Basic concept:
Apply the Archimedean screw principle to electric current, turning this water pump into an electron pump.
The Archimedes screw is a helical surface surrounding a central cylindrical shaft placed obliquely with its bottom end in the water. Its rotation allows the water to flow upwards, which, by the earth's gravity, is maintained at the bottom of each loop of the screw. A more "modern" version, revisited by Leonardo da Vinci, is to use a helical tube instead, see attached diagram.
The idea: replace the helical tube by a solenoid, replace the water by electrons, replace gravity by an electrostatic field obtained by a positively charged plate placed on one side along the solenoid. The free electrons attracted by the plate being maintained on one side only of the solenoid, the rotation of the solenoid makes appear a relative movement of the electrons, thus a current. This would require rotating contacts, so we will make it simpler.
Instead of rotating the solenoid, we will use a fixed solenoid and a rotating plate, see second diagram. The electrons of the solenoid will be attracted by the plate and follow its rotation. They will turn in the solenoid, creating a current.
As we all prefer, I think, solid state rather than mechanical rotation, the final idea is to replace the rotating plate by two pairs of diametrically opposed fixed plates, fed in quadrature to create a rotating field.
Note that since electrons move very slowly in a conductor, the rotation will have to be done very slowly too (linear speed of the order of mm/s), otherwise it is not sure that the electrons can follow the plate because they are subject to the resistance of the conductor.
I don't know if it can work. If it works, I don't know how much current we can reach. Finally I have no idea of practical application nor if it can be a way for energy. I have not seen the principle applied anywhere in a conductor. A similar idea is exploited in travelling wave tubes, but there it is in vacuum, not in a conductor. So it's just something I would like to test.
I already tried to apply the idea to dielectrics (it's on this forum), but it's impossible because the effect on positive charges cancels the one on negative charges. But in a conductor, it should work. Before I go into a practical realization, please tell me if you see any objections to the possibility of operation.
Can I share your hypothesis a bit ? ( for more eyes and opinions?
There is a moderated board at Stefan's for this "open source sharing"!
No worries either way ( feel free to remove this post if ... for any reason
Thanks for sharing
Chet
EDIT for comment below
I will pm you ..as some of your points need clarity!
Quote from: Chet K on 2022.10.25, 12:23:34
Can I share your hypothesis a bit ? ( for more eyes and opinions?
There is a moderated board at Stefan's for this "open source sharing"!
...
Chet,
This thread is public so there is nothing to stop anyone talking about it elsewhere. So feel free to share but please, not anywhere: I wouldn't appreciate it at all if it was done on overunity.com or energeticforum.com, sites that have censored me and where I can't post anymore. I would be very annoyed to find there anything that I put here, next to the fakes and nonsense that are found in great quantity on these sites and that skeptics are prevented from commenting. :(
Thanks
Hi F6FLT,
Reading this thread reminded me of the patent attached...
Fred
Hi Fred,
Only the helical strip has something in common with my setup since in the patent we are dealing with a magnetic generator device without any link with electrostatics, and whose principle is conventional: the rotation of the ferromagnetic helical strip changes the reluctance of the magnetic circuit between the two poles of the electromagnet, and thus we have a variation of flux which induces current in the coil 3 (fig. 1).
On the other hand, it can also be seen as an Archimedean screw in which, contrary to my setup, it is not the electrons that replace the water, but the magnetic flux. This new idea opens a perspective but with a very different setup.
I will think about it but after the implementation of the device that I presented above. I just got the motor of a microwave oven to make the plate connected to the HV power supply turn around the coil, with a regular movement.
F6FLT
QuoteI don't know if it can work. If it works, I don't know how much current we can reach. Finally I have no idea of practical application nor if it can be a way for energy. I have not seen the principle applied anywhere in a conductor. A similar idea is exploited in travelling wave tubes, but there it is in vacuum, not in a conductor. So it's just something I would like to test.
It does work and I built and tested the device you posted around 2012. I also used this setup to calibrate a rotating coil atmospheric charge detector which were common in the late 1800's. As the coil rotates some electrons are dragged along due to the positive charge of our atmosphere. This charged a small capacitor with one terminal also connected to ground. The voltage on the capacitor gives us an indication of the difference in potential (V/cm) between the atmosphere and ground. The larger the loop the better and most used coils around 36" in diameter.
I was experimenting with this stuff when researching Lord Kelvins work and I believe it was he who used this setup.
These kinds of devices were later replaced with the atmospheric field mill still in use today which doesn't require brushes.
https://en.wikipedia.org/wiki/Field_mill
AC
Hi F6FLT,
I must admit I had only skimmed the thread when I sent the patent. I saw the word Archimedes Screw and the patent jumped into my mind. It was no deeper association than that. After reading I found it different and more interesting than I originally thought.
