Class 10th Science Chapter 14 – Sources of Energy | Wave Energy

🌊 Sources of Energy

Wave Energy | तरंग ऊर्जा

Class 10 CBSE Science | NCERT + Foundation + Competitive Preparation

🌊 Sources of Energy | Wave Energy

1. Introduction | परिचय

English: Wave energy is the energy obtained from the motion of ocean surface waves. Ocean waves contain mechanical energy that can be converted into useful mechanical or electrical energy.

हिन्दी: तरंग ऊर्जा (Wave Energy) समुद्र की सतह पर बनने वाली तरंगों की गति से प्राप्त ऊर्जा है। समुद्री तरंगों में mechanical energy होती है, जिसे उपयोगी mechanical या electrical energy में बदला जा सकता है।

🌊 Ocean Waves → Mechanical Motion → Turbine / Generator → ⚡ Electricity

Exam Point: Wave energy is different from tidal energy. Wave energy mainly uses the motion of ocean waves, while tidal energy uses the periodic rise, fall or currents associated with tides.

परीक्षा बिंदु: Wave energy और tidal energy अलग हैं। Wave energy समुद्री waves की motion का उपयोग करती है, जबकि tidal energy tides के कारण होने वाले water-level changes या currents का उपयोग करती है।

2. What are Ocean Waves? | समुद्री तरंगें क्या हैं?

Ocean waves are disturbances that travel across the surface of water. They are commonly generated by the transfer of energy from moving air to the ocean surface.

The water particles generally move in orbital or oscillatory paths while the wave transports energy from one location to another.

हिन्दी: समुद्र की सतह पर ऊर्जा के कारण उत्पन्न होने वाली disturbances को ocean waves कहते हैं। सामान्यतः हवा की गति से समुद्र की सतह को ऊर्जा मिलने पर waves बनती हैं।

3. Source of Wave Energy | Wave Energy का स्रोत

For most ocean waves, the ultimate energy source is the Sun. Solar heating causes unequal heating of Earth's surface, producing atmospheric pressure differences and winds. Wind transfers energy to the ocean surface and generates waves.

☀️ Sun → Unequal Heating → 🌬️ Wind → 🌊 Ocean Waves → ⚙️ Wave Energy Converter → ⚡ Electricity

Important: Although wave energy is often classified as ocean energy, the immediate source of most surface-wave energy is wind, while the broader driving energy originates from solar heating of the atmosphere.

4. Animated Wave Energy System | तरंग ऊर्जा प्रणाली

5. Basic Principle | मूल सिद्धांत

Wave energy converters capture the motion of waves. The relative motion of a floating or submerged component can drive a mechanical system, hydraulic system, air chamber or turbine. The mechanical energy is then converted into electrical energy by a generator.

Basic chain:

Wave Motion → Mechanical/Hydraulic/Pneumatic Motion → Generator → Electrical Energy

6. Important Types of Wave Energy Converters

Type	Basic Working
Oscillating Water Column (OWC)	Wave motion changes the water level inside a chamber, compressing and expanding air that drives a turbine.
Point Absorber	A floating device moves mainly up and down with waves and converts relative motion into useful power.
Attenuator	A long floating structure aligned roughly parallel to wave direction flexes at its joints as waves pass.
Overtopping Device	Wave crests carry water into a raised reservoir; the stored water flows back through turbines.

7. Oscillating Water Column | दोलनशील जल स्तंभ

In an Oscillating Water Column system, incoming waves cause the water level inside a chamber to rise and fall. The changing water level compresses and expands the air above it. The moving air passes through a turbine, which drives a generator.

8. Point Absorber | पॉइंट एब्जॉर्बर

A point absorber is generally a floating device that moves relative to a fixed reference or submerged component as waves pass. The up-and-down movement can drive hydraulic, mechanical or electrical power-conversion systems.

Key idea: Wave motion → Relative movement → Power conversion.

9. Attenuator | एटेन्यूएटर

An attenuator is a long floating wave-energy device usually positioned approximately parallel to the direction of wave travel. Its connected sections flex as waves pass along the device. The relative motion at the joints can be converted into useful power.

