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Introduction
In physics, energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J).
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, and the internal energy contained within a thermodynamic system. All living organisms constantly take in and release energy.
Due to mass–energy equivalence, any object that has mass when stationary (called rest mass) also has an equivalent amount of energy whose form is called rest energy, and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy.
Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The Earth's climate and ecosystems processes are driven by the energy the planet receives from the Sun (although a small amount is also contributed by geothermal energy). (Full article...)
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There are many motivations to improve energy efficiency. Reducing energy use reduces energy costs and may result in a financial cost saving to consumers if the energy savings offset any additional costs of implementing an energy efficient technology. Reducing energy use is also seen as a solution to the problem of reducing carbon dioxide emissions. According to the International Energy Agency, improved energy efficiency in buildings, industrial processes and transportation could reduce the world's energy needs in 2050 by one third, and help control global emissions of greenhouse gases.
Energy efficiency and renewable energy are said to be the twin pillars of sustainable energy policy and are high priorities in the sustainable energy hierarchy. In many countries energy efficiency is also seen to have a national security benefit because it can be used to reduce the level of energy imports from foreign countries and may slow down the rate at which domestic energy resources are depleted.
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Photo credit: Andreas Tille
Geysers erupt periodically due to surface water being heated by geothermal heat.
Did you know?
- The Stuart Shale Oil Plant (pictured) in Australia was in operation only five years?
- Atlantic LNG Company of Trinidad and Tobago operates the world's largest LNG train?
- Despite projections of producing four times as much power as it used in heating, the Riggatron fusion reactor was never built due to a lack of funding?
- In the late 1980s, as many as 50 percent of Argentina's thermal power plants had to be shut down due to lack of maintenance, causing a supply crisis?
- Kashiwazaki-Kariwa Nuclear Power Plant in Japan, the largest nuclear power plant in the world, was shut down after being hit by the Chūetsu offshore earthquake in July 2007?
- The world's largest surface oil shale pyrolysis reactor is Petrosix, operated by the Brazilian oil company Petrobras?
- Russia plans to build several floating nuclear power stations?
- Shale gas, a form of natural gas extracted from shale, may also refer to oil shale gas?
Selected biography
In recognition of Watt's achievements, the SI unit of power, the watt, is named after him.
James Watt was born on 19th of January, 1736 in Greenock, a seaport on the Firth of Clyde. His father was a shipwright, shipowner and contractor, while his mother, Agnes Muirhead, came from a distinguished family and was well-educated. Both were Presbyterians and strong Covenanters. Watt attended school irregularly and instead was mostly schooled at home by his mother.
After studying instrument-making for a year in London, the University of Glasgow offered him the opportunity to set up a small workshop within the university. It was established in 1757. After four years, Watt began to experiment with steam, finally producing a working model steam engine in 1765. Strapped for resources to develop a full-scale engine, Watt was forced to take up employment as a surveyor for eight years. Finally, in 1776, the first engines were installed and working in commercial enterprises.
After further improvements, Watt and foundry owner Matthew Boulton established Boulton and Watt in 1794 to exclusively manufacture steam engines. By 1824 it had produced 1,164 steam engines having a total nominal horsepower of about 26,000.
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Quotations
- "Without radical international measures to reduce carbon emissions within the next 10 to 15 years, there is compelling evidence to suggest we might lose the chance to control temperature rises. Failure to act will make an increase of between 2 and 5 degrees [3.6 - 9°F] in average temperatures almost inevitable." – Tony Blair, 2006
- "The question is not whether climate change is happening or not, but whether, in the face of this emergency, we ourselves can change fast enough." – Kofi Annan, 2006
- "I promise you a day will come when our children and grandchildren will look back and they will ask one of two questions. Either they will ask, 'What in God's name were they doing? Didn't they see the evidence?' Or, they may look back and say 'How did they find the uncommon moral courage to rise above politics and redeem the promise of American democracy?'" – Al Gore, 2007, on global warming.
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