4 ms·

Part of it comes down to an air conditioner just being a heat pump that works one way only, so there’s fairly easy opportunity to build in some efficient heatin

Part of it comes down to an air conditioner just being a heat pump that works one way only, so there’s fairly easy opportunity to build in some efficient heating capacity going forward without much incremental cost by installing reversible systems. The other thing is that a heat pump can be so efficient, that it’s net beneficial to burn nat gas at a power plant and use that electricity to run a heat pump. But this all falls apart near and below freezing temperatures. NYC will still want to have direct-burn natural gas heating for cold days because that’ll be more efficient than resorting to resistive heating.

InvertedRhodium 5y ago
TIL - I always thought that heat pump and air conditioning were just different ways of saying the same thing - here in NZ, I don't think I've ever seen a heat-only heat pump.
- NoahKAndrews 5y ago
  We don't have heat-only heat pumps, we have cooling-only air conditioning.
- rkowalick 5y ago
  To clarify, in the US, there are two commonly used HVAC heat pumps: - A/C units, which can only cool a room but can’t heat it up - Heat Pumps, which typically do both.
  - avianlyric 5y ago
    What’s particularly frustrating is that the only thing that separates one from the other is the inclusion of a $20 reversing valve[1], and some software that can use it. [1] https://en.m.wikipedia.org/wiki/Reversing_valve https://en.m.wikipedia.org/wiki/Reversing_valve
    - mlyle 5y ago
      Well, that and you tend to split heat pump systems instead of pumping around warm air to pick up efficiency. And the design of the condensers, etc, is a little different for efficiency and to cope with e.g. condensation outside.
  - doikor 5y ago
    The AC unit can do heating if you just run the pump in the opposite direction. It is just a feature the manufacturer did not bother to install/wants extra money for (it is literally a single $20 part for the valve). Obviously they are not the most efficient heaters as they are not designed for it but they would still work.
endisneigh 5y ago
> NYC will still want to have direct-burn natural gas heating for cold days because that’ll be more efficient than resorting to resistive heating. I agree. With climate change and unpredictable weather I really wouldn't go all-in on heat pumps. Even with hyper-heat it only works efficiently down to 5 degrees Fahrenheit. NYC rarely gets colder than that, but I wouldn't be surprised if the extreme cold days are the same days where electricity has problems. Those two things together means people freezing to death. I think buildings should have both, and default to heat pumps.
- newjersey 5y ago
  > Those two things together means people freezing to death. If we want to prevent people from freezing to death, the best way is to help people get 1. food 2. clothes 3. shelter 4. health care. I'd argue gas based heat isn't even on the list. As you said, we should not go all-in on heat pumps. We can and should have alternate sources of heat for vulnerable people (I am thinking hospitals, retirement communities, and so on). I am confident that healthy, well-fed, appropriately dressed people in well insulated homes do not die because the weather outside dips below freezing for under a day.
  - gscott 5y ago
    https://www.wsws.org/en/articles/2009/01/bayc-j28.html https://www.wsws.org/en/articles/2009/01/bayc-j28.html
- drusenko 5y ago
  That’s a big misconception. Latest generation heat pumps can work well even in very cold climates eg Lake Tahoe. The “fixes” needed to make that work aren’t that dramatic eg a bit of pre-heating of some parts with regular electric heating elements.
  - endisneigh 5y ago
    What's the big misconception? My comment doesn't disagree with what you're saying.
kibwen 5y ago
> But this all falls apart near and below freezing temperatures. That's a concern for designs with air-based heat exchangers, but for environments where this is expected to be a problem you can instead exchange heat via pipes into the earth, where it remains a more-or-less constant 50F/10C year-round. Pump heat out of the earth in winter, pump it back in in the summer.
doikor 5y ago
> But this all falls apart near and below freezing temperatures. There are heat pumps designed for cold climates that work well into the -30C range or so still holding a COP of 2 or more. Here are some test results from Finland from a few years ago https://www.scanoffice.fi/vttn-testiraportit-ilmalampopumppuvertailu/ https://www.scanoffice.fi/vttn-testiraportit-ilmalampopumppu... (Lämpökerroin = COP) And if one is doing it at district level just pump the heat from the ground or sea where the temperature stays the same all year around.

