The preparation of a 10-year project of refurbishment at ENGIE’s Dinorwig pumped storage station has begun, following an 8-year refurbishment at Ffestiniog, enabling the delivery of clean energy whenever needed.
These flexible generation assets, based in North Wales, are essential to the UK Government’s accelerated target of achieving a net zero carbon power grid by 2030. Together they help keep the national electricity system balanced, offering instant system flexibility at short notice. The plants are reaching the end of life and replanting will ensure clean energy can continue to flow into the next few decades.
Re-planting could see the complete refurbishment of up to all six generating units at Dinorwig – a final investment decision is still to be made on the number of units to replace – while the re-planting at Ffestiniog will be completed at the end of 2025. The program also involves the replacement of main inlet valves – with full drain down of the stations – and detailed inspections of the water shafts.
Due to the complexity and the scale of engineering involved, and the necessity to keep the plant as available as possible to serve the electricity system, the re-planting project for Dinorwig will take up to ten years, involving specialist technology, bespoke lifting systems, and expert contractors.
Before the main inlet valves can be replaced – preparation which will be completed in 2025 – the plant must be drained down, a slow and careful process that takes two weeks due to the high water pressure levels. The drainage is a rare procedure, typically carried out every 40 years. During this time, engineers will climb inside the water shafts, carrying out a thorough safety and integrity inspection.