Green hydrogen, produced through water electrolysers powered by renewable energy, is becoming a key element in decarbonizing future energy systems. Scaling-up alkaline water electrolyser (AWE) stacks by adding series-connected cells, and increasing the operating voltage (1000 V–1500 V) can reduce the capital cost of electrolyser system and improve the energy efficiency of AC–DC power converters. However, scaling-up AWE stacks is limited by shunt currents. Therefore, series connection of multiple substacks is considered a promising approach to improve scalability, elevate voltage level, and mitigate shunt currents of the electrolyser. This study focuses on developing the equivalent circuit model of series-connected substack system, consisting of isolated electrolyte circulation, and shared electrolyte circulation. Single-stack model, verified with measurement data from an industrial AWE, served as foundation for this research. Both configurations of AWE substack system are compared in terms of shunt currents and specific energy consumption. Additionally, this research investigates the impact of number of series-connected substacks and various lengths of external-ports on shunt currents in the AWE. Dividing a long electrolyser stack into shorter substacks significantly decreases shunt currents. Successful implementation of series-connected substacks requires careful consideration of current efficiency, pressure drop in the electrolyte circulation, and capital cost of the AWE system. • Series-connected AWE stacks with isolated and shared electrolyte circuit are studied. • Modeling of series-connected substacks is developed using a resistive network. • Dividing an AWE stack into series-connected substacks improves current efficiency. • External shunt currents can be reduced by increasing the length of external-ports.
Hysa et al. (Tue,) studied this question.
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