Wind turbines work on a simple principle: instead of using electricity to produce wind, like a fan, wind turbines use the wind to produce electricity. The wind spins the turbine’s propeller-like blades around a rotor, which turns a generator that creates electricity.
Wind is a form of solar energy that results from the combination of three simultaneous events:
- The sun heats the atmosphere unevenly;
- Unevenness of the earth’s surface;
- The rotation of the earth.
Wind patterns and speeds vary greatly across the United States and are altered by bodies of water, vegetation, and differences in topography. People use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.
The terms “wind power” and “wind energy” describe the process by which wind is used to produce mechanical power or electricity. This mechanical power can be used for specific tasks (such as grinding grain or pumping water), or a generator can convert this mechanical energy into electricity.
A wind turbine converts wind energy into electricity using aerodynamic force from rotor blades that work like airplane wings or helicopter rotor blades. As the wind flows across the blade, the air pressure on one side of the blade decreases. The difference in air pressure on both sides of the blade creates both lift and drag. The lift force is stronger than the drag force, and this causes the rotor to rotate. The rotor is connected to the generator either directly (if it is a direct-drive turbine) or through a shaft and a series of gears (gearbox) that accelerate the rotation and allow the generator to be physically reduced. This conversion of aerodynamic force into generator rotation creates electricity.
Most wind turbines are divided into two main types:
- Horizontal-axis turbines;
- Vertical-axis turbines.
Wind turbines can be built on land or on the shore of large bodies of water such as oceans and lakes. The U.S. Department of Energy is currently funding projects to promote the deployment of offshore wind turbines in U.S. waters.
Application of wind turbines
Modern wind turbines can be classified according to their installation location and grid connection:
- Onshore wind;
- Offshore wind;
- Distributed wind.