10. Overtopping Device | ओवरटॉपिंग प्रणाली

In an overtopping device, waves carry water over a ramp into a reservoir located above the surrounding sea level. The stored water can then flow back through low-head turbines to generate electricity.

Energy conversion:

Wave Energy → Potential Energy of Stored Water → Turbine → Generator

11. Wave Energy and Tidal Energy Difference

Wave Energy	Tidal Energy
Uses motion of ocean surface waves.	Uses tidal rise/fall or tidal currents.
Most surface waves are generated mainly by wind.	Tides are mainly associated with gravitational interactions.
Wave conditions vary with weather and sea state.	Tidal cycles are highly predictable.
Uses wave-energy converters.	Uses barrages, tidal-stream turbines or lagoons.

12. Wave Energy and Wind Energy Difference

Wave Energy	Wind Energy
Uses energy stored in ocean waves.	Uses kinetic energy of moving air.
Often available in coastal/ocean regions.	Requires suitable windy locations.
Wave devices operate in a marine environment.	Wind turbines operate on land or offshore.
Maintenance can be difficult because of seawater and storms.	Maintenance is generally easier than for underwater systems, though offshore wind also presents marine challenges.

13. Why is Wave Energy Renewable?

Wave energy is considered renewable because waves are continuously regenerated by natural processes, especially wind generated by solar heating of Earth's atmosphere. The resource is not consumed like coal, petroleum or natural gas.

14. Advantages of Wave Energy | लाभ

• Renewable: Ocean waves are naturally regenerated.
• Low direct emissions during operation: Electricity generation does not require conventional fossil-fuel combustion.
• Large resource: Oceans cover a major portion of Earth's surface and contain substantial wave energy.
• Useful for coastal regions: Wave-energy systems can potentially provide electricity near coastal communities.
• Complementary resource: Wave conditions may provide a useful addition to other renewable-energy sources.
• No fuel transport: The wave itself supplies the mechanical energy.

15. Limitations of Wave Energy | सीमाएँ

• Wave energy technology is technically challenging.
• Marine equipment faces corrosion due to seawater.
• Storms and extreme waves can damage equipment.
• Installation and maintenance can be expensive.
• Power output varies with wave conditions.
• Underwater cables and marine infrastructure require specialised engineering.
• Wave-energy projects may interact with marine ecosystems and navigation.
• Suitable locations and grid connections are important.

16. Factors Affecting Wave Energy Output

Factor	Effect
Wave Height	Higher waves generally contain more available wave energy.
Wave Period	Longer-period waves can carry substantial energy and influence device performance.
Wave Direction	Device orientation affects how efficiently waves are captured.
Wave Frequency	Converter design must match the range of wave frequencies at the site.
Weather / Storms	Extreme conditions can increase output temporarily but also increase structural loads and damage risk.

17. Wave Energy Concept | तरंग ऊर्जा की अवधारणा

🌞 Solar Heating
↓
🌬️ Winds
↓
🌊 Ocean Waves
↓
⚙️ Wave Energy Converter
↓
🔄 Generator
↓
⚡ Electrical Energy

18. Important Terms | महत्वपूर्ण शब्द

Term	Meaning
Wave	A disturbance that transfers energy through the ocean surface.
Wave Energy	Energy available from ocean wave motion.
Wave Energy Converter	Device that captures wave motion and converts it into useful power.
Oscillating Water Column	System using changing water level and air movement to drive a turbine.
Point Absorber	Floating device that captures relative motion caused by waves.
Attenuator	Long floating device whose sections flex with passing waves.
Overtopping Device	System that stores wave-driven water at an elevated level before it flows through turbines.

