(453f) Dynamic Modeling and Analysis of a Tubular Solid Oxide Fuel Cell

Solid oxide fuel cells have received considerable attention in recent years. Efforts have been made to improve their design and operation, and to develop mathematical models that can predict their steady-state and dynamic behavior accurately [1, 2, 3, 4, 5]. In these modeling studies, a set of simplifying assumptions, such as considering one dimensional changes only [2, 3, 4], neglecting the heat transfer by convection and radiation, and considering the isothermal behavior [1], have been made to arrive at a simple model. In addition, most of the modeling efforts have focused on steady-state cell operation [5], while a dynamic model can provide important insights into the dynamic behavior of a fuel cell. In this paper, a dynamic model of a solid oxide fuel cell is developed and presented. The model also considers the heat transfer by convection and radiation. Also, the model takes into consideration the geometry of cathode and anode porous catalysts. The system is divided into seven subsystems: the air inside the fuel cell injection tube, the injection tube itself, the space between the injection tube and the fuel-cell cell-tube, diffusion layer inside the cathode side of the cell tube, the cell tube itself, diffusion layer inside the anode side of the cell tube, and the fuel outside of the cell tube. In some of the subsystems, reaction kinetics is coupled with transport processes including energy, mass and momentum. Activation, ohmic and concentration polarizations are accounted for in the model. The resulting model equations, coupled differential equations representing all processes, are solved numerically to predict the transient response of the system. Sensitivity analyses are conducted to analyze the effects of feed conditions and design parameters on the fuel cell performance. Dynamic outlet voltage, current, and fuel-cell-tube temperature responses to changes in the external load and feed conditions are presented. The results show that the temperature and pressure of the inlet air stream and the temperature of the inlet fuel stream have the strongest effects on the fuel cell performance.

References

1. Colpan, C. O.; Dincer, I.; Hamdullahpur, F., A review on macro-level modeling of planar solid oxide fuel cells. International Journal of Energy Research, 2008, 32 (4), 336-355.

2. Jiang, W.; Fang, R. X.; Dougal, R. A.; Khan, J. A., Thermoelectric model of a tubular SOFC for dynamic simulation. Journal of Energy Resources Technology-Transactions of the Asme, 2008, 130 (2), 10.

3. Qi, Y. T.; Huang, B.; Luo, J. L., Dynamic modeling of a finite volume of solid oxide fuel cell: The effect of transport dynamics. Chemical Engineering Science, 2006, 61 (18), 6057-6076.

4. Hajimolana, S.A.; Soroush, M. Dynamics and control of a tubular solid-oxide fuel cell. Ind. Eng. Chem. Res., released online in April 2009.

5. Chaisantikulwat, A.; Diaz-Goano, C.; Meadows, E. S., Dynamic modelling and control of planar anode-supported solid oxide fuel cell. Computers & Chemical Engineering 2008, 32 (10), 2365-2381.