Thermodynamic magic enables cooling without energy consumption

Thermodynamic magic enables cooling without energy consumption
Theoretically, this experimental device could turn boiling water to ice, without using any energy. Credit: Andreas Schilling, UZH

Physicists at the University of Zurich have developed an amazingly simple device that allows heat to flow temporarily from a cold to a warm object without an external power supply. Intriguingly, the process initially appears to contradict the fundamental laws of physics.

If you put a teapot of boiling water on the kitchen table, it will gradually cool down. However, its is not expected to fall below that of the table. It is precisely this everyday experience that illustrates one of the fundamental laws of physics—the second law of thermodynamics—which states that the entropy of a closed natural system must increase over time. Or, more simply put: Heat can flow by itself only from a warmer to a colder object, and not the other way round.

Cooling below room temperature

The results of a recent experiment carried out by the research group of Prof. Andreas Schilling in the Department of Physics at the University of Zurich (UZH) appear at first sight to challenge the second law of thermodynamics. The researchers managed to cool a nine-gram piece of copper from over 100°C to significantly below without an external power supply. "Theoretically, this experimental device could turn boiling water to ice, without using any energy," says Schilling.

Creating oscillating heat currents

Thermodynamic magic enables cooling without energy consumption
Thermodynamic Magic: A simple technique allows to cool hot materials below ambient temperature without external intervention, seemingly defying the laws of physics. Credit: A. Schilling

To achieve this, the researchers used a Peltier element, a component commonly used, for example, to cool minibars in hotel rooms. These elements can transform into temperature differences. The researchers had already used this type of element in previous experiments, in connection with an electric inductor, to create an oscillating current in which the flow of heat between two bodies perpetually changed direction. In this scenario, heat also temporarily flows from a colder to a warmer object so that the colder object is cooled down further. This kind of "thermal oscillating circuit" in effect contains a "thermal inductor". It functions in the same way as an electrical oscillating circuit, in which the voltage oscillates with a constantly changing sign.

Laws of physics remain intact

Until now, Schilling's team had only operated these thermal oscillating circuits using an energy source. The researchers have now shown for the first time that this kind of thermal oscillating circuit can also be operated "passively", i.e. with no external power supply. Thermal oscillations still occurred and, after a while, heat flowed directly from the colder copper to a warmer heat bath with a temperature of 22°C, without being temporarily transformed into another form of energy. Despite this, the authors were also able to show that the process does not actually contradict any laws of physics. To prove it, they considered the change in entropy of the whole system and showed that it increased with time—fully in accordance with the second law of thermodynamics.

Potential application still a long way off

Although the team recorded a difference of only about 2°C compared to the ambient temperature in the experiment, this was mainly due to the performance limitations of the commercial Peltier element used. According to Schilling, it would be possible in theory to achieve cooling of up to -47°C under the same conditions, if the "ideal" Peltier element—yet to be invented—could be used: "With this very simple technology, large amounts of hot solid, liquid or gaseous materials could be cooled to well below room temperature without any energy consumption."

Thermodynamic magic enables cooling without energy consumption
Thermodynamic Magic: A simple technique allows to cool hot materials below ambient temperature without external intervention, seemingly defying the laws of physics. Credit: A. Schilling

The passive thermal circuit could also be used as often as desired, without the need to connect it to a power supply. However, Schilling admits that a large-scale application of the technique is still a long way off. One reason for this is that the Peltier elements currently available are not efficient enough. Furthermore, the current set-up requires the use of superconducting inductors to minimize electric losses.

Established perceptions challenged

The UZH physicist considers the work more significant than a mere "proof-of-principle" study: "At first sight, the experiments appear to be a kind of thermodynamic magic, thereby challenging to some extent our traditional perceptions of the flow of heat."


Explore further

It's a one-way street for sound waves in this new technology

More information: "Heat flowing from cold to hot without external intervention by using a 'thermal inductor'" Science Advances, DOI: 10.1126/sciadv.aat9953 , https://advances.sciencemag.org/content/5/4/eaat9953
Journal information: Science Advances

Citation: Thermodynamic magic enables cooling without energy consumption (2019, April 19) retrieved 19 October 2019 from https://phys.org/news/2019-04-thermodynamic-magic-enables-cooling-energy.html
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Apr 19, 2019
Even if we end up needing to have superconducting materials to make this work, space-based industry will benefit enormously from this kind of thermal transfer efficiency. Once we figure out how to cool the superconducting materials directly, that will let us use this virtually anywhere. Your freezer could be helping to warm your food and vice versa.

