Enhancing CO2 supermarket refrigeration efficiency by raising the medium-evaporation temperature through zero-superheat operation

• Zero-superheat CO 2 systems cut annual energy use by 6–16 % across Europe. • 3 K rise in MT evaporation temperature can save up to 16 % of energy • Findings support next-generation CO₂ refrigeration for decarbonized retail. This work investigates the energy performance of advanced CO₂ refrigeration architectures for supermarkets operating with zero-superheat medium-temperature (MT) evaporators, compared with conventional dry-evaporator systems. Two reference systems: parallel compression booster (PC) and integrated mechanical subcooling booster (IMS); and three advanced solutions: gas–liquid ejector booster (GLEj), low-pressure lift ejector with liquid pump (EjLP), and integrated mechanical subcooling with liquid subcooling and zero-superheat evaporators (IMS+) have been analyzed. The systems were thermodynamically optimised for a medium-size supermarket (240 kW MT, 40 kW LT) and their annual performance was evaluated across 282 European locations using typical meteorological data. Results demonstrate that raising the MT temperature from –6°C to –3°C, made possible by zero-superheat operation, leads to substantial energy savings. Compared with the parallel compression booster, annual reductions range from 6 to 7% for the GLE, 9 to 16% for the EjLP, and 14 to16% for the IMS+. Relative to the IMS, the IMS+ achieves 6 to 8% savings, particularly in southern Europe.