19. 30 MCQs | बहुविकल्पीय प्रश्न

1. Wave energy is obtained mainly from:

A. Motion of ocean waves

B. Burning coal

C. Nuclear fission

D. Underground heat

Answer: A

2. Most ocean surface waves are generated mainly by:

A. Earthquakes only

B. Wind

C. Volcanoes

D. Tides alone

Answer: B

3. The broader energy source driving atmospheric winds is:

A. Coal

B. Moonlight

C. Solar heating

D. Petroleum

Answer: C

4. Wave energy is classified as:

A. Fossil energy

B. Nuclear energy

C. Non-renewable energy

D. Renewable energy

Answer: D

5. An Oscillating Water Column uses changing:

A. Water level and air pressure

B. Coal pressure

C. Nuclear pressure

D. Soil temperature only

Answer: A

6. In an OWC system, moving air can drive a:

A. Solar panel

B. Turbine

C. Battery

D. Transformer only

Answer: B

7. A point absorber generally captures:

A. Underground heat

B. Solar radiation directly

C. Relative motion caused by waves

D. Coal combustion

Answer: C

8. An overtopping device first stores:

A. Coal

B. Compressed gas

C. Steam

D. Water at an elevated level

Answer: D

9. Which machine commonly converts mechanical energy into electrical energy?

A. Generator

B. Battery

C. Fuse

D. Capacitor

Answer: A

10. Wave energy differs from tidal energy because wave energy mainly uses:

A. Earth's internal heat

B. Ocean surface-wave motion

C. Coal combustion

D. Nuclear energy

Answer: B

11. An attenuator is generally:

A. A floating wave-energy device

B. A coal furnace

C. A nuclear reactor

D. A solar battery

Answer: A

12. A major challenge for wave-energy equipment is:

A. Lack of gravity

B. Seawater corrosion

C. Lack of ocean waves everywhere

D. Absence of sunlight at noon

Answer: B

13. Which condition can damage wave-energy devices?

A. Gentle breeze only

B. Normal humidity

C. Severe storms

D. Ordinary daylight

Answer: C

14. Wave energy is a form of:

A. Ocean energy

B. Fossil energy

C. Nuclear energy

D. Chemical energy

Answer: A

15. Which factor affects the amount of wave energy available?

A. Wave height

B. Colour of seawater

C. Shape of clouds only

D. Soil pH

Answer: A

16. A wave-energy converter is used to:

A. Produce coal

B. Capture wave motion

C. Stop ocean currents

D. Produce uranium

Answer: B

17. In an overtopping system, stored water has:

A. Chemical energy only

B. Nuclear energy

C. Gravitational potential energy

D. No energy

Answer: C

18. Which energy conversion is correct for an overtopping system?

A. Wave energy → stored water → turbine → electricity

B. Coal → wave → electricity

C. Electricity → coal → wave

D. Nuclear energy → wave

Answer: A

19. Most surface waves receive their immediate energy mainly from:

A. Wind

B. Uranium

C. Coal

D. Earth's core

Answer: A

20. A major advantage of wave energy is:

A. It requires continuous coal supply

B. It is renewable

C. It produces petroleum

D. It needs no equipment

Answer: B

21. Which is a limitation of wave energy?

A. Marine maintenance can be difficult

B. It is always available at the same power

C. It requires no engineering

D. It can work without waves

Answer: A

22. Wave-energy systems are especially associated with:

A. Ocean and coastal regions

B. Dry deserts only

C. Underground mines

D. Polar ice only

Answer: A

23. Which is NOT a wave-energy converter type?

A. Point absorber

B. Attenuator

C. Oscillating Water Column

D. Coal boiler

Answer: D

24. Wave energy ultimately depends mainly on:

A. Solar-driven atmospheric processes for most surface waves

B. Coal formation

C. Nuclear fission

D. Petroleum combustion

Answer: A

25. The movement of a point absorber can be converted into:

A. Useful power

B. Coal

C. Petrol

D. Uranium

Answer: A

26. In an OWC, air movement can be used to:

A. Rotate a turbine

B. Produce coal

C. Stop tides

D. Freeze seawater

Answer: A

27. Which factor can affect the performance of a wave-energy device?

A. Wave direction

B. Classroom temperature

C. Soil colour

D. Road width

Answer: A

28. Wave energy is different from wind energy because:

A. Wave energy uses ocean-wave motion

B. Wind energy uses seawater

C. Wave energy is non-renewable

D. Wind energy uses coal

Answer: A

29. The main role of a generator in a wave-energy plant is to:

A. Convert mechanical energy into electrical energy

B. Create waves

C. Produce wind

D. Store coal

Answer: A

30. Which sequence is correct?

