Conventional Energy Technology: Thermal, Oil, Gas and Hydro

Prerequisites

• Electricity and Magnetism: how a generator turns rotation into current, and why power is sent at high voltage.
• Conventional Energy (Geography): where India’s coalfields, oilfields, dams and power plants are. This page explains how they work; that page says where they are.
• Power Generation in Chhattisgarh: Korba, Sipat, Lara and Hasdeo Bango, the state examples used below.

The Hook: What Happens Inside Sipat?

Why it matters: Prelims asks the science behind everyday energy: which gas is in LPG, CNG vs LNG, octane vs cetane, which turbine suits which head, what FGD or an ESP removes. Mains GS-II (Paper IV) asks short notes on clean-coal technology, coal gasification and the energy transition.

Energy Basics You Need First

How a Coal-fired Thermal Power Plant Works

A thermal power station (ताप विद्युत गृह) runs on the Rankine cycle: water is boiled into high-pressure steam, the steam spins a turbine, and the used steam is condensed back into water and pumped round again.

graph LR
    A["Coal
(chemical energy)"] --> B["Boiler / furnace
(heat energy)"]
    B --> C["High-pressure steam"]
    C --> D["Steam turbine
(mechanical energy)"]
    D --> E["Generator
(electrical energy)"]
    E --> F["Step-up transformer
to the grid"]
    D --> G["Condenser
steam back to water"]
    G --> H["Cooling tower
or river water"]
    G --> I["Feed pump"]
    I --> B

Subcritical, supercritical and ultra-supercritical

Water has a critical point at about 374 °C and 22.1 MPa (roughly 218 times atmospheric pressure). Above it, water does not “boil” in the normal sense: liquid and steam become a single phase.

Why it matters: each percentage point of efficiency means less coal burnt per kWh, so less CO₂, ash and SO₂ for the same electricity.

Coal: what kind burns in Indian plants?

Coal is ranked by how much carbon it holds and how much moisture and volatile matter it has lost over geological time.

• Most Indian thermal coal is non-coking, Gondwana coal with high ash (often around 30–45%) but low sulphur. High ash is why Indian plants need efficient ESPs and generate huge volumes of fly ash.
• Coal washing (beneficiation) removes some ash before burning, which also cuts transport of useless rock.

Clean-coal technologies

Petroleum: From Crude to Fuel

Crude oil (पेट्रोलियम, “rock oil”) formed from the remains of tiny marine organisms buried in sedimentary rocks and cooked by heat and pressure over millions of years. It collects in porous rock under an impermeable cap, often in an anticline (dome-shaped fold).

Fractional distillation in a refinery

Crude is a mixture of hydrocarbons. It is heated and fed into a tall fractionating column: lighter fractions with lower boiling points rise to the top, heavier ones stay near the bottom.

Cracking breaks heavy, long-chain molecules into lighter, more valuable ones such as petrol.

Fuel quality terms

Natural Gas: CNG, LNG, LPG and PNG

Natural gas is mainly methane (CH₄). It burns more cleanly than coal or oil, emitting roughly half the CO₂ of coal per unit of electricity and very little SO₂ or particulates. This is why it is called a “bridge fuel” for the transition.

Unconventional gas:

• Shale gas: methane locked in tight shale rock, released by horizontal drilling + hydraulic fracturing (“fracking”), which needs large volumes of water and can contaminate groundwater.
• Gas hydrates: methane trapped in ice-like crystals under the seabed and permafrost. India’s offshore basins are believed to hold large deposits, but there is no commercial production.

Hydropower: Falling Water

A hydroelectric plant (जलविद्युत) converts the potential energy of water stored at a height into kinetic energy, which spins a turbine connected to a generator.

Here \(\rho\) is the density of water, \(g\) is gravitational acceleration, \(Q\) is the flow rate, \(H\) is the head (height of fall) and \(\eta\) is efficiency. Power rises with both head and flow. Hydro turbines are very efficient, often around 90%.

