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Research Papers

# A Detailed Three-Dimensional Simulation of an IP-SOFC Stack

[+] Author and Article Information
B. A. Haberman1

Hopkinson Laboratory, Engineering Department, Cambridge University, Cambridge CB2 1PZ, UKb.haberman.01@cantab.net

J. B. Young

Hopkinson Laboratory, Engineering Department, Cambridge University, Cambridge CB2 1PZ, UKjby@eng.cam.ac.uk

1

Present address: Department of Mechanical Engineering, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, UK.

J. Fuel Cell Sci. Technol 5(1), 011006 (Jan 16, 2008) (12 pages) doi:10.1115/1.2786468 History: Received July 26, 2006; Revised February 12, 2007; Published January 16, 2008

## Abstract

A typical integrated-planar solid oxide fuel cell (IP-SOFC) consists of modules with series connected electrochemical cells printed on their outer surfaces. Oxygen is supplied to the cathodes from air flowing over the outside of the module and hydrogen diffuses from the internal fuel channels to the anodes through the porous module support structure. The IP-SOFC is intended for use in medium scale stationary power applications, and such a system will use a fuel cell stack containing many thousands of modules housed inside a pressure vessel. For certain purposes, the geometry of this stack can be adequately described using a computational domain that considers just two modules. A computer code has been developed to simulate the many physical and chemical processes occurring within the stack, including fluid flow, heat transfer, water gas shift, and electrochemical reactions. The simulation results show how the performance of the IP-SOFC stack is strongly affected by these physical processes, the geometry of the stack, and the operating conditions. The temperature distribution, which is difficult to predict using a less realistic geometric model, is almost uniform within each fuel channel and rises steadily in the air flow direction. The shift reaction, which is catalyzed by the anodes, is of great importance, and as the fuel flow becomes depleted of hydrogen it enables the electrochemical cells to make increasing use of carbon monoxide. Overall it was found that the operating voltage produced by the fuel cells is typically $0.74V$ and the component efficiency, the ratio of the actual power output to the maximum available from the fuels consumed, is around 59%.

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## Figures

Figure 1

Gas and ion transport, and electrochemical reactions in an IP-SOFC

Figure 2

Schematic diagram of the fuel cell stack and reformer system

Figure 3

Schematic diagram of the components of an infinite fuel cell stack

Figure 4

The variation of the rate of hydrogen production of the shift reaction Ss,H2

Figure 5

Conventional current flow path analyzed in Ref. 10,27

Figure 6

Radiative heat exchange between two directly facing surfaces of the same area

Figure 7

Schematic diagram of a cross section through the computational domain in the x-z plane

Figure 8

Schematic diagram of a cross section through a fuel cell module in the x-z plane showing the arrangement of the electrochemical layers considered in this study. The bracketed terms show the thickness of each layer

Figure 9

Schematic diagram of a cross section through the stack in the y-z plane showing the computational domain considered

Figure 10

Diagram showing a computational cell and the storage of information

Figure 11

Variation of the resistivity of the current carrying materials with temperature

Figure 12

Plot of conventional current density vectors for a simulation of the three electrochemical layers when a variable potential difference is generated at the anode/electrolyte boundary

Figure 13

Plot of conventional current density vectors for a simulation of the three electrochemical layers when a uniform potential difference is generated at the anode/electrolyte boundary

Figure 14

Temperature (T) distribution plotted in the x-z plane located at the midpoint of FC 4 in the y direction

Figure 15

Temperature (T) distribution plotted in the x-y plane located at the midpoint of air channel 1 in the z direction

Figure 16

Hydrogen mole fraction (XH2) distribution plotted at a cross section in the x-z plane located at the midpoint of FC 6

Figure 17

Carbon monoxide mole fraction (XCO) distribution plotted at a cross section in the x-z plane located at the midpoint of FC 6

Figure 18

Kas∕Kps distribution plotted at a cross section in the x-z plane located at the midpoint of FC 6

Figure 19

Hydrogen mole fraction (XH2) distribution plotted at a cross section in the y-z plane located near the FC inlets and exits at x=120mm

Figure 20

Voltage distribution on the upper outer surface of the lower module (the x-y plane located at z=9mm)

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