A. Waves → Converter → Generator → Electricity

B. Electricity → Waves → Coal

C. Coal → Waves → Generator

D. Uranium → Waves → Electricity

Answer: A

20. 30 Subjective Questions with Answers

2 Marks Q1. What is wave energy?

Wave energy is the energy obtained from the motion of ocean surface waves and converted into useful mechanical or electrical energy.

2 Marks Q2. What is an ocean wave?

An ocean wave is a disturbance that travels across the surface of seawater and transfers energy.

2 Marks Q3. What is the immediate source of energy for most ocean surface waves?

The immediate source is wind, which transfers energy to the ocean surface.

2 Marks Q4. Why is wave energy called renewable?

Waves are naturally regenerated by atmospheric and ocean processes, so the resource is continually replenished.

2 Marks Q5. What is a wave-energy converter?

It is a device that captures the motion of ocean waves and converts it into useful mechanical or electrical power.

3 Marks Q6. Explain the basic principle of wave energy conversion.

A wave causes mechanical movement of a floating, submerged or enclosed component. This movement drives a mechanical, hydraulic or pneumatic system, which ultimately drives a generator to produce electricity.

3 Marks Q7. What is an Oscillating Water Column?

It is a wave-energy system in which wave-induced water-level changes cause air above the water to move back and forth through a turbine, producing mechanical power.

3 Marks Q8. What is a point absorber?

A point absorber is a floating wave-energy device that captures relative motion caused by waves and converts that motion into useful power.

3 Marks Q9. What is an attenuator?

An attenuator is a long floating wave-energy device whose connected sections flex as waves pass, allowing the relative motion to be converted into power.

3 Marks Q10. What is an overtopping device?

It is a wave-energy system that directs wave-driven water into an elevated reservoir. The stored water then flows through turbines to generate electricity.

4 Marks Q11. Explain how solar energy is indirectly related to wave energy.

Solar heating causes unequal heating of Earth's surface. This creates pressure differences and winds. Winds transfer energy to ocean water and generate waves. Wave-energy devices then capture this energy.

4 Marks Q12. Explain the working of an Oscillating Water Column.

Incoming waves make the water level inside a chamber rise and fall. This movement compresses and expands the air above the water. The moving air passes through a turbine, which drives a generator and produces electricity.

4 Marks Q13. Differentiate between wave energy and tidal energy.

Wave energy uses ocean surface-wave motion, usually generated mainly by wind. Tidal energy uses periodic tidal water-level changes or tidal currents caused mainly by gravitational interactions. Tidal cycles are generally more predictable than wave conditions.

4 Marks Q14. Write four advantages of wave energy.

It is renewable, does not require fossil-fuel combustion during normal operation, has a large ocean resource and can provide useful energy for suitable coastal areas.

4 Marks Q15. Write four limitations of wave energy.

Marine corrosion, storm damage, high installation and maintenance costs, variable wave conditions and possible environmental impacts are important limitations.

5 Marks Q16. Explain the complete energy conversion chain of wave energy.

Solar heating indirectly drives atmospheric winds. Wind transfers energy to the ocean surface and creates waves. Wave motion is captured by a wave-energy converter. The mechanical, hydraulic or pneumatic motion is used to drive a generator, which produces electrical energy.

5 Marks Q17. Explain the construction and working principle of an OWC system.

An OWC has a chamber open to the sea below the water level and an air passage connected to a turbine. As waves enter, the water column rises and compresses air. As the wave retreats, the water level falls and air moves in the opposite direction. The air movement drives a turbine connected to a generator.

5 Marks Q18. Explain the advantages and limitations of wave energy.

Advantages include renewable supply, large ocean resource, low direct emissions during generation and suitability for some coastal locations. Limitations include corrosion, storm loads, variable wave conditions, expensive marine maintenance and possible effects on marine environments.

