New refrigerant as cool as R-134 but safer if released

So why is GM switching from R-134 to HFO-1234yf?  The new refrigerant provides lower “global warming potential” (GWP), which is to say it is better for the environment.  It cools as well or better than R-134.

Current automotive air conditioners use hydrofluorocarbon HFC-134a, which has a GWP of 1430. The European Union’s Mobile Air Conditioning Directive requires that, starting in 2011, all new vehicle models use a refrigerant with a GWP below 150, and by 2017, all new automobiles sold in Europe will be required to use a low-GWP refrigerant. The new refrigerant, developed by DuPont and Honeywell, has a GWP of 4, which is 97% less GWP than the new regulation requires.

Remember the old R-12?  It had a GWP of 8100.  So yes, R-134 was better than R-12, but HFO-1234yf is a large improvement over both.

The other alternative was CO2 (R744); here is a comparison of HFO-1234yf and R744:

HFO-1234yf: the better choice
HFO-1234yf CO2 (R744)
Environmental Impact Lower lifetime GHG emissions than 134a or CO2 20% more lifetime greenhouse gas emissions than 1234yf
Atmospheric Lifetime 11 days >500 years
Compatibility with Current A/C Equipment Yes, with minor change No; new high-pressure system required
Cooling Efficiency Comparable to 134a in all climates Less efficient in hot climates where A/C is needed and used most
Ease of Adoption High; minimal additional design changes or delay Low; significant engineering and re-tooling required
Safety Safe for use in automotive air conditioning applications Safe for use in automotive air conditioning applications

So it looks like HFO-1234yf is a good choice going forward.  A concern has been the relatively high cost of the new refrigerant, but with widespread usage and new factories online that should resolve itself (supply and demand).

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