Wind: A Renewable Energy Source Wind is called a renewable energy source because it will be continuously produced as long as the sun shines on the earth. The sun's contribution to wind energy is the conversion of air into heat or cool wind. Wind is produced by the uneven heating of the Earth's surface by the sun. On land the warm air spreads and rises into the sky, in the water the heavier, cooler air moves to take the place of the warm air, thus providing local winds. This energy source should be used more often in the United States due to its safer environmental and financial standards. To capture this wind, turbines are used to convert the renewable resource into electricity. The energy in motion or kinetic energy is then processed mechanically. Windmills are used in the United States and other countries around the world. They are used to heat water, refrigerate produce, dry crops, irrigate crops, heat buildings, and charge batteries for tractors on farms, etc. Most windmills today extract about 30% of wind energy (www.earthsci.org). Windmills are as efficient as coal; the difference between them is that air is less polluting than coal. Unfortunately there is no 100% efficient energy source. “For a fully efficient energy source, power plants must operate all day and all year without interruption” (www.eia.doe.gov). To make it so that they depend on windmills to convert electricity ...