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This study presents a review of prognostic methods applied to automotive proton exchange membrane fuel cell (PEMFC). PEMFC durability is strongly affected when it is subjected to automotive load cycling (ALC). ALC is normally composed of four operation modes such as start‐up, idle, transient high‐current demand and shutdown. All of these operation modes drastically change the internal variables of the system like temperature, pressure, relative humidity etc. causing degradation of the fuel cell components in a short time. Prognostic methods could be a possible solution to tackle the PEMFC's low durability issue because they allow predicting the remaining useful life of the system in order to apply preventive maintenance plans. Therefore, the objective of this study is to review the prognostic techniques applied to PEMFC under ALC. In the first part of this study, a summary of PEMFC degradation mechanisms caused by ALC is realised based on literature review. In the second part, the prognostic methods review for automotive PEMFCs is carried out and a general synthesis and future challenges are given in the third part of the study. [ABSTRACT FROM AUTHOR]

This work proposes a state observer as a tool to manage cost and durability issues for PEMFC (Proton Exchange Membrane Fuel Cell) in automotive applications. Based on a dead-end anode architecture, the observer estimates the nitrogen build-up in the anode side, as well as relative humidities in the channels. These estimated parameters can then be used at fuel cell management level to enhance the durability of the stack. This observer is based on transport equations through the membrane and it reconstructs the behavior of the water and nitrogen inside the channels without the need of additional humidity sensors to correct the estimate. The convergence of the output variables is proved with Lyapunov theory for dynamic operating conditions. The validation is made with a high-fidelity model running a WLTC (Worldwide harmonized Light vehicles Test Cycle). This observer provides the average values of nitrogen and relative humidities with sufficient precision to be used in a global real-time control scheme. [ABSTRACT FROM AUTHOR]

In this work, a PEM fuel cell 2D + 1D model has been developed to investigate the heterogeneities existing at the surface of a cell. A study on the effects of the operating conditions is carried out. The fuel cell behavior is monitored through its interactions with local conditions thanks to the model. A GDL structuring and its effect on local conditions are also analyzed. The model has been confronted with stack test results in several operating conditions with an in-situ device. The comparison in three very distinctive humidity regimes (dry, mid-hydrated, fully hydrated) between the model and the measures for two local conditions (current density and temperature distributions) has enabled to validate the model and its approach. Other local conditions computed by the model but hardly reachable in real life have then been examined to better understand the cell's electrochemical behavior. In particular, temperature distribution measurements show that three hot spots exist at the cell surface, being located where the cooling fluid reaches a low velocity for a given bipolar plates' design. The current density distribution is the result of the interactions between the temperature, relative humidity and molar fractions distributions along the cell surface. The in-plane GDL structuring shows an improvement of current density homogeneity in dry conditions. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, an approach allowing connecting two numerical models for the simulation of the PEMFC operation and durability at different physical scales is presented. After explaining the interest of coupling them to study the interactions between the fuel cell system and the fuel cell itself, along with lifetime concerns, the feasibility of the task is assessed. Then the numerical approach to achieve this coupling is presented. Finally the response of the coupled models is examined to check its validity, and first results are presented. Predicted fuel cell lifetime trends when changing the stack operation conditions are shown, which highlight the presence of optima concerning temperature, demanded current, pressure and O2 stoichiometry. Two operation modes are then compared in terms of their impact on the fuel cell performance decay, showing that power cycles are more damaging the fuel cell than nominal operation. [Copyright &y& Elsevier]

Abstract: A new analysis of performance degradation during oxygen starvation of PEMFC (Proton Exchange Membrane Fuel Cell) is proposed in this paper. Oxygen starvation happens for several reasons like compressor delay, fault during peak power demand or water management issues. The consequences on fuel cell performance degradation are not still well understood. This paper proposes a complete study with experimental tests and modeling. Impacts on performance were investigated under oxygen starvation and effects on the local conditions in the MEA (Membrane Electrode Assembly) were measured and modeled. In particular, current density measurements during oxygen starvation have been made with a specific bi-cell stack. Voltage oscillations were also found. Durability test have been realized on a PEMFC stack. Samples from the degraded MEA were analyzed by TEM (Transmission Electron Microscopy). Degradation mechanisms are proposed and the local conditions during oxygen starvation are identified. [Copyright &y& Elsevier]

