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GEOTHERMAL ENERGY

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WHAT IS GEOTHERMAL ENERGY?

The energy that originates from the core of the earth,

where temperatures are about 4000 degree

centigrade is called geothermal energy.

Electrical power generating capacity from

geothermal resource is about 7,704 mega watt.

Geothermal power is growing steadily at a rate of

about 8.5% per year.

These energy are extracted from various geothermal

fields.

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ITS ORIGIN

Geothermal energy is the heat that originates from the core of the earth.

This heat occurs from a combination of two sources, like:-

a) heat produced by gravitational collapse.

b) heat produced by radio active decay of various isotopes.

The core is surrounded by mantle which contains semi-fluid material called magma.

Mantle is covered by crust, the temperature in the crust increases with depth till the core of the earth.

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APPLICATIONS

Direct heat use:- Geothermal energy with low and moderate temperature

hydrothermal fluids can be used as direct heat source for space and water heating, for industrial process like food industry, crop drying, chemical industries, aquaculture agricultural process and space heating of glass houses.

Electric power generation:-

If temperatures are high enough above 90 degree centigrade the preferred use of geothermal energy is generation of electricity. It is used for base load power generation. Electricity 1st generated from geothermal steam is at Italy on 1904.Geysers are main source of this geothermal energy.

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ADVANTAGES

Reliable source

Available 24 hours per day

Availability is independent of weather.

No extra storage facility required

Geothermal plants require less area.

Non-conventional source of energy.

Causes very less or no pollution.

Have low gestation period.

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DISADVANTAGES

Energy available as low grade heat.

Subsidence of land due to extraction of heated

ground water.

Geothermal fluid causing land and air pollution.

Drilling operation leads to noise pollution.

Transportation problem.

Corrosive and abrasive geothermal fluid reduces life

of the plants.

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TYPES OF GEOTHERMAL RESOURCES

HYDRO-THERMAL RESOURCES.

GEO-PRESSURED.

HOT-DRY ROCK.

MAGMA.

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HYDRO-THERMAL RESOURCES

Hydro-thermal resource arise when underground water has access to high temperature porous rocks, capped by solid rock. The water trapped in the underground reservoir is heated by surrounding rock. This heat is supplied by magma by upward conduction. This forms a giant underground boiler. Hot water escapes through fissures in the rock and form hot springs or geysers. Sometimes escapes through cracks called fumaroles. These resources are located at shallow to moderate depth.

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TYPES OF HYDRO-THERMAL RESOURCES

Vapour-dominated (dry steam system).

Liquid-dominated (wet steam system).

Hot water resource.

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GEO-PRESSURED RESOURCES

Hot salty water reservoirs at moderately high temperatures under great pressure are found at depth of 3-6 km is called geo-pressured resources.

These contain significant amount of dissolved methane gas.

Three types of energy produced are

1-Thermal energy

2-Mechanical energy .

3-Chemical energy.

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HOT DRY ROCK RESOURCES

Recovery of heat from hot dry rock involves forming a man-made reservoir by drilling deep into hot rocks and then cracking it to form deep fractures.

These method is more easily accessible.

Potential is quite high.

Hydraulic fracturing process is adopted.

This technique was 1st tested at caldera, US.

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MAGMA RESOURCES

At some places molten rock at temperatures 650-1200 degree centigrade occurs at depth of 5-10 km forming magma resources.

They appear in the vicinity of recently occurring volcanic activity.

Special drilling technology is required.

Very high temperature and large volume make magma a huge potential energy source.

Magma drilling technology has not been developed as yet.

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EXPLORATION AND DEVELOPMENT

Efforts are made to develop procedures for

forecasting geothermal reservoir performance. the

procedures include:-

1. Rate of upward heat flow in the ground.

2. Chemical composition of surface and ground water.

3. Electrical resistivity of the underground

4. Seismic measurements.

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GEO-THERMAL ENERGY IN INDIA

The geothermal provinces include:-

Himalayas, Sohana, West-coast, Son-Narmada-Tapi, Godavari and Mahanadi.

Geothermal reservoirs for power generations are located at Tattapani in chhatisgarh, Puga valley of ladakh, Manikaran HP.

Direct heat pilot plant has also been established at various places.

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CONCLUSION

Geothermal fields lend themselves to staged development.

Exploratory drilling and modern production technology is used.

It is not as renewable as solar or wind energy.

Geothermal energy used for small scale power generation and thermal applications.

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