Open Source Ecology - Germany - Benutzerbeiträge [de]

Wind Logging System for Sourcing ENergy – WiLSSEN

2018-03-02T16:12:52Z

Shure:

==Status==

This project is not in active development. The information on this page is obsolete and outdated.

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Turbine/en

2018-03-02T15:58:13Z

Shure:

{{DISPLAYTITLE:Wind Turbine}}
[[File:Project-icon_vawt_wikithumb_h400px.png|388px]]

==Status==

This project is not in active development. The information on this page is obsolete and outdated.

==Introduction==

All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

[[File:Etemu.com_TiVA_l2_front_wip.jpg|320px|thumb|left|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the performance on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
===Development of ''[[Wilssen]]''===
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters. ''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.

===Others===

* Design a mold for casting the alternator's stator
* 3D Models and Simulation
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.
There are various restrictions in Germany present which depend on the size and location of a wind turbine:
<blockquote>Verfahrensfrei sind Windenergieanlagen bis zu einer Höhe von 10 m<ref>Nummer 22 des Anhangs zu Paragraph 50 Abs. 1 LBO</ref>. In Mischgebieten<ref>Mischgebiet bedeutet gleichwertige Wohn- und Gewerbenutzung</ref> darf nachts ein Lärmrichtwert von 45 dB(A) nicht überschritten werden<ref>Auszug Windfibel Baden-Württemberg</ref>. Zu den Genehmigungsverfahren sei gesagt, dass die Landesbauordnung der jeweiligen Bundesländer / Kommunen unterschiedlich ist, also sollte man beim Bauamt nachfragen.</blockquote>

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT with [[TiVA]], resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter. See [https://www.youtube.com/watch?v=XthnaliaS88&t=1m2s video] and reference. <ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>https://en.wikipedia.org/wiki/Tip-speed_ratio</ref> >> 1 (TSR=Tip Speed Ratio), i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>C_d</math> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> = Area of turbine = max 4 m² 
<math>v_{wind}</math> = Wind speed in m/s

<math>F(50\frac{m}{s})=\frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</math> 
<math>F(30\frac{m}{s})=2160N</math> 
<math>F(20\frac{m}{s})=960N</math> 
<math>F(10\frac{m}{s})=240N</math> 
<math>F(5\frac{m}{s})=60N</math> 

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <math>F(30\frac{m}{s})=2160N</math>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math> = Area of turbine = max 4 m² at a small scale turbine 
<math>v_{wind}</math> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>
while 
<math>
\rho_{simple} = 20\% \\
\rho_{decent} = 30\% \\
\rho_{good} = 35\% \\
\rho_{superbVAWT} = 40\% \\
\rho_{superbHAWT} = 50\% \\
\rho_{limit} = 59\% \\
</math> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]
[[Category: Energie]]
[[Category: Wind]]
[[Category: Turbine]]

Wind Turbine/en

2018-03-02T15:57:08Z

Shure:

{{DISPLAYTITLE:Wind Turbine}}
[[File:Project-icon_vawt_wikithumb_h400px.png|388px]]

==Status==

This project is not in active development. The information on this page is obsolete and outdated.

==Introduction==

All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

[[File:Etemu.com_TiVA_l2_front_wip.jpg|320px|thumb|left|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the performance on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]].]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|working on the schematics and PCB layouts for [[Wilssen]], the controller.]]

===Development of ''[[Wilssen]]''===
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters. ''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.

===Others===

* Design a mold for casting the alternator's stator
* 3D Models and Simulation
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.
There are various restrictions in Germany present which depend on the size and location of a wind turbine:
<blockquote>Verfahrensfrei sind Windenergieanlagen bis zu einer Höhe von 10 m<ref>Nummer 22 des Anhangs zu Paragraph 50 Abs. 1 LBO</ref>. In Mischgebieten<ref>Mischgebiet bedeutet gleichwertige Wohn- und Gewerbenutzung</ref> darf nachts ein Lärmrichtwert von 45 dB(A) nicht überschritten werden<ref>Auszug Windfibel Baden-Württemberg</ref>. Zu den Genehmigungsverfahren sei gesagt, dass die Landesbauordnung der jeweiligen Bundesländer / Kommunen unterschiedlich ist, also sollte man beim Bauamt nachfragen.</blockquote>

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT with [[TiVA]], resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter. See [https://www.youtube.com/watch?v=XthnaliaS88&t=1m2s video] and reference. <ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>https://en.wikipedia.org/wiki/Tip-speed_ratio</ref> >> 1 (TSR=Tip Speed Ratio), i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>C_d</math> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> = Area of turbine = max 4 m² 
<math>v_{wind}</math> = Wind speed in m/s

<math>F(50\frac{m}{s})=\frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</math> 
<math>F(30\frac{m}{s})=2160N</math> 
<math>F(20\frac{m}{s})=960N</math> 
<math>F(10\frac{m}{s})=240N</math> 
<math>F(5\frac{m}{s})=60N</math> 

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <math>F(30\frac{m}{s})=2160N</math>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math> = Area of turbine = max 4 m² at a small scale turbine 
<math>v_{wind}</math> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>
while 
<math>
\rho_{simple} = 20\% \\
\rho_{decent} = 30\% \\
\rho_{good} = 35\% \\
\rho_{superbVAWT} = 40\% \\
\rho_{superbHAWT} = 50\% \\
\rho_{limit} = 59\% \\
</math> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]
[[Category: Energie]]
[[Category: Wind]]
[[Category: Turbine]]

Datei:20111228LXM8731 UZURI NOA -2 facebook3.jpg

2016-02-09T02:17:32Z

Shure: Shure uploaded a new version of Datei:20111228LXM8731 UZURI NOA -2 facebook3.jpg

[[Alex Shure]] at work at the horizontal band saw.

Datei:Alex Shure.jpg

2016-02-09T02:16:42Z

Shure: Shure uploaded a new version of Datei:Alex Shure.jpg

Benutzer:Shure

2016-02-09T02:06:08Z

Shure:

{{InternalWikiCommunication|Alex_Shure}}
(deprecated)

[[Category:Mitgliederliste‏‎]]

Benutzer:Shure

2016-02-09T02:05:59Z

Shure: Der Seiteninhalt wurde durch einen anderen Text ersetzt: „{{InternalWikiCommunication|Alex_Shure}} Alex Shure (deprecated) Category:Mitgliederliste‏‎“

{{InternalWikiCommunication|Alex_Shure}}
[[Image:Alex_Shure.jpg|thumb|Alex Shure]]
(deprecated)

[[Category:Mitgliederliste‏‎]]

Wind Logging System for Sourcing ENergy – WiLSSEN

2014-03-12T10:54:57Z

Shure: /* Development */

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
During collaborative sessions: '''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Tiny Vertical Axis Wind Turbine (TiVA)

2014-03-12T10:47:38Z

Shure: m

==Introduction==
The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a wind energy harvesting and testing platform for anybody. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines. [[TiVA]] is also a prototyping platform for educational purposes: Students, teachers, hackers and anybody with interest in the topic can learn and tinker with renewable energy harvesting in a small scale.

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

TODO: post a list with all the parts needed for one TiVA.

Still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===YOU===
Is there anything you can supply or contribute? Please get in touch with [[Alex Shure|Alex]] or make a post in our Forum. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32m x 0.32m drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s?) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]].

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Open Source Ecology Germany

2014-03-12T10:42:40Z

Shure: After talking with the project owner: Filapuller is not (yet?) Open Source, thus removed it. Also has no content and is not maintained in this wiki.

{{DISPLAYTITLE:}}
<html>
<table class="table10col" style="text-align:center; width:100%; border:2px solid white; border-radius:20px;">
<tr>
<td colspan="10" align="left"><h2 style="border-bottom:1px solid grey;"> Die Projekte</h2></td>
</tr>
<tr style="background:#F0EEB7; font-size:0.7em;">
<td class="release"></html>[[File:Unipro_icon2.png|50px|link=Universal Prototyping Kit]]<html> </html>[[Universal Prototyping Kit|Baukasten]]<html></td>
<td class="prototype"></html>[[File:Icon5c.png|50px|link=Zn/O-Brennstoffzelle]]<html> </html>[[Zn/O-Brennstoffzelle]]<html></td>
<td class="testing"></html>[[File:Tiva-wind-turbine-transparent-50pxh.png|link=Wind_Turbine]]<html> </html>[[Wind_Turbine|Windturbine]]<html></td>
<td class="documentation"></html>[[File:Plastic_shredder_50pxh.png|link=Filamaker]]<html> </html>[[Filamaker]]<html></td>
<td class="rd inactive"></html>[[File:Induction-furnace_50pxh.png|link=Induktionsofen]]<html> </html>[[Induktionsofen]]<html></td>
<td class="testing inactive"></html>[[File:Tlud-stove_50pxh.png|link=Holzvergaserofen]]<html> </html>[[Holzvergaserofen|Holzvergaserofen]]<html></td>
<td class="prototype"></html>[[File:MC_Step_Motor.png|50px|link=CNC_Circuit_Mill]]<html> </html>[[CNC_Circuit_Mill|CNC Platinenfräsen Elektronik]]<html></td>
<td class="rd inactive"></html>[[File:Hoflader.png|50px|link=Hoflader]]<html> </html>[[Hoflader]]<html></td>
<td class="documentation inactive"></html>[[File:Rollhacke.png|50px|link=Rollhacke]]<html> </html>[[Rollhacke]]<html></td>
<td class=""></td>
</tr>
<tr style="background:#F0EEB7; font-size:0.7em;">
<td class="testing"></html>[[File:Wilssen_icon.png|50px|link=Wireless Wind Logging System]]<html> </html>[[Wilssen| Wireless Wind Logging System]]<html></td>
<td class="rd"></html>[[File:Icon5c.png|50px|link=Microbial_fuel_cell]]<html> </html>[[Microbial_fuel_cell| Mikrobielle Brennstoffzelle]]<html></td>
<td class="documentation"></html>[[File:DiVER.png|50px|link=DiVER]]<html> </html>[[DiVER]]<html></td>

<td class="prototype"></html>[[File:HOG3D PlaDruMas.png|50px|link=HOG3D_PlaDruMas_-_Platinen-_und_Druck-Maschine]]<html> </html>[[HOG3D_PlaDruMas_-_Platinen-_und_Druck-Maschine|Platinen- 3D-Drucker Kombi]]<html></td>
<td class="inactive"> </html>[[Hofladen]]<html></td>
<td class="prototype"></html>[[File:Milking_robot.png|50px|link=Milking_robot]]<html> </html>[[Milking_robot| Mobiler Melkroboter]]<html></td>
<td class="research inactive"></html>[[File:Archimedes_screw_credit_Britannica.png|50px| link=EDUWAMA_Energie_DUrch_WAsserMAssen]]<html> </html>[[EDUWAMA_Energie_DUrch_WAsserMAssen| Hoch-Durchsatz-Wasserkraftwerk]]<html></td>
<td class="prototype"></html>[[File:EDUWAFA.png|50px| link=EDUWAFA_Energie_DUrch_WAsserFAll]]<html> </html>[[EDUWAFA_Energie_DUrch_WAsserFAll| Hoch-Druck-Wasserkraftwerk]]<html></td>

<td class=""></td>
</tr>
<tr><th colspan="10" style="text-align:left;">Legende:</th></tr>
<tr>
<td class="inactive">Projekt inaktiv! <a href="Open_Source_Ecology_Germany/Profil">Entwickler gesucht!</a></td><td class="research">R & D Forschung & Entwicklung</td><td class="prototyping">Prototyp</td><td class="documentation">Dokumentation</td><td class="testing">Testphase</td><td class="release">Released</td><td colspan="4"></td>
</tr>

<tr><td colspan="10" align="left"><h2 style="border-bottom:1px solid grey;"> Open Source Ecology Germany</h2></td></tr>

<tr style="border:1px solid grey;">
<td colspan="2"><a href="/OSEG_Organisation"><img src="./images/icons/book.png"></a></td><td colspan="2"><a href="/Open_Source_Ecology_Germany/Werte"><img src="./images/icons/green_button.png"></a></td><td colspan="2"><a href="/Open_Source_Ecology_Germany/Open_Source_Economy"><img src="./images/icons/globe_process.png"></a></td><td colspan="2"><a href="/Open_Source_Ecology_Germany/Netzwerk"><img width=60 height=60 src="./images/icons/network.png"></a></td><td colspan="2"><a href="/Open_Source_Ecology_Germany/Freunde"><img src="./images/icons/users.png"></a></td>
</tr>
<tr style="background:#EFF9E2; height:50px;">
<td colspan="2"></html>[[OSEG_Organisation|OSEG Live]]<html></td><td colspan="2"></html>[[Open_Source_Ecology_Germany/Werte|Werte]]<html></td><td colspan="2"></html>[[Open_Source_Ecology_Germany/Open_Source_Economy|Open Source Economy]]<html></td><td colspan="2"></html>[[Open_Source_Ecology_Germany/Netzwerk|Netzwerk]]<html></td><td colspan="2"></html>[[Open_Source_Ecology_Germany/Freunde|Freunde]]<html></td></tr>
<tr><td colspan="10" height="50px" style="border:1px solid lightgrey; border-left:0px; border-right:0px;"><div style="font-size: 145%; line-height: 25px;"> Die Open Source Ecology (OSE) Germany ist eine offene Bewegung, die eine Open Source Ökonomie aufbaut, welche sowohl Produktion als auch Verteilung optimiert, und dabei Regeneration der Umwelt und soziale Gerechtigkeit fördert. <div style="font-size: small; line-height: 150%;">Wir entwickeln die '''Technologien''' zum Aufbau einer lokalen Ökonomie, von Traktoren über Windkraftwerke bis hin zu Autos, verbessern diese kontinuierlich gemäß </html>[[Open_Source_Ecology_Germany/Werte|'''nachhaltigen Grundwerten''']]<html> wie Reproduzierbarkeit, Modularität, Eignung für den Eigenbau sowie ökologischem Design, und stellen die Ergebnisse jedem Open Source zur Verfügung. </div></div></td>
</tr>

<tr><td colspan="10" style="border:1em dotted white; border-left:0px; border-right:0px; background:lightgrey;">
<div id="osegtv" style="width:100%;">
</html>{{Videoset}}<html>
</div>
</td></tr>

<tr><td colspan="10" height="50px" style="border:1px solid lightgrey; border-left:0px; border-right:0px;"></td></tr>

<tr>
<td colspan="2">
</html>[[File:Facebook_logo.png|link=https://www.facebook.com/OSEGermany]] [[File:Twitter_logo.png|link=http://twitter.com/OSEGermany]] [[File:Youtube_logo.png|link=https://www.youtube.com/user/osegermany]]<html>
</td>
<td colspan="2"><a href="/Open_Source_Ecology_Germany/Profil"><img src="./images/icons/add_user.png"></a></td>
<td colspan="4"><a href="/Open_Source_Ecology_Germany/Spenden"><img src="./images/icons/euro_coin.png"></a> <a href="/Open_Source_Ecology_Germany/Spenden/Bitcoinspenden"><img src="./images/icons/bitcoin.svg"></a></td>
<td colspan="2"><a href="/Open_Source_Ecology_Germany/Unterstützen"><img src="./images/icons/add_to_favorites.png"></a></td>
</tr><tr style="background:#EFF9E2; height:50px;">
<td colspan="2">Externe Netzwerke</td>
<td colspan="2"></html>[[Open_Source_Ecology_Germany/Profil|Beitreten und eigenes Profil erstellen]]<html></td>
<td colspan="4"></html>[[Open_Source_Ecology_Germany/Spenden|Spenden]]<html></td>
<td colspan="2"></html>[[Open_Source_Ecology_Germany/Unterstützen|Unterstützen]]<html></td>
</tr>

<tr><td colspan="10" height="50px" style="border:1px solid lightgrey; border-left:0px; border-right:0px;"> </td></tr>

