Ocean Thermal Energy (OTEC)
Complete Detailed Notes for Competitive Examinations
Ocean Thermal Energy Conversion, Working, Advantages, Disadvantages and Applications
By Home Academy
1. Introduction to Ocean Thermal Energy
Ocean Thermal Energy is the energy obtained from the temperature difference between warm surface water and cold deep ocean water.
This technology is called:
Ocean Thermal Energy Conversion (OTEC)
It is a:
Renewable source of energy
Non-conventional source of energy
Pollution-free source of energy
2. Principle of Ocean Thermal Energy
OTEC works on the principle that:
Surface ocean water is heated by Sun.
Deep ocean water remains cold.
The temperature difference is used to generate electricity.
Important Condition
For efficient OTEC operation:
Temperature difference should be about 20°C or more.
Energy Conversion
Thermal\ Energy\ of\ Ocean \rightarrow Mechanical\ Energy \rightarrow Electrical\ Energy
3. Temperature Distribution in Ocean
| Ocean Layer | Temperature |
|---|---|
| Surface water | Warm (25°C–30°C) |
| Deep water | Cold (5°C–10°C) |
Important Point
Warm water is found near tropical regions.
4. Working of OTEC Plant
Basic Working
Warm surface water heats a liquid with low boiling point.
Liquid changes into vapor.
Vapor rotates turbine.
Generator produces electricity.
Cold deep water condenses vapor back into liquid.
5. Fluids Used in OTEC
Liquids with low boiling point are used.
Example
| Fluid |
|---|
| Ammonia |
| Propane |
Important Point
Ammonia vaporizes easily due to warm seawater.
6. Types of OTEC Systems
| Type | Description |
|---|---|
| Closed-cycle OTEC | Uses working fluid like ammonia |
| Open-cycle OTEC | Uses seawater directly |
| Hybrid-cycle OTEC | Combination of both |
A. Closed-Cycle OTEC
Working
Warm water heats ammonia.
Ammonia vapor rotates turbine.
Cold water condenses ammonia vapor.
Important Point
Most common OTEC system.
B. Open-Cycle OTEC
Working
Warm seawater converted into steam under low pressure.
Steam drives turbine.
Advantage
Produces fresh water along with electricity.
C. Hybrid-Cycle OTEC
Combination of:
Closed cycle
Open cycle
7. Components of OTEC Plant
| Component | Function |
|---|---|
| Evaporator | Converts liquid into vapor |
| Turbine | Rotates due to vapor |
| Generator | Produces electricity |
| Condenser | Converts vapor back into liquid |
| Pipes | Carry warm and cold water |
8. Advantages of Ocean Thermal Energy
| Advantage | Explanation |
|---|---|
| Renewable | Continuous energy source |
| Pollution free | No harmful gases |
| Continuous supply | Available day and night |
| Produces fresh water | In open-cycle systems |
9. Disadvantages of Ocean Thermal Energy
| Disadvantage | Explanation |
|---|---|
| High installation cost | Expensive technology |
| Limited locations | Tropical oceans needed |
| Low efficiency | Small temperature difference |
| Maintenance difficulty | Corrosion by seawater |
10. Applications of OTEC
| Application | Use |
|---|---|
| Electricity generation | Main application |
| Desalination | Fresh water production |
| Air conditioning | Cooling systems |
| Aquaculture | Fish farming |
11. Areas Suitable for OTEC
OTEC works best in:
Tropical oceans
Equatorial regions
Suitable Countries/Regions
| Region |
|---|
| India |
| Hawaii |
| Japan |
| Philippines |
12. OTEC in India
India has good OTEC potential because:
Large tropical coastline
Warm ocean surface water
Important Organization
National Institute of Ocean Technology (NIOT)
has worked on OTEC projects.
Potential Areas in India
| Area |
|---|
| Lakshadweep |
| Andaman and Nicobar Islands |
13. Difference Between Tidal Energy and OTEC
| Tidal Energy | Ocean Thermal Energy |
|---|---|
| Uses tides | Uses temperature difference |
| Caused by Moon’s gravity | Caused by solar heating |
| Uses moving water | Uses warm and cold water |
14. Environmental Impact
Positive Effects
Reduces fossil fuel use
Low air pollution
Negative Effects
Disturbs marine ecosystem
Affects ocean temperature balance
15. Important Exam Points
OTEC stands for Ocean Thermal Energy Conversion.