Apr 19, 2019
Something doesn't add up. Doesn't this suggest one could create an infinite energy device? Cool things without energy, then use the temperature difference to drive a motor? That can't be right.

Apr 19, 2019
This raises more questions than it answers.

Apr 19, 2019
Something doesn't add up. Doesn't this suggest one could create an infinite energy device? Cool things without energy, then use the temperature difference to drive a motor? That can't be right.


No. They've just demonstrated an "inductor" for heat flow, like a heavy wheel rolling up a hill some way before it runs out of momentum. A peltier element creates a current from a flow of heat, and a flow of heat out of a flow of current, so a stack of peltier elements cleverly connected can be used to create a "wave" of heat that has the equivalent of inertia, or inductance as analogous to the electrical component. It tends to keep the current going in a single direction, which can be used to generate high voltages, or high differences in temperature in this case.

It can be useful, but it won't break the laws of physics.

Apr 19, 2019
@Eikka is correct. It's also important to note here that there is indeed electrical energy flowing; the Peltier cooler both generates electricity from a temperature difference, and generates a temperature difference from an electrical flow, and it oscillates between these states with no external power applied. This is fairly ingenious, and does not violate any laws of physics, though it's certainly not straightforward. It's by an appropriate selection of Peltier cooler, resistor, and inductor that this occurs. For EEs in the audience, it's important that the resistor not swamp the combined impedance of the Peltier cooler and inductor. This hints at the mechanism at work.

Apr 19, 2019
This reminds me of a voltage doubler. Only capacitors and diodes are necessary to stack up two potential differences, each of which is composed of only a portion of the total charge moving around the entire circuit. Just as voltage is not equivalent to energy -- it must be multiplied by charge -- so temperature is not energy either; it must be multiplied by number of molecules.

(I might be getting this wrong, and would appreciate any corrections if that is the case.)

Apr 19, 2019
"This reminds me of a voltage doubler."
Or, cascaded, to a Cockroft-Walton generator. Which will get there, but you've time to stroll down the corridor and have a leisurely mug of coffee or tea while the charges build on each stage...
;-)

Apr 19, 2019
@Ralph, never forget that a voltage multiplier is a current divider. E = VI and like that.

Apr 19, 2019
The writer puts emphasis on respecting the laws of thermodynamics. I think that the bigger issue is whether or not the process works. Breaking a law if physics shouldn't be treated like a crime. If it works it works

Apr 19, 2019
Why insist thermodynamics is wrong when the theory and experiment don't violate it?

Apr 19, 2019
which states that the entropy of a closed natural system must increase over time.


According to Boltzmann's formulation the macrostate (eg the closed system) is made up of the microstates (the total number of these is 'S', Entropy). The number of microstates can't change is a closed system of, say, a gas, and so entropy can not change (rise or fall) unless the number of microstates changes.

Statistical mechanics states that there are no exclusive configurations in phase space and so all configurations, including the initial condition, will recur with some frequency in a closed system.

Thus the statement quoted is not true of one of the standard models of entropy, a gas compacted in one corner of a closed (thermally isolated) system. The gas does expand but the configuration of the compacted gas, according to Boltzmann, has the same probability of occurring as any other configuration.

Blanket statements must either be qualified or must always be true.

Apr 19, 2019
"Heat can flow by itself only from a warmer to a colder object, and not the other way round."

This is not quite true. Heat flows in both directions (from hot to cold and cold to hot) but hotter atoms are more excited and emit energy more frequently and so the higher frequency results in a *net flow* from hot to cold.

Saying that heat can not flow in the opposite direction requires some law of nature to prevent it, and there is none. Frequency and probability rule here, there is no governing mechanism that controls the general direction of flow, simply a higher frequency of thermal emission events in the hotter body....

Apr 19, 2019
Future solution for global warming !?!

Apr 20, 2019
the current set-up requires the use of superconducting inductors to minimize electric losses

Always a catch, isn't there. Of course, clearing that "little" hurdle, would be far more valuable than this invention.

Apr 20, 2019
There's almost no such thing as a closed system on Earth, so apparent local violations of the Second Law don't bug me that much.

