In the 1990’s automotive air conditioning systems started switching over from CFC R-12 dichlorodifluoromethane to HFC R-134a tetrafluoroethane, which has significantly less of an ozone-depletion potential. Still, R-134a has a significant global warming potential (GWP), measuring 1,300 on the scale, which has prompted regulators to move for its discontinuation. New mandates specify that new vehicle air conditioning systems must use refrigerants with a GWP lower than 150. In 2013, the use of a synthetic R-123a was mandated, and then HFO-1234yf tetrafluoropropene, which only has a GWP of 4, was approved and mandated for use in automotive air conditioning systems by 2017.
While laudable as a climate-conscious replacement for HFC R0134a, at least one automaker was absolutely shocked to discover that HFO-1234yf was extremely flammable, resulting in the release of both toxic and corrosive gases. As a result, Mercedes-Benz, BMW, and Volkswagen-Audi wholly rejected the use of HFO-1234yf refrigerant, focusing instead on liquid carbon dioxide, also known as R-744, as a refrigerant.
Mercedes-Benz will be the first to release vehicles with the new air conditioning systems, using liquid carbon dioxide as a refrigerant. Regarding GWP, liquid carbon dioxide is essentially the baseline, with a GWP of 1. Additionally, it is non-flammable, non-corrosive, and non-toxic, which makes it an ideal solution for automotive air conditioning applications.
The first cars to get the new liquid carbon dioxide air conditioning system will be the 2016 Mercedes-Benz E-Class and S-Class. Later, Mercedes-Benz will extend the application to the A-, B-, and C-Class. Still, to comply with current regulations, the company says that it has made serious modifications to adapt to HFO-1243yf. Time will tell if the EU will continue to mandate the flammable-toxic-corrosive refrigerant, or if it will bend and allow the use of the new liquid carbon dioxide system.