Windmills have had a long history of being used for agricultural purposes. Now the wind turbine, an evolved version of the windmill, is used for generating electricity as a source of renewable energy. The blades of a wind turbine form a rotor that captures wind energy. Energy increases with height above the ground surface. For this reason, wind turbines are ideally located on tall towers, at least 100 feet above the ground.

The physics of a wind turbine involve lift and drag. Lift occurs when a low-pressure air pocket forms when the wind blows against the downside of a blade. This blowing of the wind against a blade is an example of drag. The force of lift is greater than that of drag. The spinning rotor spins a shaft, which in turn spins a generator to create electricity.

Turbines can be used alone or combined with other renewable energy systems. An efficient way to collect wind energy involves the building of clusters of turbines to form a wind plant.

(Information gathered from the National Renewable Energy Laboratory page on wind energy: ttp://www.nrel.gov/clean_energy/wind.html)

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