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Are Air Conditioners Chilling the Benefits of Electric Vehicles?

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Debate over the so-called “dirty little secret” of AC fluid muddies the merits of electric vehicles.

Why? Electrification of transportation is an important solution to reduce oil use and global warming emissions. The obvious advantage of electric vehicles (EVs) over conventional cars and trucks is the lack of tailpipe exhaust, meaning the elimination of both smog-forming pollution and carbon dioxide production from the vehicle. Even factoring in the emissions to produce electricity, the benefits of using EVs are significant. In California using an EV like the Nissan Leaf produces 63% less global warming emissions than the average new compact gasoline vehicle.

However, a recent article claims that EVs have a “dirty little secret”: some have a potent greenhouse gas called HFC-134a in their air conditioning (AC) system. The fact that most EVs have HFC-134a in their AC system is true, but the “dirty little secret” characterization is disingenuous for several reasons.

Car AC button with green indicator light

Almost all new cars, EV and conventional alike, use the same type of AC system. (source: User:Mattes, via Wikimedia Commons)

First, this compound (HFC-134a, also known as R-134a) is found in almost all vehicles built after 1994 on the road today, not just in some electric vehicles! When assessing the benefits of EVs, we can’t look at these vehicles in isolation; we need to compare them to the current alternatives. In the case of global warming emissions from AC system leaks, there’s little if any difference between EVs and conventional vehicles.

Second, the global warming impact of HFC-134a leaking from AC units is small compared to that of burning of gasoline. The EPA has estimated that the HFC-134a that leaks over a new vehicle’s lifetime produces the equivalent of about 18 grams CO2 per mile. The emissions produced from using gasoline in a 29 mpg car is about 386 grams CO2 per mile or over 21 times higher than the emissions from AC leaks. We shouldn’t ignore the effect of AC refrigerant on global warming emissions, but reducing the amount gasoline we burn will have the most significant impact on emissions.

Reducing emissions from leaking vehicle AC systems is possible. In fact, the current EPA vehicle emissions standards encourage the use of more climate-friendly refrigerants and there are options available today that reduce the emissions from AC leaks to nearly zero. One option, HFO-1234yf, is already in use in 9 car models, including 2 EVs. We can and should replace HFC-134a in all vehicles with alternatives that are safe, effective, and produce less global warming emissions. However, it doesn’t make sense to look at a relatively minor emissions source that is shared by electric AND conventional vehicles and call it electric vehicle’s “dirty little secret”.

Posted in: Vehicles Tags: , , ,

About the author: David Reichmuth is a senior engineer in the Clean Vehicles Program, focusing on oil savings and vehicle electrification. See Dave's full bio.

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  • Tom Harrison

    Why don’t they just use thermo-electric coolers instead? These are solid state (except for the fans) cooling systems which are cheap, low maintenance, and electrically powered.

    • http://www.ucsusa.org/about/staff/staff/David-Reichmuth.html David Reichmuth

      I believe the problem is that thermoelectric coolers are more costly and less efficient than conventional cooling systems. There are technologies out there like magnetic cooling that could be both more efficient and eliminate the need for a refrigerant, but they are still in the research stage. There is a report from Pacific Northwest National Laboratory that gives a good overview of alternative cooling systems and their outlook for commercial adoption (http://www.pnl.gov/main/publications/external/technical_reports/pnnl-19259.pdf).

  • http://www.jpwhitenissanleaf.com JP White

    Thanks to GE, we can look forward to A/C units on all vehicles using water as refrigerant once magnetic refrigeration becomes mainstream. GE have perfected the system in the lab and believe they are 5 years away from us seeing the first refrigeration units. The system uses 20% less energy than existing technology and no harmful CFC’s.

    http://www.geek.com/science/ges-magnetic-fridge-could-reinvent-refrigeration-in-just-5-years-1587808/

  • Eric Fisher

    Electric cars do not emit Hfc-143a like gas cars because most leakage is coming through the front seal of the compressor. In an electric car the compressor is hermetically sealed just like a normal house refrigerator compressor is. A leak in the compressor seal can not escape to the atmosphere in a hermetically sealed unit unlike a gas car compressor which is driven by an external fan belt and the front seal leaks to the atmosphere unlike the hermetically sealed unit where a leak on the compressor seal is contained and can not escape to the atmosphere. Sorry back to the think tank for you guys.

    • http://www.ucsusa.org/about/staff/staff/David-Reichmuth.html David Reichmuth

      Eric-
      This would be true if the only HFC-134a emissions were from the compressor seals. However, there are other routes to HFC-134a emissions. Slow leaks from fittings, service ports, and hoses contribute to emissions and the automotive environment is much more challenging for a closed, pressurized system than a home refrigerator (How many potholes does your fridge hit?). A larger route to emissions is the releases due to accidents, maintenance, equipment failure, and scrapping of cars. Data from SAE International show about 50% of leaks occur through these larger release events. So even a car (either hybrid or plug-in battery electric) with a perfectly sealed electric compressor still can have refrigerant leaks.
      The main point though is that there is no reason to link HFC-134a emissions specifically to electric vehicles and moreover the reduction in global warming emissions from avoiding gasoline combustion is much larger than any AC-related emissions.

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