InvertedRhodium 5y ago

TIL - I always thought that heat pump and air conditioning were just different ways of saying the same thing - here in NZ, I don't think I've ever seen a heat-only heat pump.

NoahKAndrews 5y ago
We don't have heat-only heat pumps, we have cooling-only air conditioning.
rkowalick 5y ago
To clarify, in the US, there are two commonly used HVAC heat pumps: - A/C units, which can only cool a room but can’t heat it up - Heat Pumps, which typically do both.
- avianlyric 5y ago
  What’s particularly frustrating is that the only thing that separates one from the other is the inclusion of a $20 reversing valve[1], and some software that can use it. [1] https://en.m.wikipedia.org/wiki/Reversing_valve https://en.m.wikipedia.org/wiki/Reversing_valve
  - mlyle 5y ago
    Well, that and you tend to split heat pump systems instead of pumping around warm air to pick up efficiency. And the design of the condensers, etc, is a little different for efficiency and to cope with e.g. condensation outside.
- doikor 5y ago
  The AC unit can do heating if you just run the pump in the opposite direction. It is just a feature the manufacturer did not bother to install/wants extra money for (it is literally a single $20 part for the valve). Obviously they are not the most efficient heaters as they are not designed for it but they would still work.

endisneigh 5y ago

> NYC will still want to have direct-burn natural gas heating for cold days because that’ll be more efficient than resorting to resistive heating. I agree. With climate change and unpredictable weather I really wouldn't go all-in on heat pumps. Even with hyper-heat it only works efficiently down to 5 degrees Fahrenheit. NYC rarely gets colder than that, but I wouldn't be surprised if the extreme cold days are the same days where electricity has problems. Those two things together means people freezing to death. I think buildings should have both, and default to heat pumps.

newjersey 5y ago
> Those two things together means people freezing to death. If we want to prevent people from freezing to death, the best way is to help people get 1. food 2. clothes 3. shelter 4. health care. I'd argue gas based heat isn't even on the list. As you said, we should not go all-in on heat pumps. We can and should have alternate sources of heat for vulnerable people (I am thinking hospitals, retirement communities, and so on). I am confident that healthy, well-fed, appropriately dressed people in well insulated homes do not die because the weather outside dips below freezing for under a day.
- gscott 5y ago
  https://www.wsws.org/en/articles/2009/01/bayc-j28.html https://www.wsws.org/en/articles/2009/01/bayc-j28.html
drusenko 5y ago
That’s a big misconception. Latest generation heat pumps can work well even in very cold climates eg Lake Tahoe. The “fixes” needed to make that work aren’t that dramatic eg a bit of pre-heating of some parts with regular electric heating elements.
- endisneigh 5y ago
  What's the big misconception? My comment doesn't disagree with what you're saying.

kibwen 5y ago

> But this all falls apart near and below freezing temperatures. That's a concern for designs with air-based heat exchangers, but for environments where this is expected to be a problem you can instead exchange heat via pipes into the earth, where it remains a more-or-less constant 50F/10C year-round. Pump heat out of the earth in winter, pump it back in in the summer.

doikor 5y ago

> But this all falls apart near and below freezing temperatures. There are heat pumps designed for cold climates that work well into the -30C range or so still holding a COP of 2 or more. Here are some test results from Finland from a few years ago https://www.scanoffice.fi/vttn-testiraportit-ilmalampopumppuvertailu/ https://www.scanoffice.fi/vttn-testiraportit-ilmalampopumppu... (Lämpökerroin = COP) And if one is doing it at district level just pump the heat from the ground or sea where the temperature stays the same all year around.