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Article

Modeling the Performance of a Tubular Solid Oxide Fuel Cell

[+] Author and Article Information

Center for Energy and Environmental Studies, Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA anshu@cmu.edu

D. H. Archer

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA

E. S. Rubin

Center for Energy and Environmental Studies, Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA

1

Corresponding author; Tel: (412) 268-2670.

J. Fuel Cell Sci. Technol 2(1), 38-44 (Aug 16, 2004) (7 pages) doi:10.1115/1.1842781 History: Received May 22, 2004; Revised August 16, 2004

Abstract

In this paper, we develop two computational models for the electrical performance of the tubular solid oxide fuel cell designed by Siemens Westinghouse Corporation. The first model makes simplifying assumptions for activation and concentration polarizations and obtains an analytical solution. In the second procedure, we allow the polarizations to vary with the current density and solve the equations numerically. The results of the two methods are in good agreement with the experimentally quoted performance results. Thus, the relatively simple analytical procedure can be used to predict the performance of the cell as a function of cell dimensions.

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Figures

Figure 1

View of the SOFC showing the Nernst voltages (V) and current (A/m) at the inlet and exit and also a slice (dx) located at a distance x

Figure 2

Cross section of a tubular SOFC showing the different layers

Figure 3

Differential element located at angular location θ showing flow of current between anode and cathode

Figure 4

Voltage and power characteristics using the two approaches. The results of nonlinear model and analytical model are in good agreement in the linear region. The model predicts a cell power output of 123W and a current density of 214mA∕cm2 for a voltage of 0.65V and Nernst voltages of 0.90 and 0.77V at cell inlet and exit, respectively.

Figure 5

Anode and cathode currents at a cross-sectional slice located at cell inlet (x=0). The circumferential anode current decreases monotonically. The cathode current increases and reaches a maximum at the angular location θ=140deg.

Figure 6

Current densities as a function of radial location at a cross section at cell inlet (x=0) and cell exit (x=L) using the two methods. This shows the limitations of the analytical solution using constant polarizations.

Figure 7

Impact of cell operating voltage on current density at a cross-sectional slice at cell inlet (x=0). The current densities are high for lower operating voltages and approach limiting current values for 0.55V.

Figure 8

Comparison of the different polarizations for seven current paths at a cross-sectional slice located at cell inlet (x=0)

Figure 9

Impact of cathode thickness on cell performance

Figure 10

Impact of outer cell diameter on power for operating voltage of 0.65V

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