The work presented in this article combines experimental analysis and theoretical studies of temperature effects on the performance of an open-cathode, self-humidified PEM fuel cell system for the design of optimization strategies. The experimental analysis shows the great potential of improving the system performance by proper temperature management. The most significant temperature dependent parameters of the system under study are the activation polarization and the water content of the ionomer of the catalyst layer. An Extremum seeking control algorithm is proposed to regulate the temperature to a voltage maximum. However, the slow dynamics of the temperature related catalyst-drying effect on performance complicate the optimal thermal management via model-free control strategies.

Proton Exchange Membrane Fuel Cells (PEMFC) are energy efficient and environmentally friendly alternatives to conventional energy conversion systems in many yet emerging applications. In order to enable prediction of their performance and durability, it is crucial to gain a deeper understanding of the relevant operation phenomena, e.g., electrochemistry, transport phenomena, thermodynamics as well as the mechanisms leading to the degradation of cell components. Achieving the goal of providing predictive tools to model PEMFC performance, durability and degradation is a challenging task requiring the development of detailed and realistic models reaching from the atomic/molecular scale over the meso scale of structures and materials up to components, stack and system level. In addition an appropriate way of coupling the different scales is required. This review provides a comprehensive overview of the state of the art in modeling of PEMFC, covering all relevant scales from atomistic up to system level as well as the coupling between these scales. Furthermore, it focuses on the modeling of PEMFC degradation mechanisms and on the coupling between performance and degradation models.

In this paper we present a new dynamic multiscale model of an open-cathode Polymer Electrolyte Membrane Fuel Cell (PEMFC). The model describes two-phase water transport, electrochemistry and thermal management within a framework that combines a Computational Fluid Dynamics (CFD) approach with a microstructurally-resolved model predicting the water filling dynamics of the electrode pores and the impact of these dynamics on the evolution of the electrochemically active surface area (ECSA). The model allows relating for the first time the cathode electrode structure to the cell voltage transient behavior during experimental changes in fuel cell temperature. The effect of evaporation rates, desorption rates and temperature changes on the performance of four different electrode pore size distributions are explored using steady-state and transient numerical simulations. The results are discussed with respect to water management and temperature control.

Abstract.The durability of polymer electrolyte membrane fuel cells (PEMFC) is governed by a nonlinear coupling between system demand, component behavior, and physicochemical degradation mechanisms, occurring on timescales from the sub-second to the thousand-hour. We present a simulation methodology for assessing performance and durability of a PEMFC under automotive driving cycles. The simulation framework consists of (a) a fuel cell car model converting velocity to cell power demand, (b) a 2D multiphysics cell model, (c) a flexible degradation library template that can accommodate physically-based component-wise degradation mechanisms, and (d) a time-upscaling methodology for extrapolating degradation during a representative load cycle to multiple cycles. The computational framework describes three different time scales, (1) sub-second timescale of electrochemistry, (2) minute-timescale of driving cycles, and (3) thousand-hour-timescale of cell ageing. We demonstrate an exemplary PEMFC durability analysis due to membrane degradation under a highly transient loading of the New European Driving Cycle (NEDC).

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