Here is a compilation of essays on ‘Geothermal Energy’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Geothermal Energy’ especially written for school and college students.

Essay on Geothermal Energy


Essay Contents:

  1. Essay on the Introduction to Geothermal Energy
  2. Essay on the Types of Geothermal Energy
  3. Essay on the Geothermal Energy Resources in India
  4. Essay on the Hybrid Systems
  5. Essay on the Advantages of Geothermal Energy
  6. Essay on the Disadvantages of Geothermal Energy


Essay # 1. Introduction to Geothermal Energy:

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Geothermal energy is primarily energy from the earth’s own interior. 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 as inexhaustible as solar or wind energy, so long as its sources are actively sought and economically tapped. The centre of the earth is estimated at temperatures up to 10,000 K due to decay process of radioactive isotopes.

Geothermal energy is the sheet energy deep within the temperature earth. Huge amount of heat are stored in the lower layer of the earth crust. The temperature of earth interior increases with depth. A temperature of 200°C – 300°C normally occur only at the depth of 10 km. U.S. Geological survey defines geothermal sources as “All heat stored in the earth’s crust above 15°C to a depth of 10 km”.

The total steady geothermal energy flow towards earth’s surface is 4.2 × 1010 kW. But the average energy flow density is only 0.063 W/m2 and average temperature gradient is 30 K per kilometer of depth. Locations with very high temperature gradients are suitable for geothermal energy utilization. Geo­thermal energy can be used for heat and power generation.


Essay # 2. Types of Geothermal Energy:

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The molten mass of the earth is called magma. The thickness of crust above magma is about 32 km in average. At certain places due to earth’s tremors, magma came close to earth’s surface. The hot magma near the surface causes active volcanoes, hot springs and geysers where water exits. It also causes steam to vent through the fissures in the form of geothermal energy.

Geothermal energy reservoirs are liquid-dominated and steam dominated. Some are only hot rocks where there is no ground water.

Geothermal Sources are:

A. Hydrothermal systems.

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B. Geopressured systems.

C. Petrothermal systems.

A. Hydrothermal Systems:

Steam and water from hydrothermal system contain the following:

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1. Dissolved solids in water.

2. Entrained solid particles.

3. Non condensable gases (CO2, CH4, H2, N2, and NH3, H2S).

4. Sand.

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The above solid and non-condensable gases have to be removed before using steam or water for power generation.

These create the following environmental problems:

1. The non-condensable gases enter the equipment with the fluid and partly escape to the atmosphere via particle centrifugal separators, condenser ejectors and cooling towers.

2. The gas ejectors have to be specially designed to handle large quantities of non-condensable gases as compared to conventional steam power plants.

3. The corrosive action of these gases in wet conditions requires the use of stainless steel for handling wet steam and condensate.

4. Special materials of construction are required for steam turbines, nozzles, condensers, cooling towers, pipes and valves and open structures due to presence of corrosive atmosphere.

5. All electrical equipment needs protected copper to withstand the corrosive action of H2S on bare copper.

6. H2S and NH3 are corrosive and toxic and therefore objectionable for escape into atmosphere.

7. Large extraction of geothermal fluids and reinjection into the ground pose the possibility of seismic disturbances.

8. Exhausts, blow downs and centrifugal separation are sources of noise pollution and suitable silencers have to be installed.

9. Geopressed water carrier’s large quantities of sand resulting in increased erosion and scaling problems.

These can be vapour-dominated and liquid- dominated systems:

1. Vapour-Dominated Systems:

In these systems, water is vaporized into steam which reaches the earth’s surface at 8 bars and 205°C in dry condition. The steam can be used to produce power by Rankine Cycle with minimum costs.

However, the steam is associated with corrosive and erosive materials. Such systems are very rare in the world.

2. Liquid-Dominated Systems:

Hot water is trapped underground at a temperature of 174 to 315°C. This water is brought up either by drilling wells or pumped up. Due to pressure drop, hot water flashes into two phase mixture of low quality. The water contains high concentration of dissolved solids and power production becomes difficult due to scaling in pipes and heat exchangers. The liquid-dominated systems are much more plentiful.

B. Geopressured Systems:

Geopressured system is hot water or brine at about 160°C trapped under­ground at about 2400 to 9100m depth. The pressure is more than 1000 bar. Although it has great thermal and mechanical potential for power generation, but due to low temperatures and great depth, it may not be economical to drill for this brine. But this brine has recoverable methane and there may be economic feasibility to generate electricity involving combustion of methane as well as heat from the thermal content of water.

C. Petrothermal Systems:

When there is no underground water, there are hot dry rocks (HDR) at 150 to 298°C near the earth’s surface. This energy is called petrothermal energy and accounts for 85% of geothermal resources. Water will have to be pumped into and back out to the surface. Fracturing methods for drilling wells into the rocks can be by- (i) high pressure water or (ii) nuclear explosions.

