Conventional and Advanced Exergy Assessment of a Solar-Assisted Trigeneration System based on Direct Steam Generation

This work performs conventional and advanced exergy assessments on a trigeneration system supported by solar-powered direct steam generation (DSG). The system utilized parabolic trough collector (PTC) as the energy source, a Rankine cycle for electricity generation, a ground-source heat pump (GSHP) for building heating, and heat exchanger (HX) for domestic hot water (DHW) production. Exergy assessment is executed to identify the exergy destruction and critical equipment in the system. Advanced exergy assessment is performed to determine what proportion of the exergy destruction calculated in the exergy examination is endogenous, exogenous, avoidable, or unavoidable. Thus, the advanced exergy assessment more clearly pinpoints the equipment in the system having potential for enhancement. Exergy efficiencies of the system under real, unavoidable, and ideal conditions are calculated as 20.55%, 25.43%, and 36.42%. For all three cases, the maximum exergy efficiency is achieved in the ground heat exchanger (GHX), while the lowest exergy efficiency is attained in the evaporator. The PTC experiences the greatest exergy destruction, amounting to 19.2 MW. Approximately 0.42 MW of exergy destruction in the PTC is endogenous and avoidable, approximately 8.11 MW is endogenous and unavoidable, approximately 6.74 MW is exogenous and avoidable, and approximately 3.92 MW is exogenous and unavoidable.