Differentiate between short-duration and long-duration energy storage technologies. Why is LDES critical for India's grid reliability during extreme weather events?

Energy storage is classified by how long it can continuously discharge. India's storage build-out is designed around hours, while climate-stressed grids increasingly need power for days — the gap that Long-Duration Energy Storage (LDES) is meant to fill.

Short-duration vs long-duration storage: key differences

• Discharge duration: short-duration systems discharge for roughly 4–8 hours — battery storage averages ~4 hours and pumped hydro ~6 hours in the Central Electricity Authority's long-term plan [1]; LDES discharges over multiple days.
• Grid function: short-duration storage shifts surplus solar to the evening peak and supplies frequency regulation and ancillary services; LDES covers multi-day renewable generation droughts and seasonal balancing.
• Technology: lithium-ion batteries (BESS) and pumped hydro (PHES) dominate the short/medium range [1][2]; LDES relies on flow batteries, compressed-air, thermal storage and green hydrogen, largely pre-commercial in India.
• Economics: longer discharge improves utilisation per unit of capacity, but the total cost of storing more energy rises — deterring investment without targeted policy support.
• Policy coverage: the National Electricity Plan projected ~208 GWh of BESS by 2029-30 [3], and the Long-Term National Resource Adequacy Plan (2026-27 to 2035-36) targets 80 GW BESS and 94 GW PHES [1] — all short-to-medium duration.

Why LDES matters for extreme-weather reliability

• Prolonged low-output spells: overcast, low-wind conditions can suppress solar and wind for several days; 4–6 hour storage is exhausted in a single evening.
• Heatwave-driven night peaks: peak demand crossed 270 GW in May 2026, matching CEA's FY2026-27 projection [1], as cooling load persists long after sunset.
• Avoiding fossil fallback: without multi-day cover, utilities revert to costly coal and gas peaking plants, weakening non-fossil targets [2].
• Disaster resilience: cyclones and floods that disrupt transmission make locally stored, long-duration energy vital.

India's storage planning has correctly solved the daily cycle; the residual risk is the multi-day one. Embedding LDES pilots, duration-differentiated storage obligations and viability-gap support within CEA's resource adequacy framework would align grid reliability with India's clean-energy and climate-resilience commitments.