Monitoring and Diagnostics of SOFC Stacks and Systems

Abstract

While high performance of SOFC systems has already been achieved, there is still a need to increase the stack lifetime, while decreasing the system’s total cost of ownership, both being linked. The increase in lifetime includes the minimization of performance degradation, but also avoidance of potentially detrimental events during operation, originating from the stack, outside the stack, or a combination of both. The present paper highlights how the detection of faulty operation as early as possible is important to implement adequate mitigation strategies, wherever applicable, according to the fault and its grade of severity. Three types of faults have been considered, fuel starvation, leakage and carbon deposition. Both hardware components and algorithms to monitor, detect, isolate, and finally correct faulty system operation have been developed and will be embedded in a real SOFC system.

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

“…Focus should be therefore given to advanced approaches, where the necessary measurement time is reduced. A promising approach in this regard seems to be a change of the exciting alternating current signal, as can be seen by the works outlined above by Debenjak [110] and Mougins [18] or Nusev et al…”

“…achieving simplified structure with a reduced number of equations as well as good accuracy and validity [18,116]. The basic structure of a hybrid model is given by a physicsbased model, which is extended by a data-based model.…”

“…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].…”

“…This is shown in figure S3 schematically on the typical U/I-curve of a fuel cell with an error-free state (blue dotted line) in comparison to a faulty state (red solid line), which can be caused for instance by fuel depletion. In general, the use of THD and EIS should allow the detection of faulty operating conditions in a SOFC such as carbon formation or fuel depletion at an early stage and suitable countermeasures to be taken in time [18].…”

“…However, main challenges for the SOFC-technology are cost reduction, reduced start-up time, improvement of durability with less degradation caused by the high temperatures and enhanced efficiency of a SOFC-system [5,10,[15][16][17][18][19][20]. Another challenge is the shift of the overall energy system to a high share of renewable energies.…”