- Asked 7/21
- 2071 Magh · 10 marks
Thermal, geothermal and PV plants compared
Short answer
Thermal is firm, synchronous, 30–40% efficient, moderately flexible, but polluting with high fuel cost. Geothermal is steady base load with 80–90% capacity factor and only 10–20% efficiency, site-limited with corrosion issues. PV is intermittent, inverter-based, 15–20% capacity factor, low cost, simple maintenance, and clean.
Compare the operational characteristics of thermal, geothermal and PV plant on the basis of reliability, grid connection, efficiency, operating range and maintainability.
Thermal power plants burn fossil fuel to raise steam; geothermal plants take steam or hot water from the earth's heat; PV plants convert sunlight directly into DC electricity using semiconductor cells.
Working in brief
Thermal: Fuel -> Boiler -> Steam -> Turbine -> Gen
Geotherm: Well -> Separator/HX -> Turbine -> Gen
(brine reinjected)
PV: Sun -> PV array -> Inverter -> Grid
Comparison
| Basis | Thermal | Geothermal | Solar PV |
|---|---|---|---|
| Reliability | Firm and dispatchable if fuel is available; availability about 70–85% | Very steady; capacity factor about 80–90%; resource declines if brine is not reinjected | Only in sunshine; capacity factor about 15–20%; needs storage/backup |
| Grid connection | Large synchronous units near load; provide inertia and reactive power | Synchronous units of 5–100 MW at remote geothermal fields; long lines may be needed | Inverter based; no inertia; harmonics, voltage rise and reverse flow; can connect at distribution level |
| Efficiency | About 30–40% | About 10–20% | About 15–22% (module), system lower |
| Operating range | Minimum stable load about 40–50%; slow start (hours); moderate ramp | Base load; little load-following ability | Output from zero to peak by irradiance; MPPT; not dispatchable |
| Maintainability | Complex; boiler, coal and ash handling, cooling system; many skilled staff | Corrosion and scaling by dissolved minerals; well workovers | Very low; module cleaning, inverter replacement every 10–15 years; no moving parts |
| Fuel cost | High | Nil | Nil |
| Capital cost | Moderate | High (exploration and drilling risk) | Low and falling |
| Construction time | 3–4 years | 3–6 years | Months |
| Location | Flexible | Only at geothermal fields | Wherever there is sunshine and land/roof |
| Environment | CO₂, SO₂, NOx, ash | Low; H₂S, minerals, land subsidence | Clean in operation; land use and panel disposal |
| Life | 25–30 years | 30–50 years | About 25 years |
Remarks
- Thermal: most flexible in location and output, but high fuel cost and pollution.
- Geothermal: ideal clean, firm base load where the resource exists; but inflexible (little load following) and site-limited.
- PV: cheapest and simplest to build and maintain, but intermittent; best combined with hydro or storage.
For Nepal, thermal is limited to diesel standby, geothermal is only at low-temperature hot springs (direct use), and PV is growing as a complement to run-of-river hydro.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Thermal, geothermal and nuclear plants compared · Power Plant Design, chapter 1 · asked 7×
- Thermal, wind and PV plants compared · Power Plant Design, chapter 1 · asked 7×
- Thermal versus hydro operational characteristics · Power Plant Design, chapter 1 · asked 8×
- Thermal, hydro and solar PV plants compared · Power Plant Design, chapter 1 · asked 8×
- Solar versus hydro operational characteristics · Power Plant Design, chapter 1 · asked 5×
- Geothermal versus conventional thermal plant · Power Plant Design, chapter 1
- Solar PV versus hydro and their combination · Power Plant Design, chapter 1
- Hydropower versus solar PV in Nepal · Power Plant Design, chapter 1
- Grid-tied solar PV versus hydropower · Power Plant Design, chapter 1
- Operational characteristics of combined cycle plant · Power Plant Design, chapter 1