
New Material Breaks World Record Turning Heat into Electricity - ragerino
https://www.tuwien.at/en/tu-wien/news/news-articles/news/new-material-breaks-world-record-turning-heat-into-electricity/
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grecy
I've always wanted to build a little hobby project where I put TECs on top of
my wood stove and have a radiator outside with coolant to get a nice big heat
difference (maybe 100C to 200C) across them and make power in winter when
solar isn't so great in the Yukon.

I know it won't be a massive amount of power, but given it will be 24/7 for
about 6 months of winter when the wood stove runs, I think it will be a useful
amount.

Does anyone know where I can buy TECs that will handle extremely high
temperatures like this?

All the ones I see say they're rated at about a max temp delta of ~67C-72C

~~~
arghwhat
You'd be actively cooling your wood stove by _much_ more than the power you'd
extract, and you won't get more than enough to charge a phone or laptop. TECs
are just terrible.

You'd get much better result by making a small steam plant with the same
setup: boil water on stove, drive plant (turbine or piston), condense outside,
repeat.

However, if you _really_ want to do this with TECs, stack them to lower the
per-unit temperature differential, or distribute the heat energy over a larger
area and run them in parallel.

~~~
learc83
A small stirling engine would be easier and safer than a steam setup.

~~~
8bitsrule
The good ol' Stirling engine was tried out -- at a few locations in the US
Southwest 10 years back -- to generate megawatts of solar-powered electricity
(25kW per engine) at the focus of parabolic mirrors.

It got beat out by subsidized Chinese-produced PV panels (SES was forced into
bankruptcy).

[https://en.wikipedia.org/wiki/Applications_of_the_Stirling_e...](https://en.wikipedia.org/wiki/Applications_of_the_Stirling_engine#Solar_power_generation)

[https://en.wikipedia.org/wiki/Mount_Signal_Solar](https://en.wikipedia.org/wiki/Mount_Signal_Solar)

~~~
abdullahkhalids
My senior year project ten years ago was exactly this - solar thermal + a
Stirling engine. When we started the project, we estimated it 20% or so
cheaper than solar PV. In that one year solar prices halved or so, leaving us
at a dead end.

I ended up consulting with leather plant for their hot water needs via solar
thermal. At least that is still viable.

~~~
8bitsrule
Interesting. I just learned about that energy combo, and Stirling also makes a
lot of sense for someone with a non-solar heat source!

Amazing how China came along at the time it did. The hardball politics aimed
against US solar startups since Carter has been a fascinating tale with little
mainstream coverage.

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jcims
Every time some phenomenon arises from a recipe of fairly typical materials I
wonder what other surprises nature has in store for us.

The idea that the crystalline structure plays a large role in the bulk thermal
conductivity of the material is kind of mind-blowing at first and then
retrospectively obvious.

~~~
adw
I am twenty years removed from it, but I used to be well-informed on this kind
of thing; I have a PhD in mineral physics.

Let's see how well I can explain this (haven't read the article, yet, sorry!
Waiting for a plane...)

So you're no doubt familiar with the physics of a vibrating string; it
resonates at wavelengths (length of string, 2 * length of string, 3 * length
of string... n as n->inf). So you can express any vibrational state of the
string as sum(intensity * wavelength); so you can represent the state of the
string as a vector of intensities on a basis of allowable vibrations of the
string.

Let's call these _vibrational modes_. Let's assume occupancy of these modes is
quantized. It's (sort of...) the same as energy levels of atomic orbitals in
electronic structure, if you remember that from chemistry classes; the way
it's _not_ the same is important (bosons vs fermions) but not at this level of
handwaving :-)

So this is how solids store energy, and we call this energy "heat".

A reasonable approximation for a crystalline structure is balls – point masses
– connected by springs, where the springs are covalent bonds, plus
electrostatic effects between point charges. Intuitively, you can follow that
the same kind of _vibrational spectrum_ will arise from this arrangement (in
the same kind of way; the solutions of the differential equation of this
system of forces under periodic boundary conditions). So _materials_ have
resonant frequencies in the same way _guitar strings_ do.

