Jay Burton, age 11, of Fargo, N.D., for his question:
WHEN WAS THE FIRST WINDMILL USED?
A windmill is a mechanical device that converts the energy of the wind into power. It is a machine that is known as a prime mover. Wind driven machines can be traced back to as early as the 7th Century in Persia where they were used for milling grain and pumping irrigation water. The early windmills were rather inefficient but the idea spread to China and to most of Islam.
Early in the 12th Century the windmill turned up in England and then it appeared across Europe. These early machines were called post mills.
The tower mill was developed in France in the 14th Century. It had stationary machinery inside a masonry tower topped by a rotatable wood sided cap bearing the windshaft and the upper portion of the mill gearing.
These early windmills had horizontal shafts that protruded from the cap, or upper portion of the mill building. Four to eight wind sails, each about 10 to 30 feet long, radiated from the exterior end of the shaft. The wood frames of the sails were either covered with canvas or fitted with wood shutters. The power of the turning shaft was transmitted through a system of gears and shafts down to the mill machinery at the base of the building.
Between the 15th and 19th centuries windmills were used for milling grain and irrigating farmland, and also adapted to such jobs as pumping seawater as part of land reclamation projects. By the 19th Century the Dutch had built about 9,000 windmills, many of which are still in use today.
The fantail was invented in 1745. This is a mechanism that automatically rotates the sails into the wind.
In 1772 the spring sail came into being. This is a sail made of wood shutters, the openings of which can be controlled either automatically or by hand to maintain a constant sail speed in winds of varying speeds.
In 1890 the first windmill was used to power an electric generator. By 1920 windmills generating electricity were widely used.
Today windmills are most often built of steel.
Generally speaking, the power of windmills increases with the diameter of the wheel.
A mill used to pump water has a wheel of blades set at a common angle and mounted on a horizontal shaft. The wheel is held with its face toward the wind by a vane or rudder. The wind hits the blades of the windmill at an angle and forces the wheel to revolve. The mill gets the full force of the wind by being mounted on a tower at least 20 feet high.
Wind electric mills have a propeller type wheel with two or three blades that turns at high speed. The wheel is usually mounted on a mast held up by guy wires. The wheel is connected to an electric generator through gears.
The sizes of wind electric plants range from those that produce 100
watts to those that turn out 2,000 watts. Many windmill were erected in windy areas to generate electricity. Near Palm Springs California hundred of windmills spin daily and generate electricity that is feed into the electrical distribution system.