Energy Efficiency Assessment,based on Field Measurements andComputational Simulations : A Swedish Hypermarket’s case study

Abstract: This study aims to compare the energy consumption of a supermarket according to field measurements and results from building’s simulation software. Additionally, measures of energy efficiency to minimize the energy intensity of the supermarket are investigated. For such purpose, an ICA MAXI hypermarket in Bålsta, Stockholm, with a total conditioned area of 6570 m2 has being under analysis. This hypermarket operates with a trans-critical CO2 booster refrigeration system, which allows to recover the heat taken out from the refrigeration cabinets to warm up the sales area, when necessary and the only energy source it uses is electricity. Ground source energy storage is used to store part of this heat and enable an effective space heating and domestic hot water supplies. This system is also responsible to provide the required space cooling. In that sense, the referred hypermarket is using the state of the art refrigeration system for supermarkets in cold climate’s countries. Results from the field measurements performed in 2021 showed a total electricity consumptionof 1734 MWh, which corresponds to 264 kWh/m2. This value is in accordance with several studies’ conclusions. However, the values predicted by the simulation tools appointed a lower annual consumption. EnergyPlus and CyberMart software were used to simulate the power loads of ICA MAXI. Subsequently, a Python tool was used to compute the energy consumption by the refrigeration system, taking into account the demands found on the building’s simulation tools. In the end, EnergyPlus’ model predicted an annual energy consumption of 1347 MWh, which equals 205 kWh/m2. Out of the 387 MWh gap, 266 MWh are due to the assumptions taken for the energy consumed by the electrical appliances, 120 MWh resulted from the non-optimal control strategy used on the refrigerationsystem and the remaining 48 MWh were related to different outsides temperatures, predicted on the model and field measurements. This allows to conclude that by managing the current refrigerationsystem in an optimal way, 77.6 thousands of swedish kroner may be saved and the equivalent of about 11 tons of CO2 can be avoided annually. The final results from CyberMart tool were close to the EnergyPlus’ ones and this software was found to be much more user-friendly. In addition, with the aim to identify energy efficiency measures to be applied in this hypermarket, several scenarios were constructed in EnergyPlus, by changing the temperature setpoints of the system, the infiltration rate and the store’s location. Findings pointed out that adapting the indoor temperature for Summer and Winter months can lead to energy savings.