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Article

Modeling the Performance of Flattened 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, PAanshu@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), 52-59 (Aug 16, 2004) (8 pages) doi:10.1115/1.1842783 History: Received June 03, 2004; Revised August 16, 2004

Abstract

In this paper, we develop a computational model to predict the electrical performance of the flattened tubular solid oxide fuel cell (SOFC) designed by Siemens Westinghouse Corporation. This design is an improvement over the conventional cylindrical SOFC and allows higher power densities. We modeled the current transport in a cross section of the cell for a given cell operating voltage and local Nernst voltage. We solved the resulting system of simultaneous nonlinear equations using $n$-dimensional Newton-Raphson algorithm. The output gives the current density distribution and also the total current at the cross section, which is used to obtain the total cell current (and power) for the given voltage. The results of the model are in good agreement with the experimental performance reported in literature.

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Figures

Figure 1

Cross section of the HPD design of SOFC with four ribs and five airflow channels. The differential element has a length of Δx.

Figure 2

Resistor network diagram of one symmetric half of the flattened SOFC. The diagram is representative and shows only a few nodes (or differential elements) due to space constraint. The actual number of nodes (differential elements) used in computation is as follows: (N1=28;N2=58;N3=85;N4=110;N=153;M1=25;M2=50;M=75).

Figure 3

Sketch of a differential element of current transport between anode and cathode

Figure 4

Iterative algorithm for solving the finite difference procedure

Figure 5

V–I Characteristics of the HPD design of SOFC

Figure 6

Total current flowing in the cell and the distribution in ribs and branches at an operating voltage of 0.72V

Figure 7

Current density distribution at two cross sections: Cell inlet (x=0) and cell exit (x=L). The current density is highest at the points where current enters the cell from interconnect (N0, N2, and N4).

Figure 8

Anode currents per unit cell length (A/m) flowing on two cross sections: cell inlet (x=0) and exit (x=L)

Figure 9

Cathode currents per unit cell length (A/m) flowing on two cross sections: cell inlet (x=0) and exit (x=L)

Figure 10

Anode and cathode surface voltage at the inlet cross section. The voltage at points N0, N2, and N4 is taken to be 0 as a base.

Figure 11

Impact of changing the rib width to 4000μm. More current flows in the ribs and the total cell current (and hence power) increases than in Fig. 6.

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