Air conditioning debate heats up for Mercedes

Mercedes crash testing indicates new air conditioning refrigerant gas could ignite, releasing toxic and corrosive gases
CC BY 2.0 A200/A77Wells

Air conditioning relies on coolant fluids that can be compressed and then expand rapidly, which is the source of the desired cooling effect. Unfortunately for all of us seeking respite from ever more frequent record-setting heat, the coolants can have terrible effects on our environment.

A Short History of Cooling

The original engineered refrigerants, chlorofluorocarbons (CFCs), were banned when it was discovered that emissions of the CFCs damage the ozone layer that protects our planet from the sun's rays. When these were banned, chemical companies filled the gap with Fluorocarbon refrigerants. As you might guess from the names, the earlier substances had a mixture of chlorine and fluorine on a hydrocarbon backbone. The newer substances have eliminated the chlorine and use only fluorine, which has gone a good way to rescue the ozone layer.

But now when engineers think of coolants, they think global warming. While most of the public associates carbon dioxide (CO2) with climate change, other substances have more greenhouse effect than CO2. So although much more CO2 is released by fossil fuel burning, smaller amounts of these high-greenhouse effect chemicals can cause equal damage.

The measurement of the strength of a chemical's greenhouse effect is known as GWP -- global warming potential. CO2 serves as the standard, with GWP = 1.

  • The old CFCs had GWPs thousands of times higher than the ill-reputed CO2: R-12 has a GWP of 8500 and R-11's GWP is 4000.
  • The CFC replacement Fluorocarbon refrigerant R-134 dropped to a GWP of 1440.
  • Enter R-1234yf. This refrigerant has a GWP of 4, and breaks down in the atmosphere in less than a week.

Because of its high GWP, governments are acting to ban R-134. While many favor CO2 itself as a replacement, the use of CO2 in cooling systems would require entirely re-engineering the automotive systems. R1234yf can be used in the same systems that use R-134, making it a preferred alternative for the automotive companies.

Mercedes Dilemma

Mercedes parent Daimler claims R-1234yf is too dangerous. It has shown in lab tests that a small amount of butane (see correction note below), present as an impurity in the otherwise inert refrigerant gas, can catch fire if it leaks in a crash. Once involved in a fire, the R-1234yf breaks down, releasing hydrofluoric acid -- which is toxic and highly corrosive.

In spite of European laws requiring Mercedes models built after June 2013 to use the new refrigerant, Daimler has refused. Unfortunately, it seems that they are alone in the moral sanctity of this decision.

No other automotive manufacturer has seen this type of ignition event in crash tests. R-1234yf manufacturer, Honeywell, says that a minor redesign of Mercedes air conditioning system would solve the problem. Germany has granted Mercedes an exemption from the EU law, igniting their own toxic, corrosive debate about the issue.

Daimler, Audi, BMW, Porsche and VW have stated publicly their intention to develop CO2-based air conditioning. But that will take time. So now the questions remain: Will Daimler step in line under public and political pressure, possibly putting drivers at risk? Will a settlement allow Daimler to pay into a compensation fund for using the old climate-killer refrigerant until they can find a solution they approve -- as has been proposed to resolve issue. And when will this heat wave end?

Correction: Honeywell has informed TreeHugger that R1234yf does not contain any butane. According to Honeywell: "As refrigerant used in MAC (mobile air conditioning), R-1234yf does not contain any butane, but is only mixed with lubricant oil within an AC."

Air conditioning debate heats up for Mercedes
Mercedes stands alone against the law, claiming new climate-friendlier refrigerant too hazardous

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