How Does It Work?
The Basics:
Wind power transforms the kinetic energy of the wind into mechanical power, which is turned into electricity by a generator. The blades of the turbine drive the shaft of the generator by using the aerodynamic concept of lift. The blades, like airplane wings or sailboats, are tapered aerofoils; the cross-section of a blade looks like a tear drop. As wind flows over the blade, a difference in air pressure is created; this results in lift. The lift then turns the turbine blades with drive the shaft of the generator. The generator produces electricity that is fed to local transmission lines.
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1998 by the American Wind Energy Association.
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Design Variations:
Some turbines have horizontally-oriented blades (like a traditional water-pumping windmill) while other have blades that are vertically-oriented (like an eggbeater). The turbines range in height, blade length, and output. One huge turbine in Hawaii has propellers as long as half the length of a football field. The turbine stands 20 stories high and can power ~1400 homes! In contrast, a small, home-sized turbine has blades between 8 and 25 feet long and stands about 30 feet high. Some machines have emergency shutdown systems so that if any part of the turbine fails, brakes are enabled.
Output:
Not all of the wind flowing through a turbine is converted to electricity. Efficiency limits on the blades, shaft, generator, and transmission lines limit the output electricity. As the efficiency of these individual components is increased due to technological advancement, wind power becomes more economically feasible. The average size of a turbine in the United States is 100 kW, though large units (> 500 kW) are becoming more common. Reasonable outputs are reached in geographic areas with an average annual wind speed greater than 12 miles per hour.