Model-based study of the influence of selected parameters on the performance of a low-powered SOFC.

Solid oxide fuel cells (SOFCs) are a technology of high efficiency that is often applied in stacks for modern cogeneration systems as a standalone unit, or hybridized with an internal combustion engine (ICE) or a gas turbine (GT). Such systems successfully process different types of carbohydrate fuels and have close to none local emissions. Simultaneously, SOFCs are faintly available on the market of fuel cells today, and the processes and technologies used for their production and testing are not as popular as those of proton exchange membrane fuel cells (PEMFCs). Thus, in order to better understand the nature and working principles of SOFCs, and to optimize their performance in order to better select and possibly produce a stack with the appropriate working characteristics for a concrete application, a mathematical simulation needs to be performed. This article describes a 0-D steady state model of the reforming and electrochemistry of a low-powered, intermediate temperature, anode-supported planar SOFC stack. The model uses internal reforming with 100% methane as fuel and air as oxidant. The stack is intended for a hybrid power generation system with a low-powered ICE (up to 2 kW) for realization of a bottoming or a combined cycle. The main purpose of the model is to determine a suitable single-cell and stack parameter layout with power also up to 2 kW, based on the comparison of the polarization curves, efficiency, power, and the energy contained in the anode off-gas of the cells in the stack. The varied parameters in the study are operating temperature, operating pressure and fuel utilization factor of the stack. The results show that a stack with T=750 °C, p=1 bar, and Uf=0.75 gives the most favorable characteristic in terms of compromise between performance, cost, stable operation and heat management. [ABSTRACT FROM AUTHOR]