Potential application of radiative sky subcooling used for CO2 refrigeration system in commercial supermarket throughout the world: Energy saving and decarbonization assessment

To achieve superior coefficient of performance (COP) in supermarket-grade transcritical CO2 booster systems (BASE) through thermodynamic optimization, the radiative sky subcooling CO2 booster refrigeration system (RSSC) is proposed in this study, as the passive subcooling technology of radiative sky subcooling is utilized to subcool the outlet fluid of the gas coole/condenser. The energy efficiency, economics, and carbon emissions performances throughout the life cycle of the RSSC system are evaluated and compared with the baseline CO2 and traditional R404A system used in 10 Chinese cities and 20 cities in different climate zones around the world. The results represent that the new system can significantly improve COP. When the ambient temperature is 35 °C and the solar radiation is 0 W/m2, the COP enhancement ratio is up to 32.52 % compared with BASE. And the system adopting radiative sky subcooling technology can achieve higher APF than the conventional system, the enhancement ratio is 10.86–21.43 %. Moreover, RSSC can reduce life cycle climate performance (LCCP) by 9.56–18.88 % on the basis of BASE in different regions. Meanwhile, the system adopting radiative sky subcooling technology can achieve lower life cycle cost than the conventional system, the reduction rate is 9.18–16.59 %. The payback period is 1.64–4.93 years. Consequently, the radiative sky subcooling CO2 booster refrigeration system has notably potential application, especially in hot regions.