21 October 2025
Every year, vast quantities of renewable energy are lost in Germany. In 2022 alone, over eight terawatt hours had to be curtailed — enough electricity to power over two million households. However, even energy that is not curtailed often cannot be put to good use. Due to a lack of seasonal storage options, it is sold on the electricity market at very low prices, sometimes even at negative prices. This is due to a fundamental imbalance: while more electricity is generated than consumed in summer, there is a shortage of energy in winter. Until now, there have been no affordable technologies available to store these seasonal surpluses long term and make them available as needed. This is precisely the issue that the new H2Season project aims to address.
Scientists at the Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN) are developing an innovative concept for seasonal energy storage involving the reversible electrochemical storage of hydrogen in the liquid hydrogen carrier acetone/isopropanol (LOHCs — Liquid Organic Hydrogen Carriers). Green hydrogen is electrochemically bound to acetone to produce isopropanol. These molecules are non-toxic, inexpensive and industrially available, and can be safely stored in conventional plastic tanks. If necessary, the hydrogen can be released again through electrochemical dehydrogenation, and the acetone produced in this process can be returned to the storage tanks for the next cycle.
The technology developed in Prof. Simon Thiele's department has the potential not only for low material and operating costs, but also for a wide range of applications. The electrochemical reactors used for hydrogenation and dehydrogenation are compatible with a variety of existing and future energy systems, as they can be used independently of the electrolysis or fuel cell technology employed. The concept is also promising from an economic perspective. The technology achieves round-trip efficiencies of up to 40%, comparable to pressurised hydrogen storage systems but at a fraction of the cost of battery storage systems.
H2Season, which is funded by the Bavarian State Ministry of Economic Affairs, Regional Development and Energy (StMWi), is scheduled to run for three and a half years and comprises three closely interlinked subprojects. The focus is on developing, scaling up and integrating the new electrochemical hydrogen storage technology into a practical demonstrator that will test the technology under real-world conditions.
The project aims to develop a market-ready storage system that is safe and economical — and thus make a decisive contribution to the energy independence and climate neutrality of rural businesses, as well as Germany and Europe.
H2Season builds on the intensive preparatory work of the previous project, 'Emissions-free and greatly reduced-emission rail transport on non-electrified lines', which was also funded by the StMWi.
There, the electrochemical dehydrogenation of acetone/isopropanol was investigated in depth. In several publications, scientists at HI ERN analysed the technological potential and challenges of electrochemical cells using isopropanol as a carrier medium. A follow-up study demonstrated the basic feasibility of electrochemical hydrogenation and dehydrogenation. Key parameters such as fuel concentration, temperature and mixing ratios were investigated in detail, and cell performance and energy efficiency were demonstrated under realistic conditions. Overall, the results showed very high current densities at low voltages. This shows the potential for compact, cost-effective systems that require minimal energy for hydrogen storage and supply.
Experience the first H2Season prototype live! At the "Lange Nacht der Wissenschaften" (Long Night of Science) at our "Auf AEG" site in Nuremberg. More
