Mathematical model and characterization of the transient behavior of a PEM fuel cell

Modeling of fuel cells is getting more and more important as powerful fuel cell stacks are getting available and have to be integrated into power systems. In this paper, the governing equations of the transient behavior of a proton exchange membrane fuel cell are presented. They show the influence of the operating conditions and the current density on internal parameters, especially the ohmic resistance. A method and specially designed electronic load are presented for in-situ membrane resistance measurements. This resistance is plotted in transient operation during parameter changes and current variations. The results are compared to the simulated values to explain the internal phenomena of the fuel cell. Special attention is given to the water management, one of the most important challenges in low temperature fuel cell operation where drying or flooding can decrease the performance or even lead to destruction.