What bugs me is the presumption that each heat-to-electrical and electrical-to-heat transformation through the Peltier device appears to be lossless. And the electrical energy inserted into the superconductor also appears to be lossless. Once electrons are *in* the superconductor, okay - but electrons supplied by non-superconducting circuits? How is it that there is no electrical cost to operating the experiment?

I'm no expert in thermodynamics, but this smells funny to me.

They also didn't explain how they verified that there was no violation of the Second Law. They could have explained where entropy progression was preserved. But they didn't.

Nope. This looks like another cold fusion/perpetual motion bit of nonsense to me. It will be interesting to see if anyone can replicate their results. I'd bet a dollar no-one can.

Apr 20, 2019
What bugs me is the presumption that each heat-to-electrical and electrical-to-heat transformation through the Peltier device appears to be lossless.
Incorrect. energy is lost and in fact this energy loss is sufficient to strongly mute the effect, according to the article:
According to Schilling, it would be possible in theory to achieve cooling of up to -47°C under the same conditions, if the "ideal" Peltier element—yet to be invented—could be used

Apr 20, 2019
Guys. It's a thermal OSCILLATOR. It doesn't stay at that low temperature.

Here's the paper
https://advances....53?rss=1

From the abstract
We describe the equivalent of a "thermal inductor," composed of a Peltier element and an electric inductance, which can drive the temperature difference between two bodies to change sign by imposing INERTIA on the heat flowing between them, and enable continuing heat transfer from the chilling body to its warmer counterpart without the need of an external driving force

(caps mine)

If you let it run it will end up at equilibrium tmeperature.

Apr 20, 2019
@antialias, but you don't let it run. According to the paper,
In this way, the electronic oscillator circuit reaches the typically very large time scales encountered in thermal systems (i.e., seconds, minutes, or even longer).
Read the paper. How long you wanna let it run? Maybe a cunning selection of operation periods would help.

Apr 20, 2019
Good God Guys&Gals just look at the headline and the pictures. This is obviously an April Fool's joke that was published a little late. The process is a little easier to understand if you just use the stored energy as a power source. Thus the 100c degree copper will produce x amount of joules of energy via the Peltier device which can be stored via any method you choose. You can then let the copper and the Peltier device naturally cool to room temperature and then connect the stored energy device using the stored power to cool the copper below room temperature.

This is a one time deal utilizing the original stored energy in the copper and NOT sustainable due to losses in the Peltier device.

Apr 20, 2019
Breathless claims about cooling that costs no energy are a joke, yep, yep. The only question is whether the joke was meant to be humorous, or meant to attract credulous investors for scamming purposes.

Apr 20, 2019
The headline is representative of the free ride mentality of today's culture. Yup, free medical care, free education, free housing all paid for by someone else.

Apr 20, 2019
Cooling with heat is not new. The first home refrigerators were powered with a natural gas heating element.

Apr 20, 2019
Read the paper. How long you wanna let it run? Maybe a cunning selection of operation periods would help.

Sure, but you're just shunting the heat energy into something else (driven by the inertia of the created magentic field). That will relax eventually and rewarm the sample.
Unless you physically remove the peltier element and let it warm something else - which takes a lot more energy than the cooling process - it's just going to warm the sample back up for the next oscillation.
No free lunch here (though I'm sure there will be applications where microsecond cold peaks will be useful).

They handily even cite Clausius in their own article:
a flow of heat from cold to hot must be associated with "some other change, connected therewith, occurring at the same time"

Apr 20, 2019
This reminds me of a voltage doubler. Only capacitors and diodes are necessary to stack up two potential differences, each of which is composed of only a portion of the total charge moving around the entire circuit. Just as voltage is not equivalent to energy -- it must be multiplied by charge -- so temperature is not energy either; it must be multiplied by number of molecules.

Electricity, which is measured in watts, is not energy per se, it is just a specific kind of energy. There is also kinetic energy, mechanical energy, chemical energy, nuclear energy, even gravitational energy. Which is why energy of all kinds is generally measured in joules.
Temperature is indeed not energy, it is just a measure of the basest form of energy : heat.

Apr 20, 2019
The only thing magical here, is that, should you be tempted to invest in it, then you can watch your money disappear.

Apr 20, 2019
With a cycle time in minutes, it seems to me something can be worked out. Have you read the paper yet? They specifically mention getting the cycle times well out of the millisecond range and up into
seconds or minutes
. The tradeoff is that the difference between the cold and hot sides must be lowered to get these longer cycle times.

