Additional capacity of between 400-600MW could be added if the Cruachan pumped storage plant in Scotland was expanded, a feasibility study suggests.

ScottishPower, the operator of the 440MW plant near Oban, recently completed the two-year feasibility study to determine whether it is possible to expand the station.

The findings show that it would be possible to develop between the additional capacity, with investment of between £300 million to £400 million.

The study shows that a new cavern would need to be excavated within Ben Cruachan, and the possibility that new dams could be constructed to increase the capacity of the upper reservoir.

ScottishPower is now considering all the options, but in a statement it said that any project to expand Cruachan would include:

  • 8-10 year build programme for extension
  • 2-3 years to secure Section 36 planning consent and other necessary consents
  • 6-7 years for construction and commissioning
  • New cavern and potential for new dam
  • 800 workers for the main civil construction works at peak

Given the increasing importance of renewable energy in Scotland, and the increasing need for energy storage, ScottishPower believes that Cruachan is well placed to help support the grid.

"A new generation of pumped storage hydro would be a major asset for electricity systems worldwide as more renewable electricity continues to come on line," said Hugh Finlay, Generation Director at ScottishPower. "Pumped storage hydro is the most cost effective and well-developed large-scale electricity storage technology in existence. We will now take forward our Cruachan findings with government and regulators."

ScottishPower will now consider the next steps for the project, including discussions with government on potential support mechanisms.

Cruachan celebrated its 50th anniversary in October 2015. Her Majesty the Queen presided over the official opening ceremony on 15th October 1965, six years after construction had started.

Widely regarded as an engineering masterpiece, and often referred to as The Hollow Mountain, Cruachan was devised by Sir Edward MacColl and was built by a workforce of 4000. Over 220,000m3 of rock was blasted and drilled by explosives experts know as Tunnel Tigers, to create a cavern 1km inside the mountain to house the turbines and a network of pipes and tunnels.