To be clear: crosswind kite power does work. The question is whether it is economical or competitive.

The paper that started it all is this one by Miles Loyd from 1980. It's short enough it could fit on the back of a large envelope. :-)

http://edge.rit.edu/edge/P15462/public/CAD/crosswind_kite.pd...

In the film they explain that since wind turbines extract power based on the area they sweep, their kite would be able to sweep a bigger area more easily. (No need for so much material, no need for a 150m tall tower, etc.)

https://www.youtube.com/watch?v=qd_hEja6bzE&t=6m40s