大象传媒

It鈥檚 known, locally, as Electric Mountain.

Engie鈥檚 hydroelectric station at Dinorwig in North Wales is built deep inside a mountain.

It鈥檚 called into service when the National Grid needs a surge in supply and can generate power within 10 seconds.

As part of the Cool Planet season, 大象传媒 Radio 5 Live went behind the scenes at Europe鈥檚 largest pumped-storage hydroelectric power generator.

Film by Nick Garnett.