Design and testing of a compact PEM electrolyzer system

A compact prototype system for H2 production based on a Polymer Electrolyte Membrane (PEM) stack was developed and investigated. A detailed study and an optimization of the Balance of Plant (BoP) was carried out. The system was developed in laboratory by using commercial devices tailored around in house-made membrane electrode assemblies (MEAs). The study regarded both the hydraulic circuit efficiency loss and its optimization by varying process parameters. Energy consumption for auxiliary devices was studied at different temperatures (40, 60 and 75 °C). Efficiency and control strategy management of the system were investigated. Despite an increase of stack performance observed at high temperature, maximum system efficiency (65% compared to HHV) was obtained at 40 °C because of moderate energy consumption by the electric heater. To evaluate the stack contribution to the overall efficiency, the present investigation was completed by a hydrodynamic study of the stack inside the system. Diffusional aspects related to the water mass distribution inside the stack were investigated through a computational fluid dynamic analysis (CFD). In particular, a 3D analysis of the whole stack composed by 120 channels and 10 cells was carried out. The model showed a quite uniform distribution of water over the individual channels and a homogeneous pressure inside the cells. Accordingly, the risk of having hot spots and gases accumulated inside the stack was minimal.