Thesis for degree: Licentiate of Engineering

1 Introduction
After some time of decreasing interest, fuel cell research is now receiving a lot of attention.
Fuel cells are considered a promising future resource for both stationary and distributed
electric power stations because of their high performance and high reliability [1, 2]. In order
to explore these aspects in greater depth, there is a need for both multiphysics and multiscale
modeling. The approach is by solving the equations for momentum, charge, heat and mass
transport and chemical reactions at the same time at corresponding scales. At this point,
simulation of mass diffusion and convection as well as chemical and electrochemical
reactions at microscale will offer crucial insight to improve the performance of the fuel cell
[3]. Furthermore, future prospects for fuel cell research are to connect microscale to
macroscale and obtain stable solutions for multiscale modeling.
Solid oxide fuel cells (SOFCs) are particularly interesting because it operates at high
temperature and can therefore handle the reforming of hydrocarbon fuels directly within the
cell. SOFCs have a number of advantages, e.g., high conversion efficiency, high quality
exhaust heat and flexibility of fuel input. However, as expected, SOFCs also have
disadvantages. For instance, because they operate at very high temperatures (800–1100C
[1]), material performance and manufacturing costs are currently of concern. Recently,
attempts have been made to lower the operating temperature of SOFCs by adopting a porous,
anode-supported structure to reduce the thickness of the electrolyte.
It is important to model all physical processes and chemical reactions simultaneously since
the mass and charge transport depends on the multifunctional material structure in the porous
electrodes, the chemical reactions, the temperature distribution and the species concentrations.
The fluid flow depends on the chemical reactions, temperature and fluid characteristics. The
heat transport depends on the polarization losses, the chemical reactions, the fluid flow and
the material structure. The reforming reactions depend on temperature, concentration and
amount of catalyst available. The interaction issues are numerous and here the microscopic
contributions are important to include. Also it is necessary to model SOFCs into detail and
explore them at a microscopic level, in order to fully understand how different parameters
affect the performance, by connecting different physical phenomena at different scales [2, 4].
The purpose of this study is to develop a microscale model of an anode of an SOFC for the
transport processes and the chemical reactions to get a deeper understanding of the effect on
the different physical processes at multiple scales. The lattice Boltzmann method (LBM) is
used to model the mass transport at microscale for a limited part of the porous anode. Also an
evaluation of a macroscale model for the whole unit cell is carried out.
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