A new storage model enters a coal-heavy grid story
South Africa’s state-owned utility Eskom is exploring grid-scale gravity storage through a new agreement with Energy Vault, a move that gives one of the power sector’s more unconventional long-duration technologies a prominent proving ground. According to pv magazine, the companies signed a strategic development agreement covering a potential 25 megawatt, 100 megawatt-hour gravity energy storage system at the Hendrina Power Station in Mpumalanga.
The deal matters because it is not limited to a single demonstration site. It also establishes a framework to license, co-develop and partner on up to 4 gigawatt-hours of long-duration storage deployments across the 16 states of the Southern African Development Community. That regional scope turns what might otherwise look like a pilot into a broader commercial beachhead.
How the proposed system would work
Energy Vault plans to use its EVx 2.0 gravity platform at Hendrina, one of Eskom’s oldest coal stations. The system would rely on large blocks made from waste coal ash, with each block potentially weighing 25 to 30 tons. The concept is simple in principle even if the engineering is complex in practice: use gravity as the storage medium by lifting and lowering heavy masses to absorb and release energy.
The company says the platform includes advances in software orchestration, mechanical operations and construction automation. Those elements are central to whether gravity systems can compete with more established storage options, particularly on cost, reliability and deployment speed. In markets that need longer-duration storage and have legacy industrial sites, the ability to repurpose waste materials and existing power infrastructure could be part of the pitch.
Why South Africa is a consequential test case
South Africa is an especially significant venue for this kind of experiment. Eskom sits at the center of a grid under constant pressure to balance aging assets, growing clean-energy integration needs and the practical realities of infrastructure transition. Locating the proposed storage system at a coal station underscores the symbolic and operational overlap between the country’s old energy base and the technologies being considered to support a different future.
The use of waste coal ash is also notable. If the project advances, it would connect industrial byproducts from the fossil era to a storage technology marketed for the low-carbon grid transition. That does not erase the challenges associated with coal dependence, but it does point to an approach that tries to extract additional value from legacy material streams rather than treating them only as disposal burdens.
A regional ambition, not just a single contract
The larger framework around the Eskom agreement may be the more important business signal. Up to 4 gigawatt-hours of possible long-duration storage activity across Southern Africa indicates that Energy Vault is trying to position gravity storage as a regional infrastructure option, not merely a niche demonstration technology. The countries named in the source include Zimbabwe, Mozambique, Angola, Botswana, Tanzania and Zambia, among others.
That ambition faces obvious questions. Gravity storage remains far less established than lithium-ion batteries, and long-duration storage markets are still evolving in terms of procurement, bankability and system planning. But utilities are increasingly looking for storage types that can do more than short-burst balancing. If Eskom is willing to evaluate the technology at grid scale, that alone gives the sector a notable validation point.
What to watch next
The agreement does not mean the full regional buildout is guaranteed. The immediate reference point is the proposed 25 MW / 100 MWh Hendrina installation. Whether that project advances, how it is financed and how it performs will shape perceptions of gravity storage’s prospects in the region.
Still, the announcement marks an important step. It places gravity energy storage inside a utility conversation that is usually dominated by batteries, pumped hydro and thermal options. For Eskom, it represents another avenue for strengthening grid flexibility. For Energy Vault, it is a chance to prove that gravity-based long-duration storage can move beyond concept-stage attention and into serious utility planning in one of the world’s most consequential power-transition environments.
This article is based on reporting by PV Magazine. Read the original article.
Originally published on pv-magazine.com
