Mr Shepard’s flying generator looks like a cross between a kite and a helicopter. It has four rotors at the points of an H-shaped frame that is tethered to the ground by a long cable. The rotors act like the surface of a kite, providing the lift needed to keep the platform in the air. As they do so, they also turn dynamos that generate electricity. This power is transmitted to the ground through aluminium cables. Should there be a lull in the wind, the dynamos can be used in reverse as electric motors, to keep the generator airborne.Here's another interesting proposal: Meanwhile, Wubbo Ockels of the Delft University of Technology in the Netherlands has been developing another approach to airborne wind generation at lower altitude, with backing from Royal Dutch Shell and Nederlandse Gasunie, a natural-gas company. Dr Ockels’s idea is that a kite (without rotor blades) be launched from a ground station, turning a generator as it rises to an altitude of several hundred metres. When it reaches its full height, it alters its shape to catch less wind, and can thus be reeled back in using much less power than it produced when it was being paid out.
more: http://economist.com/science/tq/displaystory.cfm?story_id=8952080