Experimental and modeling study on energy flow of 250 kW alkaline water electrolysis system under steady state conditions and cold start process

Improving the energy utilization efficiency of alkaline water electrolysis system (AWE) is one of the urgent problems at this stage. This study explores the heat flow and energy distribution under steady state and cold start processes by establishing a multi-physical field coupled AWE system model including heat transfer, mass transfer and electrochemistry, based on this, the methods to improve energy utilization efficiency are proposed. The system power consumption at full load is 272.7 kW, the electrolyzer accounts for up to 88.4%, of which, the useless heat production and parasitic current are the main factors that cause the electrolyzer energy loss, accounting for 21.2% and 3.1% of the total power consumption, respectively. The electrolyzer useless heat production also significantly contributes to the chiller energy consumption, which accounts for 5% of the system power consumption. Improving the electrolyzer performance and minimizing its heat production is essential to optimize the system efficiency. During the AWE cold start process, the constant voltage control has a shorter cold start time than the constant current control, but their power consumption differences in terms of heat and hydrogen production are small. Reducing the system thermal capacity is extremely effective in speeding up the cold start process compared to optimizing the power load type, which can cut the cold start time to less than 1 h.