Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetative cover. This wind flow, or motion energy, when "harvested" by modern wind turbines, can be used to generate electricity.

What is wind?
Wind is the movement of air over the surface of the Earth, from areas of high pressure to low pressure. But what causes the changes in pressure? There are a few concepts that we will have to explore to find exactly how this works, but ultimately all the energy on our planet comes from the Sun.

The Sun gives out all sorts of radiation, including heat and light energy, and is so powerful that it radiates 170,000,000 GW of energy to the Earth!  When this energy reaches the Earth, the ground and other surfaces absorb it, and heat the surrounding air. It's these differences in temperature, together with the rotation of our planet, that create the wind.

About 1 to 2 per cent of the energy coming from the sun is converted into wind energy, which is enough to meet the electricity needs of the world three times over, and is a source of power that will never run out.

hestory

Wind power has been harnessed for many, many years. Nobody knows for sure when man started using the wind's power to grind flour or pump water, but it is thought that the first windmill appeared in the Persian region. From there this windmill technology spread back to northern Europe. Windmills crafted by the Dutch were used primarily to pump water.

Windmills were definitely not the first structures to harness the wind. This award belongs to the sailboat. More than likely, founded in small scale (small canoe with an animal skin as a sail) the sailboat became the only way to cross large areas of water. The sailboat evolved into large ships moving great distances by using only wind as a source of power.

Windmills on a smaller scale showed up in America in the mid 19th Century. The Aermotor and Dempster design were invented and many are still in use. From 1850 to 1970 more than 6,000,000 windmills were installed in the United States. The main application was pumping water for livestock and providing farm homes with a water supply.

In the late 19th Century, the first windmill to generate electricity was born! This was the Brush postmill in Cleveland Ohio, and the year was 1888! The rotor was approximately 17 meters in diameter. This windmill had a gearbox with a high spin ratio attached to a DC generator.

By the middle 1920's, several small scale systems were found across the Midwestern plains and used to supply farms with electricity. These systems generally had a 1 to 3 kilowatt output.

1941 saw the largest wind generator to date. This generator's capacity was 1.25 megawatts. It was known as the Smith-Putnam machine. The rotor measured an astonishing 175 feet in diameter.

Today, many wind turbines are in operation from small scale residential systems that are affordable to the homeowner to large scale wind turbine farms that are used to supply a large amount of electricity to utility customers.