Energy analysis of alternative CO₂ refrigeration system configurations for retail food applications in moderate and warm climates

Refrigeration systems are crucial in retail food stores to ensure appropriate merchandising of food products. This paper compares four different CO₂ refrigeration system configurations in terms of cooling performance, environmental impact, power consumption and annual running costs. The systems studied were the conventional booster refrigeration system with gas bypass (reference system), the all CO₂ cascade system with gas bypass, a booster system with a gas bypass compressor, and integrated cascade all CO₂ system with gas bypass compressor. The weather conditions of London, UK, and Athens, Greece, were used for the modelling of energy consumption and environmental impacts to represent moderate and warm climatic conditions respectively. The control strategies for the refrigeration systems were derived from experimental tests in the laboratory on a conventional booster refrigeration system. The results from the analysis showed that the CO₂ booster system with gas bypass compressor can provide best performance with 5.0% energy savings for the warm climate and 3.65% for the moderate climate, followed by the integrated cascade all CO₂ system with gas bypass compressor, with 3.6% and 2.1% savings over the reference system for the warm and moderate climates respectively.