<tr><td colspan="5" align="left"><h2 style="border-bottom:1px solid grey;"> Kontakt</h2></td><td colspan="5" align="right"><h2 style="border-bottom:1px solid grey;">Hilfe </h2></td></tr><tr><td><a href="/Open_Source_Ecology_Germany/OSEG_Kommunikation"><img src="./images/icons/megaphone.png"></a></td><td><a href="/Open_Source_Ecology_Germany/Events"><img src="./images/icons/event.png"></a></td><td><a href="http://forum.opensourceecology.de"><img src="./images/icons/users_comments.png"></a></td>
<td><a href="http://opensourceecology.de"><img src="./images/icons/promotion.png"></a></td>
<td><a href="/Open_Source_Ecology_Germany/Kontakt"><img src="./images/icons/mail.png"></a></td><td colspan="3"></td><td><a href="/Software"><img src="./images/icons/tools.png"></a></td><td><a href="/Fragen_und_Antworten"><img src="./images/icons/help.png"></a></td></tr><tr style="background:#EFF9E2; font-size:0.7em;"><td></html>[[Open_Source_Ecology_Germany/OSEG_Kommunikation|Kommunikation]]<html></td><td></html>[[Open_Source_Ecology_Germany/Events|Events]]<html></td><td></html>[http://forum.opensourceecology.de Forum]<html></td>
<td></html>[http://opensourceecology.de Blog]<html></td>
<td></html>[[Open_Source_Ecology_Germany/Kontakt|Kontakt]]<html></td><td colspan="3"></td><td></html>[[Software]]<html></td><td></html>[[Fragen_und_Antworten|FAQ]]<html></td></tr><tr><td colspan="10" height="5px" style="border:1px solid lightgrey; border-left:0px; border-right:0px; border-bottom:0px;"> </td></tr></table>
</html>[[Umstrukturierung|Momentan findet eine Umstrukturierung statt, für weitere Informationen klicke hier!]]<html>


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AgroCircle

2014-03-02T20:36:49Z

Shure: m typo

Alias "Agrokruh"

==Übersicht==
Universeller Agrar - Roboter für den Bio-Gemüseanbau, aufbauend auf dem Rundfeldprinzip

==Materialsammlung==
Erfinder: Ján Šlinský
* Talk TEDx Bratislava (mit englischen Untertiteln) http://www.youtube.com/watch?v=ZwP3A6z4sFc

Doku aus der Slovakei:
* http://www.youtube.com/watch?v=mYrJ0BJ4Qak

Linksammlung
* Ján Šlinský's CSA AgroKruh http://www.google.de/maps/@48.1699222,17.3968533,339m/data=!3m1!1e3
* http://ec.europa.eu/environment/ecoap/about-eco-innovation/good-practices/slovakia/20140127-organic-farming-goes-in-circles_de.htm
* http://www.farmlandia.sk/en/agrokruh/
* http://www.agrokruh.sk/
* http://www.fairtrade.cz/files/texty/spolupracujeme/cepta-introducing-agrokruh.pdf
* http://www.osrliving.org/forum/forum_posts.asp?TID=44]

==Komponenten==

===Port===
http://www.youtube.com/watch?v=IMbGA-nOW64#t=53

'''Funktion:''' Befestigte Installation für Lageraufnahme, 400V, Wasser, (optional Netzwerk)
*unverrückbar durch Eigengewicht oder Verankerung

===Drehlager===
'''Funktion:''' Auflager für Traverse, Drehverteiler für Strom und Wasser, (optional Netzwerkanschluß (Wlan)), Synchronisation der Verschiebung

'''Realisation:'''
http://www.youtube.com/watch?v=IMbGA-nOW64#t=5m35

* Inkremental-Drehgeber (nich benötigt)
* Schleifkontakte
**5-polig für L1-3,N,PE
**fertig kaufen oder Eigenbau
**Eigenbau aus Ringen aus CU-Rohr, Motorkohlen, Kunststoffträgern (ggf. 3D-Druck)
**16A Belastbarkeit
* Zahnrad für umlaufende Kette des Radialantriebs

===Traverse===
'''Funktion:''' Lager für Geräteträger, Personenträger, nimmt Drehmomente und Kräfte auf
'''Realisation:'''
*3seitig
*ggf. mit Stützrad
*aus Veranstaltungsbau (Al oder St)
*Kranmast, Gitterrohrmast
*einfacher Eigenbau

===Tangentialantrieb (Hauptantrieb)===
'''Funktion:''' Kreisbewegung, Antrieb für Geräte
'''Realisation:'''

*http://www.youtube.com/watch?v=Von3EgRGutw#t=1m35
*http://www.youtube.com/watch?v=Von3EgRGutw#t=2m01

*Drehstrom-Getriebemotor mit FU
*ggf. ohne Getriebe nur mit FU? - Ich glaube das ist nicht möglich. --[[User:Shure|Shure]] ([[User talk:Shure|talk]]) 21:35, 2 March 2014 (CET)
*Ein Rad mit Stützrädern oder 2 Räder

===Radialantrieb (steuert Spirale)===
Ján Šlinský hat dafür ein einfache Lösung gefunden, die komplett ohne Elektronik auskommt: Es gibt eine Umlaufende Kette, die sich um ein Zahnrad am Zentralmast wickelt.
Der Umfang dieses Zahnrades bestimmt die Spurweite der Spirale.

===Geräteträger===
*http://www.youtube.com/watch?v=IMbGA-nOW64#t=4m30
*http://www.youtube.com/watch?v=IMbGA-nOW64#t=6m55

*selbsthemmende Übersetzung + Schrittmotor
*Ketten- oder Seilantrieb mit Rückkopplung vom Drehgeber, um Schlupf vom Hauptantrieb zu kompensieren
*Positionserkennung via Markern auf Traverse (induktiv, rfid, optisch) oder Entfernungsmessung
*Eilgang zum zurückfahren
*Steckdose für angetriebene Geräte, oder angetriebene Zapfwelle/Riemenscheibe
*Schleppkette für Strom, Wasser, Daten
*Gleitlagerung oder Formrollen
*Standardisierte WZ-Schnittstelle (z.B. von Einachstraktoren)
*Magnetventil für Wasser

===Werkzeuge===
*modifizierte Handwerkzeuge
*Geräte von Einachstraktoren
*Eigenbauten

====Spatenschreiter ;-)====

====Saatvorbereiter =====
*http://www.youtube.com/watch?v=Von3EgRGutw#t=1m35
*http://www.youtube.com/watch?v=Von3EgRGutw#t=3m55

===Elektronik (optional)===
Elektronik wird in der einfachsten Realisationsstufe nicht benötigt.

Für vermehrter Automatisierung (automatische Bewässerung, etc) jedoch wünschenswert

*Arduino o. Raspberry Pi
*Frequenzumrichter (FU)
*ggf, Wlan

==ToDos==
*Kontaktaufnahme zum Erfinder, Pläne nachfragen, Besuch abstatten
*Günstige Bezugsquellen recherchieren
*Geld besorgen
*Komponenten/Material beschaffen
*Eigenbauteile konstruieren
*Bauen, Programmieren und Testen
*Erfahrungen und Pläne teilen

==Mitwirkende==
*[http://wiki.opensourceecology.de/user:ganafets82 Stefan Raabe]
*[http://www.coforum.de/?121 Thomas Kalka]
*[http://wiki.opensourceecology.de/User:FranzN Franz Nahrada]

==Sammlung==

===Ján Šlinský===
An ecological farmer. He has a diploma from the Mendel University in Brno, Faculty of Gardening. Jan Šlinský is the author of the agricultural system Agrokruh, whose main idea is to produce vegetables sustainably and ecologically. He has also built a net of local buyers, thus supporting local trade in his area.
Jan Šlinský is a practical and witty person with a well-developed common sense.

"”Enough talk, it's time to act. It is not in the power of an individual to save the entire planet. However, each of us can help a particular place on Earth. But he must be sufficiently educated and skilled, and he has to love the place he is aiding. “

http://www.agrokruh.sk/kontakt
tel.: 0918 655 564

Dozent am Sokratov-Institut

http://www.sokratovinstitut.sk/index.php/en/lektori/lektori#slinsky

Talk an TEDx Bratislava mit englischen Untertiteln: http://www.youtube.com/watch?v=ZwP3A6z4sFc

HD-Video: http://www.youtube.com/watch?v=2P7MGNLz5xE

[[Category:Landwirtschaft]]
[[Category:Bodenfruchtbarkeit]]
[[Category:Boden]]
[[Category:OSEG_Projekte]]

AgroCircle

2014-03-02T20:35:10Z

Shure: /* Tangentialantrieb (Hauptantrieb) */

Alias "Agrokruh"

==Übersicht==
Universeller Agrar - Roboter für den Bio-Gemüseanbau, aufbauend auf dem Rundfeldprinzip

==Materialsammlung==
Erfinder: Ján Šlinský
* Talk TEDx Bratislava (mit englischen Untertiteln) http://www.youtube.com/watch?v=ZwP3A6z4sFc

Doku aus der Slovakei:
* http://www.youtube.com/watch?v=mYrJ0BJ4Qak

Linksammlung
* Ján Šlinský's CSA AgroKruh http://www.google.de/maps/@48.1699222,17.3968533,339m/data=!3m1!1e3
* http://ec.europa.eu/environment/ecoap/about-eco-innovation/good-practices/slovakia/20140127-organic-farming-goes-in-circles_de.htm
* http://www.farmlandia.sk/en/agrokruh/
* http://www.agrokruh.sk/
* http://www.fairtrade.cz/files/texty/spolupracujeme/cepta-introducing-agrokruh.pdf
* http://www.osrliving.org/forum/forum_posts.asp?TID=44]

==Komponenten==

===Port===
http://www.youtube.com/watch?v=IMbGA-nOW64#t=53

'''Funktion:''' Befestigte Installation für Lageraufnahme, 400V, Wasser, (optional Netzwerk)
*unverrückbar durch Eigengewicht oder Verankerung

===Drehlager===
'''Funktion:''' Auflager für Traverse, Drehverteiler für Strom und Wasser, (optional Netzwerkanschluß (Wlan)), Synchronisation der Verschiebung

'''Realisation:'''
http://www.youtube.com/watch?v=IMbGA-nOW64#t=5m35

* Inkremental-Drehgeber (nich benötigt)
* Schleifkontakte
**5-polig für L1-3,N,PE
**fertig kaufen oder Eigenbau
**Eigenbau aus Ringen aus CU-Rohr, Motorkohlen, Kunststoffträgern (ggf. 3D-Druck)
**16A Belastbarkeit
* Zahnrad für umlaufende Kette des Radialantriebs

===Traverse===
'''Funktion:''' Lager für Geräteträger, Personenträger, nimmt Drehmomente und Kräfte auf
'''Realisation:'''
*3seitig
*ggf. mit Stützrad
*aus Veranstaltungsbau (Al oder St)
*Kranmast, Gitterrohrmast
*einfacher Eigenbau

===Tangentialantrieb (Hauptantrieb)===
'''Funktion:''' Kreisbewegung, Antrieb für Geräte
'''Realisation:'''

*http://www.youtube.com/watch?v=Von3EgRGutw#t=1m35
*http://www.youtube.com/watch?v=Von3EgRGutw#t=2m01

*Drehstrom-Getriebemotor mit FU
*ggf. ohne Getriebe nur mit FU? - Ich glaube das ist nicht möglich. --[[User:Shure|Shure]] ([[User talk:Shure|talk]]) 21:35, 2 March 2014 (CET)
*Ein Rad mit Stützrädern oder 2 Räder

===Radialantrieb (steuert Spirale)===
Ján Šlinský hat dafür ein einfache Lösung gefunden, die komplett ohne Elektronik auskommt: Es gibt eine Umlaufende Kette, die sich um ein Zahnrad am Zentralmast wickelt.
Der Umfang dieses Zahnrades bestimmt die Spurweite der Spirale.

===Geräteträger===
*http://www.youtube.com/watch?v=IMbGA-nOW64#t=4m30
*http://www.youtube.com/watch?v=IMbGA-nOW64#t=6m55

*selbsthemmende Übersetzung + Schrittmotor
*Ketten- oder Seilantrieb mit Rückkopplung vom Drehgeber, um Schlupf vom Hauptantrieb zu kompensieren
*Positionserkennung via Markern auf Traverse (induktiv, rfid, optisch) oder Entfernungsmessung
*Eilgang zum zurückfahren
*Steckdose für angetriebene Geräte, oder angetriebene Zapfwelle/Riemenscheibe
*Schleppkette für Strom, Wasser, Daten
*Gleitlagerung oder Formrollen
*Standardisierte WZ-Schnittstelle (z.B. von Einachstraktoren)
*Magnetventil für Wasser

===Werkzeuge===
*modifizierte Handwerkzeuge
*Geräte von Einachstraktoren
*Eigenbauten

====Spatenschreiter ;-)====

====Saatvorbereiter =====
*http://www.youtube.com/watch?v=Von3EgRGutw#t=1m35
*http://www.youtube.com/watch?v=Von3EgRGutw#t=3m55

===Elektronik (optional)===
Elektronik wird in der einfachsten Realisationsstufe nicht benötigt.

Für vermehrter Automatisation (automatische Bewässerung, etc) jedoch wünschenswert

*Arduino o. Raspberry Pi
*Frequenzumrichter (FU)
*ggf, Wlan

==ToDos==
*Kontaktaufnahme zum Erfinder, Pläne nachfragen, Besuch abstatten
*Günstige Bezugsquellen recherchieren
*Geld besorgen
*Komponenten/Material beschaffen
*Eigenbauteile konstruieren
*Bauen, Programmieren und Testen
*Erfahrungen und Pläne teilen

==Mitwirkende==
*[http://wiki.opensourceecology.de/user:ganafets82 Stefan Raabe]
*[http://www.coforum.de/?121 Thomas Kalka]
*[http://wiki.opensourceecology.de/User:FranzN Franz Nahrada]

==Sammlung==

===Ján Šlinský===
An ecological farmer. He has a diploma from the Mendel University in Brno, Faculty of Gardening. Jan Šlinský is the author of the agricultural system Agrokruh, whose main idea is to produce vegetables sustainably and ecologically. He has also built a net of local buyers, thus supporting local trade in his area.
Jan Šlinský is a practical and witty person with a well-developed common sense.

"”Enough talk, it's time to act. It is not in the power of an individual to save the entire planet. However, each of us can help a particular place on Earth. But he must be sufficiently educated and skilled, and he has to love the place he is aiding. “

http://www.agrokruh.sk/kontakt
tel.: 0918 655 564

Dozent am Sokratov-Institut

http://www.sokratovinstitut.sk/index.php/en/lektori/lektori#slinsky

Talk an TEDx Bratislava mit englischen Untertiteln: http://www.youtube.com/watch?v=ZwP3A6z4sFc

HD-Video: http://www.youtube.com/watch?v=2P7MGNLz5xE

[[Category:Landwirtschaft]]
[[Category:Bodenfruchtbarkeit]]
[[Category:Boden]]
[[Category:OSEG_Projekte]]

OSHW Websites

2013-12-20T00:56:59Z

Shure:

Collection of OSHW Links:

* http://makingsociety.com/
* http://etemu.com/

==Germany==
* http://dokuwiki.bauraum-lowtech.org/

Benutzer:Shure

2013-12-06T11:48:12Z

Shure: /* WHO are you? */

{{InternalWikiCommunication|Alex_Shure}}
[[Image:Alex_Shure.jpg|thumb|Alex Shure]]

==Team Culturing Information==

==='''WHO''' are you?===
*''Name'' - Alex Shure
*''Location (country)'' - Germany
*''Contact Information (email, phone)'' - as at etemu.com, PGP: 0x3DF914EB, mobile: +49 151 five two seven 16901
*''Introduction Video'' -
*''Resume/CV'' - technologist, inventor: electronics, prototyping, research and development.

==='''WHY''' are you motivated to support/develop this work?===
*''Do you support open source culture?''
''This question is pretty obsolete for any profile on this wiki.''

*''Why are you interested in collaborating with us?''
I like to create/craft/tinker.

*''What should happen so that you become more involved with OSE Europe?''
Let's wait for some time to pass, [[OSE_Europe/Germany|OSE Community in Germany]] is too virgin right now.
However, successful fundraising and a lab/workshop village/place full of interesting people, ideas and machines in Germany seem attractive to me.

*''What is missing in OSE Europe?''
- New inventions. We shouldn't focus on the [[GVCS]].

- An efficient electronic infrastructure, preferably low voltage DC.

- Also, the [[GVCS]] lacks some quite important everyday machines. For the average household, there are definitely some appliances missing: Washing machine, dish washer, cooking range/small oven, most importantly a refrigerator!

- Tools: Router, table saw, vacuum cleaner, chainsaw, ...

*''What are your suggestions for improvement in OSE Europe?''
(tbd)

==='''WHAT''' are your skills?===

*''List all of your skills in these areas, at what level (beginner, intermediate, advanced) and where did you practice them:''
**Humor - advanced, post-human-level. dark and filthy.
**Natural Building - earthship design basics, geodesic structures, sub-terra-cooling
**Woodworking - intermediate. I worked as a carpenter some time ago. I built an acoustic guitar. And I carved a spoon once.
**Electronics - advanced. I prefer SMD over THT, AVR over MSP, SSRs over electromechanical relays, brushless over brushed motors. My DSO has 4 channels + FFT.
**Automation - intermediate. The light in my bathroom is automatically switched with a pyroelectric sensor. I sip tea in the kitchen while watching the ''Linux'' controlled CNC milling machine work in the basement via VNC ''on my smartphone''. My lathe is digitally controlled with a VFD.
**CAD Design - intermediate beginner, SketchUp expert, new to Inventor. Did some FEA, have not yet gotten into CFD.
**Energy - advanced -> power sources, renewable energy, efficiency calculations, grid layout, power consumption, rectifying techniques, power supplies, inverters, off-grid-systems,...
**CNC - advanced -> construction, maintenance of stepping motor and servo driven machines, retrofitting lathes and milling machines with modern hardware, LinuxCNC (formerly EMC2, the enhanced machine controller)
**Product Design - advanced <-> working at etemu.com prototyping.
**Sports -> downhill mountain biking, snowboarding, squash, climbing, pillow fights

Jack of all technical trades, a master of none.

