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Article

Time Dependent Properties and Performance of a Tubular Solid Oxide Fuel Cell

[+] Author and Article Information
Gang Ju, Kenneth Reifsnider, Xinyu Huang, Yanhai Du

Connecticut Global Fuel Cell Center, University of Connecticut, Storrs, CT, 06269

J. Fuel Cell Sci. Technol 1(1), 35-42 (May 17, 2004) (8 pages) doi:10.1115/1.1782926 History: Received May 06, 2004; Revised May 17, 2004

Abstract

Time dependent properties and performance of tubular solid oxide fuel cells were studied numerically and experimentally. The numerical model incorporated local characteristics such as porosity, tortuosity, grain size, and conductivity and was used to evaluate the specific and relative changes in performance caused by the effect of time-dependent material changes of those characteristics. A 500 hour experimental study was conducted at $800°C$ in $97%H2∕3%H2O$ on an extruded $LSCo-La0.6Sr0.4CoO3∕LSGM∕Ni$ electrolyte-supported tubular SOFC made in our laboratory. Changes in current density with time (at constant voltage) formed a curve with initial convex (upward) curvature, becoming monotonic decreasing. The microstructure of the constituent layers was examined by scanning electron microscopy. Comparisons between model predictions and experimental observations were made. For the situation modeled and tested, the porosity and ionic conductivity were found to be most influential on performance. More importantly, the effect of porosity is a trade-off between the influence on gas transport and the mixed conductor influence on the electrochemical reactions at the electrode.

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Figures

Figure 1

A generic drawing of the tubular solid oxide fuel cell

Figure 2

Fuel cell 500 hours durability test result, current (A) versus time (hour)

Figure 8

Current Density versus the ionic conductivity at the voltage=0.7V

Figure 7

Current density versus spatially linear varied porosity at the voltage=0.7V

Figure 6

Effective charge transfer resistance as a function of porosity ε, ionic conductivity σ and grain size B

Figure 5

Current Density versus spatially uniform distributed porosity of the electrodes at the voltage=0.7V

Figure 4

Modeled fuel cell voltage versus current density, and voltage and various polarizations versus current density of the electrolyte supported SOFC

Figure 3

Experimental results: cell voltage and power density as a function of current density

Figure 9

Current density as a function of pore size at the voltage=0.7V

Figure 10

Current density as a function of grain size at the voltage=0.7V

Figure 11

(a) SEM micrographs of LSCo-La0.6Sr0.4CoO3 composite cathode in three different locations; (b) Image analysis of the objects in SEM micrographs using ImageJ software, and (c) three-dimensional surface plot of the pixel analysis.

Figure 12

Generic trend chart of properties as a function of time

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