The Anonymous Widower

Drax Submits Application To Expand Iconic ‘Hollow Mountain’ Power Station

The title of this post, is the same as that of this press release from Drax.

The project is called Cruachan 2 and is described on this web site.

This is the introduction to the project.

We have kickstarted the planning process to build a new underground pumped hydro storage power station – more than doubling the electricity generating capacity at Cruachan.

The 600 megawatt (MW) power station will be located inside Ben Cruachan – Argyll’s highest mountain – and increase the site’s total capacity to 1 gigawatt (GW).

The new power station would be built within a new, hollowed-out cavern which would be large enough to fit Big Ben on its side, to the east of Drax’s existing 440MW pumped storage hydro station. More than a million tonnes of rock would be excavated to create the cavern and other parts of the power station. The existing upper reservoir, which can hold 2.4 billion gallons of water, has the capacity to serve both power stations.


  1. The generation capacity will be increased from 440 MW to 1040 MW, which is an increase of 36 %.
  2. Cruachan has a storage capacity of 7.1 GWh, which will not be increased.
  3. Cruachan opened in October 1965, so the generating equipment is nearly sixty years old.

I will assume that Drax and its various previous owners have kept the turbines, generators, dam and associated pipework in good condition, but as an Electrical Engineer, I do believe that the modern equipment, that will be used in Cruachan 2 will offer advantages.

  • One of these advantages could be the ability to ramp up power faster, than the original equipment.
  • I also suspect, it will have a sophisticated computer control system, that will allow the output of the power station to be precisely controlled.

These two features should mean that when a spike in power demand happens, that the combined Cruachan will step up to the plate.

So all those watching the Celtic and Rangers match on television, will still get their half-time cuppa.

I suspect that the combined Cruachan will be a power regulator of the highest quality.

Will The Storage Capacity Of Drax Be Increased?

Drax don’t appear to have any plans for increasing the size of the upper reservoir and I suspect that geography can’t deliver an affordable solution.


  • Loch Awe is an excellent lower reservoir for a pumped storage system.
  • The building of Cruachan 2 may create substantial employment and economic benefits in the area.
  • Cruachan 2 is not the only pumped storage scheme under development in the area.
  • The UK needs as much pumped energy storage as can be created.

I wouldn’t be surprised to see, further development of Cruachan, if Cruachan 2 is an overwhelming success.

It’ll all be down to the geography and the economics.


May 17, 2022 - Posted by | Energy, Energy Storage | , ,

1 Comment »

  1. Started reading it and thought just get on with it but then saw its not expanding the storage capacity and decided whats the point of it then you might as well retrofit the existing turbine hall and install modern kit. The UK desperately needs more high capacity storage and im mean >5GWh installations not piddling 50MWh 1 hour batteries which are just a way for financial people to make easy money without dealing with the underlying problem

    Comment by Nicholas Lewis | May 17, 2022 | Reply

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