Modelling and analysis of multiphysics transport processes in proton exchange membrane electrolysis cell under marine motions

Electrolytic hydrogen production is energy intensive. Offshore power generation methods may have excess power that could be used for “green” hydrogen production. However, waves and wind cause marine motion, which may affect the electrolysis performance of proton membrane exchange electrolysis cells (PEMECs) by affecting the gas-water multiphase flow within these cells. In this study, a model of multiphase transport and electrochemical reactions in a PEMEC was developed and used to investigate the cell's performance under six marine motions: pitch, roll, yaw, heave, surge, and sway. The oxygen distribution and current density in the PEMEC anode were obtained for both single and superimposed motions. The motion effects were mainly attributable to the differing viscosity/inertia of oxygen and water. The movement of gaseous oxygen with low viscosity was found to be dominated by inertial forces, whereas high-viscosity water moved with the cell. Thus, the oxygen lagged behind the water, resulting in uneven distributions, particularly for rotational motion. For example, the oxygen concentration varied greatly within the cell during pitch (0.012–0.035 kmol/m3), and the electrolysis current density was 13.3 % lower than when motionless. Surge further increased the nonuniformity of the oxygen distribution (0.01–0.04 kmol/m3) and reduced the current density (4750–9210 A/m2). However, heave along the cell thickness direction improved oxygen diffusion, resulting in 37.5 %−72.4 % lower oxygen concentrations than in other cases. In particular, the oxygen gradient was 60 % lower with surge, pitch, and heave than for surge and pitch.