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Streda, 22. januára 2020
Energy sources
Dátum pridania: 25.11.2002 Oznámkuj: 12345
Autor referátu: aradvan
 
Jazyk: Angličtina Počet slov: 1 085
Referát vhodný pre: Stredná odborná škola Počet A4: 3.7
Priemerná známka: 2.97 Rýchle čítanie: 6m 10s
Pomalé čítanie: 9m 15s
 
Energy is the lifeblood of modern industrial society. Important as it is, energy was taken for granted for many years.
Most of the electricity we use comes from four sources: coal, hydroelectric power, oil, and nuclear power.
Most experts agree that at the current rate of consumption, the proven reserves of crude oil will last only about 60 years. Making matter worse, any increase in the rate of oil consumption would drastically cut the lifespan of oil. At the current rate of usage, proven global reserves of natural gas would last about 100 years.
Coal is the world’s most abundant nonrenewable fossil fuel. World proven reserves will last about 600 years at the current rate of consumption. Coal will probably play a large role in the near term, for it can also be used to make liquid fuels to power our transportation systems and can be converted into a synthetic natural gas for home heating.
Oil and natural gas supplies are fast on the decline and in need of a substitute. The world is also suffering the early symptoms of global warming caused by air pollution. Both trends suggest the need for alternative energy sources. Two major groups exist to pick from -nonrenewables and renewables.
Some nonrenewable energy sources may have a place in the immediate future. Nuclear reactors are fueled by uranium-235, whose nuclei split when they are struck by neutrons. This process, fission, releases an enormous amount of energy. Nuclear fuels pass through a complex cycle from mining to waste disposal, at each stage of the cycle radioactive materials can escape, either by accident or through normal operations.
Nuclear power offers many advantages over coal and oil. It produces very little air pollution, less land is disturbed by mining, the cost of transporting nuclear fuels is lower than of coal.
The major problems with nuclear power are disposal of radioactive wastes, contamination of the environment, thermal pollution, health impacts from radiation, limited supplies of uranium ore, low social acceptability, high construction costs, questionable reactor safety, lack of experience with the technology.
The proposal of breeder reactor is getting around the problem of limited fuel supply. Besides producing electricity, the breeder reactor makes fissionable plutonium-239 from the abundant uranium-238.
Another proposed energy system is fusion power.
 
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