4. Renewable and Non-Renewable Energy

📌

CSS GSA — Paper 7, Part-I, Section I, Sub-topic 4: Renewable and Non-Renewable Energy

---

1. Non-Renewable vs Renewable Energy Sources

• Biomass can be lower-carbon under suitable life-cycle conditions (not automatically carbon-neutral)
  • CO₂ released when it burns
  • Offset by CO₂ the plants absorbed while growing (photosynthesis)
• Solar limitation
  • Direct solar energy is available only in the daytime
  • Storage batteries are needed for night use

💡

In simple words: renewable = nature refills it quickly (sun, wind, water, plants, Earth's heat); non-renewable = once it is used up, it is gone for a very long time.

1.1 Key Definitions

💡

In simple words: energy is the fuel in the tank; power is how fast you burn it. Primary energy is what nature gives us; secondary energy is what we make from it (electricity is the best example).

1.2 Classification of Energy Sources

ℹ️

Note: the CSS 2021 question on "non-conventional energy resources in Pakistan" means the newer sources: solar, wind, biomass and similar. Large hydro and nuclear are usually treated as conventional.

1.3 Types of Non-Renewable Sources

• Coal formation: peat is the precursor to coal; principal coal ranks are lignite → sub-bituminous → bituminous → anthracite.
• Environmental effects of burning fossil fuels: sulphur dioxide and nitrogen oxides contribute to acid rain, while carbon dioxide contributes to greenhouse warming. Ozone depletion is a separate process.
• Nuclear energy: commercial reactors use fission of finite nuclear fuel. Operation produces relatively little CO₂ but requires careful radiation safety and radioactive-waste management.

💡

In simple words: fossil fuels are ancient sunshine stored underground; once we burn them they are gone for millions of years. Fission breaks big atoms apart; fusion squeezes small atoms together, which is how the Sun shines.

1.4 Types of Renewable Sources

• Biomass and climate: biomass combustion emits CO₂ and air pollutants. Net climate benefits depend on regrowth, land use, processing and transport; it is not inherently carbon-neutral.
• Solar: photovoltaic panels can generate electricity without batteries; grid-connected systems exchange energy with the grid, while batteries offer backup and storage.
• Hydro and wind: water or wind turns a turbine rotor, and the linked generator converts mechanical energy into electricity.
• Geothermal: electricity can be produced using natural steam, hot water or binary-cycle systems; direct heat use is also possible.
• Environmental balance: renewable sources replenish naturally but may still involve land use, material requirements, ecosystem impacts, equipment costs and intermittency.

ℹ️

Note: hydrogen is an energy carrier (a secondary fuel made using other energy), not a natural energy source.

2. Latest Facts: World and Pakistan

2.1 World

• Renewables overtook coal in 2025 (Ember, Global Electricity Review 2026)
  • Renewables: 33.8% of global electricity
  • Coal: 33.0%
  • First time in modern history that renewables beat coal
• Clean power met all the growth in global electricity demand in 2025
• Solar and wind are expected to overtake nuclear in 2026
• Asia is the only region where renewables have not yet overtaken coal

2.2 Pakistan (Economic Survey 2025-26 and recent data)

• Solar boom in Pakistan
  • Driven by high electricity tariffs, unreliable grid supply and cheap imported panels (more by economics than by policy)
  • Much of it is rooftop and off-grid, so it is hard to track in official data
  • One analyst estimates solar may now supply roughly a quarter of actual electricity consumption
  • Farmers shifting to solar tube wells: agricultural use of grid power fell 42.3% in July–March FY26
• Mix is shifting: RLNG share fell to 13.3% in FY26 (from 17.5%), while imported coal rose to 10.7% (from 7.1%)

⚠️

Pakistan's share figures change every month. In the exam, quote the direction (clean share above 50%, nuclear about 18%, solar rising) and say "recent data" rather than risking exact decimals.

3. LED Lighting (Note)

LEDs are energy-efficient electrical devices, not energy resources: they convert electrical energy into light using a semiconductor.

• LEDs (Light Emitting Diodes) are a form of Solid State Lighting (SSL)
• They are not a renewable energy source
  • They are just an efficient device that uses electric current to produce light
• Directional light source (emits light in a specific direction)
  • Compact fluorescent bulbs emit light/heat in all directions
  • That is why LEDs are more energy-efficient

4. Biotechnology (Linked Topic)

• Biotechnology: use of living organisms, cells or their products to make useful products or solve problems for human benefit
  • Examples: insulin from bacteria, vaccines, antibiotics, high-yield/disease-resistant crops
• Two core principles
  • Genetic Engineering: changing or transferring genes between organisms
  • Bioprocess Engineering: growing microorganisms/cells under controlled conditions

4.1 Types of Biotechnology (by Field)

💡

In simple words: biotechnology means putting living things (bacteria, yeast, plant cells) to work for us, like tiny factories that make medicine, food or fuel.

