SOFC Characteristics along the Flow Path

摘要

Electrolyte supported solid oxide fuel cells with a galvanically separated cathode were characterised integrally and locally. The measurements were performed by electrochemical impedance spectroscopy (EIS), current density / voltage (ⅰ-ⅴ) and temperature measurements and gas chromatography. The results show a change in the cell behaviour from air inlet to air outlet in the applied counter flow design. Although the anode was forced on a common potential, the segmented cathode was greatly influenced by the anodic conditions. The open circuit voltage (OCV) decrease from air inlet to outlet was therefore mostly affected by the anode gas composition. Also the current density distribution showed a decrease from air inlet to outlet. The impedances obtained by local EIS verified these observations. As an important influencing factor on the impedance the temperature could be pointed out. The air inlet remained slightly cooler than the rest of the cell because the air in the internal manifold was 50℃ cooler than the cell. Leakages in the cell and sealing caused conspicuous varieties in the impedance at OCV. A drift in ohmic resistance that could be attributed to contacting problems terminated the operation of the cell. Gas chromatography measurements in a pre-test were concordant with the assumed gas concentration distribution in the cell.