Integration of heating and air conditioning into a CO2 trans-critical booster system with parallel compression Part II: performance analysis based on field measurements.

This paper investigates the energy efficiency performance of an integrated CO2 trans-critical booster system providing refrigeration, heating and air conditioning demands of a small-medium size supermarket in Sweden. Using a computer model and input data from field measurements (data presented in part-I of this paper), the system loads and energy efficiencies are evaluated for a warm summer month and a cold winter month. Having analysed the loads hourly and daily, the results show that the system is able to provide the entire air conditioning (AC) demands and a great share of the available heat is recovered for tap water and space heating. It is seen that the refrigeration energy efficiency hasn’t been affected providing the heating and AC demands. Focusing on air conditioning (AC) function of the system, it is shown that the system has high COP values for Tamb<25°C, confirming that it is a suitable solution for northern Europe. On the use of parallel compression (PC) during AC delivery, it is found that COPAC and COPtot of the system are 25% and 8% higher using “AC with PC” comparing with “AC without PC”, respectively. Heat recovery (HR) study indicates that CO2 system provides the heating demands with high COPHR values, usually within the 4-6 range and comparable to majority of commercial heat pumps in the market. To conclude, the energy efficiency study of the integrated CO2 system functions confirm that it can be used as an environmentally friendly all-in-one supermarket energy solution suitable for mild-cold climates.