--- title: "Geothermal versus conventional thermal plant" subject: "Power Plant Design" chapter: 1 key: "semester_8/power_plant_design:geothermal-vs-thermal" source: https://www.bctengineer.com/q/semester_8/power_plant_design/geothermal-vs-thermal site: BCT Engineering --- # Geothermal versus conventional thermal plant Power Plant Design · Chapter 1: Energy Sources and Electric Power Generation - Asked in: 2077 Chaitra, 6 marks - Video: [Geothermal Energy and Geothermal Power Plant Working Principle](https://www.youtube.com/watch?v=JRchKsk3bPc) — EnergyProf - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/power_plant_design/geothermal-vs-thermal - Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-1 ## Question Compare Geothermal power plant with conventional thermal power plant considering various aspects. ## Short answer Geothermal uses earth's heat with nil fuel cost, low efficiency 10-20%, high capacity factor, and very low emissions, but is site-limited. Thermal plants burn coal, oil, or gas, give 30-40% efficiency, can be located flexibly, but have high fuel cost and pollution. ## Answer A **geothermal power plant** uses heat from the earth (steam or hot water from wells), while a **conventional thermal plant** burns coal, oil or gas in a boiler. Both drive steam turbines. #### Comparison | Aspect | Geothermal plant | Conventional thermal plant | |---|---|---| | Heat source | Earth's internal heat | Combustion of fossil fuel | | Fuel cost | Nil | High; major running cost | | Renewability | Renewable if reinjected | Non-renewable | | Location | Only at geothermal fields | Near load, port or coal mine | | Steam condition | Low pressure and temperature (about 150–250 °C) | High pressure, superheated (about 540 °C) | | Efficiency | Low, about 10–20% | About 30–40% | | Unit size | Small to medium (5–100 MW) | Large (100–800 MW) | | Boiler / fuel handling | Not needed | Boiler, coal handling, ash handling needed | | Capacity factor | High, about 90% (base load) | About 60–85% | | Load following | Poor; run as base load | Moderate | | Capital cost | High (exploration and drilling risk) | Moderate | | Emissions | Very low CO₂; some H₂S, mineral salts | High CO₂, SO₂, NOx, particulates | | Problems | Corrosion and scaling by minerals, reservoir depletion | Fuel supply, ash disposal | | Land use | Small | Large (fuel yard, ash ponds) | | Life | 30–50 years (if reservoir managed) | 25–30 years | #### Remarks Geothermal is cleaner and cheaper to run but is site-limited and has lower efficiency; thermal plants are flexible in location and size but costly to run and polluting. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How do fuel costs compare? A. Geothermal has nil fuel cost; thermal fuel cost is high B. Both have high fuel cost C. Geothermal fuel cost is higher D. Both have nil fuel cost Answer: A. Geothermal uses earth heat, so no fuel is bought. (Key point: Fuel cost) 2. Which statement about efficiency is correct? A. Geothermal about 30-40%, thermal 10-20% B. Geothermal about 10-20%, thermal about 30-40% C. Both about 90% D. Both about 50% Answer: B. Geothermal steam is low pressure and temperature, so efficiency is lower. (Key point: Efficiency) 3. Geothermal plants typically have a capacity factor of about A. 20% B. 40% C. 90% D. 10% Answer: C. They run as base load at about 90%, higher than thermal's 60-85%. (Key point: Capacity factor) 4. Where can a geothermal plant be located? A. Anywhere near a port B. Only at geothermal fields C. Near the coal mine D. Near load centres only Answer: B. It is site-limited, unlike thermal plants. 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