New Hollow Mountain renewable energy project planned

Cruachan is one of only four pumped hydro storage schemes in the UK

A planning application could be submitted next month to construct a new underground power station at Scotland's Hollow Mountain.

Renewable power developer Drax has proposed building the complex at its Ben Cruachan site in Argyll.

The company intends to submit an application to the Scottish government in April and work could start in 2024 if the plans are approved.

The existing underground power station was opened by the Queen in 1965.

At the time, it was the first large-scale reversible turbine storage energy project of its kind in the world.

It is housed within a huge cavern dug out inside Ben Cruachan, which is nicknamed Hollow Mountain because of the project.

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The new plans would more than double the facility's generating capacity to more than 1GW, and involve excavating more than a million tonnes of rock.

Drax would invest £500m in the construction project over seven years.

The new complex would be constructed below where these sheep are standing

Inside Argyll's Hollow Mountain

Cruachan is a pumped hydro storage scheme and one of only four in the UK. The others are Foyers, which is also in Scotland, and Dinorwig and Ffestiniog in Wales.

The schemes involve two bodies of water at different heights. The water flows from one to the other through tunnels, passing through a power station inside a cavern which has been created by hollowing out part of the mountain.

When there is low demand for electricity from consumers and/or when surplus power is available from wind farms, electricity is used to pump water from the lower level to fill a reservoir further up the hill.

A large-scale pumped storage scheme has not been built in the UK for 38 years.