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Lighter colored cars are 2% more efficient

Discussion in 'Tech Talk' started by ModFather, Aug 7, 2017.

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  1. ModFather

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  2. Sandy

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    What about winter? Dark color cars are much warmer to get into after sitting in the sun a few hours than light colored cars. Opposite in the summer. Net net.
     
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  3. nisse

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    Except the sun doesn't shine much in winter.
     
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  4. SoFlaModel3

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  5. ModFather

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    So that begs the question, do people with darker colored cars and larger rims drive their cars more 'aggressively?' I don't know the answer, but I am sure there is a study somewhere that addresses the issue.
     
  6. SoFlaModel3

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    #6 SoFlaModel3, Aug 7, 2017
    Last edited: Aug 7, 2017
    You may be on to something...
     
  7. ModFather

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  8. SuperMario

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    My guess is this study has a lesser factor on M3 since the roof is glass, not painted steel
     
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  9. SSonnentag

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    With Tesla, I doubt it makes any measurable difference at all as the cabin is all glass anyway. So there isn't any difference between a white and a black car from the window sills on up.
     
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  10. Badback

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  11. Badback

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    Maybe it only impacts police behavior.
     
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  12. ahagge

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    Hey @ModFather, have you run across any similar study concerning interior colors? As has already been mentioned, I'd think that the Model 3's glass roof would negate most of the effects of the exterior color story, but I'd also think that there would be a non-trivial difference with a white vs black interior...
     
  13. SSonnentag

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  14. JWardell

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    I'm sure the exterior color makes some difference when you have a huge roof panel...but all Model 3s of any color will have identical top surfaces: all glass.
    If anything there may be a different between black and white interior color. But Tesla's special homebrew tints and filtering will probably filter most of the IR out.
     
  15. Mark C

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    I wish that were the case. The Premium package lists the all glass roof as a part of what you get for your $5k.
     
  16. JWardell

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    The metal roof is still only a small percentage of the roof. Even without the premium glass roof, most of the top surface will be glass.
     
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  17. jsmay311

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    Kinda surprised that no one in this thread pointed out the fundamental difference between how ICEVs and BEVs heat their cabin. Any such study considering ICEVs would have different results than if they were looking at BEVs, principally because ICEVs have lots of "free" engine heat to warm the cabin when it's cold out, but they have to use extra energy to run the A/C compressor to cool the cabin when it's hot, and therefore they would generally benefit from less solar heat gain.

    In contrast, BEVs have to use battery energy to create heat when it's cold and that generally requires more energy than an A/C compressor.

    So (dependent on the climate and use cases, of course), BEVs might actually benefit from a darker paint color instead of a deficit.

    (Heating/cooling the battery itself would be another important difference to take into account.)
     
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  18. RolfS

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    I think that study is missing the part about driving the car. One does not just sit in a car one drives somewhere in a car. Black is a good emitter of radiant heat. When you see black it is actually the absents of any visible photons that reach your eyes. Black is not a color it is the absence of a color, your actually seeing nothing that the eye can register.That is because black absorbs the visible light. The energy that the black absorbs has to go somewhere. It does, it is radiated as IR (Infrared Radiation) which is heat. White paint is just the opposite it reflects light (that is why it is white). It is a good emitter of visible light therefore it does not produce as much heat, but it still does produce some.

    Therefore a black car will radiate much more heat that a white car will and heat up the interior much faster, but at some point an equilibrium will be reached where both interiors will be just as hot. It might just take a little longer in a white car. I am assuming the cars have an equal amount of insulation.

    In a car the heat is going to build up while sitting still, but as soon as you drive the car the wind rushing past the body will act to cool the body. The wind will absorb the IR and in turn the metal body will cool. That is one reason why after driving for some time the A/C can run at a reduced rate at just a fraction of the energy it needs to cool the interior of the car down while parked. Try it yourself. Touch the roof of the car when just sitting on a hot day. Do it quickly so you don’t burn your hand. Then drive for 10-15 minutes continuously and reach up and touch the roof of the car again. It will feel no warmer than the ambient temperature. That is because the air rushing past the car will take the heat away faster than it can form. Therefore when driving I think it makes no difference what color your car is.

    The glass roof on the Tesla is designed to reflect most UV and IR and remains transparent to visible light, an additional benefit.

    So their conclusion is right but they failed to mention that when actually driving the heat build up is negated by the air taking the excess IR away faster than it can build up. So unless you sit around in your car a lot with the A/C on (maybe at SCs ) I don't think it is anything to worry about.
     
  19. John

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    Dark cars do get hotter in the sun, but apparent color is more complicated than "black is 0% reflection, and white is 100%."
    100% reflection looks like a mirror. Paint requires diffuse body effects in subsurface layers to look white.
    Not important. Just sayin'.
     
  20. arnis

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    It's been proven that there is almost no radiating heat happening with these temperatures. More than 99,9% is lost by convection.
    While car is moving, even more convection is happening.
     

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