The Effects of Dynamic Dispatch on the Degradation and Lifetime of Solid Oxide Fuel Cell Systems

Understanding of mechanisms affecting degradation, durability and performance of solid oxide fuel cell (SOFC) stacks and integrated systems has become important due to increasing worldwide deployment. A novel simulation approach accounting for state-of-the-art understanding of degradation mechanisms in the context of an operating SOFC system has been developed. Investigative tools simulating lifetime degradation have been applied to a physical SOFC system model designed and controlled to allow dynamic dispatch. The system was operated in two modes (a) constant power output mode, and (b) diurnal dynamic dispatch mode. Results show that on a time basis the dynamically dispatched SOFC system proved more durable and degraded less than a system operated at constant full-power output. The net energy production over the stack lifetime was roughly equivalent between the two modes (1.5 to 2 kWh cm(-2)), with the dynamically dispatched fuel cell operating longer, degrading less and producing more power during highly valued peak demand periods. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.032111jes] All rights reserved.

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Daniel Favrat, Arata Nakajo, Jan Van Herle
2011
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https://infoscience.epfl.ch/record/170817?ln=fr

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Electrochemical Model of Solid Oxide Fuel Cell for Simulation at the Stack Scale I. Calibration Procedure on Experimental Data

Stefan Diethelm, Daniel Favrat, Arata Nakajo, Jan Van Herle, Zacharie Wuillemin

Lifetime prediction and improvement of solid oxide fuel cell (SOFC) devices require a reliable electrochemical model that supports the implementation of degradation phenomena. This study comprises two parts. This Part I describes the calibration of an electrochemical model based on physical principles for simulation at the stack scale. Part II presents the further implementation of degradation models. A distinction is made between the two most common cathode materials, lanthanum strontium manganite and lanthanum strontium cobalt ferrite. The experimental data used for the parameter estimations was gathered by two segmented setups. The calibrations enabled to reproduce adequately the measurements over a wide range of operating conditions. The optimal values of the physical parameters were inside the ranges reported in literature. Unambiguous discrimination could not be achieved between variations (i) in the choice of electrode rate-determining steps, (ii) data on the properties of the materials found in literature and (iii) empirical relations for the steam-methane reforming reaction. However, these model variations do not affect significantly the predicted magnitudes and distributions of the field variables assumed to govern the degradation processes at the SRU scale, compared with the uncertainties on the degradation phenomena to be implemented in Part II. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3596433] All rights reserved.

2011

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Electrochemical model of solid oxide fuel cell for simulation at the stack scale. Part II: Implementation of degradation processes

Stefan Diethelm, Daniel Favrat, Arata Nakajo, Pietro Tanasini, Jan Van Herle

The degradation of the electrochemical performance of solid oxide fuel cell (SOFC) devices is a major hurdle to overcome before commercialisation. The interplay between the phenomena and the long testing times complicate the research, which highlights the relevance of modelling to propose mitigation approaches. This study comprises two parts. This Part II proposes approaches for the simulation of the degradation induced by: (i) interconnect corrosion, (ii) loss of ionic conductivity of the ion-conducting materials, (iii) nickel particle growth in the anode, (iv) chromium contamination and (v) formation of insulating phases in the cathode. The literature survey highlights the lack of data for a completely consistent calibration of the models, despite the simplifications. The support for the implementation is the electrochemical model validated in Part I and a two-dimensional model of the cell and interconnection system. The cathode largely contributes to the degradation. The local overpotential predominantly governs chromium contamination, which can promote the formation of insulating phases, as operation proceeds. The local electronic current density has comparatively a weak direct influence on the degradation. Qualitative agreement with experimental data from the literature could be achieved, without dedicated adjustments of the parameters. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3596435] All rights reserved.

2011

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Understanding mechanisms that affect degradation and durability of solid oxide fuel cell (SOFC) stacks and systems is becoming increasingly important as systems are being deployed around the world. A novel simulation approach accounting for state-of-the-art understanding of degradation mechanisms in the context of an operating SOFC system has been developed. Investigative tools simulating lifetime degradation have been applied to a physical SOFC system model designed and controlled to allow dynamic dispatch. The system was operated in two modes (a) constant power output mode, and (b) diurnal dynamic dispatch mode. Results show that on a time basis the SOFC system with dynamic dispatch proved more durable and less degraded than the system operated in constant full-power output. The net energy production was roughly equivalent between the two modes, with the dynamically dispatched fuel cell degrading slightly less and producing a greater portion of power during peak demand.

Electrochemical Society2011

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Pile à combustible à oxyde solide

Les piles à combustibles à oxydes solides (ou SOFC selon l'acronyme anglais de Solid oxide fuel cells) sont prévues essentiellement pour les applications stationnaires avec une puissance de sortie a

Système

Un système est un ensemble d' interagissant entre eux selon certains principes ou règles. Par exemple une molécule, le système solaire, une ruche, une société humaine, un parti, une armée etc. Un s

Système solaire

Le Système solaire (avec majuscule), ou système solaire (sans majuscule), est le système planétaire du Soleil, auquel appartient la Terre. Il est composé de cette étoile et des objets célestes gravi