- 2072 Magh · 8 marks
Hydro versus thermal: techno-economic and environmental
Short answer
Hydro has 85-92% efficiency, fast start, excellent load following, zero fuel cost, low O&M, long life, but high capital and long construction. Thermal has 30-40% efficiency, slow start, firm output, high fuel and O&M cost, shorter life, and causes air and thermal pollution. Hydro is clean but capital intensive.
Compare the operational characteristics of the hydroelectric power plant and thermal power plant considering factors such as techno-economic, environmental and so on.
A hydroelectric plant converts the potential energy of stored or flowing water into electricity, while a thermal plant burns fuel to make steam that drives a turbine.
Technical comparison
| Aspect | Hydroelectric plant | Thermal plant |
|---|---|---|
| Energy source | Water; renewable | Coal, oil, gas; exhaustible |
| Efficiency | 85–92% | 30–40% |
| Starting time | Few minutes | Several hours |
| Load following | Excellent; peak load | Poor; base load |
| Operating range | Wide | Narrow (above about 40–50%) |
| Reliability | Seasonal (RoR), firm with storage | Firm if fuel is available |
| Location | Fixed by river and head; remote | Flexible, near load |
| Transmission | Long lines | Short lines |
| Auxiliaries | Few | Many (boiler, coal and ash handling, cooling) |
| Life | 50–100 years | 25–30 years |
Economic comparison
| Aspect | Hydroelectric plant | Thermal plant |
|---|---|---|
| Capital cost | High (dam, tunnel, powerhouse) | Lower |
| Construction time | Long (4–10 years) | Shorter (3–4 years) |
| Fuel cost | Nil | High; most of running cost |
| O&M cost | Low; few staff | High; many staff |
| Cost per kWh over life | Low | High, rises with fuel price |
| Risk | Geology, hydrology, sediment | Fuel price and supply |
Environmental and social comparison
| Aspect | Hydroelectric plant | Thermal plant |
|---|---|---|
| Air pollution | None in operation | CO₂, SO₂, NOx, particulates |
| Waste | None | Fly ash, bottom ash |
| Water impact | Changes river flow, fish migration, sediment | Thermal pollution of cooling water |
| Land | Submergence by reservoir; resettlement | Land for plant, coal yard, ash pond |
| Other benefits | Irrigation, flood control, drinking water, tourism | Employment in mining |
| Climate | Small GHG (some methane from reservoirs) | Large GHG emission |
Remarks
Hydro has high initial cost but very low running cost, long life and clean operation; thermal is cheaper and quicker to build but expensive to run and polluting. For Nepal, with large hydro potential and no fossil fuel, hydro is the main option, with thermal only as standby.
✓ Answer checked by Claude Opus 5.5 (high effort)
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