SOLID wants to turn iron pellets into a safe hydrogen battery

With the Steam Iron Reactor 2, the Eindhoven student team is taking a step from proof of concept to industrial pilot. In doing so, SOLID builds on a legacy that gave rise to RIFT, while clearly choosing a different route.

On Friday, at High Tech Campus Eindhoven, the focus was not on a gleaming factory hall, but on a shipping container. Yet for TU/e student team SOLID, that container symbolised a major step: the transition from laboratory research to a pilot installation that, in the coming years, must demonstrate in practice whether iron pellets can become a safe and scalable form of hydrogen storage.

During SOLID Event 2026, the team announced the development of the Steam Iron Reactor 2, an iron-based hydrogen storage system with a capacity of 2.5 MWh. Patrick Groothuis, Vice President of TU/e, and Bas Maes, Provincial Executive for Energy of the Province of North Brabant, jointly unveiled the container in which the new installation will be built. The scale is substantial for a student team: the capacity is comparable to the daily electricity output of around 2,000 modern solar panels.

According to team manager Sam Liebregts, the project marks a turning point. “We are moving from proof of concept to practice. It shows that student teams can play a serious role in the energy transition. We are now taking a giant step toward real impact.”

Iron as a hydrogen battery

Team SOLID’s technology starts from an idea that is simple in concept but technically challenging: using iron as a circular energy carrier. Renewable energy can be stored by using hydrogen to convert rust (iron oxide) back into iron. The energy is then safely stored in those iron pellets. When the iron later comes into contact with steam, hydrogen is produced again. In the process, the iron becomes iron oxide once more, after which the cycle can begin again.

In this way, the material functions as a kind of reusable hydrogen battery. Not by storing hydrogen under high pressure or at extremely low temperatures, but by chemically locking the energy into solid pellets. That is precisely where the promise lies: iron is relatively inexpensive, widely available, easy to transport, and stable to store. Moreover, no energy is lost during storage and transport, which means the system could be suitable for storage over days, weeks, or even months.

With this approach, SOLID is targeting one of the most persistent challenges in the energy transition. Solar and wind power are generating more and more renewable electricity, but not always when the industry needs it. Large-scale storage is therefore crucial. Batteries can do a lot, but they are not suitable for every application. Hydrogen offers opportunities, but storage and transport remain complex. Iron pellets could fill that gap: as a solid, safe, and reusable carrier of hydrogen.

A different route from RIFT

Team SOLID has been working on iron-based energy technology since 2016. Over the past ten years, hundreds of students have built on each other’s research, prototypes, and systems. That legacy is tangible. In 2020, the student team gave rise to RIFT, the Eindhoven spin-off that uses iron powder as a circular fuel for industrial heat. The company has grown into one of the best-known examples of TU/e student innovation making the leap to the market.

RIFT burns iron powder to produce heat. The rust formed in the process can be converted back into iron powder using hydrogen. This also creates a circular chain, but with a different purpose: emission-free industrial heat. RIFT has since raised €114 million for its first commercial iron fuel project and previously received support from Bill Gates’ Breakthrough Energy network.

The current SOLID team is choosing a different position within that same iron family. Whereas RIFT uses iron as a heat source, SOLID uses iron pellets to store hydrogen safely and release it later in a controlled manner. That difference is fundamental. SOLID is not building a burner, but a storage system. The focus is not on the direct production of heat, but on the ability to temporarily store renewable energy and make it available when industry needs it.

That is exactly where this generation of students differs from its predecessors. SOLID’s pioneers proved that iron as an energy carrier deserved to be taken seriously and laid the foundation for RIFT. The current generation carries that legacy forward, but moves into a different application area: safe, stationary hydrogen storage at pilot scale. “With this project, we are moving beyond laboratory development and taking an important step toward demonstration in real-world environments,” says Liebregts. “It represents years of work by hundreds of students and shows how student-driven innovation can play a key role in the energy transition.”

IJzerkracht: student team as the largest project partner

The Steam Iron Reactor 2 is being developed within Project IJzerkracht, a consortium of twelve partners from industry, research, and education. In addition to Team SOLID and TU/e, Avans University of Applied Sciences and HZ University of Applied Sciences are among the participants. The total project value is €3 million. Remarkably, Team SOLID is the largest project stakeholder within the consortium. This makes IJzerkracht the largest student team project to date.

That matters because the step from lab to practice is usually the hardest one. A proof of concept can show that a technology works. A pilot has to demonstrate that it is also reliable, safe, manageable, and economically viable under conditions that closely resemble reality. The new installation will be housed in a 20-foot container and is expected to take 1.5 to 2 years to build. After that, a testing program will follow at several locations, examining performance, reliability, operational requirements, and industrial applicability.

According to Saleh Mohammadi, Professor of Renewable Energy Carriers at Avans and consortium leader of IJzerkracht, the project shows what happens when student innovation is connected to the wider ecosystem. “Student teams offer a unique environment where technical talent, entrepreneurship, and societal challenges come together. The IJzerkracht project shows what can be achieved when students, researchers, industry, and government work together to accelerate the development of promising energy technologies.”

High Tech Campus as an accelerator

The fact that the unveiling took place at High Tech Campus Eindhoven is more than a decorative choice. For a technology that must grow beyond the protected environment of the lab in the coming years, proximity to companies, researchers, investors, and potential launching customers is essential. High Tech Campus is exactly that kind of environment: a place where hardware, systems development, deep tech, entrepreneurship, and international business activity meet every day.

For SOLID, that location can help the team learn faster what industrial users require. How should such a system be integrated into existing energy infrastructure? Which safety standards apply? What does maintenance mean in a factory setting? How do you scale from one container to multiple systems? And under what conditions does iron-based hydrogen storage become more attractive than alternatives?

The campus can also help narrow the gap between the student team and the market. RIFT has already shown that an idea from a student team can grow into a company that attracts serious funding and industrial partners. For SOLID, the next phase is not yet commercialisation but rather preparation for it. The pilot must generate the knowledge needed to determine where the technology has the greatest value later on: in industrial energy storage, grid balancing, hydrogen logistics, or specific applications where safety and long-duration storage are decisive.

The coming years: testing, learning, refining

The expectations for the coming years are therefore concrete, but far from noncommittal. First, the Steam Iron Reactor 2 must be built. After that, the system must prove at several locations that the cycle of iron, iron oxide, and hydrogen not only works technically, but is also repeatable and practically applicable. The questions will then become less academic and much more operational: how quickly can the system charge and discharge? How efficient is the cycle? How does the material behave after many rounds? How robust is the installation under varying conditions? And what does this require from operators, permits, and maintenance?

For a student team, that is an ambitious agenda. At the same time, that very dynamic is SOLID’s strength. New talent joins every year, while knowledge from previous generations is passed on. The team’s history shows that such continuity can lead to unexpectedly large steps. First, a student team experimented with iron as an energy carrier. Then came RIFT. Now there is a new generation that is not simply trying to copy that path, but is choosing its own route: using iron not as a fuel for heat, but as a safe carrier for hydrogen.

The container on High Tech Campus is therefore more than just housing for a pilot installation. It is an intermediate station in a longer development: from student idea to system, from system to pilot, and possibly later from pilot to industrial application. Whether iron pellets will indeed play a key role in renewable energy storage remains to be seen in the coming years. But with the Steam Iron Reactor 2, Team SOLID has clearly raised the bar.