Apr 21, 2019
Nice effect, though if it will find a use is an open question.

Doesn't this suggest one could create an infinite energy device?


How can you ask that when the article notes that the paper show that the system entropy increases over time? Increasing entropy means no free lunch, you are operating some irreversible process that shuttles energy into some form that cannot become useful work.

They also didn't explain how they verified that there was no violation of the Second Law. They could have explained where entropy progression was preserved. But they didn't.


Of course they did, the article even mentions that the scientists did it, and it is a separate section of the paper - it is curious how you could miss it. The experiment would have been amazing if it broke a law and it would have been unpublishable in peer review without checking for consistency with physics.

The paper itself notes when they do it that it is surprisingly simple.

Apr 21, 2019
They actually give a four-cycle interpretation of their results. It's quite an interesting paper.

Apr 21, 2019
I f they just replace the inductor (energy storage device) with another Peltier device they could have continuous below room temperature cooling based on a 100c waste heat source.

Apr 21, 2019
The largest inductor ever made was 1000 henrys. Thus the 50 henry unit used in the experiment will be quite large and heavy because it will need a huge iron core.

Apr 21, 2019
OK please ignore my last post. a 50 henry inductor at low currents is not that large or heavy.

This was a google search gone bad.

Apr 21, 2019
This is very interesting. I've always been interested in the potential the peltier effect but I have one question about the possibility of lowering the temperature of a liquid below room temperature. When room temperature water evaporates doesn't that take energy to make the water vapor which would bring the temperature down? Or is there something I'm not thinking of? If I would apply a fan to a shallow pool of water could that bring it below ambient temperature? Thank you.

Apr 21, 2019
There are in fact evaporative air conditioners called "swamp" or "sump" coolers that you can buy that use exactly this latent heat principle to draw heat from the air before recirculating it.

Apr 21, 2019
Statistical mechanics states that there are no exclusive configurations in phase space and so all configurations, including the initial condition, will recur with some frequency in a closed system.


Not necessarily. It is easy to construct, at least mathematically, a closed system that cannot return to its initial condition once set in motion.

You take three gears, first rotating at 1 revolution per second, the second rotating half as fast, and the third rotating at 1:pi to the first. They will never align the same way again because pi is not evenly divisible by two. They will repeat an infinitely many number of alignments that are almost, but not quite, the same as the initial one.

Apr 21, 2019
@Eikka, that's probably overstating the case a bit. I'd think there'd be a period over which cycle replication would occur because of the gear teeth. If you eliminated the teeth on the gears however, I expect you'd be correct, even not considering any slippage.

I will also say that in the limit of smaller and smaller teeth your conjecture would be more and more true, with the repetition period becoming longer and longer. It might be tricky, though, to make a gear with pi teeth.

Apr 21, 2019
If I would apply a fan to a shallow pool of water could that bring it below ambient temperature? Thank you.


Yes. If you insulate the pan from below and shade it from above, fanning it with air will bring the temperature down to the dew point, which is usually some 10-15 degrees below the ambient temperature, depending on how humid the air is.

If it's not too hot and humid, you can reach fridge temperatures easily. +20 C and 50% relative humidity, and a clay pot soaked in water gets to about +10 C on the inside in a breeze.

Apr 21, 2019
@Eikka, that's probably overstating the case a bit. I'd think there'd be a period over which cycle replication would occur because of the gear teeth. If you eliminated the teeth on the gears however, I expect you'd be correct, even not considering any slippage.


I don't see how that would make a difference. I didn't specify the gears would be meshed to each other, just that they have specific ratios of rotation.

After all, you can't make a gear with multiples of pi teeth to mesh with the first gear. It's not physically possible that way. The point was just to illustrate a system that can never return to its initial configuration, or to any exact configuration for that matter. It's not given that there isn't some ratio or relationship in the laws of physics that follows some n:pi or n:e etc. ratio that would make for systems with infinite variation and no repetition of states.

Only thing is, if those states become quantized to a limited number for some reason.


Apr 21, 2019
Though even if the system was quantized to discrete states, then the underlying "law" would still cause those states to follow a non-repeating pattern over time. You get to the same configurations, but the interval is not cyclical and therefore, there will be infinitely long periods of time while some states just won't re-appear.

KBK
Apr 21, 2019
Sometimes we forget that transistors are quantum devices.

Apr 21, 2019
After all, you can't make a gear with multiples of pi teeth to mesh with the first gear. It's not physically possible that way.
Yes, that was what I was getting at.

