Fossil fuels are nonrenewable, they draw on finite resources that will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve. Alternative energy or renewable energy sources, such as wind and solar energy, are constantly replenished and will never run out.
Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses.
Wind energy is captured with wind turbines.
The organic matter that makes up plants is known as biomass. Biomass can be used to produce electricity, transportation fuels, or chemicals. The use of biomass for any of these purposes is called biomass energy.
Hydrogen can be found in many organic compounds, as well as water. It's the most abundant element on the Earth. But it doesn't occur naturally as a gas. It's always combined with other elements, such as with oxygen to make water. Once separated from another element, hydrogen can be burned as a fuel or converted into electricity.
Geothermal energy taps the Earth's internal heat for a variety of uses, including electric power production, and the heating and cooling of buildings.
The ocean can produce thermal energy from the sun's heat and mechanical energy from the tides and waves.
Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower.