Investigating Local Temperature and Related Parameters in Large Area Pemfcs through a Pseudo-3D Physic-Based Model

Local temperature and water balance have been proven to be critical not only for the performance but also for the durability of proton exchange membrane fuel cells [1]. On the one hand, a higher local temperature can induce not only membrane drying and performance loss but can also cause pinhole formation, which can exacerbate locally the degradation mechanisms. On the other hand, a lower local temperature can induce local flooding due to lower water saturation pressures and limit the reactant gas delivery to reaction sites. Furthermore, water phase change can induce deposits in the bipolar plate channels and accelerate corrosion mechanisms.

Different works have been conducted in order to investigate those parameters by experimentation (micro-fabrication-based sensors, printed circuit boards, neutron radiography, in-situ imaging techniques…) and/or by modeling [2]. Nevertheless, experimentation methods are limited by their invasiveness and low precision and/or resolution. Regarding the models, the great challenges remain to have access to the local physical conditions in the Membrane Electrode Assembly as well as the enlargement and better description of the studied geometrical domain while maintaining an acceptable computational time.

In order to address those challenges, in this work a pseudo-3D physic based model has been developed at the cell scale (220 cm²) and validated against in situdata obtained from a local measurement device (S++ Current Scan Lin [3] which allows mapping the current density and temperature distribution in the bipolar plates with an acceptable resolution) inserted in the middle of a home-made 30 cells stack. Given the aspect ratio of the different cell components, the idea of the pseudo-3D approach is to consider each component as a plane layer, which is coupled to the other components through appropriate exchange conditions. With this approach, it is thus possible to compute the 2D (in-plane) distribution of the different physical parameters (temperature, species concentration…) in each cell component (active layers, gas diffusion layers, membrane, bipolar plates, cooling circuit…) at a reasonable cost. The model takes into account the thermal effects, the species transport and the electrochemical behavior of the electrodes. It is implemented in the software Comsol Multiphysics.

The simulation results highlight different zones where temperature and linked parameters, such as humidity, have extreme values causing notably lower local performance or increasing risks of water flooding. The model can be used to study the correlation between the observed degradations and the local conditions inside the cell (temperature, relative humidity, concentrations, water fluxes…) and so optimize the design of the bipolar plates. 

[1]  K. Panha et al. Accelerated durability testing via reactants relative humidity cycling on PEM fuel cells, Applied Energy 93 (2012) 90 -97

[2]  A. Bıyıkoglu. Review of proton exchange membrane fuel cell models, International Journal of Hydrogen Energy 30 (2005) 1181 – 1212

[3]  S++ Simulation Services, Waldstraße 5, 82418 Murnau-Westried, Germany. www.splusplus.com

Figure 1: Comparison between the simulated and the measured temperature in the sensor plate – Prediction of the temperature and water content in the different components of the cell