Coire Glas power station

Topographic map of Coire Glas (left centre) and part of Loch Lochy

Loch Lochy lies along the Great Glen of Scotland, at an altitude of 29m above ordnance datum (AOD).[3][2]

Above its north-western shore, the Munro mountain Sròn a' Choire Ghairbh reaches a height of 937m. The north-east slope of the summit forms the headwall of the Coire Glas, a horseshoe-shaped glacial corrie. The corrie tarn, Loch a’ Choire Ghlais, lies at an altitude over 500m AOD.

Damming the mouth of the Corrie Glas will create the upper reservoir. The crest of the dam will be around 700m long and 92m above ground level at its tallest point. When full, the reservoir will be approximately 1km long and 500m across,[2]^{: Figure 3.1} with a maximum surface area of 0.63km². The water level will vary between 494m and 558m AOD, corresponding to a storable volume of 25.9 million m³.[4]

A sloping headrace tunnel will take water down from the upper reservoir through the mountain to a vertical high-pressure shaft leading down to turbines located in a cavern within the mountain itself, and thence to an upwards sloping tailrace discharging into Loch Lochy. The turbines, motor-generator sets and water channels are reversible, so that water from the loch can be pumped back uphill to store electrical energy when needed.[4]

Depending on final design, the power station would have a generating capacity of up to 1500MW, and be able to store up to 30GWh of energy.[4]

The Scottish Government approved the scheme in 2020.[1]

In March 2023, SSE announced plans to spend £100M in exploratory work, including drilling a tunnel 1km into the mountainside to assess the geology. A final investment decision will depend on UK government assurances about how the regulated electricity market would reward storage schemes. SSE hope to make that £1.5Bn decision in 2024, in which case the scheme could be completed in 2031.[1]

• Project website
• Description of proposed development, from planning application documentation