'Reverse Solar Panel' Generates Electricity at Night
4 34Researchers 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.
4 comments
Not a "reverse solar panel" (Score: 5, Informative)
by greytree ( 7124971 ) on Saturday January 31, 2026 @04:13AM (#65960636)
A solar panel converts sunlight to electricity.
A reverse solar panel would convert electricity to sunlight.
Stupid headline
Re:Resulting capacity is fairly low (Score: 5, Interesting)
by Geoffrey.landis ( 926948 ) on Saturday January 31, 2026 @09:56AM (#65960824)
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]
Re:Light bulb (Score: 5, Informative)
by Geoffrey.landis ( 926948 ) on Saturday January 31, 2026 @09:59AM (#65960830)
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)
by Geoffrey.landis ( 926948 ) on Saturday January 31, 2026 @09:48AM (#65960818)
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.