Nanotech free energy

[Merko]

If the walls are solid enough to prevent leakage then how can the gas molecules lose or gain energy from them without the walls losing their integrity? How do you imagine constructing a leakproof wall one atom thick with an atom of lower molecuar weight than the gas it's containing??

I believe that is more a matter of the strength of the bonds between the molecules in the wall, than of the number of atoms thick that it is. However, like I already said - it doesn't matter one bit. We can make the walls arbitrarily thick, it doesn't change anything at all, it just makes the drawing less legible.

You can't gloss over the scale problems here. Pointing out a severe deviation from the reality of the situation shouldn't be ruining the thread.

It's no deviation because it is of no consequence. This is in fact already covered in point 3 of the OP.

If you draw it to scale it's going to become clear that the momentum of the door is going to prevent from closing fast enough to prevent molecules from escaping as molecules enter (among other things).

It doesn't have to close 'fast'. Again - molecules have no net tendency to 'escape' through a door that is sometimes open, unless the device works.

 

[Ben Tilly]

Below I'll try to list the possible reasons for failure that I've come across, and why I'm not satisfied:

1. It would not be possible to build such a small hatch and spring.

I think it would be possible, if you're a nano-technology scientist maybe you can convince me it's not possible, but this doesn't appear to be the problem.

While one could build a device that looks like this, it wouldn't work like you think it would. In particular molecules don't come up, shove, and push their way in. The molecule that imparts enough momentum to the hatch to make it open will be knocked away by that collision before the hatch actually opens. The result is that the hatch will open and close randomly, and when it is open molecules will randomly go in and out.

2. This device breaks the second law of thermodynamics and so it's impossible.

It does. But this law is more of a conjecture anyway. No one has been able to break it, so we believe that no one ever will.

Sorry, it is not a conjecture. The fluctuation theorem implies that the second law must hold for large systems and over long times.

3. Molecules would enter the box, but they would lose momentum in doing so. The gas inside the box would be cooler than on the outside, according to the ideal gas law, and no energy could be extracted in the turbine.

They would lose momentum. But they would regain this through normal heat transfer through the walls of the box.

The molecules that enter the box will generally do so by missing the hatch, so this is a red herring.

(The rest deleted because it is already clear that the device won't work.)

Cheers,
Ben

PS When you began talking about free energy from nano-devices I thought you were going to talk about extracting net energy from the Casimir effect. Which nobody has shown is impossible, even though nobody has any idea how one would go about actually doing it.

 

[RecoveringYuppy]

Point 3 of your OP neglects to mention that heat can flow out of the box through the walls just as well.

 

[RecoveringYuppy]

It doesn't have to close 'fast'. Again - molecules have no net tendency to 'escape' through a door that is sometimes open, unless the device works.

Huh? Could you think about that again and see if you really believe that?

Do you think the molecules arrange to be there only when the door is closed???

The reality of the situation is that you can't arrange for the door to only open for incoming molecules without allowing for outgoing molecules to leave.

 

[Merko]

While one could build a device that looks like this, it wouldn't work like you think it would. In particular molecules don't come up, shove, and push their way in. The molecule that imparts enough momentum to the hatch to make it open will be knocked away by that collision before the hatch actually opens. The result is that the hatch will open and close randomly, and when it is open molecules will randomly go in and out.

While the device is no doubt simplified, I'm not convinced. Of course the molecule will be deflected. But there is nothing that says it cannot be heavier than the hatch itself. It might be a gas with heavy molecules. Additionally, even if it deflects completely, it may still enter the box. For example, it might bounce at the hatch, bounce back at RecoveringYuppy's 'thin narrow passage', and bounce back again towards the opening, and enter. If the gas is thin enough, the probability of this happening will be significant, since the molecule hitting the hatch in the first place means that it is close to the opening. There is no corresponding mechanism saying that a molecule from the inside is likely to be closeby at the same time.

Sorry, it is not a conjecture. The fluctuation theorem implies that the second law must hold for large systems and over long times.

Seems to be far from waterproof, though.

The molecules that enter the box will generally do so by missing the hatch, so this is a red herring.

How could it 'miss the hatch'? Quantum tunneling effects? I don't think so..

 

[Merko]

Point 3 of your OP neglects to mention that heat can flow out of the box through the walls just as well.

Irrelevant. Normal heat transfer will make sure that the temperature inside the box equals that of the temperature outside the box. That is all that matters.

The reality of the situation is that you can't arrange for the door to only open for incoming molecules without allowing for outgoing molecules to leave.

I'm going to explain this really slowly for you.

The door may open for a number of reasons.

