Iron-Air Batteries: A New Option for Long-Duration Energy Storage

 

As renewable energy grows, the power grid needs more than just clean generation. It also needs ways to store electricity when wind and solar output is high, and release it when renewable generation drops.

 

Most people are familiar with lithium-ion batteries because they power phones, laptops, electric vehicles, and many grid-scale battery projects. But lithium-ion is not the only battery technology being explored for the energy transition.

 

One emerging option is the iron-air battery.

 

Iron-air batteries are not yet widely known or widely deployed, but recent developments suggest they could become important for long-duration energy storage, especially in electricity systems with high levels of wind and solar power.

 

A recent example is Ore Energy, a Dutch startup that signed an agreement with Budget Thuis to deploy up to 1GWh of iron-air battery storage in the Netherlands. The agreement includes a first phase of 400MWh, planned for 2028.

 

What Is an Iron-Air Battery?

An iron-air battery is a type of battery that stores and releases energy through a chemical reaction involving iron and oxygen.

 

The basic idea is often described as “reversible rusting.”

 

When the battery discharges, iron reacts with oxygen from the air and forms iron oxide, commonly known as rust. This reaction releases electricity.

 

When the battery charges, electricity is used to reverse the process, converting the iron oxide back into metallic iron.

 

In simple terms:

Discharging: iron turns into rust and releases electricity.
Charging: rust is converted back into iron using electricity.

 

The core materials are relatively simple: iron, air, and water-based chemistry. That is one reason the technology is attracting interest. Iron is abundant, widely available, and much less expensive than many of the critical minerals used in conventional battery supply chains.

 

Why Long-Duration Storage Matters

Most grid batteries today are designed to discharge power for a few hours. That is useful for shifting solar energy from the middle of the day into the evening, when electricity demand often rises.

 

But as power grids add more renewable energy, they face a bigger challenge: what happens when renewable output is low for longer periods?

 

This is especially relevant for wind-heavy grids. Wind generation can be strong for days and then drop for extended periods. During those gaps, the grid still needs reliable power.

 

That is where long-duration energy storage becomes important.

 

Long-duration storage can help bridge longer gaps between renewable energy supply and electricity demand. Instead of storing electricity for only two to four hours, technologies like iron-air batteries are being designed to store and discharge energy over multiple days.

 

How Iron-Air Batteries Differ From Lithium-Ion Batteries

Iron-air batteries are not trying to replace lithium-ion batteries in every application.

 

Lithium-ion batteries are compact, efficient, and well-suited for electric vehicles, consumer electronics, and short-duration grid storage. They are valuable where size, weight, and fast response are critical.

 

Iron-air batteries are different.

 

They are expected to be bulkier and less energy-dense than lithium-ion batteries. That makes them unsuitable for applications like cars, phones, or portable devices. But for stationary grid storage, bulk is not necessarily a dealbreaker.

 

If a battery is installed at a utility-scale site, the main questions become different:

 

• Can it store electricity for long enough?
• Can it be built at low cost?
• Can it use abundant materials?
• Can it scale safely and reliably?
• Iron-air batteries aim to answer those questions for long-duration storage.
• Why This Matters for Europe

 

Europe is trying to increase renewable energy, reduce dependence on fossil fuels, and strengthen energy security. But higher renewable penetration creates a need for more flexible storage.

 

Short-duration lithium-ion batteries can help manage daily fluctuations. But multi-day weather patterns require storage that works over longer periods.

 

For a country like the Netherlands, where wind power is an important part of the energy mix, long-duration storage could help reduce curtailment when renewable generation is high and provide electricity when wind generation drops.

 

This is why the Ore Energy deal is notable. The 1GWh headline is important, but the more significant point is the type of storage being proposed: multi-day discharge for a wind-heavy power system.

 

The Advantages of Iron-Air Batteries

Iron-air batteries have several potential advantages for grid-scale storage.

 

First, they use abundant materials. Iron is widely available and inexpensive compared with materials such as lithium, cobalt, or nickel.

 

Second, they are designed for long-duration discharge. This makes them potentially useful for storing renewable energy over days rather than hours.

 

Third, they may offer a more resilient supply chain. Because the main materials are common, iron-air batteries could reduce dependence on critical mineral supply chains.

 

Fourth, they are built for stationary use. For grid storage, weight and size matter less than cost, safety, duration, and reliability.

 

The Limitations and Open Questions

Iron-air batteries are still early in their commercial development. They should not be seen as a proven replacement for lithium-ion batteries today.

There are also tradeoffs.

Iron-air systems are bulky. They are not designed for mobility or compact applications. They may also be less efficient than lithium-ion batteries, meaning some energy is lost during the charge and discharge cycle.

 

The bigger questions are about execution:

• Can the technology be manufactured at scale?
• Can it meet cost targets?
• Can it operate reliably for many years?
• Can it be deployed quickly enough to support the growth of renewable energy?
• These questions will determine whether iron-air batteries become a major part of the grid storage market or remain a niche technology.

 

Why the Ore Energy Deal Is Worth Watching

Ore Energy’s agreement with Budget Thuis is important because it suggests that iron-air batteries are moving from pilot projects toward commercial-scale deployment.

 

The first phase of the agreement is planned for 400MWh in 2028, with the broader agreement covering up to 1GWh.

 

That does not mean iron-air batteries are already mainstream. They are not. But it does show that utilities and energy suppliers are beginning to take multi-day storage seriously.

 

The key point is not that iron-air batteries will replace lithium-ion batteries. The more likely outcome is that different technologies serve different roles.

 

Lithium-ion batteries may continue to dominate short-duration storage.

 

Iron-air batteries, if successful, could serve a different need: low-cost, long-duration, stationary storage for renewable-heavy grids.

 

Conclusion

Iron-air batteries are an emerging technology designed to solve one of the harder problems in the energy transition: how to store renewable electricity for days, not just hours.

 

They are bulky and still early in commercialization. But they also use abundant materials, have the potential for lower-cost long-duration storage, and are well-suited for stationary grid applications.

 

As renewable energy grows, the grid will need a mix of storage technologies. Lithium-ion has helped unlock short-duration storage. Iron-air batteries could help unlock the next layer: multi-day renewable power.

 

The Ore Energy deal in the Netherlands is worth watching because it points to where the storage market may be heading next.