Pumped Storage

Pumped storage hydro-electricity is the oldest kind of large-scale energy storage and works on a very simple principle.

Two reservoirs at different altitudes are required and when the water is released from the upper reservoir, energy is created by the downflow, which is directed through a turbine and generator to create electricity. The water is then pumped back to the upper reservoir.

Pumped storage hydropower provides a dynamic response and offers critical back-up during periods of excess demand. Three of the four existing pumped storage schemes in Wales and Scotland were developed in the 1950’s and 60’s. The last, and largest, at Dinorwig was commissioned in 1984. Their extremely important role in maintaining grid stability and in providing immediate reserve power has proved their worth.

However, the new electricity market mechanisms have proved to be challenging for pumped storage, largely through the absence of reward for capacity, and the increased reliance on short term market volatility (inconsistent with investment timescales for civil projects.) Operators have had to establish new working regimes to ensure continued operation in the short-term, including some mothballing. Their role is likely to become more critical in the future in order to help manage increased intermittency on the GB system.

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