*''How have you already contributed to OSE, OSE Europe and Open Source Hardware?''
I include the OSHW logo in any of my open source PCB and hardware designs. I try to publish everything under an Open Source license wherever possible.
I talk about it and spread the word.
I work actively on projects like the [[Wind_Turbine]], [[TiVA]], [[DiVER]], [[WiLSSEN]], ...

===HOW can you help?===

*''How do you want to contribute?''
Giving advice in engineering and bringing new inventions to life.

<references />

[[Category:Mitgliederliste‏‎]]

DiVER/en

2013-06-24T22:32:44Z

Shure: /* Introduction */

{{DISPLAYTITLE:DiVER}}

[[Open_Source_Ecology_Germany|<MainPage]]

==Introduction==

DiVER:
'''Di'''rect Current low '''V'''oltage '''E'''lectrical Grid for '''R'''enewable energies

*Any voltage over about 60VDC is not safe to the touch
*Any voltage over 60VDC needs a special license to operate in Germany, e.g. you may not build and connect a grid over 60V, unless a proper Electrician checks everything (VDE)
*Small permanent magnet alternators used in a generator at a wind turbine or a water turbine usually operate at below 100V
*It is very expensive to generate a true sine wave alternating current out of low voltage DC from the renewable energies
*Solar panels output low voltage DC
*TEG (thermo electric generators) output low voltage DC

Only a few systems really do need the high voltage AC of 230V or 110V.

*Desktop Computers (although terribly inefficient compared to laptops and smartphones) do need 12 VDC, 5 VDC and 3,3 VDC.
*Laptops need about 12-20 VDC
*TFT Flatscreens run on DC, especially if they have an LED backlight.
*Mobile phones, smartphones, tablet PCs etc are all charged and run with 5VDC

Difficulties and negative points about a low voltage DC grid:

*Grid size is smaller with a lower voltage or:
*available Power is lower at the same AWG / cable dimensions
*special connectors have to be chosen

A hybrid 230 VAC + DiVER infrastructure for OSEG/FeFG: 230VAC for high power appliances like some machines, DiVER for any consumer electronics (wherever possible) and efficient lighting.

Household circuit breakers may be re-used for a DiVER grid, e.g. anything from 8-63A per phase.

System voltage:

*N: 0V, GND
*L1: 12VDC, 10-15VDC (one lead acid battery)
*L2: 24VDC, or higher, to be determined. e.g. 24-48VDC (three lead acid batteries)

A cheap NYM-J 2x2.5mm² (1 Phase) or 4x2.5mm² (2 Phase) cabling may be used for low power branches of the grid.

E.g. for L2 with nominal voltage 3x12V = 36V: equals three lead acid batteries connected in series. If fully charged, grid voltage at the source would be 3*14V = 42V, at empty batteries about 32V.

The L2 grid voltage (only the voltage!) may be compatible with PoE, Power over Ethernet 802.3af (802.3at Type 1) and 802.3at Type 2, if the grid voltage is above 40 V.

At 36V and 63A, there are 2268W available in the grid, if we assume proper cables and connectors. It depends on the application, but I would have switched over to 230 VAC already at this power rating.

One could make the 12V phase on/off grid redundant with one efficient ATX power supply+two Schottky diodes or with active switching. It is much easier to switch DC synchronous vs AC synchronous, because one does not have to establish a phase lock to get the waveform in sync.

==Smart DiVER==

The start would be to equip an energy monitoring system, like DiVER.Wilssen. Communication could take place via
*Wireless connections (even to non-grid-tied appliances. NRF24L01+, RFM, xBee)
*Wired LAN connection (expensive and uses additional cabling)
*PLC (Powerline Communication) with an Open Source protocol and hardware design.

Research: What about RS485 between two phases, would that be possible? Is a choke / low-pass needed at the low impedance energy sources and appliances? What frequency is used best for transmitting data via a modulated power line? Coupling via passive RC-highpass?
There might be an integrated circuit for low voltage DC PLC communication?

==DiVER.Wilssen==
The Wireless Logging System for Sourcing ENergy - Controller is monitoring some or all grid parameters and is connected with the BMS (battery monitoring/managment system) or may even contain BMS functions. Wilssen is the brain of a DiVER grid, Wilssen is recommended but not necessary for operation.

*battery voltage of each battery (multiplexed) (2s1p, 3s1p, 3s2p, 3s4p etc)
*battery bank voltage
*l1 phase current (has got to be signed for bidirectional measurement)
*l2 phase current (has got to be signed for bidirectional measurement)

*battery bank temperature sensor (OneWire preferred)
*over current protection
*under voltage protection
*Uninterruptable Power Source function.
*SSR<ref>Solid State Relay</ref> usage, no conventional electromechanical Relays.

At a future revision, Wilssen may also:

*switch on chargers or grid-tied SMPS (switch mode power supplies) if source impedance gets to high/grid voltage too low.

optional: digital ZVD (zero voltage diode) function via comparator+ISR at ADC or interrupt attached to a plain digital port pin. SSR could then be used as OC protection, UV protection and ZVD.

SSR module may be replaced with a MOSFET at low power applications.

===Wilssen Hardware===

*Voltage sensing should be through passive voltage dividers with appropriate headroom and a high impedance connection to the ADC, we don't need the galvanic isolation at these low voltages.

*Current sensing should not be shunt based, but rather with a hall effect sensor or inductive. At DC, inductive sensing is not possible I guess, so we have to stick to hall sensors.
The integrated current sensor packages from Allegro are quite expensive. The following will be suitable for a <200A grid.
Bidirectional integrated hall effect current sensor:
ACS759 ±50A to 200A
ACS756 ±50A to 100A

*SSR example:
100V, 100A type:
http://www.mercateo.com/p/139A-1779776/SSR_100A_100V_SIP_Typ_D1D100.html?showSimplePage=NO&ViewName=live~showGrossColumn&utm_source=product-search&utm_medium=web&utm_campaign=Halbleiterrelais#crydom-ssr-100a-100v-sip-typ-d1d100-crydom

*2row LCD display for easy overview at the controller, showing the momentary power consumption and accumulated energy, grid voltage, ...

==Physical Layout: Cabling, Sockets, Fuses==

If the infrastructure is build from scratch and completely new, then it's best to start with a hybrid AC/DC<ref>Alternating Current / Direct Current, not the famous rockband</ref> DiVER grid:

cabling:
*open or closed ring topology with branches, e.g. 3p AC household EIS: 1 x NYM-J 5G2.5, laid in parallel with 1x NYM-J 4x2.5 (up to 4x10)

Important: How to determine the cables other than by their inner topology? DiVER cables should be marked differently.

===Connectors, sockets, plugs, terminals===

Suggestions for sockets and plugs for DiVER:

*large screw terminals (which is somewhat legal, because the DIVER grid is safe to the touch )
*PowerCon sockets (expensive, proprietary, e.g. by Neutrik. How many poles?)
*SpeakOn sockets (moderately expensive, well suited because they carry 4 poles and are aimed for moderately high currents)
*XLR sockets (cheap, but can't carry much current. maybe for small appliances like phone chargers)
*Open Source screw terminals with M6 screws. 3D printed or milled.

Any other recommendations?

*CEE sockets are way too expensive, overkill and not meant for DIVER voltages. They may also be confused with the mains grid.

*DiVER Fuses, circuit breakers, Wilssen, BMS, PDUs and so on are encased in a separate enclosure and are nowhere near the mains.

XLR specifications from Neutrik NC3-FX

Capacitance between contacts ≤ 4 pF
Contact resistance ≤ 3 mΩ (inner)
Dielectric strength 1,5 kVdc
Insulation resistance > 2 GΩ (initial)
Rated current per contact 16 A
Rated voltage 50 V

===Separated or safety extra-low voltage (SELV)<ref>http://en.wikipedia.org/wiki/Extra-low_voltage</ref>===

IEC defines a SELV system as "an electrical system in which the voltage cannot exceed ELV under normal conditions, and under single-fault conditions, ''including'' earth faults in other circuits".

There exists some confusion regarding the origin of the acronym: "SELV" stands for "''separated'' extra-low voltage" in installation standards (e.g., BS 7671) and for "''safety'' extra-low voltage" in appliance standards (e.g., BS EN 60335).

A SELV circuit must have:
* protective-separation (i.e., double insulation, reinforced insulation or protective screening) from all circuits other than SELV and PELV (i.e., all circuits that might carry higher voltages) As an example, in New Zealand, ELV wiring in domestic premises must be installed at a minimum distance of 50 mm from low voltage wiring or have a separate insulating barrier such as conduit.<ref>http://en.wikipedia.org/wiki/Extra-low_voltage</ref>
* simple separation from other SELV systems, from PELV systems and from earth (ground).

The safety of a SELV circuit is provided by
* the extra-low voltage
* the low risk of accidental contact with a higher voltage;
* the lack of a return path through earth (ground) that electric current could take in case of contact with a human body.

The electrical connectors of SELV circuits should be designed such that they do not mate with connectors commonly used for non-SELV circuits.

<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

DiVER/en

2013-06-24T22:20:41Z

Shure: /* Separated or safety extra-low voltage (SELV)http://en.wikipedia.org/wiki/Extra-low_voltage */

Tiny Vertical Axis Wind Turbine (TiVA)

2013-06-02T23:51:37Z

Shure: /* Introduction */

==Introduction==
The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a wind energy harvesting and testing platform for anybody. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines. [[TiVA]] is also a prototyping platform for educational purposes: Students, teachers, hackers and anybody with interest in the topic can learn and tinker with renewable energy harvesting in a small scale.

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

TODO: post a list with all the parts needed for one TiVA.

Still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===YOU===
Is there anything you can supply or contribute? Please get in touch with [[Alex Shure|Alex]] or make a post in our Forum. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]].

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Diskussion:Basis-Set Haus

2013-06-02T00:04:06Z

Shure: Created page with "Bitte die Sources (SKP?) hochladen und verlinken. Danke! --~~~~"

Bitte die Sources (SKP?) hochladen und verlinken. Danke! --[[User:Shure|Shure]] ([[User talk:Shure|talk]]) 02:04, 2 June 2013 (CEST)

DiVER/en

2013-05-28T14:45:01Z

Shure: /* Connectors, sockets, plugs, terminals */

{{DISPLAYTITLE:DiVER}}

[[Open_Source_Ecology_Germany|<MainPage]]

==Introduction==

DiVER:
'''Di'''rect Current low '''V'''oltage '''E'''lectrical Grid for '''R'''enewable energies

*Any voltage over about 60VDC is not safe to the touch
*Any voltage over 60VDC needs a special license to operate in Germany, e.g. you may not build and connect a grid over 60V, unless a proper Electrician checks everything (VDE)
*Small permanent magnet alternators used in a generator at a wind turbine or a water turbine usually operate at below 100V
*It is very expensive to generate a true sine wave alternating current out of low voltage DC from the renewable energies
*Solar panels output low voltage DC
*TEG (thermo electric generators) output low voltage DC

Only a few systems really do need the high voltage AC of 230V or 110V.

*Desktop Computers (although terribly inefficient compared to laptops and smartphones) do need 12 VDC, 5 VDC and 3,3 VDC.
*Laptops need about 12-20 VDC
*TFT Flatscreens run on DC, especially if they have an LED backlight.
*Mobile phones, smartphones, tablet PCs etc are all charged and run with 5VDC

Difficulties and negative points about a low voltage DC grid:

*Grid size is smaller with a lower voltage or:
*available Power is lower at the same AWG / cable dimensions
*special connectors have to be chosen

A hybrid 230 VAC + DiVER infrastructure for OSEG/FeFG: 230VAC for high power appliances like some machines, DiVER for any consumer electronics (wherever possible) and efficient lighting.

Household circuit breakers may be re-used for a DiVER grid, e.g. anything from 8-63A per phase.

System voltage:

*N: 0V, GND
*L1: 12VDC, 10-15VDC (one lead acid battery)
*L2: 24VDC, or higher, to be determined. e.g. 24-48VDC (three lead acid batteries)

A cheap NYM-J 2x2.5mm² (1 Phase) or 4x2.5mm² (2 Phase) cabling may be used for low power branches of the grid.

E.g. for L2 with nominal voltage 3x12V = 36V: equals three lead acid batteries connected in series. If fully charged, grid voltage at the source would be 3*14V = 42V, at empty batteries about 32V.

The L2 grid voltage (only the voltage!) may be compatible with PoE, Power over Ethernet 802.3af (802.3at Type 1) and 802.3at Type 2, if the grid voltage is above 40 V.

At 36V and 63A, there are 2268W available in the grid, if we assume proper cables and connectors. It depends on the application, but I would have switched over to 230 VAC already at this power rating.

One could make the 12V phase on/off grid redundant with one efficient ATX power supply+two Schottky diodes or with active switching. It is much easier to switch DC synchronous vs AC synchronous, because one does not have to establish a phase lock to get the waveform in sync.

==Smart DiVER==

The start would be to equip an energy monitoring system, like DiVER.Wilssen. Communication could take place via
*Wireless connections (even to non-grid-tied appliances. NRF24L01+, RFM, xBee)
*Wired LAN connection (expensive and uses additional cabling)
*PLC (Powerline Communication) with an Open Source protocol and hardware design.

Research: What about RS485 between two phases, would that be possible? Is a choke / low-pass needed at the low impedance energy sources and appliances? What frequency is used best for transmitting data via a modulated power line? Coupling via passive RC-highpass?
There might be an integrated circuit for low voltage DC PLC communication?

==DiVER.Wilssen==
The Wireless Logging System for Sourcing ENergy - Controller is monitoring some or all grid parameters and is connected with the BMS (battery monitoring/managment system) or may even contain BMS functions. Wilssen is the brain of a DiVER grid, Wilssen is recommended but not necessary for operation.

*battery voltage of each battery (multiplexed) (2s1p, 3s1p, 3s2p, 3s4p etc)
*battery bank voltage
*l1 phase current (has got to be signed for bidirectional measurement)
*l2 phase current (has got to be signed for bidirectional measurement)

*battery bank temperature sensor (OneWire preferred)
*over current protection
*under voltage protection
*Uninterruptable Power Source function.
*SSR<ref>Solid State Relay</ref> usage, no conventional electromechanical Relays.

At a future revision, Wilssen may also:

*switch on chargers or grid-tied SMPS (switch mode power supplies) if source impedance gets to high/grid voltage too low.

optional: digital ZVD (zero voltage diode) function via comparator+ISR at ADC or interrupt attached to a plain digital port pin. SSR could then be used as OC protection, UV protection and ZVD.

SSR module may be replaced with a MOSFET at low power applications.

===Wilssen Hardware===

*Voltage sensing should be through passive voltage dividers with appropriate headroom and a high impedance connection to the ADC, we don't need the galvanic isolation at these low voltages.

*Current sensing should not be shunt based, but rather with a hall effect sensor or inductive. At DC, inductive sensing is not possible I guess, so we have to stick to hall sensors.
The integrated current sensor packages from Allegro are quite expensive. The following will be suitable for a <200A grid.
Bidirectional integrated hall effect current sensor:
ACS759 ±50A to 200A
ACS756 ±50A to 100A

*SSR example:
100V, 100A type:
http://www.mercateo.com/p/139A-1779776/SSR_100A_100V_SIP_Typ_D1D100.html?showSimplePage=NO&ViewName=live~showGrossColumn&utm_source=product-search&utm_medium=web&utm_campaign=Halbleiterrelais#crydom-ssr-100a-100v-sip-typ-d1d100-crydom

*2row LCD display for easy overview at the controller, showing the momentary power consumption and accumulated energy, grid voltage, ...

==Physical Layout: Cabling, Sockets, Fuses==

If the infrastructure is build from scratch and completely new, then it's best to start with a hybrid AC/DC<ref>Alternating Current / Direct Current, not the famous rockband</ref> DiVER grid:

cabling:
*open or closed ring topology with branches, e.g. 3p AC household EIS: 1 x NYM-J 5G2.5, laid in parallel with 1x NYM-J 4x2.5 (up to 4x10)

Important: How to determine the cables other than by their inner topology? DiVER cables should be marked differently.

