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Recycle motor waste energy to heat the tesla model S in cold wheater ?

Discussion in 'Model S' started by NielsChr, Oct 25, 2011.

  1. NielsChr

    NielsChr Member

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    Here in scandinavia (and other places :) ), it quite offen become cold (half the year), in norway its not unusual to have minus 25 degree celsius (-13 degree F) or below.
    I know the tesla Model S will be equiped with a electric heater somehow in the size of aprox 1500 Watt, and that the car can be preheated while charging.....witch is a nice feature.

    However here we are doing quite a lot to insulate our houses (30 cm of insulation) to awoid wasting energy just flowing out in the snow, we are also installing solar heating panel on top of our houses to gather this heat ect. .....now if the tesla is made of aluminum witch transfere heat and cold quite well....
    I can forsee that our electric bill will "go insane" if we where to have the car preheatet by electricity while charging all night - heating our houses is expensive already. luckly we can set a timer on the model S so it is only a few hours be fore driving the car heats up, this helps a bit.

    One point where it might help this energy calculation at no energy cost is "recycling" waste energy from the motor. As I have understod the tesla Model S, it is like a ICE, having some energy wasted by the motor. In model S the motor is water cooled, I do not know if this water cooled motor is connected to the heating system inside the cabin, but I truely hope - no need to waste the energy in a radiator/condenser up front and at the same time trying to heat the cabin with a electric heater.

    Does anybody know if the water cooled heat from the motor is being "recycled" inside the cabin like in a conventional ICE using it to heat the cabin (when needed) - in my pressent car (ICE) I regulary use the heater, and the fact that the heater is using energy witch else have been wasted is nice to know.
    In my pressent car there is a small radiator right at the central point the air intake is entering the cabin under the dash. this radiator is made aluminium and at a size of aprox 10x20 cm - this is heated from the cars coolan system and delivers plenty of heat to the cabin - it is something simmilar I would like (hope) to see in the model S.

    E.g. today with tempetur around 10 degree celcius (50 degree F) Im using the heater in my ICE car. As a person trying to think green, I would be a litle sad to know that my car is heating by energy witch could be used for something better and at same time knowing that the car is also wasting energy elsewhere witch could be used in the cabin.

    Does anybody know anything about this ?

    And YES, I know that 1500 even 2000 watt heater in the car willl not "drain" my battery mutch as this could run for hours without takeing more than 10% of my driving range. However it is not driving range Im concerned about - its the energy waste witch can be awoided soly by recylcling already pressent energy witch else would be wasted.

    last I apologize for any speeling here in this post. Im, as you might have guessed, not english speeking person but danish :)
     
  2. TEG

    TEG TMC Moderator

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    That idea has been suggested in the past, so I suspect they have thought about it... But I don't know if they are doing it or not.
     
  3. qwk

    qwk Model S P2681

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    You could do that with a water cooled motor(like the Model S is going to have). It's probably not worth doing as the lag time using such a heater is too great. I would much prefer instant heat at the expense of a bit of range...

    An air cooled motor is a bad choice for heat. Early Vw bug's come to mind. That didn't work so well....
     
  4. Eberhard

    Eberhard #421 Model S #S32

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    Not only from the motor you can capture the heat, also the inverter (PEM) get quite hot too. If you run at 100km/h you need around 15-18kW with 90% efficiency gives 1,5-2kW heat.
     
  5. NielsChr

    NielsChr Member

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    ok, I haven't read all post, so I will go back and see what have been posted previous about this. how-ever now the beta have been shown, some might have new information to share about this.

    I do also agree witch you (qwk) that electric heater have no lag time, but to stay green the electric heater should be turned off when the coolant fluid is so hot that it needs cooling - e.g. after driving 10 minuttes the coolant might be hot

    - have you seen the size of the center radiator up front - that size indicate to mee that Tesla is expecting some heat to be cooled down - the heat could insted be usefull inside the cabin :)

    (not worryed so mutch about driving range, less energy wasted = more green car)


    off topic: Another isue witch have striked me is the Li battery at the buttom of the car - as far as I know Li battery does suffer if charged below 0 degrees celsius - this means Models S battery pack needs heat all night all winter...will we need insulation below the batterys to help keep tempeture up - I asume only a few mm. of iron/aluminium is seperate the minus 20 degree air and the Li cells
     
  6. Robert.Boston

    Robert.Boston Model S VIN P01536

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    The batteries themselves are thermally controlled to maintain temperature in an optimal range. You're correct, though, that heating the batteries during charging uses additional electricity. Over half of Finnish electricity comes from renewable or zero-carbon sources, so you're not harming the environment very much by not insulating the undercarriage, but you might be hurting your electricity bill by a good bit.

