The Economist has an interesting article about different proposals to harvest wind energy from the jet stream (elevation: 10km). A San Diego, CA company called Sky WindPower wants to send giant kite-turbines into the jet stream to generate power.

“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.”