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Science and Technology for AP Exams · Chapter 4

Energy: Conventional, Renewable and Nuclear

What to remember

  • Coal is still the main source of India's electricity. Renewable energy, nuclear power and hydro power add to it, and the country is moving step by step towards clean energy.
  • India's nuclear programme has three stages: natural uranium with heavy water reactors, then fast breeder reactors using plutonium, then thorium-based reactors. The plan is built around India's large thorium reserves.
  • Renewable sources (solar, wind, biomass, small hydro) are growing fast. The International Solar Alliance, the National Solar Mission and energy-saving schemes show the national direction.

Basics of energy sources

Energy sources are grouped in two ways. Conventional (non-renewable) sources are coal, petroleum and natural gas. They took millions of years to form and will finish one day. Non-conventional (renewable) sources are solar, wind, tidal, geothermal, biomass and small hydro. They renew themselves naturally.

Fossil fuels are made from the remains of plants and animals buried under heat and pressure. When they burn they release carbon dioxide, sulphur dioxide and nitrogen oxides. This causes global warming and acid rain. This is the main reason the world is moving to cleaner energy.

Coal, oil and gas

Coal forms in stages: peat, lignite, bituminous and anthracite. Carbon content rises along this order. Anthracite is the best quality and has the highest carbon. Most Indian coal is bituminous, with high ash. Coal is burnt in thermal power plants to boil water; the steam turns a turbine, and the turbine turns a generator.

Petroleum is crude oil found in sedimentary rocks. It is separated in refineries by fractional distillation into petrol, diesel, kerosene, LPG and other products. Natural gas is mainly methane. It is sold as CNG (compressed natural gas) for vehicles and PNG (piped natural gas) for homes. LPG is mainly propane and butane.

India imports a large share of its crude oil. For this reason the country keeps strategic petroleum reserves in underground rock caverns, with sites on the east and west coasts. Coastal Andhra Pradesh has deepwater gas in the Krishna-Godavari basin, and Visakhapatnam has a major refinery.

Hydro power

Hydro power uses the potential energy of stored water. Water falls through pipes called penstocks, turns turbines, and the turbine runs a generator. A dam is needed for storage. Hydro power gives no air pollution and can start and stop quickly, so it is used to meet peak demand.

Disadvantages are land submergence, displacement of people and effects on rivers. Pumped storage plants pump water to an upper reservoir when demand is low, and release it when demand is high; they work like a large battery. Srisailam on the Krishna river is a well-known hydro project in Andhra Pradesh and Telangana, and Simhadri near Visakhapatnam is a coal-based thermal station. Small hydro projects (generally up to 25 MW) are counted as renewable.

Nuclear energy

Fission is the splitting of a heavy nucleus (uranium-235 or plutonium-239) into smaller nuclei when hit by a neutron. It releases a very large amount of energy and more neutrons, which keep the chain reaction going. Fusion is the joining of light nuclei such as hydrogen isotopes; it powers the Sun and is not yet used for power on Earth.

Parts of a reactor: fuel (uranium), moderator (slows neutrons; heavy water or graphite), control rods (absorb neutrons; boron or cadmium), coolant (removes heat) and a strong containment building. Pressurised Heavy Water Reactors (PHWR) use natural uranium and heavy water. Light water reactors use enriched uranium. Kudankulam in Tamil Nadu has Russian-designed light water reactors.

India's three-stage programme, planned by Homi J. Bhabha:

StageReactorFuelOutput
1PHWRNatural uraniumElectricity and plutonium-239
2Fast Breeder ReactorPlutonium and uraniumElectricity and uranium-233 from thorium
3Thorium-based reactorsUranium-233 and thoriumLong-term electricity

India has very large thorium reserves, mostly in beach sands of Kerala, Tamil Nadu, Odisha and also coastal Andhra Pradesh. This is why the thorium route matters. The Atomic Energy Commission and the Department of Atomic Energy lead the programme, and the Nuclear Power Corporation of India Limited runs the power reactors. The Atomic Energy Regulatory Board is the safety regulator. Nuclear waste is handled by storage and reprocessing.

