Transient behaviors and mathematical model of proton exchange membrane electrolyzer

The transient characteristics of proton exchange membrane water electrolysis for hydrogen production are crucial for the study of the load control and durability of the electrolyzer under the fluctuating conditions of renewable energy sources. In this study, a dynamic model of the electrolyzer is established based on various equivalence theories used to describe the transient characteristics of the electrolyzer during operation. Differential-equation-based transient models of the RC (resistance and capacitance) equivalent circuit and the equivalent controlled current source, their advantages and disadvantages, and their typical transient response spectra are presented. Among these, the graphical method based on the polarization curve is recommended because it has the advantages of intuitive and simple expression and can help researchers precisely and efficiently predict the response form and time of current or voltage using various control methods. The transient characteristics of the shutdown process reflect electrochemical processes similar to those of fuel cells in the electrolyzer during the OCV (open circuit voltage) period. The performance of the transient process is related to the structure of the electrolyzer and the operating conditions of the measurement. Low-voltage sustenance with manual intervention following shutdown may have a positive effect on the durability of the electrolyzer.