Physicists build circuit that generates clean, limitless power from graphene - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: October 03, 2020, 02:50:44 am
content: Another university team that are ontosomething, but I don't think that something is what they think it is.So much verbal wankery in this article, I don't know where to start.https://phys.org/news/2020-10-physicists-circuit-limitless-power-graphene.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 03, 2020, 02:52:51 am
content: I mean, the first paragraph literally describes a resistor...Ed: that press release literally has NO MENTION of the actual source article. The ScienceDaily copy gives this link at least:https://journals.aps.org/pre/abstract/10.1103/PhysRevE.102.042101Tim

author: EEVblog
author_rank: Unknown
timestamp: October 03, 2020, 03:17:12 am
content: Quote from: T3sl4co1l on October 03, 2020, 02:52:51 amI wonder where the energy is coming from? Gee, I just can't seem to figure it out...

author: DrG
author_rank: Super Contributor
timestamp: October 03, 2020, 03:51:51 am
content: https://arxiv.org/pdf/2002.09947.pdf

author: Siwastaja
author_rank: Super Contributor
timestamp: October 03, 2020, 07:26:10 am
content: What are they thinking? Graphene was the buzzword adecadeago! This can't possibly work now.

author: BravoV
author_rank: Super Contributor
timestamp: October 03, 2020, 07:59:17 am
content: Quote from: Siwastaja on October 03, 2020, 07:26:10 amIts all about cheap and low risk opportunistic move, all the inventor need is just a computer and type/make/deliver what ever they wanted in writing/video/web/publication and etc, thats all, really cheap.If the bait is bitten, hurray ... big fish, if not, nothing to loose, as simple as that.

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 03, 2020, 04:11:03 pm
content: Quote from: Siwastaja on October 03, 2020, 07:26:10 amPeople still say "Synergy"...

author: tszaboo
author_rank: Super Contributor
timestamp: October 04, 2020, 08:21:14 am
content: Quote from: EEVblog on October 03, 2020, 03:17:12 amWhile I also had a good laugh when i saw the battery, they claim this:"However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath."Even if they messed up the measurement, making a heat pump is nice.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2020, 05:42:39 pm
content: Also, note the part where the tip is moved away so that tunneling current is zero; it's under bias, but not doing work.Same as magnetic or electric deflection of an electron beam, it's affecting the system but it doesn't affect the energy level of the system, there's no power consumption.I'm not clear on what the source of energy actually is, and they don't seem to go into much discussion of it. Alas I don't know an Ito product, and I was never that great at shuffling around partials in thermodynamics...t sounds to me like a process of redistributing thermal energy by spectra. The wobble of the graphene is a low frequency effect (which also couples to ambient vibrations, although this may still be at a frequency much higher than any vibration you would expect), so the system couples phonons in that band, to electrical fluctuations in the resistors/diodes.Which is kind of like that MIT press release from... some years ago, they had a subthreshold and endothermic LED. Which as far as I know was just a regular LED, biased to V less than hν/e of the light emitted, so that it emits light -- incredibly feebly, but still detectable. In essence, it exchanges electronic thermal noise (you can imagine the terminal voltage having some variance, and the diode emits when above the threshold) for optical thermal noise (variation in that band of the visible spectrum, with equivalent temperature, if only thermal radiation extended to this wavelength in the first place).I'm still not sure how to resolve that case; a single quantum of visible light, no matter how it's emitted (there is a thermodynamic property of light in terms of collimation, étendue), carries more energy than the EM field is supposed to, at that temperature. I don't know if étendue is a strong enough effect to excuse that (is there an exponential tail associated with that as well, allowing energy to be arbitrarily high, for arbitrarily-near-zero radiance?). But it still makes sense classically, and I don't know quite how to connect that to quantum mechanics.Namely, consider the PSD in the bandwidth of the LED. Its spectral width is some fraction of its center frequency, typically a few percent. (Maybe it's even narrower at low voltages?) It could well be equal to the PSD at some baseband frequency equal to that bandwidth. That is, suppose you had an ideal optical modulator, which converts say, +/-1THz baseband, to 545 +/- 1THz (green). Then, in equilibrium, you would have equal PSD in those bands, and the mixer doesn't necessarily have to input any power to implement that. I think.The mixer is not quite a Maxwell's Demon: it's not sorting things, it's just switching back and forth at its own rate. It could deliver power in making a product, but it could also draw power in making a negative product. It's not "clean", in a sense; it definitely couples to the system under some conditions. (See also, parametric amplifier?) But the equilibrium condition stipulates that both flows are balanced, so it should be possible for the mixer to also deliver no power?Tim

