Windmill and Wind Turbine
The windmill is a simple device used over the years for many valuable purposes: grinding grain, driving saws, pumping water, driving electric generators, and charging storage batteries. The windmill harnesses natural wind energy for human use--the whirling propeller shaft transmits its rotary motion through gears, converting it into power that people can use.
Windmills go far back in history. Nearly 4,000 years ago the Babylonian emperor Hammurabi (1792-1750 B.C.) used them for irrigation. About 200 years before Christ, Hero of Alexandria described a windmill in his writings. By 1000 A.D. these machines were in practical usage throughout Europe. In 1105 a French convent built both a water mill and a windmill.
It was the Dutch who made the most extensive use of windmills. Inhabitants of the Netherlands faced a drainage problem for centuries. Their land was actually a series of marshes separated from the sea by a belt of dunes, mostly below sea level. Sections of land called poders were surrounded by high earthen walls, or dikes, to protect them from the sea, and people led precarious lives huddled on top of earthen mounds. In the fifteenth century this situation changed. Using powerful windmills, the Dutch were able to pump unwanted water from the polders. For example, by 1608 a 10-foot (3 m) deep lake had been emptied by 26 windmills.
At the height of their use, over 9,000 windmills lined the dikes and canals which covered the land. These windmills had sails made of 30-to 50-foot (9-15 m) long wooden frames with canvas covering their lattice or framework. The sails were attached to a central wooden axle, or shaft, that was connected to large, toothed gears which could provide power for pumping. The older types of windmills were made so the entire mill house, with its sails, could be turned around its shaft to face the wind. The Dutch also used the configuration of the windmill's wings to send messages--if the wings were positioned straight up and down in a cross formation, this indicated the birth of a baby. To announce weddings, the sails formed an X with garlands of flowers woven into the framework. During World War II, windmill sails signaled German troop movements to the Dutch resistance fighters. With the invention of the steam engine in England in the nineteenth century, the Dutch, too, began to shift to the new form of power. But many windmills still exist there, either as homes or as functioning windmills.
In the United States there was little interest in the European-style windmills because they were costly to build and cumbersome to operate. In 1854, Daniel Halliday revolutionized the entire concept of wind power when he invented an easily constructed tower, topped by a light wheel fitted with automatic mechanisms to break its speed when the wind increased or when a tank of water was full. This type of windmill was later used to generate enough electricity to meet the needs of a small house. Some historians believe that this windmill was a major factor in the rapid settling of the West.
As fossil fuel prices skyrocket and supplies are depleted, wind power is becoming an attractive alternative energy source. Much thought and effort has gone into designing better windmills. A German design uses two blades and an electric generator mounted on the axis between the two rotors. It does away with gears, and is able to convert more of the wind's energy to use than conventional windmills, at a cost very competitive with fossil fuels. Simple egg beater windmills with a vertical axis and two thin, curved blades attached at the top and bottom are used in many locations. Of course, windmills have the further advantage that they emit no pollution.
The federal government and several universities have sponsored wind power research projects. One interesting possibility is the Chalk windmill, an airfoil that looks like a bicycle wheel, with 48 blades capable of spinning in breezes which will not budge other windmills. Another wind visionary, William Heronemus of the University of Massachusetts, has called for a network of gigantic windmills off the coastline of the United States. The energy produced by them would be used to convert ocean water to hydrogen and oxygen, and the hydrogen would be shipped ashore to be combined with the oxygen in fuel cells to produce electricity without pollution.
Many believe that wind power will be the power of the future. It is estimated that, with today's technology, wind power could supply about 20% of the United States' electricity. For the twenty first century, it is thought that installation costs for wind turbines, and ultimately the electricity they produce, will be cheaper than more conventional means like hydroelectric plants or nuclear reactors--without concerns about a nuclear accident or environmental damage. To date Europe has been ahead in the exploration and acceptance of windmills and wind turbines to generate power needs.
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