In this paper we propose a mechanistic model describing the coupling between the polymer electrolyte fuel cell (PEFC) membrane electrodes assembly (MEA) electrocatalysis and the cathode carbon catalyst-support corrosion. The electrocatalysis description includes our previously introduced irreversible thermodynamics nanoscale models of the electrochemical reactions (hydrogen oxidation reaction/oxygen reduction reaction) coupled with the catalyst/ionomer interface double layer phenomena. Physically, the model describes the feedback between the instantaneous performance and the intrinsic cathode carbon oxidation process. It allows exploring the impact of the operating conditions (nominal current, reactant gas pressures, temperature, etc.) and the initial electrodes compositions (carbon and platinum loadings) on the PEFC MEA durability. Some numerical simulations show agreement with experimental knowledge already reported in literature, in particular, when the anode chamber is partially exposed to oxygen (induced by polymer electrolyte membrane crossover or fuel starvation), cathode thickness decrease and cell potential decay are predicted. Furthermore, we found that cathode damage increases as platinum loading increases and as platinum nanoparticles size decreases. Moreover, carbon corrosion favors the platinum coarsening; competition between carbon oxidation reaction and electrocatalytic mechanisms is investigated. Simulations also suggest that an "optimal" external load current inducing a "maximal" durability exists. The sensitivities of the electrochemical impedance spectra to the operating conditions and simulated operation time are also provided. [ABSTRACT FROM AUTHOR]

This paper presents a study of the carbon support corrosion and mitigation strategies through the use of a pseudo-3D model. This model consists in coupling a 2D model along the channel with another model perpendicular to the flow at the rib/channel scale. Simulations offer a deeper understanding of the corrosion through the analysis of the local conditions. Rib/channel heterogeneities show the higher degradation in the zones facing the anodic rib. These results are validated qualitatively on literature data by analysis of SEM images and carbon dioxide concentration at the cathode outlet. Three mitigation strategies are studied using the model. The first one consists in speeding up the hydrogen filling of the cell. The second strategy involves an external electrical resistance to create a current leak during the startup. Third, a design study of the rib/channel is performed to minimize the cathode degradation. Whatever the mitigation strategy, it consists in reducing either the duration or the magnitude of the high cathode electrode potential. [ABSTRACT FROM AUTHOR]

One of the bottlenecks hindering the usage of polymer electrolyte membrane fuel cell technology in automotive applications is the highly load-sensitive degradation of the cell components. The cell failure cases reported in the literature show localized cell component degradation, mainly caused by flow-field dependent non-uniform distribution of reactants. The existing methodologies for diagnostics of localized cell failure are either invasive or require sophisticated and expensive apparatus. In this study, with the help of a multiscale simulation framework, a single polymer electrolyte membrane fuel cell (PEMFC) model is exposed to a standardized drive cycle provided by a system model of a fuel cell car. A 2D multiphysics model of the PEMFC is used to investigate catalyst degradation due to spatio-temporal variations in the fuel cell state variables under the highly transient load cycles. A three-step (extraction, oxidation, and dissolution) model of platinum loss in the cathode catalyst layer is used to investigate the cell performance degradation due to the consequent reduction in the electro-chemical active surface area (ECSA). By using a time-upscaling methodology, we present a comparative prediction of cell end-of-life (EOL) under different driving behavior of New European Driving Cycle (NEDC) and Worldwide Harmonized Light Vehicles Test Cycle (WLTC). [ABSTRACT FROM AUTHOR]

In this paper, an approach coupling an along the channel and rib-channel models has been developed to perform a design optimization of PEM fuel cell bipolar plates rib/channel patterns. Overall performance mainly results from a competition between current collection and oxygen supply. The allows proposed to investigate the effect of geometry and operating parameters on the resulting equilibrium and optimum. Moreover, heterogeneities issued from the crushing effect by the rib on the GDL are accounted. The electrochemical parameters used in the model are fitted to experimental measurements before being used in the optimization process. Results at the channel/rib scale show the competition between the oxygen supply from the gas channel to the catalyst layer and the current collection by the ribs. This understanding is possible thanks to the access to local conditions (such as the oxygen concentration) given by the model which are difficult to reach with experimental measurements. In-plane and through plane heterogeneities of current density distribution in the catalyst layer are exhibited. Design optimization is performed on the channel width/total width ratio on the cathode side. The model suggests an optimal channel design by varying its width along the flow while the standard design considers a contant ratio. This optimal channel is shown to be mainly dependent on the stoichiometry ratio of oxygen. [ABSTRACT FROM AUTHOR]

In the present work, the in-plane structuration of the electrode Gas Diffusion Layer (GDL) is proposed as an interesting approach to reduce the operating heterogeneities occurring within the cell along the gas flow fields, especially in dry operating conditions. This is especially important for transportation applications where the fuel cell is often operated in these conditions. Structured and homogeneous large-area (220 cm 2 ) membrane electrode assemblies (MEAs) are tested in single-cell and 6-cell stack configurations. An S++ ® electronic card inserted in the stack is used to measure the current distribution within the cell, which is an indicator of the local electrochemical reaction conditions. The results of the current distribution measurements together with the cell performances obtained for the structured and the homogenous MEAs indicate that the electrode in-plane structuration is effective in reducing the functioning heterogeneities within the cell under specific operating conditions. [ABSTRACT FROM AUTHOR]