Solar power is most commonly produced when photovoltaic (PV) systems convert sunlight into electricity. PV systems are made of solar cells, which absorb the photons in sunlight, causing the free flow of electrons through the cellís circuit. Today, some cells can convert up to a quarter of the sunlight that shines on them into electricity.
Compared to other countries, the United States receives more solar energy in the summer than other times of the year because days are longer and the sun is nearly overhead. The sun's rays are far more slanted during the shorter days of the winter months.
Wind power is produced by wind turbines, which convert the kinetic energy of wind into mechanical energy to generate electricity, charge batteries, pump water and grind grain. Most wind energy technologies can be used as stand-alone applications, connected to a utility power grid or even combined with a photovoltaic system. For utility-scale sources of wind energy, a large number of turbines are usually built close together to form a wind farm that provides grid power.
Stand-alone turbines are typically used for water pumping or communications. However, homeowners and farmers in windy areas can also use small wind systems to generate electricity. Learn more about small wind electric systems from Energy Savers.
Biomass is organic material made from plants and animals. Examples of biomass fuels include wood, crops, manure and some garbage. Most electricity generated from biomass is produced by direct combustion using conventional boilers. These boilers primarily burn the organic materials to produce steam, which spins a turbine. The spinning turbine then activates a generator that produces electricity.