--- title: "Advantages and disadvantages of diesel plant" subject: "Power Plant Equipment" chapter: 5 key: "semester_7/power_plant_equipment:diesel-plant-merits-demerits" source: https://www.bctengineer.com/q/semester_7/power_plant_equipment/diesel-plant-merits-demerits site: BCT Engineering --- # Advantages and disadvantages of diesel plant Power Plant Equipment · Chapter 5: Diesel Power Plant - Asked in: 2073 Chaitra, 8 marks - Video: [Advantages And Disadvantages of Diesel Power Plant](https://www.youtube.com/watch?v=UYrmdPwJ2iY) — BEST MECHANICAL ENGINEERING - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/power_plant_equipment/diesel-plant-merits-demerits - Whole chapter: https://www.bctengineer.com/md/semester_7/power_plant_equipment/chapter-5 ## Question Discuss on advantages and disadvantages of Diesel Power Plant. ## Short answer Advantages: simple design, quick starting, small space, low initial cost, high efficiency (30-40%), less water, no standby losses, easy fuel handling, mobile. Disadvantages: high fuel cost, limited capacity (≤50 MW), high maintenance, noise/vibration, short life (10-15 years), poor overload capacity, exhaust pollution. ## Answer A diesel power plant generates electricity using a compression-ignition engine coupled to an alternator. It is mainly suited to small capacities, standby and peak duties, and isolated areas. #### Advantages 1. **Simple design and layout**; few auxiliaries compared with a steam plant (no boiler, condenser or ash handling). 2. **Quick starting and loading**: can be started and put on full load within a few minutes, so it is ideal for standby and peak loads. 3. **Small space** required; can be located near the load centre, reducing transmission cost. 4. **Low initial cost** per kW for small capacities; short construction time. 5. **High thermal efficiency** (about 30–40 %), better than small steam plants; good part-load efficiency. 6. **Less water** is needed (only for cooling). 7. **No standby losses**: fuel is used only when the engine runs. 8. Fewer operating staff; easy operation and automatic control. 9. Fuel is easy to handle and store; no ash disposal problem. 10. Can be **mobile** (skid or trailer mounted) and works independently of weather. #### Disadvantages 1. **High fuel cost**: diesel oil is costly and in Nepal must be imported, so running cost is high. 2. **Limited capacity**: unit size usually up to about 50 MW; not economical for large base-load stations. 3. **High maintenance and lubrication cost**; frequent overhauls of injectors, valves and liners. 4. **Noise and vibration** are severe; heavy foundations and silencers are needed. 5. **Short life** (about 10–15 years) compared with hydro (50 years or more) and steam stations (25–30 years). 6. **Overload capacity is poor**: engine cannot run long above rated load. 7. **Exhaust pollution** (NOx, smoke, particulates). 8. Cost per kW rises sharply with size. #### Comparison summary | Point | Diesel plant | Steam plant | |---|---|---| | Starting time | Minutes | Hours | | Capacity | Small (≤ 50 MW) | Large (100–1000 MW) | | Fuel cost | High | Low (coal) | | Space | Small | Large | | Water need | Small | Very large | | Life | 10–15 yr | 25–30 yr | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is a diesel plant suited to standby and peak duty? A. It starts and loads in a few minutes B. It takes hours to start C. It has huge capacity D. It has long life Answer: A. Quick starting and loading, compared with hours for a steam plant. (Key point: Quick starting) 2. What does "no standby losses" mean? A. Fuel is used only when the engine runs B. The plant never stops C. No fuel is required D. It cannot be shut down Answer: A. Unlike a boiler kept hot, a diesel engine consumes fuel only when running. (Key point: No standby losses) 3. Why is the running cost high in Nepal? A. Diesel is costly and imported B. Water is costly C. Land is costly D. Ash disposal Answer: A. High fuel cost is the main disadvantage. (Key point: Fuel cost) 4. How does a diesel plant compare with steam and hydro in size and life? A. Larger and longer-lived B. Limited to about 50 MW and about 10-15 years life C. Same life as hydro D. Over 100 MW with 50-year life Answer: B. Diesel units are limited in capacity and have short life compared with steam (25-30 years) and hydro (50+ years). (Key point: Capacity and life) 5. Which is a drawback listed? A. Large water need B. Poor overload capacity, severe noise and vibration, exhaust pollution C. Ash disposal D. Long construction time Answer: B. The engine cannot run long above rated load; noise, vibration and NOx/smoke are problems. (Key point: Overload and environment) ## Related in Power Plant Equipment - [Layout of diesel power plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-plant-layout) — Power Plant Equipment, chapter 5, asked 3× - [Fuel supply system of diesel plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-fuel-supply) — Power Plant Equipment, chapter 5, asked 3× - [Diesel plant components and fuel supply](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-components-fuel-supply) — Power Plant Equipment, chapter 5, asked 3× - [Diesel plant lubrication and cooling systems](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-lubrication-cooling) — Power Plant Equipment, chapter 5, asked 2× - [Reheat gas turbine power plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Agt-reheat-plant) — Power Plant Equipment, chapter 6 - [Advantages of combined power plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Acombined-advantages) — Power Plant Equipment, chapter 8 ## Related in other subjects - [Load duration curve; diesel plant; ROR flow duration](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Aload-duration-diesel-import-fdc) — Hydropower Engineering, chapter 3 - [Types of power supply system for industrial plant](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aindustrial-supply-system-types) — Industrial Power Distribution and Illumination, chapter 1, asked 2× - [Thermal versus nuclear power plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-vs-nuclear) — Power Plant Design, chapter 1, asked 2× - [Simple Rankine plant 2 MPa / 20 kPa: efficiency, power](https://www.bctengineer.com/question.md?key=semester_2%2Ffundamental_of_thermodynamics_and_heat_transfer%3Arankine-2mpa-20kpa-50kgs) — Fundamental of Thermodynamics & Heat Transfer, chapter 6