Simanaitis Says
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A GLOSSARY OF COOL
CHANGES ARE coming in the refrigerant used in automotive air conditioning, so it seems a good time to bring things up to date with a Glossary of Cool. Also, it’s the 25th anniversary of the Montreal Protocol on Substances that Deplete the Ozone Layer, the international understanding that started all this.
Pre Montreal Protocol: R-12, trade name DuPont Freon, was the refrigerant of choice in automotive a/c systems. It was highly effective in its transitions from gas to liquid and back over different pressures and temperatures. R-12 was also reasonably inexpensive.
Alas, R-12 is a CFC, a chlorofluorocarbon. And there is robust science that CFCs were depleting the ozone layer, our stratospheric protection against cancer-inducing ultraviolet radiation. The Montreal Protocol, signed and effective by 1989, set a 1992-1994 phase-out period for automotive use of R-12.
On modern cars, we take these vents utterly for granted. The type of refrigerant lurking behind them has changed, though.
R-134a: Freon’s substitute, in most cars on the road today, is R-134a. It’s not a direct drop-in replacement of R-12, though. The two require different lubricants in the a/c system, run at different optimal pressures—and R-134a isn’t quite as good a refrigerant as R-12. To get the same cooling from an R-134a system, there is likely an upsizing of components at the design stage.
Most important, R-134a doesn’t harm the ozone layer. And, indeed, scientists reckon that with CFC use diminished around the world, the ozone layer is rejuvenating itself.
This wonderful illustration by Jack Unruh initially appeared in “Tech Update: Keeping Kewl,” in Road & Track, June 2011.
A climate change digression: Climate has been identified as changing (as though anyone would have expected it to be utterly constant), and scientific evidence points to fossil fuels’ contribution of CO2 as having a detrimental effect in this.
I disagree with those who say “the science is over.” Science is never over. With something as complex as climate studies, science is a process, not simply a collection of musty old facts.
CO2: Yet, it happens that CO2 levels are reaching historic highs, and there are models suggesting this is not a beneficial thing. The mechanisms may not be as clear as CFCs harming the ozone layer, but there is a point to be made: If CO2’s effect on the atmosphere is bad—if, mind—then the effect of R-134a is dramatically worse.
That is, today, refrigerants are categorized by their Global Warming Potential, with CO2 assigned the GWP value of 1. On this proportional scale, R-134a has a GWP of 1430.
European regulators were first to demand a phase-out of R-134a, with the requirement that its replacement’s GWP be no greater than 150.
R-744: For a while there, European automakers were exploring CO2 itself, code named R-744, as an automotive refrigerant. However, R-744 is not cheap, not a very good refrigerant, and its operating pressures are 10 times that of R-134a systems.
HFO-1234yf: Instead DuPont and Honeywell have jointly developed another choice, HFO-1234yf. Thankfully known as “twelve-thirty-four,” this refrigerant is a near drop-in with existing R-134a designs—and its GWP is 4. No wonder EPA includes its use in the credit column of future Corporate Average Fuel Economy calculations.
There’s good news as well in 1234’s “atmospheric lifetime.” Whereas R-134a takes more than 13 years to break down—and R-744, more than 100 years—1234’s atmospheric life is only 11 days.
Two new Cadillacs, the XTS shown here and the ATS, are the first to use the new refrigerant. Others will have it phased in through Model Year 2016.
Alas, 1234 is significantly more expensive than R-134a. Right now, it’s in relatively short supply. And a/c shops servicing cars using it need new equipment and training.
Environmental improvements are never particularly simple. ds
Simanaitis Says 
My first car, a truck actually, had manual vents. To open a portal straight to the outside air, you pulled a lever with a ball on the end. I used to say it had 50/50 A/C — drive 50 mph with the windows halfway down. (Not that the truck would go 50 without a tailwind.) Maybe we are headed back this way!
Aha. A difference between Bakersfield and Cleveland. There, it was 440 a/c: four windows down all the way, but only 40 mph. I think it was more muggy too.