Retrofitting Supermarket Refrigeration System with CO2 Heat Recovery : A Comparative Study

Sammanfattning

Supermarkets are among the most energy-intensive commercial buildings, with refrigeration systems responsible for nearly half of their electricity use. Many refrigeration systems still rely on hydrofluorocarbon (HFC) refrigerants such as R404A, which face regulatory phase-out due to their high climate impacts. As a response, CO₂ systems are increasingly adopted as sustainable alternatives. This study presents a case analysis of a Swedish supermarket that retrofitted its HFC system with a CO₂ transcritical booster system. Technical, economic, and environmental performance were compared, with emphasis on heat recovery. Simulations were conducted using a KTH-developed heat recovery tool for the CO₂ booster system and CyberMart for the HFC system, supported by real Swedish energy price and carbon intensity data. Results show that the CO₂ booster system recovers 629 MWh of heat annually, meeting 94% of the supermarket’s space heating demand and enabling 9 MWh of export, compared with 361 MWh recovered by the HFC system. The seasonal COP for heat recovery is 4 for the CO₂ booster system and 3.1 for the HFC system. The CO₂ booster system’s performance is comparable to that of high-efficiency heat pumps. Economically, the CO₂ booster system reduces annual energy costs by 32%. Environmentally, it lowers annual CO₂ emissions by 63%, with even greater reductions when refrigerant leakage is considered. Overall, the findings demonstrate that CO₂ booster systems with heat recovery provide clear advantages for supermarket retrofits, functioning simultaneously as refrigeration system upgrades and heat pump retrofits tailored to supermarkets.