Drax Group’s Cruachan hydroelectric pumped storage plant, built inside a hollowed-out mountain in Scotland, is to undergo an upgrade.

In the £1m (€1.1m) project the station’s current programmable logic controller computer system will be replaced with a new design to improve Cruachan’s efficiency.

ITI (previously Servelec Controls) will undertake the design, installation and commissioning of the upgrade across the station’s four units.

Cruachan can generate power in less than a minute when needed and can also store excess electricity from the grid like a giant battery, a service which was called upon when the low electricity demand during the lockdown coincided with periods of high wind power in Scotland.

The plant’s reversible turbines pump water from Loch Awe to an upper reservoir on the mountainside to store excess power from the grid.

The stored water is then released back through the turbines to generate power quickly and reliably when demand increases.

In July, Cruachan became the first power station in Britain to provide critical system support services to the National Grid as part of a world-first stability contract aimed at reducing the threat of blackouts.

Drax Group hydro head Ian Kinnaird said: “Cruachan plays a critical role in supporting renewable energy in Scotland and stabilising the electricity grid.

“As the country continues to decarbonise, the station’s flexibility has never been more important. This upgrade will ensure the Hollow Mountain can deliver the fast, flexible power that hundreds of thousands of homes and businesses rely on for many decades to come.”

ITI installed the current PLC control systems at Cruachan in 1987 and built the control system which allows the Lanark and Galloway hydro schemes to be remotely managed when needed from a single interface with Cruachan’s underground cavern.