A Three-Dimensional, Multiphysics Model of An Alkaline Electrolyzer

During the previous years, increasing awareness of the detrimental effects of greenhouse gas emissions along with the need to supply an increasing world population with electricity has given rise to investments in the field of green energy technology. In particular, research and development has focused on the production of “green hydrogen” which can be used as a source for a sustainable energy system. Green hydrogen can be made from water electrolysis provided the electricity stems from a renewable energy source. Among the different types of water electrolysers, the alkaline electrolyzer cell (AEC) is the most mature technology. Among its advantages compared to other technologies are the low capital expenditure and the simplicity of the system with proven components. However, the detailed heat and mass transfer mechanisms that occur in an AEC are far from completely understood. It is expected that further improvements of the technology and reduction in cost can be attained through a fundamental understanding of above-mentioned phenomena. In order to better understand the phenomena and the physics of such system, a numerical model is developed in this project. Using ANSYS Fluent 2021 R1, an isothermal, single phase, three-dimensional model is developed to replicate the phenomena in a small single cell. Equations such as Butler-Volmer and Nernst Equation are considered to describe the electrochemical part of the system. A simplified Nernst-Planck equation is also modelled to account with the diffusion and migration of charged species (in this case, the ion OH-). The flow is considered laminar, and the species conservation equation are written to solve the molar concentration of each species. The porosity of the electrodes is changed along the simulations to study its influence on the performance of the electrolyzer. Also, the initial concentration of the species is changed in order to evaluate its effect on the output of the system. First results suggest that the polarization curve acquired shows a strong consistency with prior experimental findings and outcomes from other simulation models. Figure 1