Moreno

Still, there is principal theoretical difference between entropy decrease and entropy unchanged. This is what ideal Carnot engine does: https://physics.stackexchange.com/questions/214346/how-is-the-efficiency-of-a-heat-engine-related-to-the-entropy-produced-during-th

I don't know. I think demon would decrease entropy if he increase temperature/pressure differences in comparison to some initial state. If he just starts from some initial non-equilibrium state (created not by him) and keeps this state unchanged, where do you see entropy decrease?

But that's a point. The demon doesn't decrease entropy. It just prevents it grow, so basically keeps it at the same level.

I've already said. It may use some part of energy produced by the turbine.

I think word "energy" may be appropriate here as well, if we are trying to describe heat exchange between gas molecules and those atoms/molecules the turbine made of at the atomic level. It may draw part of the turbine's energy.

To a larger extent Earth exist in thermodynamic equilibrium with Sun as it radiates as much energy into space as it receives from Sun. We may ignore here the space rays or similar phenomena. But let imagine for simplicity that entire Earth is surrounded from space with shield completely restricting for any radiation to come in and out. And all Earth is divided in two containers separated by molecular membrane with a demon who allows fast or slow molecules to come from one container to another, sorting them at will. All humans may live in one of part of the container together with their factories, cars, houses and entire civilization. Let say another part of container is completely uninhabitable. The air pressure in inhabitable part of container is constant and is always 10 times higher than in uninhabitable part. Air is allowed to travel from one part of container to another part through a turbine and this huge turbine powers entire human civilization. Demon allows molecules return to high pressure container by opening molecular membranes when needed. In this way the constant air pressure is supported in both part of containers and entropy never changes. Entropy would diminish if pressure difference between both containers grow larger at some point, but this is not a case as demon constantly preserves the same amount of molecules in each particular part of container. As entropy of entire system never changes, I assume will neither change its ability to perform a useful work. So, factories, cars, computers, trains will keep going forever and ever. Entropy growth = amount of useful work diminishes. Entropy never change = no useful degradation. Turbine is not going to transfer all the energy at any given point. Turbines work smoothly.

"For Earth think still some remnant heat of formation. For smaller planets, heat of formation may have been dissipated as quickly as planet formed." https://www.tcd.ie/Physics/people/Peter.Gallagher/lectures/PY4A03/pdfs/PY4A03_lecture10n11_ineriors.ppt.pdf One more argument against Pluto preserved lot of formational heat.

Why do you think it suppose to transfer energy outside the system in order to do the work? Principally we can imaging that closed system is entire Earth, and we all live inside one part of container. And huge, huge turbine located within this closed system and powers all the power grids on Earth. Heat energy has nowhere to go outside the system, so it totally conserved within it.

I've read claims that heat pumps which are based on adsorption process are more efficient. Is it true? If yes, does it apply to any outside temperatures?

To rotate and perform useful work.

Not necessarily, if the turbine is the part of the closed system. Then total heat energy that gas atoms transfer to turbine will be equal to total energy the turbine transfers back to the gas atoms.

In any case Uranium is non replenishable. And will start to get scarce soon.

It is assumed that classical Maxwell's demon suppose to work in cycles. So, it starts from equilibrium system, then make it non equilibrium by sorting fast and slow atoms, and reduces its entropy in this way, then system performs some useful work and when it does entropy increases and system returns to equilibrium state again. Then demon starts his work again... The common objection against it is that: "entropy of the system cannot spontaneously decrease". But let imagine that demon never decreases entropy and entropy constantly stays at the same level. And the system never comes to equilibrium. For example, let imagine we have a container separated by atomic membrane through which individual atoms can pass and demon can sort fast and slow atoms. Gas pressure in the part A of the container is initially 10 times higher than in the part B. Gas atoms are allowed to pass prom part A to part B through a rotating turbine and perform a useful work. But once one additional atom passes from part A to part B, the demon opens a membrane and allows a fast atom from container B return to container A. So, in this way pressure and temperature in each individual part of container never changes. Possibly, in this way we are going to obtain an ideally reversible process.

Do they have moving parts? If not, then where noise and vibration come from? How their efficiencies and power is compared to electrical heat pumps? If they are less efficient, then why? What can be done to increase heat pump efficiencies radically at lower temperatures? For example, could use of propane instead of Freon be helpful?

What about neutrino radiation and heat flux mismatch? The mainstream hypothesis suggest otherwise: https://earthscience.stackexchange.com/questions/4798/what-percent-of-the-earths-core-is-uranium I will look for more reliable link if you want.

Why do you expect I suppose to argue with you? Do you think I'm an expert to prove if you are right or wrong? You expressed your opinion so I'm OK with this. If other users don't then they can contribute. The new measurements suggest radioactive decay provides more than half of Earth's total heat, estimated at roughly 44 terawatts based on temperatures found at the bottom of deep boreholes into the planet's crust. The rest is leftover from Earth's formation or other causes yet unknown, according to the scientists involved. https://blogs.scientificamerican.com/observations/nuclear-fission-confirmed-as-source-of-more-than-half-of-earths-heat/# Well, you believe, it seems, that all heat produced inside of Pluto is caused by radioactivity. Then without radioactivity temperature inside of Pluto would be equal to that on the surface. It would loose any primordial heat long age. So, what I meant is that it suppose to bring temperature of entire planet from -230 to 0 if we assume that radioactive elements are distributed more or less evenly. And create a subsurface ocean. Even if the core is 2/3 of entire Pluto by mass, it doesn't make much difference as entire planet is tiny. Also, 2/3 by mass is even much less than that by volume, taking density in account. Presently, the geologists believe that radioactive decay takes places in Earth mantle and crust, not much (if any) in the core. Do you need any links for this? I don't know if the same thing is applicable to Pluto, but still you argument have to be taken cautiously.

"This" is still here. Researchers claim that radioactivity can explain only 55-75% of geothermal heat. Are they wrong? If not then what about the rest?

Radioactivity is outstanding for pollution and safety problem, so people can only hope that by token they will succeed much more next time.

The same thing people would say about radioactivity 150 years ago.

Interesting ideas. Still there is no energy source discovered which would be cheap, safe, powerful and available everywhere. I think the quest for such an energy source will continue in this millennia. Fusion can be regarded as an almost inexhaustible, but is not safe enough at modern stage and is too alien to anything that can be encountered in Earth conditions. I think it would be nice to discover some new energy source which can happen naturally in the bowels of the planets and moons. Regarding the farther exploration I think, it would be interesting to send a probe to Enceladus which would melt down the ice and make thorough exploration of the internal ocean, its chemical composition and make detailed 3-d map of the energy sources, to understand where energy come from. Also some new measurements and calculations on tidal forces in Saturn systems wouldn't be spare.

Maybe it wouldn't be able to reach absolute zero due to Heisenberg uncertainty principle. There always going to be some quantum fluctuations in any body and maybe it will continue to radiate because of that.

Can we harness the very expansion of Universe? For example if we capture some light from stars that became violet shifted relative to us, doesn't it mean we harness it?

We are still not in the state of "heat death". Possibly it means some forces in Universe reverse entropy.

Not necessarily if we regard entire universe as a system. If this is infinite, we can extract something from it infinitely.

A mistyping. Farther reads 3500 meters. Possibly. I remember a decades ago some researchers were in hunt of the "cold fusion" and some of them still are.