Excerpts：
"A team of University of Arkansas physicists has successfully developed a circuit capable of capturing graphene's thermal motion and converting it into an electrical current."
"The idea of harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work."
Extracting power from no gradient is definitively a perpetual motion machine. This concept fails at a high level even before diving into the weeds. No authority is needed. Closing the feedback loop would help separate the wheat (science) from the chuff (pseudoscience).
There is an awful lot of projection going on here. I'd focus on the content. Prove that extracting power from no gradient of any kind is possible. If this request doesn't set off alarm bells in your head: I think the audience knows who is out the their depth.
> first analysed in 1912 ... by Polish physicist Marian Smoluchowski. ... popularised by [Feynman] in a physics lecture at the California Institute of Technology on May 11, 1962,
When correctly shaped, graphene can harvest energy from motion, such as human body movements, and store it as electrical energy in micro-supercapacitors.
Clocks that wind themselves up from being jostled around are centuries old. But thermal energy is supposed to be maximally disordered and thus unable to be converted to a more ordered form like electricity.
I would read the article, it is easy to read and accessible.
Here's the meat though.
"Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible.
According to Kumar, the graphene and circuit share a symbiotic relationship. Though the thermal environment is performing work on the load resistor, the graphene and circuit are at the same temperature and heat does not flow between the two.
That’s an important distinction, said Thibado, because a temperature difference between the graphene and circuit, in a circuit producing power, would contradict the second law of thermodynamics."
A circuit producing power without a temperature difference contradicts the second law of thermodynamics, which is what Thibado is claiming to have done.
Hard to see how this works when Brownian ratchets don't.
Also: "Léon Brillouin in 1950 discussed an electrical circuit analogue that uses a rectifier (such as a diode) instead of a ratchet. The idea was the diode would rectify the Johnson noise thermal current fluctuations produced by the resistor, generating a direct current which could be used to perform work. In the detailed analysis it was shown that the thermal fluctuations within the diode generate an electromotive force that cancels the voltage from rectified current fluctuations. Therefore, just as with the ratchet, the circuit will produce no useful energy if all the components are at thermal equilibrium (at the same temperature); a DC current will be produced only when the diode is at a lower temperature than the resistor."
But if the diode at a lower temperature than the resistor can generate current, then the current should raise the temperature of the resistor, meaning that it will stay running.
That seems unlikely, as I understand thermodynamics. Can anyone explain?
This is pretty meaningless argument though. Ok, maybe it does not contradict the second law of thermodynamics. It still contradicts the conservation of energy though, and that's what matters!
(It also does not contradict law of conservation of momentum, Boltzmann law, and San Francisco parking rules. Who cares?)
The abstract doesn't appear to me to say anything about violating known physical law.
They are claiming it all works as theory predicts, I think.
What is missing for me is an explanation why this is in fact interesting to a layperson.
"At room temperature, micron-sized sheets of freestanding graphene are in constant motion, even in the presence of an applied bias voltage. We quantify the out-of-plane movement by collecting the displacement current using a nearby small-area metal electrode and present an Ito-Langevin model for the motion coupled to a circuit containing diodes. Numerical simulations show that the system reaches thermal equilibrium and the average rates of heat and work provided by stochastic thermodynamics tend quickly to zero. However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath."
I guess it sounds like they are saying the graphene is all wibbly-wobbly at room temperature, and applying a kind of damping mechanism temporarily produces power. Very temporarily.
I'm not quite sure why this should or should not be possible. If they say it's initially not at equilibrium though, that means they aren't suggesting new physics, right?
It is nonsense. The claim is that a machine exists that violates the 2nd law of thermodynamics (definition of a perpetual motion machine, Maxwell's Demon). This is well trodded ground.
I didn't read the whole article, but from the schematics it looks like they are exploiting thermal electronic noise and applying a half-bridge rectifier to it so it produces very low voltage power.
On one hand, it's clearly bullshit due to the extravagant title claiming to violate the 2nd law of thermodynamics. On the other hand, if a system is sufficiently small than it can violate the 2nd law, locally. It seems the tour de force in this case is that the scale can be somewhat enlarged by the very low power of thermal electronic noise.
A previous time this came up, I had the impression that what it really does is extract energy from a temperature difference between the graphene and the load, which is in principle perfectly normal even is it's a new way to arrange the details.
Edit: missed the link to the abstract.
> However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath.
So yeah, extracting power from a thermal bath sounds exactly like capturing energy as it flows down a temperature gradient.
