Numerical Analysis of Gas Distribution in 1000 W-Class Solid Oxide Fuel Cell Stack With Internal and External Manifolding

Abstract

Solid oxide fuel cells (SOFC) can generate electricity and heat with a minimal negative impact on the environment and with high electrical efficiency (∼60%). SOFC stacks are the key component of cogeneration units in the range from several kiloWatts up to hundreds of kiloWatts. The larger power output of a system is achieved by the multiplication of a number of separate modules, which are usually based on 1000 W class stacks. In the design of the SOFC stack, the following parts are distinguished: two terminating plates (top and bottom), interconnectors, separators, gaskets, electrical connections, fuel and oxidant delivery lines, and fuel cells. Geometric features and physical and chemical properties of the aforementioned components affect the performance and mechanical strength of the SOFC stack. Two different approaches for air supply can be used and were investigated, namely internal and external manifolding. Comprehensive analysis of the geometric features of the stack together with inserts, the supply and discharge piping of reaction gases, was performed in order to determine the optimal operating conditions on the latest third generation of the SOFC stack, which is currently under development at the Institute of Power Engineering (IEN). This study includes the results of laboratory tests and numerical studies. The results obtained indicate the set of parameters that influence the performance and lifetime of SOFCs. Among others, the most important variables are as follows: fuel type, operating conditions, homogeneity of temperature distribution, and uniformity of gas flow.