🌍 Sources of Energy
Geothermal Energy | भू-तापीय ऊर्जा
Class 10 CBSE Science | NCERT + Foundation + Competitive Preparation
🌋 Sources of Energy | Geothermal Energy
1. Introduction | परिचय
English: Geothermal energy is the energy obtained from the natural heat present inside the Earth.
हिन्दी: Geothermal Energy या भू-तापीय ऊर्जा वह ऊर्जा है जो पृथ्वी के अंदर प्राकृतिक रूप से उपस्थित ऊष्मा से प्राप्त की जाती है।
The word Geothermal comes from:
Geo = Earth
Thermal = Heat
हिन्दी: Geothermal Energy या भू-तापीय ऊर्जा वह ऊर्जा है जो पृथ्वी के अंदर प्राकृतिक रूप से उपस्थित ऊष्मा से प्राप्त की जाती है।
The word Geothermal comes from:
Geo = Earth
Thermal = Heat
Geothermal = Geo (Earth) + Thermal (Heat)
Exam Point: Geothermal energy is a renewable energy source because Earth's internal heat is continuously generated and stored over very long timescales, although individual geothermal reservoirs can be depleted if poorly managed.
परीक्षा बिंदु: भू-तापीय ऊर्जा पृथ्वी की आंतरिक ऊष्मा पर आधारित renewable energy source है।
परीक्षा बिंदु: भू-तापीय ऊर्जा पृथ्वी की आंतरिक ऊष्मा पर आधारित renewable energy source है।
2. Source of Geothermal Heat | भू-तापीय ऊष्मा का स्रोत
The Earth's interior is extremely hot. A significant part of this heat comes from the residual heat of Earth's formation and the radioactive decay of naturally occurring isotopes inside the Earth.
पृथ्वी का आंतरिक भाग बहुत गर्म है। इस ऊष्मा का एक महत्वपूर्ण भाग पृथ्वी के निर्माण से बची ऊष्मा तथा पृथ्वी के अंदर प्राकृतिक रेडियोधर्मी समस्थानिकों के क्षय से प्राप्त होता है।
पृथ्वी का आंतरिक भाग बहुत गर्म है। इस ऊष्मा का एक महत्वपूर्ण भाग पृथ्वी के निर्माण से बची ऊष्मा तथा पृथ्वी के अंदर प्राकृतिक रेडियोधर्मी समस्थानिकों के क्षय से प्राप्त होता है।
Important:
Earth's internal heat → heats rocks and underground water → hot water/steam → useful thermal energy or electricity.
Earth's internal heat → heats rocks and underground water → hot water/steam → useful thermal energy or electricity.
3. Earth's Internal Heat | पृथ्वी के अंदर की ऊष्मा
4. Underground Heat and Hot Water | भूमिगत गर्म जल
In some regions, groundwater comes into contact with hot rocks deep underground. The water gets heated and may become hot water or steam. Where geological conditions allow, this heat can be brought to the surface and used.
कुछ क्षेत्रों में भूमिगत जल गहराई में गर्म चट्टानों के संपर्क में आता है। इससे जल गर्म होकर hot water या steam में बदल सकता है। उपयुक्त भूगर्भीय परिस्थितियों में इस ऊष्मा का उपयोग किया जा सकता है।
कुछ क्षेत्रों में भूमिगत जल गहराई में गर्म चट्टानों के संपर्क में आता है। इससे जल गर्म होकर hot water या steam में बदल सकता है। उपयुक्त भूगर्भीय परिस्थितियों में इस ऊष्मा का उपयोग किया जा सकता है।
Hot Rocks + Underground Water → Hot Water / Steam
5. Geothermal Resources | भू-तापीय संसाधन
| Resource | Description |
|---|---|
| Hot water reservoirs | Underground reservoirs containing naturally heated water. |
| Steam reservoirs | Underground sources where steam is available. |
| Hot springs | Natural surface outlets of hot groundwater. |
| Geothermal wells | Wells drilled to access underground heat and fluids. |
| Hot dry rock / enhanced geothermal systems | Systems designed to extract heat from hot underground rock where natural fluid circulation is insufficient. |
6. Hot Springs | गर्म जल के स्रोत
A hot spring is a natural spring where heated groundwater reaches the Earth's surface.
Hot springs are visible examples of geothermal activity.
