Wind blows stronger and more consistently as you rise above ground obstacles like buildings, trees, and hills. This makes for a lucrative green energy source—assuming you can lift generators 1000 feet in the air. This Airborne Wind Turbine could well become the first.

Altaeros Energies is currently developing the Airborne Wind Turbine (AWT). It consists of a cylindrical series of helium-filled bladders that surround a central turbine. The AWT's shape ensures that it consistently faces the wind and the entire assembly is anchored to the ground via an electrically-conductive tether. Since the AWT doesn't rely on propellers or mechanical processes to stay aloft, it can remain in the air for much longer and at a greatly reduced cost.

Altaeros has successfully tested a 35-foot scale prototype in Limestone, Maine, in which the aereostat autonomously climbed to 350 feet. Using its Southwest Skystream turbine, it produced twice as much power at altitude as it did at ground level, and then landed.

The company hopes to scale up the platform to reach altitudes of over 1000 feet, where wind speeds are five times faster than on the ground and can generate over 20 times the power. (Each time wind speed doubles, the amount of energy it theoretically holds increases eight-fold.) If it works, Altaeros believes it can cut the cost of energy production by 65 per cent. "For decades, wind turbines have required cranes and huge towers to lift a few hundred feet off the ground where winds can be slow and gusty," explained Ben Glass, the inventor of the AWT and Altaeros Chief Executive Officer. "We are excited to demonstrate that modern inflatable materials can lift wind turbines into more powerful winds almost everywhere."

The downside to the AWT, however, is that it relies on helium for its lift, and helium is becoming increasingly scarce. If the price of this element continues to rise, it could offset any savings gained by lifting the turbines in the first place. [Wired.UK - Altaeros - ABC News - Nomada - AWT Wiki - Southwest Windpower]