Nanotech free energy

[Modified]

So here's a good question. Suppose that we set this up with macroscopic bouncing balls. (Let's assume that we have truly elastic balls.) What you've just said is that the proposed device will tend to collect the balls on one side of the wall. Why doesn't that violate the second law?

My answer is that the entropy created by the heat created by the damping of the spring outweighs the entropy lost by moving the balls into a less random configuration. Which means that the working of the spring is a significant part of the operation of the machine, and has to be a significant part of the analysis.

Macroscopic balls will not speed back up due to temperature equalization.

 

[Modified]

Only if the engine is frictionless and weightless. Any engine has a minimun energy threshold.

As has been stated numerous times, if the device works you can put as many as you need in series to generate any pressure gradient you want.

 

[MRC_Hans]

One problem with this thing (which is essentially the same as with Maxwell's demon), is that while we tend to invisage atoms or molecules as little bouncing balls, that is not really what they are. For your trapdoor (or Maxwell's) to open for the right atom, it needs to "know" the atom's position, and to extract energy from it, it needs to "know" its speed. Unfortunately, it is impossible to know both at the same time.

Hans

 

[DeviousB]

One problem with this thing (which is essentially the same as with Maxwell's demon), is that while we tend to invisage atoms or molecules as little bouncing balls, that is not really what they are. For your trapdoor (or Maxwell's) to open for the right atom, it needs to "know" the atom's position, and to extract energy from it, it needs to "know" its speed. Unfortunately, it is impossible to know both at the same time.

Please tell me you are trolling?

 

[roger]

We don't measure the pressure. The valve can be an automatic control valve, which opens and closes because of the pressure difference itself.
Such valves are very commonly used and obviously completely possible.
If there is no overpressure, the valve will never open, and it can be considered as just another part of the wall. If there is an overpressure, then, again - this proves the device works.

So you are positing a valve that is so sensitively calibrated that it is perfectly set to the current entrophy setting of the room, such that it doesn't open when subjected to gas molecules moving at the normal velocity, but does open when hit by a few molecules moving somewhat faster than average. And it somehow keeps working as you increase the entropy of the room? I'm not seeing how this works.

You now have two trapdoors in sequence, basically. As others have pointed out, it doesn't work. It is not "obviously completely possible".

I say this with no ire - you are doing the same thing all the free energy people do. You are just waving your hands when a difficulty appears and say it "obviously" works. Now, I'll stipulate my objection above may be wrong. I said earlier I'm not a physicist, and I wasn't being coy. I'm not, and am not good at this stuff. I'm just having fun exercising my brain on this problem. But you can't just say things are "obvous". You have to show your work - do the math.

What is the effect of the brownian motion of the door? What is the energy loss caused by a molecule hitting the door strongly enough to open it part way, but not enough to escape? How much energy does the molecule lose to the sides of the container while it is trying to escape? Etc? You have to do the math.

Earlier you said that this is at a nanoscale, and we can't think about pressures, that this is a system that only uses single gas molecules. Now, when an objection is raised, you postulate pressure such as exists in a gas macroscale. You can't change scales when you want to get the answer you want.

 

[Modified]

Or maybe not. Because when the hatch swings open due to random vibrations, it also 'clears' an area on the inside of the box from molecules. Eg, any molecules approaching the opening have a probability of hitting the opening hatch and getting deflected. Molecules coming from the outside don't have this problem.

Using your line of thought, since the door is spring loaded, on average it should swing shut more forcefully than it swings open, because of the occurrence of spring + random closing fluctuation. Imagine holding a macro-sized spring loaded trap door in a frame and shaking it.

 

[roger]

One problem with this thing (which is essentially the same as with Maxwell's demon), is that while we tend to invisage atoms or molecules as little bouncing balls, that is not really what they are. For your trapdoor (or Maxwell's) to open for the right atom, it needs to "know" the atom's position, and to extract energy from it, it needs to "know" its speed. Unfortunately, it is impossible to know both at the same time.

Hans

Exactly. This is what I was alluding to when questioning how these doors could be so finely tuned that they are perfectly calibrated to the current average entrophy of the room. You put it much better. Either the doors are magically just perfectly set at the right tension to extract the tiny entrophy differences in the room, or, you have to measure the entrophy and calibrate the doors, which takes more energy than you can subsequently collect.

 

[Modified]

Earlier you said that this is at a nanoscale, and we can't think about pressures, that this is a system that only uses single gas molecules. Now, when an objection is raised, you postulate pressure such as exists in a gas macroscale. You can't change scales when you want to get the answer you want.

Sure you can. The hatch is nanoscale, the turbine is macroscale. If you have a tank containing a high pressure gas, you can use it to do work. If the pressure is high enough, it can do far more work than is necessary to open a valve on it. Do you doubt this?

