Abstract
Understanding the cell temperature distribution of solid oxide fuel cell (SOFC) stacks during normal operation has multifaceted advantages in performance and degradation studies. Present efforts on measuring temperature from operating SOFCs measure only the gas channel temperature and do not reveal the cell level temperature distribution, which is more important for understanding a cell's performance and its temperature-related degradation. The authors propose a cell-integrated, multi-junction thermocouple array for in-situ cell surface temperature monitoring of an operational SOFC. The proposed thermocouple array requires far fewer numbers of thermoelements than that required by sets of thermocouples for the same number of temperature sensing points. Hence, the proposed array causes lower disturbance to cell performance than thermocouples. The thermoelement array was sputter deposited on the cathode of a commercial SOFC using alumel (Ni:Al:Mn:Si – 95:2:2:1 by wt.) and chromel (Ni:Cr – 90:10 by wt.). The thermocouple array was tested in a furnace over the entire operating temperature range of a typical SOFC. The individual sensing points of the array were shown to measure temperature independently from each other with equivalent accuracy to a thermocouple. Thus, the concept of multi-junction thermocouples is experimentally validated and its stability on a porous SOFC cathode is confirmed.
Highlights
Understanding the role of operating temperature of an solid oxide fuel cell (SOFC) stack during its operation is crucial to advance the SOFC technology to a level that will deliver an economically viable solution to the future energy era
A comprehensive knowledge on the cell level and stack level temperature distribution of an operating SOFC is central to the success of such investigations
The substrate was prepared by first cleaning with acetone and with deionised water followed by drying in a furnace at 150 C for 10 min
Summary
Understanding the role of operating temperature of an SOFC stack during its operation is crucial to advance the SOFC technology to a level that will deliver an economically viable solution to the future energy era. Since each sensing point of a thermocouple is formed by intersection of two thermoelements, measuring temperature from SOFC with greater spatial resolution requires deposition of a large number of thermoelements on the electrodes. This is likely to cover a large portion of the effective cell area, potentially causing adverse effects to cell performance. To circumvent this problem while preserving the merits of TFTC, the authors investigated the possibility of sharing thermoelements between junctions to make multi-junction thermocouples that reduce the number of thermoelements required in multi-point temperature sensing. This paper discusses the fabrication, testing, and results of these multi-junction thermocouples fabricated on SOFC electrodes
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