UPSC CSE Prelims
Energy Technology Previous Year Questions (PYQs)

Detailed Explanation:

Statement 1 — Incorrect. This describes Blue Hydrogen, NOT Green Hydrogen. Blue Hydrogen comes from natural gas + carbon capture (CCS). Green Hydrogen uses a completely different method (see Statement 2).

Statement 2 — Correct. Green Hydrogen = splitting water (electrolysis) using electricity from renewable sources (solar/wind). It's a zero-emission process.

Statement 3 — Correct. India's National Green Hydrogen Mission targets:

• 5 MMT/year production capacity by 2030
• This leads to ~50 MMT reduction in greenhouse gas emissions annually
• Plus reduces fossil fuel imports and creates 6 lakh+ jobs

Memory Trick: Color-code hydrogen by source:

• Green = Renewable electricity + water (clean)
• Blue = Natural gas + carbon capture (cleaner fossil)
• Grey = Natural gas, no carbon capture (dirty)

Detailed Explanation:

Alternative powertrain vehicles are vehicles that do not rely on conventional petrol or diesel internal combustion engines as their primary source of propulsion.

• Statement I is Correct: Battery Electric Vehicles (BEVs) run entirely on electricity stored in batteries.

• Statement II is Correct: Hydrogen Fuel Cell Vehicles (FCEVs) generate electricity from hydrogen using fuel cells.

• Statement III is Correct: Fuel Cell Electric Hybrid Vehicles (FCEHVs) combine fuel cells, batteries, and electric motors.

• Therefore, all three are considered alternative powertrain vehicles, making Option C the correct answer.

Vehicle-wise Analysis

Alternative Powertrain Vehicles

What are Alternative Powertrains?

These are vehicle propulsion systems that use alternatives to conventional petrol or diesel engines.

Major Types

Important Facts

• BEVs produce zero tailpipe emissions.

• FCEVs emit only water vapor as a by-product.

• Hydrogen-based vehicles are considered important for long-range and heavy-duty transport.

• Alternative powertrains help reduce dependence on fossil fuels and lower carbon emissions.

Detailed Explanation:

Coal gasification converts coal into syngas (mainly carbon monoxide and hydrogen), which serves as a raw material for many chemicals.

• I. Ethanol ✅ Correct – Syngas can be converted into ethanol through chemical or biological processes.

• II. Nitroglycerine ❌ Incorrect – Nitroglycerine is produced by nitrating glycerol, not from syngas obtained through coal gasification.

• III. Urea ✅ Correct – Hydrogen from syngas is used to make ammonia, which then reacts with carbon dioxide to produce urea.

• Therefore, only Ethanol and Urea can be produced using coal gasification technology, making Option B the correct answer.

Substance-wise Analysis

 Coal Gasification

What is Coal Gasification?

Coal gasification is the process of converting coal into syngas, a mixture of:

• Carbon Monoxide (CO)

• Hydrogen (H₂)

• Carbon Dioxide (CO₂)

• Water Vapour

Major Products from Syngas

• Ammonia

• Urea

• Methanol

• Ethanol

• Synthetic Natural Gas (SNG)

• Hydrogen

Important Facts

• Coal gasification helps reduce dependence on imported natural gas and crude oil.

• It is an important technology for producing fertilizers and industrial chemicals.

• India is promoting coal gasification to utilize its large domestic coal reserves.

Detailed Explanation:

In most Lithium-ion Electric Vehicle (EV) batteries, the cathode is made using combinations of Lithium, Cobalt, and Nickel.

• Statement I (Cobalt) ✅ Correct – Used in cathodes such as NMC and LCO batteries.

• Statement II (Graphite) ❌ Incorrect – Graphite is generally used in the anode, not the cathode.

• Statement III (Lithium) ✅ Correct – A key component of all lithium-ion battery cathodes.

• Statement IV (Nickel) ✅ Correct – Commonly used in NMC and NCA cathode chemistries.

• Therefore, only three elements (Cobalt, Lithium, and Nickel) usually make up battery cathodes, making Option C the correct answer.

Element-wise Analysis

EV Battery Components

Common Cathode Chemistries

• LCO – Lithium Cobalt Oxide

• NMC – Nickel Manganese Cobalt

• NCA – Nickel Cobalt Aluminum

• LFP – Lithium Iron Phosphate

Important Facts

• Cathode materials largely determine a battery's energy density and cost.

• Graphite remains the most widely used anode material in EV batteries.

• Demand for Lithium, Nickel, and Cobalt has increased significantly due to the global EV transition.

