At a pilot plant in Switzerland, researchers from ETH Zurich are demonstrating how iron can be used to reliably and safely store hydrogen for months, paving the way for a new system of seasonal energy storage
Storing Hydrogen in Iron: A Feasible Solution?
From Switzerland’s ETH Zurich comes a new long-term hydrogen storage system that is safe, cost-effective, and efficient. The secret to its success lies in a common and readily available element: iron. Led by Professor Wendelin Stark, a team of scientists from the Department of Chemistry and Biosciences has revived a 19th-century process, giving it new purpose. The result is a hydrogen-based system stored in iron, capable of preserving solar energy captured during the summer for use in winter.
But to grasp the significance of this study, let’s take a step back
How to Store Hydrogen for Long Periods
Hydrogen as a Storage Solution for Renewable Energy. Using hydrogen as a storage system for intermittent renewable energy is one of the major trends in the energy transition. However, for it to be commercially viable, hydrogen must be stored safely and cost-effectively over long periods. Unfortunately, the most widely used storage technologies today are physical methods, involving pressurized containers, natural formations, and cooling processes. These methods are energy-intensive and carry certain risks.
The most promising alternative? Chemical hydrogen storage. In recent years, liquid organic hydrogen carriers (LOHCs) have shown particular promise in this field. These carriers can chemically trap and then release hydrogen molecules through completely reversible cycles. The challenge, however, lies in identifying the perfect LOHC among the billions of compounds potentially suitable for this purpose.
ETH Zurich Unveils Cutting-Edge Iron-Hydrogen-Water Battery
In the realm of hydrogen storage, ETH Zurich’s approach stands out for its solidity—both figuratively and literally. Drawing inspiration from an 18th-century method of hydrogen production using iron and steam, the team has revamped this concept. Originally developed in 1784, the old technique generated hydrogen by passing steam over a bed of red-hot iron at 600°C. This process was later replaced by steam reforming.
The new system devised by ETH Zurich’s scientists uses green hydrogen (produced from renewable sources) and introduces it into a stainless steel reactor filled with iron oxide at 400°C. In this setup, hydrogen extracts oxygen from the iron ore, resulting in elemental iron and water. To retrieve the stored energy, the process is simply reversed by introducing steam into the reactor to produce iron oxide and hydrogen. To minimize energy consumption, the steam is generated using the waste heat from the discharge reaction.
A full-scale prototype for storing hydrogen in iron.
According to the researchers, the reactor operates at ambient pressure and does not require special safety measures.
A full-scale prototype for iron-based hydrogen storage has been tested at ETH’s Hönggerberg campus, utilizing three stainless steel reactors. Each reactor has a capacity of 1.4 cubic meters and is filled with 2-3 tons of iron ore. This demonstration plant can store approximately 10 MWh of hydrogen for extended periods. “Depending on how the hydrogen is converted into electricity, you can expect to generate between 4 and 6 MWh of electricity,” explains Samuel Heiniger, one of the researchers involved. The study has been published in Sustainable Energy & Fuels 2024.
