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<br />For a 10kW residential-scale turbine <br /> <br />$U76 or 226% <br />2.4% <br />100 10.7 9,338 $51,346 $2681 or 344% <br />5.5% <br />* = Return on Investment Mick Sagrillo, AWEA Windletter, January 2006 <br /> <br />226%.;. 2.4% <br />= 94 to 1 ROI <br />344%.;. 5.5% <br />= 63 to 1 ROI <br /> <br /> <br /> <br />. Overly conservative zoning height <br />restrictions therefore cost the owner <br />money - and a lot of it. They can also <br />mean more sound, since taller tower? <br />raise the generator high above the <br />grou nd, diluting sOUlld. considera bly. <br />Sound decreases four-fold with every <br />doubling of distance from the turbine <br />(including distance above the ground) so <br />taller towers are better for their owners as ' <br /> <br />well as neighbors. (See also "Soundll p. 11.) <br /> <br />Mariah Power Windspire <br />lkW turbine <br /> <br />For zoning officials, the importance <br />of strong winds also means that tower <br />height cannot be compromised as a <br />gesture to neighbors concerned about <br />the visibility of the turbine. "Hiding" a <br />turbine from neighbors using a shorter <br />tower almost always means hiding it <br />from the wind, too. <br /> <br /> <br />Power from the Wind <br /> <br />900% <br />800% <br />700% <br />600% <br />500% <br />400% <br />300% <br />200% <br />100% <br /> <br /> <br />0% <br /> <br />o Wind Speed Increase _ Power Increase <br /> <br />Bergey WindPower <br />lOkW XLS turbine <br /> <br />Nor do two shorter installations make an <br />acceptaple substitute for a single, taller <br />one. A tower alone can comprise 50% or <br />more.of a system's total cost, so multiple, <br />shorter turbines (on multiple towers) cost <br />the owner far more than a single, taller <br />system. (See alSo "Multiple Turbines," p. 14.) <br /> <br />It is also important to keep in mind <br />that a turbine's generator size <br />(generating capacity, measured in <br />kilowatts or kW) has little, jf anything, <br />to do with its tower height. Sometimes <br />zoning regulations mistakenly limit <br />tower heights based on the size of <br />the turbine's capacity, thinking that <br /> <br />a 2kW turbine, for example, always <br />corresponds to a 40 foot tower. This is <br />not the case. Appropriate tower height <br />is matched to a turbine depending on <br />surrounding terrain, trees and buildings, <br />and wind re'source. Therefore, tower <br />height restrictions~ jf any, ?hould only <br />reflect sound and safety concerns rather <br />than be designed to correspond to a <br />system's generating capacity. Most <br />often, in fact, established sound and <br />setback requirements negate the need <br />even to mention height in regulations <br />for small wind systems. <br /> <br />