Hendrina Gravity Energy Storage System

Executive Overview

The Hendrina Gravity Energy Storage System is a 25 MW / 100 MWh (four-hour duration) long-duration energy storage project to be deployed by Energy Vault (NYSE: NRGV) at Eskom's Hendrina Power Station in Pullens Hope, Mpumalanga, South Africa, under a Strategic Development Agreement announced May 13, 2026. The agreement also frames a broader partnership to license, co-develop, and deploy up to 4 GWh of long-duration gravity storage across the 16 member states of the Southern African Development Community (SADC) by 2035. The Hendrina site itself is designed to be scalable up to 4 GW of power capacity. The project anchors Energy Vault's first commercial GESS deployment in Africa and is positioned as a flagship asset of Eskom's Just Energy Transition strategy.

How It Works & Differentiation

The system uses Energy Vault's EVx 2.0™ Gravity Energy Storage System (GESS), which stores electricity by raising heavy composite blocks (potentially weighing 25–30 tonnes each) and releases it by lowering them through electric motor-generators — the same physics as pumped hydro storage, but with solid masses instead of water. Critically, the EVx 2.0 platform incorporates material-science technology that uses coal combustion ash from Hendrina (a coal plant being decommissioned under South Africa's Just Energy Transition) as the storage medium in the blocks themselves. This converts a regional waste liability into a structural asset and creates a circular-economy story specific to South Africa's coal-heavy generation fleet. The differentiator versus lithium-ion BESS is duration economics: gravity storage scales storage duration largely independently of power output, with no chemistry degradation over cycles, making it suitable for 4+ hour applications and beyond.

Commercialization & Traction

Energy Vault's first commercial GESS is operating in Rudong, China, with three additional Chinese systems under construction (including one in Zhangye). The Hendrina project is Energy Vault's first announced gravity deployment in Africa and a meaningful expansion beyond China for the GESS product line. Eskom is South Africa's state-owned electricity utility, supplying over 86% of national electricity and ~20% of all electricity produced on the African continent. Under the agreement, Energy Vault provides EVx 2.0 GESS technology, on-site engineering, project management, and localized training. No financial terms, contractor selection, or project timeline (commercial operation date) were disclosed at announcement.

Scalability & Strategic Context

The project directly supports Eskom's Just Energy Transition Partnership (JETP) — South Africa's internationally backed framework for decarbonizing a coal-dependent grid (coal supplied >80% of 2024 generation). Hendrina is one of nine Eskom coal stations scheduled for decommissioning by 2035; repurposing the site with long-duration storage preserves grid infrastructure, transmission interconnection, and local employment. The 4 GWh SADC-wide ambition, if realized, would constitute one of the larger LDES deployment programs globally and would extend storage access to a region where 56% of the population currently has electricity access (up from 36% a decade ago). Risks worth flagging: Energy Vault's gravity storage technology faces ongoing technical and economic scrutiny from industry analysts, UK peer Gravitricity entered administration in 2026, and Energy Vault itself has diversified into lithium-ion BESS and green hydrogen. The Strategic Development Agreement is a framework, not a binding offtake or construction contract; no COD timeline was disclosed.