THE generating capacity of Scotland’s famous “Hollow Mountain” pumped storage hydro station in Argyll is to be ramped up in a move hailed as a major boost to UK energy security.

Energy giant Drax declared it will invest £80 million in a major refurbishment of the Cruachan site, which has been producing hydro power since the 1960s.

Drax said the investment will support UK energy security after it was brought into sharp focus by Russia’s full-scale invasion of Ukraine.

The company noted the project will increase the generating capacity of two of the Cruachan plant’s four units by a combined 40 megawatts, raising the facility’s total generating capacity to 480MW. The units were commissioned in 1965 and contain parts, including turbines, which are now more than 50 years old.

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Drax, which acquired the site from ScottishPower in 2019 as part of a £702m deal for a portfolio of power generation assets, has appointed Andritz, a global hydro-power technology supplier, as the main contractor to the upgrade.

“Pumped storage hydro is vital to the UK’s energy security, it’s a technology which works in partnership with renewables,” said Penny Small, interim chief operating officer at Drax, speaking at the signing of the contract with Andritz in Ravensburg, Germany.

“These plants play a critical role in stabilising the electricity system, helping to balance supply and demand through storing excess power. When wind turbines are generating more power than we need, Cruachan steps in to store the renewable electricity so it doesn’t go to waste.

“By investing in Cruachan today, Drax is ensuring the power station can play an even bigger role in the energy system of tomorrow. We look forward to working with our contracting partners to deliver this exciting project.”

Drax’s Cruachan Power Station is located on the shores of Loch Awe in Argyll and is one of four pumped storage hydro facilities in the UK, playing a “critical” role in the country’s energy security.

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Built in the 1960s in the hollowed-out Ben Cruachan, Drax has noted that the facility works like an enormous rechargeable battery by managing water resources between a reservoir in the Argyll hills and Loch Awe, 396 metres below.

Water is pumped using reversible turbines from Loch Awe to fill the upper reservoir which stores excess power from sources such as wind farms when supply outstrips demand. When demand for electricity rises, the same turbines are used to bring the stored water through the plant to generate power.

Drax noted that the upgrades to two of the plant’s four units will improve their operability and reliability, lengthening their lifespan. It said the investment is underpinned by the award of a 15-year capacity market agreement from the UK Government worth around £221m.

Dominik Fust, managing director at Andritz Hydro Germany, said: “We are proud to have been entrusted with the refurbishment of the Cruachan Pump Storage Power Plant. This project aligns with our mission to contribute to the global transition toward sustainable energy generation.”

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Drax said the Cruachan upgrade project is separate to its plans to build a new 600MW pumped storage power station next to the existing facility.

The company secured development consent from the Scottish Government for the £500m project last July, in what it said was a “major milestone” in its quest to develop the first new plant of its kind in a generation. Consent was provided by ministers through Section 36 of the Electricity Act 1989.

A final investment decision has still to be made on the project, with Drax stating that the development hinges on the UK Government providing an “updated financial stabilisation mechanism”.

The company has noted that the absence of a framework for large-scale, long-duration technologies has meant that no new plants have been constructed in the UK since 1984, despite the key role they can play in decarbonising the energy system.

A study by Scottish Renewables has estimated the project could create and support up to 1,100 jobs.