5. AC vs DC: Why Power Stations Generate AC

• Most household appliances internally use DC (converted through an internal adapter/rectifier)
• Yet power stations generate and transmit AC (Alternating Current), because:
  1. AC voltage can be easily stepped up and down using transformers; DC cannot be transformed this way efficiently
  2. High-voltage transmission over long distances minimizes power loss
     • Power loss = I²R
     • Raising voltage lowers current for the same power, so resistive losses in the lines are cut
     • AC lets stations step voltage up for transmission, then step it down safely for homes
  3. AC generators (alternators) are simpler, cheaper and more efficient to build and maintain at large scale than DC generators
  4. AC motors are simpler and more robust than DC motors for most industrial applications

5.1 AC vs DC at a Glance

💡

In simple words: AC is water sloshing back and forth in a pipe; DC is water flowing steadily one way. Sloshing current is easy to "step up" for the long journey and "step down" for your home.

6. Forms in Which Energy Exists

🧮

Law of conservation of energy: energy cannot be created or destroyed, only transformed from one form to another.

6.1 Energy Conversions (Examples)

Detailed energy flows

• Hydroelectric: stored water potential → moving-water kinetic → turbine mechanical → generator electrical.
• Wind: moving-air kinetic → turbine mechanical → generator electrical.
• Solar PV: sunlight photons → electrical charges in a semiconductor → DC electricity → AC through an inverter when needed.
• Biomass power station: chemical energy → heat → steam/turbine mechanical energy → electricity.
• Geothermal: underground thermal energy → turbine mechanical energy (in power plants) → electrical energy.
• Nuclear fission: nuclear energy → heat → steam/turbine mechanical energy → electricity.
• Two basic kinds: kinetic (energy of motion) and potential (stored energy); every other form is one of these in a different guise

• Efficiency = useful energy out ÷ total energy in × 100%; no conversion is 100% efficient, because some energy always escapes as heat

7. Energy Conservation

• Improve energy efficiency of appliances, vehicles and buildings
  • Insulation
  • LED lighting
  • Efficient motors
• Reduce unnecessary consumption (e.g. switch off unused devices)
• Public transport and carpooling
• Recycling materials: uses far less energy than producing from raw materials
• Smart-grid and demand-management technology
• Government policy and incentives for efficiency standards
• Public awareness campaigns

7.1 Sustainable Use of Energy

• Sustainable energy use: meeting today's energy needs without harming the ability of future generations to meet theirs
• Pillars
  • Efficiency: get the same service from less energy (LED lighting, efficient motors, insulation)
  • Renewables: replace fossil fuels with solar, wind, hydro, biomass and geothermal
  • Conservation: avoid waste; recycle; use public transport
  • Planning: balanced energy mix, storage, smart grids, lower losses
  • Fair access: affordable energy for all (this is Sustainable Development Goal 7)
• Why it matters: fossil fuels are finite and cause climate change; sustainable use cuts emissions, import bills and pollution

7.2 Conservation vs Efficiency

8. LED Mechanism and Uses

• Mechanism
  • An LED is a semiconductor diode
  • When forward-biased (current flows in the allowed direction), electrons and "holes" recombine at the p-n junction
  • The energy is released as photons (light), which is called electroluminescence
  • The colour of light depends on the semiconductor material's band gap energy
• Why LEDs are the modern choice
  • Very high energy efficiency (far less energy lost as heat than incandescent bulbs)
  • Long operational lifespan (tens of thousands of hours)
  • Directional light output (less wasted light)
  • Compact and durable (solid-state, no filament to break)
  • Instant-on, no warm-up time
  • No toxic mercury (unlike CFLs)
• Uses: household/street lighting, electronic displays/screens, traffic signals, vehicle lights, indicator lights

8.1 LED vs Other Lights

9. Benefits of Solar Energy: Different Ways to Harness It

• Benefits
  • Reduces electricity bills
  • Lowers carbon emissions
  • Works in remote/off-grid areas
  • Low maintenance once installed
  • Increasingly cost-competitive with fossil fuels

9.1 Solar Terms and Types of Systems

• Photovoltaic effect: when sunlight hits a semiconductor such as silicon, it knocks electrons loose and they flow as an electric current (DC)
• Inverter: converts the panel's DC into AC for homes and the grid
• Net metering: a home sends its surplus solar power to the grid and is credited for it

💡

In simple words: a solar panel is a sandwich of silicon: sunlight goes in, direct current comes out, and an inverter makes it usable at home.

