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Cheap material converts heat to electricity

sciencemag.org

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Re: Cheap material converts heat to electricity

#61

Post by oehpr »

billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

It sure is tempting to think of heat as just energy. I mean it is. Of course. But the kind of device you're talking about is like Maxwell's Daemon. The article is talking about a step towards making an inexpensive thermocouple. These require temperature differentials, not just heat. And you don't want to be drawing power from the temperature differential in your house ;)

Re: Cheap material converts heat to electricity

#62

Post by bernulli »

elzbardico wrote: post #60
billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

I don't see why people are downvoting you, as you are basically wanting to avoid wasting good energy with air conditioning. Maybe people thought your tone was blasfemous?

People are downvoting because billpg essentially wants a perpetuum mobile, something that creates useable energy just from the presence of a high temperature reservoir. This violates the 2nd law of thermodynamics. Heat does not equal usable energy, what you need to extract something useful is a temperature difference.

Re: Cheap material converts heat to electricity

#63

Post by tialaramex »

billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

> What would be ideal is if the heat energy could be converted into some other form of energy

That would be nice, wouldn't it. If you ever build a universe, you should definitely implement that. In this universe the laws of thermodynamics specifically forbid destroying heat, or converting it into something else.

Heat will naturally spread out evenly over time, but if we would prefer to do the opposite, moving heat where we want it (or away from where we don't want it), we need to use a heat pump which expends energy to do that, and that energy produces further waste heat which, yes, we also need to move. This is a core principle of how our universe works. Nobody is going to invent a new material that violates the laws of thermodynamics, for the same reason nobody is going to find an even integer that was hiding between 2 and 4 somehow without us noticing it.

Re: Cheap material converts heat to electricity

#64

Post by grishka »

billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

Or you could have a battery and store that energy to supply your house with electricity, thus reducing your bills.

Re: Cheap material converts heat to electricity

#65

Post by Ajedi32 »

elzbardico wrote: post #60
billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

I don't see why people are downvoting you, as you are basically wanting to avoid wasting good energy with air conditioning. Maybe people thought your tone was blasfemous?

Because what GP is proposing is thermodynamically impossible. The second law of thermodynamics states that heat naturally flows from hotter to colder regions. You can't just magically convert a static pool of heat to light and beam it somewhere else with no energy input. It's like suggesting that we generate electricity by rolling stones uphill; it just doesn't make sense.

Re: Cheap material converts heat to electricity

#66

Post by fy20 »

France_is_bacon wrote: post #55
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.

I'd be interested, too. I once read in some article that CPUs have the same power consumption as equivalent output of a nuclear reactor, based on size, of course. So the 1 inch of a CPU takes as much energy as 1 inch of a nuclear fusion output from a nuclear reactor. Again, I don't know if this is true, but if it is, that's a lot of heat energy, given the number of computers in the world. But maybe I remember wrong,…

Must have been a Pentium 4.

Re: Cheap material converts heat to electricity

#67

Post by blueblisters »

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'…

> I thought about many ways to get rid of heat without having to dump it somewhere, but thermodynamics is such a terrible thing.

This is likely a stupid question but temperature is a statistical property describing the energy of molecules right? Is there no way to tap the energy of the molecules for useful work without having a temperature difference?

Re: Cheap material converts heat to electricity

#68

Post by grishka »

tialaramex wrote: post #63
billpg wrote: post #59

Heat is energy. In summer, the sun (rudely) gives me excess unwanted heat in my house. I need to expend even more energy to get that heat from inside to outside my house. (We call this process "Air Conditioning".) What would be ideal is if the heat energy could be converted into some other form of energy that I could dispose of. Maybe if I could turn it into electricity I'd put a lightbulb in my window and shine the…

> What would be ideal is if the heat energy could be converted into some other form of energy That would be nice, wouldn't it. If you ever build a universe, you should definitely implement that. In this universe the laws of thermodynamics specifically forbid destroying heat, or converting it into something else. Heat will naturally spread out evenly over time, but if we would prefer to do the opposite, moving heat wh…

> In this universe the laws of thermodynamics specifically forbid destroying heat, or converting it into something else.

But wait, what does a Stirling engine run on? Or a steam engine? You clearly can get some energy out of heat.

Also, objects that are hotter than absolute zero radiate infrared light — and you, in principle, could convert light, regardless of its spectrum, into electricity.

Re: Cheap material converts heat to electricity

#69

Post by bernulli »

grishka wrote: post #68
tialaramex wrote: post #63

Earlier quoted context omitted.

> What would be ideal is if the heat energy could be converted into some other form of energy That would be nice, wouldn't it. If you ever build a universe, you should definitely implement that. In this universe the laws of thermodynamics specifically forbid destroying heat, or converting it into something else. Heat will naturally spread out evenly over time, but if we would prefer to do the opposite, moving heat wh…

> In this universe the laws of thermodynamics specifically forbid destroying heat, or converting it into something else. But wait, what does a Stirling engine run on? Or a steam engine? You clearly can get some energy out of heat. Also, objects that are hotter than absolute zero radiate infrared light — and you, in principle, could convert light, regardless of its spectrum, into electricity.

They run on temperature differences, that's how you get usable energy out of it. Google Carnot engine, there's even a super simple way to find the maximum efficiency just from the temperatures!

Re: Cheap material converts heat to electricity

#70

Post by mrfusion »

SigmundA wrote: post #57

It says a ZT of 3.1, isn't that approaching 25% efficiency on par with more standard heat engines? Also more in line with say a solar panel for light to electricity. That kind of efficiency would be a big breakthrough if it where affordable, imagine the applications.

Could you put these on the backs of solar panels to capture some waste heat?

Or tack them on ice engines.

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