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.

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