Nanotech free energy

[Merko]

I have been pondering the following design for a free-energy device using nano-technology for at least ten years. I still didn't get a satisfying explanation for why it won't work. Since I think there are a lot of people interested in this subject on this forum, I thought I'd give it a try here.
It is basically a version of Maxwell's Demon, but without any demon. Just to be clear: I don't think this would work. I want to know why it wouldn't.

To the left, we have a molecule-sized hatch. The hole in the box is barely large enough for one single gas molecule to pass through. As we can see, the hatch can only open inwards. When molecules from the outside hit the hatch, they will sometimes have enough momentum to swing it open and enter the box. When molecules inside the box hit the hatch, this never happens.
So, we end up with more and more gas inside the box, eg an overpressure. On the right, we have a turbine (different scale of course) that turns this overpressure into electricity and solves the world's energy problems.

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.

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.

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.

4. But the molecules could go out of the turbine, then enter the box again, going around in circles creating more and more energy - this also breaks the first law of thermodynamics, which is clearly impossible.

The molecules would lose momentum in the turbine, and if we take the electricity out of the system, they will eventually cool down until they can't push through the hatch anymore.

5. The hatch will only let through a few molecules - this can't be turned into useful energy on the macroscopic level, because they are so few.

If it works with one hatch, we can make a box will millions upon millions of parallel hatches, and eventually it can drive a real turbine.

6. On this nano-sized scale, vibrations in the box would cause the hatch to flip open every now and then, allowing molecules to pass from either side. If there is an overpressure in the box, more molecules would then go out of the box, than inside it, equalising the pressure.

This argument assumes that there is an overpressure. If there is, we should indeed expect an equilibrium pressure to occur when this effect equals the effect of the hatch opening from hits by outside molecules. But for the equalising effect to occur at all, there has to be an overpressure in the first place.

7. There might be an equilibrium overpressure, but it will be so small that it could not be turned into useful energy on the macroscopic level.

If there is an overpressure, then we can, in theory, put many walls with hatches in serial, until this overpressure is high enough to drive a real turbine.


So.. where am I going wrong? In one of the attempts above, or is there something else that I just haven't thought about?

 

[RecoveringYuppy]

What stops molecules from leaving when the hatch is opened from the outside?

 

[roger]

I'm no physicist, but isn't what you doing is extracting heat from the environment? It's 'free energy' in the exact same way a solar panel is 'free energy'. You are relying on some external element to provide heat (molecules moving around). Factor that external element into your equation, and it is no longer free. How did those molecules get moving fast anyway? The heat of the sun, waste heat from industrial processes, chemical reactions, many different things. If you sum the energy inputs with the energy outputs and losses, the total will be zero.

This will work in exactly the same way putting a water wheel in a stream will work. Is it 'free' energy? Free as in beer, yes. Free as in breaking the second law of thermodyamics, no, I don't see how.

Did I understand your design correctly?

 

[DanishDynamite]

I have been pondering the following design for a free-energy device using nano-technology for at least ten years. I still didn't get a satisfying explanation for why it won't work. Since I think there are a lot of people interested in this subject on this forum, I thought I'd give it a try here.
It is basically a version of Maxwell's Demon, but without any demon. Just to be clear: I don't think this would work. I want to know why it wouldn't.

[qimg]http://ronnblom.net/ntfed/freeenergydevice.gif[/qimg]

To the left, we have a molecule-sized hatch. The hole in the box is barely large enough for one single gas molecule to pass through. As we can see, the hatch can only open inwards. When molecules from the outside hit the hatch, they will sometimes have enough momentum to swing it open and enter the box. When molecules inside the box hit the hatch, this never happens.
So, we end up with more and more gas inside the box, eg an overpressure. On the right, we have a turbine (different scale of course) that turns this overpressure into electricity and solves the world's energy problems.

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.

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.

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.

Interesting thought-experiment, Merko.

My layman explanation for why this wouldn't work is the following:

As the pressure increases in the little chamber above compared to the pressure on the other side, any gas molecules who try to enter the chamber would need to overcome a lot more than the friction in the doorway. They would need to overcome the pressure of the molecules already in the chamber. If they had warmed to the same temperature as the molecules not in the chamber, that door would be sealed shut.

 

[Solitaire]

So.. where am I going wrong? In one of the attempts above, or is there something else that I just haven't thought about?

The spring. If it's weak enough to open then random vibrations of thermal energy will cause it to open randomly. If it's strong enought to prevent thermal vibrations from moving it then the molecules will not have sufficient energy to enter the box. It may be possible to overcome the second law of thermodynamics by exploring quantum mechanics, but it's equally likely that it may not be possible.

 

[Walter Wayne]

What roger said.

