Airborne Wind Energy Technology Can Fly Like a Kite

Posted by Sarah Laskow

kite
Makani Power’s Wing 7 wind energy generator looks like it comes from a Miyazaki movie. It resembles one of the Wright Brothers’ earliest planes, but when it takes off, it rises vertically into the sky, then begins swooping and climbing in a circle. As it flies, the Wing 7 harvests the energy of higher-speed winds that grounded, conventional wind turbines can't reach. It’s attached to the earth by a tether, which brings the power that it’s generating back to the ground. 

Makani just won a Breakthrough Award from Popular Mechanics, but it’s not the only company that’s exploring airborne wind technologies. It’s one of five “gold members” of the Airborne Wind Energy Consortium, some of which are seeking to create airborne wind technology that can generate a megawatt or more of power within a year or two. 

The power generated by wind turbines is proportional to the cube of the wind’s speed, so faster wind generates exponentially more power. The fastest winds are the hardest to reach: they’re out at sea, where the water is too deep to anchor wind turbines on the ocean floor, or high up in the atmosphere. Conventional wind turbines have been growing bigger in order to reach the faster winds, but there are limits to how high they can climb. 

Airborne wind energy technology promises to reach winds more than 1,000 feet above the earth’s surface, where winds are not only faster, but more reliable. For offshore wind farms, airborne technology might make more sense than large floating turbines that have to contend more directly with unbalancing waves. Airborne turbines, which are smaller and contain less material than conventional ones, also have smaller initial carbon footprints. 

Questions about the technology remain. The energy-generating components, usually called kites or wings, have to stay up in the air for long periods of time and either deal with harsh weather or land return to Earth when a bad storm comes by. But both the government and the private have already shown interest in these ideas. Makani received $3 million in funding from the Advanced Research Projects Agency-Energy in 2010, and millions more from Google’s investment arm.

Large aerospace companies have also shown interest in the technology: Honeywell, a defense contractor, recently designed an airborne wind prototype with a body design inspired by unmaned military drones. One company, Windlift, is designing its technology for more mobile use by the military or disaster relief organizations. 

The idea of using wind energy from higher in the sky is hardly new: Makani advisor Miles Loyd first wrote about it in the 1970s, for the Lawrence Livermore National Laboratory. It’s long been apparent that the strongest, most consistent winds are in the upper reaches of the sky. Soon we might be able to fly up and catch hold of them. 

Photo via (cc) Flickr user CafeYak.com