    If you do decide to have some insulation overnight, make sure you discuss this with Tesla beforehand.
     
  7. vfx

    vfx Well-Known Member

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    So a Model S that parks in a snow fallen driveway is essentially putting it's batteries on ice?
     
  8. strider

    strider Active Member

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    But the act of charging also generates heat so the car will only need to "heat" the batteries for the first few minutes. After that the act of charging the batteries will keep them warm. It's more of a problem in hot weather as the car will need to actively cool the batteries while charging. On a hot day, when my Roadster kicks on at midnight it sounds like a giant vacuum cleaner is running in the garage.
     
  9. JRP3

    JRP3 Hyperactive Member

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    Jack Rickard from EVTV did a Mini conversion using a liquid cooled MES motor and plumbed the coolant into the heater core along with an electric water heater. I think he said the motor/controller waste heat provided a decent amount of heating without using the electric heater.
     
  10. Todd Burch

    Todd Burch Electron Pilot

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    Regarding preheating the cabin, I suspect that 10, maybe 15 minutes of preheating on a cold day is all that's necessary to bring it to a comfortable temperature.

    As Strider mentioned, charging generates heat so batteries only need to be preheated a little bit. Not to mention that even on a cold day, the batteries don't have to be warmed too much to get to a safe temperature for charging.
     
  11. doug

    doug Administrator / Head Moderator

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    As I understand it, target temp for the batteries is around 20 C, the motor/inverter is kept below 60 C. As it's currently designed, heat from the motor/inverter can go to the batteries, but not the cabin.
     
  12. dpeilow

    dpeilow Moderator

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    Having an electric source for instant heat that then segues into motor heat would be the obvious solution to minimise range loss.
     
  13. zdre

    zdre 40kWh Model S P6415

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    My VW Golf TDI has this. When the engine is cold and it is below 40 F outside, auxiliary electric cabin air heater turns on until the engine warms up. In freezing temperatures, the diesel engine takes more than 10 minutes to heat up enough to be useful for cabin heat, so it is nice not to have the cold air blowing in your face; however, I usually just use the heated seat and turn on the cabin heat later.
     
  14. jcstp

    jcstp Active Member

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  15. strider

    strider Active Member

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    jcstp FTW! Nice find. I had seen that pic but never looked closely at the arrows. Looks like Tesla is way ahead of us :redface:
     
  16. TEG

    TEG TMC Moderator

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    It isn't clear to me that the simplified diagram there confirms what was suggested. How can you tell if heat from the motor is used to heat the cabin?

    That diagram seems to show an A/C system up front that can cool the cabin or cool the battery pack, but I don't see how the diagram shows cabin heat coming from motor heat.
    (Not saying it doesn't... just don't see the "proof" there. Did I miss something?)
     
  17. jcstp

    jcstp Active Member

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    I just guess : when you use the same infrastructure to cool engine, battery and cabin, then this applies also to heating
     
  18. NigelM

    NigelM Recovering Member

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    It was confirmed that there are 2 A/C systems up front, one for the cabin and one for the battery/PEM/motor. The green arrows on that graphic show the regen path from the rear wheels to the battery. I don't see anything transferring heat (or cold) from one environment to another (i.e. cabin to motor or vice versa), unless I'm missing something...?
     
  19. JRP3

    JRP3 Hyperactive Member

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    I agree, the graphic doesn't really show what we are talking about. I think the ideal situation would be that motor/PEM heat goes to the battery pack in cold weather to warm that up or keep it warm, then when not needed it could be sent to supplement the HVAC system. There may not be enough heat left over to make it worthwhile, especially with the large cabin area the S has.
     
  20. dsm363

    dsm363 Roadster + Sig Model S

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    Might something like you're describing be overly complex, costly or not worth the added engineering time? I know nothing about designing a car but maybe they thought of that and decided to skip it. I think it's a good idea and makes sense to me at least.
     

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