10. Wind Energy and Wind Farms

• How it is harnessed
  • Wind turns large turbine blades connected to a rotor
  • The rotor spins a generator
  • Kinetic energy of moving air becomes electrical energy
• Wind farm
  • A cluster of many wind turbines installed together (onshore or offshore)
  • Placed where wind is consistently strong and steady
  • Generates electricity at scale and feeds it into the power grid
• Siting considerations
  • Consistent high wind speeds
  • Open, unobstructed terrain (or offshore)
  • Distance from residential areas (noise)
  • Environmental impact assessment (bird/bat migration paths)
• Advantages
  • No fuel cost
  • No emissions during operation
  • Land beneath turbines can still be used for farming/grazing
• Limitations
  • Intermittent (depends on wind availability)
  • Visual/noise concerns
  • High initial installation cost

10.1 Types of Wind Turbines and Wind Farms

• Parts of a turbine: blades → rotor → gearbox → generator (inside the nacelle on top of a tall tower)

💡

In simple words: a wind turbine is a fan working backwards: instead of electricity turning the blades to make wind, the wind turns the blades to make electricity.

🌾 Biomass vs biogas — CSS 2025

• Biomass: Organic matter from living or recently living organisms used as an energy source, e.g., crop residues, wood, animal manure and food waste.
• Biogas: Fuel gas made when microorganisms break down wet biomass without oxygen (anaerobic digestion), usually rich in methane (CH₄) and carbon dioxide (CO₂).
• Conversion methods:
  • Direct combustion: Burn relatively dry biomass for heat, steam or electricity.
  • Anaerobic digestion: Convert wet manure and organic waste into biogas; leftover digestate can be a fertilizer subject to safe handling.
  • Fermentation: Convert suitable sugars/starches into bioethanol.
  • Transesterification: Convert vegetable oils/animal fats into biodiesel.
  • Gasification/pyrolysis: Heat biomass with limited/no oxygen to produce combustible gas, bio-oil and/or biochar.
• Difference: Biomass is the feedstock, whereas biogas is one fuel product made from biomass.
• 5-mark response: Definition and two examples for each → conversion steps → advantages and limitations.

⚡ How energy technologies convert energy — key mechanisms

• Solar photovoltaic (PV): Photons excite charge carriers in a semiconductor junction → direct current (DC) → inverter converts to AC for ordinary grid use.
• Solar thermal: Sunlight produces heat; thermal collectors heat water or concentrating mirrors make steam to drive a turbine.
• Wind turbine: Moving air turns blades → rotor drives generator → electrical energy. Extractable wind power approximately P = ½ρAv³Cₚ, where ρ = air density, A = swept area, v = wind speed, Cₚ = power coefficient.
• Hydroelectric: Water at height has gravitational potential energy → moving water spins turbine → generator. Ideal hydraulic power P = ρgQH; actual output = ηρgQH.
• Geothermal: Earth's heat supplies hot water/steam or heats working fluid to drive turbines; ground-source heat pumps instead transfer heat using electricity.
• Energy conservation vs efficiency: Conservation reduces unnecessary use; efficiency provides the same useful service with less input energy.
• Energy units: Power = energy/time (W = J/s); energy = power × time (1 kWh = 3.6 million joules).

11. MCQ Traps

🚨

• LED is NOT a renewable energy source; it is only an efficient lighting device (a common trap question)
• Nuclear is non-renewable (uranium is finite), even though it is often wrongly grouped with "clean renewables"
• Biomass is renewable and roughly carbon-neutral despite releasing CO₂ when burned
• Hydal and wind generate electricity by the same mechanism (rotating turbines) but from different driving forces (falling/flowing water vs moving air)
• Nuclear is "low-carbon", not "renewable": Pakistan's clean share (53.1%) includes nuclear
• Conservation = using less; efficiency = doing the same job with less energy
• Fission splits heavy nuclei (used in plants); fusion joins light nuclei (the Sun; not yet commercial)
• Thar coal is lignite (low rank); anthracite is the highest-rank coal
• Hydrogen is an energy carrier, not a natural source; pumped storage works like a giant battery
• The most common wind turbine is the horizontal-axis type

12. Self-Test Questions

1. List three non-renewable and five renewable energy sources.
2. Explain why nuclear energy is classified as non-renewable.
3. Explain why biomass energy is considered close to carbon-neutral.
4. Why is an LED not classified as a renewable energy source?
5. Describe the two core principles of biotechnology with one example each.
6. Most household appliances utilize 'DC', so why do we generate 'AC' at the power stations?
7. What are the different forms in which energy exists?
8. How can energy be conserved?
9. What is the mechanism of LED? What are its uses that make it a choice in the modern age?
10. What are the different ways to get benefits from solar energy?
11. What do you know about wind energy and its harnessing? Also describe a wind farm.
12. Define energy and power, and classify energy sources in four ways.
13. Differentiate between nuclear fission and fusion.
14. Differentiate between energy conservation and energy efficiency, with examples.
15. Compare AC and DC, and name the types of solar power systems.

