www . refrigerationandaircon . co . za RACA Journal I March 2025 7
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This system will be substantially more complicated even than current variable tariffs and it may require the development of sophisticated new control strategies to maximise the benefits to end users without compromising product quality or operator safety .
It will be difficult to avoid unintended consequences of any complicated new system , such as incentivising ‘ bad behaviour ’ and penalising those who do most to ensure that their system is operated in line with national and international priorities . There may be a role in this control and scheduling exercise for artificial intelligence managing the plant operation , but there is a danger that anything that is too complicated or not sufficiently transparent in control strategy will simply be disabled by the operator if they don ’ t trust it .
In the fluorinated refrigerant sector , the process of change will continue , and it is possible that it will end with fluorinated substances being banned completely , or at best being reserved for essential uses only . At present these fluorinated products have been lumped together into a category known as perfluorinated alkyl substances ( PFAS ) and there are several jurisdictions around the world developing legislation to restrict their use . Most of the fluorinated refrigerants fall into the most common definition of PFAS , which is that the carbon chain contains at least one – CF2 – group in the middle or at least one – CF3 group on the end . However , many of the serious health concerns that are making headlines around the world relate to other forms of PFAS , such as perfluorooctanoic acid ( PFOA ), perfluorobutanesulfanoic acid ( PFBS ) and hexafluoropropylene oxide ( HFPO ).
Conflating these serious health concerns with the widespread use of fluorinated refrigerants is misleading and doesn ’ t help to clarify the advantages and disadvantages of using HFCs and HFOs as refrigerants . One of the quirks of this definition of PFAS is that R-32 is not in this category . We may therefore find that ultra-low GWP substances like R-1234yf are regulated sooner than moderate GWP substances ( R32 is the only single-substance refrigerant in the moderate GWP band ).
The focus has shifted several times over the years ; from ozone depletion to global warming and then from global warming to persistent organic pollutants . At each stage the decisive action taken to address a specific issue has had some unintended and unwelcome consequences . For example , the substitution of R-22 with R404A reduced the ozone depleting potential of a leaked refrigerant from 0.05 to 0 but increased the GWP on the 100-year time horizon from 1,810 to 3,922 – more than double . This accelerated the adoption of lower GWP alternatives like R-410A , but its GWP is still higher than R-22 , at 2,088 ( and it is still designated as ‘ high
GWP ’ according to Table 1 ). The fluorinated chemicals with a low GWP designation are all olefins , with a carbon double bond in the main chain , which means they decompose relatively quickly in the atmosphere and therefore make little contribution to global warming , particularly when measured against the traditional 100-year time horizon . The unintended consequence of this approach is that the end products of the breakdown reaction may not be entirely environmentally friendly , and those substances are transferring into the biosphere much faster than the more stable compounds that they are replacing , as shown in Table 2 .
One of the remarkable things about the data in Table 2 is the implication that some of the R-12 manufactured by Thomas Midgley in the 1920s is still in the atmosphere and has not transitioned into any other substance yet , whereas most of the R-32 released since its introduction to the air-conditioning market in the 1990s has now been transformed into its breakdown products and the HFO released just a few weeks ago has already gone .
Table 2 : Atmospheric Lifetime of Various Refrigerants Refrigerant Type Lifetime * ODP GWP PFAS R-12 CFC 140 years 1.0 10 900 No R-22 HCFC 13.3 years 0.05 1 810 No R-134a HFC 14.6 years 0 1 430 Yes R-32 HFC 5 years 0 675 No R-1234yf HFO 11 days 0 4 Yes
The atmospheric lifetime of the refrigerant is defined ( AR6 , 2023 ) as the mass of substance in a reservoir ( the atmosphere ) divided by the rate of removal from the reservoir . For some substances this is a constant but for others the rate of removal is influenced by the quantity in the reservoir , so it varies as time goes by .
One of the most common breakdown products for most of the refrigerants is trifluoroacetic acid , known as TFA . This is similar in structure to acetic acid , the main active ingredient in vinegar , but with the methyl group ( -CH3 ) replaced with a fluorinated group ( -CF3 ). It is the subject of intense debate between environmentalists and the chemical industry . The chemical producers point out that there are background levels of TFA in the environment all over the world , even on remote islands in the Pacific Ocean , and in deep water samples that are thousands of years old .
These background levels are several orders of magnitude lower than levels that would harm
www . refrigerationandaircon . co . za RACA Journal I March 2025 7