हिन्दी: Hot Spring वह प्राकृतिक स्रोत है जहाँ भूमिगत गर्म जल पृथ्वी की सतह पर बाहर आता है।
Hot springs are visible examples of geothermal activity.
हिन्दी: Hot Spring वह प्राकृतिक स्रोत है जहाँ भूमिगत गर्म जल पृथ्वी की सतह पर बाहर आता है।
7. Animated Geothermal Energy Plant | भू-तापीय ऊर्जा संयंत्र
8. Working of Geothermal Power Plant | कार्य-विधि
-
Heat source:
Heat from Earth's interior warms underground rocks and fluids.
ऊष्मा स्रोत: पृथ्वी के अंदर की ऊष्मा चट्टानों तथा भूमिगत द्रवों को गर्म करती है। -
Production well:
A well may be drilled to bring hot water or steam to the surface.
Production well: गर्म जल या steam को सतह तक लाने के लिए कुआँ खोदा जा सकता है। -
Steam/Hot fluid:
The hot fluid provides thermal energy.
गर्म द्रव: गर्म जल या steam अपनी ऊष्मा ऊर्जा प्रदान करता है। -
Turbine:
Steam or another geothermal working fluid can drive a turbine.
Turbine: Steam या geothermal working fluid turbine को घुमा सकता है। -
Generator:
The turbine drives a generator that produces electrical energy.
Generator: Turbine generator को घुमाता है जिससे विद्युत ऊर्जा उत्पन्न होती है। -
Reinjection:
In many systems, cooled geothermal fluid is reinjected into the reservoir.
Reinjection: कई प्रणालियों में ठंडे हुए geothermal fluid को वापस भूमिगत reservoir में भेजा जाता है।
9. Types of Geothermal Power Plants
| Type | Working |
|---|---|
| Dry Steam Plant | Uses natural steam from an underground geothermal reservoir directly to drive a turbine. |
| Flash Steam Plant | High-pressure hot water is brought to lower pressure so that part of it flashes into steam. |
| Binary Cycle Plant | Geothermal hot water heats a secondary fluid with a lower boiling point, which drives the turbine. |
Memory Trick:
Dry → Steam Direct
Flash → Hot Water → Steam
Binary → Secondary Fluid
Dry → Steam Direct
Flash → Hot Water → Steam
Binary → Secondary Fluid
10. Binary Cycle Power Plant | बाइनरी चक्र संयंत्र
In a binary cycle plant, geothermal water heats a second fluid that has a lower boiling point than water. The secondary fluid vaporizes and drives the turbine.
Binary cycle system में geothermal water एक दूसरे fluid को गर्म करता है जिसका boiling point पानी से कम होता है। यह secondary fluid vaporize होकर turbine को घुमाता है।
Binary cycle system में geothermal water एक दूसरे fluid को गर्म करता है जिसका boiling point पानी से कम होता है। यह secondary fluid vaporize होकर turbine को घुमाता है।
Geothermal Heat → Secondary Fluid → Vapour → Turbine → Generator
11. Direct Use of Geothermal Energy | प्रत्यक्ष उपयोग
Geothermal heat does not always need to be converted into electricity. Hot geothermal water can directly provide useful heat.
| Application | Use |
|---|---|
| Space heating | Heating buildings in suitable regions. |
| Greenhouses | Maintaining suitable temperature for crops. |
| Bathing | Hot spring and thermal bathing applications. |
| Industrial heating | Providing heat for selected industrial processes. |
| District heating | Supplying heat to multiple buildings through a distribution network. |
12. Advantages of Geothermal Energy | लाभ
- Renewable: Earth's internal heat is continuously replenished over long timescales.
- Reliable: Geothermal plants can provide energy independent of sunlight and wind conditions.
- Small land footprint: A geothermal facility can generate significant energy from a relatively compact site compared with some large surface-based renewable installations.
- Low operational emissions: Properly managed geothermal plants generally have low greenhouse-gas emissions compared with fossil-fuel power generation.
- Direct heating: Geothermal heat can be used directly without converting it to electricity.
- Base-load potential: Suitable geothermal resources can provide steady electricity output.
13. Limitations of Geothermal Energy | सीमाएँ
- Suitable geothermal resources are geographically limited.
- Exploration and drilling can be expensive.
- Deep drilling requires specialized technology.
- Some geothermal fluids contain dissolved minerals and gases that require careful handling.