One reason is that a molecule can hit from the outside. If that happens, there is a molecule hitting it from the outside. That molecule may enter the box, because the hatch is now open. It is open as a causal effect of the molecule being close to the hatch.

The door may open for other reasons. It may open because of vibrations. It may open because of a molecule hitting from the outside, without entering. When the door is open, molecules can exit the box. When the door is open, molecules can enter the box. The probability of molecules entering the box, is equal to the probability of molecules exiting the box. Unless there is a higher density of molecules inside the box. Also known as a higher pressure. But if there is a higher pressure in the box, the turbine will rotate. Then we can get energy out of the device. Then the device works.

 

[RecoveringYuppy]

And let me explain something really slowly for you. When a molecule hits from the outside, there is no way your mechanism can guarantee that no molecule from the inside will exit at the same time. The spring and door system you described in your OP will open wider and longer for an energetic molecule and allow more opportunity for interior molecules to exit. On top of that there is no way to guarantee that a molecule opening the door will actually enter the device. The one way door just doesn't exist.

 

[Merko]

And let me explain something really slowly for you. When a molecule hits from the outside, there is no way your mechanism can guarantee that no molecule from the inside will exit at the same time.

So what? I don't need such a guarantee. A molecule from the inside may exit, or it may not. At the same time, additional molecules may enter, or they may not.

What makes you think there will be more molecules exiting, than entering, in this way?

The spring and door system you described in your OP will open wider and longer for an energetic molecule and allow more opportunity for interior molecules to exit.

And more opportunity for exterior molecules to enter.

On top of that there is no way to guarantee that a molecule opening the door will actually enter the device. The one way door just doesn't exist.

We don't need a guarantee. We only need a probability greater than zero. It doesn't have to be a one-way door. The OP makes this quite clear. All we need is that the door is biased.

 

[Dilb]

PS When you began talking about free energy from nano-devices I thought you were going to talk about extracting net energy from the Casimir effect. Which nobody has shown is impossible, even though nobody has any idea how one would go about actually doing it.

I read a scientific paper a few years ago that illustrated a device to extract energy via the Casimir effect. The device is perfectly consistent with thermodynamics, as the Casimir effect is just a peculiar potential that (measurably) occurs when metal plates are very close together. It's like getting energy from dropping rocks down a hill: sure it's possible, and it's perfectly good available energy, but it's extremely non-renewable.

 

[AZAtheist]

appears to me that the flap on the input side of the device is not that dissimilar in function to the turbine on the back side. Tall buildings in the past had revolving doors for entry to keep the building from acting like a chimney. Replace the flappy door with a revolving door to do the same function and you'll quickly see that you have a box with a turbine on each end.

 

[Dilb]

After running a simulation (because physics is hard), I'm fairly certain this setup would work, for an ideal classical situation. Why this isn't possible in real life seems really hard to understand, but seems to involve the fact that a one-way valve for atoms isn't possible. This paper seems to address the problem for actual, or at least possible, devices.

 

[Schneibster]

This is interesting, but far from being bothered by your simplifications, this goes beyond my very basic understanding of QM theory. Since you seem to be better informed, I could ask you an off-topic question: you don't happen to have come across any book dealing with QM from a predominantly experimental point of view? Eg something focusing on the various experimental findings that show interesting QM properties, rather than the maths. I'm must admit I'm a bit skeptic towards the heavily math-based theories, perhaps partly because I find it hard to grasp them intuitively, but also because a pretty formula may appear to satisfy occam's razor in ways that I find dubious. But of course, when it predicts empirical observations, it is another matter.

There is actually a running thread on learning QM in this forum where I did some recommendations; you might, I think, find Vincent Icke's The Force of Symmetry very interesting, and quite valuable if you know your way around Newtonian and Galilean physics pretty well.

 

[Schneibster]

I'd love to learn more about that... toss me a bone/link/reference?

You seem facile with Wikipedia- there was a pretty good article in it on the FT about six months ago. YMMV if someone has hacked it.

A google of the FT might help some. If you don't get anywhere either way, lemme know and I'll see what I can dig up.

The most interesting things about the FT are:
1. You can derive the 2LOT from it.
2. It implies that as the system you're considering, and the components of that system, get smaller, anti-entropic behavior becomes more and more likely, until at the quantum scale, anti-entropic behavior is as likely as entropic.
3. One of the most important pre-requisites for the FT to be true is that QM upon which it is based must be truly time-reversal symmetric for the particles in question. There is some question on this due both to the lack of time-reversal symmetry in the weak interactions and the time-reversal symmetry violations in the decays of the kaon and beon, but these don't appear (according to some physicists I have discussed this with, and my own take on it as well) to affect the majority up-n-down-quark-n-electron-n-photon universe we do most of our screwing around in. But be aware that this may eventually sink it.
4. Boltzmann originally did his statistical analysis of thermodynamics based on Maxwell-Boltzmann statistics, which don't apply to the fermions and bosons we really encounter, because the Maxwell-Boltzmann statistics don't take the laws of Spin and Statistics into account; but the FT uses Fermi-Dirac and Bose-Einstein statistics, so it is a better description of what's going on than Boltzmann's statistics are.

