In 1990′s the most popular choice for car AC refrigerants was R12.It was manufactured by Dupont and marketed as Freon. It was chlorine based (HFC or HYDRO FLUORO CARBON) and has a very high warming potential (8500). It was banned in the 90′s because of its adverse effect on Ozone layer and search for green refrigerants started.
R134a refrigerant replaced R12 for charging Car AC’s as it was effective in cooling and has a 7 times less warming potential (1400) than R12.In recent years ,EPA has announced
• All the vehicle models starting from 2011 has to use a refrigerant with a warming potential of less than 150.
• Starting from 2017 all new vehicles sold will have to meet the low global warming potential requirement.
Since the warming potential of R134a is more than 150, the EPA decided that it will be phased out by 2011 and a complete ban will be implemented by 2016.
Take a look at some of the alternatives
It was one of the contenders to replace R134A in car ac systems. It is HFC based refrigerant with the warming potential between 120 to 140.It is slightly flammable because using hydrogen in place of chlorine makes the molecules less stable. It is losing the battle to replace R134A because of better alternatives like R744 and HFO-1234YF.
According to some GWP Limit of 150 was announced because of the MAC lobbying to open the market for R152A.
R744 Refrigerant (CO2)
Modine is trying to develop a carbon dioxide based refrigerant system to reduce the greenhouse effect. It is one of the most popular alternatives as it has a warming potential of only one and it is readily available.
•Modine has contract from US Army and it has demonstrated its refrigerant in Army Humvee.
• Recently BMW has shown interest in their technology.
• German Automotive Association plans to switch to CO2.
Modine is claiming that there is a conspiracy to side line the CO2 based refrigerants. German Federal Environment Agency is supporting R744 (CO2 based) refrigerant after tests conducted by it found some safety issues with HFO-1234YF.
The downside of CO2 systems is that it requires more pressure to function properly and hence car makers have to make changes in the design to use CO2 as refrigerant.
It was developed in joint venture by Honeywell and Dupont to meet the new EPA standards. It is accepted by GM for 2013 release of Buick, GMC, Cadillac and Chevrolet. Its biggest advantages are listed below:
• It has warming potential of just four compared to 1400 of R134A
• It has atmospheric lifetime of just 11 days as compared to 13 years of R134A
• It is approved by EPA under its SNAP program.
• SAE tested it and found it superior to Carbon dioxide in performance and low in risk.
• The temperature pressure chart of HFO-1234yf and R134A are almost identical. So HFO-1234yf can be used in existing AC systems and its leak can be tested by existing R134A leak detectors.
At the moment the battle is between R744 and HFO-1234YF to become the R134a alternative in Car AC systems.
The refrigerant that replaces the R134A must meet the below points:
• It must have a GWP of less than 150 to meet the EPA standards. Lower the GWP and better the chances of gaining popularity as everyone is supportive of green refrigerants.
• Its pressure temperature chart should match the PT chart of R134A.A matching chart will ensure that there will be no changes in existing AC systems and help car manufacturers save a lot of money. It will also ensure that existing leak detectors can be used in new refrigerants case.
• It must not be Inflammable because it will need changes in existing AC systems to prevent fire.
• It must be as efficient in cooling as R134A because a costlier solution will not suit the masses.
• The ingredients used in the refrigerant must have any toxic effects on persons using it.
• Another point of concern is low atmospheric life. Leaked R134a has the atmospheric life of more than 10 years.