This study presents a detailed analysis of energy consumption in supermarkets, combining field measurement and parametric analysis to optimize efficiency using theoretical modelling. Using a 6780 m² supermarket near Stockholm as a case study, advanced technologies were integrated, including CO2 refrigeration cycle with heat recovery, ground boreholes as thermal storage, LED lighting, PV panels, and optimized ventilation. Energy data were collected through sub-metering, synchronized with temperature and pressure measurements of the refrigeration cycle, and analysed to validate EnergyPlus/Python simulations. Simulations used for evaluating refrigeration demands, HVAC loads, and overall energy consumption. Results show a 60 % reduction in energy use intensity comparing to a basic-reference supermarket, achieving 140 kWh/m² annually. Key findings include a 17 % reduction in electricity use with LED lighting, a 55 % decrease in medium-temperature (MT) cabinets’ refrigeration demand and a 64 % drop in space heating demand due by adding doors in the MT cabinets. Integrating heat recovery into the CO2 refrigeration system reduces energy consumption by an additional 7 %. Thermal storage further improved system efficiency by optimizing subcooling, while photovoltaic panels reduce grid dependency by 29 %. These results demonstrate the potential of modern technologies to improve energy performance and sustainability in the retail sector, offering actionable insights for designers and policymakers.

The benefit of two-stage heat recovery compared to one-stage heat recovery is not deeply investigated in CO2 refrigeration systems with heat recovery in supermarkets. Moreover, the optimum discharge pressure respecting the thermodynamic principles governing the heat recovery heat exchangers, has not been defined. This study addresses this research gap combining existing knowledge of the pinch point in CO2 heat pump gas coolers and supermarket refrigeration systems with heat recovery. This novel approach leads to more accurate control and design inputs for the commercial refrigeration industry. Key findings of the study in a Swedish supermarket show that two-stage heat recovery, compared to one-stage, improves the Seasonal Performance Factor for heat (SPF) by 17 %, with the refrigeration cycle's annual energy savings reaching up to 4 % in cold climates. Additionally, heat export capabilities to district heating networks are explored, demonstrating a 25 % efficiency improvement with a two-stage configuration instead of a one-stage configuration. Moreover, increasing the discharge pressure by less than 5 bar compared to the optimum value can reduce the total required UA-value of the heat recovery heat exchangers by 45–48 %, with a maximum SPF penalty of 2.8 %

Overfeeding the medium temperature level evaporators using liquid ejectors is one of the features of the modern CO2 refrigeration systems for supermarket applications, which provides higher evaporation temperature. The liquid leaving the evaporator is accumulated in a liquid receiver before the compressor and is pumped back to the main receiver before the evaporators by the liquid ejector. This paper uses field measurements of two supermarkets in Sweden. One of the supermarkets is analysed in two days where it operates under overfeed conditions at one day and under dry expansion conditions at the other, providing better understanding of the benefit of overfeeding the cabinets. The first system shows that the evaporation temperature is increased by 2 K (from -6 degrees C to -4 degrees C) while the air set point temperature inside the cabinet is kept satisfied. The second system shows that the evaporation temperature can be up to -2.5 degrees C with a small impact in the cabinets' air set point temperature satisfaction.

This study explores the capability of a supermarket to fulfill the thermal demands of neighboring buildings. The research combines field measurements analysis, obtained from a Swedish supermarket which covers the neighbors' thermal demands, with theoretical calculations, using thermodynamic models of the refrigeration system and the ground source thermal storage. In contrast to previous studies, this work is unique in its use of demonstrating a real-life built case study rather than only theoretical approach. Results demonstrate that inte-grating ground source storage in a supermarket can meet the thermal demands of neighboring buildings without requiring additional equipment. The refrigeration system accounts for 80% of the total heat demand, while the ground serves as a heat source for the rest. This approach results in 67% annual operating cost savings for the neighboring buildings. In addition, ground source subcooling provides 9% annual energy savings to supermar-ket's refrigeration system. By exporting heat to neighboring buildings, the proposed solution emits 90% less CO2 in Uppsala and 67% less in Stockholm compared to solutions in which the refrigeration system only meets the refrigeration demands. Summing up, the concept of utilizing supermarkets to meet thermal demands offers a more energy-efficient operation for both supermarkets and property owners while significantly reducing annual energy consumption and emissions.

