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:
|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).