I think you could accomplish this in a semiconductor where you would have electron drift current in presence of an E field. I don't think it would work in a conductor since an E field doesn't penetrate it-- you would have to connect a wire to a conductor to get the current, which would bring you back to the conventional situation.
https://en.wikipedia.org/wiki/Drift_velocity
The simplest case might be a semiconductor cylinder with a charged disc at one end. For clarity we say the disc isn't touching the cylinder and that no current comes from it. This would be the case with an Electret, the electric equivalent of a permanent magnet.
Electrons and holes will flow and a current is generated. Since the E field doesn't lose charge in this process, how is energy conserved in this system?
It's also interesting to note that the electron drift current increases with the temperature of the semiconductor so there seems to be a bit of a Maxwell's Demon happening with the presence of the E field...if not the random thermal movements of the electrons/holes would still cancel out regardless of the presence of the E field...
Fred
@AC
I would have already posted something similar in 2012?! I don't remember, I have a very bad memory :(. Do you have the reference?
Quote from: Orthofield on 2022.10.28, 00:11:25
I don't think it would work in a conductor since an E field doesn't penetrate it
When you think about the capacitor, it is clear that an external E-field from a plate attracts electrons to the surface of the other one. If you slide a small polarized plate over a long conducting strip, the electrons in the strip will always be attracted to the sliding plate.
The question is therefore whether this effect leads to a longitudinal displacement of charges in the strip, or whether it is a simple tidal effect like the moon making the water of the oceans rise in its direction while rotating around the earth, but without horizontal displacement of water.
This case, equivalent to your objection, also corresponds to what we read in the courses since an E field external to a conductor can only have an orthogonal component at its surface.
On the other hand, in the case where the screw rotates and the plate remains fixed, it is clear that there is an excess of electrons in the part of the coil close to the plate. As the coil rotates and the electrons remain at the same position, we have a displacement of the conductor relative to the electrons, thus a displacement of the electrons relative to the conductor, thus a current. As this effect is the reciprocal of the one with the fixed coil and the rotating plate, this questions it.
How would you explain an absence of current with the fixed plate and the rotating coil?
Quote
I think you could accomplish this in a semiconductor where you would have electron drift current in presence of an E field. [...]
The simplest case might be a semiconductor cylinder with a charged disc at one end. For clarity we say the disc isn't touching the cylinder and that no current comes from it. This would be the case with an Electret, the electric equivalent of a permanent magnet.
Electrons and holes will flow and a current is generated. Since the E field doesn't lose charge in this process, how is energy conserved in this system?
It's also interesting to note that the electron drift current increases with the temperature of the semiconductor so there seems to be a bit of a Maxwell's Demon happening with the presence of the E field...if not the random thermal movements of the electrons/holes would still cancel out regardless of the presence of the E field...
Fred
I do not see very well the constitution of the device, in particular the circuit in which this current would circulate. When we place the charged disk, I understand that it causes a displacement of electrons and holes. But how could it continue indefinitely? The restoring coulombic force inside the semiconductor will make them reach an equilibrium.
Quote from: Chet K on 2022.10.28, 12:13:25
https://youtu.be/UcwBmqd60C4
Privately I did receive this opinion from smokey
Neutral or nil result to be expected!
not sure this is appropriate to place this response here ( will check with him later
Chet
It is a possibility that the result is zero, for the reason I indicated above in response to Orthofield's relevant objection.
A field orthogonal to the surface can't exert a work for a longitudinal movement of the charges.
But if the rotation of the plate does not drive the electrons, on the other hand it is not clear why the reciprocal case of the fixed plate and the rotating coil would not work. If the answer to this question also allows to foresee a null effect, then the starting idea will have to be revised for a work around of the problem of the orthogonal field. This work around could be the use of a charged dielectric instead of a conductor.
F6FLT
QuoteI would have already posted something similar in 2012?! I don't remember, I have a very bad memory
No, if you read my post I said I built and tested the Archimedes' screw principal for electricity your talking about and posted. The device and principal was actually invented in the late 1800's and used to measure atmospheric electricity. Thus it is not new or unique in any sense of the word.
AC
Hi F6FLT,
Yes, I see what you mean, there would be a concentration of charge on the surface of the (metal) screw opposite the plate, and that would make an apparent current as the screw rotated. I guess the question, to be answered by experiment, is whether energy consumed to rotate the screw + energy lost in resistance (ie charge 'friction') can be less than the power dissipated in a load attached to the screw.
My circuit was not well thought out. To demonstrate drift current in a semiconductor device, one can use a voltage source and high impedance in parallel with it, with the load resistance in parallel with those two legs. There are then two components to the current through the load, a small residual current from the voltage source, and the drift current. By using a pure voltage source like an electret, unconnected to the semiconductor, I was trying to bring out the fact that the drift current is additional to any current caused by the voltage source. But in that case, as you said, the semiconductor would simply polarize and the drift would stop. In the case where there is a wire connection, the drift current doesn't stop, as long as the voltage is present.
