Electricity storage and H2 producer at the same time: The Fraunhofer IZM project "Zn-H2" is developing a low-cost zinc battery that can both store energy and produce hydrogen. Initial tests indicate an efficiency of up to 50 % for electricity storage and 80 % for hydrogen production. The miracle battery is expected to last ten years.
A consortium of research institutions and the companies Zn2H2 GmbH and Steel PRO Maschinenbau GmbH want to store green energy in the Zn-H2 project. The goal is a long-lasting battery that is suitable for long-term storage. Based on established solutions in the battery sector with zinc anode, the researchers are combining this technology with alkaline water electrolysis in an attempt to develop a new storage technology.
Zinc storage batteries are cheaper than conventional lithium batteries. They also use readily available raw materials (steel, zinc, potassium hydroxide) and are considered recyclable. Electrically rechargeable hydrogen storage systems are designed to store energy in the form of metallic zinc and provide electricity and hydrogen on demand.
Details of the demonstrator
A demonstrator is to be created by the end of the year. In the final stage, the researchers want to electrically connect eight cells with a capacity of approximately 12 V and 50 Ah. Electroplating is a cost-effective production technique for the large-scale manufacture of the bifunctional catalyst, which alternates between hydrogen and oxygen.
The team at Fraunhofer IZM in Berlin is responsible for designing the demonstrator, setting up a test stand and conducting the reliability tests. Since this type of zinc-hydrogen storage is unique to date, they have developed a corresponding test environment. For this, a high-precision intelligent control system is used to adjust and optimise different parameters.
According to the researchers, the first tests show: In realistic use during seasonal dark breaks, but also in daily use as solar storage, the catalysts have a service life of more than ten years. However, the system still has to go through several stages of up-scaling before it is finally suitable for industrial use.
Properties of the zinc battery
Project coordinator Dr Robert Hahn from Fraunhofer IZM explains: "During charging, water in the battery oxidises to oxygen, and at the same time zinc oxide is reduced to metallic zinc. When the storage cell is discharged as needed, the zinc is converted back into zinc oxide. The water is reduced again, so that hydrogen is produced and released. The result is a unique combination of battery and hydrogen production with an overall electricity storage efficiency of 50 %, which means we outperform the alternative and currently favoured power-to-gas technology twice over."
Since the material costs are less than one tenth of a lithium battery, this opens up an economically attractive perspective for storing green energy.
Source: Fraunhofer IZM/2023
