The Scottish government has approved a plan to expand the Cruachan Power Station in Argyll with a 600 MW pumped hydro storage facility.

UK-based Drax Group, the project developer, said that the new pumped hydro facility will be built underground and will require an investment of GBP 500 million ($645.3 million).

Cruachan has a pumped hydro storage capacity of 440 MW and is one of only four pumped storage power stations in the United Kingdom. According to Drax, the plant currently runs for short periods to meet peaks in demand but can also operate continuously at full output for around 15 hours if necessary.

“The expansion of Cruachan requires an updated financial stabilization mechanism from the UK government,” the company said. “The current absence of a framework for large-scale, long-duration storage technologies has resulted in no new plants being constructed in the UK since 1984, despite their critical role in the decarbonization process.”

The Scottish government said that it is currently urging the UK government to provide an appropriate market mechanism to support pumped hydro and other long-term storage technologies.

Drax acquired the Cruachan Power Station for GBP 702 million from Spanish energy giant Iberdrola in 2019.