ETH researchers are using iron to store hydrogen safely and for the long term. The technology could be used for seasonal energy storage in the future.
The charging and discharging process of the storage technology - Graphic: ETH Zurich
In order to store hydrogen more effectively, they are relying on the iron-steam process, which has been known since the 19th century. If there is too much solar power available in the summer months, water can be split to produce hydrogen. This hydrogen is then fed into a 400 °C stainless steel boiler filled with natural iron ore. There, the hydrogen extracts the oxygen from the iron ore - which is chemically nothing more than iron oxide - producing elemental iron and water. If the energy is needed again in winter, the researchers reverse the process: They feed hot steam into the boiler, which turns the iron and water back into iron oxide and hydrogen. The hydrogen can then be converted into electricity or heat in a gas turbine or fuel cell. In order to use as little energy as possible for the discharging process, the waste heat from the discharging reaction is used to generate the water vapor. However, the use of hydrogen also has a disadvantage: its production and conversion are inefficient compared to other energy sources, as up to 60 % of the energy is lost in the process. Hydrogen is therefore particularly interesting as a storage medium when sufficient wind or solar power is available and other options are out of the question. This is particularly the case for industrial processes that cannot be electrified. The pilot plant is to be expanded by 2026 to cover a fifth of the Hönggerberg campus's electricity requirements with solar power in winter.