It still seems to me that there's the possibility of generating useful power from the heat around the semiconductor. Then the voltage is in effect aligning the thermal energy in one direction, like a Maxwell's Demon. But none of this is relevant to your concept, and I'll take it to another thread here.
Fred
Quote from: Orthofield on 2022.10.28, 15:53:38
Hi F6FLT,
Yes, I see what you mean, there would be a concentration of charge on the surface of the (metal) screw opposite the plate, and that would make an apparent current as the screw rotated...
That's exactly it, you have captured the effect that I hope. Since this would be the work of the Coulomb force, I don't believe there would be OU there. But what interests me here is to have an additional degree of freedom in the way of coupling circuits, so as to imagine in a second stage, more sophisticated systems than those seen so far which gave nothing.
It remains to be seen if there would really be a current. I hope to be able to experiment it in about ten days.
Quote
...
My circuit was not well thought out. To demonstrate drift current in a semiconductor device, one can use a voltage source and high impedance in parallel with it, with the load resistance in parallel with those two legs. There are then two components to the current through the load, a small residual current from the voltage source, and the drift current. By using a pure voltage source like an electret, unconnected to the semiconductor, I was trying to bring out the fact that the drift current is additional to any current caused by the voltage source. But in that case, as you said, the semiconductor would simply polarize and the drift would stop. In the case where there is a wire connection, the drift current doesn't stop, as long as the voltage is present.
It still seems to me that there's the possibility of generating useful power from the heat around the semiconductor. Then the voltage is in effect aligning the thermal energy in one direction, like a Maxwell's Demon. But none of this is relevant to your concept, and I'll take it to another thread here.
Fred
Your idea is worth trying out too. A Maxwell demon is part of the possibilities of FE, the principle has not been invalidated in the general case, only in some particular cases. An electric Maxwell demon has already been proposed and experimented. The current was very low, so I'm not sure if all the experimental artefacts have been eliminated but maybe. It is not a semiconductor that is used, the depletion zone will have to be replaced by the junction between electrodes in a vacuum tube, where the work function of two electrodes is biased by a magnetic field and not by an electret. There is a little family resemblance with your idea, so I put the two pdf that deal with it, from the same authors: https://arxiv.org/pdf/physics/0311104 and https://arxiv.org/pdf/physics/0509111
The experiment: https://www.youtube.com/watch?v=FCCPeEKIVvQ
If you start experimenting with your idea, I will follow it with attention.
Hi F6FLT,
Thanks for sending those references and the video! I was aware of this principle already from other sources, but it is very helpful to see it demonstrated.
There's a US patent that covers this principle, from 1959. See attached. Fig. 2 in the patent is identical to a diagram shown in both of the two papers you sent. The operating principle is described at the bottom of col. 3 on pg. 7.
The Hatsopoulos device has an ES field created by batteries, and thus moves more into the area that I'm interested in--except that I want to do it in solid state to avoid using tubes, etc.
The principle of nonreciprocality, or time-irreversible, or 'rachet' processes is important for understanding this area. It was I believe Casimir, or possibly Onsager who said that a magnetic field was necessary to create electrical nonreciprocity, as we see in the Hall effect. But the rise in drift current with increased temperature seems to indicate something of a rachet effect with only an E field.
Yes, I'm planning an experiment now. I'm going to use a thermoelectric module, and bias it with 20 V or so (I'm just guessing as to correct bias at this point), and see if any noticeable power is generated when the module is in a uniform heat bath (my oven on warm). I don't have much in the way of test equipment so measurements will be crude.
Fred
Hi fred
The ratchet technique for recovering useful energy from heat seems simple. After all, a simple diode that rectifies the noise of a resistor would be sufficient.
The problem is the threshold effect. The noise does not exceed the threshold of the "ratchet" that is the diode, so it does not work.
You would need a very low threshold, but then it would also be subject to thermal noise, and the temperature and noise being the same on both sides, you would lose the functionality of the diode.
This is a general principle problem with single temperature thermal baths. For example, it is not well known, but a solar panel that would be at the same temperature as the sun will no longer work (even if it was designed to withstand this temperature). Even for a solar panel, there must be a temperature difference between the source and the load.
So it is clear that we need an additional "trick", like the irreversibility or non-reciprocity you are talking about. We saw from the Chinese patent that the magnetic field was a possibility. I don't know of any other.
I haven't looked at the patent you provided yet, I will.
Hi F6FLT,
My basic idea is to stimulate the noisy/heated system with an E field. This will work as long as the field source consumes little or no power. I've seen no evidence that drift current requires an additional current from the bias--only a 'pure' voltage-- so I think it will work.
