[drdeca]

A seebeck generator “converts a heat flux into electrical energy” (Wikipedia), it does not convert heat into electricity.

(Edit: by which I mean, it does not decrease the total amount of heat in the system.)

You need something colder on the other side.

The sun-earth system is not uniform in heat, no. The sun on average is hotter than the earth on average.

Edit: what thermodynamic symmetry are you referring to?

[cerealbad]

the mechanism that generates heat is reversible, that's how we got fossil fuels to begin with (hydrocarbon storage). if you think converting heat flux into electrical or mechanical energy doesn't reduce the total heat flux of the system then it's a perpetual motion engine? you get more energy out than you put in? think it through.

it's powered by a heat differential, you are draining the heat from the system and storing it or dissipating it under motion - reducing the overall flux - over time by cooling the hot side and heating the cool side eventually some equilibrium is reached, depending on how efficient the throughput is and how much heat you have, you then exhaust your temperature gradient and need to move somewhere hotter or colder.

one of us is very confused here. i claim "you can reduce heat locally in the earth system", and give examples: capturing and insulating it (trees, plants), converting it into other types of energy (genetically modified sea sponge/robots), as well as venting it into space through an atmospheric/orbital seebeck ring.

im not breaking any laws of thermodynamics, i am turning the planet into a refrigerator.

edit: to clarify i am claiming it's possible to move heat away from the habitable thin boundary layer by conversion: storage, mechanical use or venting.

[drdeca]

I agree that converting heat flux (or, uh, temperature gradient? I think I might actually mean temperature gradient) into electrical or mechanical energy reduces the amount of heat flux ( or temperature gradient) of the system.

Reducing the temperature gradient(s) of the system does not reduce the amount of heat in the system. When the temperature gradient decreases, that just means that there isn’t as much variation in the temperatures in the system. The temperatures become more uniform. When the temperatures are uniform, you cannot use the temperature in order to do useful work.

.. I now notice that I missed that you mentioned putting things into orbit?

I misunderstood and thought you meant putting the seebeck stuff in the ocean, as if that would cool down the oceans.

Yeah, if you pump heat into places that you can remove from earth, or have emit black body radiation more effectively, that would help.

But, Unless you are ejecting stuff away from earth, there is still a max rate you can radiate away heat at a given temperature? Oh, but, hm, if you made your thing in orbit really really hot, hm.

Is that what you were saying?

Sorry for misunderstanding what you meant about the ocean.

[cerealbad]

i did mean the ocean originally, you have heat sponges which sit near the surface and use the gradient between air flowing above the surface, the hotter temperature above, and the cooler temperature of the ocean. the sponges can use the heat to move or they can trap it like charging a battery so you transform heat into kinetic or chemical energy. it occurred to me that a third way is to build a ring that uses the heat exchange between the layers of the atmosphere and space, using the same ectothermic biological principle.

talking about the earth as a system here is a bit of a misnomer. the core up to the mantle is very hot, but that heat only escapes to the surface through lava tubes/vents because the tectonic plates are good insulators. im specifically talking about the part of the earth we care about affecting the temperature of - and you can do this by shifting the heat up, down, storing it or converting it. the atmosphere is more permissive than the hydrosphere, hadal zone or crust.

it's easier to imagine the earth as a ball and things leaving the surface as exiting the ball system. but really when we talk about the earth it's more like a layer on a ball, and if you go deep into the ocean, underground or exit the atmosphere it's all the same type of thing.

as far as i know the climate cycles are a surface feature of the planet, deep underground is more inaccessible to our technology than reaching another star system.

the term is called geosequestration.

[drdeca]

I had thought you meant sponges at the bottom of the ocean.

Not sure what you mean by storing heat.

You could store energy obtained from (the smoothing-out of) a temperature gradient, but that isn’t storing the heat, just the energy extracted as the temperature gradient goes away. It doesn’t decrease the amount of heat?

And I suppose if you have some endothermic reaction (like melting ice) you can decrease the amount of heat around, (and then if you freeze it again, you release the heat), which is sort of like storing heat, but it isn’t like you can store arbitrarily large amounts of heat this way. You would need arbitrarily large amounts of stuff to have react.

I’m still fairly sure you cannot “transform heat into kinetic or chemical energy”, but rather, you can transform a difference in temperatures, and a potential for heat to be exchanged, into kinetic or chemical or whatever energy?

In the example of that mechanism for converting a temperature gradient into electricity, suppose you had two regions with particular and different initial temperatures , which are in contact with opposite sides of the mechanism. The two regions have the same mass and are made of the same material. How do you expect the temperature of all the parts after reaching equilibrium to depend on the initial temperature? I expect that the total heat will remain the same (even though you did extract some energy as the difference in temperatures went away).

Also, pumping heat around costs energy. To move things against the tendency for temperatures to equalize, costs energy, right?

I don’t understand why the fact that earth is not homogeneous would be a reason to not call it a system?

I don’t see how the specifics of geology and such are relevant here. The question is: under what circumstances can we keep the part of a system that we care about to stay at a low temperature while waste heat is being added to the system at an arbitrarily fast rate, and the only way we have for heat to leave the system is blackbody radiation? (Assuming the system is connected/contiguous and stuff)

Now it sounds like you are suggesting that we just make the inside of the earth hotter while keeping our part cool?