Detailed Explanation:

Correct Answer: ✅ Water Vapour (Option D)

Fuel Cell Electric Vehicles (FCEVs) use hydrogen as fuel. Inside the fuel cell, hydrogen reacts with oxygen from the air to generate electricity that powers the vehicle.

The by-products of this reaction are water (H₂O) and heat. Therefore, the only exhaust emission released from the vehicle's tailpipe is water vapour, making FCEVs a clean-energy transportation technology.

❌ Hydrogen Peroxide: Not produced as a normal exhaust product in fuel cells.

❌ Hydronium (H₃O⁺): Exists in aqueous solutions and is not emitted from vehicles.

❌ Oxygen: Oxygen is consumed in the reaction, not emitted.

✅ Water Vapour: The primary and only exhaust emission from hydrogen fuel cell vehicles.

Short Notes: Fuel Cell Electric Vehicles (FCEVs)

• FCEVs use hydrogen (H₂) as fuel to generate electricity.

• Electricity is produced through an electrochemical reaction, not combustion.

• Main reaction: Hydrogen + Oxygen → Electricity + Water + Heat.

• The exhaust emission is only water vapour (H₂O).

• Fuel cells are considered zero tailpipe emission technology.

• Hydrogen is stored in high-pressure tanks inside the vehicle.

• Examples include the Toyota Mirai and Hyundai Nexo.

• FCEVs offer fast refuelling and longer driving ranges compared to many battery EVs.

Detailed Explanation:

Correct Answer: ✅ Option 4 (All Four)

Distributed Energy Resources (DERs) are small-scale energy generation, storage, or management systems located close to consumers rather than large centralized power plants. They help improve grid reliability, energy efficiency, and renewable energy integration.

✅ Battery Storage – Correct: Stores electricity locally and supplies power when needed, making it a key DER.

✅ Biomass Generators – Correct: Small-scale biomass-based power plants can generate electricity near consumption points.

✅ Fuel Cells – Correct: Fuel cells produce electricity in a decentralized manner and are widely recognized as DERs.

✅ Rooftop Solar Photovoltaic Units – Correct: One of the most common DERs, generating electricity directly at homes, offices, and industries.

Short Notes: Distributed Energy Resources (DERs)

• DERs are small-scale energy resources located near end-users.

• Include both energy generation and energy storage technologies.

• Common examples: rooftop solar, battery storage, fuel cells, biomass plants.

• Reduce transmission and distribution losses.

• Improve grid resilience and reliability.

• Support integration of renewable energy sources.

• Can operate independently or alongside the main grid.

• Important for the development of smart grids and decentralized energy systems.

Detailed Explanation:

Answer: Option 3 — Statement-I is correct but Statement-II is incorrect

India indeed has domestic uranium deposits but relies heavily on coal for electricity generation (around 70% of total capacity). However, Statement-II is factually wrong because commercial nuclear power plants do not require uranium enriched to 60%.

✅ Statement-I – Correct: India has uranium deposits in Jharkhand (Singhbhum), Andhra Pradesh (Tummalapalle), and other regions, yet coal remains the dominant source for electricity production due to its abundance, lower cost, and established infrastructure.

❌ Statement-II – Incorrect: Uranium enriched to 60% or more is classified as Highly Enriched Uranium (HEU) and is used for research reactors or nuclear weapons, not commercial electricity production. India's PHWRs use natural uranium (0.7% U-235), while most commercial Light Water Reactors worldwide use Low Enriched Uranium (LEU) enriched to only 3-5% U-235.

📝 Short Notes: Nuclear Fuel Enrichment Levels

• India's Nuclear Program: Uses indigenous three-stage program starting with natural uranium in PHWRs
• Coal Dominance: India's coal reserves (4th largest globally) and lower capital costs make it preferred despite environmental concerns
• Uranium Sources: Jharkhand (Jaduguda), Andhra Pradesh (Tummalapalle - one of world's largest), Meghalaya, Rajasthan
• Nuclear Capacity: Only ~3% of India's total electricity comes from nuclear power (as of 2023)

Detailed Explanation:

Answer: Option 4 — None

All three statements regarding coal-based thermal power plants in India are incorrect. Some plants use seawater for cooling (like Mundra), many are located in water-stressed districts, and a significant number are privately owned.

❌ Statement 1 – Incorrect: The Mundra Thermal Power Plant uses seawater from the Gulf of Kutch in a closed-cycle cooling system, and also employs purified seawater from reverse osmosis plants for auxiliary systems.

❌ Statement 2 – Incorrect: According to WRI research, 40% of India's thermal power plants are situated in water-stressed regions, with 14 out of 20 largest thermal utilities experiencing shutdowns between 2013-2016 due to water shortages.