• India’s hydro capacity (large and small) was about 57 GW in July 2026. Since March 2019, large hydro (above 25 MW) is also counted as renewable energy.
• Chhattisgarh: the Hasdeo Bango (Minimata Bango) station in Korba, 120 MW (3 × 40 MW), is the state’s largest hydel plant.
• Concerns: displacement, submergence of forests, siltation, methane from rotting vegetation in tropical reservoirs, and seismic risk in the Himalaya.

Analysis for Mains: Why Conventional Energy Still Dominates

1. Base load and reliability: coal, gas and large hydro can be dispatched on demand; solar and wind cannot (yet) without storage.
2. Domestic coal security: India imports about 89% of its crude oil (2025-26) but mines most of its own coal, so coal is the most “self-reliant” fossil fuel.
3. Costs of coal: air pollution (PM, SO₂, NOx), fly ash, mercury, water use, land loss in mining districts such as Korba, and CO₂ emissions.
4. The middle path: higher efficiency (supercritical and USC units), FGD retrofits, fly ash use, gasification for chemicals, and retiring old inefficient units while renewables and storage grow.
5. Just transition (न्यायसंगत संक्रमण): districts like Korba depend on coal for jobs and revenue (DMF funds). Any phase-down needs reskilling and new industries.

Memory Tricks

Don’t Confuse

Common Mistakes

Practice

All questions below are original practice questions written in CGPSC style. They are not previous-year questions.

Level 1: Foundation

1. One unit of electricity on a bill equals one ________.
2. In a thermal power plant, the device that removes fly ash from flue gas is the ________.
3. The main constituent of CNG is ________, while LPG is mainly ________ and ________.

Level 2: Prelims MCQs

Q1. Consider the following statements about supercritical thermal power technology:

1. In a supercritical boiler, water is heated above its critical point, so there is no separate boiling stage.
2. Supercritical units are less efficient than subcritical units but cheaper to build.
3. NTPC’s Sipat station in Chhattisgarh uses supercritical units in its Stage-I.

Which of the statements given above is/are correct?

• (a) 1 only
• (b) 1 and 3 only
• (c) 2 and 3 only
• (d) 1, 2 and 3

Q2. Match List I (Turbine) with List II (Most suitable condition):

• (a) A-2, B-3, C-1, D-4
• (b) A-3, B-2, C-1, D-4
• (c) A-2, B-1, C-3, D-4
• (d) A-1, B-3, C-2, D-4

Q3. Which one of the following correctly describes LNG?

• (a) Propane and butane liquefied under pressure for household cylinders
• (b) Methane cooled to about −162 °C so that it occupies a much smaller volume for transport
• (c) Methane compressed to about 200 bar for use in buses
• (d) Gas obtained by gasifying coal, mainly carbon monoxide and hydrogen

Q4. In the fractional distillation of crude oil, which of the following fractions is collected nearest the top of the column?

• (a) Diesel
• (b) Kerosene
• (c) Petrol
• (d) Lubricating oil

Q5. Flue-gas desulphurisation (FGD) units in coal power plants commonly produce which useful by-product?

• (a) Fly ash
• (b) Gypsum
• (c) Ammonia
• (d) Syngas

Level 3: Mains Answer Writing

Q1. (60 words) What is coal gasification? Why is it important for a coal-rich state like Chhattisgarh?

Q2. (150–200 words) “Clean coal is not an oxymoron but a bridge.” Examine the technologies that can reduce the environmental impact of coal-based power in India.

Quick Revision Table

Key Takeaways

What’s Next

• Renewable Energy Technology: how solar cells, wind turbines and biogas plants work
• Energy Storage and Hydrogen: pumped storage, batteries and green hydrogen
• Nuclear Energy: reactors and India’s three-stage programme
• Environmental Pollution and Waste Management: the air and ash problems of fossil fuels