Wind Turbine/Research Development

=Overview=

Open Source Ecology is involved in researching, developing and building open-source technologies for clean, local electricity-generation. As well as solar power, we like wind power. Wind power or solar or both may be appropriate, depending on local materials and local weather conditions.

Specifically, we are interested in open-source designs for a wind turbine that can provide electricity for a small community. Small wind turbines like this are usually 7 feet (2m) to 25 feet (7.6m) in diameter.

Open Source Ecology Europe and -Germany are working on a prototype VAWT design: Germany/Wind_Turbine. Research and development is currently concentrated at 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.

Design specifications

 * Scalability - scalable from ??? to ???
 * Low-cost - must cost less than $1 per installed watt and $0.05/kWh produced on a medium speed site (6m/s average speed [13.4mph, 21.6km/h])
 * CAD files to allow parts to be digitally fabricated. We could just take an existing open-source design, and get one of our draftsmen to make the CAD file. Good CAD files could allow for scalable digital fabrication: the blades could be printed in a range of sizes, depending on what you need

Existing open-source wind turbines
Several wind turbines have already been open-sourced and it should be possible to use them for the Global Village Construction Set:


 * Zoetrope is a vertical-axis wind turbine made from common materials such as stove pipe, metal brackets, plastic sheet and a trailer hub. Generates about 150-200W in winds of 20mph (32km/h). Construction Guide. The major parts are: parts kit for $159 (unless you could order one from a Fab Lab/ a hackerspace with a water-jet cutter), 24 neodymium magnets for $140, trailer hub for $26. There are also a bunch of pieces like nuts and bolts, but those are the main one, and come to $425 excluding shipping.
 * OtherPower.com have several complete plans for wind turbines that can be built at home. Their site has -
 * Complete plans for a 10 foot (3m) turbine that puts out 100W in 10mph (16km/h) winds and 700W in 25mph (40km/h) winds.
 * Design of a 14 foot (4.25m) turbine that does 200W in 10mph (16km/h) winds and 1500W in 25mph (40km/h) winds. This is the record of a project rather than a replicable open-source design.
 * Chispito Wind Generator. Chispito is made from recycled/salvaged materials, completely open-source with clear instructions and designed for simplicity. Open-source instructions for building both the turbine and the tower are available. Each turbine generates about 100W; most people seem to use a bunch of them. This is probably smaller that what we are looking for.
 * http://www.scoraigwind.com/ has a lot of information on wind turbines, but no fully open-source plan
 * Open source alternator for wind turbines
 * Onawi is a not-for-profit organization dedicated to developing open-source wind turbines. No signs of progress yet, but watch this space.

What kind of turbine?
The first design decision we have to make is which kind of wind generator best suits our needs

Vertical Axis Wind Turbine
Verical Axis Wind Turbines or VAWTs offer a number of advantages over traditional horizontal-axis wind turbines (HAWTs). With careful layout they can be packed closer together in wind farms, allowing more in a given space. This is not because they are smaller, but rather due to the slowing effect on the air that HAWTs have, forcing designers to separate them by ten times their width. VAWTs are rugged, quiet, omni-directional, and they do not create as much stress on the support structure. They do not require as much wind to generate power, thus allowing them to be closer to the ground. By being closer to the ground they are easily maintained and can be installed on chimneys and similar tall structures.

In addition, by being closer to the ground, VAWTs have the ability to take advantage of the tunnelling effects of small buildings and structures (provided the structures are build close enough) small VAWTs are also used in corners of buildings (usually the corner of a balcony).

Although VAWTs are not as efficient as HAWTs they are considered more reliable and much easier to maintain. Some disadvantages of VAWT are:


 * Some designs are non-self starting
 * Blade that moves into the wind also moves against the wind, slowing down the turbine. This could be addressed by a shield that adjusts to the direction of the wind and covers the blade that moves into the wind. This could be done with some kind of vane. However, this would complicate the design significantly, incl. bearings for the shield. So this may not be worth it ... probably easier to just build more VAWTs or build them bigger. But who knows ? Come up with a good sail/shield design and this might be just the breakthrough that VAWTs have been waiting for.
 * Gorlov helical turbine design which solves the pulsatory torque experienced by the blades during each revolution is patented.

A good step by step guide can be found on this link: a small Savonius wind turbine that takes advantage of the Venturi effect.

There is a small scale printable VAWT on thingiverse http://www.thingiverse.com/thing:6899

Airborne wind turbines
A turbine attached to a lighter-than-air ballooon, such as being developed by Magenn. I think we can reject this as too complex and too experimental for our purposes.


 * 1) Wind driven apparatus for power generation - expired patent for a tethered airborne turbine. This design generates power at the turbine and transmits it to the ground.
 * 2) High Altitude Wind Power at PESwiki

Kite generators
A high-flying power kite tethered to a generator on the ground. The kite tugs on the tether, which spins a turbine and generates electricity. All the machinery can be kept at ground level; only the sail is airborne. This allows for easy maintenance.

The two main advantages of this design are that reaches the more powerful winds higher up, and it may come in cheaper than a turbine. This report from the WPI Kite Power Team says there is an "anticipated 50% cost savings over wind turbines".