Renewable energy

Solar: photovoltaic (PV) cells change sunlight directly into electricity. Solar thermal systems use mirrors to heat a fluid. The National Solar Mission (2010) aims to make India a leader in solar power. The International Solar Alliance, started by India and France, is for countries rich in sunshine; its headquarters is in India. Rooftop solar and solar pumps for farmers are supported by schemes such as PM-KUSUM.

Wind: wind turns blades connected to a generator. Tamil Nadu, Gujarat and Karnataka are leading wind states, and Andhra Pradesh also has wind and solar parks, with Rayalaseema regions suited for both.

Biomass and biogas: farm waste, cattle dung and wood are used. Biogas is mainly methane produced by anaerobic digestion. Biofuels such as ethanol blended with petrol are encouraged to cut oil imports.

Others: tidal energy uses sea level changes; geothermal uses heat from within the Earth; green hydrogen, made by splitting water with renewable electricity, is promoted by the National Green Hydrogen Mission.

SourceMain advantageMain limitation
CoalCheap, plentifulPollution, ash
HydroClean, quick startSubmergence, needs rain
NuclearLarge power, low carbonWaste, safety, cost
SolarFree fuelWorks only in daytime
WindCleanNeeds steady wind

Energy policy and efficiency

The Ministry of Power looks after electricity and the Ministry of New and Renewable Energy looks after renewables. The Energy Conservation Act created the Bureau of Energy Efficiency (BEE). BEE runs the star labelling programme for appliances; a higher star means lower electricity use. The UJALA scheme distributed LED bulbs. The Perform, Achieve and Trade (PAT) scheme sets energy-saving targets for large industries and lets them trade certificates. The Energy Conservation Building Code sets rules for efficient buildings.

India has set a long-term goal of net-zero emissions and has promised to raise the share of non-fossil power in its capacity. Smart grids, battery storage and electric vehicles support this goal.

Andhra Pradesh has a long coast, strong sun and good wind areas. The state promotes solar parks, wind projects, pumped storage and green hydrogen plans. Check the latest official release for current project names and capacities.

Electricity grid and energy security

Power is made at generating stations, sent over high-voltage transmission lines and then lowered by transformers for homes and factories. The lines form a grid. India has one national grid, so surplus power in one region can be sent to another. Electricity is a concurrent subject, so both the Centre and the states make rules for it. Losses during transmission and distribution (called T&D losses) are an old problem, and smart meters and better lines are used to reduce them.

Energy security means having enough energy at an affordable price at all times. India tries to achieve it by using many sources, building storage and reserves, saving energy and making more of its own fuel. Coal gasification turns coal into a gas that burns more cleanly, and clean coal methods try to cut the pollution from thermal plants. Chimneys in thermal plants use filters called electrostatic precipitators to catch ash. Fly ash can be used to make bricks and cement, which reduces waste. Solar and wind power need a strong grid and storage such as batteries, because sunlight and wind change during the day.

Quick comparison: fossil fuels in use

Coal is used mainly for power and steel making. Petroleum is used mostly for transport and as raw material for plastics and fertilisers. Natural gas is used for power, fertiliser plants and as a cleaner fuel at home. Among the three, coal gives the most carbon dioxide for each unit of energy and natural gas gives the least. This is why gas is called a bridge fuel on the way to cleaner energy.

Exam traps

  • Fusion powers the Sun; fission is used in reactors today.
  • Heavy water is a moderator, not a fuel; control rods absorb neutrons.
  • Stage 2 uses plutonium as fuel (thorium only as a blanket to breed uranium-233); thorium-based fuel is Stage 3.
  • Anthracite has the highest carbon; lignite and peat have less.
  • LPG is propane and butane; CNG is mainly methane.
  • Bhabha planned the programme; Bhabha Atomic Research Centre is the main research centre, while NPCIL runs power plants.
  • BEE does labelling; the Ministry of New and Renewable Energy handles solar and wind.
  • Pumped storage stores energy; it does not create new energy.

One-liners

  • Fossil fuels release carbon dioxide when burnt.
  • Coal is the largest source of power in India.
  • Petroleum is separated by fractional distillation.
  • Biogas is mainly methane.
  • A moderator slows down neutrons.
  • Control rods use boron or cadmium.
  • The first stage of India's nuclear programme uses PHWRs.
  • India's thorium reserves are large.
  • The International Solar Alliance has its headquarters in India.
  • BEE gives star ratings to appliances.
  • UJALA promoted LED bulbs.
  • Srisailam is a hydro project on the Krishna.

