Is this a beautiful Scottish loch or a giant power battery?

Hydro potential
Assynt loch © Russell Bruce

By Russell Bruce

In fact it could be both. The challenge of our times is to keep the windfarms churning and not close them down when the grid does not need the power. There are two reasons to capture all the power we can from wind generation. One is to convert to green hydrogen with the ability to also store it until required. The other is pumped hydro and that is where many of Scotland’s lochs come in. Our rugged, hilly and mountain landscape captures water in lochs at different levels.

Scotland has long produced hydro power since the establishment in 1943 of the North of Scotland Hydro-Electric Board which we covered in our Power Scotland series – Power from the Glens. Scotland produces close to 20% of our renewable energy from Hydro and the expansion of wind power capacity, on and offshore, provides the potential to increase this significantly.

Scotland with 90% of the UK’s freshwater resources and many of our lochs situated at different levels which could enable flows to hydro turbines without always requiring the construction of large dams. At the touch of a switch water can cascade down the pipes that connect the loch reservoir to the turbines below. Water falls naturally as everyone can note from recent weather. Water is heavy, hence its value as a power source and the reason many lochs may be suitable to act as giant batteries to provide power when required. There is no time limit on how long the battery power of higher level water will last, unlike electric battery storage which is short term but does have a part to play, despite requiring consumption of rare earth resources.

Largest ever pumped hydro plant in Scotland to power 3 million homes

Work is getting underway to prepare for SSE’s Coire Glas pumped hydro station with construction expected to begin in April 2024. Located north of Fort William the power plant would use Loch Lochy as a large lower reservoir with surplus wind generation used to feed the upper reservoir at a height of 500 metres.

Scotland’s Coire Glas project will be the first large-scale pumped storage scheme to be developed in the UK for more than three decades and is planned to deliver 1500MW which SSE claim would more than double Britain’s existing storage capacity.

Map image from Open Street Maps Creative Commons Licence (CC BY-SA 2.0)

Not many streets on the map but it does display Scotland’s extraordinary water resources in this part of the Highlands. Globally water is in short supply. Given the topography of Scotland’s natural landscape and our prevailing weather conditions the sky will augment pumped hydro at times.

A collaboration between Scottish energy company SSE, design services group Stantec and engineering, economics and environmental science consultancy COWI, Coire Glas is intended to provide fast response to meet grid demand and be able to do so for days at a time, when required. At full capacity is would come close to Dinorwig Power Station in Snowdonia National Park, locally refered to as ‘Electric Mountain.’

SSE have produced a short video which can be accessed from the website

Cruachan Power Station

Cruachan, often referred to as ‘The Hollow Mountain’ is an existing pumped hydro plant dear Dalmally in Argyll. Opened in 1965 it was operated by the North of Scotland Hydro-Electric Board and later transfered to the South of Scotland Electricity Board, then Scottish Power after privatisation. In 2019 Drax, of smokey chimney fame, bought it from Scottish Power along with a number of other smaller Scottish hydro power plants.

Cruachan upper reservoir Photograph James Hearton, CC BY-SA 2.0, Creative Commons /w/index.php?curid=92858


Drax has begun the process to develop an new underground pumped hydro power station to add to the existing capacity. Drax needs to secure consent under Section 36 of the Electricity Act 1989 from Scottish Ministers.

Energy company Drax Group said it is kickstarting the planning process to build a new underground pumped hydro storage power station that will more than double the electricity generating capacity at its iconic Cruachan facility in Scotland. The project was announced in June ahead of COP26 climate conference in Glasgow. Drax said Cruachan2 “will support almost 900 jobs in rural areas across Scotland during construction and will provide the storage capacity needed to support a net zero power system.”

The 600MW power station will be located inside Ben Cruachan to the east of Drax’s existing 440MW pumped storage hydro station increasing the site’s total capacity to 1040MW. The existing upper reservoir (photograph above) has the capacity to supply both Cruachan power stations.

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