Air conditioning and refrigeration have become necessary in modern life, accounting for more than 7.8% of greenhouse gases (GHG) emitted globally. Reducing the environmental impact of these systems is crucial for meeting the global GHG emission targets. Two principal directions must be considered to reduce the environmental impact of air conditioning systems. Firstly, reducing the direct effect by looking at less harmful refrigerants and secondly, reducing the indirect effect by searching for options to improve the system efficiency. This study presents the latest developments in the vapor compression cycle and natural refrigerants, focusing on water as a refrigerant. Natural refrigerants, and especially water, could be the ultimate solution for the environmental problems associated with the operation of vapor compression cycle (VCC) cooling systems, including ozone depletion (OD) and global warming (GW). Reducing the environmental impact of building cooling systems is essential, and the recent system improvements made to enhance the system coefficient of performance (COP) are thoroughly discussed in this paper. Though the cycle improvements discussed in this work are essential and could increase the system efficiency, they still need to solve the direct environmental impact of refrigerants. Accordingly, this paper suggests that natural refrigerants, including water, are the most suitable strategic choice to replace the current refrigerants in the refrigeration and air conditioning industry. Finally, this study reviews the latest VCC system improvements and natural refrigerants in order to guide interested researchers with solutions that may reduce the environmental impact of VCC systems and suggest future research areas.

The rising global warming potential (GWP) of refrigerants, particularly R‐410A and R‐134a, has driven the urgent need for environmentally friendly alternatives in cooling and heating systems. While low‐GWP refrigerants are increasingly available for large and small refrigerant charge systems, a significant gap remains in identifying viable replacements for medium‐charge applications, particularly in high and moderate climate conditions. This study addresses this critical gap by evaluating 15 lower GWP refrigerant options, including hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), hydrochlorofluoroolefins (HCFOs), and hydrocarbons (HCs). The analysis focuses on their direct and indirect environmental impacts, ease of design integration, operational parameters such as capacity and efficiency, and economic feasibility. A novel aspect of this work is including internal heat exchanger performance as a function of refrigerant properties, offering unique insights into how system design can influence cycle efficiency. Key findings reveal that while several refrigerants can effectively replace R‐410A in chiller applications, variable refrigerant flow systems present greater challenges due to performance and safety considerations. R‐447A exhibits superior performance in standard ambient conditions among the studied refrigerants, whereas R‐454B is better suited for high ambient environments. Additionally, refrigerants such as R‐1233zde, R‐1234yf, R‐1234zee, R‐1234zez, R‐1243zf, and R‐1336mzz(Z) demonstrate significantly lower total environmental weighted impact compared to R‐410A, emphasizing their potential for reducing environmental harm. This study advances the current understanding of medium‐charge refrigerant applications, providing actionable insights for researchers, policymakers, and manufacturers navigating the transition away from high‐GWP HFCs.

While forced-air convective systems remain the predominant method for heating and cooling worldwide, radiant cooling and heating systems are emerging as a more efficient alternative. Current radiant cooling systems primarily rely on hydronic chilled water systems. This study introduces direct-expansion radiant cooling as a novel technique that could enhance the efficiency of radiant cooling and reduce its environmental impact. Water (R-718) has been tested as a refrigerant due to its favorable thermodynamic properties and environmental advantages; however, to the author’s knowledge, it has yet to be tested in direct-expansion radiant cooling. This research investigated several refrigerants, including water (R-718), ammonia (R-717), R-410a, R-32, R-134a, and R-1234yf, for this application. The findings indicate that water demonstrates efficiency comparable to other non-natural refrigerants, making it a promising candidate, given its favorable thermodynamic properties and substantial environmental benefits. Despite challenges such as a high compression ratio necessitating multi-stage compression, a high compressor discharge temperature exceeding 300 °C and requiring specialized blade materials, and a high suction volume flow rate, direct-expansion radiant cooling operates within a different temperature range. Consequently, the compressor discharge temperature can be reduced to 176 °C, and the compression ratio can be lowered to approximately 3.5, making water a more viable refrigerant option for this application.