Dynamic Operation of an AEM Electrolysis System

Today, alkaline electrolysis (AEL) and proton exchange membrane (PEM) electrolysis represent the most relevant low temperature electrolysis technologies. However, anion exchange membrane (AEM) electrolysis is emerging as a promising technology that combines the advantages of the alkaline environment with the advantages of using an active membrane instead of a diaphragm. For instance, both the use of rare iridium in the anode and fluorine-containing membranes can be avoided with this technology. As the share of renewable energy in the electricity grid is increasing, the fluctuation of the electricity supply is getting more prominent. Consequently, the ability of an electrolyzer to adapt and meet these requirements of transient operation while maintaining a low degradation is of great importance for the viable success of hydrogen production in future energy systems. This study examines the experimental start-stop operation of an AEM electrolysis stack operated in a system environment. The measurements involve parameter variation and the optimization of the cold start procedure to decrease start-up duration while maintaining low degradation. Analyses with 150 cold starts per parameter set reveal that the degradation of the AEM electrolysis stack correlates with the steepness of the current slope during the voltage ramp-up. By applying a gentle start procedure, a degradation of 10 µV start-1 could be observed, while applying a substantially faster current increase results in degradation rates of 26 µV start-1 leading to a significantly decreased lifetime of the electrolyzer. The primary objective is to develop an in-depth understanding of the capabilities and limitations of an AEM electrolysis system regarding the entire transient operation including start and stop procedures.