Hendrina Gravity Energy Storage System

Eskom Holdings SOC Limited, South Africa's state-owned electricity utility, and Energy Vault Holdings (NYSE: NRGV) announced a Strategic Development Agreement on May 12, 2026 to deploy a long-duration gravity energy storage system (GESS) at Eskom's Hendrina Power Station in Mpumalanga province. Hendrina is one of Eskom's oldest operating coal plants (2,000 MW installed; commissioned 1970–1976) and has been earmarked for decommissioning under South Africa's Just Energy Transition.

The first-phase system will be 25 MW / 100 MWh, providing 4 hours of storage. Energy Vault will supply its EVx 2.0 GESS technology platform along with on-site engineering, project management, and localized training. The EVx 2.0 design uses composite blocks weighing 25–30 tons each, with material science enabling re-use of coal combustion ash (a waste byproduct from Eskom's coal fleet) as the storage medium — a notable circular-economy angle that ties the project directly to repurposing the host site's legacy.

The agreement is structured to be scalable: the Hendrina design is rated for expansion to 4 GW, and the partnership envisions deploying up to 4 GWh of gravity storage across the 16 member states of the Southern African Development Community (SADC) by 2035. No timelines were disclosed for the first-phase commissioning or for the broader regional rollout, and financial terms were not announced.

The project supports Eskom's Just Energy Transition Partnership (JETP) framework, which aims to transition the country away from coal (still ~80%+ of generation in 2024) while preserving grid reliability, creating local jobs, and supporting economic development in coal-dependent regions. Context worth flagging: gravity-based energy storage remains a contested technology category — UK peer Gravitricity went into administration earlier in 2026, and Energy Vault has faced ongoing scrutiny over the commercial viability of its gravity product (Q1 2026 net loss of US$32.49M, though it reaffirmed 2026 revenue guidance of US$225–300M). The Hendrina deal is Energy Vault's first announced gravity project outside China.