Modified auxiliary exergy costing in advanced exergoeconomic analysis applied to a hybrid solar-biomass organic Rankine cycle plant

This study concerns advanced exergoeconomic analysis of a hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant. The hybrid plant had been previously conceived as structural optimization scheme to upgrade thermo-economic performance of a real 630 kW solar-ORC plant which currently runs in Ottana, Italy. The irreversibility rates, investment cost rates and irreversibility cost rates were obtained for each system component, based on thermodynamic balance as well as cost balance and auxiliary equations established for the components. Next, the avoidable/unavoidable and exogenous/endogenous splitting options were applied to investigate the sources of thermo-economic losses in the system, the effects of component interactions on the losses, as well as the best approach to improving the system. The main contribution of this paper centers on modification of the traditional auxiliary exergy costing in advanced exergoeconomic methodology, by incorporating stream energy quality into the cost formation process. Results showed that more than 50% of total irreversibility rates can be avoided in almost all of the components of the hybrid plant, most of which are endogenous. Similarly, it was obtained that component interdependencies have little impact on thermo-economic losses. Specifically, more than 60% of irreversibility cost rates could be avoidable in the hybrid plant by optimizing internal operations of each of the system components individually. Moreover, results showed that how auxiliary exergy costing is defined in advanced exergoeconomic method plays a significant role on the analysis, and the modified approach presented in this study is a viable choice.