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Future Alternative Refrigerants
What the future holds for automotive refrigerants is uncertain, but changes are coming. At some point down the road, R-134a refrigerant will likely be replaced by one or more alternative refrigerants. The question now is which one?
The Europeans want to phase out R-134a in new vehicles by 2017. The European rules require any new refrigerants must have a global warming potential of less than 150. The U.S. EPA also wants car makers to switch to a different refrigerant to lower the overall carbon emissions of the vehicle fleet. Carbon credits will be given to auto makers who make the switch to a refrigerant that has a lower Global Warming Potential (GWP).
Though R-134a poses no danger to the ozone layer if it escapes into the atmosphere, it is a "greenhouse gas" with a fairly high global warming potential of 1300 (compared to 1 for carbon dioxide, which is nature's own greenhouse gas). A leak that allows only an ounce or two of R-134a to escape into the atmosphere may not seem like a big deal, but over time it all adds up, especially when you multiply small leaks times the hundreds of millions of vehicles that now share planet Earth with humanity.
According to November 2006 report by the Energy Information Administration, vehicles in the U.S. leaked 50.8 thousand tons of R-134a into the atmosphere, equivalent to to over 66 million tons of greenhouse gases. The emissions are 7% higher than in 2004, and up 273 percent since 1995.
As of 2008, the North American and Japanese auto markers had not yet decided to replace R-134a with any other refrigerant. But the auto makers have redesigned their A/C systems with the following goals in mind:
* To use less refrigerant. Some newer A/C systems now use only 12 to 14 oz. of refrigerant, which is much less than the 24 to 60 oz. charges that most older A/C systems use. As time goes on, we will see more and more of these low capacity A/C systems in new vehicles.
* To reduce refrigerant leakage 50% over the life of the vehicle. This requires using improved seal designs, hoses and o-ring connections.
* To improve cooling efficiency 30% with more efficient condensers, compressors and operating strategies (things like variable displacement compressors that run all the time rather than cycle on and off). Mercedes has this now.
* To reduce the cooling requirements inside the passenger compartment 30% by using reflective coatings on glass, heat reflective paint, and venting the interior during hot weather.
Changes are also being made to reduce refrigerant losses when the A/C system on a vehicle is serviced. The latest generation of refrigerant recovery machines do a better job of removing all of the refrigerant from the system. Older machines can leave as much as 20 to 30 percent of the old refrigerant charge in the system. The residual refrigerant can escape into the atmosphere when the A/C system is opened to replace parts. Some of the newest machines can pull up to 95% of the refrigerant out of the system to reduce the amount of R-134a that escapes into the atmosphere.
Auto makers have also been adding leak detection dye to the refrigerant to make it easier for technicians to detect refrigerant leaks. A leak will leave a telltale stain that glows greenish-yellow or greenish-blue when illuminated with an UV light source. Leaks as small as 1/8 oz. of refrigerant per year can be detected this way.
The Europeans auto makers are taking a different approach. They want future A/C systems to be as environmentally benign as possible. That means no chlorine-containing CFCs such as R-12 or R-22 that cause ozone depletion, an no refrigerants that could add to the global warming problem (which includes R-134a). Any new refrigerants must also be nontoxic and safe, though that doesn't necessarily mean nonflammable.
For more information, see Flammable Refrigerants
In an effort to address these issues, the Alliance for Responsible Atmospheric Policy (ARAP) and the U.S. Environmental Protection Agency (EPA) have held a series of annual meetings to discuss and evaluate alternatives to R-134a. The first of these meetings was held in 2003 by the European Commission in Brussels. As a result of that meeting, the European Commission decided to allow carbon dioxide, HFC-152a and other refrigerants as possible replacements for R-134a.
CO2 as an Alternative Refrigerant?
When used as a refrigerant, CO2 (called R-744) requires extremely high operating pressures (up to 1,800 psi on the high side, and 350 to 400 psi on the low side), compared to 300 to 400 psi on the high side for R-134a. The reason the pressures are so high is because CO2 does not condense in the refrigeration circuit. It remains in the gaseous state. Consequently, the front heat exchanger is called a "cooler" rather than a condenser.
CO2's main attribute is that it has virtually no impact on global warming or ozone depletion. CO2 is also nontoxic in small doses but concentrations over 5% can be lethal. It is also cheap (about $10 for a 20-lb. cylinder) and nonflammable. Numerous test vehicles with CO2 A/C systems have shown that CO2 does provide cooling performance comparable to R-134a.
SAE has developed service fitting standards for R-744. Leak detection presents a challenge because natural levels of CO2 in the atmosphere may be higher than the amount emitted by a leak from an A/C system. Some type of ultrasound or infrared equipment may be required to find R-744 leaks, but dyes may also work or plain old soap bubbles.
