The Coir Glas Pumped Hydro Storage Project will be located in Scottish Highlands, the UK. (Credit: SSE)
The project would be the first pumped hydro storage scheme to be built in the UK in 40 years. (Credit: SSE)
Indicative design of the project. (Credit: SSE)

The Coir Glas Pumped Hydro Storage Project is proposed to be developed in the Scottish Highlands of the UK.

The project, owned by SSE Renewables, would be the first pumped hydro storage scheme to be built in the UK in 40 years.

Initially, the proposed capacity of Coir Glas was 600MW. In October 2020, the Scottish Government approved a revised application to increase the scheme’s capacity up to 1,500MW.

The development of the hydro storage project will entail a capital investment of more than £1.5bn.

Exploratory works for the pumped hydro storage project began in December 2022.

In March 2023, SSE Renewables announced an investment of £100m for the project. Around half of this investment will be spent on pre-construction phase including site investigation works.

SSE Renewables is expected to make a final investment decision on the project in 2024. The decision is subject to satisfactory progress in development works and policy environment in the country.

According to the planned timeline, Coir Glas is expected to be fully commissioned by 2031.

Once operational, it will have an energy storage capability of 30GWh, and meet power requirements for 3 million UK homes for a day.

Location of Coir Glas Project

The Coir Glas Pumped Hydro Storage Project will be located on the shores of Loch Lochy between Fort William and Inverness in Great Glen of Scotland.

Coir Glas Pumped Hydro Storage Project Details

The Coir Glas Pumped Hydro Storage Project will consist of two reservoirs at different elevations- a large lower reservoir at Loch Lochy and a new upper reservoir.

The new upper reservoir, up to 700m wide, will be located in a coire, or hollow, more than 500m above the Loch Lochy.

A new dam of up to 92m in height will be constructed for the upper reservoir to store up to 26 billion litres of water. This is equal to 11,000 Olympic sized swimming pools.

Coir Glas will have a hidden power station situated around 1km inside the mountain and buried under centuries’ old rock.

The power station will consist of four pumped hydro storage turbines, each with a rating of 324MW, and a series of tunnels. This will provide the project with a total capacity of 1,296MW.

The station will work continuously for 24 hours at full output and will use surplus renewable power from the grid to pump water 500m above the top of the mountain from Loch Lochy.

The water, at the top of mountain, will be stored before it is released back via tunnels to generate power at times of low wind output and high customer demand.

The Coir Glas Project will be capable of reaching operational stage within 30 seconds from an operating standby situation.

A project of such scale has an estimated construction time of five to six years, and an operation life of more than 50 years.

Coire Glas Connection details

SSEN Transmission, which is responsible for the electricity transmission network in the north of Scotland, signed the transmission owner agreement to connect the Coire Glas Pumped Hydro Project for December 2027.

Coir Glas will be connected in two phases.

Phase one will include the connection of 612MW Export/ 660MW Demand in December 2027.

Key components for this phase will include a new 400kV external Air Insulated Switching Station (AIS) with two control buildings; a new 400/132kV substation near Loch Lundie which will include a control building, two transformers, and outdoor AIS equipment; and a new 400kV overhead line of approximately 3.5km length which will connect project substation to Loch Lundie substation.

Additionally, an 8.5km-long 400kV overhead line will connect the Loch Lundie substation to the existing Fort Augustus substation at Auchterawe.

The second phase will include the connection of an additional 684MW Export/ 700MW Demand and it will be connected in October 2029. This phase will involve upgrading the Beauly-Denny overhead line second circuit to 400kV operation and building the Eastern HVDC Peterhead – Drax Link.

Contractors Involved

Fugro, a Dutch multinational service company, received a ground investigation contract for the Coir Glas Project from SSE Renewables in March 2023.

ASH Design + Assessment Limited was selected by SSE Renewables to undertake Environmental Impact Assessment (EIA) and deliver Environmental Statement (ES) for the project. ASH also prepared a scoping report for the project in May 2017.

In May 2023, CEMEX UK, a building material company, started the supply of Silo Sprayed Concrete to Coire Glas.

STRABAG UK, a construction service provider company, uses specialised all-terrain vehicles and helicopters for site assessment and equipment transport.

STRABAG UK was also selected by SSE to undertake exploratory works for the pumped storage scheme in April 2022.

Cowi, an engineering and architecture consultancy company, was hired to prepare geotechnical baseline report, geotechnical ground investigations, exploratory audit design services, and reference design of the underground structures.

Stantec, an international professional services company in design and consulting, will provide reference designs for engineering, support procurement of the construction contractor (dam included), and complete Section 36 environmental permitting for construction.

In February 2022, the Invitation to Tender (ITT) for the main construction works of Coire Glas was issued. The process is slated to run until late 2023.

SSE Renewables commissioned Imperial College London for a research that indicated a project such as Coir Glas can save up to £690m per year by 2050.