Nope. Not reproduced since then. One of these classic "hey I've discovered an effect that is not properly isolated and contradicts brownian motion. Everything we know is probably wrong, let's publish about it rather than try to understand what we screwed up" moments.
Even in utopian depictions of the future energy tends not to be limitless. Extremely abundant maybe, but never limitless. It seems strange to even pursue it.
50 comments
[ 2.9 ms ] story [ 98.4 ms ] thread"The idea of harvesting energy from graphene is controversial because it refutes physicist Richard Feynman’s well-known assertion that the thermal motion of atoms, known as Brownian motion, cannot do work."
There's nobody to give this research group bad marks.
https://youtu.be/rckrnYw5sOA
> first analysed in 1912 ... by Polish physicist Marian Smoluchowski. ... popularised by [Feynman] in a physics lecture at the California Institute of Technology on May 11, 1962,
https://en.wikipedia.org/wiki/Brownian_ratchet
When correctly shaped, graphene can harvest energy from motion, such as human body movements, and store it as electrical energy in micro-supercapacitors.
Clocks that wind themselves up from being jostled around are centuries old. But thermal energy is supposed to be maximally disordered and thus unable to be converted to a more ordered form like electricity.
Is this clickbait? Or, is there actual basis to the claim?
Kindly, someone who knows about this space elaborate?
Here's the meat though.
"Thibado’s team found that at room temperature the thermal motion of graphene does in fact induce an alternating current (AC) in a circuit, an achievement thought to be impossible.
According to Kumar, the graphene and circuit share a symbiotic relationship. Though the thermal environment is performing work on the load resistor, the graphene and circuit are at the same temperature and heat does not flow between the two.
That’s an important distinction, said Thibado, because a temperature difference between the graphene and circuit, in a circuit producing power, would contradict the second law of thermodynamics."
Also: "Léon Brillouin in 1950 discussed an electrical circuit analogue that uses a rectifier (such as a diode) instead of a ratchet. The idea was the diode would rectify the Johnson noise thermal current fluctuations produced by the resistor, generating a direct current which could be used to perform work. In the detailed analysis it was shown that the thermal fluctuations within the diode generate an electromotive force that cancels the voltage from rectified current fluctuations. Therefore, just as with the ratchet, the circuit will produce no useful energy if all the components are at thermal equilibrium (at the same temperature); a DC current will be produced only when the diode is at a lower temperature than the resistor."
https://en.wikipedia.org/wiki/Brownian_ratchet
That seems unlikely, as I understand thermodynamics. Can anyone explain?
Current in a diode also raises the diode's temperature.
(It also does not contradict law of conservation of momentum, Boltzmann law, and San Francisco parking rules. Who cares?)
They are claiming it all works as theory predicts, I think.
What is missing for me is an explanation why this is in fact interesting to a layperson.
"At room temperature, micron-sized sheets of freestanding graphene are in constant motion, even in the presence of an applied bias voltage. We quantify the out-of-plane movement by collecting the displacement current using a nearby small-area metal electrode and present an Ito-Langevin model for the motion coupled to a circuit containing diodes. Numerical simulations show that the system reaches thermal equilibrium and the average rates of heat and work provided by stochastic thermodynamics tend quickly to zero. However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath."
I guess it sounds like they are saying the graphene is all wibbly-wobbly at room temperature, and applying a kind of damping mechanism temporarily produces power. Very temporarily.
I'm not quite sure why this should or should not be possible. If they say it's initially not at equilibrium though, that means they aren't suggesting new physics, right?
680kHz perhaps?
The first thing they should do it hook up this radio frequency “AC” to a speaker and see if it sounds like country music or traffic reports.
AC in a high impedance circuit is practically unavoidable, graphene or not.
https://youtu.be/rckrnYw5sOA
On one hand, it's clearly bullshit due to the extravagant title claiming to violate the 2nd law of thermodynamics. On the other hand, if a system is sufficiently small than it can violate the 2nd law, locally. It seems the tour de force in this case is that the scale can be somewhat enlarged by the very low power of thermal electronic noise.
Title is awful ofc but the actual scientist of course never claimed this.
Since the followup isn't "Arkansas Graphene Power 10GW plant comes online", it probably doesn't generate "clean, limitless power".
Edit: missed the link to the abstract.
> However, there is power dissipated by the load resistor, and its time average is exactly equal to the power supplied by the thermal bath.
So yeah, extracting power from a thermal bath sounds exactly like capturing energy as it flows down a temperature gradient.