5 Marks Q19. Why is maintenance of wave-energy equipment difficult?

Wave-energy equipment operates in a harsh marine environment. Saltwater can cause corrosion, strong waves and storms can create large mechanical loads, and underwater equipment and cables can be difficult and expensive to access.

5 Marks Q20. How does an overtopping wave-energy device work?

Wave crests carry water over a ramp into an elevated reservoir. The stored water has gravitational potential energy. When it flows back toward the sea through turbines, the turbines drive generators to produce electricity.

6 Marks Q21. Describe wave energy in detail.

Wave energy is obtained from the motion of ocean surface waves. Most waves are generated by wind, whose energy ultimately comes mainly from solar heating of Earth's atmosphere. Wave-energy converters capture wave motion using devices such as point absorbers, attenuators, Oscillating Water Columns and overtopping systems. The captured energy is converted into mechanical motion and then electricity. Wave energy is renewable but faces challenges such as corrosion, storms, variable wave conditions and high marine maintenance costs.

6 Marks Q22. Compare wave energy, tidal energy and wind energy.

Wave energy uses ocean surface waves, tidal energy uses tidal water-level changes or currents, and wind energy uses moving air. Most surface waves are generated mainly by wind; tides are mainly driven by gravitational interactions. Tidal cycles are highly predictable, while wave and wind conditions vary with weather and sea state. All three can be renewable energy sources.

6 Marks Q23. Explain four types of wave-energy converters.

Point absorbers capture relative floating motion. Attenuators use flexible sections that move with passing waves. Oscillating Water Columns use changing water levels to move air through turbines. Overtopping systems collect wave-driven water in elevated reservoirs and release it through turbines.

6 Marks Q24. Why is wave energy considered an indirect form of solar energy?

Solar radiation heats Earth's surface unevenly, producing atmospheric pressure differences and winds. Wind transfers energy to ocean water and creates waves. Therefore, much of the energy contained in ordinary surface waves can ultimately be traced to solar heating.

6 Marks Q25. Discuss the environmental aspects of wave-energy projects.

Wave-energy projects do not require fossil-fuel combustion during normal operation, but marine structures can interact with habitats, marine organisms, sediment movement and navigation. Underwater cables and structures may also affect the local environment. Proper site selection and environmental assessment are therefore important.

6 Marks Q26. What factors determine the suitability of a location for wave-energy generation?

Important factors include wave height, wave period, wave direction, seasonal variation, storm frequency, water depth, seabed conditions, distance from the coast and electrical grid, environmental sensitivity and maintenance accessibility.

6 Marks Q27. Explain why wave height is important in wave-energy generation.

Wave height indicates the size of the wave and strongly affects the amount of energy available. Larger waves generally contain more energy, although very extreme waves can also create excessive mechanical loads on equipment.

6 Marks Q28. Why can wave energy not be generated at the same rate throughout the year?

Wave conditions change with weather, wind speed, storms, seasons and ocean conditions. Therefore, wave height, period and direction vary, causing the available power and converter output to vary with time.

6 Marks Q29. Why are oceans suitable locations for wave-energy systems?

Oceans cover a large area and continuously receive energy from atmospheric winds. Long fetches allow waves to develop and carry substantial mechanical energy, making suitable coastal and offshore regions potential locations for wave-energy systems.

6 Marks Q30. Write an exam-ready note on Wave Energy.

Wave energy is renewable energy obtained from ocean surface waves. Most ordinary surface waves are generated by wind, whose energy ultimately comes mainly from solar heating. Wave-energy converters such as point absorbers, attenuators, Oscillating Water Columns and overtopping systems capture wave motion and convert it into electricity. It is renewable and has a large resource potential, but marine corrosion, storms, variable wave conditions, cost and environmental considerations are important challenges.

21. Assertion–Reason | कथन–कारण

Q1. Assertion: Wave energy is a renewable source.
Reason: Ocean waves are naturally regenerated.

Answer: Both Assertion and Reason are true, and the Reason correctly explains the Assertion.

