Introduction
India's transition towards a renewable energy-based economy has reached a crucial stage. While the country has made remarkable progress in expanding solar and wind power, ensuring a continuous electricity supply remains a major challenge because these sources are intermittent. Long Duration Energy Storage (LDES) is emerging as the technology that can bridge this gap and ensure reliable, clean, and affordable electricity.
Why is Long Duration Energy Storage Suddenly Important?
India's electricity demand is growing at an unprecedented pace. On 21 May 2025, the country recorded its highest-ever peak electricity demand of 270.8 GW, almost 90 GW higher than the corresponding period in 2019. The surge was mainly driven by prolonged heatwaves, rapid urbanisation, rising ownership of air conditioners, industrial expansion, digital infrastructure, electric vehicles, and data centres.
During summer afternoons, electricity generation is generally sufficient because solar power plants operate at maximum capacity. However, the real challenge begins after sunset. Electricity demand continues to remain high as households and commercial establishments continue using cooling appliances, whereas solar generation falls to zero and wind generation may also decline depending on weather conditions. This creates a mismatch between electricity generation and electricity demand.
Consequently, India's challenge is no longer limited to generating renewable electricity; it is increasingly about storing electricity when it is available and supplying it whenever required.
What is Long Duration Energy Storage (LDES)?
Long Duration Energy Storage refers to technologies capable of storing electricity and delivering it continuously for more than eight hours, extending to several days, weeks, or even entire seasons depending on the technology.
Unlike conventional batteries that mainly balance daily fluctuations, LDES is designed to provide sustained electricity during prolonged periods of low renewable generation caused by cloudy weather, weak winds, or extreme climatic events.
In simple terms,
- Short-duration storage balances electricity within a single day.
- Long-duration storage maintains electricity supply across multiple days or adverse weather conditions.
Thus, LDES acts as the backbone of a renewable-dominated electricity grid.
How Electricity Reaches the Consumer: The Complete Process
The electricity system operates through a sequence of interconnected stages.
Coal / Solar / Wind / Hydro / Nuclear ↓ Electricity Generation ↓ High Voltage Transmission (Power Grid Corporation of India) ↓ State & Private Distribution Companies (DISCOMs) ↓ Homes • Industries • Agriculture ↓ Electricity Consumption
In a renewable-rich system, electricity storage is inserted between generation and distribution.
Solar & Wind Generation ↓ Excess Electricity Produced ↓ Stored in LDES Technologies ↓ Night / Cloudy Weather / Heatwaves ↓ Stored Electricity Released ↓ Consumers Receive Reliable Supply
Without adequate storage, excess renewable electricity generated during the day often goes unused, while shortages occur during evenings or prolonged cloudy periods.
India's Existing Energy Storage Roadmap
Recognising the growing importance of storage, India's Long-Term National Resource Adequacy Plan (2026) proposes the installation of approximately:
- 80 GW of Battery Energy Storage Systems (BESS)
- 94 GW of Pumped Hydro Energy Storage (PHES)
by 2035–36.
However, these systems are expected to provide average discharge durations of only 4 hours (battery storage) and 6 hours (pumped hydro).
Such capacities are adequate for handling normal day-to-day fluctuations but are unlikely to sustain the electricity system during multi-day heatwaves, prolonged cloudy weather, or weak wind conditions. This is where Long Duration Energy Storage becomes indispensable.
Why LDES Matters for India's Renewable Future
India has committed to achieving 500 GW of non-fossil electricity capacity by 2030 and Net Zero emissions by 2070. As renewable energy occupies a larger share of the electricity mix, maintaining grid reliability becomes increasingly difficult.
LDES can help by:
- storing surplus renewable electricity instead of wasting it,
- supplying electricity during night-time demand,
- reducing dependence on coal-based peaking power,
- preventing grid instability,
- supporting disaster resilience during extreme weather,
- enabling higher renewable penetration without compromising reliability.
It therefore serves as the "insurance policy" of a renewable electricity system.
Major Long Duration Energy Storage Technologies
1. Pumped Hydro Energy Storage (PHES)
Pumped hydro is currently the world's most mature and commercially proven storage technology.
During periods of surplus electricity, water is pumped from a lower reservoir to an upper reservoir. When electricity demand increases, the stored water is released downhill through turbines to generate electricity.
Surplus Electricity ↓ Water Pumped Uphill ↓ Upper Reservoir ↓ Electricity Demand Rises ↓ Water Released ↓ Turbine Rotates ↓ Electricity Produced
- Efficiency: 70–80%
- Commercial maturity: Very high
- Life span: More than 50 years
However, it requires suitable geography, adequate land, two reservoirs at different elevations, and sufficient water availability.
According to the Central Electricity Authority (2026), India possesses a PHES potential of around 267 GW, while projects totaling 100.8 GW are planned by 2035–36. Approximately 11.6 GW is already under construction.
2. Compressed Air Energy Storage (CAES)
CAES stores surplus electricity by compressing air into underground caverns. During periods of high demand, the compressed air is released to drive turbines and generate electricity.
- Efficiency: 40–70%
- Commercial maturity: High
Its deployment is limited because it requires naturally occurring underground formations such as salt caverns or depleted gas fields.
3. Thermal Energy Storage
Thermal storage systems retain heat using materials such as molten salts or high-temperature solids.
