Investigation of modeling challenges of PEM fuel cells cold start operation

In this study a one-dimensional transient isothermal model was implemented in MATLAB to conduct an in-depth evaluation of available modeling framework for cold start simulation of PEMFC. In this regard, several shortcomings were addressed and a combination of modifications introduced by other researchers and assumptions made in this study was used to improve modeling accuracy; reaction kinetics variation with temperature and ionomer water content was investigated and incorporated in the model; dynamics of nucleation and subcooling was described by Johnson-Mehl-Avrami-Kolmogorov (JMAK) and Classical Nucleation theories; effect of temperature on ECSA loss was examined and assumptions were made regarding electro-osmotic drag in catalyst layer under low load conditions. The results showed high fidelity to experiments in the early stage of cold start and the model was able to capture the effect of all three influential parameters, i.e. temperature, initial ionomer water content, and current density on performance evolution and failing time in isothermal cold starts with acceptable accuracy. Moreover, the linear performance drop at low subcooling and the nonlinear relation between cold start duration and initial ionomer water content were properly reproduced by the model.