Wind is created from an unequal heating of the earths atmosphere therefore wind is an indirect form of solar energy. Convection currents, which occur due to the fact that warm air rises and cooler air drops, produces this cycle of air or wind. Some of the suns energy directly heats the air but mostly the heat is transferred form the earth into the atmosphere. "Between 1 - 2% of the solar radiation that reaches the Earth is converted into energy in the wind."1.

Seasonal variations in the speed and direction of the wind result from the seasonal changes angle of the Earths spin relative to the Sun. Daily variations are caused by the different speeds of heating different surfaces, for example land and oceans heat up at different speeds.2

The force excreted by wind on a propeller or some sort of mechanical instrument is used to create motion. Thus converting mechanical energy into electrical is not a problem. The process is the reverse of an electric motor which uses a magnet to force the shaft to spin. Likewise if the shaft spins it will induce a magnetic field thus providing electricity. "There are three basic physical laws governing the amount of energy available from the wind. The fir

"Practical wind turbines are designed to work between certain wind speeds. The lower speed, called the 'cut in speed' is generally 4 - 5 ms-1, as there is too little energy below this speed to overcome system losses. The 'cut out speed' is determined by the ability of the particular machine to withstand high wind. The 'rated speed' is the wind speed at which the particular machine achieves its maximum rated output. Above this speed, it may have mechanisms that maintain the output at a constant value with increasing wind speed."5.

st law states that the power generated by the turbine is proportional to the wind speed cubed. For example if the wind speed doubles, the power available increases by a factor of eight; if the wind speed triples then twenty seven times more power is available." Therefore a proposed site must have a very fast wind a lot of the time to generate electricity. It is very expensive to deploy lots of wind turbines if each is only going to produce very little electricity. "The second law states that the power available is directly proportional to the swept area of the blades. That is the power is proportional to the square of the blade length. For example, doubling the blade length will increase the power by four times, and tripling the blade length will increase the power by nine times. The third law states that there is a maximum theoretical efficiency of wind generators of 59%. In practice, most wind turbines are much less efficient than this, and different types are designed to have maximum efficiency at different wind speeds. The best wind generators have efficiencies of about 35 - 40%."3.

Wind is not a reliable source of energy in som

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Approximate Word count = 1128
Approximate Pages = 5 (250 words per page double spaced)