13. Past-Paper MCQs (FPSC)

✅

Taken from the FPSC papers you shared (2015–2025). FPSC does not publish MCQ keys, so the answers are worked out by me. Chapter 4 had only one direct MCQ in these papers.

1. (CSS 2025, Q1.3) Which of the following source of energy is caused by uneven heating of earth’s surface? (A) Wind (B) Solar (C) Biomass (D) None of these

• ✅ Answer key
  1. (A) Wind (uneven heating of Earth's surface creates pressure differences, and air moves from high to low pressure)

14. Past-Paper Long Questions with Answers (FPSC)

📝

Mark-wise model answers: Only the past-paper questions already listed in this chapter have been refined. All are 5-mark questions; answers are concise, structured, and matched to each question's command words. Where a question has two or more parts, marks are apportioned for revision. These are model answers, not official FPSC marking schemes.

• CSS 2019 Q3(a), 2020 Q2(d), 2022 Q2(b) — Differentiate between renewable and non-renewable sources of energy, with examples. (5 marks)

  Introduction: Energy resources are classified by whether natural processes replenish them on a human timescale.

  Basis	Renewable resources	Non-renewable resources
  Meaning	Replenished naturally	Finite stocks; replenished extremely slowly
  Examples	Sunlight, wind, flowing water, biomass	Coal, oil, natural gas, uranium
  Environmental effects	Usually lower lifecycle emissions, though not impact-free	Fossil fuels emit CO₂ and air pollutants; nuclear fuel creates radioactive waste
  Operation	Solar/wind output varies; hydropower can be flexible	Fuel-based plants can often be dispatched on demand
  Fuel cost	Sunlight and wind have no fuel bill	Continuous fuel supply and cost required

  Example: Solar panels use incoming radiation, whereas coal-fired stations consume geological deposits accumulated over millions of years.

  Conclusion: Renewable sources help long-term sustainability; non-renewables remain useful but face depletion or waste-management challenges.

  Examiner's point: Uranium is non-renewable although nuclear electricity is low-carbon.

• CSS 2020 Q2(d) — Briefly explain Geothermal Energy and Hydro Electricity. (5 marks)

  Geothermal energy (approximately 2.5 marks): It is energy obtained from the Earth's internal heat, generated largely by primordial heat and radioactive decay. In suitable geothermal fields, steam or hot water is brought to the surface and used for a turbine-generator or direct heating. Merits: near-continuous output and low operational emissions. Limits: drilling expense, suitable geology and possible release of dissolved gases.

  Hydroelectricity (approximately 2.5 marks): Water at height possesses gravitational potential energy. Flow through a penstock rotates a turbine coupled to a generator.

  Conversion: Potential → kinetic → turbine mechanical energy → electrical energy.

  Formula: P = ηρgQH, where η is efficiency, ρ water density, g gravity, Q flow rate and H effective head.

  Pakistan example: Tarbela and Mangla dams.

  Merits: low operating emissions and flexible supply. Limits: ecological disturbance, resettlement, siltation and seasonal flow variation.

• CSS 2022 Q2(b) — Briefly explain wind energy, solar energy and biofuels. (5 marks)

  Wind energy: Uneven heating creates pressure differences and moving air. Wind turns turbine blades connected to a generator. Benefit: no fuel purchase. Limit: output varies with wind speed. Example: Jhimpir–Gharo, Sindh.

  Solar energy: Photovoltaic cells convert sunlight directly into DC electricity through the photovoltaic effect. Solar thermal collectors instead use sunshine for heat. Benefit: suitable for rooftop generation. Limit: generation falls at night and under heavy cloud. Example: Bahawalpur solar installations.

  Biofuels: Fuels derived from recently living organic materials. Bioethanol comes from fermentation, biodiesel from suitable oils and fats, and biogas from oxygen-free microbial digestion. Benefit: can turn agricultural waste into useful energy. Limit: unsustainable cultivation can compete with food production and land.

  Conclusion: These alternatives can diversify Pakistan's energy supply, but each requires suitable technology and management.

