Numerical Study of the Cold-Start Process of PEM Fuel Cells with Different Current Density Operating Modes

Abstract

A 1D transient model was proposed to investigate the effects of the current density operating modes on the cold-start process of proton exchange membrane (PEM) fuel cells. The temperature evolution of the cell is solved by considering the reversible heat, reaction heat, Joule heat, and phase change heat. Four current density operating modes were studied based on this model: constant mode, gradually increasing mode, stepwise increasing mode, and zigzag mode. The results show that there is a threshold for the initial current density that influences the relationship between the successful cold start and current density. The cell can successfully start at a lower operating temperature by increasing the initial current density when the initial current density is below this threshold value. However, the lowest temperature for successful cold start increases if the initial current density exceeds the threshold value. Finally, a chart was plotted to indicate the regions of successful and failed self-start processes at different operating temperatures for the studied current density operating modes, respectively. The chart suggests that the cells with gradually and stepwise increasing current density modes have nearly equivalent cold-start performance, and are both better than the constant and zigzag modes.