Analysis of Energy Performance Indicators for Supermarket Buildings

Abstract: In the sector of food retail, supermarkets are common all over the world with their presence projected to increase further. They are also the most energy intensive amongst commercial spaces on an area basis, along with having direct emissions through refrigerant leakage. Energy efficiency and overall environmental impact of supermarkets are hence important areas of research. This study aims to investigate performance indicators for supermarkets through 3 case study stores using CO2 refrigeration. This is to be done by evaluating existing indicators and developing new ones based on field measurement data. Sales area as a primary performance indicator is commonly used for supermarkets. However, there is a need for additional indicators validated by reliable field data to further improve supermarket benchmarking as well as estimation of their energy demand. Total area, sales area, installed refrigeration capacity, outdoor temperature, opening hours and connected refrigeration load were studied, selected based on literature review and available data. The effect of outdoor temperature on energy demand yielded a trend which was consistent with the behaviour of climate dependent subsystems, heating and cooling. The total energy demand increases at high or low outdoor temperatures while remaining relatively constant between -4 and 15°C. Also, the impact of opening hours was studied by calculating the effect of closing of store on energy demand. A reduction of 36% upon closing of store was observed for one of the case studies. Normalised weekly opening hours (NWOH) was then formulated to account for the impact of varying opening hours on energy demand. Primary energy was also explored in the study for better comparability of energy use, accounting for both electricity and heat. Performance indicators based on opening hours and outdoor temperature can hence be explored using the foundation laid down in this study, through further research and reliable data across a wider range of climates and opening hours.