Efficiency Analysis based on a Balance of Plant Model for a Modular Electrolysis System

Green hydrogen produced by electrolysis using renewable power is a promising technology for long term energy storage. The efficiency of electrolysis systems depends not only on the stack efficiency, but also on the auxiliary plant components. This paper proposes a balance of plant model of a small-scale modular anion exchange membrane electrolysis system. The model considers the energy consumption of all peripheral devices necessary for hydrogen production and storage, that is, hydrogen dryer, water tank, external cooling circuit pump, gas warning system, control system, fans for ventilation, air conditioning unit and hydrogen compressor. In addition, hydrogen losses due to crossover, purging and regeneration of the hydrogen dryer are considered. Efficiencies are analyzed for steady operation and for an intermittent power load. Additionally, an experimental characterization of a single electrolyzer module is performed.