Q2. Assertion: Most ordinary ocean surface waves are generated mainly by wind.
Reason: Wind transfers energy to the ocean surface.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q3. Assertion: An OWC can use air movement to generate electricity.
Reason: Wave-induced water-level changes cause air to move through a turbine.

Answer: Both are true, and the Reason correctly explains the Assertion.

Q4. Assertion: Wave energy output is perfectly constant.
Reason: Wave height and period vary with weather and sea conditions.

Answer: Assertion is false, but Reason is true.

Q5. Assertion: Marine corrosion is a challenge for wave-energy systems.
Reason: Wave-energy equipment is exposed to seawater and a harsh marine environment.

Answer: Both are true, and the Reason correctly explains the Assertion.

22. HOTS / Competency-Based Questions

HOTS 1: Why can a very large wave be both useful and dangerous for a wave-energy device?

A large wave may contain substantial energy and increase power capture, but it can also produce very large mechanical loads that may damage the device.

HOTS 2: Why is an OWC suitable for converting wave motion into air movement?

The water level inside the chamber rises and falls with waves, compressing and expanding the air above it. This creates a reciprocating airflow that can drive a turbine.

HOTS 3: Why is wave energy not exactly the same as wind energy even though wind generates many waves?

Wind energy directly captures the kinetic energy of moving air, whereas wave energy captures mechanical energy stored in ocean waves after wind has transferred energy to the water.

HOTS 4: Why should wave-energy devices be designed for extreme storms?

Storms can produce unusually large waves and forces. A device that works efficiently in normal conditions must also survive extreme loads to remain safe and economically useful.

HOTS 5: Why can wave energy be considered indirectly related to solar energy?

Solar heating drives atmospheric circulation and winds. Winds transfer energy to ocean water and create waves. Therefore, the energy in many surface waves ultimately originates from solar energy.

23. Golden Points | परीक्षा के लिए महत्वपूर्ण बिंदु

• Wave energy comes from the motion of ocean waves.
• Most ordinary surface waves are generated mainly by wind.
• Wind energy ultimately depends mainly on solar heating of the atmosphere.
• Wave energy is renewable.
• Wave energy is different from tidal energy.
• Wave-energy converters capture mechanical wave motion.
• Oscillating Water Column uses changing water level and air movement.
• Point absorber captures relative motion.
• Attenuator uses flexible connected sections.
• Overtopping devices store wave-driven water at an elevated level.
• Generators convert mechanical energy into electrical energy.
• Wave height and period influence available energy.
• Seawater corrosion is a major engineering challenge.
• Storms can produce severe loads on equipment.
• Wave-energy output varies with sea conditions.

24. One-Minute Revision | एक मिनट में Revision

☀️ Sun
↓
🌬️ Wind
↓
🌊 Ocean Waves
↓
⚙️ Wave Energy Converter
↓
🔄 Generator
↓
⚡ Electricity

Energy Source: Ocean waves
Immediate source: Wind for most ordinary surface waves
Ultimate driver: Solar heating of atmosphere
Devices: Point Absorber, Attenuator, OWC, Overtopping
Output: Mechanical / Electrical energy
Nature: Renewable
Main challenges: Corrosion, storms, variable waves, cost and marine environment

25. Concept Map | अवधारणा मानचित्र

26. Final Summary | अंतिम सारांश

Wave energy is the energy available from the movement of ocean surface waves. Most ordinary surface waves are generated by wind, and the energy driving atmospheric winds ultimately comes mainly from solar heating.

Wave-energy converters such as Oscillating Water Columns, point absorbers, attenuators and overtopping systems capture wave motion and convert it into useful mechanical or electrical energy.

Wave energy is renewable and has a large ocean resource, but practical challenges include seawater corrosion, storms, variable wave conditions, marine maintenance, cost and environmental considerations.

Final Memory Line:

🌊 Waves → Converter → Generator → Electricity

📘 Class 10 CBSE Science
Sources of Energy | Wave Energy
NCERT + Foundation + Competitive Preparation