author: RoGeorge
author_rank: Super Contributor
timestamp: October 04, 2020, 08:01:41 pm
content: I see nothing wrong with that idea. Should also work with a resistor, a diode and thermal noise.After all, the Brownian motion is called after the dude who discovered random grass-hooping moving pollen under a microscope, as it is shown in one of the comments (i.e. by goldeneye) on the phys.org article, quoted from wikipedia:https://en.wikipedia.org/wiki/Brownian_motionWell, to move something randomly, being it even only a grain of pollen, some energy must be spent.Anyway, the problem of our times is not the lack of energy. There's plenty of energy everywhere, way more than we could ever spend, and by now we already know how to change it from one form to another so it suits us.What we really lack in our current stage of development is not the energy, but a way to store it at a high density per volume unit, so to release it later upon wish.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 04, 2020, 09:19:41 pm
content: (In this post, I'll try to convert the salient points of the article in laymans terms. I'll comment in a separate message.)The measurements are done in a very high vacuum (10-10mbar, or about 10-12PSI), using a conductive tip (gold) brought to within a few nanometers of the sample to be measured. The sample must also be conductive, as a bias voltage is applied between the two. If the distance between the tip and the surface is 2nm or more, the electrons tunnel between the two; there is no "direct" contact wrt. electron flow. Then, the tip-surface can be treated as a variable capacitor, with the capacitance depending on the distance. Inversely, by measuring the capacitance, we obtain the distance between the tip and the surface.The sample sits on a copper grid with 7500nm by 7500nm square holes, and 5000nm thick bar supports. The tip was used only inside the holes, not moved laterally; only measuring one point on the graphene sheet. The copper grid is completely isolated, except for a connection to the bias voltage supply.The measurements are done using 1V, 15V, and a 45V bias voltage. They measured the current flowing between the bias voltage source and the tip, and the current between the copper grid and the bias voltage source. Because the currents were so small, they used two diodes of opposite polarities and very sensitive ammeters in series with each diode. They consider one the battery current, and the other the graphene-induced current.They claim they verified that the graphene-induced currents they saw with 15V and 45V bias voltages with freestanding graphene did not occur when the graphene sheet was rigid(ly mounted to the copper grid).The rest of the paper is them asserting that this shows that it is possible to extract continuous thermal power from Brownian motion in thermodynamic equilibrium without violating the second law of thermodynamics, as long as that power is dissipated in a resistor.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 04, 2020, 09:42:22 pm
content: Aside from that paper, the energy is conserved in closed systems only. As long as the system is NOT closed (or technically just very big), then enough energy exchange can be made, so we can benefit of that flow. No energy conservation laws should concern us then.Other said, while a theoretically (ideal) perpetuum mobile is impossible, we don't even need it, because a practically infinite energy machine is perfectly in our reach.Take for example the sky at night. Point an infrared thermometer to it. It will show a very, very low temperature. It's almost absolute zero in outer space. The earth is at a much, much higher temperature. This alone should be enough to fuel our world. Same during the day, the sun temp is much higher than the rest. If only we could store it (the harvested energy).We are living in a tremendous flux of energy, way more than we need at this stage.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 04, 2020, 10:41:48 pm
content: My own comments:A freestanding sheet of graphene will deform (the carbon atoms move, changing their interatomic distances) when the local electron densities on different sides of the sheet differ – meaning, if a photon or electron hits the graphene, part of the energy goes into deforming the sheet. Exactly how this happens, is quantum physics; and involves concepts like plasmons and phonons.Localized excitation from e.g. thermal photons (remember, this is in room temperature, so lots of those zipping around) and de-excitation occurs in very, very short timescales (picosecond to femtosecond range); they're so short-lived, that almost all simulations at the atomic level only consider electrons in their ground states. These are too localized in space and time to exploit, but if they deform the freestanding sheet, we can extract that energy (relaxing/straightening the sheet out at the same time) by connecting the different potentials into a circuit; the flowing current can do external work.So, no problems there.The problem in the article is the practical setup. After applying a 45V bias voltage, after 40 seconds they observed a 1.0 nA to 1.5 nA pulse of current (about 25 pW) for 10 seconds. So, let's say the excess is 250 pWs = 250 pJ ≃ 6·106eV. If we have electrons accelerated through a potential difference of 45V, we need a bit over a hundred thousand (133,000) such electrons to explain the excess.A typical photon at room temperature has 0.025 eV of energy. To account for the excess, we need 240,000,000 electrons with similar energy.Ahem-ho-hum.They do claim this only happened when the sheet was freestanding, and not when the sheet was rigidly fastened to the underlying copper grid; so, we probably should assume the excess is from the freestanding sheet and not from elsewhere in the circuit (like the diodes). Although something as simple as having a brighter light over the circuit containing the diodes could explain the difference...Here's my take:Before the experiment begins, the freestanding graphene sheet is already deformed, essentially having stored the (tiny amount of) excess energy measured in the experiment. This deforming occurs because the copper grid, even though in room temperature, means the electron density on the graphene sheet surface is uneven. (It would be interesting to do a STM scan of the surface of the sheet with 1V bias voltage. I bet the effect of the copper grid would show up, even for the freestanding sheet.)The 1V bias voltage at a single point on the sheet is not enough to deform/reform the sheet.The 15V bias voltage at a single point causes the sheet to have a thermal gradient, which in ten seconds or so reforms a small area of the sheet near the tip.The 45V bias voltage at a single point causes a larger thermal gradient, which diffuses to a larger area of the sheet, and reforms a larger area of it; but also taking a longer time.The fact that there is a "snap action" – around 10 seconds with 15V bias, and around 40 seconds with 45V bias – is interesting. It could indicate that the room-temperature deformed sheet reforms quickly when a specific temperature difference is reached; much like shape-memory alloys like NiTi, except at atomic scales only; the deformations they measured are on the order of couple dozen interatomic distances. The reason why the delay is so much longer with 45V bias, could be that the thermal gradient reaches the copper grid, with the copper grid acting as a heatsink.(Note that the thermal gradient is approximately the same regardless of whether the sheet is fixed or freestanding. I am basically assuming that they accounted the energy in and out of the system incorrectly, assuming that thermal loss was somewhere else in their circuit.)I could be completely wrong, though; I only do computational material physics, not experiments.

author: rfeecs
author_rank: Frequent Contributor
timestamp: October 05, 2020, 06:01:01 pm
content: We talked about this a few years ago, and so they're still at it:https://www.eevblog.com/forum/renewable-energy/a-potential-source-of-clean-limitless-energy/msg1407998/#msg1407998