3 ms·

If we cared about making refrigerators more efficient, we would just put the heat exchanger outside or better yet underground

nextos 2y ago
AFAIK, that's how lots of restaurants keep their stock chilled, at least in my area. They have relatively noisy exchangers outside connected to their fridges that are indoors.
econ 2y ago
Imagine heat pumps 400+% efficient with 60% heat to electric conversion. https://en.m.wikipedia.org/wiki/Johnson_thermoelectric_energy_converter https://en.m.wikipedia.org/wiki/Johnson_thermoelectric_energ...
- scotty79 2y ago
  Does it work?
  - econ 2y ago
    Both work, seems funny to run in a loop.
calmbonsai 2y ago
That's actually commonly done in industrial cooling applications with rapid turnover (think dockside food storage warehouses), but it's not practical for the heat output of domestic units. Even in parts of Europe and Iceland with ready access to a common municipal heat exchange, household refrigerators don't have have enough heat output to justify the infrastructure. The typical domestic fridge just needs to "get cold once" and the remainder of its duty-cycle (aside from the rare holiday feast or party) it's just trickle-cooling.
bityard 2y ago
Depends on where you are. Where I live, it's cold seven months out of the year so keeping the resultant heat inside the house lowers the heating bill somewhat. I've always wished for a fridge that was mounted to an exterior wall. In the summer, it operates like a normal fridge but with the condenser coil outside of the house. In the winter, the compressor system turns off when the outside temp goes below a certain value and little door/shutters with fans regulate the temperature of the refrigerator either by letting in cold air from outside (if the interior needs to be colder) or from the inside (if the interior needs to be warmer to prevent food from freezing). There's probably a few good reasons why this is not actually practical but I'm tempted to try something like it in retirement.
- dgacmu 2y ago
  I've had the same desire! However, it probably doesn't pan out. An energy star fridge uses about 400kWh/year. In pittsburgh, we have 5710 cooling degree days and 736 cooling degree days. Those cooling degree days are spread across about 4 months. So we only need to dump heat from the refrigerator about 1/3 of the time: 133kWh. With an A/C CoP of 5, that means that cooling the extra load from your fridge costs you about an extra 26kWh / year, or about $5. On the heating side, it's actually better to heat the house from the fridge than to burn gas - you've basically got a heat pump system! Heat pumps are more efficient than direct heating. If you already have an efficient heat pump system this may not be as true but it probably comes out in the wash. The physical modifications to the house would have to be very cheap to make this cost-effective -- and more penetrations through the house envelope create opportunities for leaks.
- valenterry 2y ago
  Aside the complexity and standardization needed for building it, which alone will absolutely not make it worth it, you'd also have the problem of temperature fluctuations. You probably don't want your milk to be frozen right? ;-) So if you really need to push indoor air inside to avoid that, you are basically killing the efficiency. And not only that, you would push warm and comparibly humid air inside the fridge a lot. It will condense and now your fridge has to deal with a lot of condensation and probably get moldy. But good to see that I'm not the only one making these thought experiments. My personal conclusion is: eventually we will have a single refrigerant distribution system where other systems can be connected and then make use of it (similar to multi-split ACs, but extended to more devices). Then, your fridge would just be part of the system. And, just to understand: transferring heat from inside the fridge to the outside in the case that the outside is colder is so energy efficient already, there's no need at all to optimize anything. A solar panel as big as your hands will be sufficient even in winter to take care of keeping the fridge cool. That's how little energy is needed.
userbinator 2y ago
The very first household refrigerators had the condensing unit mounted outside. You can see an example in this 1920s Frigidaire training video (which is also worth watching for other reasons): https://www.youtube.com/watch?v=W-t7DqOAMME https://www.youtube.com/watch?v=W-t7DqOAMME
- ethagknight 2y ago
  Oh man I just watched that whole video. What a ride. I loved that tossing your cigs in the driveway was the correct solution, instead of dip on the front porch. Also the maid taking the service guy’s hat and coat.
  - yencabulator 2y ago
    Did you notice he used a separate entrance, for the lower-class servants? And the gauge he adjusts is labeled "retard".

