Solar Energy – Solar energy is harnessed from the light and heat of the sun’s radiation.
It is one of the renewable energy sources.

How it is harnessed: There are two different ways to capture solar energy: Active Solar and Passive Solar.

Active Solar = Active solar
technologies use electrical equipment like pumps and fans to increase the amount of usable heat in a system. These are then used to convert solar energy into usable light and heat to power systems, or store heat for future use. Active solar is more useful when harnessing large amounts of energy.

Passive Solar = Passive Solar technologies use sunlight for useful energy without the use of electrical equipment. Such technologies convert sunlight into usable energy with little use of other energy sources. Passive solar is more useful when harnessing smaller amounts of energy.

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Wind Energy – Wind energy is harnessed from wind power and can be converted to electricity.
Wind produces only about 1.5% of worldwide electricity use.
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This three-bladed wind turbine is the most common modern design because it minimizes forces related to fatigue.
Wind power consumes no fuel for continuing operation, and has no emissions directly related to electricity production. Operation does not produce carbon dioxide, sulfur dioxide, mercury, particulates, or any other type of air pollution, as fossil fuel power sources do.


Hydroelectric Energy – Hydroelectric energy is harnessed from flowing water, and converts the gravitational potential and kinetic energy of water into electricity. Flowing water is the world’s largest renewable energy source.

How it is harnessed: Dams are built to impede the flow of the water, and depending on the amount of water and the velocity of the flowing water, a certain amount of energy can be harnessed.

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It is particularly useful in hilly or mountainous areas with fast-flowing rivers, and is sustainable as rivers flow continuously. As a result, it is more reliable than wind, wave, or solar power. However, hydroelectric dams have high construction costs and are expensive to maintain.

Nuclear Energy – Energy created in a nuclear reaction is called nuclear energy.
There are two types of nuclear energy: Fusion and Fission. However, fusion is not commercial used at the moment, as it is still being researched and cannot be harnessed. Nuclear energy is considered a renewable energy source.
Nuclear Fission: Fission involves the splitting of the nuclei of atoms. This split causes energy to be released. Uranium is seen as the optimum element used to undergo nuclear fission, and is therefore the main source of fuel used to produce the energy.



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Splitting of Uranium atom




Advantages - Nuclear power is a renewable energy source, and is therefore a possible replacement for finite fossil fuels. Well maintained and constructed nuclear power plants do not pollute the air as fossil fuels do. Furthermore, if scientists were able to eventually harness nuclear energy through fusion, an even more effective source of energy, the world’s problems with fossil fuels could potentially disappear.

Disadvantages – Nuclear power is extremely dangerous, and such technology could be deadly in the wrong hands, for example, if terrorists gained access to nuclear power.
Nuclear explosions release radiation, which is harmful for the environment and people. Meltdowns such as these have happened in the past, and are a major concern.

Fossil Fuels – Fossil fuels, like coal, oil, and natural gas, provide energy to power everything like planes, cars, heat for our homes etc.
Fossil fuels are energy resources that come from the remains of plants and animals. These remains are millions of years old. There are three main fossil fuels: petroleum oil, natural gas, and coal.

Oil and Natural Gas
Sea life is the source of oil and natural gas. These organisms died and were buried in ocean and river sediment. Bacteria cooked these organisms. This produced thick oil. And in hotter regions the cooking process continued for longer and natural gas formed.
Coal
Coal was formed by the same sorts of pressure and temperature as oil and natural gas, but coal comes from the remains of species of ferns that existed about 400 million years ago, trees, and other plants.
Coal is cheap and abundant; there are extensive deposits of it almost everywhere.
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Fossil fuels take million of years to develop under severe conditions. But once we used them, it is gone for ever. Therefore they are nonrenewable resources.
Burning fossil fuels emits carbon dioxide that causes global warming which results in climate change, acid rain and ozone problems.
One of the main uses of fossil fuels it to generate electricity.
Petroleum-based fuels are used for fueling transportation.





Sources:

"Hydroelectric Power - the Effects of Damming." UN Atlas of the Oceans. 1 Dec. 2006. United Nations. 21 May 2008 <http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xNzk4MSZjdG5faW5mb192aWV3X3NpemU9Y3RuX2luZm9fdmlld19mdWxsJjY9ZW4mMzM9KiYzNz1rb3M~>.

"Hydroelectric Power." TVA: Hydroelectric Power. Aug. 2007. Tennessee Valley Authority. 20 May 2008
<http://www.tva.gov/power/hydro.htm>.

Nuclear Energy." Oracle ThinkQuest Library. 01 Apr. 2009 <http://library.thinkquest.org/3471/nuclear_energy.html>.

Profiles--Fossil Fuels." Iowa Public Television. 01 Apr. 2009 <http://www.iptv.org/exploremore/energy/profiles/fossil_fuels.cfm>.

Tyler-Miller, G. "Water Energy FAQ." LENNTECH. 2008. Lenntech Water
Purification and Air Treatment. 19 May 2008
<http://www.lenntech.com/water-energy-FAQ.htm>.

"Wind and Hydropower Technologies Program - Advantages and Disadvantages of Hydropower." Energy Efficiency and Renewable Energy. 09 Aug. 2005. U.S. Department of Energy. 21 May 2008
<http://www1.eere.energy.gov/windandhydro/hydro_ad.html>.