An Optimised Multi-physics Model for Hydrogen Production in Alkaline Water Electrolysers

Alkaline water electrolysers are commonly employed for industrial-scale production of low-carbon hydrogen. Operating at high current densities leads to enhanced hydrogen production, but reduced cell efficiency, partly due to ohmic losses from bubble coverage of the electrode and reduced electrolyte conductivity. To gain further insights into the flow in electrochemical cells we carry out three-dimensional transient multi-physics simulations over a range of flow rates and current densities with the OpenFOAM libraries. We simulate the bubbly flow with a multi-fluid Eulerian model and consider electrochemistry, heat transfer, and bubble coalescence. Through a variance-based sensitivity analysis, we examine the impact of numerical parameter selection, with a focus on turbulence and interphase momentum-coupling models, and select a set of optimal parameters. The turbulent dispersion coefficient emerges as the parameter with the highest sensitivity index in all operating conditions, followed by the turbulence and drag models. Second-order sensitivity indices, which represent the sensitivity to parameter interactions, are significant for the bubble diameter and turbulence model. To address the uncertainty associated with the turbulence model and dispersion coefficients, we perform large-eddy simulations, allowing us to bridge the gap with RANS simulations typically used in industry.