Most chillers using chlorofluorocarbons (CFCs) have been converted or replaced since the U.S. moratorium on CFC production took effect in 1996, and the chiller industry’s focus has turned to the tradeoffs among next-generation refrigerants. These tradeoffs are embodied by the popular refrigerants R-134a (a hydrofluorocarbon, or HFC) and R-123 (a hydrochlorofluorocarbon, or HCFC).
R-134a has zero ozone-depleting potential (ODP), but its global-warming potential (GWP) is about 11 times greater than that of R-123. R-134a also has a greater indirect effect on global warming than R-123 because the chillers that use it aren’t as efficient at full load (there is some debate as to what the relative effect is at part load). The higher energy use of R-134a chillers at full load results in more carbon dioxide being emitted from the generation of extra electricity. Because R-123 does have a slight ODP, and given U.S. acceptance of the Montreal Protocol—an international treaty to phase out any refrigerant with an ODP—the U.S. Environmental Protection Agency is scheduled to halt the manufacture of R-123 chillers in 2020 and end production of the refrigerant in 2030.
However, some contend the phaseout of R-123 should be rethought because of this refrigerant’s very low GWP and ODP. In effect, this has set up a conflict between the ozone-focused Montreal Protocol and the global warming–focused Kyoto Protocol. It remains to be seen whether the political will can be mustered to change the Montreal Protocol. Regardless of the outcome, obtaining refrigerant for an R-123 chiller should not be a problem for many years. At worst, buyers would have until 2030 to stockpile the small amount of refrigerant that they will likely need to last the lifetime of an R-123 chiller purchased before 2020.
Meanwhile, the search goes on for refrigerants of the future. Mike Thompson, director of environmental affairs at Trane, says that the automotive industry is leading the search because of Europe’s 2011 phaseout of R-134a in automotive applications. Leading contenders include hydrofluoro olefins (such as HFO-1234yf) and carbon dioxide. According to Thompson, the HVAC industry is evaluating the emerging options to identify alternatives that best balance ODP and GWP while being efficient, cost-competitive, and safe.
The phaseout of R-22, an HCFC, on January 1, 2010, will likely result in increased overall chiller efficiencies for one segment of the market because it means that most packaged reciprocating chillers under 80 tons capacity will no longer be available. Small reciprocating chillers use R-22, and Richard Lord, fellow for Carrier Corp., says that most manufacturers are finding it easier to replace them with scroll chillers than to redesign them for use with other refrigerants. Because reciprocating chillers are the least-efficient type available, their disappearance will boost the average efficiency of what’s available on the market.
On the chiller-efficiency front, Lord also says that stricter ASHRAE 90.1 efficiency standards are coming in 2015, which will likely require significant redesign of chiller technology.