To the larger point, one CAN create a 'noise-free' volume that noise energy will flow into. Harold Black demonstrated this in a now forgotten patent, attached. Black invented the negative feedback circuit, and in this patent he showed that it's possible to feed noise back on itself to create a zero noise circuit. I quote the patent at length here so you won't need to read all of it. He reports on pg. 9 of the pdf, that "I have discovered that feedback action can produce resistances or generalized impedances free from resistance-noise---that feedback action can transform ordinary resistances (or generalized impedances) to resistances (or generalized impedances) that are free of all noise, including thermal agitation. For example, if the net across the bridge points of the input hybrid coil be a resistance, the feedback can transform this resistance by producing an enlarged copy of it as the amplifier input impedance, this copy having the remarkable property of freedom from resistance-noise."
As one would expect, if there is no resistance noise in one part of the circuit, another part of the circuit must lose some of its thermal noise to it to restore balance, and this is the case. On the same page he reports: "I have discovered that feedback action can abstract heat from a body. When a resistance is connected to an amplifier, feedback action can be made to abstract heat from the resistance or cool it. For example, if an electric conductor or resistance be connected across resistance of the type described above as free from resistance noise, the effect of making the connection is to abstract heat from the ordinary resistance or cool it, the Ordinary resistance receiving no energy from the other resistance but giving up energy of thermal agitation to the other resistance in the form of an electric current. To observe the cooling effect the resistance to be cooled can be heat insulated. If it is not insulated, the small losses due to thermal agitation are readily replaced from the relatively vast reservoir of heat surrounding
the unit." These noiseless amplifiers were later developed for Radio Telescopes by Robert Forward.
So here is a purely electronic heating and cooling effect, and a purely electronic extraction of noise energy. My point in going on at length about this, aside from what I consider the inherent interest, is that most attempts to cohere thermal noise take a passive approach, but an active approach is probably going to be more fruitful-- as long as energy needed to cohere the noise is less than that provided by it. That's the main question.
This is far afield from the original subject of this thread, but it seems to interest you as well, so I leave it here.
Fred
Quote from: Orthofield on 2022.10.28, 15:53:38
Hi F6FLT,
Yes, I see what you mean, there would be a concentration of charge on the surface of the (metal) screw opposite the plate, and that would make an apparent current as the screw rotated. I guess the question, to be answered by experiment, is whether energy consumed to rotate the screw + energy lost in resistance (ie charge 'friction') can be less than the power dissipated in a load attached to the screw.
My circuit was not well thought out. To demonstrate drift current in a semiconductor device, one can use a voltage source and high impedance in parallel with it, with the load resistance in parallel with those two legs. There are then two components to the current through the load, a small residual current from the voltage source, and the drift current. By using a pure voltage source like an electret, unconnected to the semiconductor, I was trying to bring out the fact that the drift current is additional to any current caused by the voltage source. But in that case, as you said, the semiconductor would simply polarize and the drift would stop. In the case where there is a wire connection, the drift current doesn't stop, as long as the voltage is present.
It still seems to me that there's the possibility of generating useful power from the heat around the semiconductor. Then the voltage is in effect aligning the thermal energy in one direction, like a Maxwell's Demon. But none of this is relevant to your concept, and I'll take it to another thread here.
Fred
I experienced something akin to this with electrostatics. When an isolated charged plate was providing the inducing charge, the induced current was entirely separated from the charge current induction/depletion cycle.
which leads to external circuits powered by the independent electrostatic machines.
Otto von Guericke (et all)
Hi Sm0key2,
If I understand you correctly, something like a (solid state?) ES source with a pulsating field strength was inducing a current in a circuit nearby? And that current didn't vary with the charge/discharge of the source? If so, very interesting!
I'm aiming at as close to an electrostatic source as I can get, although relatively low voltage.
Fred
That's not to say to use a sulfur plate in your experiments, but the principal of the nature would imply if the plate carries the charge of the conductor above, and was of sufficiently larger area than the perpendicular surface of the curvature of the coil, moving the field or coil would induce a charge. An opposing electrical 'drag' will occur if the charge carrier is conductive at those voltages.
To paraphrase Tinsel Koala: it works best when the charge carrier is a pure dielectric
Quote from: Orthofield on 2022.10.29, 21:37:09
Hi Sm0key2,
If I understand you correctly, something like a (solid state?) ES source with a pulsating field strength was inducing a current in a circuit nearby? And that current didn't vary with the charge/discharge of the source? If so, very interesting!
I'm aiming at as close to an electrostatic source as I can get, although relatively low voltage.
Fred
To put it clearly, the electrostatic source of any type is connected to an externally charged plate, that is isolated physically from outside systems.
another electrostatic inductor is moving through the field that is created on the plate.
A similar example is the separation of the charge mechanism of a van de graff and the discharge of charged sphere(s) connected to its' output
Quote from: Sm0ky2 on 2022.10.29, 21:51:26
To put it clearly, the electrostatic source of any type is connected to an externally charged plate, that is isolated physically from outside systems.
another electrostatic inductor is moving through the field that is created on the plate.
A similar example is the separation of the charge mechanism of a van de graff and the discharge of charged sphere(s) connected to its' output
With the Archimedean screw, the question is to create a direct current from the rotation of the screw in a field or conversely by rotating the field around the screw.
The simple movement of a plate in a field amounts to a variable capacitive coupling between the plate and the conductors that generate the field. So if a circuit connects the moving plate to the ground, a current will flow during the time of the displacement since C and U can vary and i= dQ/dt = d(C.U)/dt = U.dC/dt + C.dU/dt.
In the case of the Archimedean screw, the capacitance between the plate and the solenoid is constant, as is its voltage. As I am not claiming OU here but only a way to drive a current in a circuit from an external voltage, the energy would come from the one needed for the rotation, not from the voltage that polarizes the plate (as in the case of the Faraday disk, where the energy does not come from the source of the magnetic field). It is therefore important to understand this so as not to mix it with devices with variable capacities and potentials, and therefore unrelated.
I'm not at all sure it will work, I even have good reasons to think it won't, but a little doubt will make me try anyway.
@Fred
The principle of Hatsopoulos' patent is indeed very close to the Chinese Maxwell's demon in the way of using the magnetic field to promote the movement of electrons from the hot plate to the cold plate. But I wonder why this temperature difference since it should work as well with hot plates only. The extraction of electrons from a hot plate and then their deflection by the field seems to be the only condition necessary for operation.
Quote from: Orthofield on 2022.10.29, 14:56:59
Hi F6FLT,
Thanks for sending those references and the video! I was aware of this principle already from other sources, but it is very helpful to see it demonstrated.
There's a US patent that covers this principle, from 1959. See attached. Fig. 2 in the patent is identical to a diagram shown in both of the two papers you sent. The operating principle is described at the bottom of col. 3 on pg. 7.
The Hatsopoulos device has an ES field created by batteries, and thus moves more into the area that I'm interested in--except that I want to do it in solid state to avoid using tubes, etc.
The principle of nonreciprocality, or time-irreversible, or 'rachet' processes is important for understanding this area. It was I believe Casimir, or possibly Onsager who said that a magnetic field was necessary to create electrical nonreciprocity, as we see in the Hall effect. But the rise in drift current with increased temperature seems to indicate something of a rachet effect with only an E field.
Yes, I'm planning an experiment now. I'm going to use a thermoelectric module, and bias it with 20 V or so (I'm just guessing as to correct bias at this point), and see if any noticeable power is generated when the module is in a uniform heat bath (my oven on warm). I don't have much in the way of test equipment so measurements will be crude.
Fred
I looked into the possibility of thermionic emission some time ago, I have a number of files on a back-up memory stick somewhere. The "Nottingham Effect" comes to mind and also the little used "Inverse Nottingham Effect". The scheme used magnetic fields to direct the cathode emissions away from the anode that supplied the electric field pulling the electrons away to another collecting electrode sitting behind the cathode and therefore not in the electric field. If anyone is interested, I will dig out the data.
Smudge
Hi Smudge,
As it happened, I just reviewed one of your papers on this the other day. Here it is.
Fred
Quote from: F6FLT on 2022.10.30, 10:42:34
@Fred
The principle of Hatsopoulos' patent is indeed very close to the Chinese Maxwell's demon in the way of using the magnetic field to promote the movement of electrons from the hot plate to the cold plate. But I wonder why this temperature difference since it should work as well with hot plates only. The extraction of electrons from a hot plate and then their deflection by the field seems to be the only condition necessary for operation.
Hi F6FLT,
Looking further, the concept of using magnetic fields to direct electrons from plate to plate seems to have been prior art even at the time of Hatsopoulo's patent, being used in a wide variety of so-called 'cross field devices'. For the most part the US patent office hasn't allowed devices in a single temperature bath because of the thermodynamic issues, so I'm guessing even if the inventor had thought of it, he wouldn't have put it in there. I've only seen two patents that convert heat at a single temperature, and each is somewhat 'in disguise'-- one using the diffusion current due to differential doping of semiconductors, and one as a quasi-Seebeck effect.
Fred
Quote from: Smudge on 2022.10.30, 15:50:36
I looked into the possibility of thermionic emission some time ago, I have a number of files on a back-up memory stick somewhere. The "Nottingham Effect" comes to mind and also the little used "Inverse Nottingham Effect". The scheme used magnetic fields to direct the cathode emissions away from the anode that supplied the electric field pulling the electrons away to another collecting electrode sitting behind the cathode and therefore not in the electric field. If anyone is interested, I will dig out the data.
Smudge
Hi Smudge,
I think some people would be interested, including me. I am thinking of checking in a future project with a simple plasma in the air if it is possible to "sort" the charges thanks to a magnetic field and according to their energy. The Nottingham effect would seem to help.
Perhaps you could open a new thread on the subject?
Hi F6FLT,
I'm not sure if you noticed, but I uploaded one of Smudge's papers just before you wrote to him.
I've ordered the parts for a test of 'stimulated drift current in a thermoelectric module at a single temperature.'
Fred
@Freed
Thanks for the information, I had indeed missed the paper of Smudge, and to give us the result when you will have done the tests
Quote from: F6FLT on 2022.11.01, 16:03:07
@Freed
Thanks for the information, I had indeed missed the paper of Smudge, and to give us the result when you will have done the tests
Hi F6FLT,
I've done some initial tests with a thermoelectric module with somewhat interesting results. I used the module whose datasheet is attached. My wife has a device for drying the air in the laundry area that consists of a heating element in a plastic box with holes in the top. The temperature measured with a digital cooking thermometer is a steady 54.4 C.
The bias circuit consisted of 4 AA batteries in series with a 10K resistor. Voltage was 6.65 V and the I was below 1 mA, the resolution of my Fluke meter.
After checking that the module worked in the normal fashion, I wanted to see if it would generate power at a single temperature. I put the module on top of the dryer hot side down but without a heat sink on the exposed cold side. The upper side of the module was exposed to air, but this was warm air from the dryer, and the temperature between top and bottom of the module was less than a degree apart after 5 minutes.
After it had been in position for 5 minutes I took measurements. The V across the module was around 65 mV and the current through it was 15 mA giving a power output of .9 mW. The current didn't drop over time though the voltage did vary considerably, so this was an estimate of the average V. It's a pretty efficient module as these things go-- from the datasheet I estimate that it generates about 19 mW for every degree difference between cold and hot sides. So perhaps the small difference between the sides in my setup was enough for a small standard Seebeck output.
Application of the bias across the cell had inconsistent results. There was always some effect, but sometimes the I of the cell dropped, and sometimes it rose. There might be an effect essentially due to the speed of my manual switching of the voltage with a key type switch. In any case the bias V was very low, and results were within the margin of error. I'm going to get a power supply so I can bias with 60 V.
The final result was the most interesting. I had two small disc shaped neodymium magnets and on a whim put them on top of the module while it had a stable output of around .9 mW. The output immediately shot up to 79 mV and 23 mA, or 1.7 mW! I thought perhaps this was due to the magnets being cold and providing a temporary temperature differential, and indeed the effect seemed to vary somewhat each time I did it. However, I left the magnets on the dryer surface for some time to reach equilibrium and they still had an immediate effect on both current and voltage.
Perhaps a Hall or Nernst effect? I have no idea..
Fred
Quote from: Orthofield on 2022.11.15, 01:02:58
...
The final result was the most interesting. I had two small disc shaped neodymium magnets and on a whim put them on top of the module while it had a stable output of around .9 mW. The output immediately shot up to 79 mV and 23 mA, or 1.7 mW! I thought perhaps this was due to the magnets being cold and providing a temporary temperature differential, and indeed the effect seemed to vary somewhat each time I did it. However, I left the magnets on the dryer surface for some time to reach equilibrium and they still had an immediate effect on both current and voltage.
Perhaps a Hall or Nernst effect? I have no idea..
Fred
Hi Fred,
It is indeed very intriguing. We would need to know what materials are inside the thermoelectric generator. The effect of the magnet could be to optimise the operation by chance, by mechanical pressure on the magnetic products inside or by variation of their permeability. Otherwise it's more interesting. If you are sure that you have eliminated the effect of temperature perturbation when you position the magnet, then the effect could be due to the transverse deflection of the electrons by the Lorentz force, which would favour the dissymmetry between electrodes as if it were a temperature difference.
The results would have to be evaluated according to the direction of the magnetic field with respect to the plane of the component.
Hi F6FLT,
Your comments are very useful going forward. I haven't had time today to do any more tests, but the very first one will be to stand the module on end on the hot surface, equalize the temperature, and then check the output again. If the output is only due to residual standard Seebeck effect then it should be much reduced since both sides have the same contact with heat. I expect this will be the case. Then apply the magnets as before but putting a small gap between them and the module to eliminate any mechanical effects.
There's no information on the Marlow site about the composition of the module, but the vast majority of commercial modules are made of p- and n- doped Bismuth Telluride. BiTe is a high electron mobility Hall material. Establishing the Hall Coefficient Rh of the BiTe material is more difficult since it varies depending on the doping material and its concentration, and also declines greatly with temperature for some materials. Rather than get into a lot of detail about that, I'll do the suggested test as to orientation of the B field. In the test done already, the field is parallel to the flow of electrons and holes, so if there were a Hall effect it would indeed resemble a Lorentz force acting on them, causing them to corkscrew down through the ceramic blocks. This would tend to make their mean free paths longer and reduce efficiency, I think. Putting the magnets at right angles to electron and hole flow should establish whether the Hall effect is in play.
Fred
Hi F6FLT,
So I was only able to do one test today. I stood the module on edge on my air dryer. Temp was still 54.4, very steady. After 20 minutes I checked V and I. V was a steady 4 mV, and current varied between 1-2 mA, giving at minimum an output of .4 mW.