• CSS 2021 Q2(d) — What are the advantages and limitations of renewable energy resources? Briefly explain the prospects of non-conventional energy resources in Pakistan. (5 marks)

  Advantages (1.5 marks):

  • Naturally replenished, reducing dependence on finite fuels.
  • Generally lower lifecycle greenhouse gas emissions.
  • Solar and wind have low ongoing fuel costs; distributed systems can serve rural communities.

  Limitations (1.5 marks):

  • Wind and solar output varies with weather and daylight.
  • Upfront investment, transmission infrastructure and storage/flexible backup may be needed.
  • Hydropower and large-scale installations can affect land, rivers and wildlife.

  Prospects in Pakistan (2 marks):

  • Solar: strong irradiation across much of Pakistan; household, industrial and agricultural rooftop systems.
  • Wind: Gharo–Jhimpir corridor offers favourable conditions.
  • Biomass: sugarcane bagasse and livestock waste can support electricity and biogas.
  • Other potential: small hydropower and selected geothermal applications.

  Critical point: Non-conventional is not identical to renewable; large established hydropower is frequently classified as conventional.

  Conclusion: Prospects are substantial, provided grid upgrades, transparent regulation and affordable financing accompany expansion.

• CSS 2015 Q5(b) — How can the energy crisis be minimized in Pakistan? (5 marks)

  Introduction: Pakistan's energy crisis is not only a generation problem. Financial imbalances, inefficient distribution and dependence on costly fuels also affect supply and affordability.

  Measures:

  1. Diversify generation: develop appropriate solar, wind, hydropower and other reliable low-carbon resources to reduce fuel-import exposure.
  2. Reduce distribution losses: upgrade power lines and transformers, curb electricity theft and strengthen metering.
  3. Address circular debt: improve billing, targeted subsidies, timely payments and financial governance.
  4. Strengthen grids: expand transmission, storage and flexible generation to support variable renewable output.
  5. Manage demand: promote LEDs, efficient motors, building insulation and agricultural pumping efficiency.
  6. Improve planning: procure projects transparently and evaluate long-term capacity-payment obligations rather than adding generation indiscriminately.

  Pakistan examples: Bahawalpur solar, Sindh wind corridor and existing Tarbela hydropower.

  Conclusion: Lasting relief requires generation diversification and structural electricity-sector reform, not simply building more power stations.

• CSS 2017 Q4(D) — Most household appliances utilize ‘DC’, so why do we generate ‘AC’ at power stations? (5 marks)

  Introduction: Large power stations commonly produce alternating current (AC), while electronic devices such as phones and computers internally use direct current (DC). Many household appliances also operate directly on AC.

  Reasons:

  1. Voltage transformation: AC can be stepped up or down conveniently with transformers.
  2. Efficient transmission: For a given transferred power, a higher voltage permits lower current, which reduces resistive line loss according to P(loss) = I²R.
  3. Practical machinery: Alternators and many AC motors are robust and economical for large-scale generation and industry.
  4. Safe distribution: Voltage is stepped down at substations for consumer use.
  5. Conversion at home: Chargers and power supplies rectify AC to DC where electronics require it.

  Important qualification: Modern power electronics also allow efficient high-voltage DC transmission, particularly on selected long-distance links.

  Conclusion: AC remains widespread because voltage transformation and interconnected distribution are practical and economical.

• CSS 2018 Q3(B) — Define ‘Bio-Fuel’. How is it helpful to promote clean energy? (5 marks)

  Definition: A biofuel is a fuel made from relatively recent biological material, such as plants, agricultural residues, organic waste or animal manure, instead of ancient fossil deposits.

  Forms: Bioethanol from fermentation of sugars; biodiesel from plant oils or waste fats; biogas (methane-rich gas) from anaerobic digestion of organic waste.

  Contribution to cleaner energy:

  • Replaces part of petrol, diesel or fossil gas consumption.
  • Utilizes crop residue and animal waste, reducing uncontrolled decomposition and waste disposal.
  • Sustainable feedstocks may lower lifecycle greenhouse gas emissions.
  • Rural production can support farming livelihoods and improve local energy access.

  Limitations: Biofuels are not automatically carbon-neutral. Farming, fertilizer use, land conversion, processing and combustion all affect their carbon footprint. Some feedstocks compete with food crops or cause deforestation.

  Pakistan example: Biogas digesters using cattle dung, and bagasse-based energy in sugar mills.

  Conclusion: Biofuel is most beneficial when made from sustainable feedstocks, particularly waste.