===Connectors, sockets, plugs, terminals===

Suggestions for sockets and plugs for DiVER:

*large screw terminals (which is somewhat legal, because the DIVER grid is safe to the touch )
*PowerCon sockets (expensive, proprietary, e.g. by Neutrik. How many poles?)
*SpeakOn sockets (moderately expensive, well suited because they carry 4 poles and are aimed for moderately high currents)
*XLR sockets (cheap, but can't carry much current. maybe for small appliances like phone chargers)
*Open Source screw terminals with M6 screws. 3D printed or milled.

Any other recommendations?

*CEE sockets are way too expensive, overkill and not meant for DIVER voltages. They may also be confused with the mains grid.

*DiVER Fuses, circuit breakers, Wilssen, BMS, PDUs and so on are encased in a separate enclosure and are nowhere near the mains.

XLR specifications from Neutrik NC3-FX

Capacitance between contacts ≤ 4 pF
Contact resistance ≤ 3 mΩ (inner)
Dielectric strength 1,5 kVdc
Insulation resistance > 2 GΩ (initial)
Rated current per contact 16 A
Rated voltage 50 V

===Separated or safety extra-low voltage (SELV)<ref>http://en.wikipedia.org/wiki/Extra-low_voltage</ref>===

IEC defines a SELV system as "an electrical system in which the voltage cannot exceed ELV under normal conditions, and under single-fault conditions, ''including'' earth faults in other circuits".

There exists some confusion regarding the origin of the acronym: "SELV" stands for "''separated'' extra-low voltage" in installation standards (e.g., BS 7671) and for "''safety'' extra-low voltage" in appliance standards (e.g., BS EN 60335).

A SELV circuit must have:
* protective-separation (i.e., double insulation, reinforced insulation or protective screening) from all circuits other than SELV and PELV (i.e., all circuits that might carry higher voltages)
* simple separation from other SELV systems, from PELV systems and from earth (ground).

The safety of a SELV circuit is provided by
* the extra-low voltage
* the low risk of accidental contact with a higher voltage;
* the lack of a return path through earth (ground) that electric current could take in case of contact with a human body.

The electrical connectors of SELV circuits should be designed such that they do not mate with connectors commonly used for non-SELV circuits.

<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Tiny Vertical Axis Wind Turbine (TiVA)

2013-05-21T15:36:31Z

Shure:

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

TODO: post a list with all the parts needed for one TiVA.

Still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===YOU===
Is there anything you can supply or contribute? Please get in touch with [[Alex Shure|Alex]] or make a post in our Forum. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]].

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Tiny Vertical Axis Wind Turbine (TiVA)

2013-05-21T00:13:38Z

Shure: /* Prototyping */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

Still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Is there anything you can supply or contribute? Please get in touch with [[Alex Shure|Alex]] or make a post in our Forum. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]].

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Turbine/en

2013-05-20T23:49:55Z

Shure: /* Size */

{{DISPLAYTITLE:Wind Turbine}}
{{Germany/en}}

[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Status==

The '''wind turbine''' is in the research phase of product development. We are focusing on the '''[[TiVA]]'''-System ('''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine) right now and developing the '''[[Wilssen]]''' controller for it.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and wind turbine specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Shure]] working on the schematics and PCB layouts for [[Wilssen]], the controller.]]
If you want to participate, just get in touch via our Forum or just hit [[Shure]] an e-mail. :)

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* [[Mario Grunau]] - 3D modelling (Autodesk Inventor, Maxon Cinema 4D)
* [[Achmed Touni]] - 3D modelling (FreeCAD, Blender3D), simulation (OpenFOAM, Ansys)
* [[Nikolay Georgiev]] - communication and organization
* [[Benjamin Rudtsch]] - [[Wilssen]], software development
* [[Leon Rische]] - [[Wilssen]], software development

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
===Development of ''[[Wilssen]]''===
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters. ''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.

See the current open '''github issues''': https://github.com/etemu/wilssen/issues?state=open

===Others===

* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

* Nov 2012 [[Alex Shure]] I stopped using the wiki as a crude archive and did not protocol everything which happened since May '12. A severe amount of time was put into other parts and projects of OSEG. All in all, we have agreed on getting a real project management suite online and use it for this and other projects of OSEG.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.
There are various restrictions in Germany present which depend on the size and location of a wind turbine:
<blockquote>Verfahrensfrei sind Windenergieanlagen bis zu einer Höhe von 10 m<ref>Nummer 22 des Anhangs zu Paragraph 50 Abs. 1 LBO</ref>. In Mischgebieten<ref>Mischgebiet bedeutet gleichwertige Wohn- und Gewerbenutzung</ref> darf nachts ein Lärmrichtwert von 45 dB(A) nicht überschritten werden<ref>Auszug Windfibel Baden-Württemberg</ref>. Zu den Genehmigungsverfahren sei gesagt, dass die Landesbauordnung der jeweiligen Bundesländer / Kommunen unterschiedlich ist, also sollte man beim Bauamt nachfragen.</blockquote>

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT with [[TiVA]], resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter. See [https://www.youtube.com/watch?v=XthnaliaS88&t=1m2s video] and reference. <ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>https://en.wikipedia.org/wiki/Tip-speed_ratio</ref> >> 1 (TSR=Tip Speed Ratio), i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>C_d</math> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> = Area of turbine = max 4 m² 
<math>v_{wind}</math> = Wind speed in m/s

<math>F(50\frac{m}{s})=\frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</math> 
<math>F(30\frac{m}{s})=2160N</math> 
<math>F(20\frac{m}{s})=960N</math> 
<math>F(10\frac{m}{s})=240N</math> 
<math>F(5\frac{m}{s})=60N</math> 

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <math>F(30\frac{m}{s})=2160N</math>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math> = Area of turbine = max 4 m² at a small scale turbine 
<math>v_{wind}</math> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>
while 
<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \linebreak
\rho_{good} = 35% \linebreak
\rho_{superbVAWT} = 40% \linebreak
\rho_{superbHAWT} = 50% \linebreak
\rho_{limit} = 59% \linebreak
</math> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Turbine/en

2013-05-09T21:35:24Z

Shure: /* Assembly height */

{{DISPLAYTITLE:Wind Turbine}}
{{Germany/en}}

[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Status==

The '''wind turbine''' is in the research phase of product development. We are focusing on the '''[[TiVA]]'''-System ('''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine) right now and developing the '''[[Wilssen]]''' controller for it.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and wind turbine specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Shure]] working on the schematics and PCB layouts for [[Wilssen]], the controller.]]
If you want to participate, just get in touch via our Forum or just hit [[Shure]] an e-mail. :)

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* [[Mario Grunau]] - 3D modelling (Autodesk Inventor, Maxon Cinema 4D)
* [[Achmed Touni]] - 3D modelling (FreeCAD, Blender3D), simulation (OpenFOAM, Ansys)
* [[Nikolay Georgiev]] - communication and organization
* [[Benjamin Rudtsch]] - [[Wilssen]], software development
* [[Leon Rische]] - [[Wilssen]], software development

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
===Development of ''[[Wilssen]]''===
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters. ''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.

See the current open '''github issues''': https://github.com/etemu/wilssen/issues?state=open

===Others===

* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

* Nov 2012 [[Alex Shure]] I stopped using the wiki as a crude archive and did not protocol everything which happened since May '12. A severe amount of time was put into other parts and projects of OSEG. All in all, we have agreed on getting a real project management suite online and use it for this and other projects of OSEG.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.
There are various restrictions in Germany present which depend on the size and location of a wind turbine:
<blockquote>Verfahrensfrei sind Windenergieanlagen bis zu einer Höhe von 10 m<ref>Nummer 22 des Anhangs zu Paragraph 50 Abs. 1 LBO</ref>. In Mischgebieten<ref>Mischgebiet bedeutet gleichwertige Wohn- und Gewerbenutzung</ref> darf nachts ein Lärmrichtwert von 45 dB(A) nicht überschritten werden<ref>Auszug Windfibel Baden-Württemberg</ref>. Zu den Genehmigungsverfahren sei gesagt, dass die Landesbauordnung der jeweiligen Bundesländer / Kommunen unterschiedlich ist, also sollte man beim Bauamt nachfragen.</blockquote>

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter. See [https://www.youtube.com/watch?v=XthnaliaS88&t=1m2s video] and reference. <ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>https://en.wikipedia.org/wiki/Tip-speed_ratio</ref> >> 1 (TSR=Tip Speed Ratio), i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>C_d</math> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> = Area of turbine = max 4 m² 
<math>v_{wind}</math> = Wind speed in m/s

<math>F(50\frac{m}{s})=\frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</math> 
<math>F(30\frac{m}{s})=2160N</math> 
<math>F(20\frac{m}{s})=960N</math> 
<math>F(10\frac{m}{s})=240N</math> 
<math>F(5\frac{m}{s})=60N</math> 

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <math>F(30\frac{m}{s})=2160N</math>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math> = Area of turbine = max 4 m² at a small scale turbine 
<math>v_{wind}</math> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>
while 
<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \linebreak
\rho_{good} = 35% \linebreak
\rho_{superbVAWT} = 40% \linebreak
\rho_{superbHAWT} = 50% \linebreak
\rho_{limit} = 59% \linebreak
</math> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Turbine/en

2013-05-09T21:32:14Z

Shure: /* Assembly height */

{{DISPLAYTITLE:Wind Turbine}}
{{Germany/en}}

[[File:Etemu.com_TiVA_l2_front_wip.jpg|720px|thumb|center|3D Model of a [[TiVA]] rotor, work in progress. Note the hollow wings, this is a hybrid lift/drag wing profile with a full load TSR<ref>Tip Speed Ratio</ref> of 0.85.]]

==Status==

The '''wind turbine''' is in the research phase of product development. We are focusing on the '''[[TiVA]]'''-System ('''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine) right now and developing the '''[[Wilssen]]''' controller for it.

==Introduction==
We are developing an open source wind turbine with an agile open collaboration.

[[TiVA]] and wind turbine specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA-NC)

==[[TiVA]]==
Research and development is currently concentrated onto [[TiVA]], a tiny wind turbine prototyping platform. With this very small turbine, we can easily change parts, try out new ideas and increase the quality of the design on a small scale in a fast and inexpensive way. Please have a look at the [[TiVA]] page for further information.

==Team==
[[File:DSC08567_edit_tiva_session.jpg|512px|thumb|right|3D modelling session for [[TiVA]] with [[Alex Shure]] and Mario.]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Shure]] working on the schematics and PCB layouts for [[Wilssen]], the controller.]]
If you want to participate, just get in touch via our Forum or just hit [[Shure]] an e-mail. :)

* [[Alex Shure]] – lead designer, research and development, modeling, prototyping
* [[Mario Grunau]] - 3D modelling (Autodesk Inventor, Maxon Cinema 4D)
* [[Achmed Touni]] - 3D modelling (FreeCAD, Blender3D), simulation (OpenFOAM, Ansys)
* [[Nikolay Georgiev]] - communication and organization
* [[Benjamin Rudtsch]] - [[Wilssen]], software development
* [[Leon Rische]] - [[Wilssen]], software development

==Open Tasks==
You can help us with ''any'' improvement on the project or with the following specific tasks:
===Development of ''[[Wilssen]]''===
The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is monitoring and controlling all parameters. ''Wilssen'' is the brain of the wind turbines (+[[TiVA]]s!) and checks all the voltages at any time the wind turbine is generating power.

See the current open '''github issues''': https://github.com/etemu/wilssen/issues?state=open

===Others===

* Design a mold for casting the alternator's stator
* 3D Models and Simulation (Achmed and Mario are working on it)
* Calculations for the forces at the bearing points and the mounting point
* LED drivers, controllable constant current sources for the high power LEDs
* (many more soon to come)

We still need the following materials for our first prototypes:

* Round sheets of metal for the alternators
* Plywood (Multiplex)
* Tools for the lathe, boring bar, inserts..
* Aluminium sheets for the wings
* Polyester or epoxy resin and hardener + filler
* Paint which can be sprayed, should be a sealing one for outdoors
* Cases for the electronics, IP66<
* Neodymium magnets, preferably 15x5mm<
* Enameled copper wire aka. magnet wire, with a diameter of 0.4 - 1.0mm
* Electric planer
* Aluminium or stainless steel tubes, e.g. 12x8mm for [[TiVA]]

Please get in touch with [[Alex Shure]] if you want to donate any material or machine which could come in handy for us.

==Roadmap / Log==

[[File:TiVA_2_1_lenz2_sim_safety_extreme.png|512px|thumb|right|Safety factor at an extreme gust of wind for a Lenz2 wing coupled to a rotor base with an aluminum arm. WIP<ref>work in progress</ref>]]

* 20120211 [[Alex Shure]] Start of "Open Agile SCRUM GVCS machine development" mailing list, [[Nikolay Georgiev]] sent an E-Mail to some OSE:E members - We begin to discuss the OSE:E project of constructing a wind turbine
* 20120222 [[Alex Shure]] First online meeting on the OSE:E project "develop a wind turbine" in mumble
* 20120311 [[Alex Shure]] I had a 6 hour meeting with a German wind turbine technician who works in QS where we discussed various aspects, advantages and disadvantages of horizontal and vertical axis wind turbines.
* 20120324 [[Alex Shure]] Had an online conference in mumble and spoke with [http://opensourceecology.org/wiki/Special:Contributions/Chrono Chrono], founder of the [[Apollo-NG]][https://apollo.open-resource.org] project. Chrono has experience in electronics, especially in integrated low power switching power supplies and mobile energy supplies. He is transforming a van into a mobile hackerspace, powered by renewable energy, totally off the grid.
* 20120325 [[Alex Shure]] Phone conference with Detlef Schmitz from the solar car team Heliodet; Detlef offered to build one small wind turbine prototype. He has contacts also with engineers and technicians form the solar car project, especially students from the FH/uni in Bochum.
* 20120326 [[Alex Shure]] Added the EVA wind turbine design. We could develop a VAWT which can be optionally equipped with the EVAwt features. The biggest disadvantage is the design issue with the top cover plate: with the EVAwt design, I can't think of an easy way to span the cables from the top for now.
* 20120327 [[Alex Shure]] [[chrono]] added a pad on Apollo for collaboration
* 20120328 [[Alex Shure]] Calculations
* 20120329 [[Alex Shure]] contacted Bernd from http://www.daswindrad.de
* 20120330 [[Alex Shure]] Added the [[TiVA]] page to the wiki and further designed the concept in the etherpad..
* 20120331 [[Alex Shure]] [[chrono]] moved the content from the pad at Apollo-NG into the dokuwiki at Apollo-NG. I split the [[TiVA]] parts and copied them to a wiki page here at [[OSE]]
* 20120404 [[Alex Shure]] Researched about copper losses in the enameled copper wire windings, let's use 0.45 - 1 mm wire.
* 20120405 [[Alex Shure]] I updated the TiVA wiki entry at OSE with a full BOM for a very first prototype, including sheet material for the negative form, painting and so on. Also got Mario on board, who has experience in 3D modeling.
* 20120406 [[Alex Shure]] Meeting with Mario, 3D modelling session in Autodesk Inventor.
* 20120407 [[Alex Shure]] Met M. Klein, CEO of Wezek GmbH (engineering, automation) and spoke about waterproof cases for the electronics.
* 20120408 [[Alex Shure]] Specification for [[TiVA]]'s alternator outlined. Diameter reduced to less than 200 mm, 1 phase alternator design is preferred due to less costs and the low power demand.
* 20120409 [[Alex Shure]] Finished the calculations of [[TiVA]]'s alternator. 16 round magnets, 16 coil segments, switchable from 8s1p up to 1s8p, calculated efficiency after rectification is above 90% for low loads.
* 20120410 [[Alex Shure]] We should stick to symmetric wing profiles if we go for a Darrieus style lift rotor, because those would be the easiest to fabricate. Researching on some NACA profiles now. Wings of the V-Rotor should incorporate a metal strip sandwiched between the two halves of the wing for the easiest and most rigid wing fixation method.
* 20120412 [[Alex Shure]] Fabricated three wings for [[TiVA]] out of solid wood (spruce)
* 20120413 [[Alex Shure]] Full day working session in the shop for [[TiVA]], made a hub, cut plywood, laminated the base, machined bearing seats on the lathe ...
* 20120414 [[Alex Shure]] Glued the cut plywood together, trimmed the edges, made another pass on the lathe after the lamination, to make sure everything is perfectly balanced.
* 20120415 [[Alex Shure]] Press-fit the bearings into the hub, tested the starting torque of the assembled hub with the bearings in place: not measurable with a 0.1 N scale -> good! Bought a stand air ventilator for testing purposes.
* 20120416 [[Alex Shure]] Ordered parts for the electronics + mechanics: Bearings (DIN 6003), Schottky diodes, M6 - M12 V2A stainless steel bolts and nuts, ...
* 20120417 [[Alex Shure]] Bought 5 kg of 0,45 mm diameter enameled copper wire (aka. magnet wire) for about 100,00 EUR. '''Does anybody have a cheap source for copper wire and magnets?
'''
* 20120422 [[Alex Shure]] Tested NACA0018 profiles at various angles: NACA0018 profiles aren't self starting at low angles. Aiming for a Lenz2 profile now.
* 20120426 [[Alex Shure]] Designed the alternator rotor assembly, sketched the model in SketchUp.
* 20120429 [[Alex Shure]] Ordered passive and active electronic parts.
* 20120507 [[Alex Shure]] Rotor assembly just got reconstructed: one less part which is turned on the lathe + implemented the alternator stacking feature.
* 20120508 [[Alex Shure]] Achmed is working on a FreeCAD model and will then make a mesh for OpenFOAM, an open source CFD software package.
* 20120510 [[Alex Shure]] Meeting with Mario, instructed him about the 3D model. We also agreed on leaving the NACA lift-only profiles for TiVA behind, as the Reynolds number is just too high for these small dimensions.
* 20120512 [[Alex Shure]] 3D modelling session with Mario, finished [[TiVA]]'s rotor base and began with the Lenz2 lift/drag hybrid wing profile.

