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Your car air-con is consuming half your fuel in heavy traffic

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Shuttershock

Shuttershock

Asian traffic!

After a recent visit to Jakarta, where I experienced serious developing city traffic congestion, I thought I would explore the fuel consumption impacts of this congestion using the transport calculator I developed for the EPA Victoria Greenhouse Calculator. I assumed a ‘small’ car (Corolla size), 10 km/h average speed, with stops every 50 metres and a Darwin climate.

The results are only approximate, as the model is fairly basic and changes in environmental and traffic conditions and driving techniques can affect the outcomes significantly.

The big message was that air conditioner usage was almost half of total fuel use under these conditions. Fuel consumption for movement was, surprisingly, not very different from typical Australian usage.

It seems that the reduction in aerodynamic drag from slower speeds may offset the long periods of idling and inertia effects of frequent stops and starts from low speed.

A well-designed hybrid (e.g. a Prius) used half as much fuel overall and saved two-thirds of fuel used for movement. The large savings reflect the potential to recover and reuse a lot of braking energy from the stop-start driving, and the higher efficiency of the Prius engine.

A focus on optimum car air conditioner efficiency and the thermal performance of the car body could save a lot of fuel! High efficiency air conditioners and refrigerants with evaporative cooling of the condenser— which could be retrofitted—could help a lot. So could a light colour or ‘cool roof’,

or insulation of roof, shading (e.g. the old ‘tropical‘ roof used on 4WDs) and effective heat-reflective coatings or shading of windows. Some of these options could increase aerodynamic drag when a car finally escapes the congestion, though, so careful design is needed.

This looks like fertile ground for research into new cars and their air conditioners, and retrofit measures.

Of course, improved urban planning, effective public transport and electric bikes would reduce the time wasted (and productivity lost) trapped in traffic and cut air pollution too.

Alan Pears, AM, is one of Australia’s best- regarded sustainability experts. He is a Senior Industry Fellow at RMIT University, advises a number of industry and community organisations and works as a consultant. This story was first published in Renew magazine. Reproduced with permission of the author.

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  • Ian

    Car air con is increasingly common in parked cars even when the temperature is reasonable. And is common practice where I work, (though I have raised the issue.) Often nobody even the vehicle! I am very tempted to just jump in and drive away!

  • Peter B

    Please, please more research so that refrigerated delivery trucks don’t have to keep their Diesel engines running while making deliveries let alone stopping for morning tea or heaven forbid lunch. Why don’t the Greens do something useful and get on to this real pollution problem now!

    • Pedro

      Why don’t you start a petition, talk to some refrigeration engineers?

      • Peter B

        Not sure why I should need to start a petition when we have the Greens formed to combat pollution. I am so disappointed that even when in power in Tasmania as part of the Government they did not advocate or propose legislation to:
        • Stop sewerage overflows in the Derwent, Tamar or Huon Rivers,
        • Stop storm water flowing into same.
        • Have annual inspections of our very polluting old car fleet.
        • insist the Feds bring forward the latest Euro pollution controls for new cars.
        When I argued that they weren’t doing their basic job I was accused of being a Conservative. One accused me of being a “Tory”, which is a form of expression used by Anthony Albanese,
        Then again Pedro, you are right, I had better start a petition or move out of an apartment with shops below that have refrigerated delivery truck parking.

        • Pedro

          Good points you make Peter. There are so many sources of pollution and damaging practices done to the environment around the country, how can one minor party tackle it all at once? I would tend to put the responsibility back onto those causing the pollution and pressure the government of the day at both state and federal level. You could ask what the hell is the EPA doing? After all it is a tax payer funded government department with the resources and a bunch of law enforcement tools behind it.

          The point I am trying to make is that is not the Greens job to sort out all and every single environment concern that anybody may have. Their job is to get elected in so that they can influence government policy and make laws that go some way in protecting the environment.

          • Peter B

            Pedro, I am afraid you miss the point. The Greens were in a coalition in power with Labor in TAS. People like the EPA only respond to the Legislation that is drafted by Government and enacted by the Parliament.
            The only thing the Greens did, whilst in Ministerial positions when in Government, to enhance Tassie’s clean, green environment was to have enacted a ban on non-reusable/re-cyclable plastic bags. They even failed to even trying to enact the SA container deposit levy.
            They also supported a 3yr forestry debate that excluded Tassie’s speciality timber industry (boat building, furniture and fine art sculptures) and luckily they failed in their attempts to close off the Bell Bay Gas Fired generating plant that would have put the State in a fine mess given the break in the Bass Link power cable and the current pressure on hydro generation.
            Your fine words belie the fact that while (now Senator) Nick McKimm may well have been interested in saving the world he did not enhance or improve our own local environment.
            To paraphrase the current Australian of the Year “The standard you walk past is the standard you set.”
            As I gaze from my apartment window at the sign for the storm water drain that empty’s into the Derwent River 25 metres out from the Long Beach swimming strip I can only shake my head at the Greens hypocritical moral posturing.

          • Pedro

            Sorry Peter. I have to respectfully disagree with you, I think you are missing the point. If you are unhappy about a storm water drain then take responsibility and do something about it. Let your concerns be known to your local council, local member and those responsible for storm water drains. The greens did not put in the drain. Do you expect them to mobilize all their members and have a sit in until the drain issue is fixed.

            Your argument fails logically. So some how its all the “Greens” fault that there are a pile of environmental issues that have not been sorted out and they completely blew the massive opportunity to fix it all up with a couple of terms in a state coalition government. That is a completely unrealistic expectation.

          • Peter B

            Pedro, I must agree with you, as that was my point, the Greens cannot be relied to set standards and fix our local environment even when in Government; it is as always up to us. My completely logical point is that they are not doing the job for what they to profess to stand for (at least here in the Denison electorate (State/Federal) and the Hobart City Council area (local Govt)) i.e. a clean, green environment.

    • Graham Anderson

      Incorporate appropriate phase change material

  • DogzOwn

    When will need for “innovation” warrant car construction double skin vacuum, like thermos flask, double glazed? How far can our fantasies go? Sooner or later, cars will be obsolete, preferably sooner.

  • Sadly “it’s the culture” Google
    “https://www.google.com./why+people+leave+their+engines+running.

    It infuriates me – especially when the temperature is about 25C … I have disconnected my A/C – better to let the air flow through .. OK – when it gets REALLY humid (and there are 4 or more in the vehicle) – a rag or tissue with a little dish washing detergent clears the inner windscreen immediately – Plus most vehicle A/C’s use R 134a which is a potent green house gas – and eventually leaks out … ensure that the next time you fix your car a/c (if you must) – use hydrocarbon refrigerants GHD=1 (and they are sooo much cheaper)

  • JeffJL

    I suspect that AC in BEVs proportion would be even higher (as well as those vehicles that their engines stop when they are stopped).

    BEVs should be stopped from being used in urban situations!(/s)

  • GregX

    There are 2 things that will fix this problem or at least minimise it. Both rely on moving everyone to EV’s. One is the integration of solar panels into the roof and bonnets of cars. The other is simply being able to open your window in traffic without getting mouthfuls of ICE exhaust. EV’s will even fix the issue of air pollution and exhaust stacks from tunnels but that is another issue.