Tethered UAV's Tap High Winds for Power

Altaeros Energies' BAT uses helium gas to take the turbine
hundreds of metres into the sky

BBC News - Wind turbines take to the skies to seek out more power
US-based Altaeros Energies uses a helium-filled shell within which sits a traditional but lightweight turbine. It can be raised or lowered to seek out the optimal wind speed and is attached to the ground by three tethers, one of which transmits the power generated back to earth. The company says the design produces two to three times the power output of standard turbine, with installation and transport costs 90% lower.

Canada's LTA Windpower is developing a similar concept, but using an airship designed to contain hydrogen.

Makani's radical design uses a tethered "kite"
to fly up high to catch strong winds

Google X 'moonshots lab' buys flying wind turbine company Makani Power | The Verge
The notoriously secretive Google X is also getting in on the act, having bought wind power company Makani in 2013. Its solution involves a tethered, carbon fibre glider flying in circles at an altitude of up to 350m, carrying up to 8 small turbines producing 600KW of power. Makani claims each glider can generate 50% more energy than a traditional, fixed turbine.



With variability one of the key drawbacks of wind power, the logic of going higher is indisputable. But Jan Matthieson at the UK's Carbon Trust argues there are "a lot of questions and a lot of risks with airborne power".
"A lot more work and testing needs to be done for these companies to build up a track record, and with very high [development] costs it will be difficult for new technologies to break into the market."
He believes it will be at least 10 years before flying turbines reach widespread commercialisation.