A hydro battery is comprised of two large bodies of water at different heights – in this instance, they are located nearly 2,000 feet below ground between the Emosson and Vieux Emosson dams in Valais.
https://www.techspot.com/news/95219-swiss-water-battery-20-million-kwh-capacity-finally.html?utm_source=dlvr.it&utm_medium=blogger
https://www.techspot.com/news/95219-swiss-water-battery-20-million-kwh-capacity-finally.html?utm_source=dlvr.it&utm_medium=blogger