Johannesburg, May 12, 2026, 19:04 SAST
- Energy Vault and Eskom are teaming up to develop a 25-MW gravity storage system, with 100 MWh of capacity, at the Hendrina Power Station in Mpumalanga.
- The two firms are targeting as much as 4 GWh of storage to be built throughout the 16-nation Southern African Development Community by 2035.
- The agreement comes while coal continues to dominate South Africa’s power mix—83% of electricity in 2024, according to official data.
Energy Vault Holdings Inc. and Eskom Holdings SOC Ltd. have inked a strategic development agreement aiming to install a gravity-based energy storage system at Eskom’s Hendrina Power Station. The project offers South Africa’s state-run utility a fresh shot at repurposing coal assets, as the nation pushes to stabilize its grid and tackle emissions.
Energy Vault’s initial project aims to provide 25 MW of output over a four-hour stretch, totaling 100 MWh, all powered by its EVx 2.0 technology. According to both firms, there’s room to ramp up capacity dramatically—potentially reaching 4 GW—at Hendrina, an aging Eskom coal plant.
Timing is key here. Eskom shifted out of crisis mode and, back in April, projected no load shedding between April 1 and Aug. 31 thanks to decreased unplanned outages and better plant performance. Long-duration storage—systems capable of holding and dispatching electricity for several hours or more—is designed to shore up supply as wind and solar capacity expands on the grid.
Energy Vault is set to deliver its EVx 2.0 system, along with equipment, engineering services, project management, and onsite training. The agreement also includes plans for licensing and joint development of as much as 4 GWh of gravity storage throughout the Southern African Development Community by 2035.
Think of gravity storage as a kind of mechanical battery—electricity gets stored by hoisting giant weights, then recaptured when those weights drop back down. Energy Vault claims its long-duration setups can stretch from four up to 24 hours, using mobile composite blocks as the mass, not the battery cells you’d find in standard chemical systems.
There’s also a local materials twist to the Hendrina system. Energy Vault claims its EVx 2.0 platform can utilize coal ash—waste from combustion—as feedstock for storage blocks that come in at 25 to 30 tons each. Essentially, some of the coal plant’s waste is repurposed as the heart of the storage solution.
Energy Vault CEO Robert Piconi described the Eskom deal as a “transformational milestone.” Dan Marokane, who heads Eskom, said the companies’ technology is set to play a “pivotal role” in advancing the utility’s Just Energy Transition ambitions, according to both firms. Business Wire
The agreement brings Energy Vault into a wider contest for long-duration energy storage. Form Energy is advancing with its iron-air battery tech and revealed plans in March for a 10-MW, 1,000-MWh installation in Ireland. Highview Power, meanwhile, is working on a liquid-air storage facility near Manchester, targeting 300 MWh and six hours of storage time.
Still, most of the key commercial information wasn’t disclosed. There’s no word yet on the project’s cost, how it’ll be financed, when construction kicks off, the price secured for power, or when operations might actually start. For developers working on long-duration storage, the comparison to lithium-ion batteries—currently dominating grid storage in plenty of regions—remains tough.
Energy Vault’s new deal in South Africa comes as the firm pushes further into ownership and operation of storage and power assets. First-quarter revenue jumped to $21.9 million from $8.5 million the prior year. As of May 5, backlog stood at $1.35 billion.
Energy Vault was trading at $4.84 Tuesday afternoon in New York, putting its market cap close to $792 million.
