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Geothermal Energy

Geothermal energy is the heat energy that occurs naturally in the earth. The energy is recovered from the heat of the earth's core. In nature, geothermal heat shows up in the form of volcanoes, hot springs and geysers. The heat itself is derived from radioactive decay beneath the earth's surface. In certain locations, it is concentrated and is close enough to surface waters to be brought to the surface for many different purposes. When it is above 150 degree Celsius, it is considered hot enough to be used to generate electricity and heat in Iceland.

    For thousands of years, humans have used naturally occurring hot springs for bathing. More recently, geothermal energy has been used to generate electricity, and to provide heat for homes and industries. Geothermal energy is a versatile and reliable source of heat and electricity which generally produces none of the greenhouse gases associated with the combustion of fossil fuels. Unfortunately, the best geothermal resources are concentrated in areas of volcanic activity and are not widely distributed. California, Iceland, Italy, New Zealand and Japan are all areas where geothermal energy is used on a significant scale.

In Iceland there are mainly two sources of energy; geothermal energy and hydro power . Geothermal heat is one of Iceland's greatest natural resources. The Icelandís capital has enjoyed this valuable power source for more than 60 years. Icelanders are very lucky to have this geothermal heat. For that reason central heating and warm water are rather inexpensive. 

 

The geothermal heat is mostly used to heat fresh water which, when hot, can be utilized directly for central heating. 89% of all the houses in Iceland are heated this way (see Figure 1). But the geothermal water is also used in many other ways. It is used in swimming pools, for soil warming, fish farming, drying of timber and wool, animal husbandry etc.

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1. Geothermal energy is extracted for heating and electricity generation from natural steam, hot water, or hot dry rocks in the Earth's crust.

2. The water is pumped down through a injection well where it passes through joints in the hot rocks. It rises to the surface through a recovery well and may be converted to steam.

3. A mixture of steam and geothermal brine is transported from the wells to a central separation station.

4. After being separated from the brine, the steam is piped through moisture separators to steam heat exchangers inside the plant building.

5. Then the steam can be piped to steam turbines for co-generation of electricity. Unutilized steam is released through a steam exhaust.

6. In the steam heat exchangers, the steam is cooled under pressure into condensate.

7. The heat is then transferred to cold fresh water in condensate heat exchangers. The condensate cools down in the process to 20 degrees C.

8. Separated geothermal brine has its heat transferred to cold fresh water by geothermal brine heat exchangers. Since the mineral-rich geothermal brine causes scaling that coats the heat exchanger pipes, steel particles are allowed to circulate in the stream, impacting against the pipes to remove any scaling as it occurs.

8.Cold water is then pumped from wells to a storage tank .

9. From the storage tank, it is pumped to the heat exchangers where its temperature is raised to 85 degrees C to 90 degrees C.

10. It is then passed through deaerators where it is boiled at low vacuum pressure to remove dissolved oxygen and other gases that cause corrosion after being heated. Thus cooling the water to 82 degrees C to 85 degrees C.

The blue lagoon is located about 40 minutes from the capital Reykjavik. The lagoon is a pool of natural mineral rich geothermal sea water in the middle of a lava field. The lagoon gets is vivid blue color from the blue-green algae and white silica mud. The Lagoon is located beside Svartsengi a geothermal power plant, which pumps the mineral laden water from up to 2 km from beneath the earths surface. 

This water, which is about 240 degrees C, passes through several processes to generate electricity and then heats water that in turn heats 89% of Icelandic homes. The extra run off forms the blue lagoon which is about 35 degrees C to about 40 degrees C year round. The blue lagoon is known as a therapeutic bathing pool. The lagoon has proven health benefits. Scientists say bathing in the lagoon has positive effects on psoriasis and eczema. The lagoon is a very popular tourist attraction, mainly because of the many health benefits. The Blue Lagoon produces and markets the Blue Lagoon skin care products, based on active natural ingredients from the Blue Lagoon.

By M. Corbin

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References

Utilization of Energy in Iceland .

http://www.ml.is/hca_ml/energy.htm

Water & Energy .

http://landey.bv.rvk.is/vefur/owa/disp.birta?pk=1988

Blue Lagoon .

http://www.bluelagoon.is/index_en.ehtm

Geothermal Resources in Iceland.

http://www.energy.rochester.edu/is/reyk/

Energy Facts: Geothermal Energy .

http://www.iclei.org/efacts/geotherm.htm

Renewable Energy: Geothermal.

http://atschool.eduweb.co.uk/dcastle/geo.html

Iceland the land of Fire & Ice . <http://www.belgarath.demon.co.uk/travel/iceland/

"Nature in Action ~on the capitals door." Iceland (1999):pages 8-9

"Blue Lagoon~Geothermal Spa." Visit Iceland 2001: page 16

Zukowski, Helena. "Alice in Iceland." The Sunday Daily News (Halifax) 8 Apr. 2001