A Californian company, Makani Power, which was originally funded by Google and now by the U.S. Department of Energy’s ARPA-E agency, is developing an airborne wind turbine.

The Makani Airborne Wind Turbine is a tethered wing fitted with turbines which flies at between 250 and 600 metres where the wind is stronger and more consistent. Air moving across the turbine blades forces them to rotate, driving a generator to produce electricity.

In a conventional wind turbine blade, the tip is the most effective part and is responsible for most of the energy produced. By flying in circles across the wind at 240 kilometres an hour, the entire wing acts like the tip of a traditional turbine blade.

Makani is nearing the end of the first phase of its development program. All flight modes of the AWT have been demonstrated by a 30 kilowatt prototype. Makani will next develop a 600 kilowatt AWT, for utility scale power generation which the company expects will be at a cost below conventional solar and wind.

In this video, the AWT can be seen launching from a perch, reeling out in hover mode, autonomously transitioning from hover into crosswind flight, flying crosswind to generate power and transitioning out of crosswind back into hover before it finally comes to rest on a perch again.