--- title: "Thermal, hydro and solar PV plants compared" subject: "Power Plant Design" chapter: 1 key: "semester_8/power_plant_design:thermal-hydro-solar-pv" source: https://www.bctengineer.com/q/semester_8/power_plant_design/thermal-hydro-solar-pv site: BCT Engineering --- # Thermal, hydro and solar PV plants compared Power Plant Design · Chapter 1: Energy Sources and Electric Power Generation - Asked in: 2070 Bhadra, 8 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/power_plant_design/thermal-hydro-solar-pv - Whole chapter: https://www.bctengineer.com/md/semester_8/power_plant_design/chapter-1 ## Question Compare the operational characteristics of thermal, hydro and solar PV plant on the basis of reliability, grid connection, efficiency, operating range and maintainability. ## Short answer Thermal is firm, dispatchable, 30–40% efficient, with high running cost and pollution. Hydro is 85–92% efficient, dispatchable 0–100%, starts in minutes, but needs high capital and long construction. PV is intermittent, 15–22% efficient, low capital, very low maintenance, and best as a complement to hydro. ## Answer **Thermal** plants burn fuel to produce steam for turbines; **hydro** plants use the potential energy of water; **solar PV** plants convert sunlight directly into electricity. #### Comparison | Basis | Thermal plant | Hydropower plant | Solar PV plant | |---|---|---|---| | Energy source | Coal, oil, gas | Water | Sunlight | | Reliability | Firm if fuel available; availability about 70–85% | Firm with storage; RoR seasonal; capacity factor about 50–65% | Daytime, weather dependent; capacity factor about 15–20% | | Grid connection | Synchronous; near load centres; inertia and voltage support | Synchronous; remote sites; long lines; black-start ability | Inverter based; no inertia; harmonics, voltage rise; near load possible | | Efficiency | About 30–40% | About 85–92% | About 15–22% | | Operating range | Above about 40–50% load; start in hours; slow ramp | 0–100%; starts in minutes; fast ramp; best for peak | Follows sunlight; not dispatchable; MPPT | | Load position | Base load | Peak (storage) / base (RoR in wet season) | Daytime energy supply | | Maintainability | Complex; many auxiliaries and staff | Moderate; sediment erosion, civil works | Very low; cleaning, inverters | | Running cost | High (fuel) | Very low | Very low | | Capital cost | Moderate | High | Low and falling | | Construction time | 3–4 years | 4–8 years | Months | | Life | 25–30 years | 50+ years | About 25 years | | Environment | CO₂, SO₂, NOx, ash | River ecology, submergence | Land use, panel disposal | #### Remarks - Thermal suits base load where fuel is cheap; hydro is the most efficient and flexible; PV is cheapest to build but intermittent. - In Nepal, hydro is the backbone, PV complements it in the dry season, and thermal (diesel) is kept only for emergency. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which set of efficiencies matches thermal, hydro and PV respectively? A. 85-92%, 30-40%, 15-22% B. 15-22%, 85-92%, 30-40% C. 30-40%, 85-92%, 15-22% D. 30-40%, 15-22%, 85-92% Answer: C. Thermal is about 30-40%, hydro 85-92% and PV module 15-22%. (Key point: Efficiency) 2. What is special about hydro operation? A. Dispatchable 0-100%, starts in minutes, fast ramp, best for peak B. Minimum load 40-50% C. Not dispatchable D. Starts in hours Answer: A. Hydro can start in minutes and ramp quickly, making it suited for peaking. (Key point: Hydro operating range) 3. Which is correct for hydro compared with PV? A. Hydro has lower capital cost and shorter life B. Hydro has high capital cost and 50+ year life; PV is low cost and about 25 years C. Both have same cost D. PV lasts 50+ years Answer: B. Hydro is capital-intensive but very long lived; PV is cheap and modular with about 25 years life. (Key point: Capital cost and life) 4. What is the role of the three plants in Nepal? A. Thermal is the backbone B. PV is the backbone, hydro for emergency C. Hydro is backbone, PV complements in dry season, thermal (diesel) for emergency D. All are equal Answer: C. Nepal depends on hydro; PV helps in the dry season; thermal diesel is standby. (Key point: Role in Nepal) ## Close variants set in other exams - [Solar versus hydro operational characteristics](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asolar-vs-hydro-economics) — Power Plant Design, chapter 1, asked 5× - [Thermal, wind and PV plants compared](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-wind-pv) — Power Plant Design, chapter 1, asked 7× - [Thermal, geothermal and PV plants compared](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-geothermal-pv) — Power Plant Design, chapter 1, asked 7× - [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× - [Thermal, geothermal and nuclear plants compared](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-geothermal-nuclear) — Power Plant Design, chapter 1, asked 7× ## Related in Power Plant Design - [Solar PV versus hydro and their combination](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asolar-pv-hydro-combination) — Power Plant Design, chapter 1 - [Hydropower versus solar PV in Nepal](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahydro-vs-solar-pv-nepal) — Power Plant Design, chapter 1 - [Grid-tied solar PV versus hydropower](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Agrid-tied-pv-vs-hydro) — Power Plant Design, chapter 1 - [Thermal versus hydro: load curve and stability](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-vs-hydro-load-curve) — Power Plant Design, chapter 1 - [Operational characteristics of combined cycle plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Accgt-operational-characteristics) — Power Plant Design, chapter 1