Wind resources can vary significantly over an area of just a few miles due to local terrain influences on the wind flow. As a first step in evaluating whether there is enough wind on your site to make a small wind turbine system economically worthwhile, wind resource maps like this one can be used to estimate the potential wind power density in your region. The highest average wind speeds in the U.S. are generally found along seacoasts, on ridgelines, and across the Great Plains; however many areas have wind resources strong enough to power a small wind turbine. The wind resource estimates on this map generally apply to terrain features that are well exposed to the wind, such as hilltops, ridge crests, and high plains.
Although local terrain features may cause the wind resource at specific sites to differ considerably from these estimates, you can get a ballpark estimate of your expected power production by multiplying the first column of the key corresponding to the color of your area by the rotor swept area of your wind turbine. For example, a 20 kW turbine with a 30-foot (10-meter) rotor diameter has a 700 square-foot (78 square-meter) swept area and in a Class 4 wind regime (pink) on an 80-ft (24-meter) tower would be expected to produce 48,000 – 54,000 kWh per year, reflecting a 27-31% capacity factor.
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