I think I've found Maxwell's Demon, however the demon is quite large...

[broli]

1 year later and I still think this concept has merit. I just remembered it and wondered why it died off. It would be very easy to confirm.

You would be right about choosing a bad thermal conductor as the container. PVC in itself is a bad thermal conductor but some companies actually make tube shaped polyurethane like seen here:

http://www.coolag.co.za/products/

This could be inserted in the PVC pipe to get the thermal conductivity further down.

But I do have one question relating to the concept. You say that without buoyancy the fluid in the container will take the temperature of the bottom coil. And this is where it gets a bit confusing for me. So let's say the temperature is 20°C uniformly distributed. Now you introduce buoyancy, wouldn't the temperature become lower than 20°C at the bottom and higher at the top? Because the total sum has to become 20°C? In your explanation you prorpose that the lower temperature would match the environment.
Of course if this is true it wouldn't change much in fact I think it would aid the concept more.

[broli]

I also forgot to mention the test. You don't need a whole array, just one long isolated tube would do. You keep one temperature probe at the top and one at the bottom, if the latter goes from bottom to top it has to preferably be non metal or it might act as a short circuit for the gradient and defeat the purpose. This experiment would show the feasibility and give some numbers on how much temperature difference arises using x m height. Luckily buoyancy only needs hight so the tube doesn't have to be large in diameter but I think using less volume would make the gradient appear quicker but it would also be easier to disrupt.
This is what they would call a proof of concept.

[lumen]

I also forgot to mention the test. You don't need a whole array, just one long isolated tube would do. You keep one temperature probe at the top and one at the bottom, if the latter goes from bottom to top it has to preferably be non metal or it might act as a short circuit for the gradient and defeat the purpose. This experiment would show the feasibility and give some numbers on how much temperature difference arises using x m height. Luckily buoyancy only needs hight so the tube doesn't have to be large in diameter but I think using less volume would make the gradient appear quicker but it would also be easier to disrupt.
This is what they would call a proof of concept.

I did build such a test device!

I placed a 3" diameter pvc pipe inside a 4" diameter pipe and used a vacuum pump to evacuate the cavity between the tubes to work as an insulator.

I had installed temperature probes in each end (digital cooking thermometers) to see the results.

After leaving it in the shed, standing on end for a few days, the probes checked exactly the same temperature.

I thought it was working at one point when the upper was a few degrees higher, but it was the result of an increase in the ambient temperature near the ceiling.

It does seem the results should have been better, but I am convinced that you would probably get more energy by raising a large weight  when the moon is overhead, and extracting the energy when the moon is on the other side of the earth.

[broli]

I did build such a test device!

I placed a 3" diameter pvc pipe inside a 4" diameter pipe and used a vacuum pump to evacuate the cavity between the tubes to work as an insulator.

I had installed temperature probes in each end (digital cooking thermometers) to see the results.

After leaving it in the shed, standing on end for a few days, the probes checked exactly the same temperature.

I thought it was working at one point when the upper was a few degrees higher, but it was the result of an increase in the ambient temperature near the ceiling.

It does seem the results should have been better, but I am convinced that you would probably get more energy by raising a large weight  when the moon is overhead, and extracting the energy when the moon is on the other side of the earth.

Interesting but you didn't mention the two most important parameters. What was the height of the tube and what fluid or gas did you use? Also how could the temperature probe be affected by the ceiling if it was supposed to be inside the insulated tube? And finally, what was the accuracy of your thermometers?

And don't be so hasty with debunking it  . Only a fool would conclude final results after one test.

[Nabo00o]

Hey Broli, yeah it has been a while, actually also a while since I have been on the forum.

First I think something like the insulator you proposed would work very well, as long as it is thin enough to allow some water or other fluid left inside.

Second, here is how I see it. If there were no buoyancy, then the temperature should have remained at whatever it was to begin with, and probably equally distributed all inside the volume.
When we then introduce heat exchangers like the coils, the temperature inside and outside should equal with enough time, so no gradients there.

Okey, to the confusion. With buoyancy, but 'without' the heat exchanger, the bottom would be colder then the otherwise average inside temperature, and this would also keep the inside temperature as a total conserved. But since we have a heat exchanger at the bottom, it will fight that change and keep the bottom at the outside temperature, given its heat conductive capacity is higher than the inside buoyancy forced temperature separation, which it probably is.....

So the bottom will stay at the outside temperature, but there should at the same time be created a gradient, and the top of that gradient must be at some value higher than the original temperature, because of the methods here used. At least I strongly believe so.


And from here it is a simple task of connecting the top high temperature of one tube to the bottom low temperature of the next tube, thus helping the heat to flow, and kinda works like connecting two or more batteries in series. If we want this heat to be transferred at a fast rate, something called a heat pipe would aid this process tremendously, but it is probably not cheap at a bigger scale than the one found in my laptop's cpu.

Also...... I have had some new ideas about this concept, partially inspired by the vortex tube.
Since gravity decides the power of buoyancy, what about replacing that force with centrifugal force, which can be much much higher....

Julian