Using iron to store hydrogen for the long term

The novel method is cost-effective and can be easily scaled

Spotted: Hydrogen and hydrogen-based fuels are now a central part of various nations’ net-zero plans, with 41 governments having formalised hydrogen strategies in place as of 2023. Despite this, production and usage of low-emission hydrogen lags behind where it needs to be to meet 2030 and 2050 targets. One of the key obstacles to widespread adoption is issues around storage, but researchers at ETH Zurich hope to change that.

Rather than traditional pressurised hydrogen tanks – which are expensive, energy-intensive, and rarely leak-proof – the scientists turned to the steam-iron process, using stainless steel reactors filled with iron ore. Once hydrogen is fed into the tank at 400 degrees Celsius, it reacts with oxygen in the iron ore to create water and leave pure iron behind.

According to the research lead Professor Wendelin Stark, this method would enable hydrogen to be stored for long periods without significant losses. The idea is that this storage system could be used to help hydrogen power plug the seasonal gap in renewable energy supply. During the summer months, solar power can be used to split water to produce the hydrogen that’s fed into the tanks. Then, during the winter when solar energy is less abundant, hot steam is fed into the containers to turn the components back into iron ore and hydrogen. At this point, the hydrogen is ready to be converted into electricity or heat in a turbine or fuel cell.

Although converting hydrogen does result in significant volumes of energy being lost in the process, this system could still be an attractive energy storage solution for situations where there’s abundant clean energy and limited means of storage. Unlike existing hydrogen storage tanks, the researchers’ process takes place at ambient temperature and doesn’t require any additional strengthening measures on the reactor. And because iron is easy to procure in large quantities, the system is affordable and easily scalable.

The team has already successfully demonstrated the system at a pilot plant on ETH Zurich’s Hönggerberg campus and the plan is that by 2026, the campus use the hydrogen storage system to meet a fifth of its winter electricity requirements using the solar power it generates during the summer.

Written By: Matilda Cox