Rooftop turbines: Is "small wind" really worth it?

News and commentary about environmental issues.
Feb. 12 2011 6:49 AM

Rooftop Pipe-Dream

Be wary of the booming market for pint-sized, roof-mounted windmills.

Co-operative Insurance building with wind turbines on roof. Click image to expand.
Roofttop wind turbines

"Small wind" is getting big. The market for these pint-sized windmills grew 13 percent in the United States in 2009, the latest year for which figures are available, to $82.4 million. With that boost, the total capacity of small turbines in the U.S. now exceeds 100 megawatts. That accounts for 3 percent of wind energy here, which might not seem like much, but over half that capacity has been built in just the last three years. Another sign of the turbines' increasing popularity: Last month, small-wind units appeared at the Consumer Electronics Show in Las Vegas for the first time.

Small tower turbines have been stippling Midwest horizons for at least 80 years. Interchangeably called "small wind" and "residential wind," the category covers tower- and roof-mounted turbines with the capacity to generate anywhere below 100 kilowatts of energy. (Most occupy a range of 3 kilowatts to 20 kilowatts; by comparison, the average residential solar system has a capacity of 3 kilowatts to 10 kilowatts.) They're usually used to help power a home, a farm, or, in some cases, a corporate campus. The modern small-wind craze, however, traces back to October 2008, when Congress expanded tax credits for the turbines—first as part of the Emergency Economic Stabilization Act and later as part of the American Recovery and Reinvestment Act. The laws allow consumers to write off 30 percent of the total purchasing and installation costs of any small-wind turbine—tax credits that had been previously capped at $2,000. 

A booming market in renewable energy sounds great, but here's the rub: Only the tower-mounted turbines, suitable for homes with an acre or more of land, have really been proven to work. Rooftop turbines, on the other hand, only work in very specific settings, and almost never in urban areas—precisely where many consumers seem keen on putting them.

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For a turbine to generate enough power to be of any use, it needs to be consistently hit with wind at speeds above 5 miles per hour. In cities, there are just too many physical obstacles—cell phone towers, skyscrapers, apartment buildings—in the way. "It's like putting a solar panel under a tree or in the shade," says Ron Stimmel, AWEA's small-wind expert from 2006 to 2010, now an MBA student at Columbia. To boot, most roofs are simply too weak to support rooftop turbines, which create additional drag and can cause vibrations that range from annoying to potentially dangerous.

The stimulus package also threw millions of dollars at small-wind manufacturers, some deserving of it and others not so much. In 2008 and 2009, dozens of companies launched new turbines aimed at urban and rural consumers alike, hoping to cash in on the craze. "Everyone who had been tinkering around with a turbine in their garage came out of the woodwork," says Trudy Forsyth, small-wind expert at NREL, the government's primary R&D lab for renewable energy.

That meant a surge of tower and rooftop turbines on the market, and a whole bunch of new consumers who had no idea about what sort of turbine might work for their home. For many, the allure of a windmill on the roof, powering the fridge and the lights, was strong. Quickly, rooftop turbines became the poster children for small wind. The media helped to feed the hype machine: Many articles about small wind in the last two years have run alongside photos of roof-mounted turbines; after all, they look much cooler and more modern than tower-mounted windmills on big plots of land. The small-wind industry has been complicit, as well, letting the disparity between hype and reality slide. Now, however, manufacturers find themselves needing to educate consumers quickly or risk turning them off altogether.  The fear is that if rooftop wind proliferates, it won't be long until people start complaining about broken turbines, and the same magazines and Web sites that were thrilled with rooftop wind last year will be lambasting it next year.

Take, for instance, the Philadelphia Eagles' plan to install 80 rooftop turbines atop their stadium, a move that garnered much applause when announced in November. Given the stadium's proximity to other large venues, it's hard to imagine those turbines getting the consistent, unobstructed wind they need. The turbines may look cool and green in an artist's rendering, but if people notice that they never seem to be moving, it won't necessarily be a great advertisement for small wind. Good thing the Eagles hedged their bets with 2,500 solar panels.

To mitigate any backlash, AWEA has partnered with manufacturers and installers to encourage self-regulation of both the products and their installation. The Small Wind Certification Council has worked with AWEA to devise tests and standards for small wind units. Certified turbines, which are due to hit the market beginning this June (PDF), will come with guarantees that they will produce a given amount of power and not be overly noisy—provided they're installed correctly and in an appropriate setting. To this end, the North American Board of Certified Energy Practitioners, the same organization that certifies rooftop solar installers, has begun certifying individual small wind installers, who are supposed to have the expert knowledge and professional ethics not to install a turbine where it won't work.

This self-regulation won't prevent a rogue handyman from installing uncertified windmills on your neighbors' rooftops, or stop companies from promoting them. But certification might help in other ways. Local governments have already announced their intentions to require certified turbines for any small-wind tax break—no policymaker wants to spend taxpayer dollars on renewable energy projects that produce diddly-squat.

It'd be a shame if faulty rooftop wind projects cut short the small-wind industry's growth spurt.  Thirteen million homes in the U.S.—11 percent of the country's residences—are still suitable for tower-mounted (not rooftop) turbines, according to AWEA. (Reputable installers will happily evaluate your home for its wind potential.) Even worse is the prospect of sloppy rooftop installations cutting short the development of better, safer rooftop turbines, a goal at least 17 companies and half a dozen research labs are working toward. Small wind won't solve our dependence on fossil fuels, but it could make a big dent in the country's renewable-energy needs.

Amy Westervelt is a freelance environmental reporter based in Oakland, Calif.

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