We can probably buy an off-the-shelf power kite. Here is a 5m2 one for $166. Here is a 2.7m2 one for $14. This seems to be a top-of-the-range one - it's $600 for 6.5m2. Alternatively, we could try to build our own kite.

This would need to be attached to the open-source electric motor we're designing, and a microcontroller. All the hardware is on the ground, which makes maintenance and set-up easier. The control will be the main design challenge.


 * 1) Ecoble article: Wind Power Generated From Kites
 * 2) at Delft University of Technology:Kite Power Could Generate Energy for 100,000 Homes
 * 3) Autopilot Arduino board for drones
 * 4) Saul Griffith on kites as the future of renewable energy
 * 5) Academic project assessing feasibility of kite power (link is to a 109 page pdf file). Gives technical details of the mechanism. Estimates 500W from a 2m2 kite if the average wind speed in 8m/s
 * 6) http://climatelab.org/Airborne_Wind_Energy_Systems
 * 7) WPI Kite Power Wiki - "dedicated to developing a new renewable energy technology - Wind Power from Kites. In this concept, large kites tethered to the ground are used to extract power from the wind. Kites can extract power more economically than wind turbines because they fly at higher heights than turbines can operate."
 * 8) http://www.kitegen.com/en/?page_id=7

Siting of Turbines
A critical step to make wind profitable or optimal is putting the turbine in the right spot or site (turbine siting). This involves two main factors: the speed of the wind and the turbulence in the wind. Since the energy available in the wind varies with (E ~ v^3) a site with slightly less speed can produce a lot less energy. Siting requires measuring the speed of the wind for at least a year with a measurement mast (or small weather station) in a spot close to the site of the turbine. There exist open-source software to then propagate the measurements (using more or less complex computational fluid dynamics) to find the speeds on the topography. One example: http://awsopenwind.org/

Technical Litterature
Burton, Tony. Wind energy: handbook [Wiley, 2001, EN]

Crome, Horst. Making a CK220 Profile blade [free, DE]

Chrome, Horst. Handbuch Windenergie Technik Sold at okobuch

Hansen, Martin O. L. Aerodynamics of wind turbines [ Routledge; 2nd edition (December 20, 2007), EN]

Hau, Erich. Wind turbines: fundamentals, technologies, application, economics [Springer; 2nd ed. edition (2 Sep 2005), EN]

Johnson, Gary Renewable Wind Energy Systems Revised January 29, 2004 [free, EN]

Software and Design tools
Qblade (TU, Berlin) Released under GPL. This software provides an open solution for the design and aerodynamical computation of wind turbine blades. QBlade also includes post processing of conducted rotor simulations and gives deep insight into all relevant blade and ro tor variables for verification, to compare different rotor configurations, or even to study the numerical algorithm (Blade Element Momentum Theory) and the dependency’s among the aerodynamic variables themselves. It integrates with XFOIL, also released under GPL. For more details see for example papers and research

XFOIL (MIT, Boston) Released under GPL. Used for design and analysis of subsonic isolated airfoils. Stuff you can do: Viscous (or inviscid) analysis of an existing airfoil, allowing forced or free transition, transitional separation bubbles, limited trailing edge separation, lift and drag predictions just beyond CLmax, Karman-Tsien compressibility correction, fixed or varying Reynolds and/or Mach numbers. for more see tutorials here, or here

FOCUS 6 (WMC Knowledge Center, Wieringerwerf, the Netherlands). Unknown license, but the development was partly paid by European and Dutch tax payers. FOCUS 6 is an integrated modular tool to design wind turbines and wind turbine components like rotor blades. For more than a decade, FOCUS has been used by the international wind turbine industry. more details in this presentation

NREL Simulation tools (NREL, USA), includes lots of tools for turbine design and simulation like AeroDyn, BladeFS, FAST, TurbSim, etc.

MBDyn (Politecnico de Milano, Italy) Released under GPL. MBDyn is the first and possibly the only free* general-purpose MultiBody Dynamics analysis software. MBDyn features the integrated multidisciplinary analysis of multibody, multiphysics systems, including nonlinear mechanics of rigid and flexible constrained bodies, smart materials, electric networks, active control, hydraulic networks, essential fixed-wing and rotorcraft aerodynamics. Integrates with Blender and NREL's AeroDyn. For wind turbine integration see this presentation

More

 * Turbine-less wind generator- how does it work?
 * 5 kW wind turbine kit- under $6k in parts, without tower.
 * 1 kW - http://www.hurricanewindpower.com/servlet/the-Wind-Turbine-Kit/Categories

Wind Power with Hydraulic Transmission
Back in the golden age of the Dutch, their booming economy was powered by wind in all sorts of incarnations (see article from Low-tech Magazine - Wind powered factories: history (and future) of industrial windmills). Wind provided a lot of energy but one big problem was that this energy had to be used at the time that it occurred, with very little ability to store it for later use. Now in the 21st century, we can use hydraulic implementations to solve this problem. As builders of the GVCS, we are quite familiar with hydraulic systems from projects such as LifeTrac. A hydraulic transmission can also be used for stationary applications and powerd by wind. The "mill" that harvests the wind is coupled to water pumps, generating hydrostatic pressure. With a storage reservoir (water tank at higher level), this energy is available at any time, powering hydraulic motors.
 * Patent (granted 2008): "Wind turbine with hydraulic transmission"