Windmill is a machine that is operated by wind power. Windmills are used chiefly to provide power to pump water, grind grain, or generate electric power. Modern windmills used to produce electric power are called wind turbines.
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Most windmills have a rotor of blades or sails that is turned by the wind. Typically, wind turbines have two or three blades, and other windmills have more. In most cases, the rotor is set on a horizontal shaft. The shaft is mounted on a tower, mast, or other tall structure. The shaft is turned by the movement of the rotor, and it transmits power, through a series of gears, to a vertical shaft. The shaft then transmits power to a water pump, flour mill, electric generator, or other device.
Windmills probably originated in the A.D. 600’s in Persia, now Iran. These windmills had sails that revolved around a vertical axis. People used these windmills chiefly to grind grain.
By the 1100’s, windmills had spread to Europe. About this time, inventors discovered that windmills produced more power if the sails or blades turned on a horizontal shaft. This discovery eventually led to the development of Dutch windmills. These windmills were widely used in the Netherlands to drain water from the land and to mill grain. Dutch windmills had four long arms, and cloth sails or wooden slats or shutters were mounted on the arms.
During the 1800’s and early 1900’s, many American windmills were built throughout the United States to pump water. The rotor of these windmills had curved blades of wood or steel, and was mounted on a horizontal shaft. A vane on the end of the shaft opposite the rotor moved the rotor to face the wind.
