Society of Automotive Engineers' Final Report Backs Climate-Friendly Coolant While German Car Makers Flout European Rules

Updating earlier work, an expert panel of automotive engineers issued its final report on June 21st reaffirming the safety of the new climate-friendly coolant for car air conditioners called HFO-1234yf.  In December the panel of engineers from eleven auto manufacturers, convened by SAE International (formerly the Society of Automotive Engineers), rejected fire risk claims leveled by Daimler (the maker of Mercedes-Benz), calling Daimler’s tests “unrealistic” and “highly improbable.” 

The new coolant is coming into use to meet European, American, and Japanese climate-protection requirements to replace the current coolant, HFC-134a (R-134a), which is a potent greenhouse gas. The new coolant has 1/350th the heat-trapping punch of the current one.  That means one day of producing cars with HFC-134a has the same damaging impact on the climate as a year of car production with HFO-1234yf. 

Now the SAE panel has put numbers to its adjectives.  It found that the risk of a fire related to the new refrigerant, conservatively estimated, is nearly a million times lower than the auto fire risks from all other causes.  And those risks are already quite low.  According to the panel, the risk of an auto fire from any cause is about one-in-a-million per hour of operation.  It puts the fire risk from HFO-1234yf (also known as R1234yf) at three-in-a-trillion – almost a million times less

The panel found this “well below risks that are commonly viewed as acceptable by the general public,” for example, 10,000 times less than the risk of dying in a commercial plane crash.

Last fall, after initially agreeing that the new coolant was safe to use, Daimler abruptly changed course, claiming that new tests showed a fire hazard.  As described here, Daimler conducted simulations (not actual crash tests) under contrived and extreme conditionsThe SAE panel found “the refrigerant release testing completed by Daimler was unrealistic by creating the extremely idealized conditions for ignition while ignoring actual real world collision scenarios.”   The panel found that “these conditions include specific combinations of temperature, amount and distribution of refrigerant, along with velocity, turbulence, and atomization, which are highly improbable to simultaneously occur in real-world collisions.” 

In assessing Daimler’s tests, the SAE panel examined actual crash tests by other car makers.  It also expanded on previously conducted “fault tree” analyses by considering new potential accident scenarios involving fires in the engine compartment:  “the possibility of an individual being unable to exit the vehicle due to a collision or a non-collision event that involves a refrigerant/oil release, the refrigerant/oil being ignited and the fire propagating.”  The panel estimated passengers’ fire risk at three-in-a trillion.  It also estimated passengers’ risk of being exposed to dangerous levels of hydrogen fluoride, a toxic combustion byproduct, at five-in-a-trillion.

Ten companies participated in the SAE panel from start to finish and endorsed its conclusions:  Chrysler/Fiat, Ford, General Motors, Honda, Hyundai, Jaguar Land Rover, Mazda, PSA, Renault and Toyota.  Daimler (together with BMW, Volkswagen, and Audi) dropped out when the panel’s conclusions did not go their way.   

Daimler’s motives in this whole affair remain a big puzzle.  Just one week before issuing its surprise safety claims in September, the company had joined all other German auto makers (including BMW, Audi, and VW) in publicly pronouncing R1234yf safe and environmentally acceptable.  Daimler apparently gave no hint of its impending flip-flop to its peers.  Daimler resisted formation of the SAE panel to evaluate its claims – a standard auto industry procedure – and later walked away. 

Daimler is now thumbing its nose at European regulations prohibiting the use of HFC-134a in “new type” models (models that have undergone substantial redesigns).  Daimler has sold some 47,000 cars in Germany with HFC-134a since the start of the year in violation of these requirements.  Despite having already registered some of these models as “new type,” and despite the fact that they are plainly major redesigns, Daimler and some other companies are now claiming they just old models covered under old registrations.  Germany’s auto regulatory agency is said to have “warned” the companies, but has taken no definitive action to stop them.  (These abuses are not possible in the United States, for example, where standards apply to “model years” that start and end on defined dates, and where each car’s model year depends simply on the date it was produced.)

Daimler, assisted by the German government, continues to lobby the European Commission to retroactively delay the regulations so that the company can keep using HFC-134a indefinitely while it works on developing CO2-based air conditioners.  Successfully commercializing cost-effective and energy-efficient CO2 systems for cars appears to be years away, however.

The European Commission, to its credit, has resisted Daimler’s and Germany’s pressure and standing by its requirements.  The Commission is reported to be preparing “infringement” proceedings.  These will take a long time, however, since the Commission cannot enforce directly against companies but must first take action against Germany.  And Germany is sitting on its hands.

NRDC is technology-neutral:  We’ll support any safe and effective technology to replace the potent heat-trapping HFCs as rapidly as possible.  In HFO-1234yf we have a bird in the hand that is 350 times less damaging than the current coolant, and we should use it now even while some companies continue working on CO2 systems. 

Delay has its costs.  As already noted, each day of producing cars with the current coolant, HFC-134a, has the same heat-trapping impact on the climate as a full year of production with HFO-1234yf. 

Armed with the SAE’s firm conclusions, American, Asian, and other European car makers are expected to stay the course and complete their transition to HFO-1234yf.  These companies are confident they have safely engineered their systems to render any flammability risks insignificant, for example, by keeping refrigerant lines away from hot surfaces. 

The European Commission must stand its ground and vigorously enforce its rules.  And Germany must stop acting like a fixer for Daimler.  Germany needs to demonstrate its commitment to climate protection by holding Daimler and other companies to the rules.  And then let’s see what German engineering can do.