Thermoeconomic assessments and optimization of a vapour compression and an ejector integrated sCO2 trigeneration systems

Abstract

Two sCO2 trigeneration systems are proposed in this study to supply power, heating and cooling simultaneously, one is a vapour compression recuperation system (VCRS), the other is an ejector integrated recuperation system (EIRS). Their performance assessments are conducted from thermoeconomic point of view. In a recuperative base case scenario with cooling capacity of 100 kW, the transcritical VCRS has the ability to provide 46.5 kW power output with the trigeneration utilization efficiency of 160 % and exergy efficiency of 49.92 %, while the transcritical EIRS can deliver 54.43 kW power with the trigeneration utilization efficiency of 158 % and exergy efficiency of 54.41 %. The effects of key operational parameters are evaluated, including the maximum cycle pressure, minimum and maximum power cycle temperatures, evaporation temperature and trade-offs between thermoeconomic points. Multi-objective optimization is carried out based on the identified trade-offs. It is found that the VCRS exergy efficiency increases 4.51 % when the minimum exergy cost rate rises 13 %, the EIRS exergy efficiency improves 4.21 % as the minimum exergy cost rate goes up 14 %.