Along with the rain and snow, sunlight causes plants to grow. The organic matter that makes up those 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.
Not all renewable energy resources come from the sun. Geothermal energy taps the Earth's internal heat for a variety of uses, including electric power production, and the heating and cooling of buildings. And the energy of the ocean's tides comes from the gravitational pull of the moon and the sun upon the Earth.
Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. Hydroelectricity is a renewable source of energy, produces no waste, and does not produce carbon dioxide (CO2) which contributes to greenhouse gases.
The ocean can produce thermal energy from the sun's heat and mechanical energy from the tides and waves. Ocean Thermal Energy Conversion (OTEC) is a method for generating electricity which uses the temperature difference that exists between deep and shallow waters to run a heat engine.
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.
The sun's heat also drives the winds, whose energy is captured with wind turbines. Then, the winds and the sun's heat cause water to evaporate. When this water vapor turns into rain or snow and flows downhill into rivers or streams, its energy can be captured using hydropower.