Electricity produced by sources that collect solar radiation. Photovoltaic panels are semiconductors that directly generate electricity. Solar thermal plants use the sun's energy to turn a turbine. Capturing the energy of the earth's winds to turn turbines and generate electricity is the cheapest, fast-growing source of renewable electricity. Geothermal electricity is generated by utilizing steam that lies below the surface of the earth in certain locations.
Geothermal plants emit little air pollution.