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Wind, solar, and hydroelectricity are three emerging renewable sources of energy.

Renewable energy is energy that is collected from renewable resources, which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services.

Based on REN21's 2017 report, renewables contributed 19.3% to humans' global energy consumption and 24.5% to their generation of electricity in 2015 and 2016, respectively. This energy consumption is divided as 8.9% coming from traditional biomass, 4.2% as heat energy (modern biomass, geothermal and solar heat), 3.9% hydro electricity and 2.2% is electricity from wind, solar, geothermal, and biomass. Worldwide investments in renewable technologies amounted to more than US$286 billion in 2015, with countries such as China and the United States heavily investing in wind, hydro, solar and biofuels. Globally, there are an estimated 7.7 million jobs associated with the renewable energy industries, with solar photovoltaics being the largest renewable employer. As of 2015 worldwide, more than half of all new electricity capacity installed was renewable.

Renewable energy resources exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency is resulting in significant energy security, climate change mitigation, and economic benefits. The results of a recent review of the literature concluded that as greenhouse gas (GHG) emitters begin to be held liable for damages resulting from GHG emissions resulting in climate change, a high value for liability mitigation would provide powerful incentives for deployment of renewable energy technologies. In international public opinion surveys there is strong support for promoting renewable sources such as solar power and wind power. 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. Some places and at least two countries, Iceland and Norway generate all their electricity using renewable energy already, and many other countries have the set a goal to reach 100% renewable energy in the future. For example, in Denmark the government decided to switch the total energy supply (electricity, mobility and heating/cooling) to 100% renewable energy by 2050.

While many renewable energy projects are large-scale, renewable technologies are also suited to rural and remote areas and developing countries, where energy is often crucial in human development. Former United Nations Secretary-General Ban Ki-moon has said that renewable energy has the ability to lift the poorest nations to new levels of prosperity. As most of renewables provide electricity, renewable energy deployment is often applied in conjunction with further electrification, which has several benefits: Electricity can be converted to heat (where necessary generating higher temperatures than fossil fuels), can be converted into mechanical energy with high efficiency and is clean at the point of consumption. In addition to that electrification with renewable energy is much more efficient and therefore leads to a significant reduction in primary energy requirements, because most renewables don't have a steam cycle with high losses (fossil power plants usually have losses of 40 to 65%).

Renewable energy systems are rapidly becoming more efficient and cheaper. Their share of total energy consumption is increasing. Growth in consumption of coal and oil could end by 2020 due to increased uptake of renewables and natural gas.

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Water enters the Arizona spillway during the 1983 floods

The Hoover Dam, once known as Boulder Dam, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the US states of Arizona and Nevada. It was constructed between 1931 and 1936, and was dedicated on September 30, 1935 by President Franklin Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over a hundred lives.

Hoover Dam impounds Lake Mead, and is located near Boulder City, Nevada, a municipality originally created for workers on the construction project, about 30 mi (48 km) south of Las Vegas, Nevada. The dam's generators provide power for public and private utilities in Nevada, Arizona and California. Hoover Dam is a major tourist attraction, and U.S. 93, a heavily travelled road, runs along its crest. In late 2010, traffic was rerouted onto a bypass and the dam roadway was limited to use by visitors.


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Augustin Mouchot (April 7, 1825 – October 4, 1911) was a French inventor of the earliest solar-powered engine, converting solar energy into mechanical steam power.

Mouchot was born in Semur-en-Auxois, France on 7 April 1825. He first taught at the primary schools of Morvan (1845–49) and later Dijon, before attaining a degree in Mathematics in 1852 and a Bachelor of Physical Sciences in 1853. Subsequently, he taught mathematics in the secondary schools of Alençon (1853–62), Rennes and Lycée de Tours (1864–71). It was during this period that he undertook research into solar energy, which led eventually to his obtaining government funding for full-time research.


Did you know?

... that The Clean Tech Revolution: The Next Big Growth and Investment Opportunity, the 2007 book by Ron Pernick and Clint Wilder, argues that commercializing clean technologies is a profitable enterprise that is moving steadily into mainstream business ? As the world economy faces challenges from energy price spikes, resource shortages, global environmental problems, and security threats, clean technologies are seen to be the next engine of economic growth.

Pernick and Wilder highlight eight major clean technology sectors: solar power, wind power, biofuels, green buildings, personal transportation, the smart grid, mobile applications (such as portable fuel cells), and water filtration. Very large corporations such as GE, Toyota and Sharp, and investment firms such as Goldman Sachs are making multi-billion dollar investments in clean technology.




  • "The variability of sun, wind and so on, turns out to be a non-problem if you do several sensible things. One is to diversify your renewables by technology, so that weather conditions bad for one kind are good for another. Second, you diversify by site so they're not all subject to the same weather pattern at the same time because they're in the same place. Third, you use standard weather forecasting techniques to forecast wind, sun and rain, and of course hydro operators do this right now. Fourth, you integrate all your resources — supply side and demand side..." – Amory Lovins
  • "Because the wind blows during stormy conditions when the sun does not shine and the sun often shines on calm days with little wind, combining wind and solar can go a long way toward meeting demand, especially when geothermal provides a steady base and hydroelectric can be called on to fill in the gaps". – Mark Z. Jacobson and Mark A. Delucchi. Scientific American, November 2009, p. 43.

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