A new method for acquiring temporal and spatially resolved electrochemical impedance spectroscopy data on a segmented proton exchange membrane fuel cell is developed. The cell used in this study consists of a segmented anode with 20 galvanically insulated segments. By measuring all segments simultaneously, restricting the frequency range, imposing all frequencies within one measuring task, and decoupling the acquisition and post-processing steps, we can reduce the acquisition time to 1 second. The results yield the spatial and temporal evolution of the TLM’s parameters, e.g., membrane resistance Rmem. Our results show that the temporal evolution of local Rmem strongly differs from the temporal evolution of the global Rmem. Moreover, we can see strong differences in the temporal evolution of local Rmem. The results further indicate that re-humidification after a decrease of stoichiometry appears almost instantly, while after an increase of stoichiometry it takes several minutes until the cell is dried out and equilibrated again. Furthermore, we can show, that the ratio of the 1 kHz resistance R1kHz to Rmem locally changes over time, making it an unsuitable substitute for Rmem. We therefore suggest R1kHz not to be taken as an indicator or substitute for Rmem.
This paper is devoted to the modeling of a PEMFC fuel cell stack. First, to justify the hypotheses, original experimental results are presented and show that the gas flow rates feeding a cell in its stack environment highly depend on the thermal management. Then, the generic model of a cell in its stack environment is presented. A two-phase flow model is implemented to calculate the gas flow rates as a function of the pressure drops and considering the amount of liquid water present in both compartments. In this way, the dispatching of the total active gases flow rate between the different cells can therefore be described. Finally, a stack of five cells is numerically assembled by describing the thermal coupling between the cells. Two application examples are conducted. A first one considers a cooling defect and a second one simulates the case where one cell is more degraded than the others. It is shown how these types of malfunction can cause a fuel starvation event. At the end, and for the first time as far as we know, a mechanism of propagation of degradations from cell to cell is proposed. List of symbols SymbolDescriptionUnitSymbolDescriptionUnit Double-layer capacity of the cellF Protonic resistance of the membrane and electrodesΩ water vapor concentrationmol m−3 Thermal resistanceK W−1 Oxygen Concentrationmol m−3 Mass transfer reisstances m−3 Concentration of the saturated vapor at T mol m−3 Water saturation in the channels Specific heat capacity of plateJ/K.kg TemperatureK Effective water vapor diffusion coefficient through the GDLm2 s−1 Cell potentialV Water diffusion coefficient in the membranem2 s−1 Volume of channels m3 Effective oxygen diffusion coefficient through the GDLm2 s−1 Greek Letters Thickness of the GDLm Anodic charge transfer coefficient Standard cell potentialV Cathodic charge transfer coefficient Equivalent weight of the membranekg mol−1 Roughness factor of the electrode Faraday constantC mol−1 Pressure dropPa Current intensityA Electro-osmosis coefficient Exchange current densityA m−2 Water content of the membrane thermal capacity of the MEAJ K−1 Effective thermal conductivity of GDLW mK−1 thermal capacity of the anode/cathode platesJ K−1 Volumetric masskg m−3 Length of the active aream Cathode electrode potentialV Water latent heatkJ mol−1 Upper & lower scripts lower heating value of HydrogenkJ mol−1 in Inlet Molar mass of waterkg mol−1 out Outlet Dry air molar flow ratemol s−1 c Cathode Dry hydrogen molar flow ratemol s−1 a Anode Water vapor molar flow ratemol s−1 ch Channels Water vapor flow rate from electrode to channelsmol s−1 el Electrode Atmospheric pressuremol s−1 m Membrane Total pressure in the anode channelsPa cf Cooling fluid Total pressure in the cathode channelsPa n−1Preceding electrode Universal gas constantJ mol.K−1 n + 1Following electrode Electrical resistance of the cellΩ
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.