Therefore, this vibrational spectrum defines the thermal behavior of a
material; heat capacity, thermal conductance, etc etc etc etc. Each of these
vibrational modes is also tied to a _collective motion_ of the particles in
the material, which (if sufficiently violent) will tear the structure apart –
there's the solid-to-liquid phase transition – or, more subtly, if lost will
_lower the symmetry_ of the crystal structure, which gives rise to solid-to-
solid phase transitions (an example would be alpha to beta quartz, which will
crack your crockery if you leave it in the oven on a cleaning cycle;
[https://en.wikipedia.org/wiki/Quartz_inversion](https://en.wikipedia.org/wiki/Quartz_inversion)).

There's a lot of depth here, as you can imagine!

~~~
correct_horse
I think you meant to say length of string, length of string / 2, length of
string / 3, ...

[https://en.wikipedia.org/wiki/Harmonic](https://en.wikipedia.org/wiki/Harmonic)

~~~
adw
Indeed I did! Thank you. (This is what happens when you write in a hurry.)

~~~
mkagenius
Hope you had a nice flight. Happy new year.

~~~
adw
One leg down, the long one to go...

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comicjk
Just to clarify why these aren't used everywhere: heat-to-power devices act as
insulation (compared to just letting the heat escape). If you have something
that you're trying to keep cool, like a CPU, a system that shunts heat
straight to the surroundings will always give better cooling than a system
that puts layers in between. Contrariwise, if you have a need for electricity,
mechanical heat engines will almost always be more efficient. Solid-state
heat-to-power only makes sense in a narrow set of cases which aren't suitable
for direct cooling or heat engines.

~~~
Matumio
But there are some pretty cool applications. Apparently the heat difference
between a buried water-pipe and the surrounding earth is already enough to
power a wireless sensor, which can transmit data to localize leaks, for
example.

~~~
m463
Voyager 2 and 1 are powered by thermocouples and a chunk of plutonium.

(I ordered them that way because Voyager 2 was launched first)

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s_Hogg
What does the level of performance indicated here likely mean in terms of the
efficiency of, say, a thermal energy plant of some description? How far is the
needle shifted for an end user?

~~~
icegreentea2
From mucking about with the device efficiency formula from wiki
([https://en.wikipedia.org/wiki/Thermoelectric_materials#Therm...](https://en.wikipedia.org/wiki/Thermoelectric_materials#Thermoelectric_Figure_of_Merit)),
and a change of zT from 2.5 to 5, we see a maximal possible efficiency
increase of 38% (when T_c == T_h).

Wiki also tells me that the best TEG modules currently lock in around 8%, so
we're looking at like 10-11% at best with the new material.

So from a bulk scale electricity standpoint... the needle probably hasn't
shifted at all. From a small scale? In the IoT like applications (as mentioned
in the press release), that extra 30-40% is nothing to sneeze at.

~~~
amluto
You have some kind of error here: with T_c = T_h, not only does Wikipedia’s
formula give 0% efficiency, but it _must_ : any power at all generated with no
temperature difference would make a perpetual motion machine.

~~~
abdullahkhalids
For T_c=293 and T_h=303, you get efficiency = 1.4% for zT=5 and efficiency =
1.0% for zT=2.5. So about a 40% relative increase as OP calculated and
negligible absolute change.

~~~
amluto
Improving from 1% to 1.4% is a _huge_ improvement. It’s 40% more cooling for a
given power input or 40% more power output for a given amount of heat
consumed. Alternatively, it means you consume only 1/1.4 the resources to
achieve your goal.

This does not imply that 1.4% efficiency is enough to be useful for most
applications, of course.

------
tosh
paper:
[https://www.nature.com/articles/s41586-019-1751-9](https://www.nature.com/articles/s41586-019-1751-9)

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data-wrangler
This would be an even bigger deal for remote spacecraft that rely on the heat
from on-board nuclear reactors.

~~~
wcoenen
I think you are thinking about an RTG instead of an actual reactor.

