South African electricity utility Eskom is moving ahead with plans to set up long-duration gravity energy storage systems (GESS) at coal power stations that are slated for decommissioning.

It has signed a strategic development agreement with US-based Energy Vault, which will see the first system installed at the Hendrina power station in Mpumalanga, expected to be decommissioned by 2030.

Engineering News reports that the system is expected to provide 25 MW of capacity with four hours of storage, equivalent to 100 MWh, and is designed to be fully scalable up to 4 GW.

According to a research paper in Wiley Interdisciplinary Reviews online library, GES systems rely on ‘the vertical movement of heavy objects in the gravity field to store or release potential energy which can be easily coupled to electricity conversion’. The systems can be linked to renewable energy sources such as solar PV and wind.

Eskom CEO Dan Marokane believes the partnership will play a ‘pivotal role’ in South Africa’s Just Energy Transition.

‘By combining our breakthrough EVx 2.0 platform with Eskom’s extensive power generation, grid expertise and regional reach, we’re not only advancing long-duration storage at unprecedented scale but also pioneering a new model for sustainable industrial development,’ says Energy Vault chair and CEO Robert Piconi.

Energy Vault systems have storage capability from four to 24 hours, and they have a 35-year technical lifetime.

26 May 2026
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