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Renewable energy (also called green energy) is energy from renewable natural resources that are replenished on a human timescale. The most widely used renewable energy types are solar energy , wind power , and hydropower .
Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. [1] Renewable energy replaces conventional fuels in four distinct areas: electricity generation , air and water heating/cooling, motor fuels , and rural ...
Solar panels and wind turbines in Germany Placard for renewable energy, at the People's Climate March (2017) This is a list of renewable energy topics by country and territory. These links can be used to compare developments in renewable energy in different countries and territories and to help and encourage new writers to participate in ...
Variable renewable energy sources are those that have a fluctuating nature, such as wind power and solar power. In contrast, controllable renewable energy sources include dammed hydroelectricity, bioenergy, or geothermal power. Renewable energy systems have rapidly become more efficient and cheaper over the past 30 years.
Geothermal energy is a renewable resource because thermal energy is constantly replenished from neighbouring hotter regions and the radioactive decay of naturally occurring isotopes. [90] On average, the greenhouse gas emissions of geothermal-based electricity are less than 5% that of coal-based electricity. [84]
Renewable energy can be particularly suitable for developing countries. In rural and remote areas, transmission and distribution of energy generated from fossil fuels can be difficult and expensive. Producing renewable energy locally can offer a viable alternative. [9] Renewable energy doesn't always have to come from a developing country.
Renewable resources are available each year, unlike non-renewable resources, which are eventually depleted. A simple comparison is a coal mine and a forest. While the forest could be depleted, if it is managed it represents a continuous supply of energy, vs. the coal mine, which once has been exhausted is gone.
The potential energy density is equal to the kinetic energy, [1] both contributing half to the wave energy density E, as can be expected from the equipartition theorem. The waves propagate on the surface, where crests travel with the phase velocity while the energy is transported horizontally with the group velocity .