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Cold-weather range hits aren’t as bad for EVs with heat pumps (arstechnica.com)
submitted 2 years ago by to c/technology@lemmy.world
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[–] 19 points 2 years ago (4 children)

heatpumps don't work below about -20C

I don't think that's true? There are cold weather models that can work at COPs > 1.5 at -30C. Are we talking about a sizing constraint for the model here, perhaps?

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  • [–] 7 points 2 years ago (3 children)

    There are, but then I think you'd have problems with the effective rang of the AC in the summer. To my knowledge this is all about at what temperature the coolant is a liquid and when it's a gas (because that's how you exchange heat).

    A traditional AC only needs coolant that does this at summer temperatures. A heat pump tries to use one that will work at colder temperatures as well. A cold weather heat pump goes even further but I think there is a sacrifice in AC efficiency in the summer.

    Somone please correct me if I'm wrong. But I'm not sure if a do-it-all extreme cold and extreme hot heat pump exists, and as a car manufacturer you want to put in the one that will fit most cases, as opposed to a house which only needs to operate in the range of the climate it is built in.

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  • [–] 1 point 2 years ago

    It would make sense if the two stage heat pumps use different liquids in the different stages. I don't actually know how these are made, so I can't assert that this is how it works, but I would be surprised if it worked any other way.

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  • [–] 1 point 2 years ago (1 child)

    I’m pretty sure that’s not how refrigerant (not coolant) works.

    Extra insulation around the expansion valve and piping may be necessary. Or possibly heating around them. But the main limits are the size and speeds of the compressor and fan(s).

    Home heat pumps are getting much better in colder climates. But I’m not sure of the efficiency in vehicle sized units. I’m really interested in them for a camper project I’d like to build though. But might have to wait for more of the cars that feature them to arrive in salvage yards.

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  • [–] 1 point 2 years ago

    Thank you for the correction. I know the properties of the refrigerant are important, but you're correct that the other side of the equation is how much it's compressed. If it's true that compression plays a larger part than the refrigerant at working in lower temperatures, then that does explain why we wouldnt see them in cars. The rise in cost for both the compressor and higher energy usage could make them less appealing to manufacturers.

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