* Nov 2012 [[Alex Shure]] I stopped using the wiki as a crude archive and did not protocol everything which happened since May '12. A severe amount of time was put into other parts and projects of OSEG. All in all, we have agreed on getting a real project management suite online and use it for this and other projects of OSEG.

==General design outlines==

The wind turbine should be loosely designed according to the [[OSE Core Values]] except points 8 and 9, which demand high performance and equal to or higher than industrial efficiency <ref>[[OSE Core Values]] points 8 and 9 demand a high performance and equal to or higher than industrial efficiency but the efficiency of a highly sophisticated industrial, FEA designed and airflow-simulated, wind tunnel tested model can't be matched by a diy design.</ref>

In addition to the [[OSE Core Values]], the wind turbine should be safe to operate, e.g. have a suitable safety factor in all structural calculations, proper isolation to prevent an electric shock.

=====Assembly height=====

The complete assembly of rotor and mast should not be higher than 10 m. If regional communities permit higher masts, the maximum height must not exceed 20 m, to avoid national and ICAO air traffic security issues and legal obligations to carry warning lights and report about their functionality.
There are various restrictions in Germany present which depend on the size and location of a wind turbine:
<blockquote>Verfahrensfrei sind nach Nummer 22 des Anhangs zu Paragraph 50 Abs. 1 LBO Windenergieanlagen bis zu einer Höhe von 10 m. In Mischgebieten (gleichwertige Wohn- und Gewerbenutzung) darf nachts ein Lärmrichtwert von 45 dB(A) nicht überschritten werden (Auszug Windfibel Baden-Württemberg). Zu den Genehmigungsverfahren sei gesagt, dass die Landesbauordnung der jeweiligen Bundesländer / Kommunen unterschiedlich
ist. </blockquote>

=====Size=====

We won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.
Hint: In every wind condition, a 1 m diameter VAWT with a height of 4 m (4m²) is more efficient than a 2 m x 2 m (4 m²) VAWT due to the higher rpm and better aerodynamic figures. Industrial VAWTs aim for a large height, not for a large diameter.

----

We want to design a rather small VAWT, resulting in the following advantages:

* + DIY! People should be able to build them! -> KISS principle
* + less moving parts
* + does not necessarily have to be elevated, can stand on the ground
* + collects wind from every direction: no need for a directional control (+less mechanics, electronics)
* + has a smaller footprint
* + easier to design
* + way more easy to build
* + does not need a variable pitch control for high wind speed/ high power designs
* + uses cheaper materials, less bearings and axles, less machining operations
* + maintenance is easier, as the generator is on the ground, no need for a lift or a breakdown of the turbine head
* + a modular design is possible in a certain range (e.g. building it higher/longer in any direction)
* + does not necessarily need moldings or 3D shapes like sophisticated VAWT turbine blades

* - lower rpm at the same rotor diameter, at the same wind surface area due to the partly reversed draft of the wings but:
* + can have a small diameter but a rather large height, thus more torque ''and'' more rpm

Main disadvantage against a horizontal axis wind turbine:

* - less power output compared to a sophisticated HAWT design if wind direction does not change often and turbulence is low

The small form factor alone yields the following advantages next to being diy-friendly:

* + easier maintenance
* + mobility, less weight
* + smaller impact on the environment/nature
* + lower system voltage and lower currents, less risky to operate
* + a smaller power rating results in a less complicated generator and inverter design
* + batteries can be charged quick&dirty with a simple charging circuit from a small wind turbine, which would not be possible with a high power wind turbine

Specialties about distributed energy sourcing with small wind turbines:

* (tbd) Multiple smaller wind turbines may have more physical weight per sourced energy (kg/kW) versus one large one.
* - requires an additional electrical infrastructure between multiple smaller wind turbines versus one large one -> more cables and balancing (electronics)
* + the grid can be laid out in such a way, that the turbines can be placed where the energy is needed the most, resulting in smaller run lengths of power cables and less power losses.
* + the small turbines can easily be moved to an area with a higher wind speed. This is interesting when it comes to structural or seasonal changes of the wind, e.g. when the trees grow leaves and form a barrier which decreases the ground wind speed or they form an alley/a tunnel which increases the wind speed, one may move the wind turbine to gain from the new environment.

Simply said, it is more flexible to use many small turbines versus one large one. If a larger energy source is required, we connect multiple wind turbines in a local grid -> distributed energy sourcing, a 'wind farm' consisting of VAWTs:

[[File:flowe.jpg|thumb|alt=A VAWT testing space|The ''Caltech Field Laboratory for Optimized Wind Energy'' where arrays of closely spaced ''vertical axis wind turbines'' were tested.]]
<blockquote>Dabiri carried out field tests in the summer of 2010 at an experimental farm known as the Field Laboratory for Optimized Wind Energy (FLOWE), which houses 24 10-meter-tall, 1.2-meter-wide VAWTs. In the field tests, which used six VAWTs, Dabiri and his colleagues measured the rotational speed and power generated by each of the turbines when placed in a number of different configurations. One turbine was kept in a fixed position for every configuration, while the others were on portable footings that allowed them to be shifted around.
They found that the aerodynamic interference between neighboring turbines was completely eliminated when all the turbines in an array were spaced four turbine diameters (roughly five meters or 16 feet) apart. In comparison, propeller-style HAWTs would need to be spaced 20 rotor diameters apart - which equates to a distance of more than one mile for the largest wind turbines currently in use - for the aerodynamic interference to be eliminated.
The six VAWTs generated from 21 to 47 watts of power per square meter of land area, while a comparably sized HAWT farm generates just two to three watts per square meter. See [https://www.youtube.com/watch?v=XthnaliaS88&t=1m2s video] and reference. <ref>http://www.gizmag.com/optimizing-wind-turbine-placement/19217/</ref></blockquote>

==How does the wind turbine generate energy?==

The energy is in the wind due to it's speed/local pressure differences. A wind turbine ''converts'' kinetic energy from the wind into mechanical energy. The VAWT yields energy as kinetic energy from the wind is absorbed by rotating wings. Wind is made up of moving air molecules which have mass - though not a lot. Any moving object with mass carries kinetic energy in an amount which is given by the equation<ref>http://www.reuk.co.uk/Calculation-of-Wind-Power.htm</ref>:

:Kinetic Energy = 0.5 x Mass x Velocity²

where the mass is measured in kg, the velocity in m/s, and the energy is given in joules.

Air has a known density (around 1.23 kg/m³ at sea level), so the mass of air hitting our wind turbine (which sweeps a known area) each second is given by the following equation:

:Mass/sec (kg/s) = Velocity (m/s) x Area (m²) x Density (kg/m³)

And therefore, the power (i.e. energy per second) in the wind hitting a wind turbine with a certain swept area is given by simply inserting the mass per second calculation into the standard kinetic energy equation given above resulting in the following vital equation:

:Power = 0.5 x Swept Area x Air Density x Velocity³

where Power is given in Watts (i.e. joules/second), the swept area in square meters, the Air density in kilograms per cubic meter, and the Velocity in meters per second.

{{Wide image-noborder|ETEMUcom_EVAwt6_iso.jpg|1280px|3=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.|4=99%|alt=A sketched 3D ISO view of a simplified VAWT wind energy diagram. Full size view recommended. Note: Pictured is a drag-only rotor, but our intention is to design a lift-rotor, as it has a higher tip speed ratio and revolves faster.}}

A lift-type VAWT generates lift at almost the full 360 degree rotation, as long as you have a TSR<ref>https://en.wikipedia.org/wiki/Tip-speed_ratio</ref> >> 1 (TSR=Tip Speed Ratio), i.e when the blades are moving faster than the wind is moving. This lift principle is why airplanes fly.
Depending on the operating speed and wind speed, the blades will actually be in stall for differing segments of the rotation, and hence not much lift, or at least a minimal amount compared to the drag, which slows the turbine down to a TSR < 1. This occurs when the angle of attack (for a static blade!) is at a certain point, let's say about 15 degrees. The following video shows aerodynamic stall, investigated on a 2D wing profile through air velocity, pressure, and turbulence intensity.

http://youtu.be/Ti5zUD08w5s

However, the dynamic stall characteristics are significantly different though, and since the angle of attack for a Darrieus turbine with lift airfoils is constantly changing, dynamic stall is much more important. For us, this is still ''rocket science'' and can't be measured. It has to be simulated with CFD/FEA and we hope to have some results about various wing types soon as Achmed from OSE Germany is working on a simulation with OpenFoam, an Open Source CFD program for Linux.

A drag type VAWT has always a TSR <1, and the blades capture energy for more or less 180 degrees, the blades fight the wind the other 180 degrees.

==EVA wind turbine==

[[File:ETEMUcom_EVAwt8_intake_top_iso.jpg|thumb|Example of an '''''EVA''' wind turbine'' design, ISO view of the top end. Note the wing at the front and the tail rudder.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt6_iso.jpg</ref>]]
The '''''E'''nhanced '''V'''ertical '''A'''xis Wind Turbine'' idea incorporates an intake manifold at the front which is always facing the direction where the strongest wind is coming from. The main disadvantage of the VAWT against a HAWT is reduced: There is no attacking wind which will work against the natural, clockwise rotation of the VAWT. This may result in an increased overall efficiency.

* + No wind is working 'against' the turbine, contrary to a standard VAWT, where half of the turbine is exposed to wind which flows into the 'wrong' direction
* + The wind speed right at the turbine intake is increased <ref>The deflection at the front adds up two "surfaces" of wind. However, the resulting wind speed won't change drastically.</ref>
* + (tbd) less oscillating forces, the wind flow is about unidirectional at the turbine: less vibrations and less wear at the rotating parts, more static and less dynamic thrust at the bearings, less torque ripple and cyclical stress.
* - More material is used for the construction of an '''''EVA''' wt'': two bearings, arms and static wings. However, these additional parts are not difficult to manufacture, as the surfaces are all plane.

Who can help with FEA + fluid dynamics and simulate the wind flow at various EVA wind turbine designs? We want to investigate what wing form the intake should have and at which angle it should be mounted. Also:
Does it increase the efficiency if there's another, longer planar surface at the right of the intake parallel to the wind direction (The position where only a short, structural surface is shown in the sketches)

<gallery>
File:ETEMUcom_EVAwt7_top_detailed_diagramm.jpg|Normal airflow in a VAWT at the maximum torque moment. Note the non-uniform airflow with varying surfaces as the turbine blades advance.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt7_top_detailed_diagramm.jpg</ref>
File:ETEMUcom_EVAwt8_intake.jpg|Airflow in the '''''EVA''' wt'' design. View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake.jpg</ref>
File:ETEMUcom_EVAwt8_intake_top_iso.jpg|Example of a simple constructional integration of the '''''EVA''' wt'' design with sheet material. ISO-View from the top.<ref>http://etemu.com/p/evawt/ETEMUcom_EVAwt8_intake_top_iso.jpg</ref>
</gallery>

=Calculations and Simulations=
[[File:Better_metric.gif|thumb|All calculations are made in the metric system. This is the logo for the Jamaica Metrication Board, which completed its work in 1996.]]
All calculations are made in the ''metric'' system. Corrections and additional approaches are always welcome.

Let's start with the base mount.
As the design outlines state we won't start with a turbine greater than 4 m² due to restrictions in Europe pointed out by Detlef Schmitz. A wind surface of 4 m² equals a 2 m diameter rotor with a height of 2 m.

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>C_d</math> = Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> = Area of turbine = max 4 m² 
<math>v_{wind}</math> = Wind speed in m/s

<math>F(50\frac{m}{s})=\frac{1}{2} \times 1.2\frac{kg}{m^3} \times 1.0 \times 4m^2 \times 50\frac{m}{s}^2 = 6000 N</math> 
<math>F(30\frac{m}{s})=2160N</math> 
<math>F(20\frac{m}{s})=960N</math> 
<math>F(10\frac{m}{s})=240N</math> 
<math>F(5\frac{m}{s})=60N</math> 

TODO: Leverage should be taken into account here. How to calculate the load at the bearing points?

TODO: Consider serious safety factor for robustness and against oscillations.

Maximum wind speed the turbine has to withstand:
{|
|IEC wind class
|I
|II
|III
|IV
|----
|50-year-maximum
|50 m/s
|42,5 m/s
|37,5 m/s
|30 m/s
|----
|average wind speed
|10 m/s
|8,5 m/s
|7,5 m/s
|6 m/s
|----
|}

Example for a classification in Germany, Berlin: The mean wind speed is classified above IEC class IV with an average value of 2.3 - 3.6 m/s at ground level <ref>equals a mast height of 10 m or below</ref> without any obstacles.

IEC classes are realistic for higher wind zones, industrial wind turbines are usually mounted at >50 m. We are safe with an IEC class IV design. The design should be build for a maximum load of <math>F(30\frac{m}{s})=2160N</math>.

==Estimating the power output of the VAWT==

=====Power available in the wind:=====

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind. It is available as kinetic energy due to the moving mass of the air. 
<math>\rho</math> = Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math> = Area of turbine = max 4 m² at a small scale turbine 
<math>v_{wind}</math> = Wind speed in m/s 

=====Power available from the turbine:=====

This is the estimated ''mechanical'' wind power conversion.

:<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>
while 
<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \linebreak
\rho_{good} = 35% \linebreak
\rho_{superbVAWT} = 40% \linebreak
\rho_{superbHAWT} = 50% \linebreak
\rho_{limit} = 59% \linebreak
</math> 

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? Tbd!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

==Other links==
* [http://www.rhein-zeitung.de/regionales/neuwied_artikel,-Energiemarkt-Frischer-Wind-weht-aus-Asbach-_arid,247585.html non OS example 1]
* http://www.fundamentalform.com/html/involute_wind_turbine.html
* http://www.daswindrad.de/forum/viewtopic.php?f=2&t=21
* http://www.tinytechindia.com/windenergy.htm
* http://www.macarthurmusic.com/johnkwilson/MakingasimpleSavoniuswindturbine.htm A bit more efficient than a standard Savonius
* https://www.youtube.com/playlist?list=PL212B7C0D6057AC28 youtube playlist

====Daniel====
* http://www.youtube.com/user/danielturbin/videos?sort=dd&view=0 Wind is only one of many nice things he did
* http://www.maskinisten.net/viewtopic.php?t=8655 Forum with pictures and tests explained in Swedish

==Sources==
<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

DiVER/en

2013-04-06T20:18:14Z

Shure: /* DiVER.Wilssen */

{{DISPLAYTITLE:DiVER}}
{{Germany/en}}

==Introduction==

DiVER:
'''Di'''rect Current low '''V'''oltage '''E'''lectrical Grid for '''R'''enewable energies

*Any voltage over about 60VDC is not safe to the touch
*Any voltage over 60VDC needs a special license to operate in Germany, e.g. you may not build and connect a grid over 60V, unless a proper Electrician checks everything (VDE)
*Small permanent magnet alternators used in a generator at a wind turbine or a water turbine usually operate at below 100V
*It is very expensive to generate a true sine wave alternating current out of low voltage DC from the renewable energies
*Solar panels output low voltage DC
*TEG (thermo electric generators) output low voltage DC

Only a few systems really do need the high voltage AC of 230V or 110V.

*Desktop Computers (although terribly inefficient compared to laptops and smartphones) do need 12 VDC, 5 VDC and 3,3 VDC.
*Laptops need about 12-20 VDC
*TFT Flatscreens run on DC, especially if they have an LED backlight.
*Mobile phones, smartphones, tablet PCs etc are all charged and run with 5VDC

Difficulties and negative points about a low voltage DC grid:

*Grid size is smaller with a lower voltage or:
*available Power is lower at the same AWG / cable dimensions
*special connectors have to be chosen

A hybrid 230 VAC + DiVER infrastructure for OSEG/FeFG: 230VAC for high power appliances like some machines, DiVER for any consumer electronics (wherever possible) and efficient lighting.

