We expect heat to flow from hot to cold, devices that deviate from this are thermodynamically unlikely, which is another way of saying that they require a low entropy source. (As you said.) Low entropy = thermodynamically unlikely. This means that heat pumps are extremely non-random. So any system that looks like its random (a hot cup of tea) is going to be a very bad candidate. Similarly I think that things like weather phenomena are a bad place to look.
Living creatures can do thermodynamically unlikely things. As an example lots of (all?) individual cells move various chemicals (like salt) against the density gradients (so they move salt from a place of low concentration to a place of high salt concentration). This is Active Transport. This is just as thermodynamically unlikely as a heat pump, but its a “salt pump” not a “heat pump” so its not exactly right.
“In the spring ants are observed to create clusters on the mound surface as they bask in the sun. Their bodies contain a substantial amount of water which has high thermal capacity making ant bodies an ideal medium for heat transfer. After getting hot enough the ants move inside the nest where the accumulated heat is released.”
If we suppose that, as a result of this, the inside of the ant’s nest ends up warmer than the air outside then this I think possibly counts. Its a heat pump where the working fluid is living ants. The cold ones leave to bask in the sun, then return hot.
Its borderline because there is cheating going on, in that the sun is much hotter than the inside of the ant’s nest (I assume), and they are using the sun to heat themselves up. Ideally we need ants that carry around little compressible air sacks they can inflate inside and deflate outside, so that they can unambiguously take heat from the cool air outside to deposit in the hot air inside their nest.
We expect heat to flow from hot to cold, devices that deviate from this are thermodynamically unlikely, which is another way of saying that they require a low entropy source. (As you said.) Low entropy = thermodynamically unlikely. This means that heat pumps are extremely non-random. So any system that looks like its random (a hot cup of tea) is going to be a very bad candidate. Similarly I think that things like weather phenomena are a bad place to look.
Living creatures can do thermodynamically unlikely things. As an example lots of (all?) individual cells move various chemicals (like salt) against the density gradients (so they move salt from a place of low concentration to a place of high salt concentration). This is Active Transport. This is just as thermodynamically unlikely as a heat pump, but its a “salt pump” not a “heat pump” so its not exactly right.
My feeling is that an actual “heat pump” (with heat, not salt) must occur in some organisms, and I think I have found a borderline example at this link (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3962001/#:~:text=After%20getting%20hot%20enough%20the,the%20nest%20surface%2015%2C%2046.) :
“In the spring ants are observed to create clusters on the mound surface as they bask in the sun. Their bodies contain a substantial amount of water which has high thermal capacity making ant bodies an ideal medium for heat transfer. After getting hot enough the ants move inside the nest where the accumulated heat is released.”
If we suppose that, as a result of this, the inside of the ant’s nest ends up warmer than the air outside then this I think possibly counts. Its a heat pump where the working fluid is living ants. The cold ones leave to bask in the sun, then return hot.
Its borderline because there is cheating going on, in that the sun is much hotter than the inside of the ant’s nest (I assume), and they are using the sun to heat themselves up. Ideally we need ants that carry around little compressible air sacks they can inflate inside and deflate outside, so that they can unambiguously take heat from the cool air outside to deposit in the hot air inside their nest.