- 2075 Bhadra · 7+3 marks
Solar PV versus hydro and their combination
Short answer
PV has 15–20% capacity factor, inverter-based grid connection with no inertia, 15–22% efficiency, non-dispatchable output, and very low maintenance. Hydro has 50–65% capacity factor, synchronous connection, 85–92% efficiency, 0–100% dispatchability, and higher maintenance. Combining them uses the reservoir as a battery, with solar in dry season and hydro for evening peaks and frequency support.
Compare the operational characteristics of solar photovoltaic power plant with hydropower plant on the basis of reliability, grid connection, efficiency, operating range, maintenance perspectives and so on. Also, discuss the beauty of combination of such two kinds of power project for an electric system.
A solar PV plant converts sunlight directly to DC electricity, delivered to the grid or loads through inverters. A hydropower plant converts the energy of water through turbines and synchronous generators.
Comparison of operational characteristics
| Basis | Solar PV plant | Hydropower plant |
|---|---|---|
| Reliability | Daytime only; cloud dependent; capacity factor about 15–20% | Day and night; RoR seasonal; storage firm; capacity factor about 50–65% |
| Grid connection | Inverter based; no inertia; anti-islanding, harmonics, voltage rise issues | Synchronous; inertia, reactive support, frequency control, black-start |
| Efficiency | Module about 15–22% | About 85–92% |
| Operating range | Not dispatchable; output set by irradiance; curtail only | 0–100% dispatchable via governor; fast ramp |
| Maintenance | Very low; module cleaning, inverter replacement every 10–15 years | Turbine, gates, civil works; sediment erosion; skilled staff |
| Construction time | Months | Years |
| Capital cost | Low, modular | High |
| Life | About 25 years | 50+ years |
| Location | Near load, rooftops, flat land | Fixed by river and head |
Beauty of combining solar PV and hydro
- Seasonal complement – in Nepal, river flows are low in the dry season (winter, spring), when skies are clear and solar output is high; in the monsoon, hydro is abundant.
- Daily complement – solar supplies daytime energy; the hydro reservoir saves water during the day and releases it for the evening peak. The reservoir acts as a large, cheap "battery".
- Smoothing variability – fast hydro governors balance sudden changes in solar output due to clouds, keeping frequency stable.
- Grid strength – synchronous hydro machines provide inertia and voltage support that inverter-based PV lacks.
- Shared infrastructure – floating PV on hydro reservoirs uses the same substation and transmission line; less land needed and less evaporation.
- Better economics – higher utilisation of transmission lines and lower need for battery storage.
Power
| solar
| /^^^^\ hydro raised
| / \ for evening peak
|-----/--------\-----------/^^^\----
| hydro (held back by day) \__
+---------------------------------> hour
0 6 12 18 24
Such a hybrid system gives reliable, clean and low-cost supply.
✓ Answer checked by Claude Opus 5.5 (high effort)
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