Understanding the Electrochemical Behavior of SOFC Stacks

Abstract

In contrast to single cells the electrochemical processes, the resistances and the loss mechanisms of SOFC stacks are not well understood. The paper presents both experimental and modeling results of the electrochemical behavior of SOFC stacks with ASC cells in the cassette design at different operating conditions. The focus lies on the investigation of critical operating conditions, e.g. high current densities and high fuel utilizations. The stacks were investigated by current-voltage curves, electrochemical impedance spectroscopy (EIS) and gas analysis. Results of both integral and locally resolved measurements along the fuel gas flow path are presented. The modeling results were obtained with a two dimensional elementary kinetic model which represents a single cell along the gas channels and through the thickness of the membrane-electrode assembly.

Understanding the Electrochemical Performance of SOFC Stacks

“…Hence, the strong decrease in stack performance for low fuel gas flow rates can be explained by gas transport limitations. Previous studies at DLR have shown that especially at high current densities a severe depletion of H 2 along the flow channel can occur, which can even lead to partial oxidation of the Ni in the anode substrate and the anode itself (5,20). Figure 8.…”