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I think heat pumps are far more likely to be a 'savior' in terms of energy efficiency and climate issues than going back to burning wood en masse, which the end

I think heat pumps are far more likely to be a 'savior' in terms of energy efficiency and climate issues than going back to burning wood en masse, which the end of this article handwaves away even though it seems pretty obvious that it isn't really sustainable.

duxup 5y ago
And heat pumps can be fit into existing systems.
- hasmanean 5y ago
  Yeah but this “system” has advantages heat pumps don’t have. Such as the lack of a convective air circulation system.
  - duxup 5y ago
    So… then you can’t use it to heat other rooms. That’s not an advantage.
    - hasmanean 5y ago
      Yes…it’s not a solution suitable for western style houses. But maybe if you designed your entire house around the large central fireplace…it could work. I imagine that’s what they do in Siberia.
ulrikrasmussen 5y ago
Manually operated wood furnaces are also terrible with regards to particle emissions. The article acknowledges that and claims that oven stoves do not have this problem because they can reach higher temperatures. But that ignores the fact that there is a time period until the fire has reached the right temperature during which the particle emissions are very high (particle emissions from wood furnaces are scary high and dwarf emissions from cars). If the whole neighborhood is heated by these things, then you have several hours of the day with smoke and particles, even if everyone operates their ovens correctly so they reach the correct temperatures for a clean burn. Furthermore, heat pumps are just so much more efficient, as they actually move several times the amount of energy as heat as they consume as electricity. Combined with floor heating - which gives a much larger surface area for heat dissipation than these oven stoves can ever give you - you can further lower the temperature of the water, raising efficiency even more. Floor heating is also way more comfortable as it gives an even distribution of heat throughout the house, and you don't get cold feet.
- gorgoiler 5y ago
  Silly question, but if a heat pump extracts warmth out of the ground, how much extraction can take place before that warmth runs out? Quantitatively, of course planet Earth has infinite warmth to give compared to what we could possibly extract but I have no idea what the numbers are actually like.
  - jabl 5y ago
    Ground source heat pumps with shallow heat collection coils extract heat stored by the sun during the previous warm season. With deeper boreholes you're extracting heat from radioactivity decay. In both cases the rate at which you can extract that heat depends in the heat transfer rate in the ground around the coils/boreholes.
  - Flashtoo 5y ago
    Not a silly question at all. Firstly, heat pumps do not need to extract heat from the ground, they can also extract it from the air or a body of water. The heat moved from outside to inside a building will always leak out eventually, returning to the environment. In the case of air heat pumps this means there is very little change of local air temperature over any time scale. You are right that extracting too much heat from the ground will make the ground around the exchanger too cold, which will make the process less efficient and have negative environmental effects, which means it is illegal in many places. Smaller systems like for homes are usually very shallow and will regain enough heat from the air and sun over the course of the year. Larger systems can be problematic. The common solution to this is to use the ground as a thermal battery (or install a thermal battery in the ground, using it for insulation). Then you can use your heat pump to extract heat in the cold season and in the warm season you can cool the building and move that heat back underground. This has the extra benefit of being even more efficient, since you are basically just trading heat and cold from season to season.
  - stormbrew 5y ago
    I think this is a really good way to put it into perspective, because the units we use for temperature are very misleading on this front: Where I live, the outside temperature goes from -40C to +40C at the extremes (though those are rare and the 'normal maxes' are more like -30 to +30). In F that's -40 to +104F. But in kelvin, which actually measures the amount of energy in the air, that's 233K to 313K. It's not a small difference in the amount of energy, but neither number is anywhere close to zero. It's a common meme with heat pumps that they "stop working under X temp" because it's too cold, but the actual, immediately practical issue is moisture. Ice is a great insulator, so when the outside part of your heat pump is covered with ice it no longer works well. Presumably the same might be true of ground source heat pumps and frost, though I know less about that. Obviously there are other factors like the efficiency and operating range of the coolant used and such, but you hit this moisture barrier before those. There are ways around that (I installed an air source heat pump this year and it runs in reverse (ie. as an air conditioner) periodically to defrost the outside part. I've used it successfully to heat my home down to about -20 outside before it no longer spends any real time in heating mode. It wasn't cheap though, and is almost certainly not cost-effective even over a very long time period. That's not my priority though.
cheese_goddess 5y ago
I don't know if this is right. We're talking about thermodynamic heaters, like Peltier elements, correct? Those need electricity to work and the question then becomes: where does the electricity come from? Burning wood, if it can be done efficiently, and like the article says, is almost neutral in terms of carbon emissions because you're only realeasing carbon that is part of the atmospheric carbon cycle, circulating between the atmosphere and the biosphere. With a heat pump, if the electricity comes from burning fossil fuel then you're contributing to greenhouse gas emissions (all those carbon gasses are released in a much higher rate than they were stored and, more importantly, than what the environment can keep up with). If the electricity comes from renewable sources, then it's a real saving, but how probable is that right now? If you can burn wood at 80-90% efficiency, as the article claims, then that's a net gain right now. Personally I also don't like the reliance on a complicated mechanism that can't be easily made by hand. I don't like that because it means the technology is harder to adopt. I'm talking about heat pumps. By the sound of it an "oven stove" is much easier to make and maintain, if they had them back in the middle ages. So they can be used by many more people for whom the price of electricity is higher than the price of scrap wood. For a technology to make a difference it doesn't just need to be efficient, it must also be affordable and useable by everyone.
- i_am_proteus 5y ago
  "Heat pump" typically refers to a refrigeration cycle unit that uses a working fluid to transfer heat from a cold body to a hot body. An air conditioner uses this mechanism to heat the outside of the home (cooling the inside). Technically electricity is not required, although most of these units, in practice, use electricity, converted to mechanical energy, to power compressors. Heat pumps are much more efficient than e.g. electric baseboard heating because the energy consumed is used to move heat, rather than to generate heat. The efficiency difference drops in "very" cold climates (ambient temperatures well below freezing) and in those climates the heat pump usually is backed up by a direct heating method such as resistance electric heating, gas furnace, et cetera.
  - deleted 5y ago
    [deleted]
fulafel 5y ago
To go to the opposite direction from the low tech starting point: You could have both a micro-chp setup to genetate both heat and electricity from the fuel, leaving the option to use the electricity on a heat pump or other household demands.

