Wind is simply air in motion. It is caused by the uneven heating of the Earth’s surface by the sun’s radiant energy. This motion is due to difference in the earth’s surface composition, which causes a difference in the rate at which the sun’s energy is absorbed. An ideal situation for the formation of wind is an area where land and water meet. During the day, the air above the land heats up more quickly than the air above water. The warm air over the land expands, becomes less dense and rises. The heavier, denser, cool air over the water flows in to take its place, creating wind. In the same way, the atmospheric winds that circle the Earth are created because the land near the equator is heated more by the sun than land near the North and South Poles.
The power in the wind has been put to good use for over 5,000 years, since the ancient Egyptians used it to sail ships on the Nile. Later, windmills were built to grind wheat and corn, to pump water, and to operate sawmills. Centuries later the windmill design was improved upon, in Holland, by replacing the paddle wheels type design with the propeller blade type design we have grown to know and love.
Today wind power is the fastest growing form of renewable energy source used for electricity generation. And, like old-fashioned windmills, today’s wind turbines capture the wind’s kinetic energy as the wind moves across and pushes against the blades, to produce a mechanical rotation. An electric generate coupled to the propeller’s (rotor) shaft generates electricity from this rotation, which is then transmitted via electrical cables to the electricity grid.