Glyn Rhonwy

The Glyn Rhonwy Pumped Hydro project is a new-build pumped hydroelectric energy storage scheme situated in Llanberis, North Wales, UK.

The project seeks to utilise abandoned slate quarries for use as reservoirs for the pumped hydro facility. Much of the development would be sited underground, with an tunnelled penstock connecting the two reservoirs via an underground turbine house.

The scheme would be filled initially using water from Llyn Padarn, then becoming largely off-stream with minimal interaction with adjacent watercourses. The development will be connected to the grid via an underground cable to Pentir substation.


Key figures

  • 99.9 Megawatts of power
  • 700 Megawatt Hours storage capacity
  • Volume 1.3 Million Cubic Metres at 250 metres of head.
  • 2 reversible turbines
  • Start to full power in 12 seconds
  • Cycle efficiency of around 81%
  • Project lifespan of 125 years
  • Estimated carbon saving of 50,000 tonnes per year

About us

Snowdonia Pumped Hydro is a daughter company of Quarry Battery Company, and was set up to develop the Glyn Rhonwy project exclusively. Quarry Battery Company is a developer of flexible generation technologies for operation in the UK balancing services market. 

You can read more about Quarry Battery Company on our website.