Household circuit breakers may be re-used for a DiVER grid, e.g. anything from 8-63A per phase.

System voltage:

*N: 0V, GND
*L1: 12VDC, 10-15VDC (one lead acid battery)
*L2: 24VDC, or higher, to be determined. e.g. 24-48VDC (three lead acid batteries)

A cheap NYM-J 2x2.5mm² (1 Phase) or 4x2.5mm² (2 Phase) cabling may be used for low power branches of the grid.

E.g. for L2 with nominal voltage 3x12V = 36V: equals three lead acid batteries connected in series. If fully charged, grid voltage at the source would be 3*14V = 42V, at empty batteries about 32V.

The L2 grid voltage (only the voltage!) may be compatible with PoE, Power over Ethernet 802.3af (802.3at Type 1) and 802.3at Type 2, if the grid voltage is above 40 V.

At 36V and 63A, there are 2268W available in the grid, if we assume proper cables and connectors. It depends on the application, but I would have switched over to 230 VAC already at this power rating.

One could make the 12V phase on/off grid redundant with one efficient ATX power supply+two Schottky diodes or with active switching. It is much easier to switch DC synchronous vs AC synchronous, because one does not have to establish a phase lock to get the waveform in sync.

==Smart DiVER==

The start would be to equip an energy monitoring system, like DiVER.Wilssen. Communication could take place via
*Wireless connections (even to non-grid-tied appliances. NRF24L01+, RFM, xBee)
*Wired LAN connection (expensive and uses additional cabling)
*PLC (Powerline Communication) with an Open Source protocol and hardware design.

Research: What about RS485 between two phases, would that be possible? Is a choke / low-pass needed at the low impedance energy sources and appliances? What frequency is used best for transmitting data via a modulated power line? Coupling via passive RC-highpass?
There might be an integrated circuit for low voltage DC PLC communication?

==DiVER.Wilssen==
The Wireless Logging System for Sourcing ENergy - Controller is monitoring some or all grid parameters and is connected with the BMS (battery monitoring/managment system) or may even contain BMS functions. Wilssen is the brain of a DiVER grid, Wilssen is recommended but not necessary for operation.

*battery voltage of each battery (multiplexed) (2s1p, 3s1p, 3s2p, 3s4p etc)
*battery bank voltage
*l1 phase current (has got to be signed for bidirectional measurement)
*l2 phase current (has got to be signed for bidirectional measurement)

*battery bank temperature sensor (OneWire preferred)
*over current protection
*under voltage protection
*Uninterruptable Power Source function.
*SSR<ref>Solid State Relay</ref> usage, no conventional electromechanical Relays.

At a future revision, Wilssen may also:

*switch on chargers or grid-tied SMPS (switch mode power supplies) if source impedance gets to high/grid voltage too low.

optional: digital ZVD (zero voltage diode) function via comparator+ISR at ADC or interrupt attached to a plain digital port pin. SSR could then be used as OC protection, UV protection and ZVD.

SSR module may be replaced with a MOSFET at low power applications.

===Wilssen Hardware===

*Voltage sensing should be through passive voltage dividers with appropriate headroom and a high impedance connection to the ADC, we don't need the galvanic isolation at these low voltages.

*Current sensing should not be shunt based, but rather with a hall effect sensor or inductive. At DC, inductive sensing is not possible I guess, so we have to stick to hall sensors.
The integrated current sensor packages from Allegro are quite expensive. The following will be suitable for a <200A grid.
Bidirectional integrated hall effect current sensor:
ACS759 ±50A to 200A
ACS756 ±50A to 100A

*SSR example:
100V, 100A type:
http://www.mercateo.com/p/139A-1779776/SSR_100A_100V_SIP_Typ_D1D100.html?showSimplePage=NO&ViewName=live~showGrossColumn&utm_source=product-search&utm_medium=web&utm_campaign=Halbleiterrelais#crydom-ssr-100a-100v-sip-typ-d1d100-crydom

*2row LCD display for easy overview at the controller, showing the momentary power consumption and accumulated energy, grid voltage, ...

==Physical Layout: Cabling, Sockets, Fuses==

If the infrastructure is build from scratch and completely new, then it's best to start with a hybrid AC/DC<ref>Alternating Current / Direct Current, not the famous rockband</ref> DiVER grid:

cabling:
*open or closed ring topology with branches, e.g. 3p AC household EIS: 1 x NYM-J 5G2.5, laid in parallel with 1x NYM-J 4x2.5 (up to 4x10)

Important: How to determine the cables other than by their inner topology? DiVER cables should be marked differently.

===Connectors, sockets, plugs, terminals===

Suggestions for sockets and plugs for DiVER:

*large screw terminals (which is somewhat legal, because the DIVER grid is safe to the touch )
*PowerCon sockets (expensive, proprietary, e.g. by Neutrik. How many poles?)
*SpeakOn sockets (moderately expensive, well suited because they carry 4 poles and are aimed for moderately high currents)
*XLR sockets (cheap, but can't carry much current. maybe for small appliances like phone chargers)
*Open Source screw terminals with M6 screws. 3D printed or milled.

*We could use the socket / connector system from another country far, far away. Thus not getting into trouble with the mains grid connectors.

Any other recommendations?

*CEE sockets are way too expensive, overkill and not meant for DIVER voltages. They may also be confused with the mains grid.

*DiVER Fuses, circuit breakers, Wilssen, BMS, PDUs and so on are encased in a separate enclosure and are nowhere near the mains.

XLR specifications from Neutrik NC3-FX

Capacitance between contacts ≤ 4 pF
Contact resistance ≤ 3 mΩ (inner)
Dielectric strength 1,5 kVdc
Insulation resistance > 2 GΩ (initial)
Rated current per contact 16 A
Rated voltage 50 V

===Separated or safety extra-low voltage (SELV)<ref>http://en.wikipedia.org/wiki/Extra-low_voltage</ref>===

IEC defines a SELV system as "an electrical system in which the voltage cannot exceed ELV under normal conditions, and under single-fault conditions, ''including'' earth faults in other circuits".

There exists some confusion regarding the origin of the acronym: "SELV" stands for "''separated'' extra-low voltage" in installation standards (e.g., BS 7671) and for "''safety'' extra-low voltage" in appliance standards (e.g., BS EN 60335).

A SELV circuit must have:
* protective-separation (i.e., double insulation, reinforced insulation or protective screening) from all circuits other than SELV and PELV (i.e., all circuits that might carry higher voltages)
* simple separation from other SELV systems, from PELV systems and from earth (ground).

The safety of a SELV circuit is provided by
* the extra-low voltage
* the low risk of accidental contact with a higher voltage;
* the lack of a return path through earth (ground) that electric current could take in case of contact with a human body.

The electrical connectors of SELV circuits should be designed such that they do not mate with connectors commonly used for non-SELV circuits.

<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Tiny Vertical Axis Wind Turbine (TiVA)

2013-04-06T20:15:14Z

Shure: /* Appendix */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]].

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Tiny Vertical Axis Wind Turbine (TiVA)

2013-04-06T20:14:57Z

Shure: /* TiVA applications */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<math>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</math>

<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>C_d</math> Coefficient of drag = 1.0 (cylinder Re > 100) 
<math>A_{wind}</math> Area of turbine 
<math>v_{wind}</math> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

<references />

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-04-06T20:14:20Z

Shure: Reverted edits by Shure (talk) to last revision by Tony Ford

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-04-06T20:13:24Z

Shure:

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

<html>
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<link rel="stylesheet" type="text/css" href="//www.htmlcommentbox.com/static/skins/bootstrap/twitter-bootstrap.css?v=0" />
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</html>

<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-04-06T20:12:50Z

Shure:

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.


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<references/>

[[Category: -OSEG 400 - Bereich Technologie]]
[[Category: -OSEG 401 - Windenergie]]

Hilfe:Open Source – Aber wie?

2013-04-06T19:56:49Z

Shure: /* Auswahl einer Open Source Lizenz */

==Wie veröffentlicht man eine Technologie unter einer Open Source Lizenz?==
Folgende Schritte sind nötig:
* Auswahl einer Open Source Lizenz.
* Veröffentlichung der Dokumentation der Technologie unter der Open Source Lizenz.

===Auswahl einer Open Source Lizenz===

Die meist verbreiteten Open Source Lizenzen sind

* GPL
* WTFPL (Do What The Fuck You Want To Public License)

Die oft verwendeten CC Lizenzen sind von [https://de.wikipedia.org/wiki/Creative_Commons#Die_sechs_aktuellen_Lizenzen Creative Commons] (CC):
* [https://creativecommons.org/licenses/by/3.0/de/ '''CC BY'''] (BY=Attribtion)- erfordert Namensnennung.
* [http://creativecommons.org/licenses/by-sa/3.0/de/ '''CC BY-SA'''] (SA=Share Alike) - erfordert Namensnennung und Weitergabe unter gleichen Bedingungen.
* [http://creativecommons.org/publicdomain/zero/1.0/deed.de '''CC0'''] - keine Bedingungen oder wenn möglich, kein Copyright (no Copyright)

Es gibt auch CC-Lizenzen, die restriktiver sind und nicht zu empfehlen, wenn man wirklich Freiheit den Benutzer geben möchte:
* [http://creativecommons.org/licenses/by-nd/3.0/de/ CC BY-ND] (ND=Non-Derivative) - erfordert Namensnennung und keine Bearbeitung. Nachteile:
** Keine Bearbeitung hindert gesetzlich die Kreativität der Benutzer.
* [http://creativecommons.org/licenses/by-nc/3.0/de/ CC BY-NC] (NC=Non-Commercial) - erfordert Namensnennung und nicht kommerzielle Nutzung. Nachteile:
** Ein nicht kommerzielles Werk darf gesetzlich nicht mit Werken unter CC BY oder CC BY-SA Lizenzen gemischt werden!

====Patent-Diskussion====
* Eine unter CC veröffentlichten Dokumentation kann man nicht patentieren, weil sie schon '''davor''' veröffentlicht wurde.
* Man darf aber die eigene '''Änderungen''' der Dokumentation patentieren, wenn die Lizenz nicht SA (Share Alike) ist. Wenn man sicherstellen möchte, dass die Änderung auch als Open Source veröffentlicht müssen, übernimmt man die [http://creativecommons.org/licenses/by-sa/3.0/de/ CC BY-SA] Lizenz.

===Veröffentlichung===

In der Dokumentation der Technologie (eine Webseite, ein Archiv oder eine Datei) sollte stehen:
* der '''Name''' der Lizenz.
* ein '''Link''' zu der Lizenz-Webseite.
* eventuell auch der '''Inhalt''' der Lizenz.

[[Category: -OSEG 300 - Bereich Organisation]]
[[Category: -OSEG 306 - Dokumentation, Standardisierung]]

OSE-US critics

2013-04-02T18:13:46Z

Shure: Created page with "(backup from OSE US' wiki entry due to Marcin's deletions) Apart from the well documented positive criticism OSE gets (TED, True Fans, ...) we hereby want to give negative cr..."

(backup from OSE US' wiki entry due to Marcin's deletions)

Apart from the well documented positive criticism OSE gets (TED, True Fans, ...) we hereby want to give negative critics a chance to be heard. Some of them seem very constructive and might help us and OSE as an organisation to become better:

<blockquote>It is worth noting that '''OSE is hierarchically structured''' and that direct '''democracy is completely absent''' from its values. Folks should push for a democratized OSE/FeF giving participants democratic
control over the group.<ref>Marcus, March 8. 2013 http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately </ref> </blockquote>

<blockquote>There were developers who left because there is no profit sharing for development work and labour when stuff got sold.
ie, you put a lot of time and effort improving the GVCS, and the piece gets sold, you get zilch of the net after material expenses. All went to OSE/Marcin.<ref>eBell, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately</ref> </blockquote>

<blockquote>All I see lately is voting to win money, etc. I understand the crowd funding thing didn't take off as envisioned. So no more bi-weekly ose mail? no updates anywhere (meaningful updates)<ref> Qdelima, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately </ref> </blockquote>

<blockquote>(...) there have been "ragequits" all the time over several years. Note how Yoonseo said he left also due in part by certain behaviour and comments by Marcin<ref>Marcin is the founder and self proclaimed leader of OSE</ref>.<ref>Beluga, March 15. 2013, http://forum.opensourceecology.org/discussion/1004/why-is-ose-so-quiet-lately</ref> </blockquote>
 
*Statement from Brianna, who was on site developing and fabricating GVCS products for 5 months as stated on http://forum.opensourceecology.org/discussion/comment/5310#Comment_5310:

----

As for me, I left for a few reasons.

(1.) '''Money'''. I was working out there for $10 per hour. Very small for the type of work I was doing- design and fabrication of the ironworker. I saw Marcin unwilling to pay even the most skilled labor more than $2k per month. If you aren't even willing to pay that, how on earth can you expect any quality results? At best you will be getting college students, like me, wanting to contribute, who don't have the skills to make a quality product. Or, you will be getting people doing it as a side thing, guaranteeing no results. I saw the bank accounts, and knew the organization had more than $400k in the bank. As a result, there was nobody there designing the machines. I didn't feel qualified to be designing this stuff. I felt like there should have been experts out there designing it so I could built it. There was nobody. I felt like I was defrauding the investors.

(2.) '''Lies about the quality of the products.''' The brick press produced shit for bricks. They didn't have one flat surface on them. I personally built 4 of these, which were all shipped out without proper testing. One was shipped out a year after it was supposed to be. The power cube worked for a week AT THE LONGEST.

(3.) '''Unsafe living conditions''' and insufficient infrastructure- when I was there, the well water was contaminated, and Marcin refused to fix it. There was literally algae the water tanks, and he was doing nothing to fix it. We had to either buy all water at the store, or drink from the RO system, which I had to personally install. The RO hardly produced 1/2 gallon per day to be spent among 15+ people because of the low pressure coming from the pump at the well. The well was also not producing enough to accomodate all the people there, so we could only use toilets to poop, and had to have VERY short showers.

(4.) Everyone I talked to who was working there had told me, independently, that they had felt "decieved" at their recruitment. That '''they had been lied to to get to come out there'''.
</blockquote>

----
 
*The CAD drawings seem to be inconsistent and lacking quality: http://forum.opensourceecology.org/discussion/915/ceb-press-iv
 
<references />

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-03-27T22:06:59Z

Shure: added whiteboard draft

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:SATAR_TimeTravel_draft_IMG_20130214_225536.jpg|512px|thumb|right|Time synchronization algorithm with dynamic hop time compensation and redundant allocation draft on a whiteboard. (WIP)]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-03-27T21:53:44Z

Shure: /* Hardware: */

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

==Hardware==
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-03-27T21:53:02Z

Shure: /* Main Controller: Wilssen core */

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

===Hardware:===
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

===Main Controller: ''Wilssen core''===
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

Wind Logging System for Sourcing ENergy – WiLSSEN

2013-03-27T21:49:55Z

Shure:

The '''''Wi'''reless'' / '''''Wi'''nd '''L'''ogging '''S'''ystem'' for '''''S'''ourcing '''EN'''ergy'' - Controller is a multi-purpose prototyping platform for (but not limited to) renewable energies. E.g. It can be used for monitoring all electrical parameters of a wind turbine generator or to sense the temperature in a room/machine/garden/aquaponic system wirelessly for over one year on a set of two AA-batteries.<ref>With one temperature read and transmitted every two minutes</ref>

''Wilssen'' is the brain of [[TiVA]] and checks all the voltages at any time the wind turbine is generating power.

==Team==
* [[Alex Shure]] – lead designer, schematics, PCB layout
* [[Achmed Touni]] - waveform sampling algorithm, FFT
* [[Benjamin Rudtsch]] - hard- and software development
* [[Leon Rische]] - software development: LED code, visual feedback functions

==Development==
'''IRC:''' #OSEG on freenode 
[https://github.com/etemu/wilssen '''Git repository:'''] Contains the source code, schematics, layouts and documentation (see [https://github.com/etemu/wilssen/commits/master latest commits]) - feel free to add issues or fork us. :-) 
[https://github.com/etemu/wilssen/issues '''Open issues:'''] Any issues / bugs / features of Wilssen's hard- and software. 
Any Questions may be asked [http://forum.opensourceecology.de/viewforum.php?f=38 in the Forum].