Practice questions

  1. Which form of coal has the highest carbon content?

    1. Bituminous
    2. Peat
    3. Lignite
    4. Anthracite
    Answer

    D. Anthracite

    Carbon content rises from peat to lignite to bituminous to anthracite.

  2. Natural gas used in vehicles as CNG is mainly composed of which gas?

    1. Propane
    2. Methane
    3. Butane
    4. Ethane
    Answer

    B. Methane

    CNG is compressed natural gas, which is mostly methane.

  3. Crude oil is separated into petrol, diesel and kerosene by which process?

    1. Sedimentation
    2. Filtration
    3. Electrolysis
    4. Fractional distillation
    Answer

    D. Fractional distillation

    Refineries separate crude oil fractions by their boiling points using fractional distillation.

  4. In a nuclear reactor, the material that slows down neutrons is called the

    1. Control rod
    2. Moderator
    3. Coolant
    4. Fuel
    Answer

    B. Moderator

    Heavy water or graphite acts as moderator and slows neutrons.

  5. Which material is commonly used in control rods to absorb neutrons?

    1. Iron
    2. Copper
    3. Aluminium
    4. Boron
    Answer

    D. Boron

    Boron and cadmium absorb neutrons and control the chain reaction.

  6. The process that powers the Sun is

    1. Nuclear fission
    2. Nuclear fusion
    3. Combustion
    4. Radioactive decay
    Answer

    B. Nuclear fusion

    The Sun joins hydrogen nuclei in nuclear fusion.

  7. Who planned India's three-stage nuclear power programme?

    1. C. V. Raman
    2. Homi J. Bhabha
    3. Vikram Sarabhai
    4. A. P. J. Abdul Kalam
    Answer

    B. Homi J. Bhabha

    Homi J. Bhabha designed the three-stage plan.

  8. The first stage of India's nuclear programme uses which type of reactor?

    1. Thorium reactor
    2. Fusion reactor
    3. Fast breeder reactor
    4. Pressurised heavy water reactor
    Answer

    D. Pressurised heavy water reactor

    Stage 1 uses PHWRs with natural uranium.

  9. Which fuel is mainly used in the second stage of the Indian nuclear programme?

    1. Natural uranium alone
    2. Coal
    3. Heavy water
    4. Plutonium
    Answer

    D. Plutonium

    Fast breeder reactors use plutonium recovered from Stage 1.

  10. India's long-term nuclear plan depends on which abundant resource?

    1. Helium
    2. Thorium
    3. Lithium
    4. Radium
    Answer

    B. Thorium

    India has large thorium reserves in coastal beach sands.

  11. Which body is the safety regulator for nuclear facilities in India?

    1. BARC
    2. NPCIL
    3. Atomic Energy Regulatory Board
    4. ISRO
    Answer

    C. Atomic Energy Regulatory Board

    AERB regulates nuclear and radiation safety.

  12. The International Solar Alliance was launched by India and which other country?

    1. Germany
    2. France
    3. Japan
    4. Russia
    Answer

    B. France

    India and France started the alliance for sunshine-rich countries.

  13. Photovoltaic cells convert

    1. Wind into light
    2. Heat into sound
    3. Water into fuel
    4. Sunlight directly into electricity
    Answer

    D. Sunlight directly into electricity

    PV cells use the photovoltaic effect to produce electric current from light.

  14. Biogas is mainly composed of

    1. Carbon monoxide
    2. Methane
    3. Oxygen
    4. Hydrogen sulphide
    Answer

    B. Methane

    Anaerobic digestion of dung and waste gives mainly methane.

  15. Star labelling of electrical appliances in India is run by the

    1. Bureau of Energy Efficiency
    2. Central Electricity Authority
    3. NITI Aayog
    4. Ministry of Coal
    Answer

    A. Bureau of Energy Efficiency

    BEE runs the standards and labelling programme.

