Glossary of Terms

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 Watt-hour

A unit of energy.  One watt-hour is the amount of electrical energy equivalent to a one-watt load drawing power for one hour, or a one-watt generator producing power at capacity for one hour.  The kilowatt-hour (kWh) is equal to 1000 watt-hours, and the Megawatt-hour (MWh) is equal to 1000 kilowatt-hours or 1 million watt-hours.

 Wheeling

The use of a local utility’s transmission and/or distribution system to transfer/sell generated electricity to another utility.

 Wind Power Class

A simplified and standardized measurement to compare wind resource.  Classes ranging from 1 (power density less than 200 watts/m2) to 7 (power density greater than 800 watts/m2).

 Wind Power Density

A measurement (expressed in watts/m2) of wind speed and air density, which together determine how much energy can be harnessed from the wind.

 Wind Rose

A diagram showing the direction from which the wind blows, and the percentage of power by direction.

 Wind Shear

The difference in wind speed and/or direction between two points.  Wind speed at the height of a proposed turbine can be estimated if the wind speed at a lower height and the site’s shear are known.