Your car's air conditioner might be your best friend on a hot summer day, but it is certainly no friend of the environment thanks to the ozone-depleting refrigerant used to keep the cockpit cool. This could change in a few years as carmakers in some parts of the world are being forced to charge their AC units with chemicals that have lower global warming potential.

General Motors Co. has put its considerable weight behind a new, and supposedly greener, AC refrigerant called HFO-1234yf, which is being developed by Honeywell and DuPont. The carmaker on July 23 announced it will use HFO-1234yf beginning in 2013 Chevrolet, Buick, GMC and Cadillac models in the U.S.

HFO-1234yf is designed to break down faster in the atmosphere than the R-134a refrigerant currently used. On average, R-134a has an atmospheric life of more than 13 years compared with 11 days for HFO-1234yf, according to GM. Put another way, R-134a has a global warming potential (GWP) of over 1,400 compared to HFO-1234yf's GWP of four. GWP is a value used to compare different greenhouse gases that trap heat in the atmosphere—carbon dioxide (CO2) serves as the base measurement with a GWP of one.

Automotive AC systems are prone to leakage due to the use of an open drive compressor and the need for flexible tubing to accommodate engine vibration. "There have been reports that indicate that older automotive AC systems leak up to 50 [percent] of their charge over two years," Eckhard Groll, a Purdue University mechanical engineering professor and director of the Office of Professional Practice, wrote in an e-mail to Scientific American. "Even if modern automotive AC systems are tighter most of them still leak at some rate." The U.S. alone has about 200 million cars with AC, and the typical amount of refrigerant used in each of those vehicles is about one kilogram.

HFO-1234yf is expected to help GM vehicles meet the overall requirements of the U.S. Environmental Protection Agency's new motor vehicle greenhouse gas regulations, which require a 40 percent improvement in the average overall vehicle fuel economy of the U.S. fleet by 2016, the company says. The European Union's mobile air-conditioning (MAC) directive requires that, starting in 2011, all new vehicle models use a refrigerant with a GWP below 150; by 2017, all new automobiles sold in Europe will be required to use a low-GWP refrigerant.

Automakers have another option—air-conditioning systems that use CO2. Members of the German Association of the Automotive Industry (VDA), spurred by a European Union mandate, jointly decided in the summer of 2007 to employ air-conditioning systems using CO2, rather than a fluorocarbon, as the refrigerant. If CO2 technology is adopted throughout Europe, manufacturers of fluorocarbon refrigerants will see the large MAC market significantly diminished, ICIS Chemical Business reported on its Web site in February 2008.

CO2 systems would require carmakers to modify their existing fluorocarbon-based AC systems. For one, a CO2-based system would require up to 10 times as much pressure as a fluorocarbon-based system to function properly. "Car makers would have to make major modifications to accommodate CO2 as a refrigerant, whereas HFO-1234yf can be used as a drop-in replacement refrigerant in existing AC systems," according to Groll. "I have seen presentations that show that the price of CO2 automotive AC systems will be 30 [percent] higher than that of R-134a systems."

Another challenge will be ensuring that any alternatives to R-134a do not make the situation worse. "My personal opinion is that with any synthetically manufactured substance there is some uncertainty about the long-term environmental impact," Groll says. "When the CFC refrigerants were developed in the 1930s they were celebrated as the best possible substances on Earth for this application. [Fifty] years later we found out that they deplete the ozone layer and lead to global warming."

5 Comments

1. 1. jmurphy8683 03:43 PM 8/11/10

   This article is misleading and should be revised for clarity. R134a is a hydrofluorocarbon meaning it is a chain of Hydrogen, carbon, and fluorine. It contains no chlorine and thus has a ozone depletion potential OZP = zero. R134a replaced R12 (a hydrochlorofluorocarbon) because of R12's high potention to be ozone depleting. This article states that your air-conditioner is, "no friend of the environment thanks to the ozone-depleting refrigerant used". This is not the case unless you have a very old system that still uses R12 and hasn't been converted. R134a does have a high GWP as stated in the article and this is why it is being replaced. The statement in the first paragraph is not accurate. CO2 doesn't seem like the best solution. 10 times as much pressure means the compressor is going to consume more energy making your car burn even more gasoline.

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2. 2. greencooling 09:52 AM 8/12/10

   I strongly agree with the above comment, there is quite enough public confusion about the difference between ozone depletion and global warming without SciAm.com adding to it!
   
   However, while it's great news that anything is being done to reduce HFC emissions, it's worth noting that hydrocarbon refrigerants (blends of propane R290 and isobutane R600a) are in very wide use in North America, and are a readily available solution for servicing existing systems. They are safely and reliably used in many countries worldwide, and addressing the current lack of regulatory approval of HCs in the USA could make a vastly greater reduction in emissions than many years of new production of low GWP AC vehicles.
   
   The science on the environmental acceptability of HFOs is far from certain, and many serious questions of concern are waiting to be answered (watch out for the report of the Scientific Assessment Panel of the Montreal Protocol in early 2011&). A short atmospheric lifetime may well produce a low GWP figure, but the big questions are where does that significant amount of fluorine go once weve dumped it into the atmosphere, what decomposition by-products will be formed, and what ecological impacts are they likely to have?
   
   We should be very cautious about endorsing a new fluoro-chemical when natural refrigerant solutions such as hydrocarbons and CO2 are available and highly efficient.
   Hydrocarbons have significant cost advantages, and over nearly two decades have been proven to be safe, efficient and environmentally acceptable solutions to the very Global Warming Potential HFC problem, perhaps it is time for a re-evaulation?
   
   Even if it takes another 15 years for the OEMs to accept this and provide new vehicles with very efficient purpose built small charge HC systems, for at least existing HFC or CFC systems in the service market, hydrocarbon refrigerants provide a high performance, reliable, cheaper and safe solution right now. Experience shows HCs work well, are easy for trained technicians to handle, and do not result in more frequent fires or accidents.
   
   Hydrocarbons also have great potential in domestic and commercial air conditioning applications, and as well, CO2 and ammonia are suitable in many other sectors. We simply do not need HFCs, but we do need change.
   
   It is well past time for consumers, industry and policy-making stakeholders to recognise the fluorolobby fearmongering around HCs for what it is, and to demand this practical green solution be made available.

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3. 3. greencooling in reply to greencooling 09:57 AM 8/12/10

   PS - readers interested in exploring this topic further may well find a visit to beyondhfcs.org of interest!

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4. 4. SabLoe 01:46 PM 8/13/10

   HFO is not a simple drop-in solution for existing car A/C units!
   
   Yes, this has been the initial marketing argument by the Honeywell/DuPont but meanwhile it is openly discussed in expert circles that system modifications will be necessary for the use of HFO as well. This is due as well to the high flammability of HFO as well as to mechanical difficulties.
   
   So HFO will not at all be less expansive than CO2 systems. Quite on the contrary! Honeywell/DuPont hold already the patents in all major markets for this new refrigerant - meaning they will have the monopole and can dictate the price. Furthermore, a supply shortage is expected in 2011, the first year that international legislation obliges OEMs to use a low GWP refrigerant.
   
   CO2 on the other hand is freely and cheaply available as it can be recycled from industry emissions. So even if the up-front cost is a bit higher than for a HFO system, the cost would amortise rapidly.
   
   Basically, there is no rational argument left to defend the use of HFO. It is NOT environmentally friendly, it is NOT safe, it is NOT cheaper than CO2.
   
   How can anyone justify its use?

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5. 5. rddash 03:55 PM 8/18/10

   What ever happened to Rovac? It didn't need any HFCs.

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