Dinorwig pumped storage station.
Through their joint venture, First Hydro Company, ENGIE holds a 75% stake, while CDPQ owns 25%. Together, the plants provide 2.1GW of storage capacity, accounting for 74% of the UK’s pumped storage hydro and approximately 5% of its total power generation capacity. Miya Paolucci, UK CEO of ENGIE, stated: “Flexible storage is essential for net zero carbon operation of Britain’s electricity system. It helps balance the system by ensuring there’s always a large volume of ‘back up’ power on standby, that can be delivered in very fast timescales if required.”
The refurbishment program includes a 10-year project at Dinorwig, where up to all six generating units may be replaced, pending a final investment decision. At Ffestiniog, an eight-year overhaul is nearing completion, with two units rebuilt and the remaining two set for completion by the end of 2025. The program also involves replacing main inlet valves at both sites, among the largest globally, designed with AI and scaled laboratory models for enhanced efficiency. Valve replacement requires draining the stations, a two-week process due to high water pressure, occurring once every 40 years.
Dinorwig’s upgrades involve complex engineering, custom lifting systems, and on-site valve seal tuning. Wales’ First Minister, Eluned Morgan, noted: “Investments such as these create high quality jobs for the local community. ENGIE is a longstanding investor in Wales, employing around 200 permanent staff and I’m pleased to support its replanting scheme, which will see the facilities continue to operate for another 25 years.” Ffestiniog, commissioned in 1963, was the UK’s first pumped hydro plant, while Dinorwig, opened in 1984, is Europe’s largest and fastest-acting pumped storage station.
Two of Dinorwig’s six main inlet valves were replaced in 2023, with the remaining four scheduled for 2025. The project supports sustainable energy goals and local economic growth in Wales.
