Windmill is a machine that converts wind into useful energy. This energy is derived from the force of wind acting on oblique blades or sails that radiate from a shaft. The turning shaft may be connected to machinery used to perform such work as milling grain, pumping water, or generating electricity. When the shaft is connected to a load, such as a pump, the device is typically called a windmill. When it is used to generate electricity, it is known as a wind turbine generator. This paper finds out the first windmills and its uses and improvements. It also tackles on the modern wind turbines.
I. Introduction Wind-driven mills are of ancient origin. Simple windmills may have been used in Persia (now Iran) as early as the 7th century ad. They were used for irrigation and milling grain. The wheel bearing the wind sails of the earliest windmills was horizontal and supported by a vertical shaft. These machines were relatively inefficient. Nevertheless, this type of windmill spread to China and throughout the Middle East. The earliest European windmills appeared in France and England in the 12th century and became widely used throughout Europe.
These early wood structures, called post mills, were rotated by hand around a central post to bring the sails into the wind. The tower mill was developed in France during the 14th century. It consisted of a stone tower topped by a rotatable wooden cap that supported the windshaft and the upper portion of the mill gearing (see “Wind Mills”. Grolier Encyclopedia of Knowledge, pp. 678-681. vol. 18). Early windmills all share certain features. A horizontal shaft protrudes from the cap, or upper portion of the mill building. Four to eight wind sails, each about 3 to 9 m (10 to 30 ft) in length, radiate from the shaft.
The wood frames of the sails are either covered with canvas or fitted with wood shutters. The power of the turning shaft is transmitted through a system of gears and shafts down to the mill machinery at the base of the building. II. Discussion A. Uses and Improvements of Windmills Besides milling grain and irrigating farmland, windmills built in the period from the 15th century to the 19th century were adapted to a variety of tasks, including pumping seawater from land below sea level, sawing wood, making paper, pressing oil from seeds, and grinding many different materials. By the 19th century the Dutch had built about 9,000 windmills.
Of the major improvements on the windmill, the most important was the fantail, a mechanism invented in 1745 that automatically rotates the sails into the wind. In 1772 the spring sail was developed. This type of sail consists of wood shutters, the openings of which can be controlled either manually or automatically to maintain a constant sail speed in winds of varying speeds. Other improvements include air brakes to stop the sails from rotating and the use of propeller-like airfoils in place of sails, which increases the usefulness of mills in light winds (see “Windmill: Uses and Improvements”.
New Standard Encyclopedia, pp. 645-668, vol. 19). The application of wind turbines for generating electricity was pioneered in Denmark late in the 1890s and is in widespread use there today. Water-pumping windmills were widely employed during the settlement of the arid areas of the western United States. Small wind turbine generators supplied electricity to many rural communities until the 1930s, when power lines were extended across America; large wind turbines were also built during this time.