Exergy and exergoeconomic analyses of multi-energy complementary system based on different natural gas and biogas co-firing ratios considering carbon tax

Abstract

This study analyzes the exergy and exergoeconomic performances of a combined cooling, heating, and power (CCHP) system powered by natural gas and biogas. First, the exergy of the energy and material flows in the investigated co-firing CCHP system is obtained. In addition, the exergy loss and exergy loss distribution ratios of each component as well as the exergy efficiency of the entire system are investigated. Furthermore, the effects of the co-firing ratio of natural gas and biogas on the exergy and exergoeconomic performances are analyzed. Meanwhile, a carbon tax is considered in the exergoeconomic analysis. The results show that the gasifier, two-stage LiBr-H2O absorption chiller, and internal combustion engine indicate the largest exergy loss and exergy loss distribution ratios under different co-firing ratios. The exergy efficiency of the entire system decreases by 3.81% and 4.93% as the co-firing ratio decreases from 1:1–1:10 (natural gas: biogas) in the summer and winter, respectively. The unit exergoeconomic cost (UEC) of multiple products decrease with the co-firing ratio. Finally, a sensitivity analysis is performed to reveal the effects of the co-firing ratio and natural gas price on the UEC of multiple products.