This should be a good test of output at a single temperature since the ceramic bricks of n- and p- BiTe are oriented parallel to the surface of the heat source. Even with a heat differential between the edge touching the heater and the top edge, all n- and p- pairs at the same height experience the same temperature, so no current should flow through any pairs due to the Seebeck effect.
This would seem to indicate a small output from a single temperature thermal bath, as in the Graphene experiments.
Fred
Quote from: Orthofield on 2022.11.16, 04:26:37
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This would seem to indicate a small output from a single temperature thermal bath, as in the Graphene experiments.
Fred
We should be sure by lowering the temperature to room temperature instead of 54.4.
Even if the current was only 100µA, it would be significant. Is there still a current at room temperature?
Hi F6FLT,
I got 0 V and 0 A for this test. However, my meter can only go down to 1 mA and 1 mV, so these lower outputs wouldn't be detected.
Now I'm trying the small magnets under these conditions, and without pressure or contact by the magnets.
Fred
Hi F6FLT,
Placing the stack of two small neo magnet discs on the surface of the module at RT (about 21 C), separated from it by a thin cloth, immediately caused the voltage to rise to 2-3 mV, with still no observable current. The V still seems to gradually be rising, so I'm going to leave the meter connected and come back after a while..
Fred
Hi F6FLT,
It rose to 5 mV and then gradually declined to zero over about 20 minutes. Not sure what to make of that...
Fred
@Fred
Difficult to draw conclusions. Maybe a certain temperature threshold is needed. It should be left for a long time in a hot container (60 c or more) and extremely well regulated, and see if a current stabilizes.
Hi F6FLT,
Indeed difficult, especially with my primitive equipment. I'm jumping ahead too fast due to finding the magnetic effect. I need to read more about Nernst effect anyway. I'm going to drop it for now to focus on establishing some basic facts. I will wrap the module tightly in plastic and put it in a bowl of hot water in the sink, not touching the sides. Then after some time to give the module a chance to reach a uniform temperature, I'll take measurements of V, I and temperature of the bath. This will establish for sure whether there is a single temperature effect, and also possibly some sense of the magnitude relative to temperature.
Fred
Hi F6FLT,
I did the test with the module wrapped in plastic and suspended in a water bath at 65 C. After some ten minutes in the water, there was only a persistent V of 1-2 mV and no current to the limits of my meter. It will take a more sensitive meter or a hotter bath to go further.
In the meantime I'll return to trying a bias voltage, which was my original objective.
Fred
Quote from: F6FLT on 2022.10.25, 08:30:38
Note that since electrons move very slowly in a conductor, the rotation will have to be done very slowly too (linear speed of the order of mm/s), otherwise it is not sure that the electrons can follow the plate because they are subject to the resistance of the conductor.
I don't know if it can work. If it works, I don't know how much current we can reach. Finally I have no idea of practical application nor if it can be a way for energy. I have not seen the principle applied anywhere in a conductor. A similar idea is exploited in travelling wave tubes, but there it is in vacuum, not in a conductor. So it's just something I would like to test.
I already tried to apply the idea to dielectrics (it's on this forum), but it's impossible because the effect on positive charges cancels the one on negative charges. But in a conductor, it should work. Before I go into a practical realization, please tell me if you see any objections to the possibility of operation.
Everything seems to be simple here. The interaction of charge and field is always associated with work. If an electric charge moves against the forces of an electrostatic field, then this leads to an increase in the field potential. If, on the contrary, it leads to a decrease in the field potential. In this case, the movement of the charge due to the forces of the electrostatic field will lead to a decrease in the field potential. To maintain this potential at a constant level, an external high-voltage source that creates a field must do work (expend power).
In addition, they say, the electric field does not penetrate the conductor. its is not there.
What will push the electrons?
Quote from: chief kolbacict on 2022.11.17, 06:38:05
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In addition, they say, the electric field does not penetrate the conductor. its is not there.
What will push the electrons?
The question is legitimate, this is the point that makes me doubt the operation, I talked about it with the tidal effect.
Let's place ourselves in the case where the coil is fixed and the plate turns around it.
We must also see the coil as a plate with which the other real plate constitutes a capacitor.
As in any capacitor where the electrons accumulate on the opposite plates, the electrons of the coil will be attracted to the side of the plate, even when the plate is rotating. As a result, there will be a displacement of electrons relative to the coil, and therefore a current.
The defect is that the electrons attracted to the plate can come from either side, i.e. some turn clockwise to move towards the plate, and others counter-clockwise, cancelling out their effects. This is the tidal effect I fear, where the net movement of the electrons will not depend on the direction of rotation of the plate.
Only experiment can tell, but I have postponed testing because the thread on the gradient of the vector potential seems more promising.
Hi F6FLT,
My initial concept before going off into magnetic effects, or single temperature operation, was to determine whether a bias voltage could improve the output of a thermoelectric module. I've established this pretty solidly now.
