ASSOCIATIONS EVENTS AND EXHIBITIONS
Figure 2 : Greenhouse Gas Emission Forecasts ( from Fyson et al , 2023 ) The forecast shown in Figure 2 , from the ( UNEP RTOC , 2022 ). There is no case for Climate Analytics report ‘ When will global adoption of any alternative considering this greenhouse gas emissions peak ?’ ( 2023 ), good experience so the only change that presents three scenarios . Even the most might be foreseen would be a switch to optimistic of these , where fossil fuel CO2 R-600 , normal butane , which has a higher emissions peak in 2024 , HFC emission critical temperature and offers marginally targets are met and growth trends in wind better efficiency but at the expense of and solar power and in electric vehicles slightly higher compressor swept volume continue at the present rate , only shows a requirements for a given duty . reduction of 10 % in emissions from the peak At the other end of the scale , in industrial value by 2030 . This is good , but not good systems , the development of low charge enough to limit temperature rise to 1.5 ° C . ammonia plant has greatly improved safety
In the refrigeration world analysis of and reliability without any detriment to progress needs to be done on a sectorby-sector basis including consideration of Dreosti memorial lecture 20 years ago , has
efficiency . Carbon dioxide , the subject of the
environmental issues , efficiency issues and been used to great advantage for industrial safety issues . freezer systems and has been applied in
In the domestic refrigerator market , most some other sectors including industrial air production around the world is now based conditioning and large-scale heat pumps . on R-600a , isobutane , and it is estimated The conclusions of the Dreosti lecture in that there are over 800 million of these units 2004 were that the development process in operation , with an excellent safety record for CO2 in the industrial market was nearly
complete , that CO2 was here to stay in the markets that it had reached at that time and that it would be used in other markets too , with product development filling in any gaps in the application range .
For the most part these predictions were correct . There have been attempts to apply carbon dioxide to other industrial applications beyond freezers and heat pumps but with limited success so far . If ammonia is acceptable , as it ought to be in a well-engineered , safe system , then it will likely be cheaper and more efficient than an equivalent CO2 system for an industrial installation . It will always be possible to do a CO2 system at low cost but these solutions are not really feasible in the industrial market as they are expensive to maintain and difficult to keep efficient . They are also likely to have a much shorter life than is expected of an industrial system .
Between the extremes of the domestic and industrial markets the progress in development of environmental solutions to address the climate emergency has been patchier . Good progress has been made in the commercial refrigeration market for supermarkets and smaller convenience stores . Several types of carbon dioxide system have been proved in operation , including CO2 as a volatile secondary refrigerant and transcritical CO2 ( both mentioned in the Dreosti 2004 lecture ) and other retailers have opted for propane as the refrigerant in integral display cases , typically with a low-charge water cooled condenser for heat rejection to a chilled water circuit . Smaller self-contained systems have also used hydrocarbons , for example in bottle coolers , vending machines and icecream cabinets .
The preferred refrigerants for large water chillers are R-134a , R-1234yf , R-1234ze ( E ) and R-1233zd ( E ). These are all suitable for use in centrifugal compressors and still dominate the global market in building services applications . A few projects have been executed with ammonia as refrigerant but these have tended to be special cases . Even fewer have used CO2 or hydrocarbon , generally only as proof of concept installations .
Several designs of chiller have been developed using water as the refrigerant but none of these have yet challenged the dominance of the HFC and HFO chillers in the mainstream market . Chillers using water as the refrigerant can achieve exceptionally high efficiency but they are typically very large and expensive due to the high volume flow rate required .
Mobile air-conditioning has seen its fair share of wrong turns and dead ends over the years . The initial step in replacing R-12 was to move to R-134a but after the Kyoto Protocol was published this was restricted due to concerns about high leakage rates . The European MAC directive (‘ relating to emissions from air-conditioning systems in motor vehicles ’) was published in 2006 and other jurisdictions followed suit . Initially R-152a was proposed but the motor industry rejected it on grounds of flammability so R-1234yf was developed as the preferred option , even though it is also , to an extent , flammable . For a time it seemed that CO2 would be a viable alternative when R-152a was rejected and propane was also proposed as a low GWP alternative , based on many years ’ experience of retrofits to old R-12 systems in the southern US .
12 www . coldlinkafrica . co . za COLD LINK AFRICA • March / April 2025