The wind is a source of clean, renewable energy. Wind power emits no pollution and has very little impact on the land. Wind energy can be produced anywhere the wind blows with consistent force. PV systems change sunlight directly into electricity. Solar thermal systems use the sun's energy to heat a fluid that produces steam, which then turns a turbine and generator.
Dams provide electricity by guiding water down a chute and over a turbine at high speed.
Although hydropower does not produce any air emissions, large dams must also consider environmental issues such as flood control, water quality, and fish and wildlife habitat. Therefore, while large hydro power is clean, it is not green. Coal is developed from decaying plants and becomes a black or brown rock. Strip mining or underground mines are built to extract coal. These mines cause severe erosion, leaching of toxic chemicals into nearby water sources, and loss of habitat.