Simple PEM water electrolyser model and experimental validation

We propose in this work a simple model for atmospheric or low-pressure PEM water electrolysers, which allows for simulating the electrochemical, thermal and H-2 output flow behaviours with enough precision for engineering applications. The model has been validated by good agreement with experimental measurements performed in two different electrolysers. The electrochemical submodel allows for obtaining the operating stack voltage from the input current and the stack temperature conditions. After non-linear fitting and statistical analysis from experimental data we conclude that the electrochemical submodel can be extrapolated for any PEM water electrolyser knowing two parameters with physical meaning: activation energy of the "water oxidation" for the anode electrocatalyst and the activation energy for proton transport in the solid polymer membrane. This submodel was validated with experimental polarisation curves at different temperatures from two different PEM water electrolysers. The standard error of the model was less than 0.03. The results showed that the worst values of the estimation were obtained below 50 degrees C, indicating that the assumption of constant anode charge transfer coefficient is not true at lower temperature, which is in accordance with recent results. In order to complete the electrochemical submodel, a practical methodology is presented here to obtain simple semi-empirical submodels for the H-2 production and thermal behaviours for this kind of electrolysers. Both submodels are also discussed based on the experimental validations. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.