Wind energy should be measured by capacity

In an April 9 wind energy article by David DeWitte, he quoted wind energy capacity in terms of rated energy output. This is  a  misrepresentation of the actual energy produced. Because of wind variability, rated output is not available - in fact, the typical wind farm provides only 20 percent to 40 percent of rated capacity. This percentage is the capacity factor.

A better measure than rated energy is actual energy - obtained by multiplying rated capacity by the capacity factor. For example, a one-megawatt turbine operating at full capacity would produce a yearly 8,760 megawatt hours (MWh) of energy but, at a 35 percent capacity factor, would produce only 3,066 MWh.

Capacity factor is important in comparing various energy sources. Nuclear energy plants, for example, typically have a capacity factor of about 90 percent.

Quentin Wagenfield

Cedar Rapids