  16. Which scheme promoted the distribution of LED bulbs at low cost?

    1. PAT
    2. Swachh Bharat
    3. UJALA
    4. PM-KUSUM
    Answer

    C. UJALA

    UJALA is the LED distribution programme.

  17. The Perform, Achieve and Trade scheme mainly targets

    1. Farmers
    2. Households
    3. Schools
    4. Large energy-intensive industries
    Answer

    D. Large energy-intensive industries

    PAT sets energy-saving targets for big industries with tradable certificates.

  18. Pumped storage hydro plants are useful because they

    1. Need no dam
    2. Store energy for use at peak demand
    3. Burn less coal in boilers
    4. Create new water
    Answer

    B. Store energy for use at peak demand

    They pump water up when demand is low and release it at peak demand.

  19. Hydro power plants use which part to carry water to the turbine?

    1. Penstock
    2. Chimney
    3. Boiler
    4. Condenser
    Answer

    A. Penstock

    Penstocks are the pipes that carry water to the turbine.

  20. Which of the following is a non-renewable source of energy?

    1. Tidal
    2. Wind
    3. Natural gas
    4. Geothermal
    Answer

    C. Natural gas

    Natural gas is a fossil fuel and will be exhausted.

  21. Burning fossil fuels mainly causes which problem?

    1. Ozone formation in soil
    2. Loss of tides
    3. Rise in soil nitrogen
    4. Global warming and acid rain
    Answer

    D. Global warming and acid rain

    Burning releases carbon dioxide, sulphur dioxide and nitrogen oxides.

  22. The Krishna-Godavari basin in coastal Andhra Pradesh is best known for

    1. Coal seams
    2. Bauxite mining
    3. Natural gas
    4. Uranium mines
    Answer

    C. Natural gas

    The KG basin has deepwater natural gas.

  23. Which of the following reactors in India is of Russian design and located in Tamil Nadu?

    1. Narora
    2. Kakrapar
    3. Tarapur
    4. Kudankulam
    Answer

    D. Kudankulam

    Kudankulam uses Russian-designed light water reactors.

  24. Which of the following is a correct pair of reactor part and function?

    1. Coolant - absorbs neutrons
    2. Moderator - slows neutrons
    3. Fuel - removes heat
    4. Control rod - slows neutrons
    Answer

    B. Moderator - slows neutrons

    Only moderator and slowing of neutrons is correctly matched.

  25. Which one of the following is NOT a renewable source of energy?

    1. Coal
    2. Biomass
    3. Small hydro
    4. Solar power
    Answer

    A. Coal

    Coal is a fossil fuel and non-renewable.

  26. A farmer wants to cut diesel use in irrigation. Which support scheme fits best?

    1. Star labelling
    2. UJALA
    3. PAT scheme
    4. PM-KUSUM for solar pumps
    Answer

    D. PM-KUSUM for solar pumps

    PM-KUSUM supports solar pumps for farmers.

  27. Which of the following is an advantage of a hydro power plant over a coal plant?

    1. It works in all droughts
    2. It displaces no people
    3. It gives no air pollution while generating
    4. It needs no dam
    Answer

    C. It gives no air pollution while generating

    Hydro generation emits no flue gas, though dams can displace people.

  28. A country wants to use its large thorium reserves for power. It must develop

    1. Breeder reactors producing uranium-233
    2. Coal gasification
    3. Tidal turbines
    4. Wind farms
    Answer

    A. Breeder reactors producing uranium-233

    Thorium becomes uranium-233 in breeder reactors, which later fuels Stage 3.

  29. Green hydrogen is produced by

    1. Distilling natural gas
    2. Splitting water using renewable electricity
    3. Cracking petroleum
    4. Burning coal in air
    Answer

    B. Splitting water using renewable electricity

    Electrolysis of water with renewable power gives green hydrogen.

  30. Why is an energy source like wind called intermittent?

    1. It cannot be used for electricity
    2. It is not always available at the same level
    3. It is very costly
    4. It is a fossil fuel
    Answer

    B. It is not always available at the same level

    Wind speed varies, so supply changes with time.

  31. Which statement about nuclear fission is correct? 1. It splits a heavy nucleus. 2. It is used in current nuclear power plants.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Fission of uranium or plutonium nuclei is used in present reactors.

