Power to the people: 60 years of Cruachan, Scotland’s hollow mountain and an engineering marvel

Darth Vader might not be your first thought when you gaze up at Cruachan Dam in Argyll and Bute, part of the pumped-storage hydroelectric power station run by renewable energy developer Drax. But it was Cruachan’s iconic buttressed concrete wall holding back the massive reservoir that attracted Disney filmmakers. Its similarity to the legendary villain’s mask made Cruachan the rebel base in the Andor Star Wars prequel, released in 2022.

You can see why the creatives were inspired by the dam and Ben Cruachan, rising 1,126 metres above sea level with its stunning views down over Loch Awe. A kilometre below, meanwhile, inside ‘The Hollow Mountain’, the turbine hall – the beating heart of Cruachan Power Station – houses vast turbines that hum night and day in a giant chamber, keeping the country’s lights on.

Cruachan was also inspirational for Sir Edward MacColl, hydro power pioneer, who saw it as an ideal site for a hydro plant. It was the first of this scale in the world to manage water between the reservoir nestling in the mountain’s corrie and loch below, with the station buried deep in the mountain between.

Sixty years ago Cruachan Power Station was the most impressive engineering feat of its day, an ambitious project involving 4,000 people working at the site to quarry out 220,000 cubic metres of rock and soil. When complete, the Queen officially opened it on 15 October 1965.

One of the tunnels 1km deep inside Ben Cruachan, 'The Hollow Mountain'. | John Devlin

Today it’s no less impressive, powering hundreds of thousands of homes, and still a hive of building activity as the Cruachan upgrade project continues to increase power.

As work continues on an £80 million upgrade and refurbishment project at Cruachan, Plant Manager Steve Scott explains how it works and how vital Cruachan is to the country’s future energy needs.

“We’re like a big battery really,” he says. “We have a big store of water up the hill and release that down towards Loch Awe, and in between is the power station with four turbines, generating 440 megawatts (MW). The work we’re doing over the next three years will see that rise to 480 MW and give us more flexibility to get power out there to the National Grid more quickly.”

Cruachan is already fast and can react to a power surge – a big football game, royal event or soap cliffhanger that sees everyone switching on their telly or kettle – within 30 seconds, and with more flexibility than wind or solar energy.

Plant Manager Steve Scott | John Devlin

“We’re in symbiosis with wind and solar energy,” says Steve. “Scotland is a wonderful place for wind, and solar is coming through, but it’s not always windy or sunny, so when it’s dark and calm, we’re here to generate electricity that people need. “Conversely when electricity is not required we can store power from solar and wind and that can be turned on and off as the market requires.

“Cruachan was the first reversible pumped storage hydro power station of its scale in the world, so absolutely ground-breaking, and it’s still run on the same principles today, whether we’re pumping the water up, generating or releasing water. There’s more cutting edge technology and we can start the machines quicker than in 1965 but largely it’s still the same physics involved. It’s fantastic.

“Back then they didn’t have a great deal of technology, no GPS or laser lining, everything was done by hand, slide rules and genius engineering, and a herculean task was undertaken by the workers. How they did it in six years is amazing.”

As well as being an engineering masterpiece, Cruachan is also a great place to visit.

The Hollow Mountain Visitor Centre, a five star VisitScotland attraction, is well worth a stop on the A85 road to Oban. The centre’s cafe, on the shores of Loch Awe, has some of Scotland’s most scenic views in which to enjoy a scone and perhaps spot a red squirrel or osprey. There are also activities for kids and information and photographs of construction showing how it all works.

The Dam and reservoir sit below Ben Cruachan, above Loch Awe in Argyll. | John Devlin

All of which will whet the appetite for the return of the popular Hollow Mountain Tours. These will be available to the public again when construction of the upgrade is complete and visitors can experience once more the jawdropping visit inside the mountain to see the workings of the power station.

“Everything at Cruachan in terms of hydropower is gargantuan,” explains Sarah Cameron, Scotland Community Manager.

“It’s one of the few places in Scotland where you can pull up and ten minutes later be in an underground sub-tropical paradise world hiding one of the nation’s most important infrastructures,” she says.

Wearing a hard hat and hi-vis jacket, it’s a privilege to get a one-off tour to view the working power station as the upgrade project continues.

Sarah Cameron, Community Manager at Cruachan Power Station. | John Devlin

Leaving daylight behind and passing through an entrance cut into the grassy side of the mountain is like entering Middle Earth. After a five-to-ten minute minibus ride down a kilometre-long tunnel burrowing into the dark granite of Ben Cruachan you’re in the giant turbine hall that feeds power back out to the National Grid, 1,400 feet below the dam. It’s here that the control room is situated and where the majority of the currently 40 strong workforce are toiling away.

Up on the wall of the vast chamber is something you don’t expect in a power station, a massive listed work of art by Elizabeth Falconer. It was commissioned for Cruachan’s opening and depicts the history of the mountain. The mural includes a portrayal of the myth of the Cailleach Bheur, a legendary old woman who was guardian of a spring on the mountain’s peak, mythical precursor of today’s energy source.

One of the turbines inside the machine hall at Cruachan Power Station. | John Devlin

Meanwhile the four massive turbines hum away, fed by four vast pipes channelling water from the reservoir above, and it’s a noisy hive of activity.

It’s all summed up nicely by apprentice Owen Moran, a former Oban High School pupil who has worked at Cruachan for two years now, one of five apprentices on site. “You’re in awe of the engineering that’s in the cavern. It’s a very unusual kind of place and not something everybody gets to see. To be able to work in that on a daily basis is quite something.”

Owen Moran, one of the apprentices at Cruachan Power Station. | John Devlin

With activity ramped up by the upgrade on top of the 24/7 operation, Cruachan’s longest-serving employee with 37 years at the site, Technical Services Co-ordinator Alison Boyce, is also busy planning the 60th anniversary celebrations. Along with a VIP event, commemorative glasses, a gin and whisky collaboration and plans for a Lego version of the dam, there’s also a sense of continuity for the local community and hope for the future.

“Looking at Cruachan the physicality has not really changed a lot, but technology has, and there are great opportunities for people who get to stay in the local community. We’re securing the next 60 years for Cruachan and this place will be here for many decades to come.”

drax.com/Cruachan60