Iron-based hydrogen storage process unveiled by ETH Zurich

Researchers at ETH Zurich have reported a method to “safely and securely” store hydrogen in iron for extended periods.

Located at a pilot plant on ETH Zurich’s Hönggerberg campus in Switzerland, the technology feeds hydrogen into a stainless steel reactor filled with natural iron ore at 400°C. The hydrogen then extracts the oxygen from the iron ore resulting in elemental iron and water.

When energy is needed again in the winter, researchers reverse the process and feed hot steam into the reactor to turn the iron and water back into iron oxide and hydrogen, with the latter converted into electricity or heat in a gas turbine or fuel cell.

Whilst it is capable of storing up to 10MWh of hydrogen, up to 60% of hydrogen’s energy is lost in the plant, meaning it is most attractively used as a storage medium when wind or solar power is available and other options are not.

Researchers at ETH Zurich plan to expand the pilot plant by 2026, so it can meet one-fifth of its winter electricity requirements using its own solar power from the summer. This will require reactors with a volume of 2,000 metres which could store around 4GWh of green hydrogen.

Wendelin Stark, Professor of Functional Materials at the Department of Chemistry and Applied Biosciences, claimed the plant could replace a small reservoir in the Alps as a seasonal energy storage facility.

Regarding technology, Stark said, “This chemical process is similar to charging a battery. It means that the energy in the hydrogen can be stored as iron and water for long periods with almost no losses.

“The big advantage of this technology is that the raw material, iron ore, is easy to procure in large quantities. Plus, it doesn’t even need processing before we put it in the reactor.”

The pilot plant project, which is part of ETH’s Coalition for Green Energy and Storage, is expected to support Switzerland’s Net Zero ambitions.