The Planning Inspectorate has received an application from Snowdonia Pumped Hydro Ltd to expand the output of the proposed 600 MWh pumped electricity storage facility at Glyn Rhonwy near Llanberis from 49.9MW to 99.9MW.

Under current planning law installations under 50 MW in output are determined by the relevant local authority, while those with outputs larger than 50 MW are determined by the UK Planning Inspectorate. The development will constitute a Nationally Significant Infrastructure Project (NSIP) under the Planning Act 2008, meaning Snowdonia Pumped Hydro Ltd must apply to the Secretary of State for Energy and Climate Change for a Development Consent Order (DCO).

The scheme to convert two disused slate quarries into a Pumped Storage was granted planning permission by Gwynedd Council in February 2014. Gwynedd Council, along with other local stakeholders that also gave their assent to the original scheme, will be the Planning Inspectorate’s primary consultees.

The Planning Inspectorate now has 28 days to review the application and decide whether or not to accept it - the acceptance decision on the application will be made by Wednesday 18 November 2015.

The planning system treats a pumped storage scheme such as that at Glyn Rhowny in just the same way as a conventional power station – even though the two types of facilities are self-evidently very different.

With construction work due to begin at the site next year, the application to amend the output of the scheme is being made to the UK Planning Inspectorate.

The expansion would be achieved solely by increasing the capacity of the underground turbines and associated equipment. In every other respect the revised facility would remain identical to that originally approved by Gwynedd Council.  While the footprint of the 99.9 MW scheme has increased to allow flexibility in the construction process, the size of all the above ground elements of the scheme will not change.

Pumped storage (or Pumped Hydro) is a way of storing electricity by turning electrical energy into stored (or potential) energy and back again. The system uses electricity to pump water from a lower reservoir to a higher reservoir. Pumping would normally happen during the night, making use of the cheaper electricity cost.

During the day, the water is allowed back through a hydro-turbine to generate electricity again to meet sudden spikes in consumer demand. This cycle of pumping and generating repeats on a daily basis, storing energy when there is substantially less demand on the national electricity grid and releasing it when demand is highest.