Global renewable energy resources and use in 2050

The main forms of renewable energy (RE) used today are biomass energy, hydroelectricity, wind energy, solar energy, and geothermal energy. Although several other RE sources have been extensively discussed, including various forms of ocean energy, these five are likely to still be dominant in 2050. In assessing the probable future of each RE type, it is important to know what factors will tend to enhance or decrease their future output. These include: their energy return on input energy; their technical potential; the impacts that future land use, climate, and other environmental changes will have on their availability; and alternatively, the effects of RE production on the environment.