First new UK pumped hydro scheme for 30 years given go-ahead

Developer Snowdonia Pumped Hydro (SPH) has been given the go-ahead by the UK government to turn two abandoned slate quarries at Glyn Rhonwy near Llanberis in North Wales into water reservoirs that will store some 700MWh of electricity—sufficient to supply 200,000 homes with electricity for seven hours a day over a projected operational lifetime of 125 years or more.

The £160m facility will use surplus electricity, for example from wind and solar sources, to pump water through an underground tunnel from the lower to the upper reservoir.

When lack of wind or sunshine reduces renewable power output, or when fossil fuel generators fail to start, the water will flow back down the tunnel, spinning a turbine in an underground chamber to regenerate the stored electricity at a power output of 99.9MW.

The only visible evidence of the pumped hydro storage facility will be a modest building on an industrial park, and two reservoirs contained by slate dams blending with existing slate tips, whose water levels silently rise and fall each day.