The paper below can be a start for this discussion.
https://hal.archives-ouvertes.fr/hal-00873243/document
@kitefreak just provided interesting data about some possibilities to keep kites in the air by no wind. His message is not more available. So he is invited to post them here if he wants. Thanks.
Yep interesting indeed
Rogelio Lozano; Jonathan Dumon; Ahmad Hably
Gipsa-lab, Grenoble, France
Date of Conference: 11-13 October 2013
The same publication (and also in regard to the initial post), in open archive “HAL”:
Step towing - used to launch (para, hang)gliders without wind or hills, should also allow a kite to float indefinitely at altitudes up to 1km.
Such a technology has more business opportunities than holding a wind power kite in the air - like area surveillance, medium range radio relays.
A cable powered drone floating a couple kg payload at just 50m is quite expensive.