Eskom Partners with Energy Vault for Gravity Storage
Eskom's partnership with Energy Vault marks a significant step in South Africa's energy transition—discover the potential impact!
South Africa's grid faces a trust problem. For years, Eskom — the country's state-owned utility and transmission system operator — became synonymous with "load shedding," the polite term for rolling blackouts that knocked out power for hours at a time, gutting businesses and exhausting households. So when Eskom makes a move into experimental energy storage technology, people pay attention — and some raise their eyebrows.
The latest move: a strategic development agreement with California-based Energy Vault to deploy a 25MW/100MWh gravity energy storage system at the Hindrina Power Station in Mpumalanga, the coal-heavy northeastern province that has powered South Africa for decades. The project could eventually scale to 4GW capacity, though no timeline has been attached to that number yet.
That's either a bold bet on emerging technology at exactly the right moment — or a risky experiment on a grid that can't afford more problems. Possibly both.
How Gravity Energy Storage Actually Works
The concept is almost elegantly simple, which is part of why it keeps attracting attention despite persistent skepticism.
Energy Vault's EVx system moves massive composite blocks vertically — up when energy needs to be stored, down when it needs to be released. The mechanics are essentially the same physics that make pumped hydropower work, except instead of moving water between reservoirs at different elevations, you're moving solid blocks in a purpose-built tower structure. No water required. No geography required. Just physics and engineering.
What makes the approach practically interesting, particularly in South Africa's context, is what those blocks can be made of. Energy Vault builds them from industrial waste materials — including coal ash. A country sitting on mountains of waste from decades of coal combustion suddenly has a feedstock for energy storage rather than an environmental liability.
The company's first operational gravity storage system came online in Rudong, China, developed in partnership with a waste management company. Three more are currently under construction globally, including a project in Zhangye. The EVx 2.0 GESS technology being deployed with Eskom represents the latest generation, with architectural improvements specifically designed to enable scaling to multi-gigawatt capacity — something the original EVx design couldn't readily do.
For context on that scale: 100MWh can power roughly 10,000 average South African homes for a full day. The 4GW potential buildout across the Southern African Development Community's 16 member states is a genuinely large number — though "potential" is doing a lot of work in that sentence.
The Partnership's Scope — and What It's Really About
The Hindrina project isn't just a pilot. Eskom and Energy Vault have structured this as a platform agreement, with ambitions extending well beyond a single site.
Under the deal, Energy Vault will supply its EVx 2.0 technology along with on-site engineering support, project management, and critically, training services for local staff. That last element matters more than it might seem. One of the consistent criticisms of large infrastructure deals in developing markets is that they import expertise rather than build it. If the knowledge transfer is real, this creates a domestic workforce capable of maintaining and eventually replicating the technology.
The partnership also includes plans to license, co-develop, and deploy up to 4GWh of long-duration energy storage across all 16 SADC member states — a regional ambition that would make this far more than a South Africa story if it materializes.
The framing explicitly ties into Eskom's Just Energy Transition Partnership (JETP) initiative. JETP is South Africa's international financing framework for moving away from coal while maintaining grid reliability and creating economic opportunities in the communities most dependent on coal employment. Mpumalanga is ground zero for that challenge — it's where the coal plants are, where the coal jobs are, and where the social disruption of energy transition hits hardest.
Using coal ash as a construction material for energy storage blocks is a genuinely clever piece of circular economy thinking for this context. It doesn't solve the transition problem, but it converts a waste stream into a resource, which is the kind of thing that makes JETP commitments easier to defend politically.
The Context: A Grid That's Been Through It
Eskom's reliability track record makes the stakes here concrete. South Africa experienced years of severe load shedding — at its worst, Stage 6 cuts meant up to 12 hours without power daily, across a country where reliable electricity is the baseline for virtually every economic activity.
The recent milestone of going over 300 consecutive days without load shedding represents a genuine operational turnaround, driven by a combination of new generation capacity, better plant maintenance, and a significant push into renewable energy procurement. Eskom has been procuring gigawatts of solar, wind, and battery storage through multiple schemes simultaneously.
That renewable buildout creates its own problem: solar and wind are intermittent by nature. You need storage to make them grid-reliable. This is precisely where long-duration energy storage becomes non-negotiable rather than optional. A grid that runs on solar during the day and goes dark at night hasn't solved anything — it's just shifted the problem.
Battery energy storage systems (BESS) are already being deployed at scale in South Africa, but lithium-ion batteries are optimized for short-duration response — typically two to four hours. Long-duration storage that can discharge for eight, ten, or twelve hours is a different product solving a different problem. Gravity storage, in theory, addresses that gap.
The Criticisms Are Real and Shouldn't Be Dismissed
Energy Vault has never been short of skeptics, and some of the skepticism is well-founded.
The company's CEO Rob Piconi faced pointed questions in a 2023 interview about technology viability, economics, and the gap between announced projects and operational ones. The round-trip efficiency of gravity storage systems — how much of the energy you put in you actually get back out — has been a persistent question mark compared to lithium-ion. Gravity systems also require significant civil infrastructure, which adds cost and complexity.
The recent administration of UK-based Gravitricity, a gravity storage peer, is a data point worth taking seriously. It doesn't mean the technology doesn't work, but it does illustrate that the space is not without commercial risk. Early-mover advantages in emerging technology can flip into first-mover disadvantages when development costs outpace revenue.
Energy Vault itself has adapted — diversifying into short-duration BESS and green hydrogen, including operating as an owner rather than just a technology licensor. The company reaffirmed 2026 revenue guidance of $225–300 million this week, which suggests a business that hasn't bet everything on one technology. That diversification is probably prudent, but it also means gravity storage is competing for internal capital and management attention alongside other business lines.
For Eskom, the 25MW/100MWh initial deployment is measured risk. It's large enough to generate real operational data, small enough that it won't destabilize the broader grid strategy if the technology underperforms. Think of it as an expensive but necessary proof of concept — one that happens to align with international climate finance requirements at the same time.
What Comes Next
The real test for this partnership isn't the announcement. It's whether the Hindrina project reaches commercial operation, what its actual performance data shows, and whether that data supports the case for the broader SADC rollout.
South Africa's energy transition is moving faster than most observers expected even three years ago. The procurement pipelines are real, the political will — however imperfect — is present, and international financing is available. The missing piece has always been reliable, long-duration storage at a cost that doesn't require heroic assumptions about future price declines.
If Energy Vault's EVx 2.0 delivers at Hindrina, it won't just matter for Eskom. It will matter for every grid operator on the African continent watching to see whether gravity storage graduates from ambitious concept to proven infrastructure. That's a much bigger audience than one power station in Mpumalanga.
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