A recent study commissioned by the Massachusetts Renewable Energy Trust found that the electricity output from the 21 small wind turbines in the state was only about one-third of the manufacturers’ estimates. The results seemed to agree with those of the U.K.’s Warwick Wind Trials which found that urban microwind performance varied widely depending on wind conditions, siting and height of the installation.
Basic conclusions are that optimal electricity production occurs when the turbine is mounted at least 30 to 40′ above the nearest obstruction, in an open, flat space, with steady winds at, or above, 10mph. Roof mounted systems often suffered from associated vibrations and noise. The Warwick study found that turbines mounted on high rise structures could produce as much energy in one month as lower mounted installations could in one year. Unfortunately the high rise turbines needed to be shut off for much of the time during the trials due to noise complaints by residents.
The Massachusetts study found that area wind maps could overestimate average wind speeds by as much as 10%, and that adjacent structures and obstructions, such as trees, could have a disproportionate negative impact on turbine performance.
All in all, the microwind industry is still in its infancy. Though a 30% federal tax credit will help increase home owners enthusiasm for microwind, local zoning (not in my backyard) and performance issues may slow installation.
Ultimately, product innovation, proper siting and realistic power production estimates can still make microwind a viable component of a home or building’s alternative energy menu.
additional source: cnet
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