CHENNAI: Tamil Nadu is set to play a pivotal role in India's push to scale up pumped storage projects (PSPs), as the state is projected to require around 13,581 MW of energy storage capacity by 2034-35 to support its rapidly expanding renewable energy base.
In its roadmap to achieve 100 GW of PSP capacity by 2035-36, the Central Electricity Authority has proposed regulatory relaxations to accelerate such projects, including in eco-sensitive zones of the Western Ghats.
The report emphasises that long-duration energy storage has become critical for southern states like Tamil Nadu, where the share of wind and solar power is high and grid-balancing challenges are becoming more acute.
As per the resource adequacy assessment, Tamil Nadu alone will require about 13,581 MW of energy storage capacity, including both PSP and Battery Energy Storage System capacity, by 2034-35. This is the second-highest requirement among states to reliably integrate renewable energy beyond 2030, after Uttar Pradesh targets 25,437 MW.
Based on studies by the Central Electricity Authority, long-term storage of around six hours is required to integrate higher volumes of renewable energy beyond 2030, the report noted.
The authority has estimated India's overall pumped storage potential at about 2,67,000 MW, comprising 58,000 MW of on-stream PSPs and 2,09,000 MW of off-stream PSPs. Tamil Nadu's assessed pumped storage potential is approximately 21,300 MW.
Of this, 400 MW is operational at the Kadamparai pumped storage station, while 500 MW is under construction through the Kundah stages I, II and III projects. Another 1,000 MW project at Upper Bhavani is currently under survey and investigation. Of the total potential identified in the state, about 12,300 MW is categorised as on-stream projects and around 9,000 MW as off-stream projects.
According to the roadmap, PSP capacity of 1,00,810 MW is planned to be added to the national grid by 2035-36. This includes the commissioning of the 500 MW Kundah pumped storage project by 2026-27 and the 1,000 MW Upper Bhavani project by 2031-32. At the national level, the Central Electricity Authority has estimated total investment requirements of about Rs 5.8 lakh crore for pumped storage projects up to 2035-36.
Several potential sites in Tamil Nadu and other southern states fall within or near ecologically sensitive stretches of the Western Ghats, making environmental and forest clearances a major bottleneck for project execution.
To address this, the roadmap highlights a series of regulatory interventions proposed by the Ministry of Environment, Forest and Climate Change to rationalise clearance procedures for PSPs, particularly off-stream closed-loop projects. Unlike conventional hydropower schemes, these projects do not dam rivers or alter downstream flows and are designed primarily for energy storage.
Treating off-stream closed-loop PSPs as a distinct category is expected to enable faster statutory approvals because of their relatively lower impact on river ecology, aquatic life and sediment transport.
For states like Tamil Nadu, where favourable topography exists in the Western Ghats but ecological sensitivities are high, this distinction is considered crucial. The report recommends simplified procedures for conducting surveys in forest land, permission for a higher number of exploratory drill holes and clearer guidelines for environmental appraisal. These measures are aimed at reducing the pre-construction gestation period to about 3.5 to 4 years.
Officials involved in power planning have pointed out that PSPs in the Western Ghats are increasingly being conceptualised as off-stream closed-loop systems, with reservoirs located away from perennial rivers and involving limited land submergence. Such an approach is expected to minimise rehabilitation issues and improve public acceptance while meeting the state's growing demand for peak power and grid stability.
The roadmap also links the proposed regulatory relaxations to Tamil Nadu's broader clean energy trajectory. With solar and wind generation often peaking during periods of low demand, pumped storage projects are seen as essential for storing surplus energy and releasing it during evening and nighttime peaks.
Without adequate long-duration storage, the report warns, renewable energy curtailment and dependence on thermal power plants could rise sharply over the next decade.