Energy and exergy analyses of an integrated thermal system with compressed air energy storage and carbon capture for power, cooling and domestic hot water applications

In this work, an integrated trigeneration system designed for power, cooling, and domestic hot water production is thermodynamically analysed and assessed through energy and exergy methods. The current integrated system consists of different subsystems, including compressed air energy storage, a lithium-bromide/water absorption chiller, a Brayton cycle which uses methane as fuel along with carbon capture, storage and utilization, and two steam Rankine cycles for heat recovery. Overall energy and exergy efficiencies are obtained as 42.96% and 54.45%, respectively. Varying the methane combustion from 810 K to 1000 K increases the overall energy and exergy efficiencies from 39.82% to 42.97% and 44.30%, to 54.45%, respectively. Moreover, increasing the air fuel ratio from 15 to 19 increases the overall energy efficiency from 34.61% to 42.97%; however, this decreases the overall exergy efficiency from 66.98% to 54.45%. Exergy destruction analysis shows that the highest exergy destruction is attributed to the combustor of the main Brayton cycle, with an exergy destruction rate of 22250.49 kW.