- Reservoirs must be managed carefully to maintain long-term productivity.
- Induced seismicity can occur in some geothermal projects, particularly certain enhanced geothermal systems.
- Improper management can lead to environmental impacts such as fluid leakage or groundwater concerns.
14. Geothermal Energy vs Solar Energy
| Geothermal Energy | Solar Energy |
|---|---|
| Uses Earth's internal heat. | Uses energy from the Sun. |
| Can operate day and night where suitable resources are available. | Solar PV output depends on sunlight. |
| Resource availability is location dependent. | Solar resource is widely available in many regions. |
| Requires drilling/exploration for many systems. | Solar panels can be installed directly at the surface. |
15. Geothermal Energy vs Fossil Fuels
| Geothermal | Fossil Fuels |
|---|---|
| Uses Earth's natural internal heat. | Burns coal, petroleum or natural gas. |
| Renewable when reservoirs are sustainably managed. | Non-renewable on human timescales. |
| No fuel combustion is required in the basic geothermal energy conversion process. | Combustion releases carbon dioxide and other pollutants. |
| Low operational greenhouse-gas emissions for many systems. | Generally much higher greenhouse-gas emissions. |
16. Geothermal Energy in India | भारत में भू-तापीय ऊर्जा
India has several regions with geothermal manifestations such as hot springs. Examples include areas in the Himalayan region, western India and parts of central India.
Some well-known geothermal locations include Puga Valley in Ladakh, Manikaran in Himachal Pradesh and Tattapani in Chhattisgarh.
These sites demonstrate geothermal potential, although the suitability for large-scale power generation depends on resource temperature, flow rate, geology, drilling feasibility and economics.
Some well-known geothermal locations include Puga Valley in Ladakh, Manikaran in Himachal Pradesh and Tattapani in Chhattisgarh.
These sites demonstrate geothermal potential, although the suitability for large-scale power generation depends on resource temperature, flow rate, geology, drilling feasibility and economics.
Exam Note: Do not assume that every hot spring automatically makes a suitable commercial geothermal power plant. Electricity generation requires an adequate and economically accessible geothermal resource.
17. Hot Springs, Geysers and Geothermal Energy
Hot Spring: Naturally occurring hot groundwater reaching the surface.
Geyser: A geothermal feature that periodically ejects hot water and steam through a vent.
Geothermal Power Plant: A facility designed to convert geothermal heat into electrical energy.
Geyser: A geothermal feature that periodically ejects hot water and steam through a vent.
Geothermal Power Plant: A facility designed to convert geothermal heat into electrical energy.
18. Energy Conversion in Geothermal Power Plant
Geothermal Heat Energy
↓
Thermal Energy of Steam / Working Fluid ↓
Mechanical Energy of Turbine ↓
Electrical Energy of Generator
Thermal Energy of Steam / Working Fluid ↓
Mechanical Energy of Turbine ↓
Electrical Energy of Generator
Important: The turbine converts the energy of the moving steam/working fluid into mechanical rotation, and the generator converts mechanical energy into electrical energy.
19. Environmental Impact | पर्यावरणीय प्रभाव
Geothermal energy generally has lower emissions than fossil-fuel power generation, but it is not completely free of environmental impacts.
Potential issues include release of naturally occurring gases, mineral-rich fluids, water management, land disturbance and induced seismicity in some projects.
Proper reinjection, monitoring and engineering controls can reduce these impacts.
Potential issues include release of naturally occurring gases, mineral-rich fluids, water management, land disturbance and induced seismicity in some projects.
Proper reinjection, monitoring and engineering controls can reduce these impacts.
