Britain's largest natural battery reaches major development milestone

Exploratory Works at Coire Glas

Britain’s largest natural battery project has reached a significant milestone, with developer SSE completing a £100m exploratory works programme which saw it drill and blast a 1.2km tunnel into the hillside in the Scottish Highlands.

SSE’s Coire Glas project in the Scottish Highlands would be the first major pumped storage hydro scheme built in more than 40 years.

UK Government confirmed earlier this year a cap and floor investment framework would be introduced to enable the deployment of long-duration electricity storage projects. Meanwhile, the system operator, NESO, has said pumped storage hydro will be critical for energy flexibility as part of the 2030 Clean Power plan.

Robert Bryce, Director of Hydro at SSE Renewables said:

“The decision earlier this year to introduce a cap and floor investment framework was a massive step forward in delivering more of the flexible homegrown energy the UK needs to enable clean power by 2030 and our transition to net zero by 2050.

“Having reached this important milestone in the exploratory works, we are now looking forward to seeing further detail on how the first projects will be taken forward under the scheme, which will be a key enabler of the Government’s Clean Power Plan.”

At 1.3GW with up to 30GWh of storage capacity, Coire Glas could power three million homes for up to 24 hours and would nearly double Great Britain's total current electricity storage capacity, helping the UK to put even more of its homegrown renewable energy to use.

The exploratory works gathered important geological data to inform the main design of the scheme with over 90,000 tonnes of rock and earth excavated.

Coire Glas received planning consent back in 2020 and the project is the largest and most advanced of the more than 10GW of long duration electricity storage projects in the pipeline in the UK.

Robert added:

“We are encouraged to see that NESO has identified pumped storage as critical to both its potential pathways to achieve clean power by 2030. We eagerly await the UK Government’s response to the CP30 Report, which is expected to set out the practical steps Government will now take to make that pathway a reality. In our view this will require accelerated implementation of the cap and floor with a view to enabling final investment decisions at pace on the most advanced and impactful projects.”

Scotland’s unique natural geography provides the ideal environment to deploy pumped storage hydro assets, delivering critical system flexibility by storing low-carbon power in times of surplus to be deployed when the wind doesn’t blow, and sun doesn’t shine.

Coire Glas would be able to ramp to its full generating capacity in under 60 seconds to rapidly support grid stability and start generating in under 10 seconds.

As it is predominantly a civil engineering project, most of the capex cost would be expected to be spent domestically - a major boost for the UK economy and local supply chains.

With an appropriate designed cap and floor regime in place and swift action to progress the first projects, SSE believes Coire Glas could be delivering flexibility to the system in the early 2030s.

The project has also supported more than £160k of community and educational initiatives to date, with the project providing almost circa 30per cent local employment and if it goes ahead a multi-million-pound community benefit fund will be open to the region.

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Milestone for SSE’s Coire Glas as exploratory tunnel now complete