  32. Consider the statements: 1. Heavy water is used as a moderator in PHWRs. 2. Control rods are made of heavy water.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Control rods use boron or cadmium, not heavy water.

  33. Consider the statements: 1. The Bureau of Energy Efficiency was created under the Energy Conservation Act. 2. A higher star rating means higher electricity use.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    A higher star rating means better efficiency and lower power use.

  34. Consider the statements about India's nuclear programme: 1. Stage 2 uses fast breeder reactors. 2. Stage 3 is based on thorium.

    1. 1 only
    2. 2 only
    3. Neither 1 nor 2
    4. Both 1 and 2
    Answer

    D. Both 1 and 2

    Both statements describe the three-stage plan correctly.

  35. Consider the statements: 1. Anthracite has less carbon than lignite. 2. Natural gas is mainly methane.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Anthracite has the highest carbon; natural gas is mostly methane.

  36. Consider the statements: 1. Fusion is widely used today in commercial power reactors. 2. Fusion joins light nuclei.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Fusion joins light nuclei but is not yet used commercially for power.

  37. Consider the statements: 1. The International Solar Alliance has headquarters in India. 2. It is meant for countries rich in sunshine.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  38. Consider the statements: 1. Small hydro projects are counted as renewable. 2. Pumped storage plants release stored water at times of high demand.

    1. 1 only
    2. 2 only
    3. Neither 1 nor 2
    4. Both 1 and 2
    Answer

    D. Both 1 and 2

    Both are correct.

  39. Match the energy term with its meaning: 1. PNG - A. Fuel for vehicles 2. CNG - B. Piped gas for homes 3. LPG - C. Propane and butane mix

    1. 1-C, 2-A, 3-B
    2. 1-A, 2-B, 3-C
    3. 1-B, 2-C, 3-A
    4. 1-B, 2-A, 3-C
    Answer

    D. 1-B, 2-A, 3-C

    PNG is piped for homes, CNG is vehicle fuel, LPG is propane and butane.

  40. Match the body with its role: 1. NPCIL - A. Safety regulation 2. AERB - B. Runs nuclear power plants 3. BEE - C. Energy efficiency

    1. 1-B, 2-A, 3-C
    2. 1-C, 2-A, 3-B
    3. 1-B, 2-C, 3-A
    4. 1-A, 2-B, 3-C
    Answer

    A. 1-B, 2-A, 3-C

    NPCIL operates plants, AERB regulates safety, BEE promotes efficiency.

  41. Match the reactor part with its material: 1. Moderator - A. Boron 2. Control rod - B. Heavy water 3. Fuel - C. Uranium

    1. 1-A, 2-B, 3-C
    2. 1-B, 2-C, 3-A
    3. 1-B, 2-A, 3-C
    4. 1-C, 2-B, 3-A
    Answer

    C. 1-B, 2-A, 3-C

    Heavy water slows neutrons, boron absorbs them, uranium is fuel.

  42. Match the fuel with its source type: 1. Biogas - A. Fossil 2. Coal - B. Biomass 3. Ethanol blend - C. Biofuel

    1. 1-A, 2-B, 3-C
    2. 1-B, 2-A, 3-C
    3. 1-B, 2-C, 3-A
    4. 1-C, 2-A, 3-B
    Answer

    B. 1-B, 2-A, 3-C

    Biogas comes from biomass, coal is fossil, ethanol blend is biofuel.

  43. Which of the following is the main drawback of large hydro projects?

    1. Submergence of land and displacement
    2. Carbon emissions from boiler
    3. High fuel cost
    4. Need for nuclear fuel
    Answer

    A. Submergence of land and displacement

    Reservoirs submerge land and can displace people.

  44. Strategic petroleum reserves in India are stored in

    1. Open ponds
    2. Coal mines
    3. Underground rock caverns
    4. Grain godowns
    Answer

    C. Underground rock caverns

    They are stored in underground caverns on the coasts for safety and security.

  45. Thermal power plants produce electricity by

    1. Directly converting light
    2. Splitting water
    3. Using tides
    4. Heating water to steam that turns a turbine
    Answer

    D. Heating water to steam that turns a turbine

    Steam from boilers drives the turbine connected to the generator.

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