Making a kite generate electric energy is an option, but the Makani team found that this is certainly no easy feat, as can be seen in this 
. The kite needs to first gain altitude, then be controlled in such a way that it circles the sky without crashing into the ground.
Upon ending the cycle, it needs to go from circling back to landing mode, and then be reeled in. All in all, the software has to take into account a lot of variables, and the team actually went over numerous iterations and several prototypes to work it all out.
It is hoped this is not wasted in the end, but after the sea trials the funding dried up, so the project eventually ended there...