~~~
RL_Quine
Some space craft have actually had full reactors on them believe it or not.

~~~
wcoenen
There were indeed real nuclear reactors with thermoelectrics being launched in
the cold war.

However, thermoelectrics have an efficiency well below 10% (maybe a bit better
with this improvement but not much). For that reason, future reactors in space
will likely use Stirling engines instead.

~~~
mechhacker
Correct. Space stirling designs* (and tested engines) have been much more
performant than the RTG designs

*I spent part of my career working on these devices and saw many of them running in labs

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marius_k
Could this also be used to reverse electricity into cold-heat gradient with
high efficiency?

~~~
Dylan16807
If you have a very small cooling job, yes. Anything above a handful of thermal
watts is still better off using a compressor.

~~~
hinkley
We were talking just the other day about back-side power distribution in ICs.
Basically you bury the power rails really deep, lap the chip down to half a
micrometer, and add through vias to ge to the rails.

So now you’ve got a very thin chip and all the power comes in on the side with
pretty much nothing else on it. I wonder if you mount the chip backside up,
put these little peltier devices on the hot spots, if you can maintain a
higher heat transfer rate.

~~~
Dylan16807
The thing is, a chip generally cools just fine with heat pipes and fins up to
200 or more watts. And the built-in heat spreader gets rid of hot spots very
effectively. At that power level a peltier tends to be worse than useless,
even if you're putting enormous amounts of power through it. Even if you
double the efficiency it's still a bad option.

~~~
forgotmypwd123
Overclocked threadrippers can hit 500W[1]. I can see peltiers and 'vapochill'
style phase-change cooling making a comeback...

1\. [https://www.anandtech.com/show/13124/the-amd-
threadripper-29...](https://www.anandtech.com/show/13124/the-amd-
threadripper-2990wx-and-2950x-review/13)

~~~
Dylan16807
Phase change yes. Or water chillers.

I can't imagine why anyone would be _more_ inclined to use a peltier as
wattage increases. Higher wattages make that idea progressively worse unless
you have some very specific and strange requirements.

~~~
hinkley
Are you talking about the giant Peltiers that flopped in the late 90's and
early 00's? Nobody is talking about that. I'm talking about micron, maybe
millimeter-scale peltiers to increase the thermal conductivity of the absolute
worst spots on the chip. That may mean a particular ALU, or it could mean
circuits with far more layers than we can manage now (due to yields and
thermal limitations)

~~~
Dylan16807
> the absolute worst spots on the chip. That may mean a particular ALU

The worst spots aren't much worse than the median spots (over calculating
silicon, not cache). Anything big enough to be a hot spot, like a big ALU, is
big enough to represent a large portion of your power budget. The main goal is
to get all the heat away from the chip, and putting peltiers on a large
portion of the chip gives you more heat to take away. For anything
significantly smaller than that, the heat bleeds out without the need of a
peltier. There might be a middle ground where peltiers could make a real life
difference, but I'm skeptical.

> or it could mean circuits with far more layers than we can manage now

That sounds like you're cooling the entire chip, which is the worst time to
use a peltier.

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pharke
If an advanced civilization continued to improve the efficiency of this effect
would they eventually use it to capture the majority of the energy output of
their local star? You could have a shell of high efficiency solar satellites
surrounded by another shell of high efficiency Seebeck satellites. What would
this look like from a distance? Would they be able to capture enough energy so
their star would be indistinguishable from the ambient temperature of space?

Our galaxy and others appear to be missing most of the mass i.e. stars that
they should have in order to rotate as fast as they do. We put the figure for
missing mass at about 80 to 90 percent for our galaxy. What if our galaxy and
others are already colonized by advanced civilizations that make maximal use
of the power output of stars so it simply looks like we're missing most of the
matter that should exist. This could explain why there is a variation in the
amount of missing mass between galaxies with some galaxies apparently
containing 0% 'dark matter'. No advanced civilization = no dark matter,
different amounts = different stages in development of the galactic
civilization.

Could this be a solution to the Fermi paradox?