You don't have a closed system. A molecule comes in one side, with an associatic kinetic energy, and then leaves the other, with a different kinetic energy. The difference in kinetic energy for that molecule is going to be the amount required to open the hatch and then spin the opposite turbine (overcoming friction in the process).

The energy from the turbine is going to the energy lost by the molecule going through, subtract friction effects. The molecule will lose more energy than you get out of the turbine. If you used the power extracted to boost the molecules energy back up you would still be at a net loss, and the system would eventually run down.

Walt

 

[Schneibster]

I am still thinking about it, but it is possible that it might work. The thing is, you see, recently someone managed to derive the 2LOT from a deeper theorem (note carefully: this is a theorem of mathematics, not a theory of science; it is therefore susceptible of proof, and has been proven) called the Fluctuation Theorem, or FT. However, the FT says that there is a region of sizes, the macroscopic region, in which the 2LOT is strictly obeyed; another region, the quantum region, where it is not; and a border region between them where the 2LOT can be violated for brief periods over small regions. This is a drastic and vast oversimplification of the implications of the FT; I am well aware of it; the situation is far more complex than to state baldly that the second law of thermodynamics is maximally violated by QM. So please don't come tell me I'm "wrong," because I am well aware of this oversimplification. It is, nevertheless, possible to state that there are a large variety of situations in QM in which the strict 2LOT is not obeyed, and that major characteristics of the world around us would be very different from what we see if it were obeyed in this fashion.

The FT has also been proven in a real-world experiment; physicists were able to show that over small spatial regions, for short times, in a liquid stimulated by lasers, small numbers of molecules behaved in anti-entropic fashion. So we not only can prove it mathematically, but when we go looking for the physical behavior that the math implies, there it is.

Now, I don't know that the exact (or a more correct approximate, but congruent) device you showed will work; and I am by no means convinced that there is either a way to apply it that will produce macroscopic energy, or a way to implement it, or finally that even if it is implemented it will work. But proving it one way or the other is going to take me a bit. My experience and pessimism tell me that it will not; however, I have been surprised before this, and I have seen some things suggested that sounded very much like this that I was told some pretty senior and experienced people could not find a problem with. So hang loose before you lean too far one way or the other.

 

[Solitaire]

I swear it looks like Feynman's old Racket.

P.S. Well, it's time for me to fire the Quantum Afterburner and head on home.

Chao!

 

[Merko]

What stops molecules from leaving when the hatch is opened from the outside?

Nothing, but the spring will close it again. The chance that another molecule will appear from the inside at the exact same moment, preventing the door from closing, is less than 100%. In addition, if the device doesn't work and there is equal pressure on the outside, the chance of a second molecule following in the heels of the first, from the outside, is equal to that of a molecule coming from the inside. Except the chance of a collision is reduced.

I'm no physicist, but isn't what you doing is extracting heat from the environment?

You understand the design correctly. However, this is assumed to be impossible. The second law of thermodynamics implies that it is not possible to get high quality energy, such as electricity, from the heat in a room with no temperature differences. This device violates that.

As the pressure increases in the little chamber above compared to the pressure on the other side, any gas molecules who try to enter the chamber would need to overcome a lot more than the friction in the doorway. They would need to overcome the pressure of the molecules already in the chamber. If they had warmed to the same temperature as the molecules not in the chamber, that door would be sealed shut.

That would happen with a macro-scale hatch. However, the 'pressure' that keeps such a hatch shut, is only a statistical property. It corresponds to a huge number of molecules constantly battering the inside of the hatch - a huger number than the molecules constantly battering the outside of it. This is a tiny hatch, and, typically, no molecules will batter it, from either side. Pressure just doesn't exist on this scale.

The spring. If it's weak enough to open then random vibrations of thermal energy will cause it to open randomly.

It will open randomly. But that is not a problem, because it will not be open all of the time. And on those moments where it is closed, it will bias the flow of molecules in favour of molecules entering it. This can be countered, as in argument 6 above, but that argument assumes that the device works.

The FT has also been proven in a real-world experiment; physicists were able to show that over small spatial regions, for short times, in a liquid stimulated by lasers, small numbers of molecules behaved in anti-entropic fashion.

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.

 

[Merko]

I swear it looks like Feynman's old Racket.

Yes, it's a very similar device. However, in that example, there is a plausible theory claiming that the pawl will force the wheel 'backwards' when it isn't at the base of a tooth, and so cancel the positive movement (because the teeth, in order to work, need to have a slope forcing such movement).

I see no similar possibility with my device, but maybe I'm just blind.

 

[RecoveringYuppy]

Nothing, but the spring will close it again. The chance that another molecule will appear from the inside at the exact same moment, preventing the door from closing, is less than 100%.

Exact? How are you going to arrange for the door to close instantly and "exactly"?

