---
title: "Power sources and hydro versus thermal"
subject: "Hydro Power"
chapter: 3
key: "semester_6/hydro_power:power-sources-hydro-vs-thermal"
source: https://www.bctengineer.com/q/semester_6/hydro_power/power-sources-hydro-vs-thermal
site: BCT Engineering
---

# Power sources and hydro versus thermal

Hydro Power · Chapter 3: Planning of Hydropower Projects

- Asked in: 2072 Asoj, 2+3 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/hydro_power/power-sources-hydro-vs-thermal
- Whole chapter: https://www.bctengineer.com/md/semester_6/hydro_power/chapter-3

## Question

What are the major sources of electric power generation? Discuss the relative merits and demerits of hydropower as compared to thermal power.

## Short answer

Major sources: hydro, thermal, nuclear, solar, wind, etc. Hydro has free water, high efficiency, no emissions, but high capital cost and seasonality. Thermal offers lower initial cost and steadier output but burns costly fuel and pollutant.

## Answer

#### Major sources of electric power generation
- **Conventional:** hydropower, thermal (coal, oil, diesel), gas turbine and combined cycle, nuclear.
- **Non-conventional (renewable):** solar (photovoltaic and solar thermal), wind, biomass and biogas, geothermal, tidal and wave energy, fuel cells.

#### Hydropower compared with thermal power

| Point | Hydropower | Thermal power |
|---|---|---|
| Fuel | Water, free and renewable | Coal/oil/gas, costly and finite |
| Initial cost | High (dam, tunnel) | Lower |
| Running cost | Very low | High (fuel) |
| Efficiency | 80–90% | 30–40% |
| Starting time | Few minutes; good for peak load | Hours; better for base load |
| Pollution | None in operation | Smoke, ash, CO₂, SO₂ |
| Life | 50–100 years | 25–40 years |
| Location | Fixed by site, often remote | Near load centre or fuel source |
| Construction time | Long | Shorter |
| Output | Depends on rainfall | Steady, independent of weather |

**Merits of hydropower:** no fuel cost, clean, high efficiency, long life, quick start, multipurpose use.

**Demerits of hydropower:** high capital cost and long construction time, output varies with season, remote sites need long transmission lines, and dams cause submergence and resettlement.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which set lists conventional sources?
   A. Solar, wind, tidal
   B. Biogas, geothermal, fuel cells
   C. Hydropower, thermal, gas turbine and nuclear
   D. Wave, biomass, solar
   Answer: C. Solar, wind, biomass, geothermal, tidal and wave are non-conventional. (Key point: Conventional sources)

2. Compared with thermal, hydropower has
   A. Low initial cost, high running cost
   B. High initial cost, very low running cost
   C. High initial and running cost
   D. Low initial and running cost
   Answer: B. Dams are costly but no fuel is needed. (Key point: Cost comparison)

3. Which is a demerit of hydropower relative to thermal?
   A. Pollution in operation
   B. Short plant life
   C. Slow starting
   D. Output depends on rainfall
   Answer: D. Thermal output is steady; hydro varies with season. (Key point: Output dependence)

## Related in Hydro Power

- [Stages of hydropower project study](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-study-stages) — Hydro Power, chapter 3, asked 3×
- [Layout of hydropower scheme components](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-scheme-layout) — Hydro Power, chapter 5
- [Advantages and limitations of hydropower](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-advantages-limitations) — Hydro Power, chapter 3
- [Pre-feasibility versus feasibility studies](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aprefeasibility-vs-feasibility) — Hydro Power, chapter 3
- [Firm power and plant load factors](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Afirm-power-load-factors) — Hydro Power, chapter 3
- [Flow and power duration curves](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aflow-power-duration-curves) — Hydro Power, chapter 3

## Related in other subjects

- [Hydro and thermal power sources](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Ahydro-thermal-sources) — Power System Analysis I, chapter 1
- [Types of electric drives with merits and demerits](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Aelectric-drive-types-merits) — Utilization of Electrical Energy, chapter 2
- [Thermal, hydro and solar PV plants compared](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-hydro-solar-pv) — Power Plant Design, chapter 1, asked 8×
- [Thermal versus hydro operational characteristics](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-vs-hydro-operational) — Power Plant Design, chapter 1, asked 8×