(509g) Numerical Modeling of Solid-Oxide Fuel Cells

Solid-Oxide Fuel Cells (SOFC) are expected to play a major role in the run for efficient energy production. However, modeling SOFCs is challenging due to the complex interactions between chemical, electrochemical, heat, and mass transfer processes. In this paper we present a model to simulate a SOFC stack based on efficient numerical algorithms. The model can be applied to simulate planar or tubular SOFC. It applies hierarchically arranged detailed models from an atomic scale up to reactor scale. On the reactor scale a single channel SOFC model solves the governing equations for species transport and chemical reactions. This model incorporates detailed thermo-catalytic chemistry based on an elementary step mechanism. The multi-component species transport through porous media is described by Dusty-Gas Model (DGM)[1-2].

In the transient stack model, the transient heat balance of the solid structure is solved while the processes in the single cell is treated as quasi steady-state, which is possible due to the decoupling of the time scales on stack and cell level. Modeling each and every single cell in a stack with detailed description of transport and chemistry is an enormous computational task. Therefore in our approach not every single channel is simulated, and a cluster-agglomeration algorithm is applied to choose representative channels from the SOFC stack [3-4]. This approach reduces the computational cost significantly while maintaining a sufficient accuracy of the solution.

The single cell SOFC model can be used to optimize the electrode microstructure and geometry of the cell. For example, in the case of direct internal reforming in anode supported cell, optimal anode thickness can be found for a given inlet fuel composition. Furthermore, the model also predicts the optimal catalyst loading required for a given inlet fuel composition. This single cell model has been used to study the optimal performance of the cell for a variety of operating and geometrical conditions.

References:

[1] H. Zhu, R. J. Kee, V. M. Janardhanan, O. Deutschmann, and D. G. Goodwin. J. Electrochemical Society 152 (2006) A2427-A2440

[2] V.M. Janardhanan ,O. Deutschmann. J. Power Sources 162 (2006) 1192

[3] S. Tischer, C. Correa, O. Deutschmann. Catalysis Today 69 (2001) 57

[4] O. Deutschmann, S. Tischer, C. Correa, D. Chatterjee, S. Kleditzsch, V. M. Janardhanan, DETCHEM software package, 2.0 ed., www.detchem.com, Karlsruhe, 2004.