BBC News

Inside Electric Mountain in North Wales

Deep inside an old slate quarry near Bangor in North Wales, lies a possible solution to the country's renewable energy problems.

The Dinorwig storage power station - otherwise known as Electric Mountain - is a hydro-electricity plant.

The government's chief scientific adviser thinks the UK may need more of them to bolster the power supplied by wind turbines.

Mike Hickey, manager of the Dinorwig pumped storage plant, explains how it works.