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comment Building-Integrated Wind Power a Dubious Technology
Rooftops are elevated above ground, where it’s windier, creating the potential for electricity to be generated from wind, and then used right where it’s needed. Wind energy can make a strong visual statement about environmental priorities. But is building-integrated wind a good idea?
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Wind speed typically increases with height. Putting wind turbines on top of buildings should allow them to take advantage of height without an expensive, full-size tower. Building geometry can enhance wind turbine performance, by accelerating wind as it curls over the parapet or by funneling air flow toward turbines. Most of our electricity is used in buildings, and generating the electricity on site reduces the need for transmission, with its losses and infrastructure costs. In addition to this practical benefit, wind turbines spinning on a building provide a visible testament to a building owner’s commitment to the environment.
Unfortunately, building-integrated wind often doesn’t live up to its promise. On top of even very tall buildings, wind flow is highly turbulent, while turbines need a strong laminar flow to work well. The increased wind velocity at building parapets can only be successfully harvested in a fairly narrow band, which limits the potential size and output of wind turbines. Because the turbines are small, the economics are not as attractive as with larger wind turbines. Noise and vibration from wind turbines are stubborn problems that are among the greatest obstacles to integrating them into buildings. It is not unheard of for large, free-standing wind turbines to occasionally shed a blade. Even if the building owner is willing to accept that risk, an insurance company may not be.
Perhaps the greatest impediment to building-integrated wind energy is the economics. While large free-standing wind turbines provide the least expensive renewable electricity today, small wind turbines are far less cost effective, and when small turbines are put on buildings, the costs go up while the production drops.
Putting wind turbines on a building to advertise the greenness of a company or organization is a compelling idea—as long as those turbines spin most of the time. Unfortunately, many turbines mounted on buildings frequently lack strong enough wind to operate.
Commuters who glance up at stationary turbines may conclude that wind energy doesn’t work very well.
There’s a wonderful synergy in the idea of combining form and function by generating electricity with turbines that reach into the sky on the buildings they will help to power. But in most cases, at least with today’s technology, it just doesn’t make sense.
Copyright 2009 by BuildingGreen, LLC
