Organic thermoelectric device can harvest energy at room temperature
kyushu-u.ac.jp
kyushu-u.ac.jp
Turning heat directly into electricity is one of those Trek-level technologies. Many would debate whether it is even theoretically possible, while others claim practical successes.
"harvesting energy only from the fastest of them" actually does violate thermodynamics and, if possible, would constitute the biggest revolution in physics in all of history.
Given the extremely small power levels, I expect that if it's not a hidden temperature gradient (eg between local air temperature and local radiant temperature, similar to PV) then they're actually seeing some sort of static electricity or air movement effect.
“All you have to do is harvest the hottest/fastest molecules” pretty much describes exactly what Maxwell’s Daemon is.
Now, you can see from the Wikipedia page that there is at least some debate about the topic. But, I think that generally, most physicists think that Maxwell’s Demon would violate the 2nd law, and that the 2nd law is a real limitation.
It certainly sounds like this device would violate the “metaphysics” definition of the 2nd law, “entropy always increases”. Because it sounds like it’s harvesting energy from heat for “free” (not actually energy from nothing, not violating conservation, but free in that you are not paying for the loss of entropy by increasing entropy somewhere else, which is typically “required”).
I am not a physicist, and in my layman’s understanding, I have always felt that the 2nd law seemed fishy. A lot of other people do, too. It’s called “a scientific law”, but it feels more like a philosophical “principle”. It feels different than, for example, “the law of gravity”.
But, this invention, if it is not a hoax or error, sounds world changing. 94 nW/cm2 means a milliwat for 2 square inches. That’s already usable amounts of power for tiny devices. Can you roll up a couple square meters of this stuff into something like a capacitor and get a usable “free” AA battery?
Is heat about to be free energy? No more problems with global warming? Are our refrigerators and air conditioners soon going to be a source of energy rather than a sink?
If this claim is true, then this is world changing technology available to anyone with pretty basic thin film technology…. And there are YouTubers who will be replicating this soon. Let alone real fabrication labs.
You can see why it’s reasonable to be skeptical…
This reasoning isn't convincing enough for some (non-physicist) people- there are whole forums of people working on perpetual motion machine designs, etc. that think thermodynamics is nonsense. However, thus far none of their machines have ever worked.
Although I am not a working physicist, I was trained as a physicist (a long time ago!), and assign a prior of essentially 100% to the laws of thermodynamics, from a huge amount of evidence. E.g. I am certain that either I am misunderstanding this paper, or it is simply wrong. I'm hoping someone whose physics isn't as rusty as mine will step in and explain what I am missing here.
[1] or fraud or bullshit, but let's be assume good intentions.
>But so do solar panels. A PV system turns a moving particle (a photon) into an energy gradient, a voltage.
Solar panels are not an example of a Carnot violation. As far as we know, no such examples exist.
https://en.wikipedia.org/wiki/Solar_cell_efficiency#Thermody...
I believe this isn't quite true (even though it's often repeated).
Consider that you could have an LED, at the same temperature as the PV cell, emitting light onto the PC cell, and so the PV cell would "generate" power without a temperature differential.
The Carnot cycle applies (in its initial form, at least), ONLY to generating power from temperature differentials, but PV uses the photoelectric effect, not temperature differentials.
This is not my area of expertise, but I think you can generalize the Carnot efficiency to talk about low-entropy energy sources instead of temperature differentials, but it's not quite as simple as associating a light wavelength with a temperature, because that doesn't work for radiation from something that's not a black body (like a laser or an LED).
Likely the word 'work' here is in the context of collecting or generating energy in some manner. Your example here is essentially energy transfer. In analogy what you're describing is the transfer of power from driveshaft to axle, not what is happening in the engine itself.
"At this moment, we think that the thermal energy can be supplied to the devices from the surrounding air which possesses thermal energy such as 25 meV at room temperature. The air surrounding the devices can be considered as an infinite heat bath, and the analogized conditions of steady light irradiation in a solar cell, i.e., “photon absorption,” are considered to be formed by “phonon absorption.”"
This sounds like nonsense to me- I don't think a solar cell would function without a gradient either, e.g. if the cell itself were the same temperature as the light source.
What about photons from non-thermal sources? A PV panel is able to generate electrical current from photons generated by LEDs, bioluminescence, and indirect light reflected off a cold surface.
For a “non thermal” source, the thermodynamics aren’t changed, you are still radiating the energy you put into it, and a sufficiently “hot” absorber will be unable to use the energy. The thermodynamics are the same, you just have more control over the frequency and direction of the radiation.
Each photon, no. But the distribution of the spectrum of a black body follows a pattern that depends on the temperature (and other stuff).
<bold>The important part is that the PV panel not only absorbs photons, it also emits photons. Usually the emission is much much much smaller than the light it absorbs.</bold>
If you assume that the PV panel is another black body and the sun is another black body, then the energy must flow from the hot one to the cold one.
Real objects are not perfect black bodies, so you have emission and absorcion coefficients that makes the calculation harder.
For LEDs, bioluminescence, lasers, and other sources, the calculation is harder because the distribution of light in the spectrum is different, and they usually don't match. You must consider work, entropy, and more technical stuff. But the oversimplified version is that the energy also flows from the "hot" to the "cold" one. You need a gradient of temperature or something equivalent to make the energy flow.
PS1: You can use a LED as a light detector, like a photodiode. It's somewhat the inverse effect of using a PV panel as a lamp.
PS2: I know that <bold></bold> doesn't work in HN, but that it's the important paragraph.
I am banking on the author not fully understanding their own experiment, rather than a complete overturning of thermodynamics. I would be very excited to be wrong, though.
Oh, I see it now, you're suggesting that it could just passively create a gradient that could produce power in a more conventional way, like via an engine, until I guess the device kicks in again and re-establishes the gradient (producing more power of its own in the process). Yes. That does sound like impossible free energy.
Or perhaps requiring some kind of catalyst that is rendered into a higher energy state which is functionally useless for its purpose as said catalyst?
Either way, we’ve got some interesting sci-fi concepts to work with!
My thermodynamics lectures are some 20 years in the past, so my memory is a bit rusty, but iirc you need "free energy", that is, usable energy in the form of a low-entropy energy source, which is usually a temperature gradient (but could also be a radiation source or something else).
To get to these results, you have to do statistics of large numbers, so it's theoretically possible to violate this on the nano scale.
The optimist in me hopes that we've found a scalable way to exploit this, the pessimist/skeptic in me says it's another cold fusion moment.
They don't claim "we found a scalable way to violate the second law of thermodynamics", but instead make very specific claims about what they measured, and that they produced 94 nano-Watts per square centimeter. They don't even mention entropy.
This feels more like they know exactly how unbelievable their results sound, and that they are very careful to not overstate anything.
They already have miniature kinetic energy generators, now they can pair with heat difference generators (air vs animal body temp)