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Essay on Geothermal Energy
Essay Contents:
- Essay on the Introduction to Geothermal Energy
- Essay on the Important Aspects of Geothermal Energy
- Essay on the Advantages and Disadvantages of Geothermal Energy
- Essay on the Applications of Geothermal Energy
- Essay on Geothermal Energy in India and Abroad
Essay # 1. Introduction to Geothermal Energy:
Geothermal energy is primarily heat energy from earth’s own interior. The word “Geothermal” comes from the Greek words ‘geo’ meaning earth and ‘thermal’ meaning heat.
i. It is classified as renewable because the earth’s interior is and will continue in the process of cooling for the indefinite future. Hence, geothermal energy from the earth’s interior is almost inexhaustible as solar or wind energy, so long as its sources are actively sought and economically tapped.
ii. As we travel down earth’s surface radially, there exists a temperature gradient of 0.03°C per metre. Thus a 30°C increase in temperature can be obtained per kilometre depth from the earth crust. There are many local hot spots just below the surface where the temperatures are much higher than expected.
Ground water, when comes into contact with hot spots, either dry or wet steam is fanned. By drilling holes to these locations, hot water and steam can be tapped and these can be used for power generation or space heating.
iii. Geothermal energy is present over the entire earth’s surface except that it is nearer to the surface in the ‘volcanic areas’.
iv. Heat transfer from the earth’s interior is by three primary means:
1. Direct heat conduction,
2. Rapid injection of ballistic magma along natural rifts penetrating deep into earth’s mantles.
3. Bubble-like magma that buoys upwards towards the surface.
Essay # 2. Important Aspects of Geothermal Energy:
Following are the important aspects about geothermal energy:
a. Form of Energy:
Thermal energy’ in the form of hot water, steam, geothermal brine, mixture of these fluids.
b. Availability:
i. Generally available deep inside the earth at a depth more than about 80 km. Hence, generally not possible to extract.
ii. In a few locations in the world, deposits are at depths of 300 to 3000 m. Such locations are called Geothermal fields.
c. Method of Extraction:
Deep production wells are drilled in the geothermal fields. The hot steam/ water/brine is extracted from the geothermal deposits by production wells, by ‘pumping’ or by ‘natural pressure’.
d. Geothermal Fluids:
i. Hot water;
ii. Hot brine;
iii. Wet steam;
iv. Mixture of above.
e. Range of Geothermal Power Plants Installed Capacity:
5 MW to 400 MW.
f. Average Geothermal Gradient:
30°C per 1000 m length.
g. Geothermal Energy Released through Earth’s Crust:
About 0.06 W/m2.
h. Total Geothermal Reserves in the Earth:
4 x 1024 MJ(Estimated).
i. Renewable Energy Deposits Available for Use in Upper 3 km Zone:
4 x 1015 MJ (Estimated).
j. Rate at which the Renewable Energy can be Tapped for Production of Electricity:
2 x 1012 to 10 x 1012 MJ/year (Estimated).
k. Types of Geothermal Energy Deposits:
i. Hydrothermal: Hot water and steam, hot brine.
ii. Petro thermal: Hot dry rock (HDR).
Essay # 3. Advantages and Disadvantages of Geothermal Energy:
Advantages of Geothermal Energy:
a. Geothermal energy is cheaper.
b. It is versatile in its use.
c. It is the least polluting as compared to other conventional energy sources.
d. It is amenable for multiple uses from a single resource.
e. Geothermal power plants have the highest annual load factors of 85 per cent to 90 per cent compared to 45 per cent to 50 per cent for fossil fuel plants.
f. It delivers greater amount of net energy from its system as compared to other alternative or conventional systems.
g. Geothermal energy from the earth’s interior is almost as inexhaustible as solar or wind energy, so long as its sources are actively sought and economically tapped.
Disadvantages of Geothermal Energy:
a. Low overall power production efficiency (about 15% as compared to 35 to 40% for fossil fuel plants).
b. Drilling operation is noisy.
c. Large areas are needed for exploitation of geothermal energy.
d. The withdrawal of large amounts of steam or water from a hydro-thermal reservoir may result in surface subsidence or settlement.
Essay # 4. Applications of Geothermal Energy:
The various applications of geothermal energy are:
a. Generation of electric power.
b. Space heating for buildings.
c. Industrial process heat.
d. Crop drying.
e. Plastic manufacture.
f. Paper manufacture.
g. Mushroom culture.
h. Timber seasoning.
i. Production of salt from sea.
j. Sewage heat treatment.
k. Greenhouse cultivation using discharge from a geothermal field.
Essay # 5. Geothermal Energy in India and Abroad:
Some progress has been made in India on tapping geothermal energy on a commercial scale. Engineers from the Geological Survey of India have drilled about 50 shallow wells for steam in the Puga valley of the Ladakh region in Jammu and Kashmir. It may be possible to operate a 5 MW power station at the site.
The Puga valley at an altitude of 4500 metres above sea level has the most promising geothermal field. The area extends to about 40 square kilometres out of which 5 sq. km is active. A combination of wet and dry steam to the tune of 170 tonnes of hot water per hour and 20 tonnes/hour of dry steam (superheated steam suitable for running steam turbines) is available.
This is enough to run a small power station to light the homes of local population. The geothermal heat can also be used for space heating in the Puga valley as the temperature in this area, especially during winter months, goes down to 35 degrees below freezing point.
There are no other energy sources in Ladakh region and coal, petroleum etc. have to be transported from Srinagar. It can also be used for poultry farming, mushroom cultivation and pashmina wool processing which need a warmer climate. In addition, there are good deposits of borax and sulphur in this area. Sulphur in elemental form is found only in this region in the whole of India.
There are many hot water springs in India. Hot water springs represent heat energy coming out of the earth from a large body of molten rock that has been pushed up into upper crust of the earth by geological forces. In North they occur in Ladakh and Himachal Pradesh.
In western parts they are found in the Cambay region of Gujarat and Maharashtra. . They are also found in the Singhbhum region of Bihar while there are some in Assam. The water from a hot spring at Garampani, near Jawai, in Assam is so hot in summer that rice kept in muslin bag gets worked in no time.
The Geological Survey of India has so far identified about 350 hot spring sites which can be explored as sources of geothermal energy. The engineers have commissioned an experimental 1 kW generator running on geothermal energy in the Puga area. This is the first production of electricity from a hot water spring in India.
Many countries with hot springs in their territories have realised their potential for power and heat production. Countries like Italy, Iceland, New Zealand, the USA and the USSR have achieved remarkable progress in the application of geothermal energy.
The Italian power plant at Landerello was started in 1904 on a small scale but now it produces 540 MW of electricity. This is equivalent to burning 1.5 million tonnes of oil in a year. New Zealand started exploration in 1950 and the Wairakei power station now produces 175 MW, which is equal to 0.7 million tonnes of oil per year. The power production in California, USA, began in 1960 and has already touched 50 MW.
In the Philippines the drillers struck high pressure, high temperature steam at about 200 m only at Tiwi, a tiny sleepy village nestled at the base of the volcano Malino, in 1967. By January, 1976, the first geothermal power plant at Tiwi began producing 55 MW. A geothermal plant with a capacity of 11 MW has been in operation for nearly 20 years in USSR. The construction of another power plant at Mutnovsky with a capacity of 200 MW is in progress.
At present, 35 countries of the world use about 15000 MWe geothermal energy for space heating, industrial and agricultural applications whereas 21 countries utilise geothermal energy for electricity generation.
The following countries have installed generating geothermal units (above 20 MWe) up to the year 2005:
