4. Models for Diagnostic Applications

The correct operation of an SOFC system is ensured by combining optimal design and effective control and diagnostic strategies, to guarantee system efficiency and prevent excessive degradation or undesired faulty states. In this way, system lifetime can increase and market requirements be fulfilled, with a consequent growth in SOFC systems production and market deployment. The aim of a diagnostic algorithm is to detect and isolate undesired events (i.e., faulty states) within the entire system (i.e., stack and ancillaries). During faulty operation, the inference on the system state can feed suitable control strategies in order to drive the system toward a safer operating condition, ensuring in such a way a continuous operation to the final user. The current chapter gives an overview on the development of a suitable diagnostic algorithm, based on a model-based approach. The main features are illustrated and discussed, with focus on the dominant issues to be addressed for their optimal design. The background on model-based diagnosis is summarized along with the basic concepts of diagnostics. Details on the theory behind are available in the main references reported throughout the chapter. Several applications dedicated to an SOFC system are presented to exhibit the diagnostic algorithm capability of suitably detecting and isolating different kinds of faults.