India Coal Belt Could Support Long Duration Batteries

India’s renewable energy planners and power system strategists are eyeing an unconventional large‑scale storage idea that could reshape the nation’s electricity grid, particularly in coal‑belt regions. International research shows that hundreds of thousands of abandoned underground coal mines could potentially be repurposed into gravity‑based energy storage systems — giant mechanical “batteries” that harness gravity and dense materials to store electricity generated from wind and solar farms. If realised at scale, this approach could help India balance intermittent renewable output while offering a climate‑aligned reuse path for legacy industrial sites. 

The concept builds on the physics of gravitational potential energy: surplus energy from renewables is used to lift heavy material such as sand or water deep within an unused mine shaft, storing energy in the height position. When electricity demand spikes, the mass is allowed to descend, driving generators to produce power. This method is distinct from chemical batteries and more akin to pumped‑storage hydroelectricity, the world’s dominant form of grid energy storage, except it leverages existing vertical shafts. Researchers modelling this idea have estimated a global storage potential of up to 70 terawatt‑hours (TWh) — a quantity large enough to support long‑duration energy balancing across major power systems. Most of this potential is geographically concentrated in countries with extensive coal mining legacies, including China, India and the United States. For India’s urban transition, where state and national targets aim to increase renewable capacity rapidly, practical energy storage solutions are becoming critical. Intermittency from solar generation, which can peak midday and drop at night, creates operational challenges for grid operators who must maintain stable supply to cities and industries. Large‑scale storage that can bridge these gaps is essential for cost‑effective and zero‑carbon power systems. 

Industry experts caution, however, that gravity storage is not yet mainstream. Unlike conventional pumped hydro, which uses large water reservoirs in hilly terrain, underground gravity storage in vertical mine shafts is still at the research and early demonstration stage. The technology’s economic viability depends on factors such as shaft depth, structural stability, connection to transmission infrastructure and overall project financing — all of which vary widely across India’s former coal mining heartlands in Jharkhand, Chhattisgarh and Odisha. Moreover, while gravity‑based storage promises much longer energy retention times and lower self‑discharge than lithium‑ion batteries, it must compete with existing storage alternatives — including compressed air and new battery chemistries — each with their own cost and lifecycle footprints. Urban planners and grid architects see opportunity in aligning gravity storage development with just transition goals in coal regions. Retrofitting abandoned mines for energy storage could create new industrial roles, rehabilitate degraded lands, and support equitable economic opportunities in communities historically dependent on extractive industries. Such projects could also reduce transmission bottlenecks by localising storage near demand centres, lowering generation costs for cities while improving climate resilience.

Turning mine closures into energy assets reflects a broader shift toward circular infrastructure — maximising existing industrial stocks to serve climate‑aligned energy needs. If policymakers and private investors can align technical feasibility with financing mechanisms and regulatory clarity, gravity energy storage might become a transformative tool for India’s energy‑urban transition.

Also Read: India Power Sector Urged to Fix Coal Policy Gaps

India Coal Belt Could Support Long Duration Batteries