A typical 12-meter shipping container quietly made history on July 30, 2025, while it was parked on the grounds of Delft University of Technology in the Netherlands. It contained iron pellets that reacted with airborne oxygen to turn back into rust and release electricity into the public grid. It was the first time a live electrical network had ever been linked to an iron-air battery. As is often the case, the announcement was modest. The consequences weren’t.
Iron-air batteries are intended to address a problem that has plagued the shift to renewable energy for many years. When the sun shines and the wind blows, which isn’t always when people need electricity, solar panels and wind turbines generate power. Short intervals, usually four to six hours, can be filled by lithium-ion batteries, but extending that time over several days makes them unaffordable. By turning on when renewable energy sources are insufficient and shutting off when they are, fossil fuel plants, especially gas peakers, have purposefully filled that gap. Something that can store energy for days rather than hours is needed to replace that capacity. Iron-air batteries are designed to accomplish just that.
| Category | Details |
|---|---|
| Technology | Iron-Air Battery (Long-Duration Energy Storage) |
| Key Companies | Ore Energy (Netherlands), Form Energy (Massachusetts, USA) |
| World First | Ore Energy connected the world’s first grid-operational iron-air battery system — July 30, 2025 |
| Location of Deployment | The Green Village, TU Delft (Delft University of Technology), Netherlands |
| Storage Duration | 100+ hours (vs. 4–6 hours for lithium-ion grid batteries) |
| Target Cost | Below $20/kWh — a fraction of lithium-ion grid storage costs |
| Core Materials | Iron, air (oxygen), water — all abundant, non-toxic, and globally available |
| Form Energy | Raised over $400M; commercial factory operational in Weirton, West Virginia (former steel mill site) |
| Form Energy Clients | Xcel Energy, Georgia Power — projects expected online 2025–2026 |
| Each Unit Capacity | Multiple MWh per 40-foot modular container; one MWh powers a typical US home for over a month |
| CEO — Ore Energy | Aytaç Yilmaz, co-founder |
| Reference Links | New Scientist — First Grid-Connected Iron-Air Battery · Sustainability Magazine — The Rust Revolution |
Their underlying chemistry is almost unbelievably straightforward. The battery absorbs oxygen from the surrounding air during discharge, which combines with the metallic iron pellets inside the battery to create iron oxide, or rust. Electrical energy is released during that reaction. In order to recharge, electricity runs in reverse, releasing oxygen and turning the rust back into iron. The cycle is repeated. repeatedly. utilizing materials that are incredibly abundant and nearly free. The most mined metal on Earth is iron. The air is free. The costly and politically sensitive lithium, cobalt, and nickel used to power traditional grid batteries are replaced by water-based electrolytes.
The Dutch startup Ore Energy, which successfully connected to the grid at TU Delft, used components that could be sourced from within Europe to build its pilot system entirely within the EU. That particular detail is more important than it first appears. A new and unsettling dependency has emerged as a result of the clean energy transition: rare mineral imports have replaced oil imports, with supplies of cobalt and lithium becoming more concentrated in a few nations. Iron-air batteries virtually completely avoid that issue. Rust does not have a geopolitical chokehold.
Form Energy has been pursuing the same goal via a different route across the Atlantic. The Massachusetts-based company operationalized its manufacturing facility in Weirton, West Virginia, after raising over $400 million to commercialize iron-air technology. This is a noteworthy detail because the factory is located on the site of a former steel mill and Weirton was formerly a steel town. Both the labor force and the materials used to make these batteries are connected to the same industrial past that the energy transition is meant to transcend. It’s a strange symmetry that has some poignancy.
Utilities like Georgia Power and Xcel Energy are placing orders for Form Energy’s batteries, and projects are anticipated to go online in 2025 and 2026. Each unit fits into a typical 40-foot modular container that can store several megawatt-hours of energy, which is sufficient to power thousands of homes during a multi-day lull in solar and wind power. Compared to lithium-ion grid storage, which has historically been several times more expensive at scale, the target cost is below $20 per kilowatt-hour, which is a fundamentally different economic proposition.
Here, the sincere skeptic might have a few valid objections. Iron-air batteries weigh a lot. They are heavy. Compared to lithium-ion, they have a lower round-trip efficiency, or the proportion of stored energy that is actually released. They take a while to charge and discharge. For a large static installation near a wind farm, where weight is unimportant and speed is not the goal, none of those factors really matter. Cost and duration are crucial. Iron-air appears to be truly competitive on both of those metrics, something that few other storage technologies have been able to do.
As this develops, there’s a sense that the energy storage discourse has been waiting for precisely this kind of advancement—something that doesn’t call for unusual materials, doesn’t increase the risk of fire like lithium-ion installations do, and doesn’t require supply chains that must pass through geopolitically challenging areas. One researcher said, “You can’t set fire to water,” in reference to the electrolyte that is based on water. Perhaps it’s a low bar, but considering the difficulties lithium-ion fires have caused for large-scale battery installations worldwide, it’s also a real one.
It is still unclear if iron-air will scale quickly enough to be significant during the upcoming ten years of energy transition. Although the technology is still in its early stages of implementation, it has been proven in theory. TU Delft’s grid connection is a pilot, not a commercial rollout. Utility contracts from Form Energy are an example of early adoption rather than widespread use. However, the chemistry is effective, the direction is clear, the materials are inexpensive, and the grid problem they are addressing is urgent. One of the most significant energy advancements of the decade could be the reaction of the most prevalent metal in the world with the surrounding air.
