The TEWI is the more important attribute to consider when selecting a refrigerant for a new design, even though the number varies with the environment. The TEWI reflects the direct warming potential, and it also reflects the indirect effect of providing energy to achieve the cooling required. Therefore, a more efficient refrigerant requires less energy, which results in a lower TEWI. See the quote that follows: “Gopalnarayanan (1999) examined eight different refrigerants as possible substitutes for R-22. He found that for all eight refrigerants, the direct GWP effect of a refrigerant represented less than 7.5% of the TEWI at performance rating conditions. This means that the indirect effect of a system’s energy efficiency is more than 13 times more important than GWP. Therefore, TEWI, which considers both the direct and indirect global warming effects of a refrigeration system, is a much more accurate indicator.
In addition, Gopalnarayanan (1999) also found that of all eight refrigerants examined, Puron refrigerant (R-410A) had the best performance from the point of view of energy efficiency and TEWI.” (PURON® REFRIGERANT R-410A)
An Argument for R-410a
Some European manufacturers are saying that R-134a is the best refrigerant to select for the PCA due to its GWP (1300 as compared to 2000 for R-410a). I am saying that R-410a is a better refrigerant, because it is more efficient and has a lower TEWI despite its higher GWP. In addition, the coils of an R-410a system can be as much as 20% smaller than an R-134a system. Thus, the R-410a system is physically smaller, is more efficient, and requires less refrigerant for the same cooling.
When legal acceptance, physical size, cooling performance, and cost are all considered, then R-410a is the logical choice for the PCA application. Some may try to argue that components — expansion valves, for example — are available for R-407c but not R-410a, because R-410a is a newer refrigerant. However, components are available. Manufacturers have been developing them since the “worldwide” transition started 11 years ago.
When the acquisition cost for a given performance, the energy efficiency related to the cooling medium, and the environmental impact of the refrigerant are all considered, R-410a is the clear choice for the PCA application.