UPSC Prelims 2024 Q38: Science & Technology – Energy
- (a) Irrigation of terraced crop fields
- (b) Lift irrigation of cereal crops
- (c) Long duration energy storage
- (d) Rainwater harvesting system
Answer: (c) Long duration energy storage
Explanation
Pumped-Storage Hydropower — Best Description
Pumped-Storage Hydropower (PSH) is the world's largest form of grid-scale energy storage.
How it works:
1. Off-peak / surplus electricity (from wind, solar, or nuclear at night) pumps water from a lower reservoir to an upper reservoir
2. When electricity demand peaks, water flows back down through turbines to generate electricity
3. Cycle efficiency: ~70–85%
Why it is a "long-duration energy storage" system:
- Can store energy for hours to days (unlike batteries which store for minutes to hours at grid scale)
- Provides grid balancing — absorbs excess renewable energy and releases it when needed
- Addresses the intermittency problem of solar and wind
- India's target: 18.9 GW of PSH capacity by 2031-32
India Key PSH Projects:
| Project | State | Capacity | Notes |
|---|---|---|---|
| Tehri PSP | Uttarakhand | 1,000 MW | Operational |
| Koyna | Maharashtra | 80 MW | Operational |
| Greenko Pinnapuram | Andhra Pradesh | 1,200 MW | Largest under construction |
Best description = Long duration energy storage system.
Answer: (c) Long duration energy storage.
Why each option is right or wrong
- (a) Incorrect. Pumped storage is not a 'run-of-river' system — run-of-river diverts flowing river water through turbines without storage.
- (b) Incorrect. Pumped storage is not primarily an irrigation system, though reservoirs may serve dual purposes.
- (c) CORRECT. Pumped-storage hydropower is classified as a long-duration energy storage system. It stores electrical energy as potential energy of water and releases it over hours to days.
- (d) Incorrect. While pumped storage uses gravity, 'gravitational potential energy converter' is not the standard classification. The grid function — long-duration storage — is what defines it.
Key point
Pumped-storage = long-duration energy storage. Stores surplus electricity as elevated water, releases it as hydro power during peak demand.
Remember
Pumped-storage hydropower = long-duration energy storage. Surplus energy pumps water uphill; demand releases it through turbines.
Common mistakes
- Thinking pumped storage is just a type of hydropower dam — it is specifically a storage technology for grid balancing.
- Not connecting PSH to renewable energy integration — PSH solves solar/wind intermittency at grid scale.
- Confusing PSH with run-of-river hydro — run-of-river has no storage, PSH requires two reservoirs.
Exam tip
PSH = pump water up (charging) → release water down (discharging). Best description = long-duration energy storage. Key for UPSC's renewable energy integration questions. India target = 18.9 GW by 2031.
Sources
- Ministry of Power — Pumped Storage Policy 2023
- Central Electricity Authority — PSH Potential in India