THERMONO: cell integrated thin-film sensor array for in-situ monitoring of SOFC temperature

In-situ temperature monitoring from a working SOFC stack indicates the overall health of the system. It also helps detecting variety of cell problems[1] while providing information to understand degradation and to develop better stack designs. Current efforts on simulating temperature distributions involve a great deal of assumptions[2]~[8], which may not present in a working stack. Existing temperature sensing technology does not qualify for in-situ temperature monitoring of a SOFC stack as it causes a significant disturbance to normal stack operation when inserted into a stack[9]. Therefore, Novel temperature sensor architecture was developed to in-situ monitor SOFC running temperature while causing only a minimum disturbance to the normal stack operation. This architecture, named as THERMONO, enables to reduce the number of external wires required: only {N+1} number of external wires for N number of independent temperature sensing points. A thin-film THERMONO having 4 independent sensing points was fabricated on the cathode of a cell (Φ52mm, Kerafol Ltd, KeraCell II). Standard K-type thermocouple materials, Alumel (Ni 95%, Mn 2%, Al 2%, Si 1%) and Chromel (Ni 90%, Cr 10%) of 99.99% purity were chosen as the THERMONO materials. THERMONO was successfully tested in a furnace up to 10500C. A commercial K-type thermocouple was placed adjacent to THERMONO as a reference. Transient response of THERMONO was in very good agreement with the thermocouple validating the sensor concept and proving its robustness on commercial cells. THERMONO is being tested in a specially designed fuel cell test rig to sense the temperature from a working SOFC. Integration of THERMONO into commercial fuel cells and short stacks is also covered in this study and the results will be useful to understand various degradation mechanisms and for advancement of SOFC stack operation conditions.