Investigation of the operation characteristics and optimization of an alkaline water electrolysis system at high temperature and a high current density

Increasing the operating temperature of water electrolysis is an effective way to improve its performance. When the available region of the operating current density is extended, the stack can generate an increased amount of hydrogen. This can directly contribute to green hydrogen being highly competitive compared to other kinds of hydrogen. In this study, numerical analysis was conducted to investigate and optimize the operational characteristics of alkaline water electrolysis (AWE) under high temperature and high current density conditions. The numerical model of the AWE developed in our previous study has been upgraded by considering the crossover of hydrogen gas through the membrane to more accurately determine the Faraday efficiency of hydrogen production and the available safe operating range. Simulation results show that saturated vapor generation significantly affected the performance of both stack and system components in high-temperature environments. Therefore, pressurization is important to ensure the high efficiency of high-temperature water electrolysis, but it must be appropriately adjusted in consideration of gas crossover. In this study, the highest efficiency of 78.52% was captured at 120 °C and 10 bar for 1 A/cm2 operation.