2012-06-28

Wind Power From A Flying Jet Wing

What’s that in the sky? It’s a giant flying device (part kite, part plane) that’s creating power from gusts high in the air. And it may be the future of wind power.

Although wind power has come a long way in the last few years, today’s turbines certainly have their critics. And not all of them come from nuclear or oil industries. Even enthusiasts for wind believe conventional turbines are cumbersome, expensive, and difficult to install and maintain. Or that they ruin the view.

Corwin Hardham is trying to build a different type of turbine. The CEO of a California start-up called Makani has a prototype that, instead of being fixed to the ground, rotates in the air. The wing, which is about the length of a single conventional wind blade, generates power from rotors along its span. Hardham says his design is not only cheaper to make and maintain, it also generates more power than a standard turbine—partly because wind is more plentiful at 600 feet than at 200.

Makani’s idea is to use some of the basic mechanics of a kite, with the control of a modern aircraft. Hardham is very keen to point out that his machine is not some flimsy textile-made thing you might take to the park, and see crash to the ground. The tethered wing, he says, has the sophistication of a jet plane, where automation takes care of most problems.

"It’s important to recognize that what we’re doing is similar to what’s been done in other applications," he says. "Passenger jets are autonomously controlled. The pilot has little to do, particularly during takeoff and landing. We’re already surrounded by a lot of automation, and it’s automation that makes our system possible."

Though Hardham points out lots of differences from conventional turbines, he points to one similarity. On fixed machines, the blades are calibrated so they never spin too fast. Similarly, the Makani turbine is controlled by a computer unit that shifts the wing’s course if the wind stops blowing, or if it changes direction dramatically. When the machine is looping normally, power goes down the tether. But, if necessary, power can be shifted up to the rotors, which can thrust the wing back into place.

Hardham estimates the wing uses 10% of the materials of a conventional turbine, making it easier and cheaper to construct and install, and quicker to build out in numbers. He says the Makani will generate unsubsidized onshore power at 3 to 6 cents per kilowatt hour, compared to 5 to 10 cents for today’s fixed turbines. Offshore, he says it will be more like 5 to 6 cents against 20 cents. (See here for more comparisons).

He also points out his turbines are not so dependent on terrain. While fixed machines have to be stationed in very specific locations—on top of a hill, say—the Makani wing can be hoisted wherever it is needed, as long as there is sufficient space for the loop.

With funding from Google and the Department of Energy’s Arpa-E, Makani has credibility. But, as ever, the road to commercialization is likely to be difficult. Hardham says it will be four years before the prototype becomes a utility-scale commercial product. Still, he’s convinced the economics will eventually make the idea tenable. Several developers and independent power producers have already expressed interest in buying the finished article, he says.

"One of the interesting aspects of this technology is you can go to places where the resources aren’t good enough to justify the economics of [conventional turbines]. We solve a lot of those issues. So that’s why they are interested in talking with us."

Just don’t call it a kite.

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1 Comments

  • riff_raff99

    While it's always nice to see people being creative, with commercial wind energy it's all about cost of energy.  And I haven't seen anything that would justify Makani's claims of lower coe.  Modern commercial wind turbines are incredibly robust and reliable devices that operate unattended for year after year. I can't imagine a tethered composite aircraft ever being able to do the same.

    As for energy capture, even though the Makani turbine is operating at a few thousand feet above ground level where winds tend to be higher velocity, the small diameter high-speed propellors will be far less efficient at capturing the available wind energy than a massive slow turning conventional HAWT rotor.