Power Kite
These guys want to generate power at high altitude and transmit the electricity to the ground. I think it is silly because they keep heavy generators at high altitude while needing power cables to bring the electricity down to the ground. Why not use the tether as a method to transmit energy to the ground.
Description
In response to this Slashdot article I decided to draw up the design below
The power station kite uses the rotor power to stay airborne. Essentially that is a regular autogyro. Excess power beyond what is required to stay airborne is applied to a winch that the powerstation kite uses to reel itself in. In the mean time the generator rotates thus feeding cable via a gearbox and a winch to the power station kite. The cable tension between the power station and the generator drum is used as a control input that controls the load placed on the generator.
So the Powerstation is pulling in cable at the same rate as the generator let's out cable and thus the pawerstation kite remains stationary. There is a tradeoff between tether movement speed and force. The tether could move slowly with a large force (which requires a heavier cable) or faster with a lesser force and thus a lighter cable.
A fast cable locking mechanism can lock the "Up" and "Down" cable at both ends if the cable tension suddenly reduces such as would happen in the event of a cable failure.
Below a 3D model you can view in Google Sketchup click on the image for more.