===Hardware:===
[[File:Wilssen_core_v0.201a.brd.png|512px|thumb|right|Unfinished top side of the PCB<ref>Printed Circuit Board</ref> layout of the [[Wilssen]] core module. v201a (WIP)]]
[[File:Wilssen_core_v0.203a.brd_detail.png|512px|thumb|right|Detail of the PCB layout of the [[Wilssen]] core module. You can see the constant current sources on the left for the high brightness RGB LED. v203a (WIP)]]
[[File:20121124LXM2357_LX-M.de_.jpg|512px|thumb|right|[[Alex Shure]] at work with the PCB layout of the [[Wilssen]] core module. v202a (WIP)]]
[[File:Wilssen_core_v0.216a.brd.png|512px|thumb|right|[[WiLSSEN]] mainboard consisting of [[WiLSSEN]] core module in the middle plus peripherals: high power RGB LED driver (left), MicroSD card (upper left), LiPo charging (mid top), voltage + current sensing (right, not yet implemented) (WIP)]]
[[File:Wilssen_core_v0.215a.brd.png|512px|thumb|right|PCB dimensions: The WiLSSEN core module is one inch wide, while the physical dimensions of the full featured mainboard will be 75mm (a bit less than 3 inches) wide and 60mm high (about 2 1/3 inches). There will be an unpopulated, isolated 2mm strip at the top and the bottom for mounting purposes and tabbing, thus the 56mm dimension specified for the height. Note that the [[WiLSSEN]] PCB including tabs is half the size of a standard Eurocard.<ref>100x160mm - Eurocard is a European standard format for PCB cards, see http://en.wikipedia.org/wiki/Eurocard_(printed_circuit_board)]</ref>]]

*NRF24L01+ 2.4Ghz wireless communication. Mesh networking would be awesome :) - cluster networking should be possible with this Arduino library: http://maniacbug.wordpress.com/2012/03/30/rf24network/
*RGB LED PWM output (3 channels, R+G+B)

Current sensing:
*Passive on-board shunt resistor (only for low currents) via OpAmp -> 10bit ADC
*Allegro ACS712 integrated hall sensor with drift compensation, 1.2 mOhms (5A, 20A, 50A versions available) -> 10bit ADC

Voltage sensing:
*Passive resistor divider with high impedance coupling -> 10bit< ADC
*optional: decoupled voltage sensing via IC / galvanic isolation.

*(tbd) Option for waveform sampling, ''softscope'' (e.g. output the waveform at a specified sample interval in 10bit via serial over the wireless link)
*(tbd) Logging on MicroSD
*(tbd) Charging circuit for 4 NiMH cells / 1 lead acid gel battery.

'''We chose the Atmel Atmega168/328 series for the main controller, due to the great Arduino community.'''

==Main Controller: ''Wilssen core''==
[[File:Desktop_LED_driver_prototyping_LXD_7422.jpg|512px|thumb|right|LED driver testing: Prototyping the constant current sources with PWM input. Successful!]]
[[File:201211270426_Wilssen_core_schematic4.png|512px|thumb|right|Schematic of the [[Wilssen]] core module. (WIP)]]
*Optiboot bootloader compatible, thus Arduino compatible
*Main MCU: Atmel Atmega168, Atmega328

==Software==

===Microcontroller===
* RGB LED library
* Logic power supply battery voltage monitoring / watchdog
* Variable voltage protection routine
* Variable current protection routine
* Wireless communication protocol
* RPM calculation from alternator frequency
* MicroSD logging
* Sleep mode
* (tbd)

===Computer===
* GUI for real time analysis

===Communications===

This is a draft for the communications.

We need a transparent protocol for seperate layers of communication;

If there is only one WiLSSEN controller (a single leaf node) and you wire it to a PC/Mac:
* (serial) WiLSSEN leaf node <-> host

For a stationary installation, for example in your garden or on the roof without a wired connection:
* (wireless) WiLSSEN leaf node <-> WiLSSEN gateway [exit node] <-> host|LAN|WAN

When combining WiLSSEN controllers in a peer to peer network:
* (wireless) WiLSSEN node <-> WiLSSEN node <-> WiLSSEN node ( <-> host)

The gateway node needs to forward any traffic from the nodes to a connected host via serial or to the LAN/WAN via ethernet:
* (serial/eth) WiLSSEN gateway <-> host|LAN|WAN

A gateway always listens for traffic and handles it accordingly. A leaf node may sleep for extended periods, only waking up for the occasional keep-alive packet and status report. If it is not busy with a task, it should sleep and power off the communication electronics. Except when it is in debug mode, of course.

===Network with multiple [[WiLSSEN]] nodes===

Nodes are automatically configured in a tree topology, according to their node address. Nodes can only directly communicate with their parent and their children. The network will automatically send messages to the right place: 
Node 00 is the ‘base’ node. Nodes 01-05 directly communicate with Node 00, but not with each other. So for Node 01 to send a message to Node 02, it will travel through Node 00. Nodes 011, 021, 031 and so on are children of Node 01. For Node 011 to send to 02, it will send to 01, then to 00, then to 02. Therefore, if you put a Node 011 on your network, be sure that there is a Node 01 on the network, and it’s powered up, and it’s in range! <ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

If there is a missing branch in the tree aka. a node is down, then the communication which is piped through that very node won't be handled. A fix for this would be to implement a self-organizing mesh network. However, a single NRF24 chip has only a few communication pipes and the the implementation of a true mesh network is a lot more sophisticated than a hard coded tree or star topology.

===The [[WiLSSEN]] protocol===

Nodes can communicate over the wireless network with the [[WiLSSEN]] protocol. ManiacBug's RF24Network library<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref> is used for the Nordic NRF24L01+ wireless module interfacing.

The RF24Network sends two pieces of information out on the wire in each frame, a header and a message. The header is defined by the library, and used to route frames to the correct place, and provide standard information. This is defined in RF24Network.h:

<syntaxhighlight lang="c">
/**
* Header which is sent with each message
*
* The frame put over the air consists of this header and a message
*/
struct RF24NetworkHeader
{
uint16_t from_node; /**< Logical address where the message was generated */
uint16_t to_node; /**< Logical address where the message is going */
uint16_t id; /**< Sequential message ID, incremented every message */
unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */
unsigned char reserved; /**< Reserved for future use */
... </syntaxhighlight>

The message is application-defined, and the header keeps track of the TYPE of message using a single character:

<source lang="bascomavr">unsigned char type; /**< Type of the packet. 0-127 are user-defined types, 128-255 are reserved for system */ </source>

For [[WiLSSEN]], we have these predefined message types:

*A: ACK
*B: Battery voltage

*L: Light protocol message, e.g. DMX/OSC

*P: Ping
*R: Reset/Reboot, After a successfull bootup
*S: Sensor value, e.g. a temperature sensor reading
*T: Time synchronization paket

This message is defined in the example, in S_message.h of the RF24Network library:<ref>http://maniacbug.wordpress.com/2012/03/30/rf24network/</ref>

<syntaxhighlight lang="c">
/**
* Sensor message (type 'S')
*/

struct S_message
{
uint16_t temp_reading;
uint16_t voltage_reading;
S_message(void): temp_reading(0), voltage_reading(0), counter(next_counter++) {}
char* toString(void);
};</syntaxhighlight>

This simply contains a temperature and voltage reading. These values are 8.8-bit “fixed point” values, the high byte is the decimal part and the low byte is the fractional part. For example, 3.5V is represented as 0×380. Also included is a method to convert it to a string for easy printing.

==Draft for usage as a multi-phase alternator controller==
Controlled parallel-serial generator switching system:
A turbine could be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.
==Brainstorming (deprecated)==
What micro controller platform should we choose for ''Wilssen''?
*AVR: Atmel ATmega328 (AU, PU) (pico power series) (8bit)
*MSP430: Value line, e.g. MSP430G2231IPN14 (16bit)

One MSP430G2231IPN14 16bit micro controller could work for ''ages'', at as low as 2V, it may consume 1 mW = 1/1000 W. Typical no-load best-case values from the MSP430 datasheet:
<blockquote>
0.1 µA RAM retention 
0.4 µA Standby mode (VLO) 
0.7 µA real-time clock mode 
220 µA / MIPS active 
</blockquote>

Excellent values! An 8-bit Arduino looks pretty old school against these numbers. ;-)

pro MSP430, con AVR/Arduino:

* the price! can be bought with a programmer for USD 4.30 vs Arduino USD 25.00 or a third-party Arduino for maybe USD 18.00 - This is a serious difference.
* even the single MCUs are cheaper, also, the AtMegas for an Arduino bootloader are hard to get.
* less external parts for operation at high speeds, Arduino/atmega168 and 328 need an external oscillator to operate at full speed (16 Mhz)
* runs stable over a wide range of input voltage down to 1.8V
* an excellent sleep mode with RAM retention at only 0.1µA and great power efficiency. 220µA in full operation mode is an excellent figure for off-grid low energy applications. Almost no load to the turbine. Can also be powered by a "Joule Thief" and a single old AA battery, or just two old AA cells in series (3V). That should last for ages, at a constant current of 0.25 mA and an old battery of 1000 mAh, the unit will still run for 180 days, and the MSP430 can be operated with a supply voltage as low as 1.8V.

con MSP430:
* less memory, but this depends on the package, (there are top-end msp430 processors which cost less than $1 vs an ever-expensive-avr)
* less libraries available, smaller community

A nice solution:
=> Write clean C-code and let it be compatible with MSP430 and AVR compilers. Some Arduino projects were easily ported to the MSP430.

===Draft for a closed control loop:===

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.
<references/>

Diskussion:Mathtest

2013-03-19T12:13:06Z

Shure: Created page with "<math> \rho_{simple} = 20% \linebreak \rho_{decent} = 30% \\ \rho_{good} = 30% \\ \rho_{superbVAWT} = 40% \\ \rho_{superbHAWT} = 50%. </math> linebreaks and their shortcuts (..."

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

linebreaks and their shortcuts (\\) are not interpreted. :(

--[[User:Shure|Shure]] ([[User talk:Shure|talk]]) 13:13, 19 March 2013 (CET)

Mathtest

2013-03-19T12:12:13Z

Shure:

$
\newcommand{\Re}{\mathrm{Re}\,}
\newcommand{\pFq}[5]{{}_{#1}\mathrm{F}_{#2} \left( \genfrac{}{}{0pt}{}{#3}{#4} \bigg| {#5} \right)}
$

We consider, for various values of $s$, the $n$-dimensional integral
\begin{align}
\label{def:Wns}
W_n (s)
&:=
\int_{[0, 1]^n}
\left| \sum_{k = 1}^n \mathrm{e}^{2 \pi \mathrm{i} \, x_k} \right|^s \mathrm{d}\boldsymbol{x}
\end{align}
which occurs in the theory of uniform random walk integrals in the plane,
where at each step a unit-step is taken in a random direction. As such,
the integral \eqref{def:Wns} expresses the $s$-th moment of the distance
to the origin after $n$ steps.

By experimentation and some sketchy arguments we quickly conjectured and
strongly believed that, for $k$ a nonnegative integer
\begin{align}
\label{eq:W3k}
W_3(k) &= \Re \, \pFq32{ \\ \frac12, -\frac k2, -\frac k2}{1, 1}{4}.
\end{align}
Appropriately defined, \eqref{eq:W3k} also holds for negative odd integers.
The reason for \eqref{eq:W3k} was long a mystery, but it will be explained
at the end of the paper.

[[Category: Tests]]

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:11:12Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \linebreak
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:10:01Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy 
<math>\rho</math> Density of air = about 1.2 Kg/m³ 
<math>A_{wind}</math>Surface area of the wind facing functional turbine area 
<math>v_{wind}</math>Wind speed in m/s 

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:09:10Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

|<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy
<math>\rho</math> Density of air = about 1.2 Kg/m³
<math>A_{wind}</math>Surface area of the wind facing functional turbine area
<math>v_{wind}</math>Wind speed in m/s

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:08:49Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy
<math>\rho</math> Density of air = about 1.2 Kg/m³
<math>A_{wind}</math>Surface area of the wind facing functional turbine area
<math>v_{wind}</math>Wind speed in m/s

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:08:37Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy
<math>\rho</math> Density of air = about 1.2 Kg/m³
<math>A_{wind}</math>Surface area of the wind facing functional turbine area
<math>v_{wind}</math>Wind speed in m/s

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:08:09Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

:<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy
:<math>\rho</math> Density of air = about 1.2 Kg/m³
:<math>A_{wind}</math>Surface area of the wind facing functional turbine area
:<math>v_{wind}</math>Wind speed in m/s

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:07:52Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

:<math>P_{wind}</math> is the power, which is available in the wind, as kinetic energy
:<math>\rho</math> Density of air = about 1.2 Kg/m³
:<math>A_{wind}</math>Surface area of the wind facing functional turbine area
:<math>v_{wind}</math>Wind speed in m/s

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:04:55Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

| <math>P_{wind}</math>| is the power, which is available in the wind, as kinetic energy
| <math>\rho</math>|Density of air = about 1.2 Kg/m³ |
|<math>A_{wind}</math>|Area of turbine |
|<math>v_{wind}</math>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

Tiny Vertical Axis Wind Turbine (TiVA)

2013-03-19T12:04:34Z

Shure: /* Power estimation and electronics */

==Introduction==
Part of the modular [[Wind Turbine]] system is a downscaled VAWT called [[TiVA]] with tiny dimensions. With these inexpensive, small prototypes we can have a fast prototyping and research pace. Any successful design approaches may then be scaled up and used at larger turbines.

The '''Ti'''ny '''V'''ertical '''A'''xis Wind Turbine is a general prototype model and testing platform for a larger wind turbine, and also the prototype for the Apollo-NG Zephyr Wind-Park Construction Kit. [[TiVA]] and [[Wind Turbine]] specifications started with a joint development venture between [http://www.etemu.com etemu.com] and [http://apollo.open-resource.org Apollo-NG]. All information is released open source and for free, for a better world and for the fun of open collaboration. (CC BY-SA)

==Status==
The '''[[TiVA]]''' is currently in the research phase of product development, we are focusing on the dimensions and design of it's single components right now with 3D modeling and simulation parallel with the real life prototyping: We encourage the use of CAE, are working with 2D/3D CAD, and made first steps in simulating with [[CAD_tools|CFD + FEA]].
We try to minimize it with designing and calculating as much as possible, but real life testing is of course very important, too. A wooden rotor base with bearings has already been machined, NACA0018 wings have been prototyped and tested. First results are, that lift profiles like the NACA0018 airfoil are very inefficient at small turbine dimensions and low wind speeds, but efficient at large dimensions and medium to high wind speeds. This is because the critical Reynolds number can be accomplished at a large diameter, but not at a small turbine.

==Prototyping==
We are gathering the resources for the first prototypes, here is a rough bill of materials for a first prototype: [[Media:Tiva_bom_prototype_p1.pdf]].

Do '''you'''<ref>yes, I mean you, my dear reader. :)</ref> have something available for this project? ''Please'' add yourself to this list and describe the parts, tools or experience you have to share.

TODO: post a list with all the parts needed for one TiVA.

NICE TO HAVE and still searching for this project:
Someone with the ability to establish FEM simulations of different
rotor type models and mechanics to analyze stress points in the
mechanics and to optimize the rotors performance.

===[[Alex Shure]]===
As I work at [http://www.etemu.com etemu.com], I have access to an electronic lab and some parts which could come in handy for a TiVA prototype. --[[User:Alex Shure|Alex Shure]] 13:23, 3 April 2012 (CEST)

===Detlef Schmidt===
Detlef offered to build at least one prototype for our wind turbine project.

===YOU===
Yea, YOU! Please add yourself to this list if you have anything you can supply or want to contribute. Posts may be in English or German. Link to your profile or drop [[Alex Shure|Alex]] a line with your E-Mail, so we can get back to you if we need anything. :-)

''Funding with parts or money is very welcome!''

==TiVA design outlines==
[[File:20120513LXM08559_LX-M.de_TiVA_CAD-003.jpg|512px|thumb|right|We encourage the use of CAE and work with 2D/3D CAD.]]
<50cm long parts can be cut out at almost every small CNC milling machine.

48cm wings can be made out of:

# styrofoam, Styrodur etc with a hot wire CNC cutter
# the famous 2-by-4s with a planer
# like an R/C plane wing with wooden rips and a foiled surface
# sheet metal, aluminium sheeting bent over cores [rips]
# wooden sheet material
# plastic pipes

fixed main shaft: Do = 8 mm, 608ZZ radial single race bearings
rotating turbine assembly, rotor shaft where the bearings seat: Di = 22 mm

At this size, a single I-beam design should be suitable, not a dual-bridge-H-rotor assembly.

A V rotor looks promising, too. Resource demand is further reduced with this type of rotor. two bladed or three bladed? apparently, two bladed designs have severe problems with low wind conditions and self-starting issues => three bladed.

V-rotor advantages:
* least amount of material for a given lift-type wing surface
* best wing volume vs static structural volume ratio
* only one wing-fixture-point
* no bridges, less moving parts
* less connections, less machining operations, less screws or welds
* dissassembly is easier
* uses a higher surface at a larger height, less turbulences at the ground
* (tbd) less prone to oscillations?
* snow can't set onto most of the rotor
* can be adapted to also use up-winds in urban environments, especially interesting at the top of buildings.

