-Wind is simple air in motion. It is caused by the uneven heating of the earth’s surface by the sun.

-Wind energy converts kinetic energy that is present in the wind into more useful forms of energy such as mechanical energy or electricity.

-During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air rushes in to take its place, creating winds. At night, the winds are reversed because the air cools more rapidly over land than over water.

-In the same way, the large atmospheric winds that circle the earth are created because the land near the earth's equator is heated more by the sun than the land near the North and South Poles.

-Today, wind energy is mainly used to generate electricity. Wind is called a renewable energy source because the wind will blow as long as the sun shines.

nWindmills that were used to grind grain are an example of early uses of wind energy. Modern uses of wind energy include generation of electricity and pumping water. Current wind energy machines are called "wind turbine generators", "wind pumps", or more generally, "wind turbines".