The International Energy Agency defines renewable energy as “energy that is derived from natural processes (e.g. sunlight and wind) that are replenished at a higher rate than they are consumed.” While solar, wind, and hydroelectric are perhaps the mostly widely recognised sources of renewable energy, this definition also includes power generated from biomass, tidal and geothermal sources.
Many governments and several international organizations have pushed for the development of renewable energy sources in response to climate change concerns and in recognition of the national security benefits of diversified energy supplies. In the EU, the Renewable Energy Directive promotes the development of renewable energy and sets renewable energy targets for each member country.
Historically, governmental support has been crucial to the development of renewable energy sources. Many renewable energy projects are riskier or more expensive than traditional energy projects due to one or more features specific to them.