Energy giant SSE is to progress plans for a new pumped storage hydropower scheme at Loch Fearna in Scotland’s Great Glen.

The proposed project, which SSE is pursuing in a 50:50 joint venture with a consortium led by Gilkes Energy, is located at the western end of Glengarry around 25km west of Invergarry, adjoining SSE Renewables’ existing Loch Quoich reservoir in the Great Glen hydro scheme.

It envisages the development of tunnels and a new power station connecting the reservoir at Loch Quoich with an upper reservoir at Loch Fearna. The proposed scheme would have a generating capacity of up to 1.8 gigawatts (GW) and be capable of producing around 37 gigawatt hours of stored energy capacity. The project has already secured a grid connection offer totalling 1,795 megawatts.

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SSE Renewables said it already operates the largest fleet of hydro-electric power and pumped storage hydro assets in Scotland. It is now progressing development plans for new pumped storage hydropower projects in the Highlands to complement its existing fleet and deliver the large-scale, long-duration electricity storage (LDES) needed as part of Britain’s future energy mix.

Ross Turbet, head of investment management for Hydro, SSE Renewables, said: “As the UK transitions to net zero, the development of additional pumped storage hydro projects will be crucial for energy security and for balancing an increasingly renewables-led energy system during periods when the wind doesn’t blow, and the sun doesn’t shine.

“The proposed Fearna project is a welcome addition to our development pipeline of pumped storage hydro projects, which also includes our proposal to develop what could be one of Britain’s biggest pumped storage schemes in 40 years at Coire Glas and our intention to convert our existing Sloy Power Station into a pumped storage facility.

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“Our vision for the delivery of pumped energy storage solutions for a net-zero Britain demonstrates SSE Renewables’ ongoing commitment to optimising the value of our existing hydro assets while investing in new hydro projects as part of our wider renewable portfolio.”

SSE noted that a request for a scoping opinion for the project is currently before Scottish Government ministers, adding that consultation has already begun with local communities and organisations. If consented for development, the project could begin commercial operations in the mid-2030s, subject to reaching a final investment decision. Fearna could be one of the largest pumped storage hydro projects in the UK.

Carl Crompton, managing director of Gilkes Energy, said: “We are delighted to launch, in partnership with SSE Renewables, the Fearna pumped storage project.

“Energy storage allows energy produced during times of excess generation (mainly wind) to be stored and released later when there is a deficit of renewable energy. Pumped storage hydro projects are in effect very large water batteries and the technology behind these projects is very mature and robust. PSH projects can easily last for 100-plus years with no degradation in performance.

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“The recent publication of the Government consultation on long duration electricity storage (LDES) support, likely to be a cap and floor mechanism, is also a significant step forward. This consultation recognises both the value of pumped storage hydro, but also the challenge of financing such capital intensive and long lead time projects.

“The proposed cap and floor mechanism has been used successfully to bring multiple interconnector projects to fruition, and we hope a similar mechanism will unlock the financing of a number of PSH projects. We look forward to bringing this pioneering project to fruition.”

Pumped storage hydro works by using two reservoirs of water at different elevations over a short distance. This generates power as water moves down from one reservoir to the other, passing through turbines. Water is pumped back into the upper reservoir at times of excess renewable energy generation, allowing excess renewable power to be captured and stored, like a giant natural battery.