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• From HFCs to HFOs : Hydrofluoroolefins ( HFOs ) with shorter atmospheric lifetimes have emerged as the latest alternative , though they bring new environmental concerns about their breakdown products .
Each transition has introduced technical challenges , from adapting technologies to new refrigerants to addressing safety issues with substances like R-1234yf . While each step has been difficult , it has paved the way for more complex solutions in the ongoing quest for better refrigeration technologies .
REFINING REFRIGERATION : PROGRESS AND COMPROMISES The evolution of refrigeration technology has seen substantial achievements but also numerous setbacks . Early refrigerants like R-404A , a blend of R-125 and R-143a , were effective in addressing ozone depletion but had high global warming potentials . Although R-404A was a suitable alternative to R-22 in the 1990s , it fell out of favor as the focus shifted to low GWP fluids .
Balancing ozone depletion and global warming has led to compromises . Simple metrics like GWP ratings do not capture the full spectrum of environmental impacts , making the transition an ongoing process . The GWP logarithmic scale helps set regulatory standards , guiding the shift toward more environmentally friendly options .
Advancements in natural refrigerants have gained traction . Hydrocarbons like propane ( R-290 ) and isobutane ( R-600a ) are effective and safe alternatives , with R-600a becoming widely adopted . Carbon dioxide , though effective in commercial applications , remains costly and less efficient compared to HCFCs and HFCs . Ammonia has seen a resurgence in industrial applications , where modern systems have mitigated leakage risks .
The introduction of air cycle systems , though historically significant , remains niche due to its limited commercial use .
EVALUATING PROGRESS AND FUTURE DIRECTIONS As we approach 2025 , it ' s essential to assess refrigeration technologies in the context of broader climate agreements . The Vienna Convention and Montreal Protocol , along with regulations like the European F-gas regulations and the U . S . AIM Act , have successfully addressed ozone depletion . Ozone levels are expected to recover to 1980s levels by around 2060 , a significant achievement .
However , addressing global warming has proved more challenging . The Paris Agreement aims to limit temperature rise to 1.5 ° C above pre-industrial levels , but current emission reduction forecasts fall short . Optimistic scenarios suggest only a 10 % reduction in emissions by 2030 , which is insufficient to meet the targets .
RACA Journal I November 2024
In refrigeration , progress must be evaluated based on environmental impact , efficiency , and safety . R-600a remains the dominant and safest option for domestic refrigerators , with minor efficiency improvements expected . Industrial systems have seen enhancements with low-charge ammonia plants , and carbon dioxide has proved effective in industrial freezers . Ongoing development is expected to address remaining gaps .
FUTURE REFRIGERATION TECHNOLOGIES Predictions about CO 2 in refrigeration have largely proved accurate . While CO 2 has seen success in freezers and heat pumps , its use in other industrial applications remains limited . Ammonia is typically more cost-effective and efficient compared to CO 2 systems , which , despite low initial costs , have high maintenance expenses and shorter lifespans . Commercial refrigeration has made notable strides . Various
CO 2 systems , including CO 2 as a volatile secondary refrigerant and transcritical CO 2 systems , have proved effective . Retailers have adopted propane in display cases and hydrocarbon systems in smaller appliances .
For large water chillers , refrigerants like R-134a , R-1234yf , R-1234ze ( E ), and R-1233zd ( E ) are prevalent , while ammonia and CO2 are less common . Water-based chillers , though efficient , have not surpassed the dominance of HFC and HFO chillers due to their size and cost .
Mobile air-conditioning has faced challenges with refrigerant transitions . R-134a replaced R-12 but raised leakage concerns , leading to the European MAC directive . R-152a was initially considered but rejected due to flammability . R-1234yf is now predominant despite flammability concerns . CO2 and propane were considered but did not gain widespread acceptance .
Heat pumps vary by application . Ammonia and HFO- 1234ze ( E ) are competitive in district heating , with CO 2 systems emerging but not yet widespread . HFCs are common in smaller heat pumps , with CO 2 used in water heaters for heating mains water .
Over the past 30 years , efficiency improvements have been significant . In the US , residential air-conditioner efficiency increased by 30 % from 1992 to 2015 . Despite this , many systems still fall short of their efficiency potential , with some cold storage facilities consuming ten times more energy than best practices .
NEXT STEPS Future progress will depend less on refrigerant choice and more on cleaner energy sources and transitioning processes to electricity . Cleaner electricity is essential for reducing CO 2 emissions , and shifting processes from fossil fuels to electricity is equally crucial . Success in one area without the other will not prevent severe climate impacts . The relationship between grid decarbonisation and electrification is key .
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