Most of the energy we use today comes from fossil fuels-coal, oil, and natural gas. These are fuels that are being consumed more rapidly than they are being replaced. That means that someday we could run out of these fuels. Renewable energy comes from energy sources that are constantly being replaced and are usually less polluting than energy from fossil fuels. Examples of renewable energy include solar, wind, geothermal, biomass and hydro.
Solar energy comes from the sun.
It is used to heat homes and water in more than 200,000 houses in the United States today. PV cells make electricity without moving, making noise, or polluting. We most often see these in calculators and watches. Wind is used to generate electricity. The windmills built long ago had many blades, but today's wind turbines usually have just two or three blades that turn when the wind blows.