Exergy analysis of solar collectors, from incident radiation to dissipation

It is essential to know the actual exergy input of solar radiation in a given location in order to establish the exergy budget of a solar collector or any other solar-powered process. To do so, the theories on the entropy of attenuated radiation must be re-interpreted before developing a method for evaluating the exergy flux from meteorological data. It then becomes possible to build a generic framework for describing the exergy budget of solar collectors. Three main types of exergy losses can be identified in this way. The first is related only to the type of technology chosen for the collector: flat-type collectors and highly concentrating collectors do not have same exergy losses. The second type of exergy loss is related mainly to heat dissipation, showing that all dissipated heat fluxes can be combined as the overall exergy loss. The third type is related to the utility furnished by the collector. Graphical examples are shown in a diagram that provides more information than the Sankey diagram. (C) 2012 Elsevier Ltd. All rights reserved.