Comparative Evaluation of Ammonia (R-717) and Isobutane (R-600a) for Cold Storage Systems: Energy Efficiency, Environmental Impact, and Safety Considerations

Abstract

Cold storage refrigeration systems contribute to environmental concerns because they widely use refrigerants with high global warming potential (GWP) and ozone depletion potential (ODP). The transition toward environmentally sustainable refrigeration technologies requires alternative refrigerants that provide high energy efficiency while satisfying environmental and safety requirements. This study investigates ammonia (R-717) and isobutane (R-600a) as alternative refrigerants for cold storage applications, focusing on energy performance, environmental impact, and safety aspects. A vapor compression cycle model was simulated under typical operating conditions (evaporator at –25 °C, condenser at 40 °C, and cooling load of 25 kW). The results indicate that R-717 achieved the highest coefficient of performance (COP = 2.00) with minimal energy losses but requires strict safety controls because of its toxicity. R-600a exhibited a slightly lower COP (1.82) but an almost negligible global warming potential and ozone depletion potential. Both refrigerants offer efficient, sustainable alternatives to conventional refrigerants, supporting the transition to low-emission cold chain systems aligned with the Montreal Protocol and Kigali Amendment goals.