Although if you wanted to get really baroque, I'd be interested to see the math of a gear with pi teeth and gaps to make up the difference. That might be an interesting problem.

Apr 22, 2019
@Da Schneib
Recently I found a gear ratio that is close to pi. 355 teeth mated to 113 teeth. Other people have known about it before.

Apr 22, 2019
@Len, still not meeting @Eikka's specifications. Close though.

Apr 22, 2019
Yes, a gear train with a 1:pi ratio is not realizable unless you have infinite teeth. Fortunately, that's called a CVT.

IF it is truly continuously variable, then it must pass through the ratio of 1:pi - albeit locating it would require infinite precision. Regardless, it is not physically impossible to attain - just impossibly difficult for any practical means.

Other geometric constructions might work as well. It doesn't need to be a gear train - it could be pendulums with one arm of length 1, another of 2, and a third of Pi. That too, once set in motion will never return to its original configuration because the periods of the pendulums aren't divisible with each other. This is closer to fundamental systems in physics where things tend to be described in terms of oscillators.

Apr 22, 2019
The little slips when the gaps in the pi gear aren't quite engaged with the other gears should probably give the effect you are thinking of, @Eikka, though I wouldn't care to state it without doing the math.

Apr 22, 2019
@Eikka "You take three gears, first rotating at 1 revolution per second, the second rotating half as fast, and the third rotating at 1:pi to the first. They will never align the same way again because pi is not evenly divisible by two. They will repeat an infinitely many number of alignments that are almost, but not quite, the same as the initial one."
I think part of your explanation is lacking. You say "because pi is not evenly divisible by two." How about 3 instead of pi. Three is not evenly divisible by two yet a gear set made with 1:3 will repeat its alignment.

Apr 22, 2019
@Eikka A little more. How about a ratio of 1 to 3 1/3. Like 12:40.

Apr 22, 2019
Statistical mechanics states that there are no exclusive configurations in phase space and so all configurations, including the initial condition, will recur with some frequency in a closed system.


Not necessarily. It is easy to construct, at least mathematically, a closed system that cannot return to its initial condition once set in motion.


Or a system that is unlikely to, such as a chaotic system. But while I cannot see the source to the claim, it must be a blocked troll, it seems to confuse the notion of ergodicity - that a time average and a space average (of some function) is the same almost everywhere - and ergodic system recurrence - that a subset will eventually revisit itself - with an absolute version. Chaotic and irrational systems mix, so they are ergodic, while for instance a rational gear system is not [ https://en.wikipe...c_theory ; see the rotation example].

I would say that the troll got it "almost everywhere" but not really. =D

Apr 22, 2019
But here is the thing, implied by the rational/irrational rotation example. Ergodicity and integrability are opposites [ https://en.wikipe...e_system ]. So we already know that ergodicity is not the only "nice" system property (that we can use to quantify with). The troll seems to jump from (irrelevant to the discussed open system phenomena) a closed system to equilibrium system (which it will eventually be) to ergodicity.

But ergodicity is rare and just one of the pillars ("argument") of an analysis that tries to motivate the fundamental postulate of statistical mechanics that underlies the grand canonical ensemble construction [ https://en.wikipe...echanics ]. "This approach has limited applicability, since most systems are not ergodic." The one pillar used in textbooks such as "Statistical Physics" by Mandl is - if memory serves - the general principle of indifference that underlies classical probabilities.

- tbctd -

Apr 22, 2019
- ctd -

And since we have microstate reversibility (which is why we can have equilibrium reactions in the first place), we can use the number differences between microstates in macrostates to track irreversibility (entropy, of "accessible microstates in a macrostate"). That is a consistency argument for the principle of microstate indifference.

In any case, it works, in the same way that it works in classical probability theory, it is an acceptable and useful axiom. Ergodicity is more of an observation and works too, when it is observed (rarely).

Apr 29, 2019
How about 3 instead of pi.


3n / 2 will eventually become an integer number of rotations and align with the other gears, whereas pi*n / 2 will not.

ergodicity


That's too esoteric for the point.

The original claim was that statistical mechanics somehow demands entropy to reverse because the system will eventually return to its original configuration - i.e. a broken wineglass will jump up from the shards and repair itself given enough time. It's sufficient to say that there are configurations which simply cannot return to their original configurations once set in motion, so the claim is clearly unjustified.

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