Scenarios for a new iron age: Iron to complement hydrogen as an energy carrier

Be it for wind energy from coastal regions or for solar power from desert areas – iron could serve as a transportable energy carrier in the future to make these renewable energy sources usable worldwide. “This works in a cycle that emits no carbon dioxide or environmentally harmful substances,” said Julia Schuler from KIT’s Institute for Industrial Production (IIP). For power generation, iron powder is combusted, producing iron oxide, i.e. rust. Using hydrogen from renewable sources, it is reduced to iron again in a process that removes the oxygen it contains. The iron powder can then be reused. “When burned, iron powder behaves very much like coal. We wanted to find out whether it was possible to repurpose existing coal power plants to iron-firing,” said Schuler. She believes that modifications are primarily necessary in the heat-generator; other components, such as the steam cycle, turbines, generator, and power grid connection could continue to be used.
 

Iron Cycle Complements Hydrogen Economy

Based on the findings from the Clean Circles research project, KIT scientists conducted a study funded by the Stiftung Energieforschung Baden-Württemberg (Baden-Württemberg energy-research foundation) to examine how the iron cycle could be used for power generation in a climate-neutral European energy system. It is. For the study, the researchers extended PERSEUS, an established energy-system model, by adding options for retrofitting coal-fired power plants, reduction facilities, as well as storage and transport pathways. Using the extended model, they subsequently projected an optimum development of the European energy system until 2050. Here, the iron cycle competed with other technologies such as batteries, hydrogen storage systems, and hydrogen power plants.
 

The results show that iron will not supersede hydrogen-based power generation, but might usefully complement it in a climate-neutral energy system. Iron is particularly well-suited as a long-term energy storage material. In powder form, it is comparably easy to store and transport, while hydrogen, on the other hand, requires a costly network of pipelines, import terminals, and underground storage facilities. The use of iron powder would allow renewable energy to be transported globally with less infrastructure investment. At the same time, excess electricity in Europe could be used for the conversion of iron powder in local reduction facilities, producing a storable energy source via an intermediate hydrogen production step.
 

In simulations, iron powder fired power plants proved to be particularly promising in countries with limited possibilities for generating hydropower or for underground storage of hydrogen. In such regions, iron may contribute to filling the supply gaps during longer periods of insufficient energy generation from wind or solar power plants. At the same time, it takes some of the strain off the hydrogen infrastructure, for example when import capacities or transport pipelines reach their limits. The potential is particularly great in Germany with its large number of coal power plants. Turbines, grid connections, heat networks, and other parts of their infrastructure could be retained.
 

Reducing Costs with Iron Cycle 

When looking at the future development of the technology, it is an encouraging signal for the researchers that power plants fired by iron powder were an integral part of a cost-minimizing energy system across all considered scenarios. “Iron might play a very special, but economically meaningful role for reaching climate-neutrality and in reliably making renewables available,” said Schuler. Whether a new “iron age” will actually emerge depends largely on how complex it is to retrofit existing power plants and how efficiently iron oxide can be reduced back to iron in the future. 
 

Original Publication
Julia Schuler, Armin Ardone, Viktor Slednev, Wolf Fichtner: A new iron age? The potential role of iron fuel in Europe’s clean energy transition. Chem Circularity, 2026. DOI: 10.1016/j.checir.2026.100047

The PERSEUS-PtX energy system model extended in this project, including its source code, dataset, and an extensive description, is accessible to the public for free, non-commercial use: https://zenodo.org/records/19480835 

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