Next generation of refrigerants—historical review, considerations and outlook

Reviews the progression of refrigerants, from early uses to the present, and then addresses future directions and candidates. Breaks the history into four refrigerant generations based on defining selection criteria. Discusses displacement of earlier working fluids, with successive criteria, and how interest in some early refrigerants re-emerged, for example renewed interest in those now identified as “natural refrigerants”. Examines the outlook for current options in the contexts of existing international agreements, including the Montreal and Kyoto Protocols to avert stratospheric ozone depletion and global climate change, respectively. Also examines other environmental concerns and further and international and local control measures. The discussion illustrates how isolated attention to individual environmental issues or regulatory requirements, in contrast to coordinated responses to the several issues or regulatory together, can result in unintended environmental harm that almost certainly will require future reversals. It identifies pending policy and regulatory change that may impact the next generation of refrigerants significantly.