State-of-the-art review on the CO2 combined power and cooling system: System configuration, modeling and performance

Owing to its excellent physical properties, CO2 has been extensively used as a working fluid in power cycle and refrigeration cycle. To improve energy conversion efficiency, various CO2 combined power and cooling systems have been proposed and studied in recent years. To overcome the issues of high operating pressure and condensation difficulties of the CO2 system, it’s proposed to mix CO2 with organic fluids, and the system performance of CO2 mixtures has been extensively investigated. To better understand these existing studies and determine the future research directions, a state-of-the-art review of CO2 combined power and cooling systems is presented. First, various configurations of the combined system are introduced. The structures involved in power and refrigeration cycles are also comprehensively reviewed. Further, the existing models, including steady-state and dynamic models for system performance analysis, are presented. Thereafter, employing CO2 and CO2 mixture as the working fluids, system performances of power, refrigeration, and combined cycles are determined. The review finds out that configurations of existing system originate from the experience of researchers, the optimal organic fluids of CO2 mixtures is usually found by a trial-and-error method, and there are still no unified system construction and fluid selection criteria. The analysis on CO2 system mainly concentrates on the steady-state performances, the researches on dynamic performances and experiments are still limited. In the future research, the intelligent construction of system structures, the screening of organic fluids in CO2 mixtures, dynamic simulation and experimental research on the proposed systems are promising directions.