A NASA aerospace engineer is working to shift wind turbines out of peoples' backyards - and into the sky.
"At 2,000 feet, there is two to three times the wind velocity compared to ground level," says Mark Moore. "The power goes up with the cube of that wind velocity, so it's eight to 27 times the power production just by getting 2,000 feet up, and the wind velocity is more consistent."
Get the turbines right up into the jet stream at 30,000 feet, and it's possible to harvest 20,000 to 40,000 watts per square meter, compared with 500 for ground-based wind turbines.
With the help of a $100,000 US government grant, Moore is researching different designs. These include a funnel-shaped blimp with a turbine at its back, a balloon with vanes that rotate, a truss-braced wing and even a parachute and a kite. Power would be conducted back to the ground via a nanotube tether.
"They could stay up a year, then come down for a maintenance check and then go back up," he says. "Or they could be reeled in in case of a storm. One operator could watch over 100 of these."
The best location for such devices, says Moore, would be over the sea. "Unlike ground-based turbines, there is almost no additional cost for airborne systems offshore because huge platforms are not required to support the structure or resist large tower bending moments," he says.
It would also have the advantage of preventing Nimbys from complaining about giant shadows.
But there's another, more important reason. While airborne wind power generation makes much more sense technically than ground-based systems, there's the commercial angle to consider.
Airspace is a precious resource, carefully guarded by the Federal Aviation Authority (FAA) and governed by a string of elaborate regulations.
"Offshore deployment of these airborne systems probably makes the most sense in terms of both airspace and land use, because there is little to no demand for low altitude flight over oceans 12 miles offshore," says Moore.