Characterisation of a PEM electrolyser using the current interrupt method

Abstract

The need to characterise a PEM electrolyser is motivated by a South African hydrogen company. One of two electrochemical characterisation methods, namely the current interrupt method or electrochemical impedance spectroscopy, is investigated to characterise the PEM electrolyser. Various literature sources can be found on the electrochemical characterisation methods. In this study the current interrupt method is used for the electrochemical characterisation of a PEM electrolyser. The current interrupt method is an electrical test method that will be used to obtain an equivalent electric circuit model of the PEM electrolyser. The equivalent electric circuit model relates to various electrochemical characteristics such as the activation losses, the ohmic losses and the concentration losses. Two variants of the current interrupt method, namely the natural voltage response method and the current switching method, are presented. These methods are used to obtain two different equivalent electric circuit models of the PEM electrolyser. The parameters of the first equivalent electric circuit, namely the Randles cell, will be estimated with the natural voltage response method. The parameters of the second equivalent electric circuit, namely the Randles-Warburg cell, will be estimated with the current switching method. Simulation models of the equivalent electric circuits are developed and tested. The simulation models are used to verify and validate the natural voltage response method and the current switching method. The parameters of the Randles cell simulation model is accurately calculated with the natural voltage response method. The parameters of the Randles-Warburg cell simulation model is accurately calculated with the current switching method. The natural voltage response method and the current switching method are also practically implemented. The results is used to indicate the various electrochemical characteristics of the PEM electrolyser. A Nafion 117 type membrane was tested with the current interrupt method. The membrane resistance parameters of Randles cell were estimated with the natural voltage response method. These values are validated with conductivity measurements found in literature. The results of the Randles- Warburg cell is validated with a system identification validation model.