A PLANNING application has been submitted for a new underground hydroelectric power station within Ben Cruachan, Argyll’s tallest mountain.

The renewable energy developer behind the scheme, Drax, already has an existing underground power facility at the site known as the “hollow mountain” but will look to upgrade its 600MW capacity to 1.04GW.

The plant would be housed within a new hollowed-out cavern that would be large enough to fit Big Ben on its side. Around two million tonnes of rock will be excavated to create the cavern, tunnels, and other parts of the power station.

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The design would use reversible turbines to pump water from Loch Awe to the upper reservoir on the mountainside to store excess power from wind farms and other low carbon technologies when supply outstrips demand and then use this stored water to generate renewable power when it is needed.

The National: The hollowed out cavern in the mountainThe hollowed out cavern in the mountain

The new power station could be operational as soon as 2030 with construction work getting under way in 2024 in a project that Drax says could support around 900 jobs.

However, the developer says the process of securing consent from the Scottish Government could take around a year.

Ian Kinnaird, Drax’s Scottish Assets Director, said:

“Drax’s plan to expand Cruachan will strengthen the UK’s energy security by enabling more homegrown renewable electricity to come online to power homes and businesses across the country, helping to end our reliance on imports and cut costs.

"This major infrastructure project will support hundreds of jobs and provide a real boost to the Scottish economy. Only by investing in long-duration storage technologies can the UK reach its full renewable potential, and Drax is ready to move mountains to do just that.”

The National: How pumped storage worksHow pumped storage works

Claire Mack, Scottish Renewables Chief Executive, said: “Pumped storage hydro is a critical technology needed to meet net zero. Over the last decade we have managed to develop the technologies to decarbonise the power system such as wind and solar, but what we really need now is greater flexibility to fully optimise those technologies.

"That’s why the success of long-duration storage projects such as Cruachan 2 is absolutely vital to Scotland and the whole of the UK.”