Seasonal performance evaluation of CO2 open refrigerated display cabinets

An increasing number of supermarkets and convenience stores has led to a proportionally higher demand for open refrigerated display cabinets (ORDCs). Ease of access to refrigerated products is the main advantage of ORDCs; however, they also exhibit high cumulative energy consumption as well as direct and indirect CO₂ emissions. This work aims to formulate, establish, and apply a seasonal performance evaluation method for ORDCs and "walk-in" type refrigerated device driven by CO₂ chillers. First, a thermodynamic modeling approach is used and fitted to experimental data. The relative error between the predicted and actual heat load is within ±10%, whereas it is within ±20% for the normalized compressor electric input. Then, an evaluation tool is constructed using the seasonal energy consumption of ORDCs commonly used in Japan and driven by a transcritical CO₂-compression chiller within Japanese climatic conditions. This tool can be used to predict the annual energy demand for given ambient conditions as well as the reduced environmental impact of multiple combinations of refrigerated display cabinets compared to conventional HFC/HCFC-based systems. According to the annual temperature distribution in chosen regions, the annual thermal load, annual electricity consumption, and annual coefficient of performance are calculated and analyzed. Simulation results quantitatively evaluate the beneficial effect of T_e as being translated to a better COP, and lower energy consumption and CO₂ emissions. Considering the geographic location of the store, the quantitative results show how a hotter climatic condition leads to higher energy consumption and CO₂ emissions, and lower COP. The proposed evaluation method is generally applicable to any regional setting and any chiller-ORDC combination.