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Renewable energy (also called green energy) is energy made 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 .
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.
Historically, humans have harnessed biomass-derived energy since the advent of burning wood to make fire, and wood remains the largest biomass energy source today. [ 50 ] [ 51 ] However, low tech use of biomass, which still amounts for more than 10% of world energy needs may induce indoor air pollution in developing nations [ 52 ] and results ...
In 1802 lectures to the Royal Society, Thomas Young was the first to use the term energy to refer to kinetic energy in its modern sense, instead of vis viva. [3] In the 1807 publication of those lectures, he wrote, The product of the mass of a body into the square of its velocity may properly be termed its energy. [4]
Size comparison of modern wind turbines Wind energy generation by region. As the 21st century began, fossil fuel was still relatively cheap, but rising concerns over energy security, global warming, and eventual fossil fuel depletion led to an expansion of interest in all available forms of renewable energy. The fledgling commercial wind power ...
Data from the International Energy Agency (IEA) and International Renewable Energy Agency (IRENA) also revealed that a further 40 countries generated at least 50 per cent of the electricity they ...
At the national level, at least 30 nations around the world already have renewable energy contributing more than 20 percent of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond. While many renewable energy projects are large-scale, renewable technologies are also suited ...
In 2011, a report by the International Energy Agency found that solar energy technologies such as photovoltaics, solar hot water, and concentrated solar power could provide a third of the world's energy by 2060 if politicians commit to limiting climate change and transitioning to renewable energy.