• CSS 2023 Q4(c) — What is the biosphere? Write a note on the ‘Energy Resources’ available in the biosphere. (5 marks)

  Biosphere (1 mark): The biosphere is the part of Earth in which living organisms exist, interacting with the atmosphere, hydrosphere and lithosphere.

  Energy resources (3 marks):

  • Solar radiation: The main energy input driving photosynthesis, atmospheric circulation and much of the water cycle.
  • Biomass: Plants store chemical energy by photosynthesis; wood, agricultural residues and animal waste can supply heat, biofuels and biogas.
  • Wind and hydropower: Solar heating contributes to wind and evaporation; moving air and water can turn electrical generators.
  • Fossil fuels: Coal, oil and natural gas are ancient organic deposits formed over geological timescales, though they are extracted from the lithosphere rather than produced by the living biosphere today.
  • Other Earth resources: Geothermal heat and uranium are geological energy resources, not products of the biosphere.

  Environmental relevance (1 mark): Unsustainable fuel extraction and combustion contribute to habitat loss, pollution and climate change.

  Conclusion: The biosphere is closely linked to Earth's energy flows, with sunlight sustaining nearly all ecosystems.

• CSS 2025 Q3(d) — Differentiate between biomass and biogas. Briefly explain methods of obtaining energy from biomass. (5 marks)

  Difference (2 marks):

  Feature	Biomass	Biogas
  Meaning	Organic feedstock such as crop residues, wood and manure	Methane-rich gaseous fuel made by digestion of biomass
  Nature	Feedstock; may be solid, liquid or wet organic waste	Gas mixture, chiefly methane and carbon dioxide
  Relationship	Starting material	One possible product of biomass conversion

  Energy extraction methods (3 marks):

  1. Direct combustion: Burn dry biomass to obtain heat or raise steam for electricity.
  2. Anaerobic digestion: Microbes decompose manure or organic waste without oxygen, producing biogas.
  3. Fermentation: Microorganisms convert suitable sugars into ethanol fuel.
  4. Gasification / pyrolysis: Heat biomass under restricted or absent oxygen to produce combustible gas, oils or char.
  5. Oil conversion: Process vegetable oils or waste fats into biodiesel by transesterification.

  Pakistan example: Bagasse for sugar-mill cogeneration and cattle manure for rural biogas.

  Conclusion: Biomass is the raw energy material; biogas is one renewable fuel produced from it.

• CSS 2015 Q4(b), 2019 Q4(b) — Biotechnology in Pakistan: current status, future prospects and brief account. (5 marks)

  Definition (1 mark): Biotechnology uses living organisms, cells or biological processes to develop useful products, such as vaccines, insulin, disease-resistant plants and biofuels.

  Main approaches (1 mark): Genetic engineering modifies genetic material; bioprocess engineering uses controlled cell or microorganism cultures to manufacture products.

  Pakistan's position (1.5 marks):

  • Agriculture: Bt cotton and tissue-culture techniques.
  • Research: National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, and university laboratories.
  • Healthcare: Research and manufacturing capacity in diagnostics, vaccines and biological products, although import dependence and funding constraints remain.

  Future prospects (1 mark): Climate-resilient crops, improved seed varieties, affordable diagnostics, locally produced biologics and waste-to-energy biotechnology.

  Challenges (0.5 mark): Funding limitations, biosafety regulation, infrastructure gaps and skilled-workforce needs.

  Conclusion: Responsible investment in research, biosafety and industry collaboration can expand biotechnology's contribution to national development.

  Relevance note: This is a linked biotechnology past-paper question, not a renewable-energy question.

15. Extra Practice MCQs (exam-style, not official)

ℹ️

These are exam-style practice questions written by me, not copied from FPSC papers. The official past-paper MCQs are in the section above.