 

[DeviousB]

Sure you can. The hatch is nanoscale, the turbine is macroscale. If you have a tank containing a high pressure gas, you can use it to do work. If the pressure is high enough, it can do far more work than is necessary to open a valve on it. Do you doubt this?

How do you generate sufficiently high pressure with a single molecule?

 

[Modified]

How do you generate sufficiently high pressure with a single molecule?

Are you referring to my earlier thought of considering the case of two chambers containing one molecule each? That was meant for conceptual purposes only. Otherwise, what do you mean by "single molecule"?

 

[roger]

Sure you can. The hatch is nanoscale, the turbine is macroscale. If you have a tank containing a high pressure gas, you can use it to do work. If the pressure is high enough, it can do far more work than is necessary to open a valve on it. Do you doubt this?

Yes, I do. The key term is 'if the pressure is high enough'. We are not dealing with macro gas pressures, but single gas molecules bouncing around. You postulate that those single gas molecules somehow have enough energy to exceed the macro gas (back)pressure at the turbine/engine. The way I see it, there's 30 million molecules on the back side of the second door (leaking through the engine). There's 3 gas molecules on the left of the second door. If so, that door ain't opening, yes?

 

[roger]

Are you referring to my earlier thought of considering the case of two chambers containing one molecule each? That was meant for conceptual purposes only. Otherwise, what do you mean by "single molecule"?

How big are these chambers? Big enough to hold a gas? Then they are happily living in the macro world, and standard statistical thermodynamics treating volumes of gas tells us we do not have a heat pump.

Too small to hold a gas? So, we are dealing with individual molecules. Macroscale gas laws no longer apply, and there can be significant distribution differences in energy, which Merko is trying to exploit, but you nol onger have the behavior of gas.

Show your math I'm guilty of not using math in my replies - this irony does not escape me. But I'm not the one claiming a violation of the 2nd law of thermodynamics. Burden of proof, and all that

 

[Modified]

Yes, I do. The key term is 'if the pressure is high enough'. We are not dealing with macro gas pressures, but single gas molecules bouncing around. You postulate that those single gas molecules somehow have enough energy to exceed the macro gas (back)pressure at the turbine/engine. The way I see it, there's 30 million molecules on the back side of the second door (leaking through the engine). There's 3 gas molecules on the left of the second door. If so, that door ain't opening, yes?

If the hatch could work, the chambers could be made as big as you like, and enough of them could be put in series to generate any pressure you like, and the whole thing could be valved off until there was a very high pressure in a very big tank.

 

[roger]

If the hatch could work

Show your work.

ETA: The diagram below represents what I think is generally being proposed here. The red is the device, with the doors small enough to be affected by brownian nose. Black are gas molecules.

Show me how the chamber builds up such a significant pressure that it escapes the chamber despite the second valve not being exquisitely calibrated to the current entrophy level of the room.

 

[Modified]

How big are these chambers? Big enough to hold a gas? Then they are happily living in the macro world, and standard statistical thermodynamics treating volumes of gas tells us we do not have a heat pump.

Too small to hold a gas? So, we are dealing with individual molecules. Macroscale gas laws no longer apply, and there can be significant distribution differences in energy, which Merko is trying to exploit, but you nolonger has the behavior of gas.

This makes no sense. The pore of an osmotic filter works on individual molecules, so would you argue that osmosis can not be used to filter water?

 

[Modified]

Show your work.

Eh? I'm not claiming such a hatch can work. I would be mighty worried if it could.

 

[RecoveringYuppy]

If the hatch could work, the chambers could be made as big as you like, and enough of them could be put in series to generate any pressure you like, and the whole thing could be valved off until there was a very high pressure in a very big tank.

This may not be relevant to your line of thought, but note that Merko has on several occasions stated the condition that the door is infrequently hit. He's repeatedly assumed that the gas at the door has to be "thin enough" and repeatedly dismissed two molecules arriving at the door at the same time as being a very rare case. If taken seriously, that assumption would put some limit on how many can be put in series.

There's also been some sloppiness of scale going on all around. Some pople have said that pressure doesn't exist at the door because the door is at too small a scale, but then there have been repeated assertions that parts of the mechanism are "temperature balancing". If there is some change of scale that allows pressure to not be a concept someplace and temperature to be a concept a few atoms away, someone needs to explain the change in scale that justifies that.

 

[roger]

Eh? I'm not claiming such a hatch can work. I would be mighty worried if it could.

Oh, sorry, I thought you were. Never mind, and apologies. I'm arguing about whether the hatch can work, not the consequences if it could.

 

[Merko]

Minor point: This is at least the second time you've hinged an argument on the gas being "thin enough".

