The KiteGen airfoil prototype dangles above its housing, with its high-tension wires reeled in. The start-up company is based in Chieri, Italy, near Torino.
KiteGen builds on some earlier prototypes and theoretical ideas. In the 1980s, Bryan Roberts, an engineering professor at the University of Technology in Sydney, Australia, tested a small prototype of a helicopter-like airborne turbine that he hoped would eventually fly to 15,000 feet (4,600 meters), where it would float on the strong winds and send energy down a very long tether. Roberts' idea lives on in his Oroville, California-based spin-off company Sky WindPower, which claims to be working on a Flying Generator.
Since the 1970s, airborne wind designers have toyed with a concept called the Laddermill, which is made up of a loop or loops of kites deployed at high altitude. By varying the "attack angles" of the kites, operators can theoretically get them to dive or soar, or fly in endless circles, all to transmit energy to the ground.
Dutch astronaut and physicist Wubbo Ockels published a 4-kW version of a Laddermill in 2007. In this proposal, a loop of kites would be lofted at a height of 0.62 mile (one kilometer). As the kites climbed, they would unspool a tether around a drum, which would drive a generator. When the line ran out, they would be angled to dive, and the slack line would be recovered-and then the kites would be sent back up for another cycle. According to the published proceeding in European Power and Energy Systems, Ockels' team successfully tested a 2-kW (a typical U.S. household routinely draws about 2 kW, not counting air-conditioning).
In a somewhat similar concept, the Italian start-up Twind Technology is working on a device made of two tethered balloons, each with an inflatable sail. The sails are alternately filled and stowed, to make the pair swing back and forth. The resultant motion of their tether can be used to saw wood or drive an engine, according to the company.
Read more
