Gravity energy storage at Europe's deepest copper mine

One of Europe's deepest mines in central Finland could host the continent's first full-scale gravity energy store.

Near Pyhäjärvi, a community with 5,000 inhabitants 450km north of Helsinki, is Europe's deepest zinc and copper mine at 1,444m. The Pyhäsalmi Mine is currently owned by Canadian First Quantum Minerals.

Its disused mine shaft is now being planned as an underground energy store, using technology developed by Edinburgh-based Gravitricity.

The scheme would deliver up to 2MW of storage capacity to tie straight into the local electricity grid and provide balancing services to the Finnish network.

The Scottish company has developed GraviStore, which raises and lowers heavy weights suspended in a deep shaft by cables attached to winches.

When there is excess electricity, for example on a windy day, the weight is winched to the top of the shaft ready to generate power.

This weight can then be released when required – reportedly less than a second – and the winches become generators, producing either a large burst of electricity quickly, or releasing it more slowly depending on what is needed.

The local community's development company, Callio Pyhäjärvi, plans to promote regeneration projects at the mine.

The two organisations have agreed to transform a 530m-deep auxiliary shaft into a full-scale prototype.

In 2023, Gravitricity signed an agreement with Swedish-Swiss energy multinational ABB to use their mine hoist expertise to help accelerate underground energy storage. 

Gravitricity’s Executive Chairman Martin Wright says, 'This project will demonstrate at full scale how our technology can offer reliable long life energy storage that can capture and store energy during periods of low demand and release it rapidly when required.'

The underground energy store would be one of a number of initiatives at the former mine, including solar farms, new technology start-ups, mining technology testing and an underground 5G network.

Callio Pyhäjärvi’s CEO, Henrik Kiviniemi (of Pyhäsalmen Kvanttikiinteistöt Ltd), notes, 'We can take advantage of the best of the region’s electricity grid and transformation of the energy market. It is also very attractive to take advantage of these opportunities for an energy-intensive industry to be located here utilising also the good logistical location of Pyhäjärvi.'