India’s Green Transition Is Missing Long-Duration Energy Storage

Why in the News?

India recorded its highest-ever electricity peak demand of 270.8 GW on May 21, exposing gaps in the country’s storage architecture during periods of low renewable generation. This has sharpened focus on long-duration energy storage (LDES), a category entirely absent from India’s current national storage planning framework despite its technologies and resource potential already existing.

Why did India’s existing storage roadmap prove inadequate against actual demand patterns?

1. Record peak demand: India recorded its highest-ever peak electricity demand of 270.8 GW on May 21. This is an increase of approximately 90 GW over the same period in 2019.
2. Dual demand peaks: Power generators typically meet India’s summer daytime peak. Demand rises again at night, driven largely by air conditioner use, precisely when solar generation is unavailable.
3. Roadmap’s duration ceiling: The 2026 Long-Term National Resource Adequacy Plan envisages 80 GW of battery energy storage and 94 GW of Pumped Hydroelectric Energy Storage (PHES) by FY2035-36. These translate to average discharge durations of roughly 4 hours and 6 hours, respectively.
4. Adverse-weather gap: Four-to-six-hour storage can manage routine daily demand swings. It cannot sustain the grid through prolonged low-generation events such as heatwaves.

What technologies make up India’s Long-Duration Energy Storage (LDES) landscape, and how do they compare?

1. Definition: LDES refers to technologies that store energy and discharge it as power or thermal energy over extended periods, ranging from 8 hours to days, weeks, or seasons.
2. Functional distinction: Short-duration storage systems discharge for under 8 hours and smooth intra-day demand fluctuations. LDES instead balances supply and demand over prolonged periods, eases grid congestion, and adds resilience.
3. Pumped Hydroelectric Energy Storage (PHES): PHES remains the technology benchmark. It has mature infrastructure and an energy efficiency of 70-80%.
4. Compressed-Air Energy Storage (CAES): CAES has a similar level of market readiness to PHES. Its efficiency is slightly lower, at 40-70%.
5. Thermal and hydrogen storage: Thermal storage offers the longest discharge duration among developed technologies, around 200 hours, with 55-90% efficiency. Hydrogen-based storage can discharge for up to 1,000 hours but remains inefficient.
6. Vanadium flow batteries and emerging tech: Vanadium flow batteries are commercially ready, come in different sizes, and deliver 80-85% efficiency across 10-24 hour durations. Iron-air batteries are an emerging technology still under development.

Why do cost and site constraints limit LDES deployment despite its technical readiness?

1. Duration-cost relationship: Longer discharge duration improves a technology’s economics. Storing more energy simultaneously raises total costs, making short-duration systems uncompetitive beyond six hours of discharge.
2. Cheapest options: PHES and CAES are currently the most cost-effective and commercially viable LDES technologies, at $0.12/kWh and $0.10/kWh respectively, per a Pacific Northwest National Laboratory study.
3. Site dependency of PHES: PHES needs two water reservoirs at different heights, adequate land, and sufficient height difference for water to generate force when released.
4. Site dependency of CAES: CAES needs large underground spaces, such as salt caverns or depleted gas fields, that can safely hold high-pressure air without leaking.
5. Site-flexible alternatives: Where such geological or land conditions are unavailable, hydrogen, thermal storage, or vanadium flow batteries are more suitable, since they depend less on specific land, water, or subterranean conditions.

What do international institutional and regulatory models demonstrate about accelerating LDES investment?

1. LDES Council (international industry body): This body brings together industry leaders, technology developers, investors, and policymakers to accelerate LDES innovation and commercialisation. It projects a significant decline in LDES costs by 2030.
2. United States-Pacific Northwest National Laboratory: This research body, under the U.S. Department of Energy, benchmarked PHES and CAES as the most cost-effective LDES technologies at present.
3. California-Public Utilities Commission: California’s primary utility regulator has set an LDES procurement target of 2 GW, to be deployed between 2031 and 2037.
4. United Kingdom- investor revenue guarantee: The U.K. has launched a financial framework guaranteeing LDES projects a minimum revenue even in poor market conditions, to unlock investment and accelerate deployment.

Where does India currently stand on LDES resource potential and deployment?

1. PHES potential: A 2026 Central Electricity Authority report placed India’s PHES potential at about 267 GW.
2. Planned PHES capacity: India plans to install PHES projects with an aggregate capacity of 100.8 GW by 2035-36. Of this, 11.6 GW is currently under construction.
3. CO2 battery pilot: In early 2025, India launched a 160-MWh carbon dioxide battery storage system at NTPC Kudgi, Karnataka. It cycles carbon dioxide between liquid and gas phases and has an operational life exceeding 25 years.
4. Vanadium flow pilot: India inaugurated its first MWh-scale vanadium redox flow battery system, a 3-MWh facility at NTPC Greater Noida.

Why does India’s national storage planning still not recognise LDES as a category?

1. Resource Adequacy Plan silence: The Long-Term National Resource Adequacy Plan acknowledges the general role of energy storage in grid reliability. It does not specifically recognise the need for LDES.
2. National Electricity Plan silence: The National Electricity Plan projects capacities for battery energy storage systems and PHES. It provides no technology-specific assessments or deployment pathways for LDES.
3. Capability-recognition gap: India already has a 267 GW PHES resource base and functioning LDES pilot projects. National planning documents do not treat LDES as a distinct storage category requiring its own targets or provisions.

What policy and institutional measures would close India’s LDES planning gap?

1. Framework integration: LDES should be incorporated into the Ministry of Power’s National Framework for Promoting Energy Storage Systems, with guidelines on its deployment and grid integration.
2. Technology-specific planning: Future planning exercises should estimate LDES requirements and identify technologies suited to India’s extreme weather and geography, rather than treating storage as a single undifferentiated category.
3. Clearances and regulatory classification: Faster environmental and land clearances, transmission alignment, and clear regulatory classification of LDES technologies are needed to unlock investment.
4. Technology-agnostic incentives: The incentive structure, including subsidies and viability-gap funding, must be technology-agnostic and incentivise co-location with data centres. As the market matures, the focus must shift to long-term revenue contracts, tariff structures, and procurement frameworks.
5. Capacity building: Dispatch centres need staff trained in optimal dispatch, multi-day charge-discharge decisions, and state-of-charge management across seasons, supported by clear protocols for LDES.

Conclusion

India’s storage roadmap treats energy storage as a short-duration, hourly balancing problem, while a renewables-heavy grid increasingly requires multi-day resilience. LDES technologies and resource potential already exist in India; what is missing is formal policy recognition, technology-specific planning, and an incentive architecture built around them. Unless LDES is written into national storage planning documents, India’s clean energy transition will remain dependent on favourable weather and market conditions rather than assured grid reliability.