Achieving sustainability in ultra-low temperature (ULT) cold storage using low-GWP refrigerants: A case for the tuna industry in Japan

Cold storage industry consumes significant primary energy for maintaining ultra-low temperature (ULT) conditions. The refrigeration systems in this industry operate in a 24/7/365 environment. Thus, achieving sustainability in the cold storage industry is an urgent task. This study presents a comprehensive 4E (energy, exergy, environmental, and economic) analysis of cascade refrigeration systems (CRS) in Japan's cold storage industry for tuna, comparing alternative refrigerant pairs against the conventional R-23/R-404A as a baseline. The analysis evaluates three refrigerants, namely R-41, R-170, and R-1132a for the low-temperature cycle (LTC), paired with the high-temperature cycle (HTC) using refrigerants Cyclobutene, Cyclopropane, Butene, Iso-Butene, Cis-Butene, Trans-Butene, and 1,3-Butadiene. Results show all proposed refrigerant pairs surpass the baseline, with the R-170/Cyclobutene combination offering the highest efficiency, improving COP by 15.5 % and exergy efficiency by 12.4 %. Using 10 years weather data of eight cities in Japan for the major tuna storage, it is observed that the R-170/Cyclobutene pair delivers up to 8 % annual energy savings. Life Cycle Climate Performance (LCCP) analysis further highlights its environmental superiority, reducing CO₂ emissions by up to 47 % whereas economically, R-170/Cyclobutene achieves a 18.7 % reduction in total annual costs.