Physicists Build Circuit That Generates Clean, Limitless Power from Graphene (2020)
news.uark.edu
news.uark.edu
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.
"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.
> 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,
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.
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."
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.