For anyone interested in airborne wind generators it's worth checking out some of the presentations from AWEC2015:
http://awec2015.tudelft.nl/presentations.html
Of particular note is the Makani presentation which gives an overview of their progress to date and shows their 600kW design which they're about to start testing.
The potential of this technology is quite substantial. As are the barriers. Good progress is being made though which is very encouraging.
Airborne Wind Energy Conference 2015 Presentations
Moderator: Peak Moderation