Drax Group is expanding the Cruachan Power Station in Argyll, Scotland. Credit: Drax
The power station will have a generating capacity of 600MW. Credit: Drax
The new plant is expected to commence operations in 2030. Credit: Drax

Renewable energy developer Drax Group is spearheading the expansion of the Cruachan power station in Scotland. The proposed £500m ($641.9m) expansion entails the construction of an underground pumped storage hydropower plant adjacent to the existing Cruachan facility.

The expansion, known as Cruachan II, will boost the site’s total generation capacity to 1.04GW. It will also be the first newly constructed plant of its kind in the UK in more than four decades.

The project will help in generating approximately 1,000 jobs during development. It is expected to commence operations in 2030.


The new power station will be situated adjacent to the existing Cruachan hydro-electric pumped storage, west of Dalmally on Loch Awe’s banks in Argyll and Bute, Scotland.

Development background

Drax submitted the planning application for the Cruachan Power Station expansion in May 2022. It secured development approval from the Scottish government in July 2023.

The project is part of Drax’s £7bn ($9bn) strategic investment plan in clean energy technologies, spanning from 2024 to 2030.

Construction works of the proposed project are expected to commence in 2024, which will involve the excavation of approximately two million tonnes of rock from within the Ben Cruachan Mountain to create the cavern, tunnels and other infrastructure of the power station.

Cruachan II details

The expansion project will involve the construction of a new reversible pumped-storage hydroelectric power station with up to 600MW of generating capacity.

Water from an existing upper reservoir on Ben Cruachan will propel the turbines of Cruachan II.

A new intake structure will be constructed within and adjacent to the Cruachan Reservoir. It will include a tower, screens, gates and gate-hoisting equipment to direct water into a new headrace tunnel and underground waterway system.

A new series of underground caverns will be constructed to house the reversible pump turbines and motor-generators together with associated equipment such as transformers and switchgear.

The tailrace tunnel will be a concrete-lined, low-pressure tunnel including a downstream surge shaft to the Loch Awe, which is the lower reservoir. The tailrace tunnel will feature an underground gate chamber and gate shaft on the upstream end of the lower control works.

The lower control works will comprise a screened inlet/outlet structure and stop logs on the Loch Awe, below the water level at the end of the tailrace tunnel.

The underground power plant will be accessed through a 1,450m-long, main access tunnel, which will cross-connect to the existing Cruachan power plant to allow for easy transit between the two plants.

The existing substation compound at Cruachan will be extended to accommodate two new 275kV circuit breakers and associated disconnectors. Each circuit breaker will be T-connected onto the existing 275kV overhead lines, which will enable connecting the new plant to the existing 275kV circuit connecting the site to the Dalmally sub-station, which is located approximately 7km to the east.

Cruachan power station details

The Cruachan power station, also known as the Hollow Mountain, is located within the Ben Cruachan Mountain in Argyll and Bute, Scotland.

Drax acquired the property in December 2018 through its purchase of the Lanark Hydro Scheme in a £702m ($809.3m) power deal. It is one of only four pumped hydropower generation stations in the UK.

The station can produce 440MW of power, sufficient to power 90,000 homes. The reservoir has a catchment area of 23km²  and can store up to ten million cubic metres of water.

Contractors involved

Stantec, a sustainable design and engineering services provider, was responsible for the concept design and technical, environmental, planning and consenting works as part of the project application process.

Studio Pietrangeli, a hydro-engineering consultancy, was appointed as the owner’s engineer for the project and will be responsible for the detailed design and layout optimisation of the new plant, including civil engineering works.

Engineering consultancy COWI will collaborate with Studio Pietrangeli to provide consultancy services to support works in advance of the front-end engineering design.