SSE has reached a major milestone on its Coire Glas pumped storage hydropower scheme with the completion of exploratory tunnelling in the Scottish Highlands.
The 1.3 GW Coire Glas project is set to be the first large-scale pumped storage scheme developed in the UK in 40 years.
The Scottish government gave its approval to the project, situated in the Great Glen near Loch Lochy, in 2020.
Once complete, the scheme will provide 30 GWh of long duration electricity storage, enough to power around three million British homes.
Using excess energy from the grid, SSE will pump water 500 metres uphill from Loch Lochy to an upper reservoir created by the construction of a 90 metre high dam.
© Image: SSEThe reservoir will store enough water to fill 11,000 Olympic-sized swimming pools, which can be released when wind power output is low and electricity demand is high.
Work started on the 1.2km tunnel in 2022, and SSE said it could spend up to £1.5 billion on constructing Coire Glas given “the right market investment framework”.
Approximately five metres high and four and a half metres wide, the tunnel cuts into the hillside around the proposed site of the underground powerhouse complex.
SSE said the construction will help gather accurate information on the geological conditions to inform the detailed design for the main works.
Coire Glas subject to ‘cap and floor’
SSE Renewables said it hopes to make a final investment decision on the project in late 2025 or early 2026.
The decision rests on the firm being successful in the “administrative allocation of an investable cap and floor mechanism”.
The UK government is currently developing the mechanism, which is similar to the Contracts for Differences scheme, to overcome investment barriers in energy storage.
© Supplied by SSEAlongside pumped hydro, other eligible technologies include flow batteries, compressed air and liquid air energy storage systems.
If the project gets the go ahead, SSE said main construction at Coire Glas could start in the second half of 2026.
SSE Renewables director of development for Coire Glas Mike Seaton said completing the tunnelling is a “positive step forward in de-risking the project”.
“The works progressed to plan, and samples of the materials excavated from within the hillside are currently being analysed,” Seaton said.
“This phase of the project is an engineering challenge in itself and we are learning a huge amount as we progress the works.”
Scottish pumped hydro schemes
There are numerous pumped storage hydro schemes under development in Scotland, which if constructed will more than double current UK capacity.
A recent report commissioned by Scottish Renewables estimated that six of these schemes could create almost 15,000 jobs and generate up to £5.8 billion for the UK economy by 2035.
In addition to Coire Glas, major schemes under development in Scotland include the Cruachan II expansion in Argyll and the Glen Earrach project near Loch Ness.
SSE is also developing the Loch Fearna project in a joint venture with Gilkes Energy.
