Underground compressed-air storage could power towns and aid Europe's green transition

Researchers led by Ricardo Pereira examined how surplus wind and solar power could be stored underground by compressing air into deep porous rock layers. Simulations indicate that, under optimal conditions, a single reservoir could store as much as 1 TWh of energy, enough to power a medium-sized city for a year. The process displaces non-potable brine without contaminating water supplies and releases energy on demand by expanding the air to drive turbines, providing fast “black start” response for grid emergencies.

Europe’s target of 200 GW of storage by 2030 leaves a large gap that this method could help fill, especially as a low-cost alternative to green hydrogen. However, Portugal’s regulatory framework does not yet recognize such installations, creating a barrier despite the technology’s technical feasibility. Ongoing work aims to map suitable sites, particularly around Lisbon, Almada and the Lusitanian Basin.