Wind Energy: History of Windmills

The unequal heating of land and water by solar radiation is the cause of wind generation on the earth's surface. It is one of the forms of energy made available by nature, and is available free of cost. As per a study by NASA, the US has the potential to generate 1.28 trillion KWh of electrical energy per year.

Wind power plants, or wind farms, as they are popularly called, are clusters of individual generators. Unlike nuclear or coal plants, most wind plants are not owned by public utility companies. Instead they are owned by and operated by businessmen, who sell the electricity produced on the wind farm to utilities. These private companies are known as Independent Power Producers.

Operating wind power plants is not as simple as plunking down machines on a grassy field. Wind plant owners must carefully plan the location of their machines. They must consider availability of the wind, local weather conditions, the convenience in connecting to the power grid, etc. One wind machine needs up to two acres of land. A wind power plant takes up hundreds of acres. The land can still be used by farmers to grow crops around the machines once they are they installed.

The potential of wind power was recognized quite early on in the development of human civilization. Over 5000 years ago, the ancient Egyptians used wind power to sail their ships over the Nile River. Later people built windmills to grind grain. The earliest known windmills looked like large paddle wheels.

Centuries later, the Dutch improved the windmill. They thought of propeller-shaped blades that could be turned to face the wind. American colonists used windmills to grind wheat and corn, to pump water, and to cut wood at sawmills.

A wind turbine, the vital part of power generation, converts the kinetic energy of the wind into mechanical energy transmitted by the shaft. It is further converted into electric energy with the help of a generator, thus producing electricity. Windmills are generally categorized into two types as:

1) Horizontal axis
2) Vertical axis

Depending on their axis of rotation, they are further sub-classified as:

Horizontal axis type windmills are further classified as:
a) Single-bladed
b) Double-bladed
c) Multi-bladed
d) Bicycle multi-bladed
e) Sail
f) Wing

Vertical axis type windmills are further classified as:
a) Savonius-type machines
b) Darius-type machines

These power plants have certainly risen as one of the most important sources of energy.