Renewable energy is energy generated from natural resources — such as sunlight, wind, rain, tides and geothermal heat — which are renewable (naturally replenished).
In 2006, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood-burning.
Hydroelectricity was the next largest renewable source, providing 3% (15% of global electricity generation), followed by solar hot water/heating, which contributed 1.3%.
Modern technologies, such as geothermal energy, wind power, solar power, and ocean energy together provided some 0.8% of final energy consumption.
Geothermal energyis energy obtained by tapping the heat of the earth itself, usually from kilometers deep into the Earth's crust. Where hot underground steam or water can be tapped and brought to the surface it may be used to generate electricity. Such geothermal power sources exist in certain geologically unstable parts of the world such as Chile, Iceland, New Zealand, United States, the Philippines and Italy. The world's largest geothermal power installation is The Geysers in California.
Wind poweris the conversion of wind energy into a useful form, such as electricity, using wind turbines.It is growing at the rate of 30 percent annually and is widely used in several European countries and the United States. It is renewable and produces no greenhouse gases during operation, such as carbon dioxide and methane.
Solar energy refers to energy that is collected from sunlight. Solar thermal power stations operate in the USA and Spain.
Solar energy can be applied in many ways, including to:
Ø generate electricity using photovoltaic solar cells.
Ø generate electricity using concentrated solar power.
Ø generate electricity by heating trapped air which rotates turbines in a Solar updraft tower.
Ø generate electricity in geosynchronous orbit using solar power satellites.
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| “In one hour more sunlight falls on the earth than what is used by the entire population in one year.” |
Ø heat and cool air through use of solar chimneys.
Ø heat buildings, directly, through passive solar building design.
Ø heat foodstuffs, through solar ovens.
Ø heat water or air for domestic hot water and space heating needs using solar-thermal panels.
Ø solar air conditioning
Energy in water (in the form of kinetic energy, temperature differences or salinity gradients) can be harnessed and used.
Forms of water energy:
Ø Hydroelectric energy is a term usually reserved for large-scale hydroelectric dams. Examples are the Grand Coulee Dam in Washington State and the Akosombo Dam in Ghana.
Ø Micro hydro systems are hydroelectric power installations that typically produce up to 100 kW of power. There are many of these installations around the world, includin g several delivering around 50 kW in the Solomon Islands.
Ø Damless hydro systems derive kinetic energy from rivers and oceans without using a dam.
Ø Ocean energy describes all the technologies to harness energy from the ocean and the sea.
| “Fossil fuels are depleted at a rate that is 100,000 times faster than they are formed.” |
Biofuel industries are expanding in Europe, Asia and the Americas. Recent technology developed at Los Alamos National Lab even allows for the conversion of pollution into renewable bio fuel. Agrofuels are biofuels which are produced from specific crops, rather than from waste processes such as landfill off-gassing or recycled vegetable oil.
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. Ethanol fuel is also widely available in the USA.