Heat and A/C in EVs???

Discussion in 'General' started by Dream'R, Aug 29, 2009.

  1. Dream'R

    Dream'R Well-Known Member

    I'm curious about how the electric powered cars will provide heating and A/C. We all know that a liquid cooled engine provides a source for heating and defogging but what source other than electric resistance will an EV use? I assume regenerative braking will help offset the drain caused by an A/C compressor.

    For those living in climates where winters are very cold and summers are very hot, I wonder how effective the plug-in approach will be. Conventional and hybrid cars suffer due to temperature extremes but still manage reasonably well.

    Is there heat from the electric motor that can be reclaimed, perhaps?


  2. Mr. Pancake

    Mr. Pancake Well-Known Member

    I have no idea but that is an interesting question. Even a little electric heater can draw quite a bit of amperage.
  3. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Roger:

    ___Heating by Ceramic resistance heater and cooling via a dedicated all-electric scroll compressor.

    ___And both knock the hell out of a BEVs range but will still easily be 300 + % more efficient than 400 + % of a std. ICE :(

    ___Good Luck

  4. Dream'R

    Dream'R Well-Known Member

    Thanks for your reply, Wayne.

    Since posting my original questions I wondered if a heat pump approach might work. My home is heated and cooled with an air-source system. I believe that when in heating mode at outside temperatures above freezing, it produces between 250% and 300% heat output per kWh compared to traditional electric resistance heaters. This ratio decreases as the ambient temperature drops, but stays above 100% down to very cold conditions. (One complication, however, is the frost which forms on the outdoor coil which heat pumps melt by briefly reversing into A/C mode, as needed).

    Since there is already an A/C compressor, you have most of equipment needed!


  5. jimepting

    jimepting Well-Known Member

    There's going to be sources of wasted heat, even in BEV. An engineer can easily imagine use of that heat and a very small amount of natural gas as a "hybrid" heater. For those who object to burning clean NG, just think of the original source of the electrical heat, 50% probability of being coal - anytime in the near future. There is no free energy lunch ;-)
  6. brick

    brick Answers to "that guy."

    I think using the A/C compressor for heat is a sound idea and you will probably see it happen. It will have to be more sophisticated than what we all have but the efficiency gains might be worth it. I also expect that, as EVs catch on, you will see a shift toward much better insulation of the vehicle's cabin to keep the load down on the system. (Heat-rejecting glass is in use today and the technology is steadily improving.) I also think that scheduled pre-heating off the plug will go a long way toward coping with cold winter mornings. EV people do that already and it won't take much for the functionality to be built right in to more sophisticated BEVS and PHEVs. For simple defrosting, GM had that licked years ago with the InstaClear windshield that incorporates a thin metallic film that takes a current and heats the windshield directly vs. having to get heat from the engine coolant. I wish I had that on my Prius! By the same token, you can warm the driver through heated seats more efficiently than you can heat all the cabin air plus all the thermal mass to which it transfers its heat.

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