HFC-152a is almost a straight drop-in substitute for R-134a. The molecule is similar to R-134a except that two hydrogen atoms are substituted for two fluorine atoms. It has similar operating characteristics to R-134a but cools even better. One test in an otherwise unmodified Saturn Ion found that A/C duct outlet temperatures were several degrees C lower with HFC-152a. Fuel efficiency was also up 10% at idle, and 20% at highway speeds. The system typically requires only about two-thirds of the normal charge with HFC-152a and can be used with current desiccants.
An environmental benefit of HFC-152a is that it has a global warming rating of 120, which is 10 times less than R-134a, but still a lot higher than CO2. That is why HFC-152a is currently used in many aerosol products as a propellant. Its main drawback is that it is slightly flammable (Class 2A), but it is not as flammable as propane or most other hydrocarbon-based refrigerants.
The first mobile A/C system to use HFC-152a was unveiled at the Mobile Air Conditioning Society (MACS) Worldwide tradeshow in January 2004; a self-contained unit for off-road construction equipment that featured an oil-driven compressor. Made by Red Dot, the unit may be the forerunner of future HFC-152a A/C systems to come.
Red Dot staff explained that the HFC-152a refrigerant used in the self-contained unit improves cooling capacity, decreases fuel use and helps protect the climate. The new technology also satisfies stringent new regulations proposed by the European Commission. Red Dot staff also said that the HFC-152a system uses new technology that will use hydraulic-driven compressors and secondary loop technology to increase reliability, safety and reduce the amount of refrigerant required.
The refrigerant that may eventually replace R-134a is HFO-1234yf. Developed jointly by Honeywell and DuPont, it is being promoted as a drop-in replacement for R-134a in both new vehicles and older vehicles, should that become necessary in the future. HFO-1234yf has thermal characteristics that are very similar to R-134a, so no major modifications to the A/C system are necessary. Better yet, HFO-1234yf has a global warming potential of only 4, compared to 1200 for R-134a, allowing it to meet the European requirements for a GWP of less than 150. Existing refrigerant leak detectors can also detect HFO-1234yf if it leaks. But HFO-1234yf is mildly flammable (though less so than HFC-152a), and the industry is still debating its potential safety.
Currently, there are NO plans to make HFO-1234yf directly available to consumers or do-it-yourselfers (meaning you can't recharge your A/C system yourself if this new refrigerant is accepted for wide scale use in new vehicles). Also, repair shops can only buy the new refrigerant in 10-pound containers, limiting the amount they can keep on hand for service work.
As of early 2013, production of the new refrigerant has also been very limited, so it may be some time yet before production can be remped up to meet the expected demand if auto makers opt to make the switch from R-134a to R-1234yf.
Click Here for a DuPont brochure on HFO-1234yf.
Update: November 2008
SAE Says HFO-1234yf is Best Alternative Refrigerant for R-134a
In a recent press release, the Society of Automotive Engineers (SAE) International Cooperative Research Program (CRP) says HFO-1234yf offers "superior environmental performance" for future mobile air conditioning systems that may be redesigned for alternative refrigerants.
The CRP1234-1 and CRP1234-2 programs, launched in 2007, have investigated the safety and performance of the new refrigerant HFO-1234yf. Under the direction of the SAE CRP members (who are international experts in this field from OEMs, Tier 1 and 2 Suppliers and independent test facilities), air conditioning system performance, material compatibility and relative risks of HFO-1234yf were evaluated. Based on these studies, HFO-1234yf was judged to have the lowest risk for use in mobile A/C systems compared to all of the other alternative refrigerants that are currently being evaluated. This is based on the Life Cycle Climate Protection analysis that estimates CO2 Equivalent emissions from automotive A/C usage (as described in SAE J2766).
Click Here to view the SAE CRP1234 report on HFO-1234yf.
The study was conducted in response to European Union regulations that will require all new vehicles made for model year 2011 and later to use a refrigerant with a Global Warming Potential (GWP) below 150. Current automotive A/C systems all use R-134a, which has a GWP of 1,430. HFO-1234yf has a GWP of only four.
Update: October 15, 2009
EPA to Approve HFO-1234yf Refrigerant for Significant New Alternatives Policy (SNAP) program
On Tuesday, October 13, 2009, EPA's Administrator signed a rule proposal that says HFO-1234yf is an acceptable substitute for CFC-12 in motor vehicle air conditioning, subject to use conditions. You can view the proposed rule on EPA's SNAP website at http://www.epa.gov/ozone/snap/.
The public comment period on this proposed rule is for 60 days, beginning when it is published in the Federal Register early next week. Once the rule is published, you will be able to find information and to send EPA comments on the proposed rule at http://www.regulations.gov/ , docket EPA-HQ-OAR-2008-0664. The Federal Register version of the proposed rule will be posted by the end of the week of October 19 at http://www.epa.gov/ozone/snap/regulations.html (Rule 16 on HFO-1234yf).
Update: September, 2010
GM to Use HFO-1234yf Refrigerant in some 2013 Models
GM says that starting in 2013, it will begin using HFO-1234yf refrigerant instead of R134a in the air conditioning systems in some Cadillac models (XTS luxury sedan and ATS sports sedan). This will help GM meet the new greenhouse gas emission rules. The Chevy Volt plug-in hybrid electric, however, will have an R134a air conditioning system (for now).
