NASASpaceFlight.com Forum
General Discussion => New Physics for Space Technology => Topic started by: goran d on 01/15/2017 11:10 am
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What if we make a nano-chamber with a sliding gate at the middle. we put just one molecule of gas in it. When the gate is out, the pressure in the chamber is P. The two pistons on the sides are both in the inner position. When we close the gate, one half chamber gets pressure 0, and the other gets pressure 2P. The higher pressure piston moves outwards, generating current with predictable direction! The low pressure piston doesn't move inwards, because of mechanical obstacle. We can predict that when we slide the gate closed, half the generators will provide electricity in the same direction, and the other half none at all. When we open it, the electricity will be in the other direction. Therefore, we can connect them together and produce current with energy vastly exceeding a thermal fluctuation of a molecule. So it's direct heat-to-electricity conversion.
Space applications might include converting solar energy to electricity to power ionic engines, or convert heat from hot fusion into electricity.
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You've rediscovered Maxwell's Demon (https://en.wikipedia.org/wiki/Maxwell's_demon), an idea first proposed in 1867.
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The important part of that wikipedia article to read:
Several physicists have presented calculations that show that the second law of thermodynamics will not actually be violated, if a more complete analysis is made of the whole system including the demon.[6][8][9] The essence of the physical argument is to show, by calculation, that any demon must "generate" more entropy segregating the molecules than it could ever eliminate by the method described. That is, it would take more thermodynamic work to gauge the speed of the molecules and selectively allow them to pass through the opening between A and B than the amount of energy gained by the difference of temperature caused by this.
In your case, the measurement of current of which gates to open, opening the gates, and then closing them once the molecules are through is guaranteed to take generate entropy greater than the entropy decrease in entropy from getting the molecules all on one side. (Generate entropy basically means consume energy, so in practice your device would not be able to generate more energy from heat than standard methods.)
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The important part of that wikipedia article to read:
Several physicists have presented calculations that show that the second law of thermodynamics will not actually be violated, if a more complete analysis is made of the whole system including the demon.[6][8][9] The essence of the physical argument is to show, by calculation, that any demon must "generate" more entropy segregating the molecules than it could ever eliminate by the method described. That is, it would take more thermodynamic work to gauge the speed of the molecules and selectively allow them to pass through the opening between A and B than the amount of energy gained by the difference of temperature caused by this.
In your case, the measurement of current of which gates to open, opening the gates, and then closing them once the molecules are through is guaranteed to take generate entropy greater than the entropy decrease in entropy from getting the molecules all on one side. (Generate entropy basically means consume energy, so in practice your device would not be able to generate more energy from heat than standard methods.)
There is no measurement involved. The gates are open and shut periodically.
This is because, when we shoot gate, one gate moves=generate voltage, the other gate is just pressed harder against the wedge. It is irrelevant which gate gets the high pressure and which gets low pressure.
For example, if we attach a tiny magnet at each piston, and a coil at the back,
and connect the two coils in series, one coil gets voltage pulse in a known direction, while the other gets no voltage pulse at all. The direction of the pulse is same if one coil gets triggered or the other.
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The important part of that wikipedia article to read:
Several physicists have presented calculations that show that the second law of thermodynamics will not actually be violated, if a more complete analysis is made of the whole system including the demon.[6][8][9] The essence of the physical argument is to show, by calculation, that any demon must "generate" more entropy segregating the molecules than it could ever eliminate by the method described. That is, it would take more thermodynamic work to gauge the speed of the molecules and selectively allow them to pass through the opening between A and B than the amount of energy gained by the difference of temperature caused by this.
In your case, the measurement of current of which gates to open, opening the gates, and then closing them once the molecules are through is guaranteed to take generate entropy greater than the entropy decrease in entropy from getting the molecules all on one side. (Generate entropy basically means consume energy, so in practice your device would not be able to generate more energy from heat than standard methods.)
There is no measurement involved. The gates are open and shut periodically.
This is because, when we shoot gate, one gate moves=generate voltage, the other gate is just pressed harder against the wedge. It is irrelevant which gate gets the high pressure and which gets low pressure.
For example, if we attach a tiny magnet at each piston, and a coil at the back,
and connect the two coils in series, one coil gets voltage pulse in a known direction, while the other gets no voltage pulse at all. The direction of the pulse is same if one coil gets triggered or the other.
This is an interesting variation on Maxwell's demon, but it still won't be able to do better than other ways of turning heat into electricity. It only does anything if the internal pressure is greater than the external. Try going through detailed calculations of useful work done vs ambient conditions, and compare that to standard heat engines of various thermodynamic cycles.
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Here is a diagram.
The system is supposed to periodically change between 1 and either 2a or 2b.
Energy comes from interaction of the "gas" and the walls of the chamber. ie when transition happens, heat energy of the molecule gets converted to mechanical energy, and then electric. The molecule regains its "heat" by bouncing off the chamber walls.
That's the idea at least.
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That is basically what you described,but you still haven't worked out any thermodynamics, or compared efficiency to that of standard thermodynamic cycles.
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Here is a derivation of the work done per cycle.
It is approximately 0.27kT
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I asked for the efficiency, which you haven't provided yet (hint: the isothermal assumption may cause you some issues in calculating efficiency, especially when you are claiming that 1/4 of the thermal energy of a molecule is being removed)
https://en.wikipedia.org/wiki/Thermal_efficiency
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Since there is no coolant, I can't find the thermal efficiency. The device will simply suck in heat without transferring it to a coolant. The heat is transferred to the molecule from the interaction with the chamber walls.
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You just stated that heat transfers are happening, so that means there is a thermodynamic efficiency. It is nonsensical to say that there isn't an efficiency. It sounds like you need to think about your design more, and fully consider external interactions and define boundary conditions through which they occur.
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Well if there is heat consumed, and no heat transferred to a coolant, that corresponds to thermodynamic efficiency of 100%.
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Well if there is heat consumed, and no heat transferred to a coolant, that corresponds to thermodynamic efficiency of 100%.
You just proved that you don't understand what you are talking about. Try using a PV diagram, and don't forget that you are doing work on the gas on the other side of the piston too.
As an alternative, try to consider what is happening on a mircoscopic level. The single molecule does not provide a continuous pressure, and due to the small size of this piston, this is true on the other side of the piston as well. You will then be trying to extract energy from basically Brownian motion of the piston. Try considering what mechanism could do that, and how in the world you could string billions upon billions of them together while not having the random nature of the individual generators not result in generated voltages simply cancelling.
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The Nefastis Machine probably works about as well as this.
http://www.eoht.info/page/Nefastis+Machine
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Then we use electrostatic generator, and it provides the outside "pressure". No gas on the other end.
That was the original idea but i modified it to be a coil+magnet, so i didn't think about gas for the pressure.
No gas on the other end, "outside" pressure produced by moving plate capacitors.
Also if there was gas outside, it will get exactly the same amount of heat when the piston moves out that it will spend when it moves back in, so no change.
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Saying "electrostatic generator" does not explain anything. Also saying the generator will now provide the constant pressure adds more questions (how does it do that), and does not change the fact that you are jumping between perfect energy conversion, and doing irreversible* PV work.
* I am guessing that you aren't familiar with the thermodynamic concept of irreversible. Basically anything that is done in finite amount of time cannot be undone without extra inputs (e.g. energy).