Not all wind turbines are alike. While the great majority are large steel towers fixed to the ground, a few are shaped like gliders, kites, and blimps, and move around freely.
Take the Buoyant Airborne Turbine (BAT), developed by Altaeros, a four-year-old company in Massachusetts. The BAT is a 60-foot-diameter helium aerostat with a three-blade-rotor spinning inside. It rises 1,000 feet off the ground and sends back power via high-strength tethers. And, it's not nearly as cumbersome as it looks.
Altaeros recently announced a $1.3 million demonstration project in Alaska that will supply power to about a dozen homes. It's also working on deals for remote sites in Australia and Canada, and the company has investment from a group controlled by Ratan Tata, the famed Indian industrialist.
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The BAT is aimed at remote regions where power is more expensive, and where other forms of alternative energy are hard to achieve, co-founder Adam Rein says. That includes parts of Alaska, which currently rely on diesel shipments and aren't suitable for solar (because the sun doesn't shine enough) or conventional wind turbines (because the permafrost won't take deep pilings). "In winter, it's hard to transport diesel to remote villages or industrial sites. Many areas only have road access for a few months a year," Rein explains.
The Alaska project, which is partly funded by the Alaska Energy Authority’s Emerging Energy Technology Fund, will test the viability of the technology and give a sense of costs. Altaeros says the BAT will deliver power at about 18 cents per kilowatt-hour, which is more than most of the country, but still below what some Alaskan communities currently pay. It can also be used as a mobile phone mast, potentially providing another source of revenue.
Floating a turbine at 1,000 feet has its advantages. Wind speeds are two-to-three times higher than nearer to land, and more consistent, Rein says. Also, the turbine can be taken down if winds get too fast, minimizing potential for damage. At wind speeds above 45 MPH, a winch automatically springs into action, bringing the blimp to land.
One drawback is that BAT loses helium pressure, albeit slowly. Rein says it needs topping up every three months or so.
There are a few other contenders trying to float airborne turbines into the market, particularly Makani Power, which was acquired by Google X last year. Others include Ampyx Power, from the Netherlands, and Germany's NTS, which is working on a kite that pulls a small train around a railway.
The technology making up the BAT actually isn't complicated. Blimps have existed for years, which provides lots of test data, and the rotor inside is just like the one on a conventional wind turbine. The main challenge is to reduce weight by using composite materials instead of steel.
Rein admits that Altaeros's concept is less daring than Makani's—which is like a flying jet-wing—but not necessarily in a bad way. "We're taking a more conservative approach, which is taking the most reliable way to lift heavy things into the air and combine it with a conventional wind turbine," he says.