The passageways through the turbine and the door have exactly the same pressure differential. The only difference is the amount of time they are open. If the door is open 10% of the time the flow in both directions will be 10% of the flow in both directions through the turbine.

If you are imagining that the door can be adjusted to only open when a molecule is approaching and that the senstivity of the spring can be adjusted fast enough to shut the door with the minimal force and time for that particular molecule then you aren't accounting for the energy of that mechanism.

BTW there would also be mechanical losses in the spring.

 

[DavidS]

It is basically a version of Maxwell's Demon, but without any demon.

The gate is the demon. What it lacks are the kewl horns and cloven feet I'm led to believe their union requires.

I'm no physicist, but isn't what you doing is extracting heat from the environment? <snip> Free as in breaking the second law of thermodyamics, no, I don't see how.

It would break the second law because that's precisely what it forbids.

This will work in exactly the same way putting a water wheel in a stream will work.

No, at least only the turbine and then not until the box interior gets charged with gas with more energy (kinetic, potential, enthalpic... which depends on what you mean by "water wheel", but that doesn't really matter) than that on the exterior. That's the question... whether the inlet gate achieves that end, or why not?

You don't have a closed system.

You do if you put a generator on the turbine shaft and put the whole shebang into a bigger box with inductive coupling to the outside. Voila, system closed, with the added benefit of preventing bothersome contamination of your working fluid. Wrap it all up in an insulating blanket of expanded unobtanium (Styrofoam on Economy models) and it can be adiabatic to boot; that would limit energy output to the point of internal freezeup, but with a thermally-coupled compartment inside the insulation it should make a great keg cooler. For free energy production it would be better to set an uninsulated one in a large heat sink, like tropical seawater -- which conveniently enough is ready to hand where I'd most like to be with a cold keg.

That's not the point, though; we should be able to do better than that.

I am still thinking about it, but it is possible that it might work.
<snip>
But proving it one way or the other is going to take me a bit. My experience and pessimism tell me that it will not; however, I have been surprised before this, and I have seen some things suggested that sounded very much like this that I was told some pretty senior and experienced people could not find a problem with. So hang loose before you lean too far one way or the other.[

(bolding mine)

Yeah, what he said... I'm actually surprised and frustrated that I seem to be able to out-Devil's-advocate all my rapid refutations on this one; I give up for tonight. I doubt the common man appreciates how painful that can be for an engineer. Well, maybe you do.. we're generally a pretty thick-skinned (skulled?) lot.

The thing is, you see, recently someone managed to derive the 2LOT from a deeper theorem (note carefully: this is a theorem of mathematics, not a theory of science; it is therefore susceptible of proof, and has been proven)
<snip>
The FT has also been proven in a real-world experiment; physicists were able to show that over small spatial regions, for short times, in a liquid stimulated by lasers, small numbers of molecules behaved in anti-entropic fashion. So we not only can prove it mathematically, but when we go looking for the physical behavior that the math implies, there it is.

As long as it stays a theorem of mathematics and doesn't try to be a theory of science it's irrelevant. No matter how rigorous the math, its mapping onto the world is a theory of science; that mapping requires evidence or "proof" of its own even if the mathematical theorem is irrefutable.

And you report that's been supported; thanks. Since we're (well, I'm) in nitpicking mode, however, I'll beg for indulgence of my lack of comparable research and point out that "looking for the physical behavior that the math implies, there it is" isn't all we want. We also need to never see anything that the math says won't happen, after having looked pretty darned hard.

However, the FT says that there is a region of sizes, the macroscopic region, in which the 2LOT is strictly obeyed; another region, the quantum region, where it is not; and a border region between them where the 2LOT can be violated for brief periods over small regions. This is a drastic and vast oversimplification of the implications of the FT; I am well aware of it; the situation is far more complex than to state baldly that the second law of thermodynamics is maximally violated by QM. So please don't come tell me I'm "wrong," because I am well aware of this oversimplification. It is, nevertheless, possible to state that there are a large variety of situations in QM in which the strict 2LOT is not obeyed, and that major characteristics of the world around us would be very different from what we see if it were obeyed in this fashion.

Well, that FT stuff is news to me, and interesting to boot [I'll thank you to suppress any twittering about what my interest may suggest about the quality of my social life. I need not your pity, however, as I'm hoping to aquire many new friends on the tropical cold-kegger tour, possibly some while still sober <them or me; which matters little, but the window of opportunity for the latter may be brief>.]

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

Now, I don't know that the exact (or a more correct approximate, but congruent) device you showed will work; and I am by no means convinced that there is either a way to apply it that will produce macroscopic energy <snip>

Whatever we give up in microscopic energy output we can make up with VOLUME. They're nano-devices, right? I'll just insulate a box with room for a gazillion or two and still have room for at least a twelve-pack.

