Exergy, carbon footprint and cost lifecycle evaluation of cascade mechanical subcooling CO2 commercial refrigeration system in China

The concept of cascade mechanical subcooling is recommended to widen the application of natural working fluid CO2, improve the efficiency and reduce the carbon footprint of CO2 refrigeration system applied in commercial supermarket. Three potential configurations for CO2 system with integrated multi-stage dedicated mechanical subcooling (MS-DMS) are proposed as prospect solutions. Life cycle assessment is conducted from the viewpoint of exergy, carbon footprint and cost performance for the proposed refrigeration systems, and compared with baseline CO2 booster refrigeration system (BASE) and traditional R404A system. 8 representative cities located in diverse climatic zones across China are chosen as scenarios and discussed in detail. The results indicate the irreversible loss is efficiently reduced with the utilization of MS-DMS. The annual exergy efficiency of CO2 system integrated with triple-stage DMS (TS-DMS) is 11.92-18.48% higher than BASE. Life cycle climate performance (LCCP) is reduced by 6.87% when the TS-DMS is employed in Haikou in contrast to BASE from the perspective of carbon emissions. Additionally, the life cycle cost (LCC) is remarkably reduced by 6.8% compared with BASE. Consequently, MS-DMS CO2 systems are more suitable for the application in warm or hot regions in contrast to BASE due to its better emission reduction performance as well as lower life cycle cost.