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What is Geothermal energy?• The word Geothermal comes from the Greek word geo (Earth) and therme (heat).• Geothermal energy is the heat from the earth.• It’s source lies 6,500km beneath the Earth’s surface, Core containing hot magma.
• Surrounding the core is the mantle, and outer layer is the crust.• The crust is not a solid shell but is broken into pieces called plates, Magma comes close to Earth’s surface near the edges of these plates.• Rocks and water beneath the surface around these region absorbs heat of this magma.• We can dig wells and can use this heat for various purposes.
History of Geothermal energy• The use of geothermal energy for heating purpose is not new.• Ancient people used it for heating and bathing through hot springs.• Using geothermal energy to produce electricity is a new industry• A group of Italians first used it in 1904. The Italians used the natural steam erupting from the Earth to power a turbine generator.
Finding Geothermal Energy• Some visible features of geothermal energy are volcanoes, hot springs, geysers, and fumaroles.• But we cannot see most of the resources as they are deep underground.• Exploration is done by digging well and testing temp deep underground.• Most active resources are found along edges of tectonic plates.
• An area called Ring of fire has most of geothermal activities, this area borders the Pacific Ocean.
Uses Direct use: geothermal heating and heat pumps Indirect use: Electricity production
Direct use• Heat is directly used.• Heat is extracted from low temperature source, <150 degree Celsius.• It can be used for space heating, industrial processes, drying crops, hot water supply, melting snow.• For space heating, Heat Pump is used.• It uses little energy for heating thus saves money and reduce pollution.
Indirect use: electricityproduction• Source temperature is higher than 150 degree Celsius.• Deep wells are drilled and steam from reservoir is used to drive turbines and produce electricity.
Types of power plants Flashed steam plant Dry steam plant Binary power plant Hybrid power plant
Flashed steam plant• Hot water at high pressure when released from deep reservoir forms high pressure steam (flashed steam).• This steam drives turbines.• This is most common type of plant operating today.
Dry steam plant• Usually geysers are the main source of dry steam.• Reservoirs which produce steam with small quantity of water use this type of plant.• A rock catcher is used to protect turbine from rocks coming along with steam.
Binary power plant• In this the geothermal water is passed through a heat exchanger where its heat is transferred to a secondary liquid.• Liquids having lower boiling point are used as secondary liquid such as isobutene, isopentane or ammonia–water mixture.• The vapour of secondary liquid are used to rotate turbines.• The binary system is useful in geothermal reservoirs which are relatively low in temperature.• Heat loss is minimum as system is completely closed.
• Hot water is immediately recycled back into the reservoir.• The working fluid is also condensed back to the liquid and used over and over again.
Hybrid power plant• It uses both boiling water as well as steam.• Steam is directly is used as used in flashed steam plant.• While energy of hot water is used through secondary liquid as used in Binary system.
Enhanced geothermal system• It refers to a variety of engineering techniques used to artificially create hydrothermal resources.• In this the drilling is done in hot dry rocks, and cold water at high pressure is pumped in.• As water travels through cracks in hot dry rock it’s temperature is increased.• Now this very hot water is collected back through another drilled hole, converted into steam and used.• This is very promising technology but is still in it’s development stage.• Risk of seismic activities could increase, due to artificially fracturing the underground rocks.
Advantages• Geothermal energy does not produce any pollution, and does not contribute to the greenhouse effect.• The power stations are compact, so there is not much impact on the environment.• No fuel is needed.• Once youve built a geothermal power station, the energy is almost free.• It may need a little energy to run a pump, but this can be taken from the energy being generated.
Cost, Price and Challenges• Since it does not use any fuel hence it’s cost is unaffected by price fluctuations.• Primary prices are bit high but once the capital costs have been recovered price of power can decrease.• Most of the cost is related to resource exploration and plant construction.• Drilling Costs alone account for as much as one- third of total plant cost because rocks in geothermal areas are usually extremely hard and hot.• Geothermal power plants must be located near a reservoir because it difficult to transport steam or hot water over distances.
Barriers• Finding a suitable build location.• exploration stage can be extremely capital intensive and of high-risk.• Some areas of land may have the sufficient hot rocks to supply hot water to a power station, but many of these areas are located in harsh areas of the world (near the poles), or high up in mountains.• Harmful gases can escape from deep within the earth.
Geothermal Energy In World• 10,715 megawatts (MW) of geothermal power in 24 countries is online.• The United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants.• The Philippines is second highest producer of geothermal power in the world, with 1,904 MW of capacity online; geothermal power makes up approximately 18% of the countrys electricity generation
• There is expected rise to 18,500 MW by 2015 as large no of projects are under construction.
Geothermal Energy In India• India has about 10000 MWe of geothermal power potential which ean be used.• More than 300 hot spring locations have been identified by Geological survey of India, and are grouped into geothermal provinces of India.
Geothermal Energy and theEnvironment• Geothermal energy does little damage to the environment, with very less CO2 emission.• Transportation of fuel is not required as they are located on top of there fuel.• Geothermal has minimal land requirements. Geothermal plants use 404 square meters per GWh versus 3,622 and 1,335 square kilometres for coal facilities and wind farms respectively.• They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal power plants.• It is one of the most eco-friendly technology.
References•• Www.Wikipedia.com• The NEED Project , www.NEED.org• Www.indiaenergyportal.org• Www.worldenergy.org