IN Brief:
- Two 315MW pumped-storage units at Dinorwig will be replaced.
- The scope includes turbines, motor-generators, controls, protection, and electrical supplies.
- Wider modernisation is intended to extend the station’s life by at least 25 years.
GE Vernova has been selected to replace the first two 315MW pumped-storage generating units at Dinorwig Power Station in North Wales, beginning a major modernisation of one of Great Britain’s largest flexibility assets.
Awarded by First Hydro Company, which is owned 75% by ENGIE and 25% by La Caisse, the contract covers equipment intended to improve reliability, availability, and efficiency. Completion of the first two replacements is planned by the end of the decade.
GE Vernova’s scope includes reversible pump-turbines, motor-generators, embedded turbine components, control systems, protection, and low-voltage, medium-voltage, and direct-current electrical supplies. Major elements will be manufactured and engineered across several European locations.
Spiral cases, stay rings, and draft-tube components embedded within the civil structure form part of the replacement package, alongside variable-frequency-drive equipment from Germany, protection systems from Spain, and shaft components from Switzerland.
Dinorwig has six generating units and has operated for more than 40 years. From standby, the station can provide up to 1,320MW within approximately 12 seconds and reach its full 1,800MW output within a minute.
Modernising a strategic system asset
As the first stage of a wider programme covering all six machines and associated infrastructure, the two replacements will establish the engineering and outage model for later units. The full modernisation is expected to extend the station’s operating life by at least 25 years.
Pumped storage provides more than energy shifting because its large rotating machines can deliver rapid active-power response, reserve, reactive-power capability, voltage support, and system inertia, depending on the operating mode and plant configuration.
Those services become increasingly valuable when wind and solar output changes quickly or a large generator, transmission circuit, or interconnector trips. Unlike many shorter-duration battery systems, Dinorwig can sustain high output while also contributing the electromechanical characteristics associated with synchronous machinery.
Modernisation must be carefully phased because removing a 315MW unit from service reduces available station capacity during the outage. Work inside an existing underground facility also introduces access, lifting, alignment, ventilation, and interface constraints that are absent from a new-build project.
Existing civil structures will need detailed surveys before replacement machinery is installed, while new components must match interfaces created several decades ago. Manufacturing tolerances, embedded steelwork, shaft alignment, and hydraulic performance all have to be reconciled with the retained station fabric.
Storage capacity becomes more diverse
Testing will progress from individual components through complete unit commissioning, covering protection settings, control sequences, pumping, generating, mode transitions, vibration, thermal behaviour, and interaction with station systems.
Dinorwig and Ffestiniog together provide around 2.1GW, representing approximately three-quarters of Great Britain’s existing pumped-storage capacity. Battery deployment is expanding rapidly, but most current projects have shorter durations and different operating characteristics.
Compressed-air development is advancing alongside those technologies, with EnergyPathways progressing a longer-duration storage scheme intended to shift larger quantities of electricity over extended periods.
Retaining established pumped-storage capacity reduces the risk that ageing assets retire before alternative technologies are deployed at sufficient scale. Dinorwig’s reservoirs, tunnels, caverns, and grid connection represent a substantial civil investment that can be preserved through machinery replacement.
The programme also relies on specialist European manufacturing capability for large rotating electrical machines. Motor-generators and pump-turbines require heavy fabrication, precision machining, insulation systems, hydraulic testing, and long-term service expertise that cannot be recreated quickly if supply chains contract.
Control and protection upgrades will be equally significant because the operating environment has changed considerably since the station entered service. Faster markets, converter-connected generation, interconnector flows, and more granular dispatch require legacy mechanical assets to operate within modern digital control architectures.
Successful completion of the first two units will preserve 630MW of rapid-response capacity and create a repeatable route for the remaining four machines. The programme will determine how effectively Dinorwig continues to support system operation into the middle of the century.