❌ Statement 3 – Incorrect: Out of India's 269 thermal power plants, 138 are publicly owned while 131 are privately owned, demonstrating significant private sector participation.

📝 Short Notes: Coal-Based Thermal Power Plants in India

• Cooling Water Sources: While most plants use freshwater from rivers or reservoirs, coastal plants like Mundra (Gujarat) utilize seawater cooling systems to conserve freshwater resources.
• Water Stress Challenge: 40% of thermal plants are in water-stressed regions, leading to operational disruptions and forced shutdowns during water scarcity periods.
• Ownership Structure: Total 269 plants - 138 public sector (Central/State utilities like NTPC, State Gencos) and 131 private sector (Adani Power, Tata Power, Reliance Power, etc.).
• Capacity Distribution: Thermal power contributes approximately 50-55% of India's total installed electricity generation capacity.
• Environmental Concerns: High water consumption (3-5 liters per kWh), thermal pollution, and emissions make water management critical for sustainability.

Detailed Explanation:

Answer: Option 3 — 1 and 3

This question compares traditional sodium lamps with modern LED lamps used in street lighting. Statement 1 correctly identifies that sodium lamps emit light omnidirectionally (360 degrees), while LEDs are directional, reducing light wastage. Statement 3 correctly notes that sodium lamps produce nearly monochromatic yellow light, whereas LEDs offer better color rendering and spectrum diversity.

✅ Statement 1 – Correct: Sodium lamps emit light in all directions (360 degrees), while LED lamps are directional and focus light where needed, improving efficiency.
❌ Statement 2 – Incorrect: LED lamps have a significantly longer lifespan (50,000-100,000 hours) compared to sodium lamps (15,000-24,000 hours).
✅ Statement 3 – Correct: Sodium lamps produce monochromatic yellow-orange light (narrow spectrum), while LED lamps offer a broad spectrum with better color rendering index (CRI) for street lighting.

📝 Short Notes: Street Lighting Technologies

Detailed Explanation:

Answer: Option 2 — Some use imported uranium and others use domestic supplies

India's nuclear reactors are divided into civilian and strategic facilities under the 2005 Indo-US Civil Nuclear Deal. Reactors using imported uranium are placed under IAEA safeguards to ensure peaceful use, as mandated by international agreements for nuclear fuel supply. Reactors using domestic uranium remain outside IAEA safeguards, allowing India to maintain its strategic nuclear weapons program independently.

📝 Short Notes: India's Nuclear Programme and IAEA Safeguards

• Indo-US Civil Nuclear Deal (2008): Separated India's nuclear facilities into civilian (under IAEA safeguards) and military (outside safeguards) categories, ending India's nuclear isolation despite not signing the NPT.
• IAEA Safeguards: International inspection regime to verify that nuclear materials are used only for peaceful purposes and not diverted to weapons programs.
• Separation Plan: India voluntarily placed 14 of its 22 power reactors under IAEA safeguards, while keeping 8 reactors and other facilities outside for strategic purposes.
• Imported Uranium Condition: Any reactor using imported uranium or fuel must be under IAEA safeguards as per bilateral agreements with supplier countries (USA, Russia, France, etc.).
• Domestic Uranium: Reactors using indigenous uranium from Indian mines (Jharkhand, Andhra Pradesh) remain outside safeguards, preserving India's three-stage nuclear program and weapons capability.
• Three-Stage Programme: India's unique nuclear strategy using natural uranium (Stage I), plutonium breeder reactors (Stage II), and thorium-U233 cycle (Stage III) to achieve energy security.
• Strategic Autonomy: The separation allows India to maintain its minimum credible nuclear deterrent while accessing international nuclear commerce and technology.

Detailed Explanation:

Answer: Option 2 — 2 and 3 only

❌ Statement 1 – Incorrect: Algae-based biofuel production is not restricted to seas. Algae can be cultivated on land using open ponds, closed photobioreactors, or wastewater treatment systems. Continental production is technically feasible and widely practiced.

✅ Statement 2 – Correct: Setting up algae biofuel facilities requires advanced biotechnology, sophisticated engineering for photobioreactors, precise cultivation control systems, and extraction technology. This high-tech infrastructure poses significant challenges for developing countries with limited technical expertise and capital.

✅ Statement 3 – Correct: Large-scale algae cultivation facilities need extensive land/water resources, significant energy inputs, and water usage. These requirements can trigger ecological concerns (biodiversity impact, water depletion) and social issues (land acquisition, displacement of communities, competition with food production).