Unconventional wind turbines

This article deals with various types of wind turbine that differ from the standard type.

Ducted Rotor
Still something of a research project, the ducted rotor consists of a turbine inside a duct which flares outwards at the back. They are also referred as Diffuser-Augmented Wind Turbines (i.e. DAWT). The main advantage of the ducted rotor is that it can operate in a wide range of winds and generate a higher power per unit of rotor area. Another advantage is that the generator operates at a high rotation rate, so it doesn't require a bulky gearbox, so the mechanical portion can be smaller and lighter. A disadvantage is that (apart from the gearbox) it is more complicated than the unducted rotor and the duct is usually quite heavy, which puts an added load on the tower. The Éolienne Bollée is an example of a DAWT.

Maglev wind turbine
Magnetic levitation turbines are another form of wind turbines which can drastically increase power.

Co-axial, multi-rotor horizontal-axis turbines
Two or more rotors may be mounted to the same driveshaft, with their combined co-rotation together turning the same generator — fresh wind is brought to each rotor by sufficient spacing between rotors combined with an offset angle alpha from the wind direction. Wake vorticity is recovered as the top of a wake hits the bottom of the next rotor. Power has been multiplied several times using co-axial, multiple rotors in testing conducted by inventor and researcher Douglas Selsam, for the California Energy Commission in 2004. The first commercially available co-axial multi-rotor turbine is the patented dual-rotor American Twin Superturbine from Selsam Innovations in California, with 2 propellers separated by 12 feet. It is the most powerful 7-foot diameter turbine available, due to this extra rotor.

Counter-rotating horizontal-axis turbines
Counter rotating turbines can be used to increase the rotation speed of the electrical generator. As of 2005, no large practical counter-rotating HAWTs are commercially sold. When the counter rotating turbines are on the same side of the tower, the blades in front are angled forwards slightly so as to avoid hitting the rear ones. If the turbine blades are on opposite sides of the tower, it is best that the blades at the back be smaller than the blades at the front and set to stall at a higher wind speed. This allows the generator to function at a wider wind speed range than a single-turbine generator for a given tower. To reduce sympathetic vibrations, the two turbines should turn at speeds with few common multiples, for example 7:3 speed ratio. Overall, this is a more complicated design than the single-turbine wind generator, but it taps more of the wind's energy at a wider range of wind speeds.

Appa designed and demonstrated a contra rotor wind turbine in FY 2000–2002 funded by California Energy Commission. This study showed 30 to 40% more power extraction than a comparable single rotor system. Further it was observed that the slower the rotor speed, the better the performance. Consequently Megawatt machines benefit most.

Variable pitch HAWT
Several wind turbines have been designed with variable pitch blades. These allow greater efficiency. An example of such type is the Jacobs and the "Advanced Research Turbine" located at NREL’s National Wind Technology Center near Golden, CO, USA. Variable pitch blades are also being in diy-construction.

Furling tail and twisting blades turbines
In addition to variable pitch blades, furling tails and twisting blades are other improvements on wind turbines. Similar to the variable pitch blades, they may also greatly increase the efficiency of the turbine and be used in diy construction

Aerogenerator
The Aerogenerator is a special design of vertical axis wind turbine which could allow greater energy outputs.

Savonius wind turbine
The Savonius wind turbine is another special design wind turbine.

Augmented "G" model VAWT: "G" Model Wind Turbine (GMWT)
The "G" Model VAWT Turbine is equipped with three -self directioning- "Augmentation And Directioning Wings=AADW" placed outer section of classical Darrieus blades. The GMWT is capable to increase almost fivefold the efficiency of classical Darrieus Blades: AADW adjust itself to the wind direction without any external power. The result combination ("G" Model Wind Turbine) need very low cut-in wind speed, has self starting ability togetherwith high capacity factor. Detailed information is available in: http://www.windturbine-performance.com.

Aerial


It has been suggested that wind turbines could be flown in high speed winds at high altitude taking advantage of the steadier winds at high altitudes. No such systems currently exist in the marketplace. The idea of airborne wind turbines reappears in the industry every few years, and seldom (if ever) gets off the drawing board.

H-rotor
Another type is the H-rotor

Vaneless ion wind generator
For an unusual way to induce a voltage using an aerosol of ionised water, see vaneless ion wind generator.

Solar updraft tower
Wind turbines may also be used in conjunction with a solar collector to extract the energy due to air heated by the Sun and rising through a large vertical Solar updraft tower.

Piezoelectric wind turbines
Another special type of wind turbines are the piezoelectric wind turbines.

Wind turbines on public display
The great majority of wind turbines around the world belong to individuals or corporations who use them to generate electric power or to perform mechanical work. As such, wind turbines are primarily designed to be working devices. However, the large size and height above surroundings of modern industrial wind turbines, combined with their moving rotors, often makes them among the most conspicuous objects in their areas. A few localities have exploited the attention-getting nature of wind turbines by placing them on public display, either with visitor centers around their bases, or with viewing areas farther away. The wind turbines themselves are generally of conventional horizontal-axis, three-bladed design, and generate power to feed electrical grids, but they also serve the unconventional roles of technology demonstration, public relations, and education.


 * Australia
 * Blayney Wind Farm, New South Wales has a viewing area and interpretive centre
 * Wattle Point Wind Farm, South Australia has an information centre
 * Canada
 * OPG 7 commemorative turbine is a Vestas V80-1.8MW wind turbine on the site of the Pickering Nuclear Generating Station
 * Toronto Hydro - WindShare features a Lagerwey Wind model LW 52 wind turbine
 * China
 * Inner Mongolia's Huitengxile Wind Farm has 14 visitor centers to accommodate wind power tourists to the remote region
 * Lamma Winds in Hong Kong has a single Nordex N50/800 kW model with a rotor diameter of 50m and a nameplate capacity of 800kW
 * New Zealand
 * Brooklyn, Wellington, New Zealand has a 230 kW wind turbine
 * United States
 * Dorchester, Massachusetts - Local 103 of the International Brotherhood of Electrical Workers installed the first commercial-scale wind turbine within the City of Boston, a 100 kW unit from Fuhrlaender on a 35-meter tower with rotor diameter of 21 meters, visible from the John F. Kennedy Library
 * The Great Lakes Science Center in Cleveland, Ohio has a reconditioned Vestas V27 wind turbine with a nameplate capacity of 225 kW
 * Great River Energy's headquarters in Maple Grove, Minnesota has a NEG Micon M700 wind turbine, visible from Interstate 94
 * McKinney, Texas has a Wal-Mart store with several sustainability features, including two wind turbines manufactured by Bergey Windpower, of 1 kW and 50 kW nameplate capacity respectively
 * Sweetwater, Texas has a 2 MW 60Hz DeWind D8.2 prototype wind turbine for training students in the Texas State Technical College wind energy program
 * United Kingdom
 * GreenPark Business Park has an Enercon E-70 2 MW wind turbine adjacent to the M4 motorway, billed as the UK's most visible turbine
 * Renewable Energy Systems has a Vestas V29 225 kW wind turbine visible from the M25 motorway at its headquarters at Beaufort Court, Kings Langley, Hertfordshire

Observation deck
Some wind turbines on public display go one further, with observation decks beneath their nacelles.


 * Germany
 * One wind turbine of the type Enercon E-66 at Windpark Holtriem, Germany carries an observation deck, open for visitors.
 * Netherlands
 * The Siemens plant in Zoetermeer features a wind turbine with 40m blade length and an observation deck.
 * United Kingdom
 * Another Enercon E-66 wind turbine with an observation deck belonging to Ecotricity is in the English town of Swaffham.