The study by automotive engineering association SAE International examined the mobile air conditioning HFO refrigerant R-1234yf, or HFO-1234yf. SAE initiated the evaluation in response to safety concerns raised by Daimler last fall. In September 2012, Daimler announced it would stop using the refrigerant and said in some head-on collision test scenarios, HFO-1234yf burst into flames.
The SAE study calls Daimler’s testing that raised questions about the refrigerant’s flammability “unrealistic” and says all 11 global automakers that participated in the project agree with its conclusions. The participating car companies include Chrysler, Fiat, Ford, General Motors, Honda, Hyundai, Jaguar Land Rover, Mazda, PSA, Renault and Toyota.
The testing “created extreme conditions that favored ignition” and ignored mitigating factors that would exist in an actual car crash, the study says. SAE concluded it was 20,000 times more likely for a person to die in a plane crash than be exposed to a vehicle fire caused by a leak and ignition of HFO-1234yf. It also said it was 300,000 times more likely a vehicle would experience a fire for any reason and 100,000 times more likely for an accident to happen because of a brake failure.
Ken Gayer, vice president and general manager for Honeywell Fluorine Products, said the SAE study “leaves no doubt” that HFO-1234yf is safe for use in vehicles.
Honeywell and DuPont developed HFO-1234yf as an alternative to HFC-134a, also known as R134a, which is being phased out in the European Union and will be banned in 2017. HFO-1234yf has a GWP (Global Warming Potential) of 4 and reduces global warming impact by 99.7 percent compared with HFC-134a.
According to the EPA, HFC-134a does not deplete the ozone layer, but has a GWP that is approximately 1,400 times greater than that of CO2.
In March, Volkswagen, Daimler, Audi, BMW and Porsche announced plans to develop CO2 technology as a more climate-friendly refrigerant for air conditioning systems. At the time, German media sources reported Daimler, Audi, BMW and Porsche also planned to switch to CO2 technology in mobile air conditioning systems as an alternative to HFO-1234yf.
VW says CO2 as a refrigerant — also known as R744 — has lower greenhouse gas effects than conventional refrigerants, with a GWP value of 1, or 99.3 percent below the EU-specified GWP limit of 150. The German automaker says the technology will be rolled out progressively over its entire vehicle fleet.