Concerns about pollution resulting from the production of electrical power have led to the development of wind turbines.
The wind generators are more like giant propellers with two or three blades, called rotors, mounted on top of tall towers of steel or concrete. The rotors turn a shaft which drives an electric generator.
The size of the blades and the height of the tower determine how much electricity the machine can generate. Wind generally gets stronger as you go higher, and the power of the wind you capture depends on the swept area of the blades. Double the length of the blades and the power increases four–fold. More important still is the speed of the wind, for the power that can be extracted goes up as the cube of wind speed – if it blows twice as hard, there is eight times as much power to be had.
Wind generators must point in the right direction, either directly towards the wind or directly away from it. The rotors mounted on the turntable are connected to sensors through an electric motor which tell it which way to face. This problem of wind direction can be avoided completely if the blades are mounted on a vertical rather than hotizontal axis.
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Vertical Axis Turbines
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