nextos 2y ago

AFAIK, that's how lots of restaurants keep their stock chilled, at least in my area. They have relatively noisy exchangers outside connected to their fridges that are indoors.

econ 2y ago

Imagine heat pumps 400+% efficient with 60% heat to electric conversion. https://en.m.wikipedia.org/wiki/Johnson_thermoelectric_energy_converter https://en.m.wikipedia.org/wiki/Johnson_thermoelectric_energ...

scotty79 2y ago
Does it work?
- econ 2y ago
  Both work, seems funny to run in a loop.

calmbonsai 2y ago

That's actually commonly done in industrial cooling applications with rapid turnover (think dockside food storage warehouses), but it's not practical for the heat output of domestic units. Even in parts of Europe and Iceland with ready access to a common municipal heat exchange, household refrigerators don't have have enough heat output to justify the infrastructure. The typical domestic fridge just needs to "get cold once" and the remainder of its duty-cycle (aside from the rare holiday feast or party) it's just trickle-cooling.

bityard 2y ago

Depends on where you are. Where I live, it's cold seven months out of the year so keeping the resultant heat inside the house lowers the heating bill somewhat. I've always wished for a fridge that was mounted to an exterior wall. In the summer, it operates like a normal fridge but with the condenser coil outside of the house. In the winter, the compressor system turns off when the outside temp goes below a certain value and little door/shutters with fans regulate the temperature of the refrigerator either by letting in cold air from outside (if the interior needs to be colder) or from the inside (if the interior needs to be warmer to prevent food from freezing). There's probably a few good reasons why this is not actually practical but I'm tempted to try something like it in retirement.

dgacmu 2y ago
I've had the same desire! However, it probably doesn't pan out. An energy star fridge uses about 400kWh/year. In pittsburgh, we have 5710 cooling degree days and 736 cooling degree days. Those cooling degree days are spread across about 4 months. So we only need to dump heat from the refrigerator about 1/3 of the time: 133kWh. With an A/C CoP of 5, that means that cooling the extra load from your fridge costs you about an extra 26kWh / year, or about $5. On the heating side, it's actually better to heat the house from the fridge than to burn gas - you've basically got a heat pump system! Heat pumps are more efficient than direct heating. If you already have an efficient heat pump system this may not be as true but it probably comes out in the wash. The physical modifications to the house would have to be very cheap to make this cost-effective -- and more penetrations through the house envelope create opportunities for leaks.
valenterry 2y ago
Aside the complexity and standardization needed for building it, which alone will absolutely not make it worth it, you'd also have the problem of temperature fluctuations. You probably don't want your milk to be frozen right? ;-) So if you really need to push indoor air inside to avoid that, you are basically killing the efficiency. And not only that, you would push warm and comparibly humid air inside the fridge a lot. It will condense and now your fridge has to deal with a lot of condensation and probably get moldy. But good to see that I'm not the only one making these thought experiments. My personal conclusion is: eventually we will have a single refrigerant distribution system where other systems can be connected and then make use of it (similar to multi-split ACs, but extended to more devices). Then, your fridge would just be part of the system. And, just to understand: transferring heat from inside the fridge to the outside in the case that the outside is colder is so energy efficient already, there's no need at all to optimize anything. A solar panel as big as your hands will be sufficient even in winter to take care of keeping the fridge cool. That's how little energy is needed.

userbinator 2y ago

The very first household refrigerators had the condensing unit mounted outside. You can see an example in this 1920s Frigidaire training video (which is also worth watching for other reasons): https://www.youtube.com/watch?v=W-t7DqOAMME https://www.youtube.com/watch?v=W-t7DqOAMME

ethagknight 2y ago
Oh man I just watched that whole video. What a ride. I loved that tossing your cigs in the driveway was the correct solution, instead of dip on the front porch. Also the maid taking the service guy’s hat and coat.
- yencabulator 2y ago
  Did you notice he used a separate entrance, for the lower-class servants? And the gauge he adjusts is labeled "retard".