 

[RecoveringYuppy]

BTW I also see a major major scale problem on your drawing. If the door in your drawing is a "molecule" wide then what are the walls made of? The walls are shown much thinner than a molecule. If so, how do you prevent them from leaking in a myriad of ways?

 

[RecoveringYuppy]

OK. I just thought through the scale problems I mentioned in the last post. If you imagine that the opening on the left is large enough to allow a "molecule" to pass through than the black lines you've shown are complete fantasy as to their thinness. The "walls" you are showing wouldn't be "nano", they would be subatomic. If you actually draw this device with scale in mind and show the black lines as being several "molecules" thick you will realize that the passages through the door and through the turbine actually become long thin narrow passages where the molecules will bounce around and lose a lot of energy due to friction.

 

[RecoveringYuppy]

I tried to draw something to scale and found I couldn't do it and still have a drawing that would fit on any computer monitor (And I've got a huge monitor).

To the left, we have a molecule-sized hatch.

If so, then the problem is that no molecules will leave through the turbine because the passages you've shown through the turbine are much smaller than the opening on the left. Proper consideration of scale makes the problems here obvious.

 

[Merko]

Exact? How are you going to arrange for the door to close instantly and "exactly"?

It doesn't have to be instant. Let's assume the spring can close the door in one second. Then, yes, for one second after an opening hit from the outside, the molecules can move freely in any direction. But if the device doesn't work, and we have equal pressure, this will have no net effect. The important thing is, that except for this second after an opening hit, the door is blocked from the inside, but not from the outside.

In other words, the mechanism doesn't have to work all of the time. As long as it works some of the time, and isn't countered by anything that doesn't already assume that the device works - well, then the device works.

If the door is open 10% of the time the flow in both directions will be 10% of the flow in both directions through the turbine.

I don't think this is correct. The turbine extracts energy from molecules passing, an open door does not. But this is irrelevant, it only deals with inefficiencies. For our purpose, the inefficiency can be arbitrarily large, the device still works, because for inefficiency to occur, there has to be a net effect.

If you are imagining that the door can be adjusted to only open when a molecule is approaching and that the senstivity of the spring can be adjusted fast enough to shut the door with the minimal force and time for that particular molecule then you aren't accounting for the energy of that mechanism.

Energy of what mechanism? Did you look at the sketch of the device? There is no 'opening mechanism'. The entering molecule opens it itself, using its momentum. There are no mechanisms not shown in the sketch.

BTW there would also be mechanical losses in the spring.

Those would correspond to the losses in momentum of the molecule that hits the door. This is covered in point 3. Of course, the 'loss' will turn into heat, which in turn will be transfered back to the gas molecules. So it's not a real loss in this setting.

BTW I also see a major major scale problem on your drawing. If the door in your drawing is a "molecule" wide then what are the walls made of?

Of course the drawing is not to scale. It would be illegible if it was. I think this argument goes under point 1. I believe this mechanism would be theoretically possible to construct, judging by similar nano-technology mechanisms that I have read about.

 

[RecoveringYuppy]

In regards to post 16.

You're not considering that every molecule that opens the door won't necessarily enter the chamber. Some molecules are going to hit the door and bounce back outside of the chamber. If a few others also escape at the same time (and they will) you've lost the gain you are imagining.

 

[Merko]

If you actually draw this device with scale in mind and show the black lines as being several "molecules" thick you will realize that the passages through the door and through the turbine actually become long thin narrow passages where the molecules will bounce around and lose a lot of energy due to friction.

The walls don't have to be thicker than one atom, in theory. Also, they could be made from smaller atoms than what we have in the gas. However, this doesn't matter. There is no such thing as 'friction' on this scale. The molecules may lose energy (speed) while bouncing at the walls, but they are equally likely to gain speed from the wall. Additionally, they might go straight through the passage, even if it is thin and narrow. Again - inefficiency is not a problem here.

If so, then the problem is that no molecules will leave through the turbine because the passages you've shown through the turbine are much smaller than the opening on the left.

Please stop ruining the thread. The OP clearly mentions that the turbine is not on the same scale as the hatch.

Don't try to view the sketch as a photographic depiction, it is a conceptual sketch, not a blueprint.

 

[Merko]

You're not considering that every molecule that opens the door won't necessarily enter the chamber. Some molecules are going to hit the door and bounce back outside of the chamber. If a few others also escape at the same time (and they will) you've lost the gain you are imagining.

I don't have to consider that. If the door opens for any reason, it could be vibrations or a hit from the outside, and we don't have a pressure difference, then the chances of molecules 'escaping' are equal to the chances of molecules entering from the outside. No net effect. If we have a pressure difference - well, then the device works.

 

[RecoveringYuppy]

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??

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.

The only reason you can get away with imagining you've created a one way door is by severely distorting the scale. 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).