The £500m expansion project, known as Cruachan 2, will be built within a new cavern, to the east of Drax’s existing 440MW pumped storage hydro station beneath Ben Cruachan. The project will bring an additional 600MW of power – increasing the site's total capacity to over 1GW.

Working with the owner’s engineer, Italian civil engineering company Studio Pietrangeli, Cowi will advise on the geotechnical, tunnelling and jetty / marine structures in advance of the Front-End Engineering Design (FEED). Cowi will also use its rail experience to provide input on the railway line beneath which Cruachan 2’s new access and tailrace tunnels will run.

Work on Cruachan 2 is expected to start in 2025 and the new plant will be connected to the national grid by 2030.

Cowi UK managing director Andy Sloan said Scotland was undergoing a hydro-pumped storage renaissance.

“There’s a profound opportunity for hydroelectric developments in the UK, particularly in Scotland, which will not only address our need for long-term storage in the UK energy market but support our journey to net-zero by 2045,” he said.

Drax development manager Steve Marshall pumped storage hydro plants played a critical role in stabilising the electricity system, helping to balance supply and demand through storing excess power from the national grid.

“When Scotland’s wind turbines are generating more power than we need, Cruachan steps in to store the renewable electricity so it doesn’t go to waste. With the right support from the UK government, Drax is ready to invest around £500m to more than double Cruachan’s generating capacity,” he said.