Electrical-thermal-electrochemical insights of the PEMWE stack in the accelerated stress test protocol powered by renewable energy

Abstract

Hydrogen production by proton exchange membrane water electrolysis (PEMWE) is considered a pivotal technology for renewable energy storage, utilization and conversion. In this study, based on one-year output data of photovoltaic (PV) and wind power (WP) generation in North China region, a K-means clustering algorithm was employed to extract the typical working conditions of PV and WP. The accelerated stress test (AST) protocols applicable to PEMWE stacks were proposed. Using the cell voltage monitoring (CVM) and cell temperature monitoring (CTM) devices, the voltage-temperature variations and transient response characteristics of a 10-cell PEMWE stack were experimentally investigated under steady-state, PV-AST and WP-AST conditions. Evaluation indexes were introduced to quantify the electrical-thermal consistency during 100-hour of continuous operation. The results indicate that stack performance degradation is relatively modest under steady-state testing, while significant performance degradation and electrical-thermal consistency deterioration are observed under AST fluctuating conditions. Electrochemical analysis using Electrochemical Impedance Spectroscopy-Distribution of Relaxation Times (EIS-DRT) revealed increased impedance in various electrochemical processes after 100 h of continuous testing, with more pronounced hindrance observed under AST conditions. Additionally, micro-morphological characterization identified evident material defects and degradation are witnessed in the catalyst coated membrane (CCM) after AST conditions, indicating severer cell failure due to frequent start-up/shut-down cycles and power fluctuations. These efforts contribute to clarify the electrical-thermal-electrochemical characteristics and degradation mechanisms of PEMWE stacks during long-term operations powered by renewable energy.