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Heat pump for cabin heating?

Discussion in 'Design' started by Greg Peden, Aug 2, 2017.

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  1. Greg Peden

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    Has anyone manged to find out if the cabin heating for Model 3 is provided by either electric resistors or a heat pump? I am really hoping for the latter, as in Canada I depend on car heat far more often than air conditioning.

    I have tried to do a lot of research on this myself but I have found nothing clear on this.
     
  2. MarkB

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    I was wondering the same thing. Nissan Leaf information seems to indicate it works brilliantly, supported by anecdotal reports (including Leaf owners that have used both the older/basic resistance heaters and the newer (and higher trim level)) heat pump version.
     
  3. Greg Peden

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    I should add that I would expect the heat pump solution to ALSO include electric resistive, since in very low temps a heat pump would be unable to perform.
     
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    • garsh

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      Don't forget, this car includes heated seats. You want to primarily use those. They'll be more efficient than a heat pump heating the air blowing around you.
       
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      • Greg Peden

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        Well, the heated seats are a premium upgrade so many cars won't have them.

        I understand that there are options, but bottom-line, I am curious about if the car comes with a heat pump or not. Simple as that.
         
      • garsh

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        Heated front seats are standard. Premium adds heated rear seats.
        [​IMG]
         
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        • Akilae

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          Even without premium this car is quite well equipped imo. I also thought that heated seats are reserved for premium.
           
        • MarkB

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          Heat pumps don't heat the air as such, they capture heat from the outside air to raise the temperature of the inside air. it's essentially an air conditioner in reverse.

          They are VERY efficient until very low temperatures (when there's not enough heat left in a given quantity of air), so - as Greg Peden said above, there would need to be resistive heating as well -- but that would be a very cheap part of the system.

          In houses, heat pumps heat in winter and cool in summer.
          The A/C already exists -- I don't think a completely separate system would be required.
           
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          • Greg Peden

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            Just to add a little bit of engineering talk to this, the point of using a heat pump is that you are moving heat energy instead of creating it, therefore your energy productivity is not bound by thermodynamics. There is nothing wrong with using 100 watts to pump in heat at a rate of 400 watts if your heat pump is efficient enough. Electric resistance gets one-for-one energy productivity, ie burning 100 watts gets you 100 watts of heat.

            In the broader picture, using a heat pump and glycol loop, or something similar, could in concept move waste heat from the battery in to the cabin, instead of using the radiator to vent heat. This is similar to what is done to heat a car with a combustion engine, however since we can count on massive waste heat coming off of the engine this is a very robust solution for all cases. Since electric cars waste far less energy in operation, an active cabin heating solution is needed.

            Heated seats are a good call for short-haul trips, but given a longer drive when range actually matters, over the course of the several hours of operation the cabin interior air will end up being heated one way or another, in which case you would benefit a lot from a heat pump. Similarly, a heat pump could be used to keep the battery conditioned in cold weather instead of electric resistance.

            In the simplest of terms, an air conditioner could be "turned around" with some airflow louvers and made in to a heat pump, however air conditioners and heat pumps are working with very different air temperatures and for that reason sometimes benefit from different designs with separate hardware.

            Personally I have a hard time imagining Tesla having promoted the climate control system in the car so hard as they did while still being the only major electric car manufacturer relying on resistive heating. So I am very hopeful for a heat pump.
             
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            • garsh

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              Heated seats tend to be more efficient than heat pumps in cars simply because you limit the heating to the exact locations where it is needed, instead of moving heated air around the cabin.

              With the heated seats & steering wheel in my Leaf, the only part of me that feels left out are my cold toes. :)
               
            • Tom Bodera

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              The volt uses a heat pump and adds resistive heat.

              The model S/X to my knowledge did not use heat pumps to "keep things simple". Another thing to break I guess.
               
            • mig

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              Yes, and "bundling up" is even more efficient than heated seats/steering wheel :p.

              I would hope they include a heat pump instead of resistive heater, but if they can get by with 1-1.5kW heater it shouldn't affect range *too* much (though for comparison, a heat pump would use probably 300W to move the same amount of heat).

              In my LEAF I would *never* use the heater, but in the i3 the heater seems to be much more efficient and doesn't affect range nearly as much. I can tell you it is much nicer to have the cabin heated. My kids sitting in the unheated rear seats especially appreciate that.
               
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              • garsh

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                That's exactly what I end up doing in my Leaf in the winter. I've disconnected the heater altogether. So I bundle up & use the heated seats and steering wheel. Otherwise, it doesn't have enough range for my commute.

                And that's why I'm getting my 3 with the long range option. :p
                 
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                  • mig

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