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Efficient Heating

Discussion in 'Model 3' started by Jayc, Aug 9, 2016.

  1. Jayc

    Jayc Member

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    Something that crossed my mind is, what is the current state of art most efficient heating technology available as of today? I guess cabin heating wouldn't matter much to those in warmer regions but it is quite important to some of us.

    In the case of Tesla, we can pre-heat while plugged-in but surely, maintaining that temperature when outside is cold could easily become quite a power drain. Also, the battery pack performs best at a higher optimal temperature so surely, it could benefit the whole thermal management system to be designed like home central heating systems such that there is a single point efficient heat source and heated water or oil is carried around vital components of the car including cabin. Or is that an overkill for Model 3 ?
     
  2. JeffK

    JeffK Active Member

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    They are supposed to have a new type of AC on the Model 3 so it's anyones guess.

    AFAIK on the Model S currently the heat management system takes heat from the battery and or the motor and as it heats the gycol it can be used for cabin heat (via heatsink to other glycol loop) in addition to the heater.

    [​IMG]
     
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  3. eSpiritIV

    eSpiritIV Member

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    Cooling typically is the most energy intensive of the two HVAC methods typically. I am not sure what is true with Tesla's systems. At least JeffK has pointed out that Tesla already does effciency measures to capture wasted heat produced from the battery pack and utilize it for good. Teslas "Radiator" is of the freon type i know, which requires much less maintenance than ICE cars. No engine contamination, and maintenance to top off fluids all the time. Jiffy Lube is in for a hurting :)
    I read that owners of model S find that using their electric heated seats rather than the HVAC system is more efficient in use of energy so you can drive a longer range. Basically keep plugged in for battery system warm up, then switch on heated seats for your drive.
     
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  4. garsh

    garsh Re Member

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    In what vehicle? If you're talking about an combustion vehicle, that's because heat comes for free.

    My Leaf has extremely efficient A.C. But I can't run the heater because of how badly it limits my range.
     
  5. inspron

    inspron Member

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    Uh....you mean "least" not "most". If you meant what you said you are grossly misinformed.
     
  6. Saghost

    Saghost Active Member

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    Your typical resistive heat system is almost 100% efficient - nearly all of the energy ends up as heat in the target area. That's what the Model S and most first generation EVs have (though the S also adds a fancy system to collect what little motor waste heat there is for the battery pack.)

    But that still leaves heating on a cold winter day as a huge load ave a significant fraction of the driving power requirements. Which is why some EVs have gone to heat pumps.

    Through some creative math, a heat pump can achieve efficiency far beyond one hundred percent, when defined as heat delivered to the target area over power consumed - because instead of trying to generate heat, it moves the heat from elsewhere. This gets markedly less efficient as the temperature falls, though - and in wet climates you have problems with ice accumulating on the outside coils.

    There isn't an easy answer, but I expect to see more heat pump hybrid systems in the future, along with better insulation to reduce the energy needed in the first place.
     
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  7. zenmaster

    zenmaster Member

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    Besides improving the efficiency of the heating system, they could potentially improve insulation of cabin and of the battery itself.
     
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  8. Jayc

    Jayc Member

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    I agree that cabin insulation is good because the cabin itself does not generate heat but with the battery, I expect they'd want to keep the temperature under control as it generates heat.
     
  9. Saghost

    Saghost Active Member

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    Better insulation for the battery will reduce loads, too - both heating and cooling of the battery is done more for ambient conditions than because of energy lost in use.

    You'll certainly need to retain the cooling system capacity it has now or possibly even increase it slightly for ever faster supercharging (possibly also teach the car to prepare for upcoming Supercharging sessions by precooling the pack?) but the car will be made more efficient by more pack insulation (offset against the cost and weight/volume of the insulation, of course.)
     
  10. HillCountryFun

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  11. mspohr

    mspohr Active Member

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    Heat pumps are more than 100% efficient. Typically over 300%. This is not due to "creative math" but is due to physics. You are not creating heat, you are moving heat from one area to another.
     
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  12. JeffK

    JeffK Active Member

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    This assumes there's heat to pull... and if not, it still has to be generated. You aren't going to get 300% in a car. You would in a geothermal system because you're pulling heat from the ground.
     
  13. Saghost

    Saghost Active Member

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    Aside from the creative math part, everything you said was in my post that you're quoting and correcting. I would argue that any math which results in more than 100% efficiency is by definition creative - in this case, it's correct for the application and the comparisons, but still odd.

    (If you measure the efficiency of any part of the heat pump, it is less than 100% - like any physical process. It only becomes greater than 100% as a system because of the way we define the system boundaries.)
     
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  14. mspohr

    mspohr Active Member

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    There is always heat. Any temperature above absolute zero (-273 C) has heat.
    The efficiency depends on the temperature difference. The greater the difference, the lower the efficiency.
    My heat pump water heater has a 3.25 (325%) efficiency rating (making 120 F water from air with a temperature as low as 32 f). It makes hot water using only one third of the energy as a resistance heater.
     
  15. JeffK

    JeffK Active Member

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    My house is heated via heat pump... sucks ass in the winter.
     
  16. mspohr

    mspohr Active Member

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    Most good heat pumps have resistance heating backup for when it gets very cold.
     
  17. River

    River Member

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    I wouldn't worry too much about it being in UK. From what I saw it rarely goes below −10°C so you should be ok ;). People here in Québec / Canada (where some days are below -30°C) survive in electric cars with even less range than Teslas (and I guess other regions get even colder than that).
     
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  18. River

    River Member

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    Geothermal in a car, this is an interesting idea! o_O:rolleyes:
     
  19. Saghost

    Saghost Active Member

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    Maybe I can add a hydroelectric generator to the geothermal system for extended range? ;)
     
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  20. Topher

    Topher Energy Curmudgeon

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    Some things to note:

    1) Heating seats with resistance heat isn't more efficient, it just puts the heat where you benefit more from it (in your body rather than in the air), and losses are less since the heated area is smaller.
    2) Heat pumps (e.g. air-conditioners) move heat at about the same efficiency whether heating or cooling.
    3) Cooling costs more if moisture is being condensed (970 times more energy to condense water versus cooling it 1 degree). This inflates the energy use of 'air-conditioning'.
    4) Heat pumps are 3-4 times more efficient than resistive heating. Dropping off at extremely low temps.

    Thank you kindly.
     

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