An early prototype 10-kW Makani Windpower system consisted of two 5-kW wind turbines mounted on a wing that flies in somewhat vertical circles (like a kite) several hundred meters above ground. A tether attached to the "kite" carries power from the turbines down to the ground. Since the speed of the kite-turbines moving through the air is much faster than the wind speed, much smaller turbine blades can be used than those on conventional ground-mounted wind turbines. Also with no need for a tower, the cost of materials is far lower than for a conventional system. https://www.youtube.com/watch?v=YjxkHpN8Z5Q https://www.youtube.com/watch?v=gLy13wicins 5 kW per turbine wing + 50 m/s ac wind orbit Tether DC/AC Power 400m Suppose each wing/turbine is moving through the air at 50 m/s and suppose the overall efficiency is half that of the Betz limit, what blade diameter would be required to deliver 5 kW of power per turbine. Don't bother to correct air density for this altitude.