Experimental studies and modeling of a 250-kW alkaline water electrolyzer for hydrogen production

Well-matured alkaline water electrolysis is considered as the most favorable method for cost-effective production of green hydrogen using renewable energy. In this study, a 250-kW pressurized alkaline water electrolyzer has been operated and observed, through modified procedures, as part of a wind-to-hydrogen demonstration project. Cold start from an idle state to rated hydrogen production state requires more than 6 h. A semi-empirical model is proposed to describe the behavior of the real-scale alkaline electrolyzer system. The cell voltage and gas purity of the electrolyzer are considered as functions of operating pressure, temperature, and current density. The model parameters have been adjusted using a non-linear regression, based on experimental data taken from varying operating conditions. The simulated and measured cell voltages are compatible with each other, with a maximum error of 30 mV, and the relative error evaluated for the hydrogen impurities in oxygen is lower than 3.9%. Simulation results reveals that efficiency and safety are significantly affected by the operating conditions. Meanwhile, the model is further experimentally validated with wind-to-hydrogen demonstration test results. The proposed model is a helpful tool in designing and optimizing control strategies of alkaline electrolyzers, coupled with renewable energy sources. • The 250 kW electrolyzer was operated and characterized with modified procedure. • The cold start from idle to normal state was observed on the scale of hours time. • The electrolyzer displayed load following capability during wind-to-H 2 demonstration. • A semi-physical model is developed considering operating pressure and temperature. • The model is parametrized and validated with peformance and demonstration test data.