Energy, exergy, and exergoeconomic evaluations of a micro-trigeneration system

This study presents energy, exergy, and exergoeconomic assessments for a natural gas-fueled micro-trigeneration unit, which encompasses an internal combustion engine (ICE), an absorption refrigeration system (ammonia-water), and a heat recovery unit. The energy system is designed to meet the electricity and cooling demands of a university building, while heat is directed to a biodiesel plant located on site. The analyses comprehended energy and exergy parameters (first and second laws of thermodynamics). Then, the SPECO methodology was applied for the exergoeconomic assessment, which associates monetary values with exergy flows. The ICE presented the highest irreversibility (61.24 kW) and the highest cost of exergy destruction (21.56 BRL/h), followed by the steam generator (5.52 kW and 6.71 BRL/h, respectively). The exergoeconomic assessment indicated the components that could benefit from improvements: steam generator (cooling of exhaust gases before entry into the generator) and the heat exchanger of the absorber (substitution of the exchanger and/or pre-heating of input air). This study contributes to narrow the knowledge gap regarding the exergoeconomic assessment of compact trigeneration systems, besides making a case for the utilization of ICE as prime movers.