The thermal energy of hot dry rock (HDR) is extracted by pumping water (or other fluid) through a well drilled to the lower part of the fractured rock. The water flows through the fractures, gets heated and travels up through the second drilled well. The hot water is used to produce electricity as in case of liquid-dominated geothermal system.

It offers more flexibility in design and operation. The water flow rate and temperatures can be controlled for a site by drilling to various depths. The operator of the plant can change the pumping pressure and therefore, flow rates to suit the load conditions.

The limitations of petrothermal systems are:

i. Leakage of water underground.

ii. Necessity of make-up water from resources above ground.

iii. Effect of water on rock composition.

iv. Material carryover with water.

v. High cost as two wells have to be drilled instead of one as in hydrothermal systems.

vi. Very detailed studies on the mechanical thermodynamic and economic aspects are necessary before commercial exploitation becomes feasible.


Essay # 3. Geothermal Energy Resources in India:

India’s geothermal energy capacity have been estimated to produce 10,000 MW of power- a figure which is much higher than the combined power being produced from non-conventional energy sources such as wind, solar and biomass. But yet geothermal power has not been explored.

With escalating environmental problems with coal based projects, India has to depend on clean, cheap, rural based and eco-friendly geothermal power in future. With the existing open economic policies of the Govt., and large incentives given to non-conventional energy sectors, the future of geothermal energy sector in India appears to be bright.

Several geothermal provinces in India characterized by high heat flow (78-468 mW/m ) and thermal gradients (47-100°C/km) discharge about 400 thermal springs. After the oil crisis in 1970s, the Geological Survey of India conducted lot of survey to explore the possibilities of geothermal power harnessing. The investigations carried out in the past have identified several sites which are suitable for power generations as well as for direct use.

These provinces are capable of generating 10,000 MW of power. Though geothermal power production in Asian countries like Indonesia, Philippines has gone up, India with its around 10,000 MW geothermal power potential is yet to harness to its full capacity. However, with the growing environmental problems associated with thermal power plants, future for geothermal power in India appears to be bright.


Essay # 4. Hybrid Systems:

The high-temperature heat of fossil-fuel combustion systems can be used in the high-temperature end of a Rankine Cycle and low-temperature heat of geo­thermal heat can be used in the low-temperature end of a conventional power plant. Such hybrid systems thus combine the high efficiency of a high-temperature cycle with a natural source of heat for part of heat addition. The consump­tion of expensive and nonrenewable fossil fuel can be reduced substantially.

There are two possible arrangements for hybrid plants:

1. Geothermal Preheat Hybrid System:

The low temperature geothermal heat is used for feed water heating in a conventional steam plant. No steam is required to be bled from the low-pressure stages of steam turbine and feed water heating is carried out using geothermal brine.

2. Fossil-Superheat Hybrid System:

The geothermal fluid can be superheated in a fossil-fired super heater. A flow diagram and T-s diagram of such a plant are shown in Fig. 7.11 and 7.12 respectively.

Fossil-Superheat Hybrid System

T-s Diagram of Hybrid System


Essay # 5. Advantages of Geothermal Energy:

Geothermal energy is versatiline in use:

1. This energy is least polluting in comparison of other energy resources.

2. It is renewable sources of energy.

3. It is cheaper sources of energy.


Essay # 6. Disadvantages of Geothermal Energy:

1. Overall efficiency of power production is low.

2. Drilling operation is noisy.

3. Large areas are needed for exploitation of geothermal energy.

4. The steam and hot water coming out of earth may contain H2S, CO2, NH3, radon etc. If these gases are vented into the air, may cause air pollution.

Hot molten rock called magna is present 25-40 km depth in the core of the earth. When the ground water finds its way into such a rock having molten in lava then it gets heated up by the heat of the rock and molten magna and comes to the surface of the earth as steam and hot water 200°C to 300°C. This hot water or steam is used to operate turbines to generate electricity.

Geothermal Power Plant (Wet Steam)Geothermal energy is the most versatile and least polluting renewable energy resources:

a. Used for space heating

b. Boiling water

c. Generate steam, soil warming, inshroom growing Balneoloy.

d. Drying of organic materials, sea weeds, grass, vegetables.

Efforts are being made to use this energy for generating power and creating refrigera­tion etc. A cold storage unit and 5 MW power plant have been set up a Manikaran (H.P). Geological exploration for prospective location for geothermal energy of electricity genera­tion are to be undertaken, Drilling into deeper levels is necessary where there is a possibility of availability of geothermal fluids.

At present nearly 350 geothermal springs have been located in the country. Puga (ladakh) geothermal area is a good site for power generation. Other areas to be screened are, Tattapani (Sarguja Distt. M.P.), Cambay Basin (Alaknanda valley, U.P.) and Parvati valley (H.P).


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