Renewable sources of energy are replenished by?

Renewable energy sources are energy sources that are continually replenished. These include energy from water, wind, the sun, geothermal sources, and biomass sources such as energy crops. In contrast, fuels such as coal, oil, and natural gas are non-renewable. Once a deposit of these fuels is depleted it cannot be replenished -- a replacement deposit must be found instead. Both renewable and non-renewable energy sources are used to generate electricity, power vehicles, and provide heating, cooling, and light.

Renewable sources of energy vary widely in their cost-effectiveness and in their availability across the United States. Although water, wind, and other renewables may appear free, their cost comes in collecting, harnessing, and transporting the energy so that it can do useful work. For example, to utilize energy from water, a dam must be built along with electric generators and transmission lines.

Renewables themselves are non-polluting, while the structures built to harness them can have positive or negative environmental impacts. For example, dams may affect fish migration but may also create wildlife habitat