duxup 5y ago

And heat pumps can be fit into existing systems.

hasmanean 5y ago
Yeah but this “system” has advantages heat pumps don’t have. Such as the lack of a convective air circulation system.
- duxup 5y ago
  So… then you can’t use it to heat other rooms. That’s not an advantage.
  - hasmanean 5y ago
    Yes…it’s not a solution suitable for western style houses. But maybe if you designed your entire house around the large central fireplace…it could work. I imagine that’s what they do in Siberia.

ulrikrasmussen 5y ago

Manually operated wood furnaces are also terrible with regards to particle emissions. The article acknowledges that and claims that oven stoves do not have this problem because they can reach higher temperatures. But that ignores the fact that there is a time period until the fire has reached the right temperature during which the particle emissions are very high (particle emissions from wood furnaces are scary high and dwarf emissions from cars). If the whole neighborhood is heated by these things, then you have several hours of the day with smoke and particles, even if everyone operates their ovens correctly so they reach the correct temperatures for a clean burn. Furthermore, heat pumps are just so much more efficient, as they actually move several times the amount of energy as heat as they consume as electricity. Combined with floor heating - which gives a much larger surface area for heat dissipation than these oven stoves can ever give you - you can further lower the temperature of the water, raising efficiency even more. Floor heating is also way more comfortable as it gives an even distribution of heat throughout the house, and you don't get cold feet.