One of their biggest advantages is extremely long discharge durations, often reaching around 200 hours, making them useful for concentrated solar power plants and industrial heat applications.
Efficiency ranges between 55% and 90%, although many technologies are still under development.
4. Hydrogen-Based Energy Storage
Surplus renewable electricity is used to split water into hydrogen through electrolysis. The hydrogen is stored and later converted back into electricity using fuel cells or turbines.
Hydrogen offers one of the longest storage durations—up to 1,000 hours—making it suitable for seasonal energy storage. However, it currently suffers from relatively low efficiency and high production costs.
5. Vanadium Redox Flow Batteries
Flow batteries store electricity in liquid electrolytes circulating through external tanks.
Compared to conventional lithium-ion batteries, they offer:
- longer operating life,
- easier scalability,
- better safety,
- discharge durations of 10–24 hours, and
- efficiencies of 80–85%.
India commissioned its first MWh-scale Vanadium Redox Flow Battery (3 MWh) at NTPC, Greater Noida in 2025.
6. Emerging Technologies
Researchers are also developing advanced storage technologies such as iron-air batteries, which promise multi-day electricity storage at significantly lower costs. Although not yet commercially mature, they could become a major component of future electricity systems.
Economics of Long Duration Storage
Although LDES technologies generally require higher initial investments, they become increasingly economical as storage duration increases.
For discharge periods beyond six hours, conventional lithium-ion batteries become progressively more expensive, whereas technologies such as Pumped Hydro and Compressed Air Energy Storage remain cost-effective.
According to studies by the Pacific Northwest National Laboratory, the current storage costs are approximately:
- PHES: US$0.12 per kWh
- CAES: US$0.10 per kWh
The LDES Council, an international consortium of governments, industries, researchers, and investors, projects that costs will decline substantially by 2030, making these technologies increasingly competitive.
India's Recent Developments
India has recently accelerated its efforts in advanced storage technologies.
In 2025, NTPC Kudgi (Karnataka) commissioned a 160 MWh Carbon Dioxide Battery, which stores energy by cycling carbon dioxide between liquid and gaseous states. The system has an operational life exceeding 25 years.
Soon after, India inaugurated its first 3 MWh Vanadium Redox Flow Battery at NTPC Greater Noida, marking an important milestone in indigenous deployment of advanced storage technologies.
Policy Gaps
Despite recognising the importance of energy storage, India's current policy framework still treats storage largely as a supporting technology rather than a strategic pillar.
The Long-Term National Resource Adequacy Plan, National Electricity Plan, and the National Framework for Promoting Energy Storage Systems provide capacity projections for battery storage and pumped hydro, but they do not specifically identify Long Duration Energy Storage as a separate planning category or estimate India's future LDES requirements.
Similarly, deployment pathways, technology-specific incentives, market mechanisms, and procurement strategies remain underdeveloped.
Challenges
The widespread deployment of LDES faces several challenges.
Technically, many advanced storage technologies are still evolving, while domestic manufacturing capacity remains limited.
Financially, high upfront costs and uncertain revenue streams discourage private investment.
Regulatory challenges include the absence of dedicated tariff mechanisms, lack of market signals for long-duration storage, and delays in environmental and land clearances.
For technologies such as Pumped Hydro and Compressed Air Energy Storage, suitable geographical conditions are another major constraint.
Finally, India's grid operators require specialised training to optimise multi-day storage operations and seasonal energy management.
Way Forward
India should explicitly incorporate Long Duration Energy Storage into the National Framework for Promoting Energy Storage Systems and future National Electricity Plans.
Policy support should remain technology-neutral, allowing Pumped Hydro, Flow Batteries, Hydrogen, Thermal Storage, and emerging technologies to compete fairly.
Financial incentives such as Viability Gap Funding, long-term procurement contracts, and revenue assurance mechanisms can attract private investment. Simultaneously, faster environmental clearances, integrated transmission planning, and co-location of storage facilities with renewable parks and data centres should be prioritised.
Investment in indigenous research, domestic manufacturing, and skill development for grid operators will also be essential to build a resilient storage ecosystem.
Significance for UPSC Mains
This topic is highly interdisciplinary and can enrich answers across several GS-III themes.
- Energy Security: LDES ensures reliable electricity even during prolonged renewable shortfalls.
- Infrastructure: It strengthens India's electricity grid and supports the transition to a modern, flexible power system.
- Climate Change: It reduces dependence on coal-based peaking power and enables deeper renewable integration.
- Economy: Reliable electricity supports manufacturing, digital infrastructure, data centres, electric mobility, and industrial competitiveness.
- Science & Technology: It highlights emerging technologies such as hydrogen storage, flow batteries, carbon dioxide batteries, and iron-air batteries.
- Disaster Management: LDES enhances resilience against heatwaves, prolonged cloudy weather, and other climate-induced disruptions.
- Viksit Bharat 2047: A stable, low-carbon electricity system backed by LDES is indispensable for achieving sustainable economic growth, energy independence, and India's long-term climate commitments.
Conclusion
India has made remarkable progress in renewable energy generation, but its clean energy transition cannot succeed without reliable storage. Long Duration Energy Storage provides the flexibility, resilience, and reliability needed to power a renewable-rich economy. By integrating LDES into national planning today, India can secure a cleaner, more resilient, and energy-secure future while advancing towards the vision of Viksit Bharat 2047.
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