Organic thermoelectric device can harvest energy at room temperature
(kyushu-u.ac.jp)40 points by geox 15 hours ago
40 points by geox 15 hours ago
Nature Communications... a good journal but not where I would expect them to publish what appears to be (if I'm not misunderstanding- and I probably am/must be) the most surprising experimental result in the history of physics
It seems to me that the authors are pretty cautious.
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.
Title misses the big story: "power generation ... without a temperature gradient".
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.
Indeed, I am really skeptical this is possible- it would seem to violate the laws of thermodynamics…
If the paper's claim is correct, it would literally be the creation of Maxwell's Daemon.
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.
I wouldn't hold your breath on being wrong. A device that converts heat into electricity without a gradient is a perpetual motion machine. Consider what would happen if you popped such a device on one side of a thermoelectric plate, and used its output to power a heater on the other side of the plate. The arrangement would permanently maintain a gradient across the thermoelectric plate - free electricity forever!
But so do solar panels. A PV system turns a moving particle (a photon) into an energy gradient, a voltage. So the concept of using another moving particle, this time a hot molecule, doesn't seem totally impossible. If one understands heat as being molecules moving at variety of speeds, harvesting energy only from the fastest of them wouldn't violate thermodynamics. It can be understood as taking advantage of the temperature gradients across the gaps between individual molecules.
It sounds like you have basically given a formulation of Maxwell’s Demon https://en.wikipedia.org/wiki/Maxwell%27s_demon
“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 is false. Solar panels do not violate the laws of thermodynamics. Generally the sun is quite a bit hotter than the environment in which the solar panels operate, which are the correct temperatures to compare in this case.
"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.
>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...
This is the same argument the authors make to reviewer #3:
"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.
No, that still violates thermodynamics.
Thermodynamics says "no", at least on macroscopic scales.
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.
Can't wait to strap some of these to the side of my desktop or the bottom of my laptop and make use of that waste heat. I'm sure I can do something or other with the approximately 2 mW I'll generate.
2 mW would work better than Sony's generator in some cases.
2mW would require about 1.5m² of area. I could maybe see this being used to pull a little bit of energy out of a room to charge batteries or capacitors to run sensors or other low power devices in short bursts. But you could harvest more power just by turning a hand crank generator for a few minutes. An average solar panel is like 10k times more efficient. I could still see some sort of use for it, maybe for being embedded into floors and ceilings of buildings to passively run sensors. There would be a small cooling effect on a room with enough of it.
Oh, if only it were that powerful! Their best result produced 94 nanowatts per square centimeter, or 0.94 milliwatts per square meter.
Sounds like a great idea for wildlife tracking.
They already have miniature kinetic energy generators, now they can pair with heat difference generators (air vs animal body temp)
Source Nature Article: https://www.nature.com/articles/s41467-024-52047-5