Renewable energy

Renewable energy comes from renewable resources. It is different from fossil fuels as it does not produce as many greenhouse gases and other pollutants as fossil fuel combustion.

People have used traditional wind power, hydropower, biofuel, and solar energy for many centuries, all around the world. The mass production of electricity using renewable energy sources is now becoming more common.

Growth of renewables
From the end of 2004, worldwide renewable energy capacity grew at rates of 10–60% annually for many technologies. For wind power and many other renewable technologies, growth sped up in 2009 relative to the previous four years. More wind power was added during 2009 than any other renewable technology. However, grid-connected PV increased the fastest of all renewables technologies, with a 60% annual average growth rate.  

Projections vary, but scientists have advanced a plan to power 100% of the world's energy with wind, hydroelectric, and solar power by the year 2030.

Wind power market grows 
Main articles: Wind farm and List of large wind farms.

Wind power capacity has expanded quickly to 336 GW in June 2014, and wind energy production was about 4% of total worldwide electricity usage, and growing fast.  Wind power is widely used in European countries, and more recently in the United States and Asia. Wind power accounts for approximately 19% of electricity generation in Denmark, 11% in Spain and Portugal, and 9% in the Republic of Ireland. These are some of the largest wind farms in the world, as of January 2010: 
 

A wind farm is a group of wind turbines in the same location used for production of electricity. A large wind farm may consist of several hundred individual wind turbines distributed over an extended area, but the land between the turbines may be used for agricultural or other purposes. A wind farm may also be located offshore.

World's largest PV power plants 

Solar photovoltaic cells convert sunlight into electricity and many solar photovoltaic power stations have been built, mainly in Europe. As of December 2010, the largest photovoltaic (PV) power plants in the world are the Sarnia Photovoltaic Power Plant (Canada, 97 MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW), Finsterwalde Solar Park (Germany, 80.7 MW), Rovigo Photovoltaic Power Plant (Italy, 70 MW), Olmedilla Photovoltaic Park (Spain, 60 MW), the Strasskirchen Solar Park (Germany, 54 MW), and the Lieberose Photovoltaic Park (Germany, 53 MW). Larger power stations are under construction, some proposed will have a capacity of 150 MW or more.

Many of these plants are integrated with agriculture and some use innovative tracking systems that follow the sun's daily path across the sky to generate more electricity than conventional fixed-mounted systems. There are no fuel costs or emissions during operation of the power stations.

New generation of solar thermal plants 

Large solar thermal power stations include the 354 megawatt (MW) Solar Energy Generating Systems power installation in the USA, Solnova Solar Power Station (Spain, 150 MW), Andasol solar power station (Spain, 100 MW), Nevada Solar One (USA, 64 MW), PS20 solar power tower (Spain, 20 MW), and the PS10 solar power tower (Spain, 11 MW). The 370 MW Ivanpah Solar Power Facility, located in California's Mojave Desert, is the world’s largest solar thermal power plant project currently under construction.

The solar thermal power industry is growing fast with 1.2 GW under construction as of April 2009 and another 13.9 GW announced globally through 2014.  Spain is the epicenter of solar thermal power development with 22 projects for 1,037 MW under construction, all of which are projected to come online by the end of 2010. In the United States, 5,600 MW of solar thermal power projects have been announced. In developing countries, three World Bank projects for integrated solar thermal/combined-cycle gas-turbine power plants in Egypt, Mexico, and Morocco have been approved.

Variable renewable energy
Variable renewable energy is a renewable energy source that is non-dispatchable due to its fluctuating nature, like wind power and solar power, as opposed to a controllable renewable energy source such as hydroelectricity, or biomass, or a relatively constant source such as geothermal power or run-of-the-river hydroelectricity. Critics of wind and solar power warn of their variable output, but many studies have shown that the grid can cope, and it is doing so in Denmark and Spain.

The International Energy Agency says that there has been too much focus on issue of the variability. Its significance depends on a range of factors which include the market penetration of the renewables concerned, the balance of plant, and the wider connectivity of the system, as well as demand side flexibility. Variability will rarely be a barrier to increased renewable energy deployment. But at high levels of market penetration it requires careful analysis and management.

Ethanol for transportation 
Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18 percent of the country's automotive fuel. As a result, Brazil, which years ago had to import a large share of the petroleum needed for domestic consumption, recently reached complete self-sufficiency in oil.  

Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and motor vehicle manufacturers already produce vehicles designed to run on much higher ethanol blends. Ford, DaimlerChrysler, and General Motors Corporation are among the automobile companies that sell “flexible-fuel” cars, trucks, and minivans that can use gasoline and ethanol blends ranging from pure gasoline up to 85% ethanol (E85). By mid-2006, there were approximately six million E85-compatible vehicles on U.S. roads.

Related pages

Notes

Other websites 

 The Climate Change Guide easy-to-understand information on Renewable energy
 US National Renewable Energy Laboratory (NREL). 
  EPA uses onsite renewable technologies
 New World Record achieved in solar cell technology 
 Energy conservation at home in Simple Wikibooks 
  Renewables 2011: Global Status Report 

 
Environment
Green politics