Massive rural wind farms are soaring symbols of America's renewable energy future, but ecoconscious urban dwellers might wonder: How can I get in on the action? After all, the wind roars through downtown concrete canyons, and in many blustery towns, wind is a cheaper renewable source than solar power.
New ways to catch the breeze are in the works. Towering masts and propellers don't always fit in dense metropolitan areas, much less in backyards, so developers are pursuing everything from 'micro windmills' that can be retrofitted onto existing homes and businesses to wind-harnessing 'energy skin' for building exteriors.
In Guangzhou, China, the proposed 69-story Pearl River Tower looks like a United Nations building with two horizontal creases-mechanical floors bent inward to funnel winds through eight interior turbines. At the Lilliputian end of the scale, Arizona-based Southwest Windpower makes a minitower that produces about two-thirds of a home's power and costs about $9,000 with installation. California-based AeroVironment-which designed the GM vehicle canonized in the recent film Who Killed the Electric Car?-will soon sell turbines that resemble box fans and are designed to line the roofs of big-box stores and distribution centers. At least three companies tout a helical design they say better captures capricious urban winds.
There is a reason this breezy dreamscape is still on the verge: The urban environment is less hospitable to wind power. Nearby buildings create turbulence that cuts turbine efficiency, and some turbines cause vibrations that buildings can't handle (as well as noise that neighbors can't stomach). Because of these and other limitations, urban wind power won't be a silver bullet but rather a portion of the energy mix-single-digit percentages, according to most experts.
Still, it's suddenly a hot commodity. Southwest Windpower has sold farmers and sailors small-scale wind generators for 20 years but found a new market when turn-of-the-millennium technology better connected turbines to homes on the power grid. As Southwest prepared to ship its Skystream 3.7 turbines this fall, some customers told company cofounder Andy Kruse, 'I don't care how much it costs, I just want one.'
The Skystream, a three-blade turbine atop a 35-foot pole, produces about 400 kilowatts a month in 12-miles-per-hour average winds (a speed reachable in most of the Midwest, Southwest, and coastal areas). The propellers hum along at under 45 decibels-quiet enough to keep the neighbors happy. The unit requires half an acre of unobstructed land, making it a product only an urban area's sprawl zone can love-but a lot of people live in suburbs and exurbs, and green power generated there bypasses the nation's brittle, maxed-out power grid, where 9.5 percent of power is literally lost in transmission.
The Pearl River Tower's convex skin will funnel winds in a way that produces 15 times the energy of free-standing turbines, claims its architect-engineering designer, Chicago-based Skidmore, Owings and Merrill. The funnel-dappled exterior is Pearl River's sexiest visible feature, but Roger Frechette, the firm's director of mechanical, engineering, and plumbing, says wind is just one of 28 efficiency and renewable strategies and will generate less than 10 percent of the building's power.
Pearl River has its doubters. Paul Gipe, a wind advocate, says the wind power component 'is unlikely to ever be done, and if it's done, it will be removed in one or two years.' He predicts that engineers won't master internal vibration and cost challenges, and he points to Freedom Tower, the 1,776-foot-high World Trade Center replacement that initially included wind power, which was later removed. That building was also designed by Skidmore, Owings and Merrill.
Such turbulence may represent growing pains rather than snake oil. 'Many states offer incentives for solar or small wind,' notes Southwest Windpower's Kruse, 'but before you qualify, you have to go through rigorous testing by a third party saying this product is going to work.'
Gipe sees more potential in smaller-scale urban wind farms that have already sprung up within municipal borders. Atlantic City debuted a five-tower complex this year. Just up the coast from Cape Cod's controversial 'Cape Wind' project, the 11,000-person Boston suburb of Hull, Massachusetts, gets 13 percent of its electricity from two towers and will be 100 percent wind-powered after four more are built.
Grabbing urban wind may be less about flashy innovation than about applying concepts proven elsewhere, Gipe says. 'Just like Europe has done for 20 years,' he notes, 'American harbors and piers should be covered in wind turbines.'