https://en.wikipedia.org/wiki/Autorotation
Similar ideas have been suggested using balloons:
http://latesttechnology-world.blogspot.com/2013/07/magenn-ai...
https://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=134023
https://en.wikipedia.org/wiki/Airborne_wind_turbine
An array of wind-powered drones could scale well beyond what's possible with a traditional wind turbine, since most of the torque gets applied at the wingtips. There might be advantages with inconsistent wind gusts too, since the rotor could wind up in strong wind and unwind in weak wind. Startup costs would be negligible since a few drones could start the rotor and more could be added as needed. It might even by safer for birds if a drone array turns slower than a fixed rotor.