Pumped Storage Hydropower (PSH) potential:
The report maps high‑potential closed‑loop pumped storage across Tamil Nadu using a three‑stage filter, theoretical, technical, and sustainable potential, integrating Digital Elevation Model (DEM) -based reservoir detection with a 14‑parameter environmental impact assessment to prioritise low-impact sites. Closed‑loop designs use two isolated reservoirs, reducing river dependence and permitting risk while supplying long-duration storage to facilitate the transition towards a renewable energy grid.
The study estimates 1,32,386 GWh of storage potential from 572 non-overlapping reservoir pairs, with over 60% of the potential energy capacity concentrated in a small number of ≥500 GWh sites and 33.5% from the 150 GWh class; ≤50 GWh sites together contribute under 6%. Clusters align with the districts of Nilgiris, Coimbatore, Erode, Dindigul, Theni, which have the hill ranges, while plains and coastal districts have negligible potential due to flat terrain and limited natural basins.
Siting criteria
Sites are selected using technical filters that look for an elevation difference (“head”) between the reservoirs of 200 to 750 meters, a distance between reservoirs that doesn’t exceed 12 times that height, and a reservoir pairing radius of roughly 2.2 to 8.25 kilometers. The reservoirs need to be closely matched in storage volume (at least 90% similarity), and any proposed dam should be higher than 100 meters to ensure sufficient capacity and efficiency.
After these basic engineering checks, each option is scored for sustainable potential using an Environmental Impact Assessment (EIA) that covers land use, water resources, impacts on communities, environmental conditions, infrastructure access, and protections for cultural sites and biodiversity. Sites are then rated from 0–14, guiding planners to low-impact reservoir combinations for development.
Environmental signals
About 75% of reservoirs show a scoring of EIA 5–7 (moderate), with lower reservoirs often scoring slightly higher due to proximity to settlements, croplands, and infrastructure, indicating manageable but non‑trivial siting trade-offs. Outliers exist at both ends, reinforcing the value of early GIS screening to avoid high-impact zones and focus on degraded or previously altered landscapes.
Policy and risks
Streamlined DPR concurrence can shorten parts of the approval path, but commissioning still depends on site‑specific EIA outcomes, land processes, access, and geotechnical conditions, underscoring the value of early screening and low‑impact siting embedded in this results map. This would also boost bankability.
Conclusion
Placing renewable energy generators like wind and solar plants near pumped storage hydropower facilities allows renewable energy to be stored efficiently when production is high and released when needed. This co-location makes the electricity supply more stable, helps reduce curtailment, and increases the value and reliability of variable renewable sources. Mapping these co-location opportunities, as done in this study, helps identify the best sites where pumped storage and renewable energy hubs can be developed together for maximum benefit to the grid and the environment.