__ __ <-test if winglets make a difference
\ / <- place a rope here, or lower;
\----/ <- to cope with centripetal forces at high rpm
\ / <- wings in V-form
\/ <- plate with wing-fixtures and seats for the two bearings
|| <- shaft/rotor coupling with two bearings
_/\_ <- any type of stand or clamp, generator, electronics

>I was thinking that we can't have a reliable ''absolute'' measuring device, so if all devices are built the same way then we can have a ''relative'' measuring device...
>>That is right, because there is no wing-tip-speed ratio at drag rotors. Perfect no-load drag wings have a wing-tip-speed ratio of one, thus rotating as fast as the wind ;)
>we would have to have half-cups as wings to form an actual absolute wind speed measure device like those things you can buy and don't put any load at the generator.

*Build a lovely grid and show, that wind turbines can be fun - we visualize the unused wind speed and energy. Plus it would be easy to deploy and portable, system voltage of 5V would provide charging power for mobile phones etc. USB power output could be easily done, fed by a 5 V buck-boost converter and 4 AA cells.

*can serve as a measure+log device for wind speeds
*has on-board electronics: switching power supply, 3.3V or 5V system voltage for MCU and electronics+LEDs, goldcap ?, mcu recommendation: either a low power ti MSP 16bit on a launchpad or the ordinary Atmel Atmega 328(pu) with an Arduino bootloader (or derivative) -> both would be diy-friendly and cheap.
*logging shield with shunts and opamps, goldcap, hprgb shield with logic level mosfets, software pwm.
*Reliable measurement is difficult in many ways, because devices would have to be calibrated in a (diy) wind tunnel. But let's see how far we get.
*can be deployed on a field, in an urban environment etc, flexible and mobile.
*one high power RGB LED acts as a universal signal: can be an indicator for wind speed, keep-alive.. or a 3 x 8 bit digital pixel. 
If deployed in an array on a field or in an urban environment: in low natural light conditions, at sundawn or in the night, the wind pattern can be determined by the flash+color pattern of the small wind turbines. MCU logging onto e.g. micro-sd card or via wireless link is an optional step. 
It would be a very cool art piece at night if all turbines would be connected to a master (which would be easy outdoors on a field) or connected in a grid. A pattern could be generated and all turbines could flash in sync. single flashes could be emitted with full power even if the wind conditions are bad, just the off-periods may be pretty long then.
*nodes may be connected (for example a cheap NRF24L01 node-based-network) or even simpler:
*'''the hp-LED is used as a transmitter and a cheap photo transistor as a receiver.''' Think of an infra-red remote control but with visible light and with much more power.
#Use a present IrDA protocol, for example IrSimple. (check the web for existing implementations and libraries in C for the MSP or AVR platform.)
#A system similar to [[ROnja]], but without any lenses. Maybe [[clock]] can help us out?

*[[TiVA]]s can be attached to the top of a tree, especially to free-standing ones. No pole required and higher wind speeds gained: ''win-win''.

*For a rough estimation, if the VAWT is working and how the wind condition is: Stick a thick wool or thin polythene (bin liner) tell-tales onto the top of the blades. This gives an indication of the relative speed of the blades and it is quite simple to see if the turbine is just being blown around by the drag on the downwind rotor or 'actually' running.

*A tell-tale in the centre of the rotor between the blades; so one can see the airflow through the rotor. As the rotor starts this will still blow out sideways, but when the rotor is running (without any load), it will hang limp indicating very little air flowing through the turbine. A gust or putting load on the turbine/generator will cause it to blow out sideways due to the wind which gets through.

== Mechanics ==

=== Forces ===

:<m>F_{pole} = \frac{1}{2} \times \rho \times C_d \times A_{wind} \times v_{wind}^2</m>

<m>\rho</m> Density of air = about 1.2 Kg/m³ 
<m>C_d</m> Coefficient of drag = 1.0 (cylinder Re > 100) 
<m>A_{wind}</m> Area of turbine 
<m>v_{wind}</m> Wind speed in m/s

[[File:20120410LXM213251_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|A board of spruce ready to be worked on with a planer.]]
[[File:20120410LXM213259_etemu.com_airfoil.jpg|400px|thumb|right|alt=photo of a piece of spruce|After the first few steps of planing the edges.]]
[[File:20120410LXM215603_etemu.com_airfoil.jpg|400px|thumb|right|alt=Work in progress photo of a wooden NACA airfoil made with a table saw and a planer out of spruce|Work in progress photo of a wooden NACA airfoil made with a table saw and a planer. The wood (spruce) used here is of rather low quality and split up at the trailing edge.]]

=== Rotor and wings ===

Compared to drag-only type rotors (Savonius), the lift-only type rotors (Darrieus) haven proven to be generally less suitable for low wind environments and for small sized rotors. However, the maximum speed of drag-only type rotors is always lower than a comparable lift-only type rotor, because a lift-only type rotor can rotate faster than the wind speed at the tips but with less torque. A drag-only type rotor can develop more torque, even at early stages in low wind conditions. At a large turbine diameter with a direct driven alternator, this would require a very specific and resource-intensive generator to accommodate for the very low rotational speed. A typical low end for a direct driven axial flux permanent magnet alternator with many poles is about 150 revolutions per minute. Everything under 150 rpm means huge additional resource investments into rare earth magnets and loads of copper (windings).

For the very small [[TiVA]], the research focus will be on three wing types, either of them mounted on a H (with arms) or V (with a base mount) or sandwich (base and top plate) shaped rotor:

# A lift-only type wing profile. The wings are formed by one (''NACA'') profiled element or segments of pipes, e.g. made of DN100-PE-tubes (standard sewer piping in Germany)
# The Van Canstein wing form and further derivatives based on it, with less parts if possible.
# The Lenz2 wing profile, a combined lift-and-drag profile developed by Edwin Lenz from windstuffnow.com.

The lift-only type wing profile has been successfully tested by now with the NACA0018 airfoil. Testing concluded that we will not further investigate lift profiles with TiVA, as the Reynolds number is much too low at these small dimensions, thus the rotor could not revolve faster than a TSR<ref>Tip Speed Ratio</ref> of 2 with not load. A TSR of at least 3 would be required to be reasonably efficient.
In addition to the low TSR, the NACA0018 profile had a low performance in low to medium wind speeds vs a crude drag profile and could not self-start at all.

=== C-Type Rotor ===

The "Van Canstein" wing form is a special type of H-rotor with a combined lift-and-drag-wing.

=== H-Type Rotor ===

* may be the simplest design, very simple wing forms are possible.
Complex Darrieus rotor: wings in helix-form, spiraled, lift-type
Simpler H-rotor: wings straight. May even be without any profile. Lift-type or Drag-type or lift-drag-type -> C-rotor

====C-type vs simple H-type====

con C-type, pro H-type:
* C-type requires two parts to form a wing -> more material
* wing tip has to be bent into an aerodynamic shape -> more complexity, especially at the mounting points
* upper wind speed limit is lower

pro C-type, con H-type:
* C-type requires lower wind speed, creates higher torque at lower wind speeds
* usable bandwidth of wind speed is higher

=== NACA0018 profiled straight wing fabrication process ===

One idea is to make a wing out of two symmetrical pieces. One half of the profile could be milled out of wooden sheet material or planed out of a pre-cut board by hand. Half of a profile can be hold down and clamped because one side will still be flat. The two halves are then glued together.

The pictures at the right show a simple profile made out of thin boards. They are cut out of a sheet with a table saw and then planed by hand.

==Power estimation and electronics==

All calculations are made in the metric system. Corrections and additional approaches are always welcome.

Power in the wind:

:<math>P_{wind} = \frac{1}{2} \times \rho \times A_{wind} \times v_{wind}^3</math>

|<math>P_{wind}</math>| is the power, which is available in the wind, as kinetic energy|
|<math>\rho</math>|Density of air = about 1.2 Kg/m³ |
|<math>A_{wind}</math>|Area of turbine |
|<math>v_{wind}</math>|Wind speed in m/s |

Estimated Wind-Power conversion (mechanical):

<math>P_{mech}=P_{wind} \times \rho_{turbine} </math>

while

<math>
\rho_{simple} = 20% \\
\rho_{decent} = 30% \\
\rho_{good} = 30% \\
\rho_{superbVAWT} = 40% \\
\rho_{superbHAWT} = 50%.
</math>

A tuned VAWT may have a best-case efficiency of 40%<ref>Can the EVAwt design yield more? To be determined!</ref>, while a simple drag-based turbine with no optimization nor special aerodynamics may have an efficiency of about 20%.

h_1=0.32 m 
d_1=0.32 m 
A_1=0.1024 m^2 
 
h_2=0.48 m 
d_2=0.32 m 
A_2=0.1536 m^2 

{|
|
|m/s
|km/h
|P_{0.1024m^2}[W]
|P_{0.1536m^2}[W]
|----
|
|1.8
|6.5
|0.35
|0.5
|
|----
|
|4.5
|16.00
|5.5
|8.2
|
|----
|
|6.25
|22.50
|15
|22.6
|
|----
|
|8.0
|29
|32
|48
|
|----
|}

{|
|
|m/s
|P_{0.1024m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.35
|0.07
|0.1
|----
|
|4.5
|5.5
|1.1
|1.65
|----
|
|6.25
|15
|3
|4.5
|----
|
|8.0
|32
|6.4
|9.6
|----
|}

{|
|
|m/s
|P_{0.1536m^2} [W]
|P_{\rho=0.2}
|P_{\rho=0.3}
|----
|
|1.8
|0.5
|0.1
|0.15
|----
|
|4.5
|8.2
|1.65
|2.5
|----
|
|6.25
|22.6
|4.5
|6.8
|----
|
|8.0
|48
|9.6
|14.4
|----
|}

*Assuming a bad (20%) or decent (30%) turbine design \rho_{turbine}=0.26
*A rather bad permanent magnet alternator with \rho_{alternator}=0.75;
*A normal synchronous rectifier with superb-by-design perfomance of \rho_{rect}=0.98;
*A buck-boost inverter with a good performance of \rho_{rect}=0.85;

<math>\rho_{overall}=0.25*0.75*0.98*0.85=0.16</math>

Conclusion: A 0.32 x 0.32 drag-only VAWT generates about P_{mech} = 0.1...10 W and in average German wind conditions (3 - 4 m/s??) about 0.5 - 1 W. If we have a good alternator (which will be easier at this size because of the high rpm) and a synchronous rectifier (rectifier not necessary if buck/boost power supply doesn't need DC, are there suitable packages for this mode?), most of the power will be available as an input for a buck/boost converter, which can operate reasonably well at these small power ratings.

Chrono developed a PDU (power distribution unit) which contains low power buck-boost inverters - maybe a small scale version can be powered directly by this wind turbine, generating only 5 V and 3.3 V, omitting the 12 V.

Assuming a worst-case average electrical power of 1 W after rectifying and regulating, one can still charge a cheap 4-pack of NiCd/NiMH (4 x 1.3 V = 5.2 V) which provides power for the system and for high power demands, e.g. activating the LED pattern at night. Charging all of the cells with 1 W from 0 % to 100 % takes (4 * 4 Wh) / 1 W = 16 h. At a wind speed of 8 m/s = 28,8 km/h and P_{el} = 48 W * 0.16 = 7.68 W, the batteries will be fully charged in just (4 * 4 Wh) / 7.68 W = 2 h 5 min.

One AA cell contains 1.3 V x 2500 mAh = 3.25 Wh of stored energy. We don't fully discharge the batteries, thus only 3 Wh will be used. However, taking charging and internal resistance losses and a safety margin into account, we need about 4 Wh of energy to store and retrieve about 3 Wh of energy.

4 AA cells equal 4 x 3 Wh = 12 Wh of energy. Without simultaneous recharging, this is enough to provide:

* five hours of one hp-LED shining at full brightness in white color or
* ten days of one hp-LED flashing at full brightness with one color at a duty cycle of 10%, e.g. on for one second and off for nine seconds.
* in real time without battery backup, the hp-LED may be pulsed at full power and 10% duty cycle at quite low wind speeds and 100% at >6.25 m/s.

==Main Controller: ''[[Wilssen]]''==

(moved to separate page: [[Wilssen]])

=== controlled parallel-serial generator switching system ===

The turbine can be actively regulated by Wilssen's load-balancing features, such as increasing or decreasing the load, up to the freewheeling no-load open-circuit state, or reconfiguring the alternator windings on the fly. As the coils are wound at least quadfilar, there are various possibilities to connect the windings.

Draft for a closed control loop:

example values:
V_out = 16V
V_sys = variable, depending on load
V_gen = variable, depending on wind input and switching and system voltage

#monitor V_out. if V_sys less than Vout, then
#serialize the windings,
##still to little voltage? -> if generator-coil-form-1 and many points are broken out of the coil, then serialize them in a pattern to gain more voltage
##too much voltage? never mind, either wait for a small period of time because the rotor has a mass and stores kinetic energy, which first has to be converted by the "new serial-wound-generator". the speed will drop eventually and the voltage will stabilize itself, OR
##rapidly switch between parallel and serial modes (if the load, e.g. the synchronous rectifier, can cope with the spikes (inductive..) and has appropriate switching abilities) and thus form an sort of automatic pulse width modulated, regulated, operation mode.
#if V_sys + Vdelta,hysteresis >Vout, then
#switch to parallel mode

other cases:

*any of the voltages exceed e.g. 56V: emergency mode:
* either make the generator windings float or short them.
: '''!! shorting may not be an option. only with temperature control of the generator and the semiconductors due to the heat generated at a shortcut.!!'''

*If all batteries are loaded and the current user power consumption level is minimal, the power surplus of the turbine should be fed into high power LEDs, pointing upwards from the base, lighting the turbine. This adds to protect the system of an unbalanced situation, when more power is generated than reasonably consume- or storable and at the same time to signal, that we still have more energy to share, inviting people to join, in a friendly and beautiful manner.

*In general, LEDs should also be incorporated at the controller: the controller should have a mosfet-switched control output, one 3W RGB led should display the wind speed or the battery voltage.. (on a scale from red to green and strobe patterns)

* 'high-tech' electronic idea: dual rotor on single pole design, counter rotating, brush-less royer converter, doubled rpm, less poles, switching power supply is already build in due to the royer converter, coil-in-coil, core coupling, voltage output may be quite high from the start. lower electrical efficiency? downside: needs IP67 protected circuits on both the rotor and the stator of the royer converter. upside: output voltage could be regulated on-board. also, input voltage may be very low depending on the setup.
* variation: a rotor with lift-type wings on top and a rotor with drag-type wings at the bottom. thus the lower rotor gains speed at lower wind speeds but has a top end speed of approx. lift-type/2, while the lift-type wing still accelerates in high wind speed conditions.

== Rectifier: active or passive ==

=== Passive Schottky-Rectifier ===

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. A bridge rectifier provides full-wave rectification from a two-wire AC input. The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input and nothing has to be controlled vs the active rectification, which needs to be very precisely controlled.

=== Active synchronous rectification ===

Active rectification, or synchronous rectification, is a technique for improving the efficiency of rectification by replacing diodes with actively-controlled switches such as power MOSFETs.

The constant voltage drop of a standard p-n junction diode is typically between 0.7 V and 1.7 V, causing significant power loss in the diode. Electric power depends on current and voltage: the power loss rises proportional to both current and voltage.

In low voltage converters, the voltage drop of a diode has an adverse effect on efficiency. One classic solution replaces standard silicon diodes with Schottky diodes, as in our Schottky-rectifier version, which exhibit very low voltage drops (about 0.3 - 1 volts). However, even Schottky rectifiers can be significantly more lossy than the synchronous type, notably at high currents (as the forward voltage drop of the diode rises with the current) and low voltages.

Replacing a diode with an actively controlled switching element such as a MOSFET is the heart of active rectification. MOSFETs have a constant very low resistance when conducting, known as on-resistance (RDS(on)). They can be made with an on-resistance as low as 10 mO or even lower. The voltage drop across the transistor is then much lower, meaning a reduction in power loss and a gain in efficiency.

==TiVA applications==
I would like to deploy 1-3 of these tiny turbines at a nearby off-grid mountain bike downhill track. I hope to gain the interest for renewable energy / wind turbines of any passenger who rides or cheers there at a race. --[[User:Alex Shure|Alex Shure]] 13:31, 3 April 2012 (CEST)

==Appendix==
This wiki entry evolved from a pad at apollo.open-resource.org with [[chrono]] & [[Alex]]. We try to keep Apollo's wiki and this OSE wiki entry synchronized, however, there might be variations or recent additions on either platform.

[[Category: Windenergie]]

<references />

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2013-02-21T13:44:09Z

Shure: Shure uploaded a new version of "File:WiLSSEN whiteboard drafts IMG 20130220 001337.jpg"

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