20. 30 MCQs | बहुविकल्पीय प्रश्न
1. Geothermal energy is obtained from:
A. Earth's internal heat
B. Moonlight
C. Wind only
D. Ocean waves only
Answer: A
2. The word "Geo" refers to:
A. Water
B. Earth
C. Air
D. Fire
Answer: B
3. The word "Thermal" refers to:
A. Pressure
B. Electricity
C. Heat
D. Sound
Answer: C
4. A major source of Earth's internal heat is:
A. Moonlight
B. Ocean currents
C. Wind
D. Radioactive decay of naturally occurring isotopes
Answer: D
5. A natural outlet of hot groundwater is called:
A. Hot spring
B. Glacier
C. Lagoon
D. Delta
Answer: A
6. A geothermal power plant mainly converts geothermal heat into:
A. Chemical energy only
B. Electrical energy
C. Nuclear energy
D. Sound energy
Answer: B
7. In a geothermal power plant, the turbine is used to:
A. Store water
B. Produce fuel
C. Convert fluid energy into mechanical rotation
D. Absorb sunlight
Answer: C
8. The generator converts:
A. Electrical energy into heat
B. Heat into chemical energy
C. Chemical energy into light
D. Mechanical energy into electrical energy
Answer: D
9. Which plant uses natural steam directly?
A. Dry steam plant
B. Solar thermal plant
C. Nuclear plant
D. Hydroelectric plant
Answer: A
10. In a flash steam plant:
A. Coal is burned
B. Hot water flashes into steam when pressure is reduced
C. Solar cells produce steam
D. Wind directly heats water
Answer: B
11. A binary cycle plant uses:
A. Only coal
B. Only natural gas
C. A secondary fluid with a lower boiling point
D. Uranium
Answer: C
12. Which is a geothermal feature?
A. Hot spring
B. Solar panel
C. Wind turbine
D. Dam
Answer: A
13. Geothermal energy is classified as:
A. Non-renewable only
B. Renewable energy
C. Nuclear fuel
D. Fossil fuel
Answer: B
14. Which is a limitation of geothermal energy?
A. It is available everywhere equally
B. It requires sunlight
C. Suitable resources are geographically limited
D. It cannot produce electricity
Answer: C
15. Geothermal energy can be used directly for:
A. Space heating
B. Nuclear fission
C. Making sunlight
D. Producing coal
Answer: A
16. Puga Valley is associated with geothermal potential in:
A. Kerala
B. Ladakh
C. Punjab
D. Goa
Answer: B
17. Manikaran is known for:
A. Hot springs
B. Coal mines only
C. Wind farms only
D. Nuclear reactors
Answer: A
18. In many geothermal systems, cooled fluid may be:
A. Burned as coal
B. Released into space
C. Reinjected into the reservoir
D. Converted into uranium
Answer: C
19. Geothermal energy does not depend directly on:
A. Earth's internal heat
B. Suitable underground resources
C. Drilling in many projects
D. Daily sunlight availability
Answer: D
20. Which statement is correct?
A. Geothermal energy uses Earth's internal heat
B. Geothermal energy is produced only by wind
C. Geothermal plants require coal combustion
D. Geothermal energy is the same as solar energy
Answer: A
21. Which is a possible environmental concern of some geothermal projects?
A. Induced seismicity
B. Formation of coal
C. Creation of sunlight
D. Ozone production by turbines
Answer: A
22. The hot underground reservoir mainly provides:
A. Geothermal heat
B. Wind
C. Solar radiation
D. Coal
Answer: A
23. A geyser periodically ejects:
A. Sand and coal
B. Hot water and steam
C. Petroleum only
D. Ice
Answer: B
24. Which geothermal plant is particularly useful for lower-temperature resources?
A. Binary cycle plant
B. Dry steam plant only
C. Coal plant
D. Diesel plant
Answer: A
25. Geothermal energy can be used for:
A. Electricity
B. Heating
C. Both A and B
D. Neither A nor B
Answer: C
26. Which component is driven by steam or working fluid?
A. Turbine
B. Solar cell
C. Battery only
D. Transformer only
Answer: A
27. Geothermal energy is especially suitable where:
A. There is a usable geothermal resource
B. There is no underground heat
C. Only coal is available
D. Only wind is available
Answer: A
28. The major advantage of geothermal electricity is that suitable plants can:
A. Operate without direct dependence on daily weather conditions
B. Work only at noon
C. Work only during storms
D. Require no geothermal resource
Answer: A
29. Which sequence is correct?
A. Geothermal heat → turbine → generator → electricity
B. Electricity → coal → geothermal heat
C. Wind → geothermal heat → coal
D. Solar cell → magma → uranium
Answer: A
30. The best definition of geothermal energy is:
A. Energy obtained from Earth's internal heat
B. Energy obtained only from ocean waves
C. Energy obtained from coal combustion
D. Energy obtained from moonlight
Answer: A
21. 30 Subjective Questions with Answers
2 Marks
Q1. What is geothermal energy?
