How Does a Solar-Powered Windmill Work?
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The Solar Energy Option
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With global warming prevalent and coal and oil sources dwindling, many are turning to renewable energy as an option. First used over 5,000 years ago to pump water and grind wheat and other grains, windmills (also called turbines) are now being utilized to harness the sun and generate electricity in mass quantities. Not only is wind an inexhaustible source of energy, there are virtually no waste byproducts, thus making it the "greenest" energy source in the world.
The Mechanics of a Windmill
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As earth's surface air warms and cools at different rates, the warm air rises and the cool air replaces it, causing wind. Air currents created by the sun's rays flow over the blades of a windmill, causing the blades to rotate at a rapid pace. The blades, in turn, are connected to a drive shaft, which powers a generator. This captures the air's kinetic energy and converts it to other forms of energy such as electrical. The electricity, in turn, is conducted through wires and either used directly or stored in deep cell batteries.
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Sizes of Windmills
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Blade sizes can range from a few feet to hundreds of feet in diameter, generating enough power to fuel one home or thousands when used collectively on a wind farm. One small windmill will generate about 100 kilowatts of energy, while the largest wind farm in the world (Horse Hollow Wind Energy Center in Texas) generates over 735 megawatts of electricity a year from 421 wind turbines spread out over 47,000 acres: enough to power 220,000 homes a year.
Types of Windmills
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There are two basic types of windmills in use today. The first is the horizontal-axis, which is the most common. With blades designed like an airplane propeller, horizontal-axis windmills are typically the height of a 20-story building and have three blades that span 200 feet across. These are the types of windmills used on wind farms, where dozens of turbines are situated over many acres of land.
Vertical-axis windmills have blades that look somewhat like an eggbeater. Standing about 100 feet tall and 50 feet wide, they are not as efficient as the horizontal-axis style and comprise a small percentage of windmills in use today.
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