Thermo-economic assessment of a novel trigeneration system based on coupling of organic Rankine cycle and absorption-compression cooling and power system for waste heat recovery

Abstract

A novel trigeneration system consisting of organic Rankine cycle (ORC) and absorption-compression cooling and power system (ACCPS) is proposed to recover diesel engine waste heat. A compressor is used between evaporator and absorber in ACCPS. Moreover, a screw expander is applied in ACCPS to increase power generation and domestic hot water (DHW) is prepared by DHW heat exchanger (HX) in ORC. Exergoeconomic analysis using the specific exergy costing (SPECO) method is implemented for system assessment. Base case and parametric analysis as well as the effects of using expander and compressor in ACCPS on total performance of the system are examined. The results show that the best thermo-economic performance of the system is achieved when ORC condensation temperature and generator outlet temperature have respectively the lowest (85 °C) and the highest (80 °C) values. It is difficult to select the proper ORC evaporation temperature, because the lower this temperature is, the higher net power output is obtained while higher ORC evaporation temperature leads to less total cost rate and more total energy efficiency of system. Moreover, system exergy efficiency has an optimum point versus variation of ORC evaporation temperature. By increasing expander inlet steam quality, ACCPS coefficient of performance (COP) and total energy efficiency of system decrease; however, due to increase in net power output and system exergy efficiency respectively equal to 18.23% and 3%, total system performance improves from exergy viewpoint. By utilizing a compressor in ACCPS and increasing its pressure ratio, the performance of ACCPS improves from energy viewpoint; however, system thermo-economic performance decreases.