Distinguish between on-stream and off-stream closed-loop pumped storage schemes. Why is policy moving towards the latter?

Pumped Storage Projects (PSPs) are often called the "water battery". They store surplus solar and wind power by pumping water to an upper reservoir, then release it through turbines when demand peaks [1]. The CEA projects that India will need 26.69 GW of PSP storage by 2031–32 [1]. To build that much in time, policy is shifting away from river-based designs towards off-stream closed-loop schemes.

Distinction

Basis	On-stream	Off-stream closed-loop
Reservoir location	Both reservoirs on a river, stream or nallah [1]	Neither reservoir on a river or perennial stream/nallah [1]
River flow	Dam changes natural flow, sediment and fish movement	Same water circulates between two reservoirs; river flow undisturbed
Siting	Only suitable river valleys	Hills, plateaus, even exhausted coal-mine pits [3]
Clearance	Full CEA appraisal	Exempt from CEA concurrence [2]

There is also an in-between type, off-stream open-loop, where one reservoir sits on a watercourse [1].

Why policy favours closed-loop

• Ecology: off-stream sites harm aquatic ecology less [1]. They avoid flooding river valleys and reducing flow downstream.
• Faster approvals: closed-loop schemes need no CEA concurrence, whatever their capital cost. For other PSPs, CEA review of the DPR (detailed project report) now takes 50 days instead of 90 [2].
• Lighter environmental review: MoEF&CC's August 2023 Terms of Reference ask for one season of baseline data for closed-loop projects and two seasons for open-loop ones [2].
• More sites: MoP's 2023 Guidelines allow exhausted coal mines to be used as sites [3]. This puts degraded land in coal belts back to use.
• Speed for the energy transition: schemes away from rivers displace fewer people and avoid water-sharing disputes. That helps India store power for its target of 500 GW of non-fossil capacity by 2030 [1].

Caveats to manage

• Reservoirs built on karst (cracked limestone) or other porous ground can lose water through seepage [4]. Cracked mine pits may carry the same risk.
• One season of baseline data cannot show how a site behaves in both the monsoon and the dry months.

Off-stream closed-loop PSPs have little impact on rivers and can be built quickly and at scale, which explains the policy shift. Fast approvals should be paired with site-specific studies of geology and groundwater. That way India can expand long-duration storage without harming ecology, advance SDG 7 (affordable, clean energy) and support a reliable grid built on 500 GW of non-fossil capacity.