Portuguese researchers study underground rock storage for renewable energy

Researchers from NOVA University Lisbon's GeoBioTec and the University of Lisbon's Instituto Dom Luiz published a study in the journal Geoenergy on compressed-air energy storage in porous rock formations (CAES-PM). The technology stores excess renewable electricity by compressing air into deep geological reservoirs, later releasing it to drive turbines. The study, described as the first to combine geological and thermodynamic criteria systematically, found reservoirs could store around 1 terawatt-hour, enough for hundreds of thousands of homes. The authors cite the April 2025 Iberian blackout as context and propose a methodology for identifying suitable underground reservoirs.