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Cheap material converts heat to electricity

sciencemag.org

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Re: Cheap material converts heat to electricity

#31

Post by wiredfool »

grishka wrote: post #15
calgoo wrote: post #3

I wonder if you could get it small enough to use with CPUs. Could extend the battery of a laptop for example. I’m also thinking of AC units, where it could lower the power consumption at the same time as lowering the heat we diffuse into nature, especially in big cities where the most rooftops feel like saunas.

When it was unusually hot over here, I was thinking about this. We can convert nearly every kind of energy into electricity and back. But for heat, for some bizarre reason, this only works one way. A lot of processes generate it, but you literally can't convert it into any other form of energy. You have to transfer it somewhere where it won't be as much of a problem. It would be very nice to have an AC where you don'…

Thermodynamics -- you can't win, you can't break even, and you can't even leave the game.

Re: Cheap material converts heat to electricity

#33

Post by jkgktnrnfnf »

layoutIfNeeded wrote: post #25
988747 wrote: post #20

Finally! Now we can have an air conditioner that does not require a pipe to blow the hot air outside. Like truly mobile unit.

That’s thermodynamically impossible.

Not true.

For example you could convert the heat into photons (infrared radiation) and beam that out of the room without needing a pipe. You would probably need an infrared transparent patch on the window to aim at.

https://spie.org/news/5129-a-metamaterial-to-convert-heat-to...

Re: Cheap material converts heat to electricity

#34

Post by leoedin »

enkid wrote: post #19
kwhitefoot wrote: post #6

> Those could be installed everywhere from .. water heaters .. to scavenge some of the 65% of fossil fuel energy that winds up as waste heat. Modern condensing gas boilers for domestic use are better than 90% efficient, the exhaust gas is very cool so I don't think that thermoelectric devices have much to offer there.

If I understand the article correctly, you're talking about two different things. Something can be efficiently heated but if it cools down all of that energy is effectively lost. This device would allow you to recapture some of that energy that is lost to then reheat the water. Think of it more as active insulation than a better heating element.

I don't think that's quite how it works. This device (or any thermoelectric generator) converts a fraction of the heat energy flowing through it into electrical energy. That means energy has to flow through it for it to work - essentially the opposite of insulating. Using this device, by definition, will result in the original hot thing being cooler, and the "cold end" (normally the outside world) being ever so slightly warmer.

The place this would be useful is in capturing otherwise unusable energy from low grade heat waste. For example, the output water of a steam turbine might still be "hot", but there's very little you can do with it - it's in the wrong place for heating houses, it's too cold for steam turbines. Generally that energy is lost to the air.

Re: Cheap material converts heat to electricity

#35

Post by srean »

layoutIfNeeded wrote: post #24

Nitpick: you can’t convert heat to electricity. You need a heat differential .

Nitpick on nitpick -- you absolutely can convert heat energy into electric energy. A dynamo on a heat engine does exactly that. What suffices is temperature differential.

It is a terrible analogy, a modern physicist would prefer being caught dead rather than using it, but one can think of heat as a liquid (traditionally called caloric ) stored in a vessel. Temperature is the level of the liquid. For flow you need another vessel where the level is low, that would allow flow of heat from a vessel with higher level to a lower one and one can then convert that flow into power of a form one desires. Its possible to go in the opposite direction also, that's called a heat pump. Charge and voltage would be another (incorrect) way of thinking about heat and temperature.

Re: Cheap material converts heat to electricity

#36

Post by zionic »

matheusmoreira wrote: post #23

So I can use electricity to mine cryptocurrency and convert the excess heat back to electricity? I wonder how efficient such a thing would be.

I wonder why you don't have a miner-hot-water heater? Use energy to mine and the waste heat to keep your tank warm.

Re: Cheap material converts heat to electricity

#37

Post by jodrellblank »

layoutIfNeeded wrote: post #28
flavius29663 wrote: post #26

Earlier quoted context omitted.

Why? You could theoretically take out energy from the room in the form of electricity

You can’t. The second law of thermodynamics prohibits it. “It is impossible to devise a cyclically operating device, the sole effect of which is to absorb energy in the form of heat from a single thermal reservoir and to deliver an equivalent amount of work.”

How does having a hot side of a piece of material and a cold side of a piece of material come under "cyclically operating"?

Re: Cheap material converts heat to electricity

#39

Post by optimalsolver »

JoBrad wrote: post #18
pjc50 wrote: post #9

> The polycrystalline tin selenide the team makes is spiked with sodium atoms, creating what is known as a “p-type” material that conducts positive charges. To make working devices, researchers also need an “n-type” version to conduct negative charges. This is literally inventing half a solution. Shockley didn't go to the press when he'd built half a diode. (OK, this is snarky, but I think this is another case where…

> Zhao’s team recently reported making an n-type single-crystal tin selenide by spiking it with bromine atoms. And Kanatzidis says his team is now working on making an n-type polycrystalline version. Once n-type and p-type tin selenide devices are paired, researchers should have a clear path to making a new generation of ultra-efficient thermoelectric generators.

So write the paper after that's all done.

Re: Cheap material converts heat to electricity

#40

Post by davgard »

matheusmoreira wrote: post #23

So I can use electricity to mine cryptocurrency and convert the excess heat back to electricity? I wonder how efficient such a thing would be.

I'm quite curious if this works efficiently as well. The question is, is the amount of excess heat that the rigs give off and sustain the energy needed to keep the mining rigs working 24/7?
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