Geothermal energy is energy obtained from the natural heat present inside the Earth.
2 Marks
Q2. What does the word geothermal mean?
Geo means Earth and thermal means heat. Therefore, geothermal means heat associated with the Earth.
2 Marks
Q3. Name two sources of Earth's internal heat.
Residual heat from Earth's formation and heat generated by radioactive decay of naturally occurring isotopes are two important sources.
2 Marks
Q4. What is a hot spring?
A hot spring is a natural spring in which heated groundwater reaches the Earth's surface.
2 Marks
Q5. What is a geothermal power plant?
It is a power plant that uses geothermal heat, usually through hot water or steam/another working fluid, to generate electricity.
3 Marks
Q6. Why is geothermal energy called renewable?
Earth continuously produces and stores internal heat over very long timescales. With proper reservoir management, geothermal resources can be used sustainably.
3 Marks
Q7. How does underground water become hot?
Groundwater can circulate deep into the Earth's crust and come into contact with hot rocks. It absorbs heat and becomes hot water or may form steam under suitable conditions.
3 Marks
Q8. What is the function of a turbine in a geothermal plant?
The turbine converts the energy of steam or another moving working fluid into mechanical rotational energy.
3 Marks
Q9. What is the function of a generator?
A generator converts the mechanical rotational energy supplied by the turbine into electrical energy.
3 Marks
Q10. Give three uses of geothermal energy.
It can be used for electricity generation, space heating and greenhouse heating. It can also be used for bathing and selected industrial heating applications.
3 Marks
Q11. What is a geyser?
A geyser is a geothermal feature that periodically ejects hot water and steam through a surface vent.
3 Marks
Q12. Name three types of geothermal power plants.
Dry steam, flash steam and binary cycle plants are three major types.
4 Marks
Q13. Explain the working of a geothermal power plant.
Heat from Earth's interior heats underground water or other geothermal fluids. A production well brings hot fluid to the surface. Steam or a secondary working fluid drives a turbine. The turbine drives a generator, producing electricity. The cooled geothermal fluid may be reinjected.
4 Marks
Q14. Explain the dry steam power plant.
A dry steam plant uses naturally occurring geothermal steam from an underground reservoir. The steam is directed to a turbine, which drives a generator. The resulting electricity is supplied to the grid or local loads.
4 Marks
Q15. Explain a flash steam power plant.
High-pressure hot geothermal water is brought to a lower pressure. Some of the hot water rapidly changes into steam. This steam drives a turbine connected to a generator.
4 Marks
Q16. Explain a binary cycle geothermal plant.
Geothermal hot water transfers heat to a secondary fluid having a lower boiling point. The secondary fluid vaporizes and drives the turbine. The turbine powers a generator to produce electricity.
4 Marks
Q17. Write four advantages of geothermal energy.
It is renewable when sustainably managed, can provide reliable energy, does not depend directly on daily sunlight or wind conditions, and can be used for both electricity and direct heating.
4 Marks
Q18. Write four limitations of geothermal energy.
Suitable sites are geographically limited, drilling is expensive, geothermal fluids may require treatment, and some projects can have environmental impacts such as induced seismicity or groundwater concerns.
5 Marks
Q19. Explain the energy conversion in a geothermal power plant.
Geothermal heat warms water or a working fluid. Its thermal energy produces moving steam or vapour. The moving fluid rotates a turbine, converting thermal/fluid energy into mechanical energy. The generator then converts mechanical energy into electrical energy.
5 Marks
Q20. Differentiate between geothermal and solar energy.
Geothermal energy comes from Earth's internal heat, whereas solar energy comes from the Sun. Geothermal plants can operate day and night when a suitable resource is available, while solar PV output depends on sunlight. Geothermal development often requires drilling, whereas solar systems are installed at the surface.
5 Marks
Q21. Why can geothermal energy provide relatively continuous power?
The Earth's internal heat is continuously available, and suitable geothermal reservoirs can supply hot fluid over extended periods. Therefore, geothermal electricity does not directly depend on daylight or short-term wind conditions.
5 Marks
Q22. Explain the importance of reinjection in geothermal systems.
Reinjection returns cooled geothermal fluid to the underground reservoir. It can help maintain reservoir pressure and support long-term resource management when properly designed and monitored.
5 Marks
Q23. Explain hot springs and their relation to geothermal energy.