Update: October 21, 2010
SAE Releases 20 New Standards for HFO-1234yf Refrigerant
The Society of Automotive Engineers (SAE) has announced 20 new standards covering service procedures, service equipment and vehicle components for the new HFO-12354yf refrigerant. The standards require auto repair shops to buy all new equipment to service the A/C systems on new vehicles that are equipped with HFO-1234yf. The new equipment requirements are covered in J2911, which includes a provision that the recharging machine must test the A/C system for leaks. If a leak is found, the machine will not recharge the vehicle until the leak is fixed. J2843 covers recovery procedures.
J2845 will require technicians who work on HFO-1234yf systems to be certified in service and recovery procedures.
There is also a new standard J2842 that prohibits shops from repairing leaky evaporators, or fixing a vehicle with a used evaporator from a salvage vehicle because of possible safety risks. HFO-1234yf is mildly flammable, so the reason for replacing a leaky evaporator with a new one is to minimize the risk of a repeat leak that might allow the refrigerant to enter the passenger compartment.
Currently, there is no mandate in the U.S. to phase-in HFO-1234yf by a certain date, so the phase in will be gradual and will likely be spread across many model years as new vehicle models are introduced. This will likely create a LOT of confusion in the years ahead as to which type of refrigerant to use in a particular model year vehicle. R134a or other refrigerants must NOT be intermixed with or substituted for HFO-12354yf in new vehicles if service is required as damage may result to the A/C system due to different operating pressures.
New vehicles with HFO-1234yf A/C systems will also require a unique type of PAG compressor oil. Compressors for these systems are being redesigned to keep more of the oil in the compressor to improve cooling efficiency. Larger, more efficient condensers are also required because HFO-1234yf cools about 10 percent less efficiently than R134a.
Update: September 4, 2012
MACS Announces HFO R-1234yf Technician Training Program
The Mobile Air Conditioning Society (MACS) now has a new training program to certify automotive technicians to SAE J2845 under the SAE J2911 program for the upcoming introduction of HFO R-1234yf refrigerants in new vehicles.
SAE International created the J2911 and J2845 standards in response to changes in the refrigerants that will be used in mobile A/C systems. The SAE J2845 standard covers servicing of (HFO) R-1234yf and R-744 mobile air conditioning (MAC) systems. The training teaches technicians how to identify which refrigerant is in a vehicle, how to handle it safely, and what type of service information, tools and equipment are needed to service the vehicle.
Update: November 2012
Mercedes, BMW and VW say they will NOT use HFO-1234yf Refrigerant because of Safety Concerns
Citing concerns that the alternative refrigerant HFO-1234yf can burn in real life conditions inside a vehicle (per lab simulation test results), Mercedes, BMW and Volkswagen said they will NOT switch their vehicles to HFO-1234yf. At this time, it appears that CO2 may be the best alternative to R-134a, according to the German auto makers.
HFO-1234yf can by ignited by a spark within seconds of its release, and emits highly toxic fumes and acids as it burns according to tests conducted by Daimler. CO2 is nonflammable and is carbon neutral, so it appears for now that HFO-1234yf is on hold as far as two of the leading German auto makers are concerned.
On a related note, Cadillac has temporarily suspended installing HFO-1234yf in the ATS sports sedan and XTS luxury sedan. For now, these vehicles will be produced with R-134a pending further investigation into the potential flammability issues with HFO-1234yf.
Update: April 13, 2013
Latest Alternative Refrigerant May be a Blend Called AC-6
To counter the virtual monopoly that Honeywell and DuPont have on the production of HFO-1234yf refrigerant (which is currently selling to car dealers for around $60 to $70 a pound!), Mexichem has developed a blended refrigerant that could sell for as little as $10 a pound, and would work in any R-134a A/C system. The AC-6 blend contains 85 percent R-1234ze, 9 percent R-134a and 6 percent CO2. The Global Warming Potential (GWP) of the new blend is 6.0, which is well under the GPW requirement of 150.
For AC-6 to be approved, the auto makers would have to do extensive testing, and the EPA would have to add it to its approved alternative refrigerant list.
The main drawback of a blended refrigerant is that some of the ingredients in the mix tend to leak out of an A/C system faster than others, effectively changing the blend over time and its thermal characteristics. Currently, there is no aftermarket A/C service equipment that can reconstitute a blended refrigerant. If an A/C system charged with AC-6 required service, the old refrigerant would have to be recovered from the system and replaced with new refrigerant rather than recycled.
More Refrigerant Articles:
Alternative Refrigerants for R-12
California proposes ban on R134a sales to motorists
Information about Retrofitting older vehicles with R-12 A/C systems to R-134a
Troubleshooting Air Conditioning Problems
How To Recharge Your Car's Air Conditioner
Click Here to See More Carley Automotive Technical Articles
Alliance for Responsible Atmospheric Policy (ARAP)
EPA FAQs on Alternative Refrigerants
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