Subsurface rock formations used as energy storage batteries

Researchers are exploring the use of subsurface rock formations as massive batteries to support the transition to renewable energy. This technology, which has roots dating back to salt cavern experiments in Germany during the 1970s, aims to solve the problem of storing surplus electricity generated by intermittent sources like wind and solar.

In the case of porous rocks, excess electricity powers compressors that push air into deep underground layers, typically at depths of 500 to 2,000 meters. This air displaces non-potable saltwater within the rock grains without causing contamination. The compressed air remains trapped under pressure until needed. When electricity demand rises, the air is released through a well, where its expansion drives surface turbines to generate power without burning fuel.

Ricardo Pereira, a researcher at the Faculdade de Ciências e Tecnologia of the Universidade NOVA de Lisboa, notes that this method could potentially store enough energy to power small cities. Currently, Europe has a storage capacity of approximately 55 gigawatts, with a target to reach 200 gigawatts by 2030 to alleviate grid constraints.