At a Glance
Four facts to hold on to.
Core loop
Coal, boiler, steam, turbine, generator.
Big need
Cooling water for the condenser.
Waste streams
Flue gas and ash.
UPSC 2023
All three “none” claims are false.
In this lesson
How the Plant Works
Follow coal to electricity
- Coal arrives and is crushed or ground.
- A boiler burns it with air.
- Heat turns treated water into steam.
- Steam spins a turbine and generator.
- A condenser cools used steam back into water.
- Pumps return the water to the boiler. The steam loop repeats.
- Cooling water removes waste heat from the condenser.
- Coal also leaves ash and flue gas. Each needs separate controls.
Inputs and risks
| Input | Main job | Output or risk |
|---|---|---|
| Coal and air | Provide heat | Electricity, gas and ash |
| Boiler water | Carry heat as steam | Needs cleaning and reuse |
| Cooling water | Remove waste heat | Warm return or evaporation |
- India has central, state and private coal stations.
- The CEA’s monthly table lists private coal capacity. Source: CEA executive summary, September 2025.
- A taller chimney spreads gas. It does not remove pollutants.
True or False: NTPC names seawater as the source for the cooling-water system at its Simhadri plant.
Water, Air and Ash
Withdrawal is not consumption
- Withdrawal is water taken from a river, reservoir or sea.
- Consumption is the part not soon returned to that source.
- A once-through system takes much water and returns most of it warmer.
- A cooling tower recirculates water but loses some by evaporation.
- An air-cooled condenser needs far less water. It costs more and works worse in hot weather.
- A coastal plant may use seawater. Intake and warm discharge still need controls.
Pollutants and controls
| Pollutant | Source | Main control |
|---|---|---|
| Fine particles | Ash and dust | Electrostatic precipitator or fabric filter |
| Sulphur dioxide | Sulphur in coal | Flue-gas desulphurisation, where required |
| Nitrogen oxides | High-temperature burning | Low-NOx burners |
| Carbon dioxide | Carbon in coal | Burn less coal, or replace its power |
- A filter does not remove carbon dioxide.
- A device helps only when installed and run well.
- Fine particles can enter the lungs. Source: WHO on air pollution and health.
Fly ash and bottom ash
- Fly ash rides in the exhaust. Filters collect much of it.
- Bottom ash is heavier. It falls near the boiler.
- Ash can go into cement, bricks and roads when standards allow.
- Poor handling spreads dust or contaminates water.
- India’s ash-use rules require staged use of current ash. Source: Environment Ministry, Fly Ash Mission minutes.
- See also Fly Ash.
True or False: A coal plant can run safely without cooling water if it has enough coal.
True or False: Water withdrawal and water consumption mean exactly the same thing.
Water Stress, Rules and Transition
When water stops power
- A 2018 WRI study found high water stress at about 40% of plants in its dataset. This is a dated estimate, not a 2026 count. Source: WRI, Parched Power.
- Its 2030 figure is a projection, not a measurement.
- Parli Thermal Power Station in Maharashtra lost its water supply when drought cut the Majalgaon dam.
- WRI reported 226 days of no generation there, from July 2015 to December 2016.
- WRI also estimated about US$1.4 billion in lost revenue across 14 major thermal utilities during 2013–2016 shutdowns. Source: WRI, Parli case study.
- Fuel alone cannot keep the steam cycle running.
Who regulates?
- The Environment Ministry sets national rules under the Environment (Protection) Act.
- The Central Pollution Control Board coordinates pollution control.
- State boards issue and enforce many local permissions.
- The CEA collects power data and technical information.
- A 2025 amendment changed how sulphur-dioxide limits apply across plant categories. Source: PIB, 2025 emissions update.
- Older deadline tables may be out of date.
Coal in the energy transition
- Coal plants give scheduled power when demand rises and sunlight falls.
- Solar, wind, storage and hydro can replace some of it over time.
- Some units are asked to change output as renewables vary. Repeated ramping adds wear and cost. Source: CEA flexible-operation report.
- Flexible is not the same as clean.
- See Power Resources: Conventional and Non-Conventional.
Think it through: why could a coal station stop with full coal stores?
The condenser still has to release heat. In a drought, cooling water may run short. The plant can lose generation even with fuel in hand. Parli showed this in 2015–2016.
True or False: WRI reported 226 days of zero generation at Parli during 2015–2016 because of a water shortage.
True or False: WRI’s 2018 estimate of about 40% high water stress is a current official 2026 plant count.
Previous Year Questions
UPSC 2023 gave three claims, each starting with “none”.
- UPSC 2023Statements: (1) none uses seawater, (2) none is in a water-stressed district, (3) none is privately owned. Zero statements are correct. View the question.
- Why each failsSimhadri uses seawater. The dated WRI study found plants in water-stressed areas. CEA records private coal capacity. One counterexample defeats a “none” claim.
True or False: The 2023 exam statement “None is privately owned” is correct.
Quick Q&A
Core loop?
Boiler, steam, turbine, generator.
Cooling water job?
Condenses steam, removes heat.
Seawater example?
NTPC Simhadri.
Parli blackout?
226 days, 2015–16.
UPSC 2023 count?
Zero correct.
🎲 Practice: Coal Thermal Power Plants in India: How They Work and What They Cost
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