A One-Dimensional Computational Model to Study Dehydration Effects in Polymer Electrolyte Fuel Cells

摘要

The performance of Polymer Electrolyte Fuel Cells (PEFCs) is highly dependent on the water content of the Membrane-Electrode Assembly (MEA). In particular, under transient operating conditions as can be found in mobile applications partial dehydration at the membrane-anode interface may occur. This leads to an increasing resistance and therefore to a higher potential drop which may cause a significant loss in power supply, which clearly is unacceptable in terms of driving comfort. A number of theoretical and experimental studies have been performed in the past concerning this problem. However, so far no adequate theoretical model existed to understand and to analyse in detail the physical phenomena associated with fuel cell dehydration. Therefore the objective of this paper is to present a one-dimensional (1D) model for a PEFC which tries to overcome the aforementioned limitations. Electric osmotic drag of water molecules in the membrane as well as a counterflow due to the concentration gradient between anode and cathode are part of the model. It is shown, that the sum of these two flows determines a water content gradient, which causes a decline in current-voltage performance, especially at higher currents. Typical membrane parameters like thickness, conductivity, permeability coefficients, etc. are varied to study in detail how they are linked to each other and how they influence the power output of the cell. Finally it is shown, that the computational results achieved so far are in good agreement with experimental data and are in line with previous simulation results.