Yes, but gasses are very thin. Collissions between gas particles can be assumed to be 'rare', in the sense that at any given time they are unlikely. So it is very unlikely that a molecule would hit the door and another molecule at the same time, for instance. These effects can only be expected to cancel similar rare coincidences.

If you're dealing with individual molecules, then you're not dealing with 'pressure'.

Read the OP. The engine is not drawn by the same scale as the hatch. Only the hatch is a nano-scale device.

I think we're assuming it's not a closed system: the purpose of the turbine is to extract energy from the system for work elsewhere.

This is sort of what I had in mind, but I guess that removing energy from the system doesn't cut it, we'd have to add energy to get away from the detailed balance. Presumably.

But the rates for those conditions are not the same. I gave 4 mechanisms for molecules to enter/exit, before, let me introduce two more:

I don't think those mechanisms are right, 2 seems wrong (and is not needed for the explanation anyhow). Let me try to correct them as per my suggestion in post 81:

1) Gas from outside transfers energy to door to open it, gas from outside enters, door closes and transfers energy to wall.
2) Gas from outside transfers energy to door to open it, rebounds outside, gas from inside exits, door closes and transfers energy to wall.
2b) Gas from outside transfers energy to door to open it, rebounds outside, gas from outside enters, door closes and transfers energy to wall.
3) Wall excites door to open it, gas from inside gets to the door, door excites escaping gas (ejecting it like the door was a baseball bat).
4) Wall excites door to open it, gas from outside gets in, door excites gas already outside (ejecting it like the door was a baseball bat).
4b) Wall excites door to open it, gas from inside gets out, door excites gas already outside (ejecting it like the door was a baseball bat).
5) Gas from outside transfers energy to door to open it, rebounds outside, door closes and transfers energy to wall.
6) Wall excites door to open it, door excites gas already outside (ejecting it like the door was a baseball bat).

So 1 and 3 are indeed reverses, so are 2 and 4, 2b and 4b, and 5 and 6. But 2, 2b, 4 and 4b are rare events (because it is unlikely that we have several molecules close at any one time). The reverse bias to the bias introduced in the OP is that of 3. The other mechanisms only confuse the matter.

My answer is that the entropy created by the heat created by the damping of the spring outweighs the entropy lost by moving the balls into a less random configuration.

No, that's not a problem. The heat in the spring is of no lower quality than any other heat in the system. The problem is that we're not moving balls into a less random configuration, because what we gain by the hatch working as a hatch, we lose by the hatch working as a baseball bat that ejects balls out of the box.

The atoms in the spring and trapdoor are jiggling randomly due to Brownian motion, which will prevent the mechanism from working in a useful manner (like we would expect macroscopically).

I don't think it prevents it from working, it just introduces a second function for the door which works contrary to the intended one.

What if you put the turbine at the top and the door at the bottom, doesn't heat rise.

Only if you have a temperature difference to begin with, this effect doesn't create it in the first place.

The trapdoor is heated by collisions with the gas and opens and closes randomly, allowing a particle through the wrong way as often as one pushes past.

Yes, although I think this is better and more intuitively stated as saying that it doesn't merely allow the particle through, it actively pushes the particle out. Because, if we say it just passively allows it, we have nothing that explains why it doesn't equally allow particles to enter.

You could have saved yourself a lot of time by just looking it up in a book.

It wouldn't have saved me any work because this would be canceled by losses in handling the information.

He's repeatedly rejected, even gotten testy about it, assertions that random openings can swamp the case he's interested in.

But actually it can't. It's the random closings that provide the 'negative' bias, not the random openings. The openings equally let gas through in either direction. My problem with these assertions was that they contained no explanation for a 'negative' bias.

So you are positing a valve that is so sensitively calibrated that it is perfectly set to the current entrophy setting of the room, such that it doesn't open when subjected to gas molecules moving at the normal velocity, but does open when hit by a few molecules moving somewhat faster than average.

Not at all. The valve is a normal, macro-scale valve (I provided you with links). Just like the engine is a normal, macro-scale engine. Again, we know valves work. I'm a mechanical engineer, trust me, they do. If you don't want to trust me, try my links.

You can't change scales when you want to get the answer you want.

Of course I can change scales. We can have a small hatch and a big valve. Or rather, millions upon millions of small hatches and one big valve.

 

[RecoveringYuppy]

This makes no sense. The pore of an osmotic filter works on individual molecules, so would you argue that osmosis can not be used to filter water?

I may be wrong but I don't think roger is saying that. I think he's covering both cases because he realizes that there's been some sloppiness about slipping between arguments that depend on a "nano" scale and others depend on a "macro" scale. I think he's pointing out that there's been a lot of convenient handwaving choosing "nano" versus "macro" when it suits the argument someone wants to make at the moment.