Researchers claim that high-altitude kites could generate wind energy

High-altitude kites could be used to generate clean energy at a cost comparable with that of polluting power stations, researchers claim. The “Laddermill” is a chain of controllable wing-like kites attached to a looped cable stretching more than five miles into the sky. Strong high altitude winds acting on the “kitewings” produce as upward force on one side of the loop and a downward force on the other, causing it to rotate. The slowly-turning cable drives a power generator in the Laddermill base station. Although the concept sounds far fetched, its developers at Delft Technical University in the Netherlands hope to build a working model in the next four years. They claim one Laddermill could generate 100 megawatts of electricity, compared with only a few megawatts from a conventional wind turbine. Team leader Professor Wubbo Ockels (correct) was inspired by making and flying powerful high-flying kites as a boy.

Winds at 30,000ft are 20 times more powerful than at sea level. Professor Ockels, an ex-astronaut and head of the European Space Agency’s education office, told The Engineer magazine: “Above a certain altitude there is a massive amount of wind power. “Kites that can tap into that wind can generate a great deal of energy.” At last month’s European Wind Energy Conference in London, the Laddermill team announced plans to test a variety of kiteplane designs next year using inflatable and lightweight materials. They maintain that despite its size, the structure would be safe.

“If the wind dropped the Laddermill would drift gently to the ground,” said Professor Ockels. “We want to be safe. Flexible or inflatable kites wouldn’t be hazardous; the worst that would happen would be the kite becoming dirty when it landed. “We would only operate the system with a good forecast and the wings would be adapted to weather patterns.” Each wing would be automatically controlled by changing shape or using small propellers to alter position. The Laddermill would only be flown where aircraft are banned. One such area is the zone along the US-Mexican border, where high-flying balloons fitted with radar are used to combat drug traffickers. Professor Ockels says a few hundred of the installations, each requiring some 400 kites with 27ft wingspans, could generate enough electricity to supply the needs of a city the size of Seattle. The cost would be similar to that of generating power with polluting fossil fuels.

But the technology was questioned by Scott Skinner, president of the Drachen Foundation which promotes knowledge about kites worldwide. He said: “As a kiteflier I have learned that what can go wrong will go wrong. I wonder about what happens if the line breaks. It appears the assumption made is that the kites will still fly in an upright and stable position. What if they, for example, turn 180 degrees to the wind and fly downwind and actually accelerate in speed to the ground?”