Hot springs occur where heated groundwater naturally reaches the Earth's surface. They are visible evidence of geothermal activity and can indicate areas where underground heat is accessible.
6 Marks
Q24. Explain geothermal energy in detail with its advantages and limitations.
Geothermal energy is obtained from Earth's internal heat. Underground hot water or steam can be brought to the surface through wells and used directly or to drive turbines for electricity generation. Advantages include renewable supply, reliable operation at suitable sites, low operational emissions and direct heating applications. Limitations include site dependence, high exploration/drilling costs, resource management requirements and possible environmental impacts.
6 Marks
Q25. Explain the three major types of geothermal power plants.
Dry steam: natural steam directly drives the turbine.
Flash steam: high-pressure hot water undergoes pressure reduction and part of it flashes into steam.
Binary cycle: geothermal water heats a secondary low-boiling-point fluid, whose vapour drives the turbine.
Flash steam: high-pressure hot water undergoes pressure reduction and part of it flashes into steam.
Binary cycle: geothermal water heats a secondary low-boiling-point fluid, whose vapour drives the turbine.
6 Marks
Q26. Why is geothermal energy considered cleaner than fossil-fuel energy?
Geothermal power does not require conventional combustion of coal, oil or gas. Consequently, properly managed geothermal plants generally have much lower greenhouse-gas emissions and air pollution than fossil-fuel power plants, although geothermal systems can still have environmental impacts.
6 Marks
Q27. Explain the role of the turbine and generator in a geothermal power plant.
The geothermal fluid provides energy to the turbine. The turbine rotates due to the moving steam or working fluid and converts its energy into mechanical rotational energy. The generator uses this rotation to produce electrical energy through electromagnetic induction.
6 Marks
Q28. Explain geothermal energy resources in India.
India has several geothermal manifestations, including hot springs in regions such as Ladakh and Himachal Pradesh and other parts of the country. Puga Valley, Manikaran and Tattapani are commonly cited examples. Their suitability for large-scale electricity generation depends on temperature, fluid availability, geological conditions, drilling feasibility and economics.
6 Marks
Q29. What environmental precautions should be taken in geothermal projects?
Projects should properly manage geothermal fluids, control gas emissions, prevent contamination of groundwater, monitor pressure and seismic activity, manage mineral-rich fluids, and use reinjection where appropriate. Continuous monitoring is important for sustainable operation.
6 Marks
Q30. Write an exam-ready note on Geothermal Energy.
Geothermal energy is the energy obtained from Earth's internal heat. Heat may warm underground rocks and water, producing hot water or steam. Wells can bring geothermal fluids to the surface. The fluid can drive a turbine connected to a generator, producing electricity. Major plant types are dry steam, flash steam and binary cycle. Geothermal energy is renewable when reservoirs are properly managed and can provide reliable energy, but suitable resources are location-specific and drilling can be expensive.
22. Assertion–Reason | कथन–कारण
Q1. Assertion: Geothermal energy is obtained from Earth's internal heat.
Reason: The interior of Earth contains significant thermal energy.
Reason: The interior of Earth contains significant thermal energy.
Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.
Q2. Assertion: A geothermal power plant can use steam to rotate a turbine.
Reason: Moving steam can transfer energy to turbine blades.
Reason: Moving steam can transfer energy to turbine blades.
Answer: Both are true, and the Reason correctly explains the Assertion.
Q3. Assertion: Geothermal energy requires sunlight for its operation.
Reason: Earth's internal heat comes mainly from sunlight.
Reason: Earth's internal heat comes mainly from sunlight.
Answer: Both Assertion and Reason are false.
Q4. Assertion: Binary cycle plants can use a secondary working fluid.
Reason: The secondary fluid may have a lower boiling point than water.
Reason: The secondary fluid may have a lower boiling point than water.
Answer: Both are true, and the Reason correctly explains the Assertion.
Q5. Assertion: Every hot spring automatically provides an economical source of geothermal electricity.
Reason: Electricity generation depends on resource temperature, flow, geology and economics.
Reason: Electricity generation depends on resource temperature, flow, geology and economics.
Answer: Assertion is false, but Reason is true.
23. HOTS / Competency-Based Questions
HOTS 1: Why can geothermal power operate at night while solar PV cannot produce electricity without sunlight?
