When most people think of wind power they think of large-scale wind farms with fields of huge three-bladed horizontal axis turbines. With such farms requiring lots of room they are generally unsuitable for placement in or even near large cities. Smaller turbines tailored for urban environments such as AeroVironment's Architectural Wind System, the Honeywell Wind Turbine and the Windspire represent a growing sector though, and the latest to catch our eye is the IMPLUX - a vertical axis turbine designed to harness the power of the wind blowing from all directions.

The key to the IMPLUX, which was designed by inventor Varan Sureshan, is the omni-directional shroud that forms the outer covering of the turbine and directs the wind from all directions up through the unit to turn an aerofoil propeller rotor like that used on horizontal axis wind turbines. The shroud, which wouldn't look out of place in The Jetsons, consists of a series of fixed horizontal blades that are shaped to capture the wind and accelerate it up into the central chamber to turn the turbine rotor.

To stop the wind simply blowing straight through the shroud, the horizontal blades are angled to direct the wind upwards. Sureshan says the wind entering the bottom-most opening, which has the highest focusing ability, forms a "fluid dynamic gate" - essentially an air curtain - that blocks the wind entering on one side from escaping out the other, instead forcing it up a past the rotor.

Sureshan says his invention is capable of generating the same amount or more electricity than a standard horizontal wind turbine with the same sized rotor, but with reduced noise, maintenance and the ability to harness the power of wind that is continuously and rapidly changing direction and speed. This makes it suitable for the swirling wind patterns usually found on the tops of high-rise buildings within cities.

And because the unit is fixed to the building and the rotor is spinning on a vertical axis, Sureshan says the amount of imbalance forces are almost nil, resulting in very little vibration and noise being transferred to the building on which it is located.

Sureshan says the bigger the IMPLUX is, the more efficient it is and he has modeled the design up to a 30 kW unit that measures about 15 m (49 ft) in diameter using computational fluid dynamic (CFD) analyses. However, a unit of such size would be impractical for most buildings, so to test the technology a prototype unit measuring roughly 4 m (13 ft) in diameter and 4 m high with a rotor of about 2 m (6.5 ft) in diameter has been built that is expected to produce up to a maximum of 2 kW. The prototype is set to be placed atop a high-rise building in a city environment for real world testing in June.

If the tests go as expected, Sureshan says he plans to produce units that are slightly smaller to give the device the best chance of meeting as many council planning permission regulations for placement on existing buildings as possible. These will measure around 3 m x 3 m (9.8 x 9.8 ft) and are expected to produce around 1.5 kW.

Sureshan has been awarded patents for the IMPLUX design and has founded a company, Katru Eco-Energy, to bring the IMPLUX to market. The company is aiming for a mid-2012 date for the first IMPLUX units to roll off the production line with an expected price tag in the area of US$10,000.

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