A decade-long refurbishment of the Dinorwig and Ffestiniog pumped storage hydro stations is now underway, safeguarding 2.1GW of low-carbon capacity critical to the energy transition and electricity security.
ENGIE, which owns 75% of the plants via the First Hydro Company joint venture with CDPQ, will carry out the work to extend the plants’ lifespan by another 25 years.
Together, they provide 74% of the UK’s pumped hydro capacity and 5% of all installed generation capacity.
Based in North Wales, Dinorwig and Ffestiniog offer rapid-response flexibility to balance the grid when intermittent renewables fall short.
During periods of low demand, the plants pump water to elevated reservoirs, releasing it to generate electricity when needed.
The Dinorwig replanting will involve replacing up to six turbine-generator units and all main inlet valves, a process requiring the station to be drained—a rare, careful procedure not undertaken since its commissioning in 1984.
At Ffestiniog, refurbishment is expected to complete by end of 2025.
“Flexible storage is essential for net zero carbon operation of Britain’s electricity system,” said Miya Paolucci, UK CEO, ENGIE. “We’re very proud to contribute to the electricity security of supply and green energy ambition of the UK with these extraordinary assets.”
Eluned Morgan, First Minister of Wales, added: “Investments such as these create high quality jobs for the local community. ENGIE is a longstanding investor in Wales.”
Energy Secretary Ed Miliband said: “Companies like ENGIE understand that clean energy is the economic opportunity of the 21st century, and are investing in the technologies the UK needs.”
With AI-optimised valves, bespoke lifting systems and local expertise, this programme ensures pumped storage hydro remains at the heart of the UK’s net zero future.
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