A wind turbine energy conversion device that can take advantage of the higher speed and more persistent winds at higher altitudes is hereinafter disclosed. The wind turbine energy conversion device includes an unmanned aerial vehicle (UAV) connected to one end of a tether (which may include multiple shorter tethers), the other end being connected to a terrestrial anchorage point. The UAV flies at altitudes where wind speeds can reach 40 mph or higher. The UAV comprises a flying wing with one or more trailing wind power turbines and flies airborne maneuvers designed to increase relative wind speed up to about four times the true wind speed.