A 6.65 bias V was applied in series with a 1 Mohm resistor through a switch to the negative terminal of the module while it was on the air dryer.
There was a temperature difference of about 9 degrees between top and bottom of the module, so the Seebeck effect was in operation.
The current from the module averaged around 11 mA, but varied somewhat over time. I recorded the current and then closed the switch. Leaving aside one anomalous reading where the current rose by 7 mA, the current rose an average of 4 mA every time the bias was applied. The effect was consistent and repeatable.
The actual current from the bias was below what my meter could measure, but simple calculation shows that it could not have been more than .67 mA with the measured V and R of the bias. The effect was actually stronger with the 1 Mohm than with the 100 Kohm, showing that only the EMF was responsible for the effect.
I haven't done voltage/power measurements at this point. I just wanted to nail down the drift current effect. Next will be to see if the actual power output is increased.
I'm using a very small bias voltage, but soon will have a better power supply and can work at more practical levels.
Fred
Hi F6FLT,
I'm getting my new power supply tomorrow. I've confirmed that I can increase the steady state power output of the thermoelectric module under the conditions already described from 146 mW to 197 mW by application of the 6.65 V bias through a 1 Mohm resistor. The power from the bias is calculated to be around 44 mW, so there is a gain of 6 mW through this process. Not much-- but using the bias in series is not ideal, nor is the bias or R value. When I get the PS I will be working with V up to 60 V, R up to 10 Mohm, with bias in parallel.
Fred
Conventionally, to obtain a current in a conductor one creates an electric field along the conductor, for example by connecting it to a battery. Here the aim is to drive the electrons along a conductor, thus obtaining this current, by attracting or repelling them by an electric field external to the conductor. By separating the control circuit from the driven circuit, this would be equivalent to the principle of induction between coils, but with the advantage of being able to pass DC current.
The current impossibility of DC current induction seems to me to be the result of a missing link, not in the theory of electromagnetism, but in the practice we have of it. The spatial gradient of the potential vector, considered in another thread, also seeks this same result.
Electrons move very slowly in a conductor, in proportion to the intensity of the current. We should therefore drive them with the same slowness. Let's quantify it.
For the current/speed correspondence, we have to go through the current density J = I/S where I is the current and S the cross-section of the conductor, and the drift velocity of electrons is given by v = J/ρ where ρ is the charge density in the conductors, which depends on the nature of the conductors. For copper, ρ = 1.4 * 1010 C/m³.
Example: 20A in 2.5 mm² wire gives us a velocity of 0.6 mm/s. As an indication, I produce here the distance travelled by an electron during one period of an AC signal. At 50 Hz, this corresponds to an oscillation of 2µm amplitude. In TV at 500 MHz, we get to the nanometre level.
Note that the drift velocity is very low compared to the thermal agitation speeds which are of the order of 105 m/s.
If, to begin modestly, we are looking to obtain a current of only 1 mA, it is in our interest to use the thinnest possible conductor, so as to increase the current density and the speed. There is magnet wire with a diameter of 0.05 mm, which would give us a current density J=10-3 / (pi*(0.025*10-3 )²)=509296 A/m². The drift velocity of the electrons would be v = J/ρ = 0.036 mm/s.
But even so, if we use a coil with a diameter of 5 cm, we will need a field rotating around it at only 0.18 Hz or about 1/6th of a revolution/s. For a mechanical realisation, such a slow rotation will have to use a stepper motor, or gears, which is not easy. But for a field rotating from quadrature signals, it is perfectly within the reach of a signal generator.
If the field rotates too fast, the electrons will not follow because of the resistance of the conductor. The question now is to optimise the coupling of the external field to the free electrons in the conductor.
Quote from: F6FLT on 2022.11.23, 10:35:26
Example: 20A in 2.5 mm² wire gives us a velocity of 0.6 mm/s. As an indication, I produce here the distance travelled by an electron during one period of an AC signal.
What if we took a superconductor. The diameter can be made small enough, and the current density and electron velocity large enough.
Quote from: chief kolbacict on 2022.11.23, 15:35:49
What if we took a superconductor. The diameter can be made small enough, and the current density and electron velocity large enough.
The only problem is that I haven't seen any in the shops at a reasonable price :).
I've fallen behind. I think that the implementation of the idea cannot be done exactly as described. An electric field external to a conductor is, at the surface of the conductor, always perpendicular.
The electric field produced by the plate around the coil will therefore have no component to drive the electrons along the conductor, only towards the surface.
But this is only true when the conductor is assumed to be perfect. What if the conductor is highly resistive? It is clear that the electric field will then be able to penetrate the conductor and thus drive the electrons as originally intended. I have the idea to use a coil made of a sheet of paper blackened by a carbon pencil, which will give us a resistive conductor that we can choose at will.
There is a lot of literature on conductors and insulators, but I can't find much information on electric fields in resistive materials, so this is an avenue to explore, even though the idea of resistance evokes the idea of losses. Sometimes we cure evil with evil :).