Geothermal power uses Earth's internal heat rather than sunlight, so a suitable geothermal reservoir can provide thermal energy continuously. Solar PV requires incoming solar radiation.
HOTS 2: Why is a geothermal plant not suitable at every location?
A commercially useful geothermal resource requires suitable underground temperature, fluid availability, permeability, geological conditions and economic drilling access.
HOTS 3: Why is reinjection useful?
It can return cooled geothermal fluid to the reservoir, helping maintain pressure and supporting long-term resource management.
HOTS 4: A region has hot groundwater but its temperature is too low for direct steam generation. Which technology may be useful?
A binary cycle system may be useful because geothermal heat can vaporize a secondary fluid with a lower boiling point.
HOTS 5: Why should geothermal energy still be monitored even though it is renewable?
Renewable does not mean impact-free. Reservoir pressure, groundwater, gases, mineral-rich fluids and seismic activity need monitoring for safe and sustainable operation.
24. Golden Points | परीक्षा के लिए महत्वपूर्ण बिंदु
- Geothermal = Geo + Thermal = Earth's heat.
- Geothermal energy comes from Earth's internal heat.
- Earth's internal heat includes residual formation heat and radioactive decay.
- Hot springs are natural geothermal features.
- Geysers periodically release hot water and steam.
- Geothermal energy can generate electricity.
- Geothermal heat can also be used directly.
- Dry steam plant uses natural steam.
- Flash steam plant uses hot water that flashes into steam after pressure reduction.
- Binary cycle plant uses a secondary low-boiling-point fluid.
- Turbine converts fluid energy into mechanical rotation.
- Generator converts mechanical energy into electrical energy.
- Geothermal energy does not directly depend on daily sunlight.
- Suitable geothermal resources are geographically limited.
- Drilling and exploration can be expensive.
- Reinjection can support reservoir management.
- Puga Valley, Manikaran and Tattapani are examples of Indian geothermal locations.
25. One-Minute Revision | एक मिनट में Revision
🌋 Earth's Internal Heat
↓
💧 Hot Water / Steam ↓
⚙️ Turbine ↓
⚡ Generator ↓
🔌 Electricity
💧 Hot Water / Steam ↓
⚙️ Turbine ↓
⚡ Generator ↓
🔌 Electricity
Source: Earth's internal heat
Resource: Hot water / Steam / Geothermal fluid
Main machine: Turbine
Electricity: Generator
Major plants: Dry Steam, Flash Steam, Binary Cycle
Renewable: Yes, with sustainable resource management
Direct use: Heating, greenhouses, bathing, industrial heat
Indian examples: Puga Valley, Manikaran, Tattapani
Resource: Hot water / Steam / Geothermal fluid
Main machine: Turbine
Electricity: Generator
Major plants: Dry Steam, Flash Steam, Binary Cycle
Renewable: Yes, with sustainable resource management
Direct use: Heating, greenhouses, bathing, industrial heat
Indian examples: Puga Valley, Manikaran, Tattapani
26. Concept Map | अवधारणा मानचित्र
27. Final Summary | अंतिम सारांश
Geothermal energy is the energy obtained from the natural heat inside the Earth. Underground heat can warm rocks and groundwater, producing hot water or steam. These geothermal fluids can be used directly for heating or can drive turbines connected to generators for electricity production.
The major types of geothermal power plants are dry steam, flash steam and binary cycle plants. Geothermal energy can provide reliable power at suitable locations and has relatively low operational emissions compared with fossil-fuel power generation.
However, geothermal resources are geographically limited, drilling can be expensive, and proper management is necessary to control environmental impacts and maintain reservoir productivity.
Final Memory Line:
🌋 Earth's Heat → Hot Fluid/Steam → Turbine → Generator → Electricity
The major types of geothermal power plants are dry steam, flash steam and binary cycle plants. Geothermal energy can provide reliable power at suitable locations and has relatively low operational emissions compared with fossil-fuel power generation.
However, geothermal resources are geographically limited, drilling can be expensive, and proper management is necessary to control environmental impacts and maintain reservoir productivity.
Final Memory Line:
🌋 Earth's Heat → Hot Fluid/Steam → Turbine → Generator → Electricity
📘 Class 10 CBSE Science
Sources of Energy | Geothermal Energy
NCERT + Foundation + Competitive Preparation
Sources of Energy | Geothermal Energy
NCERT + Foundation + Competitive Preparation