This paper presents the performance analysis of a well-instrumented supermarket in Sweden where heating, air conditioning and ground storage are integrated into a booster trans-critical CO2 refrigeration system. The supermarket has applied several features of a state-of-the-art system, including overfeed evaporators, 2-stage heat recovery, and air conditioning. Two warm and two cold days operation are used for the control and the performance investigation. The heat recovery follows the theoretical control strategy, where the setpoint temperature for the discharge pressure is the forward water temperature to the heating system. The combination of low water temperature return from the space heating system and 2-stage heat recovery provides efficient operation; COP heating is estimated around 6. The warm days study shows that importance of fast fault detection which resulted in 16% energy savings in this case study. The fault drives to limitation of the air conditioning capacity and as result indoor temperature increment. The air conditioning COP is estimated around 2.5 for both warm days, with potential of 20% increase in the COP with optimized operation without thermal leakage to the ground.

The energy outlook of a supermarket in Stockholm, as well as its refrigeration cycle efficiency are investigated based on field measurements. The refrigeration unit of the system is a CO2 trans-critical booster system with heat recovery, air conditioning, and geothermal storage integration. Field data are analyzed from 1st of January 2019 until the end of the same year. Based on the field measurements, low, medium temperature level, air conditioning cooling and space heating demands, as well as COP’s are calculated, for thirty-minute intervals, averaged to different ambient temperatures. The same method is used for calculating the thermal loads from the ground. The results show energy efficiency improvement comparing to previous studies, which originates from several factors such as: changes in the system design (e.g. three stage expansion), higher total efficiency of compressors, zero or low internal superheat at the three evaporation temperature levels resulting in higher evaporation temperatures. The COP for the medium temperature level reaches 8,5 and 7,5 for space heating.

This paper investigates the theoretical energy outlook of a supermarkets in Stockholm, as well as the energy efficiency of its refrigeration unit. The refrigeration unit is a CO2 trans-critical booster system with air conditioning and geothermal storage integration into the medium temperature level. This stage is operated under overfeed conditions (zero internal superheating) thanks to liquid ejectors. On the other hand, the freezers operate under direct expansion with an optimum superheat. The supermarket is heated up by reclaimed heat from the refrigeration unit. Two heat exchangers are integrated after the high-stage compressors where water is heated for tap water and space heating.

The simulation is done for a supermarket in the design stage as part of a study that will continue by collecting data from the supermarket when is in operation to evaluate its performance and compare to the results from the design phase. The cooling demand of the medium temperature level is estimated between 100-140 kW depended on the ambient conditions and around 40 kW for the freezers. The COP in the medium temperature level is expected to be up to 7.8 and 2.5 for the low temperature level. The space heating COP is expected to be up to 7.3.

Heat recovery makes CO2 trans-critical solutions more competitive. The heat recovery can be achieved in one stage or in two stages by using two de-superheaters in serial, because of the CO2 temperature profile. An Engineering Equation Solver (EES) model was developed in order to analyse what are the best operating conditions for an ice rink refrigeration system in 3 different heat recovery scenarios, respecting real de-superheater properties. The scenarios are an one stage which provides water heating from 20 ºC to 60 ºC, an one stage with 20 ºC to 70 ºC and a two stage with 20 ºC to 70 ºC. According to simulated results the refrigeration system can be more efficient if it operates under specific discharge pressure and subcooling. An optimum control strategy has been designed according to each scenario and the heat demand. Results show that the power consumption in the two-stage solution is 10% lower than the one stage scenario from 20 ºC to 60 ºC. The two-stage solution provides higher quality energy by consuming less electrical power.