1. Which of the following is a non-renewable source of energy? (a) Wind (b) Solar (c) Uranium (d) Biomass
2. Power stations generate AC mainly because: (a) AC is cheaper to store (b) AC can be easily stepped up/down with transformers (c) DC cannot flow in wires (d) AC has no resistance
3. A photovoltaic cell converts: (a) Heat into sound (b) Sunlight into electricity (c) Wind into heat (d) Water into steam
4. The process by which an LED produces light is called: (a) Fluorescence (b) Electroluminescence (c) Incandescence (d) Combustion
5. An LED is: (a) A renewable energy source (b) A solid-state lighting device (c) A type of battery (d) A fuel
6. Geothermal energy comes from: (a) The Sun (b) Heat inside the Earth (c) Tides (d) Wind
7. The source of the Sun's energy is: (a) Chemical burning (b) Nuclear fission (c) Nuclear fusion (d) Gravity only
8. 1 kilowatt-hour is equal to: (a) 3.6 × 10⁶ joules (b) 3.6 × 10³ joules (c) 1 × 10⁶ joules (d) 360 joules
9. Biomass is considered roughly carbon-neutral because: (a) It releases no CO₂ (b) The CO₂ released is offset by what the plants absorbed while growing (c) It is made of carbon only (d) It is burned underground
10. Pakistan's six operating nuclear power plants have a combined capacity of about: (a) 1,200 MW (b) 3,530 MW (c) 8,000 MW (d) 49,651 MW
11. Chashma-5 uses which reactor design? (a) CANDU (b) Hualong One (c) AP1000 (d) VVER
12. The SI unit of power is the: (a) joule (b) watt (c) newton (d) volt
13. Which coal has the highest carbon content? (a) Peat (b) Lignite (c) Bituminous (d) Anthracite
14. Nuclear power plants today use: (a) fusion (b) fission (c) combustion (d) fermentation
15. Pakistan's Thar coal is mainly: (a) peat (b) lignite (c) bituminous (d) anthracite
16. A hydropower scheme that works like a giant battery by pumping water uphill is: (a) run-of-river (b) pumped storage (c) tidal barrage (d) geothermal
17. A solar system connected to the grid that can sell surplus power is: (a) off-grid (b) on-grid (grid-tied) (c) passive solar (d) solar thermal

• ✅ Answer key
  1. (c) Uranium (nuclear is non-renewable)
  2. (b) Easily stepped up/down with transformers
  3. (b) Sunlight into electricity
  4. (b) Electroluminescence
  5. (b) A solid-state lighting device (not an energy source)
  6. (b) Heat inside the Earth
  7. (c) Nuclear fusion (hydrogen → helium)
  8. (a) 3.6 × 10⁶ J (3.6 MJ)
  9. (b) CO₂ released is offset by photosynthesis
  10. (b) ≈ 3,530 MW (4,730 MW after Chashma-5)
  11. (b) Hualong One (HPR1000)
  12. (b) watt (1 joule per second)
  13. (d) Anthracite (order: peat, lignite, bituminous, anthracite)
  14. (b) fission (fusion is still experimental)
  15. (b) lignite
  16. (b) pumped storage
  17. (b) on-grid, using net metering

16. Extra Practice Long Questions (20 Marks)

ℹ️

Extra practice questions built from the syllabus and your self-test list. The official past-paper questions with answers are in the section above.

1. Most household appliances use DC, so why do we generate AC at power stations?
2. What is the mechanism of an LED, and what are its uses that make it a choice in the modern age?
3. What are the different ways to get benefits from solar energy?
4. What do you know about wind energy and its harnessing? Describe a wind farm
5. What are the different forms in which energy exists, and how can energy be conserved?
6. Discuss Pakistan's energy mix and how the country can shift to renewables
7. Classify energy sources into renewable and non-renewable, with their types and examples from Pakistan

• 📝 Answer outlines
  1. Transformers step voltage up/down → high-voltage transmission cuts I²R loss → cheaper alternators and simpler AC motors → rectifier converts to DC inside appliances
  2. Semiconductor diode, forward-biased → electron-hole recombination at the p-n junction → photons (electroluminescence) → advantages list → uses
  3. Table: PV, solar thermal, CSP, passive design, solar devices → benefits (bills, emissions, off-grid, low maintenance)
  4. How harnessed (blades → rotor → generator) → wind farm definition → siting → advantages and limitations
  5. Table of eight forms → law of conservation of energy → conservation methods
  6. Global picture (renewables overtook coal, 2025) → Pakistan data (53.1% clean, nuclear 3,530 MW, Chashma-5, Diamer-Bhasha, solar boom) → challenges (grid, storage, cost) → way forward
  7. Definitions (energy, power, primary, secondary) → table of four classifications (renewability, conventional/non-conventional, primary/secondary, commercial/non-commercial) → non-renewable types (coal ranks, oil, gas forms, fission vs fusion) → renewable types (solar, wind, hydro types, biomass, geothermal, ocean) → Pakistan examples → advantages and limits

17. Book Questions: Added Answers

📖

Answers for the book's contents-list questions (Part A, I.d) that were missing or thin on this page. Each answer starts with a written outline, then headings and bullets.

