Pumped Storage is one of the most important generation types in the UK. Not to be confused with ‘regular’ hydro stations where water runs downstream, either having been stored in a reservoir or without a reservoir – pumped storage sites have the ability to pump water back into the reservoir, providing it with a way of controlling and storing potential energy for considerable periods of time (hours, days or weeks depending on use!)
There are four Pumped Storage sites in the UK with a combined capacity of 2900MW: Dinorwig (1800MW) and Ffestiniog (360MW), both located in Wales and both owned by First Hydro Company (Engie); Cruachan (440MW), located in Scotland and owned by Drax; and Foyers (300MW), located in Scotland and owned by SSE. Dinorwig was the last pumped storage site to be built in the UK back in 1984. While extremely valuable sites, they are expensive to build due to the significant level of construction required. With large-scale batteries becoming increasingly popular and cost effective, it is possible that we may not see any new pumped storage sites built in the UK.
Interestingly, the pumped storage sites historically appeared to have differing strategies for utilising their plant. Dinorwig dominated the Frequency Response service to National Grid; Ffestiniog secured multiple Fast Reserve contracts; Cruachan won a mixture of both Frequency Response and Fast Reserve contracts; while Foyers was utilised consistently in the Balancing Mechanism. This pattern has changed in recent years given the increasing competition in both Frequency Response and Fast Reserve services from batteries and aggregated units made up of a number of smaller plant or demand side response units. The pumped storage sites have began to respond to the changing market: Drax recently secured a 6-year contract with National Grid for Cruachan to provide other system services (such as inertia and reactive power).