Wind Energy

Wind energy is a form of alternate energy that can be produced by harnessing the power of wind. The wind turbine, the modern-day equivalent of the windmill, is used to capture the wind's power and to generate energy from that power. As a form of energy, wind energy is both renewable (i.e., inexhaustible) and sustainable (i.e., able to be maintained without depleting natural resources). Wind energy's potentially infinite supply is capable of providing power to large populations in areas where wind is plentiful and readily available.

Brief History

Wind energy has been readily available and used as a source of power throughout recorded human history. Ancient peoples, such as the Egyptians, used wind power to move boats from one place to another by capturing the wind in boat sails. Later, windmills were erected and used in China, Persia and the Middle East -- as early as 400 BCE -- to provide irrigation and power for grain mills. These windmills used "sails" made of reed or cloth, which spun horizontally, to produce energy from the wind. Later, windmills used sails that spun vertically to capture wind energy, such as the windmills erected by the Dutch and later throughout Europe and the Far East. This technology was brought to North America by the earliest settlers, as they began to spread across the continent.

Wikipedia's entry "History of Wind Power" has a complete history of the world-wide development of wind power and windmills.

Modern Wind Turbines

Modern wind turbines have replaced windmills in the cultivation of wind to create energy. The modern wind turbine operates on the same principles as early windmills, but is significantly more efficient in harnessing wind power to produce energy. The modern wind turbine consists of a two- or three-bladed propeller-like rotor, which sits atop a very tall tower. The tower stands one hundred or more feet high, to take advantage of the faster winds and lower turbulence present at greater heights.

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Generally speaking, wind turbines convert kinetic energy (the flow of wind) into mechanical energy that can be used to perform specific tasks, or into electricity via a generator that can be used as a source of power. The wind turns the blades of the rotor, which is connected by a shaft to a generator. The shaft spins the generator to create electricity. The U.S. Department of Energy's website provides a animated image of the inside of a wind turbine as well as a working animation to show exactly how wind turbines convert the movement of wind into electricity.

Types of Wind Turbines

In the United States, most modern wind turbines are found on farms, and take the form of a multi-bladed rotor atop a tall tower shaft attached to a generator (see image above). These turbines are similar in form to the older windmill: they operate on a horizontal axis, in which the blades sit on a horizontal axis or axel. Horizontal-axis wind turbines, or HAWTs, work best in high wind-flow areas, using their height and design to operate efficiently. HAWTs must face the direction of wind flow: older and smaller versions use a weather-vane design to turn the blades to face the wind, while newer and larger HAWTs use motors to adjust the direction of the blades to face the wind.

By contrast, vertical-axis wind turbines (VAWTs) are designed so that the blades sit on a vertical axis or axel (such as the Darrieus Wind Turbine and the Savonius wind turbine). Because vertical-axis are less common but gaining popularity.

Smaller versions of the turbine are used to power individual households, businesses and small farms.