• Book p.34: How do renewable energy resources replace conventional fuels? (5)

📝

**Outline:** what conventional fuels are → how renewables replace them, sector by sector (table) → what makes replacement possible → limits → Pakistan → conclusion

### 1. Conventional fuels

- **Conventional fuels** are the fossil fuels: coal, petroleum (oil) and natural gas
- They are finite and release carbon dioxide and other pollutants
- Renewables (sun, wind, water, biomass, Earth's heat) are replenished naturally

### 2. How renewables replace them

| Sector | Fossil fuel used now | Renewable replacement |
| --- | --- | --- |
| **Electricity** | Coal, gas and oil power plants | Solar panels, wind farms, hydropower, geothermal and biomass plants |
| **Transport** | Petrol and diesel | Biofuels (ethanol, biodiesel), electric vehicles charged with clean power, hydrogen |
| **Heating and cooking** | Gas, LPG, firewood | Solar water heaters, biogas, efficient biomass stoves |
| **Farming and pumping** | Diesel pumps | Solar tube wells (in Pakistan, farm use of grid power fell 42.3% in July–March FY26) |
| **Remote areas** | Diesel generators | Off-grid solar and mini-hydro |

### 3. What makes replacement possible

- Solar and wind costs have fallen sharply
- Batteries and other storage cover the night and calm days
- Grid upgrades and smart grids carry variable power
- Net metering lets homes sell extra power to the grid
- Government incentives, targets and carbon pricing

### 4. Limits and challenges

- Sun and wind are **intermittent**
- Storage and grids need big investment
- High up-front cost
- Land and material needs
- Replacement is gradual, so fossil fuels stay in the mix for some time

### 5. Benefits of replacing fossil fuels

- Lower carbon emissions and cleaner air
- Energy security and a smaller fuel import bill
- Stable, almost free fuel after set-up
- New local jobs

### 6. Pakistan

- Hydel, nuclear and renewables supplied 53.1% of generation in July–March FY26
- Rooftop and off-grid solar has boomed because of high tariffs and cheap panels
- Diamer-Bhasha (4,500 MW) and wind in Sindh add clean power
- Imported fuel and the grid's weakness still hold back the shift

### 7. Conclusion

- Renewables can replace fossil fuels step by step, led first by electricity, then transport and heating

💡

**In simple words:** instead of burning coal, oil and gas, we collect energy from the sun, wind and water. It works best for electricity first, and storage and good grids decide how fast the rest can follow.

• Book p.33: Write a brief note on non-renewable energy conservation and its sustainable use. (5)

📝

**Outline:** what non-renewables are → why conserve them → ways to conserve → sustainable use → Pakistan

### 1. Non-renewable energy

- **Non-renewable sources** are fossil fuels (coal, oil, natural gas) and nuclear fuel (uranium)
- They take millions of years to form, or are limited, so once used they are gone for a very long time

### 2. Why conserve them

- Reserves are finite
- Burning fossil fuels causes air pollution and climate change
- Imported fuel drains foreign exchange
- Future generations need them too

### 3. Ways to conserve

- **Use less**: switch off unused devices and avoid waste
- **Use efficiently**: efficient engines, appliances, industry and LED lighting
- **Insulate** buildings to cut heating and cooling
- **Public transport**, carpooling and well-maintained vehicles
- **Cogeneration**: capture waste heat from power plants and factories
- **Cut losses**: fix leaks, theft and transmission losses
- **Recycle** materials, which needs less energy than making them from raw material
- **Better recovery**: modern extraction wastes less fuel

### 4. Sustainable use

- **Sustainable use** means meeting today's energy needs without harming future generations' ability to meet theirs
- Use fossil fuels carefully as a **bridge** while renewables grow
- Keep a **balanced energy mix**
- Use cleaner technology (efficient coal plants, carbon capture, natural gas instead of coal)
- Recycle and reprocess nuclear fuel to cut waste
- Reform subsidies and use pricing that rewards saving
- Invest in research and in renewable alternatives
- Run public awareness campaigns

### 5. Pakistan

- ENERCON (National Energy Conservation Centre) promotes efficient use of energy
- Priorities: efficient appliances, fewer line losses, careful use of Thar coal and limited natural gas, and faster growth of clean power

💡

**In simple words:** coal, oil and gas are like savings in a bank that nobody refills. We should spend them slowly and wisely while we build new income from the sun, wind and water.

18. CSS Exam Perspective

🎯

• Most repeated areas: renewable vs non-renewable, LED mechanism, AC vs DC, solar and wind harnessing, forms and conservation of energy
• Newer likely areas: Pakistan's energy mix (solar boom, nuclear, Chashma-5, Diamer-Bhasha) and the global shift from coal to renewables
• Short-question style: "Why…", "What do you know about…", "How can… be conserved?"
• Tip: for essay-type answers, open with the global picture, then add Pakistan's figures as a closing paragraph