Comparative analysis of causal diagnosis methods of malfunctions in power cycles

AutoresUson Gil, Sergio
Año publicación2008


The word diagnosis refers to the activities aimed at the detection of anomalies in any system. In general, the interest of locating these anomalies appears because they can lead, if not solved, to catastrophic effects. In energy systems, besides this kind of failures that potentially originates component breaking and, perhaps, plant shut off, there are other anomalies which are of interest. These situations might never originate a catastrophic failure but may entail huge economic expenses due to the additional fuel consumption they cause. In this context, it is interesting not only to detect anomalies but also to quantify the effect of each one of them in the variation of fuel consumption. This quantification is crucial in order to decide whether or not to repair or replace a component.

This task is the objective of thermoeconomic diagnosis. Thermoeconomics can be considered as the science of energy saving and emerges from the combination of the Second Principle of Thermodynamics and Economics. It provides several tools and concepts to deal with the diagnosis problem. The main of them is the fuel impact formula, which links the variations of the unit exergy consumptions of the plant components (the indicators of their individual behaviour) to the fuel increment they cause. Thermoeconomic analysis provides a solid conceptual basis for the diagnosis, but in the practical application to real examples, difficulties appear because of the problem of induced effects. The presence of these effects makes it more difficult to identify the components where anomalies take place, and the development of methods to eliminate them is a wide field of research. (Valero et al., 2004a,b).