~~~
bagacrap
What would they use all that energy for, and how would they use it in a way
that wouldn't radiate heat or light on par with the amount captured?

~~~
pharke
A good use might be computing power whether its for storing the minds of
everyone in the civilization or powering one big mind or simulating universes
or maybe it's all dedicated to finding a way to reverse entropy.

If we're assuming a highly advanced civilization aiming for maximal efficiency
I would hope that they have figured out how to make all of their electrical
systems out of high temperature superconductors.

~~~
Matumio
Is there really a way to "use" energy for computation that doesn't just
convert all of it to heat?

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dclowd9901
They kept referring to IoT uses in the article. It got me wondering if the
best usage of this would be to be embedded in a jacket’s outer shell. You get
the surface area but not a lot of wattage of heat, I guess. But it sounds like
it makes a pretty good insulator. I could certainly imagine sensors running
off that kind of power.

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perl4ever
Something I was curious about, but not sure where to start - suppose you
wanted to make something that at 400-500K, would emit radio waves from which
the temperature could be derived. And as small, simple and durable as
possible, so it didn't break down.

I mean, there's going to inherently be infrared, so how can you convert that
to radio of roughly a desired frequency range without complex machinery?

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jasondclinton
Does anyone know if this discovery can be used to boost the efficiency of
solar panels? Don't solar panels get incredibly hot?

~~~
vermilingua
The title is misleading, the technology (thermoelectric cooler) does not turn
heat into electricity, but temperature gradients.

It needs a nearby source of cool to work, and when a solar panel is hot,
oftentimes everything surrounding it is hot.

~~~
BurningFrog
My intuition says the shaded ground below it can be quite a bit colder.

I have no real data...

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RandomWorker
Sadly the key here is lab scale and vanadium. Costs won’t make it worthwhile.

~~~
mmazing
Easy, just build a fusion reactor capable of eventually producing vanadium
from hydrogen, and you got yourself a stew going!

Edit : Method of producing said reactor left as an exercise for the reader.

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icris
does this imply an overall entropy reduction for a whole system comprising a
device and support apparatus for reusing its heat as energy source supply?

~~~
0xBA5ED
No you can't make a perpetual motion machine with it ;)

~~~
Zenst
But could you produce a cooling system that this could power?

Or at least recycle some of the heat fridge/freezers produce back into
electricity.

~~~
mping
I was thinking more like CPUs and GPUs

~~~
0xBA5ED
Right. I'm thinking about server farms.

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sunseb
Would this be efficient in a mobile phone?

~~~
Jon_Lowtek
This will be slowly but surely be used everywhere. Reducing heat output while
providing electricity is almost always a win-win situation.

~~~
comicjk
There are a lot of factors you're not considering. Reducing heat output is
good, yes, but putting a layer between your chips and their heat sink is bad!
Even though the total heat output is lower, the chip temperature will be
higher, because it will be more insulated. There is no way around this; any
heat-to-power device acts as insulation compared to a plain heat conductor.
You will also have added weight and cost. In a phone, where the heat
differences are small, the electricity gained will be almost nothing. So
actually we're not likely to see this in phones.

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ailideex
// Removed as I'm not a physicist and may be mistaken.

~~~
lopmotr
I think it's correct. Heat is the flow of thermal energy. A portion of that
flowing energy is converted to electrical energy. Perhaps you're confusing
heat with thermal energy?

There must be some heat flowing to generate electrical power because of the
1st law, so even if the effect is described as being due to a temperature
difference, in practice, you also need a heat flow to be useful.

Your quote about "without any side effect" means without heating up a cold
reservoir. But the article doesn't claim that.

~~~
zbrozek
Heat is the energy, not the flow. That flow is flux or power. A temperature
difference is how we perceive or measure a difference in thermal energy
density between two places, and is the potential that drives heat flux. A
thermoelectric barrier between those two wells can extract energy from that
flow, within thermodynamic limits.

~~~
lopmotr
Yes, I was a bit sloppy. It's the flowing energy, not the flow of energy. The
point of my comment was to distinguish heat from stored thermal energy so the
distinction isn't so important in that context.