gorgoiler 5y ago
Silly question, but if a heat pump extracts warmth out of the ground, how much extraction can take place before that warmth runs out? Quantitatively, of course planet Earth has infinite warmth to give compared to what we could possibly extract but I have no idea what the numbers are actually like.
- jabl 5y ago
  Ground source heat pumps with shallow heat collection coils extract heat stored by the sun during the previous warm season. With deeper boreholes you're extracting heat from radioactivity decay. In both cases the rate at which you can extract that heat depends in the heat transfer rate in the ground around the coils/boreholes.
- Flashtoo 5y ago
  Not a silly question at all. Firstly, heat pumps do not need to extract heat from the ground, they can also extract it from the air or a body of water. The heat moved from outside to inside a building will always leak out eventually, returning to the environment. In the case of air heat pumps this means there is very little change of local air temperature over any time scale. You are right that extracting too much heat from the ground will make the ground around the exchanger too cold, which will make the process less efficient and have negative environmental effects, which means it is illegal in many places. Smaller systems like for homes are usually very shallow and will regain enough heat from the air and sun over the course of the year. Larger systems can be problematic. The common solution to this is to use the ground as a thermal battery (or install a thermal battery in the ground, using it for insulation). Then you can use your heat pump to extract heat in the cold season and in the warm season you can cool the building and move that heat back underground. This has the extra benefit of being even more efficient, since you are basically just trading heat and cold from season to season.
- stormbrew 5y ago
  I think this is a really good way to put it into perspective, because the units we use for temperature are very misleading on this front: Where I live, the outside temperature goes from -40C to +40C at the extremes (though those are rare and the 'normal maxes' are more like -30 to +30). In F that's -40 to +104F. But in kelvin, which actually measures the amount of energy in the air, that's 233K to 313K. It's not a small difference in the amount of energy, but neither number is anywhere close to zero. It's a common meme with heat pumps that they "stop working under X temp" because it's too cold, but the actual, immediately practical issue is moisture. Ice is a great insulator, so when the outside part of your heat pump is covered with ice it no longer works well. Presumably the same might be true of ground source heat pumps and frost, though I know less about that. Obviously there are other factors like the efficiency and operating range of the coolant used and such, but you hit this moisture barrier before those. There are ways around that (I installed an air source heat pump this year and it runs in reverse (ie. as an air conditioner) periodically to defrost the outside part. I've used it successfully to heat my home down to about -20 outside before it no longer spends any real time in heating mode. It wasn't cheap though, and is almost certainly not cost-effective even over a very long time period. That's not my priority though.

cheese_goddess 5y ago

I don't know if this is right. We're talking about thermodynamic heaters, like Peltier elements, correct? Those need electricity to work and the question then becomes: where does the electricity come from? Burning wood, if it can be done efficiently, and like the article says, is almost neutral in terms of carbon emissions because you're only realeasing carbon that is part of the atmospheric carbon cycle, circulating between the atmosphere and the biosphere. With a heat pump, if the electricity comes from burning fossil fuel then you're contributing to greenhouse gas emissions (all those carbon gasses are released in a much higher rate than they were stored and, more importantly, than what the environment can keep up with). If the electricity comes from renewable sources, then it's a real saving, but how probable is that right now? If you can burn wood at 80-90% efficiency, as the article claims, then that's a net gain right now. Personally I also don't like the reliance on a complicated mechanism that can't be easily made by hand. I don't like that because it means the technology is harder to adopt. I'm talking about heat pumps. By the sound of it an "oven stove" is much easier to make and maintain, if they had them back in the middle ages. So they can be used by many more people for whom the price of electricity is higher than the price of scrap wood. For a technology to make a difference it doesn't just need to be efficient, it must also be affordable and useable by everyone.

i_am_proteus 5y ago
"Heat pump" typically refers to a refrigeration cycle unit that uses a working fluid to transfer heat from a cold body to a hot body. An air conditioner uses this mechanism to heat the outside of the home (cooling the inside). Technically electricity is not required, although most of these units, in practice, use electricity, converted to mechanical energy, to power compressors. Heat pumps are much more efficient than e.g. electric baseboard heating because the energy consumed is used to move heat, rather than to generate heat. The efficiency difference drops in "very" cold climates (ambient temperatures well below freezing) and in those climates the heat pump usually is backed up by a direct heating method such as resistance electric heating, gas furnace, et cetera.
- deleted 5y ago
  [deleted]

fulafel 5y ago

To go to the opposite direction from the low tech starting point: You could have both a micro-chp setup to genetate both heat and electricity from the fuel, leaving the option to use the electricity on a heat pump or other household demands.