Building-Integrated Wind a Dubious Technology
Building-integrated wind power is a popular idea, and numerous wind turbines are being marketed for mounting on buildings. But according to an analysis by Environmental Building News, the idea of putting wind turbines on buildings is neither technically nor economically practical.
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Integrating wind turbines into buildings is appealing on a lot of levels, the research suggests, but wind turbulence, problems with noise and vibration, and very challenging economics make successful building-integrated wind very hard to achieve. “I began my research hoping to find that this very popular green strategy made sense,” said Alex Wilson, executive editor of EBN “but the more digging I did, the less feasible the practice seemed.”
While Wilson strongly supports wind energy, he found that turbines small enough to work on buildings are simply too expensive to compete with other, more appropriate renewable energy sources, such as photovoltaics (PV) or larger, tower-mounted wind turbines. “Large, freestanding wind turbines on ridgelines or Midwestern agricultural fields and offshore wind farms provide the most affordable renewable electricity,” according to Wilson. “It’s really hard to make the economics work on buildings.”
While actual performance data is very hard to come by, what data Wilson was able to dig up showed that the performance of most systems is extremely poor. Often, the rated performance of building-integrated wind turbines, especially vertical-axis machines, is based on unrealistically high wind speeds. “A turbine rated at 5 kilowatts in 32 mile-per-hour wind may only produce a few hundred watts in 12 mph wind, which will be much more commonly experienced,” says Wilson.
“The lack of consistent ratings for wind turbines and exaggerated performance claims are big problems,” says Wilson. Indeed, some systems seem more optimized for renewable energy tax credits than for cost-effective power generation. A recent revision to federal law provides a 30 percent credit for small wind turbines, with no cap on the amount of the credit. Wilson’s article points out that while large wind turbines provide the most cost-effective renewable electricity generation, smaller building-integrated wind turbines are usually less cost-effective than building-integrated PV systems. The installed cost of these two systems is often fairly similar, relative to the rated power output, but PV systems have a significantly higher “power factor” (the percentage of time it is operating at the rated output) in most locations, are more reliable, and do not require maintenance.
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