'Reverse Solar Panel' Generates Electricity at Night (extremetech.com) 34
Researchers at the University of New South Wales are developing a "reverse solar panel" that generates small amounts of electricity at night by harvesting infrared heat radiated from Earth. "In the past, scientists have demonstrated that a 'thermoradiative diode' can convert infrared radiation directly into electricity; when used to convert heat from Earth, they exploit the temperature difference between Earth and the night sky, generating a current directly from heat," notes ExtremeTech. "This approach completely eliminates the need for heat to generate steam, though the resulting capacity is fairly low." From the report: The researchers estimate they could generate only about a watt per square meter, which isn't much. One reason for the low output is that the Earth's atmosphere lessens the heat differential that drives the generative process; in space, though, that's not an issue.
Now, researchers believe that the ability to generate power in the moments between direct sunlight could help power satellites. That could be especially true in deep space, where periods without sunlight can be longer, and sunlight is often weaker; in these situations, losing electricity to heat loss is unacceptable.
Many satellites already use heat to generate electricity, though with a much more rarified "thermoelectric generator" that uses rare, expensive materials like plutonium to create heat. With thermoradiative diodes, the heat source can be the Sun-warmed body of the satellite itself.
Now, researchers believe that the ability to generate power in the moments between direct sunlight could help power satellites. That could be especially true in deep space, where periods without sunlight can be longer, and sunlight is often weaker; in these situations, losing electricity to heat loss is unacceptable.
Many satellites already use heat to generate electricity, though with a much more rarified "thermoelectric generator" that uses rare, expensive materials like plutonium to create heat. With thermoradiative diodes, the heat source can be the Sun-warmed body of the satellite itself.
peltier/thermocouple? (Score:3)
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It's an interesting idea, but pointless given how cheap batteries have become.
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"Radioisotope Thermoradiative Cell Power Generator"
This is intended as a space craft power source. As in satellites.
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I have a watch that powered by one of those.
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No, they just glued a bunch of them on the back side of a solar panel.
If you read this submission immediately after the one about HCFC's, then it doesn't make any sense. To reduce global warming, we have to let that infrared escape into space. Trapping underneath solar panels will only exacerbate 'global warming'.
RTG (Score:4, Informative)
Many satellites already use heat to generate electricity, though with a much more rarified "thermoelectric generator" that uses rare, expensive materials like plutonium to create heat
The USA and USSR have launched a few dozen spacecraft with RTGs, out of more than 12,000 satellites launched in total. That's not "many".
There's a blond joke in there (Score:1)
somewhere
I'd like to see more stuff on this with heat... (Score:1)
If this is done right, it would allow nuclear reactors to not need to push water through steam turbines, but just have the heat from the cooling solution be directly converted to energy, which adds a lot of efficiency in the process, and fewer moving parts. I'm hoping for progress on this front, as it is useful not just for energy from residual heat, but for a number of other applications.
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Whenever they invent this I hope they name it the Thermoelectric Generator. Although in actuality I think you're hoping for something magical that can overcome the second law of thermodynamics and do this with extreme efficiency.
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Sadly the best thermoelectric generators are not nearly as efficient as conventional thermodynamic engines. I don't know if there is a fundamental limitation or in principal they could get close to Carnot efficiency. Also thermoelectric generators usually have a max temperature lower than that for thermodynamic generators so they are starting at a lower Carnot efficiency
Not a "reverse solar panel" (Score:5, Informative)
A reverse solar panel would convert electricity to sunlight.
Stupid headline
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So that's where they have "Reverse Christmas", on the beach ? Got it.
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Ah. So that's where they have "Reverse Christmas", on the beach ? Got it.
where do you think Santa gets all the toys fro to give you? Steals them from Australia.
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A solar panel converts sunlight to electricity. A reverse solar panel would convert electricity to sunlight.
We have those, lightbulbs, fluorescent tubes, LEDs, etc :-)
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A reverse solar panel would convert electricity to sunlight.
Actually, you do have to put diodes on solar panels because otherwise they do work in reverse at night. Unfortunately, the energy they emit is in the infrared spectrum, so arguably solar panels make pretty lousy light bulbs.
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Solar panels are just another PN junction, aka diode. Just like LEDs, photodiodes (which are actually just tiny solar cells) and even regular diodes.
They can work as LEDs, and in fact do if you pass current through them, but they're not great at it. They can also work as normal diodes as
Solar fridge (Score:3)
Down Under (Score:2)
It's a Down Under panel.
Their drains swirl the other way, too!
Resulting capacity is fairly low (Score:3)
Re:Resulting capacity is fairly low (Score:5, Interesting)
There are 4047 square meters in one acre. If I had a home with a heat pump that consumed 4kW I could run it with one acre of these panels - although I probably couldn't start it up. There won't be much use for this technology on Earth.
Yes, they're more useful in space. Here's a a presentation I did a few years back: https://ntrs.nasa.gov/api/cita... [nasa.gov]
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A less obvious use is to add charge to your house batteries, extending their capacity for those long nights.
How well this works in the frozen North remains to be understood.
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Did you ever launch the cubesat?
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So the idea is to use these in RTGs to replace the thermocouples used now?
Would it make sense to use them e.g. as the back face of solar panels, or as an extra layer on a spacecraft's radiators? Or is the power you can get from lower-grade heat sources too little to be worthwhile?
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So the idea is to use these in RTGs to replace the thermocouples used now?
Right, to use thermoradiative cells instead of thermoelectric converters in Radioisotope power sources.
Would it make sense to use them e.g. as the back face of solar panels,
My quick analysis is that you don't gain anything by doing that; you lose as much power by raising the operating temperature of the solar cells (because anything you put in the thermal path slows heat transfer) as you gain from the thermoradiative effect.
or as an extra layer on a spacecraft's radiators? Or is the power you can get from lower-grade heat sources too little to be worthwhile?
Yes. Also, you can then make the system with smaller radiators, because the radiators can run hotter.
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Thank you.
Light bulb (Score:2)
A light bulb is a reverse solar panel:
Solar panel: absorb light, produce electricity.
Light bulb: absorb electricity, produce light.
Re:Light bulb (Score:5, Informative)
A light bulb is a reverse solar panel: Solar panel: absorb light, produce electricity. Light bulb: absorb electricity, produce light.
More specifically, a LED is a reverse solar panel, and in fact, if you power a solar cell backwards, they emit light (electroluminescence).
But thermoradiative cells are reversed in a different way, solar cells are essentially carnot engines if you think about them right: Solar light at 6000K in ("hot side"), waste heat out ("cold side") and electrical power produced. In a perfect carnot cycle, the hot and cold sides can be swapped. Thermoradiative cells switch the hot and cold side: heat in ("hot side"), light out ("cold side"), and electrical power produced.
Of course the light out is the thermal spectrum, not the solar spectrum, and hence the semiconductor used isn't the same as the one used in solar cells.
https://ntrs.nasa.gov/citation... [nasa.gov]
Quotes me... not. (Score:5, Interesting)
Damn. This seems to be a shortened version of the CNN article, https://www.cnn.com/science/ni... [cnn.com] except they left out the second half of the article, where the CNN reporter includes several quotes from me.
I guess my fifteen minutes of fame got cut down to thirty seconds. At least the second link in the summary mentions me.
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Dumb name (Score:2)
what's the power density on these? (Score:2)
The latest news I've read on these is they generate milliwatts in square meters of space, and are about as useful as those "nuclear batteries" people were scamming around (again...) recently.
The only application for tech with that low of a power return is satellites?