Renewable energy is of many types, including wind, solar, hydro, geothermal (earth heat), and biomass (waste material). All renewable energy with the exception of tidal and geothermal power, and even the energy of fossil fuels, ultimately comes from the sun. About 1%–2% of energy coming from the sun is converted into wind energy. Today, the most prevalent renewable energy resources are wind and solar that will be reviewed brie¶y in this chapter.