Inflatable wind turbines that will float thousands of feet in the air could be the key to sustainable energy in the future, developers claim.

The helium filled 'buoyant air turbine' (BAT) is designed to harness energy from the strong wind currents higher up in the sky, transmitting it down cables attached to tethering ties. The tethers can automatically adjust the height of the turbine to catch the strongest winds.

US green energy company Altaeros Energies, which has developed the prototypes, believe the new turbines have the capability to reduce energy prices in remote locations and developing countries.

"The reason high altitude winds are so exciting and worth going after is really very simple: there's just a lot more of it," explained Ben Glass, CEO of Altaeros Energies. "Winds 1,000 to 2,000 ft above the ground are on average five to eight times more powerful than what you get on the ground."

Wind farms have long been a point of contention in the UK, with many believing current 'static' wind farms are uneconomic, low-yield, and blight the countryside.