4 ms·

No, heat pumps don't have over 100% efficiency the same way hot water pumps that pump from municipal source don't have >100% efficiency in heating home (it uses

No, heat pumps don't have over 100% efficiency the same way hot water pumps that pump from municipal source don't have >100% efficiency in heating home (it uses hot water available from somewhere else). Heat pumps engage some other source of energy so if you want to measure efficiency you now need to include that other source into account. Since you are engaging natural source of energy you can measure how effective (not efficient in thermodynamical terms) your heat pump system is, by calculating how much energy it can transfer for energy put into the pump. But this has nothing to do with efficiency, which in case of devices used to convert one type of energy into another or moving energy from place to place is typically meant in its strict thermodynamical sense.

twobitshifter 6y ago
The efficiency calculation here measures only electrical power in vs heat energy out. Heat pumps are always listed with greater than 100% efficiency. There is no problem with the laws of thermodynamics of doing this and it’s even listed in text books with the explanation of how it is possible. The work of the heat pump is to move heat from one location to another, it does so with the byproduct of producing more heat, therefore it produces more heat energy than the electrical energy put in. You’re right that conservation of energy says that the heat in being moved did come from somewhere but that’s outside the system, and you will always find heat anywhere but absolute zero. Calculations for turbines or engines don’t make any efficiency allotments for heat already in the air, which is also necessary for them to run.
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- lmilcin 6y ago
  I guess you are mistaken about what a heat pump is. Heat pump is a closed system in which you store energy when it is hot and recover it when it is cold. https://en.wikipedia.org/wiki/Heat_pump https://en.wikipedia.org/wiki/Heat_pump Heat pump is not just the pump mechanism, but the entire system which includes mass of rock that is heat reservoir. What typically happens is you drill deep in the ground or rock and circulate air, water or some other refrigerant underground. During summer you pump hot refrigerant to heat up the mass of rock. This can be for example water that has been made hot by the sun. During winter you push water through that warm rock to recover the heat to warm your home. No, it is not thermodynamically possible to recover more than 100% of stored energy.
  - twobitshifter 6y ago
    We’re talking of home heating where the ground source heat pumps are rare. Here’s an article explaining how they work. Efficiency is 200-300% https://www.finehomebuilding.com/2020/04/08/how-efficient-are-heat-pumps-really https://www.finehomebuilding.com/2020/04/08/how-efficient-ar...

twobitshifter 6y ago

The efficiency calculation here measures only electrical power in vs heat energy out. Heat pumps are always listed with greater than 100% efficiency. There is no problem with the laws of thermodynamics of doing this and it’s even listed in text books with the explanation of how it is possible. The work of the heat pump is to move heat from one location to another, it does so with the byproduct of producing more heat, therefore it produces more heat energy than the electrical energy put in. You’re right that conservation of energy says that the heat in being moved did come from somewhere but that’s outside the system, and you will always find heat anywhere but absolute zero. Calculations for turbines or engines don’t make any efficiency allotments for heat already in the air, which is also necessary for them to run.

deleted 6y ago
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lmilcin 6y ago
I guess you are mistaken about what a heat pump is. Heat pump is a closed system in which you store energy when it is hot and recover it when it is cold. https://en.wikipedia.org/wiki/Heat_pump https://en.wikipedia.org/wiki/Heat_pump Heat pump is not just the pump mechanism, but the entire system which includes mass of rock that is heat reservoir. What typically happens is you drill deep in the ground or rock and circulate air, water or some other refrigerant underground. During summer you pump hot refrigerant to heat up the mass of rock. This can be for example water that has been made hot by the sun. During winter you push water through that warm rock to recover the heat to warm your home. No, it is not thermodynamically possible to recover more than 100% of stored energy.
- twobitshifter 6y ago
  We’re talking of home heating where the ground source heat pumps are rare. Here’s an article explaining how they work. Efficiency is 200-300% https://www.finehomebuilding.com/2020/04/08/how-efficient-are-heat-pumps-really https://www.finehomebuilding.com/2020/04/08/how-efficient-ar...