Advanced exergy analysis of the combined S–CO2/ORC system

The real origin of irreversibility and improvement possibility of the combined super critical carbon dioxide and organic Rankine cycle (S–CO2/ORC) are investigated based on the advanced exergy analysis. The interaction between topping and bottoming cycles is investigated, for the first time in literature, in addition to the evaluation of interaction among system components. The results show that 34.76% of the overall exergy destruction rate is avoidable, and can be reduced. Also, 61.40% of the avoidable part is endogenous, which can be decreased by modifying the components themselves. Based on the avoidable endogenous part of exergy destruction, the high temperature recuperator, turbine1 and pre-cooler1 have the higher order of improvement priority, respectively. The results also indicate that the major part of inefficiency occurring in the reactor, compressor1 and low temperature recuperator is due to the high temperature recuperator. Another noteworthy result is that 75.4% of the overall exergy destruction occurring in the ORC is emanated from irreversibilities in the S–CO2 cycle and 62.98% of this amount is avoidable. © 2021