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GWP, boiling point and glide for A2L alternatives 1000 R-410A R-32 0,7 0,9 R-507 GWP:4265 1,7 4,1 R-22 GWP:1780 R-404A GWP:4214 5,1 5,4 6,8 8,2 12,5 9,7 7,9 26,8 7,2 R-134a GWP:1360 0,4 0,3 R-1234yf 10 0 900 800 GWP:2077 700 600 500 400 300 200 100 0 -55 -50 -45 -40 -35 -30 -25 Boiling point (mid point) Figure 2-2: Refrigerants of safety class A2L proposed since 2010, with values of 100 year GWP, boiling point, and glide. The number next to each blue dot is the glide. The orange dots are selected pure refrigerants introduced before 2010. The boiling point of selected HFC and HCFC refrigerants with zero or almost zero glide are marked with dotted grey lines for comparison. One recent study (McLinden, 2017) started with a database of more than 60,000,000 chemical structures, screening the molecules and finding all to be non-ideal, hence again the need for trade- offs (Midgley 1937, Calm and Didion, 1997). The study is limited to compounds consisting of C, H, F, Cl, Br, O, N or S, as only a small portion of the periodic table forms substances volatile enough to be used as refrigerant (Midgley 1937), the study is also limited to compounds with GWP up to 1000. A main conclusion presented in the study is that the ideal energy efficient, non- toxic, non-flammable, and broadly applicable refrigerant with negligible GWP does not and probably cannot exist. A critique of the study is that it does not include compounds containing iodine, though some of these compounds are volatile enough to be used as refrigerants. Another critique is that compounds with GWP above 1000 can play a role as components of blends, or even as pure fluids during the transition to low and very low GWP refrigerants. The phase-down of HFCs under the Kigali Amendment and under some national legislations is measured in CO2 equivalents. It is difficult to estimate how this will impact specific refrigerants; however, the average GWP in the market can be estimated as a function of time (Pachai, 2018), see figure 2-3 for an illustration. The average GWP gives an idea about which refrigerants can be used in high volume applications, however if a majority of the market uses refrigerants with GWP well below the average, then a few market segments can use refrigerants with GWP significantly higher than the average. Approximately half to two-thirds of a new refrigerant is used for servicing and the design of existing systems limits the flexibility of which refrigerants to use. The lifetime of equipment in the RAC market is 10-20 years (but can be much longer). This means that when a phase-down starts, the service sector will use a very high fraction of the CO2 equivalents available, and the average GWP for new systems will have to come down faster than indicated by the phase down curves. 48 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 100y GWPPDF Image | Heat Pumps Technical Options
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