The plants would be able to produce in excess of 1,000 gigawatt-hours (GWh) of electricity in a typical year. The last pumped storage scheme to be developed in Great Britain was the Dinorwig scheme in Wales, where work began in 1974.
The energy company announced the plans at the recent official opening of the UK's first large-scale conventional hydroelectric station in 50 years in Glendoe, near Loch Ness. Ian Marchant, CEO of SSE, said: "Our goal is to maintain a diversified portfolio of power stations, with the flexibility to respond to customer demand for electricity while achieving a 50% reduction in the carbon-dioxide intensity of electricity produced. Pumped storage can help us achieve this goal and, after 30 years, I believe is a technology whose time can come again.
Pumped storage schemes involve two bodies of water that are situated at different heights. During periods of low power demand, electricity is used to pump water from the lower loch to the upper reservoir. The water in this upper reservoir is then released to create power when demand is high. SSE claimed that pumped storage schemes complement the growing but variable amount of electricity produced by many renewable energy schemes, particularly windfarms.
In the case of both proposed schemes, the upper reservoirs would be large, enabling electricity generation to continue for longer periods without the need to pump water from the loch below, as is the case for other pumped storage schemes in the UK. Both schemes will require the construction of a dam in order to impound water and create the upper reservoirs, but SSE said that water-pumping and electricity-generation will be carried out underground to avoid any negative visual impact on the scenic Great Glen region.
SSE already owns and operates a 300-MW pumped storage scheme in Foyers, on the south side of Loch Ness, which produces 300 GWh of electricity annually. The company also recently announced plans to apply for consent to develop a 60-MW pumped storage scheme at its existing Sloy hydroelectric power station at Loch Lomond. This would allow it to produce an additional 100 GWh of electricity a year.