Work could start next year on a £160 million pumped-storage power project at a site in the Snowdonia National Park.

The scheme, proposed by developer Snowdonia Pumped Hydro, was approved in March by business and energy secretary Greg Clark.

The 99MW nationally significant infrastructure project is set to be developed at the abandoned Glyn Ronny and Chwarel Fawr slate quarries near Llanberis in North Wales. Initially the scheme was only planned to have a capacity of 50MW.