That should give you some food for thought.

 

[Schneibster]

Ben, my intuition says you're right, but damn it, I can't see a way to PROVE it yet. Still thinking about it. Be patient, Merko.

Regarding the Casimir effect, I think there are practical limitations- mainly that the most motion you can get out of it is like, three nano-inches; you might get energy if it was fifty miles wide, but where the hell you gonna PUT the damn thing? Heh, I'm spoofing, but you get the idea.

 

[andyandy]

in an enclosed space (ie the box) with an increasing number of particles wouldn't you have more and more collisions with the limiting wall and thus lose more and more energy here through transfer?

 

[MortFurd]

Ben, my intuition says you're right, but damn it, I can't see a way to PROVE it yet. Still thinking about it. Be patient, Merko.

Regarding the Casimir effect, I think there are practical limitations- mainly that the most motion you can get out of it is like, three nano-inches; you might get energy if it was fifty miles wide, but where the hell you gonna PUT the damn thing? Heh, I'm spoofing, but you get the idea.

Worse than that:
How are you going to maintain that kind of physical accuracy over 50miles?

(Steps up to the counter at the local "Impossible materials dealer")
"Hiya. I'd like two perfectly rigid metal plates fifty miles long, each perfectly flat to within less than three nano inches."

"Right. Would that be the ones with the coefficient of temperature expansion of zero?"

"Ya. Like that."

"Hang on a minute while wrap that for you. Anything else?"

"Yeah, while I'm here I could use some zero friction lubricant. Oh, and one of Maxwell's demons."

"OK. Careful not to spill that stuff. Keeping the lid on the lube is kind of tough. Where should the plates be delivered?"

"Oh, don't bother. I'll just toss 'em in my back pack. They're figments of my imagination anyway, so they don't weigh much."

 

[RecoveringYuppy]

The door won't be biased. During the time it's open molecules will flow through the opening on the left just as they do the opening through the turbine.

BTW How many atoms do you think would go in to the construction of the door? You say the opening on the left is big enough for one molecule. Do you think you can arrange for the door to be exactly the same size with no overlap of the adjacent walls? If you have the door overlapping the walls a bit then you've got a situation where the door can only have one molecule hitting it from the outside yet multiple molecules hitting it from the interior. You start to wonder if the door is ever going to open at all.

 

[Darat]

It was mentioned before but what "powers" the 'spring'?

 

[roger]

Merko, could you expand on how that turbine works a bit better?

Here's why. You don't seem to by analyzing the exhaust. If you are exhausting into the room where you are gathering the molecules from, it should be getting hit very strongly with millions of molecules. Now, when a single atom strikes the turbine from the other side, it's not going to be able to do anything.

If when you inserted this device into the room it had a hard vacuum in it, then you have a tiny temperature differential (lots of molecules moving energetically in the room, none, or very few moving inside your device). Your device may work for a few nanoseconds until you reach temperature equillibrium with the outside, but after that, the door will recieve more pressure from the inside (all those molecules plus the spring force) than the outside, and remain forever shut. The forces on the turbine will be in equillibrium, and it will not turn. But even here, won't all the work end up being done on the spring, where you will lose all the energy to heat losses?

On the other hand, if you are exhausting into vacuum, which you seem to be assuming, then you have introduced a temperature differential. You will get energy, but in exactly the same way you get energy from a water dam or a windmill.

I think the problem here is analyzing the system in isolation. You have to sum the energy over the entire system. The other side of the exhaust is part of the system.


ETA: the question about losing the heat to the spring is probably the most telling one. Why not just simplify this device to the front part - a door with a narrow opening, and replace the spring with an energy gathering device. No box, no turbine. Stick that in a room, and you'll see immediately that it won't work. The door will be hit equally from both sides. The enclosed box and turbine obsfucates this point, because we all forgot to analyze the forces on the turbine. Show me how a molecule has the ability to move all the way from the door, through the turbine, and out back into the room, despite losing energy to the door, spring, walls, and turbine.

 

[roger]

Water wheel

Here is how I see the device in a classical world. Envision a tub of water. You have a closed cylinder. On one side of the cylinder you have a door with a spring, and on the other you have a turbine. Impose a vacuum inside of it. Stick it in the vat of water. Will it run? If so, for how long?