I keep on reading about a new refrigerant, R-1234yf, that is being adopted by some automotive manufacturers.
What is this refrigerant all about, why are manufacturers considering it and what makes it different from R-134a?
R-1234yf is designed to be an environmentally-friendlier, near drop-in replacement for R-134a.
Environmental legislations are pushing for refrigerants with lower global warming potential (GWP). R-1234yf is an attempt to address that, with a GWP that is over 300 times lower than R-134a:
HFO-1234yf was developed to meet the European directive 2006/40/EC that went into effect in 2011 requiring that all new car platforms for sale in Europe use a refrigerant in its AC system with a GWP below 150.
Unsurprisingly, quite a few major manufacturers have committed to using it:
General Motors still plans to transition all new models to the new refrigerant by 2018. Chrysler announced that they would continue the transition to R1234yf as well. Japanese automakers are also making the transition to R1234yf, Honda and Subaru have begun to introduce the new refrigerant already with the 2017 models.
One of the things that makes R-1234yf an appealing option to manufacturers is that switching to it from R-134a doesn't require significant retooling of manufacturing facilities.
Something similar can be argued for the automotive repair industry:
The product could be handled in repair shops in the same way as R-134a, although it would require different, specialized equipment to perform the service. One of the reasons for that is the mild flammability of HFO-1234yf. Another issue affecting the compatibility between HFO-1234yf and R-134a-based systems is the choice of lubricating oil. The current lubricating oil is showing signs of damage to plastic and aluminium, and issues with health, including mouth dryness, rashes, and sore throat, among other effects.
Some concerns have been raised over the flammability of R-1234yf, though there are additive-based workarounds being suggested by the industry.
Mixing HFO-1234yf with 10-11% R-134A is in development to produce a hybrid gas under review by ASHRAE for classification as A2L which is described as "virtually non-flammable". These gasses are under review with the names of R451A and R451B. These mixes have GWP of ~147.
Other additives have been proposed for lowering the flammability of HFO-1234yf, such as trifluoroiodomethane, which has a low GWP due to its short atmospheric lifetime, but is slightly mutagenic.