Thursday, June 03, 2010

"Go Fly A Kite" Takes On New Meaning

Example of an AWE blimp

Wind turbine kites have taken to the skies as a form of Alternative Energy. Inventor JoeBen Bevirt of Joby Energy is mounting a test for a series of large kites that are designed to "harvest" high winds found at high altitudes. Airborne Wind Turbines are part of a wider Alternative Energy Sector known as Airborne Wind Energy Systems (AWE).

The Bevirt airborne wind turbines will fly to around 2000 feet (600m), where they will float, generating power that can be transferred to the ground via a tether.

"Global wind is a tremendous source of energy - carrying nearly 870 terrawatts in global tropospheric winds," says Bevirt. "In comparison, the global demand is 17 terawatts. Harnessing a tiny fraction will transform the way we power our civilization."

As of 2010 no commecially viable kite farms are in operation, but the concepts involved have been contemplated since the 1970s, but was not technically possible. Advances in materials, computing resources and unmanned aerial vehicles have brought the concept closer to reality. As a result, several companies are exploring harvesting wind power at high altitudes.

Magenn Power's Air Rotor System called (MARS) uses a helium filled blimp design. Sky WindPower is building flying electric generators. Kite Gen is focused on creating power kites.

Joby Energy's technology is based upon a large multi-winged kite, similar to a World War I multiwing airplane. Each kite is computer-controlled and can guided remotely to a desired altitude. Flight is controlled by its onboard computer system and harvested electricity is sent down a tether to a substation where it is converted from DC to AC power.

There are risks and limitations to contemplated AWE systems. Kites and 'helicopter' designs must be grounded when there is insufficient wind. Kytoons and blimps could allow fixed positioning. However, bad weather such as lightning or thunderstorms, could temporarily suspend use of the machines, probably requiring them to be brought back down to the ground and covered. Some schemes require a long power cable and, if the turbine is high enough, an aircraft exclusion zone. When the generator is ground-based, the tether need not be conductive.

Sky Windpower estimates that this technology will be capable of producing electricity for $0.02 per KWh, while a system of raising a kite to a high altitude while turning a generator on the ground, and then changing its shape so that it can be drawn back down with less energy than it produced on the way up, has been estimated to be capable of producing electricity for $0.01 per KWh - both numbers being significantly lower than the current price of non-subsidized electricity.

Richard Wottrich

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