Uses temperature difference between warm and cold ocean water.
Requires temperature difference of about 20°C.
Ammonia commonly used in closed-cycle OTEC.
OTEC is renewable and non-polluting.
Tropical oceans are suitable for OTEC.
NIOT works on OTEC in India.
16. Frequently Asked MCQs
1. OTEC stands for:
A. Ocean Thermal Electric Current
B. Ocean Thermal Energy Conversion
C. Ocean Turbine Energy Cycle
D. Ocean Temperature Energy Control
✅ Answer: B
2. OTEC works using:
A. Ocean waves
B. Tides
C. Temperature difference in ocean water
D. Earthquake energy
✅ Answer: C
3. Common fluid used in closed-cycle OTEC:
A. Oxygen
B. Nitrogen
C. Ammonia
D. Hydrogen
✅ Answer: C
4. OTEC is:
A. Non-renewable
B. Renewable
C. Fossil fuel energy
D. Chemical energy
✅ Answer: B
5. OTEC works best in:
A. Polar regions
B. Desert regions
C. Tropical oceans
D. Mountains
✅ Answer: C
17. Fact-Based Questions
Question 1
Consider the following statements:
OTEC uses warm surface water and cold deep water.
OTEC is renewable.
Ammonia is used in closed-cycle OTEC.
A. Only 1 and 2
B. Only 2 and 3
C. 1, 2 and 3
D. Only 1 and 3
✅ Answer: C
Question 2
Which of the following are advantages of OTEC?
Pollution free
Renewable
Continuous energy supply
A. Only 1 and 2
B. Only 2 and 3
C. 1, 2 and 3
D. Only 1 and 3
✅ Answer: C
Question 3
Consider the following:
OTEC requires tropical oceans.
OTEC efficiency is generally low.
OTEC can produce fresh water.
A. Only 1 and 2
B. Only 2 and 3
C. 1, 2 and 3
D. Only 1 and 3
✅ Answer: C
18. Assertion–Reason Questions
Assertion (A)
OTEC plants work efficiently in tropical regions.
Reason (R)
Tropical oceans have large temperature difference between surface and deep water.
A. Both A and R are true and R explains A
B. Both true but R not explanation
C. A true, R false
D. A false, R true
✅ Answer: A
Assertion (A)
OTEC is considered environment friendly.
Reason (R)
It produces electricity without burning fossil fuels.
A. Both A and R are true and R explains A
B. Both true but R not explanation
C. A true, R false
D. A false, R true
✅ Answer: A
19. Previous Year Type Questions (PYQs)
PYQ 1
Ocean thermal energy is obtained from:
A. Ocean tides
B. Ocean waves
C. Temperature difference in seawater
D. Ocean currents
✅ Answer: C
PYQ 2
The commonly used working fluid in OTEC is:
A. Oxygen
B. Nitrogen
C. Ammonia
D. Carbon dioxide
✅ Answer: C
PYQ 3
OTEC is best suitable in:
A. Polar regions
B. Tropical oceans
C. Deserts
D. Mountain regions
✅ Answer: B
20. Quick Revision Table
| Topic | Important Fact |
|---|---|
| OTEC full form | Ocean Thermal Energy Conversion |
| Main principle | Temperature difference |
| Common working fluid | Ammonia |
| Suitable region | Tropical oceans |
| Energy type | Renewable |
21. One-Liner Revision
| Question | Answer |
|---|---|
| OTEC uses | Warm and cold ocean water |
| Temperature difference needed | About 20°C |
| Common fluid used | Ammonia |
| Suitable region | Tropical oceans |
| Energy type | Renewable |
Conclusion
Ocean Thermal Energy Conversion (OTEC) is a renewable technology that uses the temperature difference between warm surface water and cold deep ocean water to generate electricity. It is environmentally friendly and has huge future potential in tropical countries like India. Understanding OTEC principles, working, advantages, disadvantages, and applications is important for competitive examinations and environmental science.
Prepared By Home Academy