by John Traveler

Created on: August 06, 2010   Last Updated: August 15, 2010

Today in the United States, wind turbines are popping up just about anywhere the wind blows with any degree of regular ferocity. Their characteristic pedestals stand out on the horizon like megalithic pylons, supporting what looks to be a large three-blade aircraft propeller. As one gains closer vantage point, the stark reality suggests these ominous propellers are much larger than anything ever attach to a flying machine, except perhaps the rotor of a helicopter.

Technically speaking, the three-bladed monstrosities are not propellers, they are turbines, the difference being the former moves the air and the latter is moved by the air. As anyone knows, the wind exerts a force on anything and everything it encounters and wind turbines convert a little bit of this force into mechanical energy which is then used to generate electricity.

The pitch of wind turbine blades is adjustable. When the blades are turned perpendicular to the oncoming wind, the force applied is felt equally on both sides of the blade, thus holding it static and immobile. As blade pitch is adjusted, exposing a larger surface area of one side of the blade to the oncoming wind, the wind force pushing on that side of the blade increases with respect to the back side of the blade. This pressure offset causes the blade to move in a direction towards its low pressure side. With all three turbine blades set at the same pitch and feeling the wind pressure simultaneously, the turbine rotor begins to spin. A small vertical fin at the back end of the turbine called a fantail, keeps it turned into the oncoming wind.  

The mechanical energy imparted to each blade is transferred to a shaft in the hub of the turbine and causes a great amount of torque to develop on the shaft. At the other end of the shaft, a gearbox transfers the energy to a secondary shaft. The step up gearing causes higher revolutions per minute (rpm) in the secondary shaft and consequently lower torque. A generator or alternator is mounted on the secondary shaft and converts the mechanical energy originally imparted by the wind to the turbine into electrical energy. It all seems pretty simple, and it would be if not for a small problem.

The alternating current (A/C) electricity used in the United States oscillates at 60 hertz or cycles per second. In Europe and other places 50 hertz is used. Regardless of the frequency used, it must be precisely maintained, that is if you want your electric clock to keep good time and other electrical

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