Residential heat pump and air conditioning systems with propane (R290) refrigerant: Technology review and future perspectives

With growing environmental concerns and stricter regulations on high global warming potential (GWP) refrigerants, as well as the potential ban on per- and polyfluoroalkyl substances (PFAS), the quest for sustainable alternatives has intensified. Due to its low GWP and excellent properties, propane (R290) is considered a promising long-term solution. However, safety concerns surrounding its flammability have hindered its widespread adoption in residential settings. This work adopts a critical review framework to evaluate recent advancements in residential heat pump and air conditioning systems utilizing R290 as a refrigerant, offering deeper insights to enhance our understanding of these technologies. It includes aspects such as thermophysical properties, system design and performance, current regulations, and safety concerns. The paper examines the key advantages of R290 that contribute to its superior system performance and summarizes best design practices. It also addresses challenges, such as reducing the refrigerant charge to meet safety standards requirements. Studies have demonstrated that a specific charge of as low as 30 g/kW is attainable. The findings of this review were utilized to evaluate the feasibility of incorporating R290 into various residential systems. This study suggests that employing R290 in small-sized systems such as mini-split and window air conditioners should not pose significant challenges. However, its adaptation into larger unitary systems remains uncertain, prompting the need for further safety assessments and potential updates to safety standards. Furthermore, this review provides a summary of existing research gaps in the current literature and future research directions.