- 2082 Shrawan · 8 marks
Hydropower versus solar PV in Nepal
Short answer
Hydro is firm, dispatchable, grid-friendly with inertia and black-start, 85-92% efficient, but high sediment and long transmission. Solar PV is intermittent, inverter-based, 15-22% efficient, simple maintenance, quick install. In Nepal, dry-season solar complements monsoon-dependent run-of-river hydro; a hydro-solar mix with storage is most reliable.
Compare the electric power from hydropower with solar photovoltaic based power generation on the basis of reliability, grid-connection, efficiency, operating range and maintainability. Also consider the scenario in Nepalese context during comparison.
Hydropower converts the potential energy of water into electricity using a turbine and synchronous generator. Solar photovoltaic (PV) converts sunlight directly into DC electricity in semiconductor cells, converted to AC by inverters.
Comparison
| Basis | Hydropower | Solar PV |
|---|---|---|
| Reliability | Firm for storage; run-of-river depends on seasonal flow but gives output day and night | Only in daytime; drops with clouds; capacity factor about 15–20%; needs storage or backup |
| Grid connection | Synchronous generators; provide inertia, voltage and frequency control; can black-start | Through inverters; no natural inertia; harmonics and reverse power flow issues; needs grid-support functions |
| Efficiency | About 85–92% (water to wire) | Module about 15–22%; system about 12–18% |
| Operating range | Wide control 0–100% via governor; dispatchable | Output follows sunlight; not dispatchable; MPPT tracks maximum power |
| Maintainability | Turbine erosion by sediment, civil works, skilled staff | Very low: module cleaning, inverter replacement (10–15 years) |
| Construction time | Long, 4–8 years | Short, months |
| Capital cost | High civil cost | Falling fast; modular |
| Life | 50+ years | About 25 years |
| Environmental impact | River ecology, land submergence | Land use; panel disposal |
Nepalese context
Hydropower:
- Nepal's grid is almost fully hydro (over 3,000 MW installed). Most plants are run-of-river; only Kulekhani is a seasonal storage project.
- Output is high in the monsoon (surplus, exported to India) and falls to about a third in the dry season (deficit, imports).
- High sediment in Himalayan rivers causes turbine erosion and maintenance cost.
- Long transmission lines from hills to load centres.
Solar PV:
- Good solar resource: about 4.5–5.5 kWh/m²/day, around 300 sunny days.
- Solar output is highest in the dry season (clear skies), when hydro output is low, so it complements run-of-river hydro.
- Widely used in remote areas (solar home systems, mini-grids, solar irrigation pumps) and in growing grid-tied plants in the Terai.
- Limited by land cost, lack of storage and inverter-based grid issues; net metering for rooftop solar has been introduced.
Conclusion
Hydro gives cheap, controllable bulk power and grid stability; solar PV is quick to install and fills the dry-season and daytime gap. For Nepal, a hydro–solar mix with hydro reservoirs acting as storage is the most reliable approach.
✓ Answer checked by Claude Opus 5.5 (high effort)
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