High altitude wind plants to tap enormous energy resources

By Eckart Gienke Oct 6, 2011, 10:31 GMT

Hamburg - Scientists are thinking up new ways of addressing the world's ever-increasing energy needs ecologically, with high-altitude winds possibly replacing wind generation plants in the future.

Kites, sails, gliders, balloons or Zeppelins can all harness wind energy at altitudes of up to two kilometres.

Some researchers are even mulling the possibility of tapping into energy created by the jet stream in the upper stratosphere at an altitude of five to 10 kilometres.

There are currently more than 20 companies working in the burgeoning high altitude wind energy sector, using different technical concepts on various levels of development, according to the wind energy consultant GL Garrad Hassan.

None of the firms are in a position to present a product ready to go into production, but the potential from high altitude winds is believed to be huge.

'There is enough energy there to meet the needs of civilization a hundred times over,' says professor Ken Caldeira from Stanford University in California.

SkySails, a German company, has already invested 50 million euros (68 million dollars) in a marketable towing kite propulsion system for cargo ships.

'We are the only firm worldwide that is in a position today to offer industrial products that use high-altitude winds,' SkySails CEO Stephan Wrage says.

The amount of research necessary to make progress in the area is generally underestimated. SkySails, for example, has registered 300 patents for its kite propulsion system alone.

The first attempt at energy generation from a kite with a 400-square-metre surface is expected to be complete by 2013.

The system consists of a free-flying kite with rope that can operate at heights between 200 and 800 metres, a launch and recovery system, an automated control system, a generator for producing electrical power and a support platform.

Energy can be produced 24 hours a day, 365 days a year, with the prototype's performance estimated at approximately one megawatt. SkySails expects the finished product to be capable of producing 3.5 megawatts within two or three years.

A large wind turbine produces around six megawatts, but the kite system is cheaper as well as easier to install and maintain, lowering the cost of each electrical unit by 30 per cent.

Wrage envisages wind farms with 100 or more kites. The system has the added advantage of being able to be installed on both conventional offshore foundations and on floating platforms.

It can also be secured far out at sea at water depths of up to 700 metres using established anchoring technologies.

SkySails is currently working on a small kite with a surface area of 20 square metres.

Yet the company and fellow pioneers, such as the US firm Makani or Dutch professor Wubbo Ockels from Delft University, still need overcome many obstacles.

The early prototypes have generated too little energy - just a few kilowatts - while there is also the question of who takes in the kites when a storm threatens.

Other issues also need to be resolved - such as rain, ice, lightning, and the potential danger to air traffic.

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