Determination of Temperature and Fuel Utilization Distributions in SOFC Stacks with EIS

Abstract

Efficient operation of solid oxide fuel cell (SOFC) stacks requires uniform temperature and fuel utilization distributions in the stack. Especially high fuel utilizations necessitate uniform fuel flow distributions to avoid performance decrease or anode reoxidation. A uniform temperature distribution helps to prolong the life-time of the stack. This work presents a method to determine the fuel utilization and temperature distribution in SOFC stacks with electrochemical impedance spectroscopy (EIS). The equations for relating the measured impedance and fuel utilization and temperature are derived from physical equations describing the SOFC stack. The method is demonstrated with an ElringKlinger AG 10-cell stack fuelled with 50%/50% H 2 /N 2 at nominal operation conditions. The difference in temperature and fuel utilization between cells was determined. The calculated distributions are in line with cell voltage measurements. The method can be used to improve SOFC stack design and performance.

Control of oxygen-to-carbon ratio and fuel utilization with regard to solid oxide fuel cell systems with anode-offgas recirculation: A review

“…The presented EIS variant is of particular interest for the low frequency components and represents a significant time saving of several orders of magnitude compared to conventional EIS. A promising concept is also the conjunction of EIS with an associated equivalent circuit diagram, as proposed by Tallgren et al [93] and Nusev et al [108]. Analysis of the respective parameters can be used in an automated monitoring tool by comparison to a reference.…”

“…The studies on diagnostic methods are mostly limited to single-cells or short-stacks with few cells and not applied at system level as can be seen in [18,28,[87][88][89][90]93,94,96,97,99,108]. In addition, simplifying limitations to a known and simplified gas composition such as pure hydrogen or methane as well as a mixture with a defined amount of water vapor are used, see [92][93][94]96,97,99,108]. In EIS the high measuring effort and the long measuring time to record a complete impedance spectrum is disadvantageous for application in SOFC-systems.…”

“…Tallgren et al [93] present a concept based on the work of Dekker et al [64], where FU distribution on individual cells of a SOFC-stack can be determined by means of EIS. The components of an equivalent circuit model are adapted and compared with a reference.…”

Properties of Spinel Protective Coatings Prepared Using Wet Powder Spraying for SOFC Interconnects

“…The WPS method (7) was applied to deposit protective layers onto K41/441 and Sandvik Sanergy HT (SS HT) commercial stainless steels (0.2 mm thickness) that contain different chromium amounts (8). The spraying suspensions were prepared by ball milling binder, solvent, and commercial MCO (KCERACELL, Korea) or MnO (Sigma-Aldrich) powder with zirconia ball media.…”