Imagine living thousands of miles from any other other civilization and your only option to produce energy would be importing the raw materials from any other countries. Now picture that you have in your own country you also have an active volcano. This means that your power and electricity production are very limited; luckily for you the fact that you have an active volcano in your country is a living proof that below the Earth’s crust, there is a layer of hot and molten rock called magma. Heat is continually produced there, mostly from the decay of naturally radioactive materials such as uranium and potassium. [3]. Besides the magma ; pockets of hot water and steam can be found deep underground. Hot water and steam can be piped up through underground wells and used to generate electricity in a power plant all of this is possible thanks to a Geothermal power plant [1]. There are Three different types of geothermal power plants:
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Dry steam plants. Hot steam is piped directly from geothermal reservoirs into generators in the power plant. The steam spins turbines, which generate electricity.[1]
Figure 1 : model of a Dry steam system
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Flash steam plants. Water that’s between 300 and 700 degrees Fahrenheit (148 and 371 degrees Celsius) is brought up through a well. Some of the water turns to steam, which drives the turbines. When the steam cools it condenses back into water and is returned to the ground[1].
Figure 2 : model of a flash steam system
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Binary cycle plants. Moderately hot geothermal water is passed through a heat exchanger, where its heat is transferred to a liquid (such as isobutene) that boils at a lower temperature than water. When that fluid is heated it turns to steam, which spins the turbines[1].
Figure 3 : model of a Binary cycle system
Any of these types of power plants make it possible to have electricity generated without needing to import raw materials. Iceland is a pioneer in the use of geothermal energy for space heating. Geothermal power facilities currently generate over 25% of the country’s total electricity production [2]Five major geothermal power plants exist in Iceland. In addition, geothermal heating meets the heating and hot water requirements of approximately 87% of all buildings in Iceland. [4]
The following are the five largest power stations in Iceland[4].
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Hellisheiði Power Station (303 MW)
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Nesjavellir Geothermal Power Station (120 MW)
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Reykjanes Power Station (100 MW)
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Svartsengi Power Station (76.5 MW)
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Krafla Power Station (60 MW)
All of these are geothermal power plants,and among them Hellisheiði Power Station is the largest geothermal power station in the world. Each one of there have a significant contribution on Iceland’s power generation . Being able to have a produce energy from a constant natural resource, allows companies and countries to decrease their dependency on fossil fuels , which consequently results in a positive impact on the environment . Enhanced geothermal systems, have life-cycle global warming emission of approximately 0.2 pounds of carbon dioxide equivalent per kilowatt-hour [5].To put this into context, estimates of life-cycle global warming emissions for natural gas generated electricity are between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour and estimates for coal-generated electricity are 1.4 and 3.6 pounds of carbon dioxide equivalent per kilowatt-hour [5].
Source
[1] http://science.howstuffworks.com/environmental/energy/geothermal-energy1.htm
[2] http://www.nea.is/geothermal/
[3] http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/how-geothermal-energy-works.html#.VFJfi74htOR
[4] http://en.wikipedia.org/wiki/Geothermal_power_in_Iceland
[5] http://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-geothermal-energy.html#.VFODSTTF9L0