Conventional and advanced exergy investigation of a double flash cycle integrated by absorption cooling, ORC, and TEG power system driven by geothermal energy

Abstract

This study looked at both conventional and advanced exergy analyses of a new combined cooling, heating and power generation system driven by geothermal energy. This cycle consists of a double flash cycle with two thermoelectric generator units and an organic Rankine cycle, besides Li–Br/water absorption cooling cycle. A parametric investigation is performed to indicate the influence of flash cycle pressures and also turbine inlet temperature on the system performance. To evaluate the accurate potential for improving this cycle performance, the first and second-division levels of exergy destruction are determined. In this study, the thermodynamic cycle approach of advanced exergy analysis is used to identify different parts of exergy destruction for each system component. Under real and unavoidable conditions, the system's overall exergy efficiency is 53.38% and 55.83%, respectively. Based on the entire avoidable exergy destruction rate, the system's greatest improvement potential is 9732.4 kW (about 35.35% of total exergy destruction), that 60.01% of this avoidable value being endogenous and 39.99% of avoidable part being exogenous. It is also disclosed that the prioritized order of components acquired by conventional exergy analysis differs from that obtained by advanced exergy analysis for increasing overall system performance. The TEG1, the generator, the TEG2, the LPT, and the condenser1, …are recommended by the conventional, whereas the generator, the LPT, and the absorber, …are recommended by the advanced exergy analysis. Despite having the largest exergy destruction, the data show that the TEG1 seems to have moderate improvement potential.