Improvement design and performance assessment of combined cooling and power system using CO2 for waste heat recovery

Waste heat recovery (WHR) is an efficient approach to reducing fossil fuel consumptions and carbon dioxide emissions. In shipboards, gas turbine exhaust can be recovered to simultaneously produce power and cooling for meeting the actual need of marine. The supercritical carbon dioxide (sCO2) power cycles and transcritical carbon dioxide (tCO2) refrigeration cycles have many advantages of compact layout, high efficiency, and environmentally friendly property. Accordingly, combined cooling and power systems (CCPs) integrating sCO2 power cycle with tCO2 refrigeration cycle are considered as competitive and promising WHR systems. However, a large space is still left for CCP to improve its overall performance. In this study, a novel CCP is proposed based on two traditional CCPs. Mathematical models are developed based on the software MATLAB to conduct quantitative parametric analyses, three-objective optimizations and exergy analyses on these systems. The results indicate that compared with two traditional systems, the proposed system can enhance net power output by 40.185% and 35.743% while obtaining a comparable refrigeration capacity and total product unit cost. Exergy analysis indicates that the maximum exergy destructions occur in recuperators and cooler, and the proposed system can significantly reduce exergy destructions in these components compared with two traditional systems.

Automated summary

Waste heat recovery is an efficient way to reduce fuel consumption and carbon dioxide emissions. In shipboards, recovering gas turbine exhaust can provide power and cooling. Combined cooling and power systems (CCPs) integrating sCO2 power cycle with tCO2 refrigeration cycle are considered competitive and promising. This study proposes a novel CCP based on two traditional CCPs and analyzes its performance through parametric analyses, optimizations, and exergy analyses. The results show that the proposed system can significantly improve net power output while maintaining comparable refrigeration capacity and total product unit cost, and reduce exergy destructions compared to traditional systems.