No sun? No problem.
A new thermoelectric device can generate electricity for an LED light bulb even during the blackest night, according to a report by researchers.
The secret is using a phenomenon known as radiative cooling, which happens when surfaces on the ground radiate heat into the atmosphere. This process can make a surface cooler than the air surrounding it, which explains why frost forms on grass even if the air temperature is above freezing.
Researchers say their device is a useful form of renewable energy, especially because lighting demand peaks at night. "Beyond lighting, we believe this could be a broadly enabling approach to power generation suitable for remote locations, and anywhere where power generation at night is needed," lead author Aaswath Raman, an assistant professor of materials science and engineering at the University of California, Los Angeles, said in a statement.
The prototype device was tested on a table 3 feet (1 meter) above the ground on a rooftop in Stanford, California, in late December. It was placed in a polystyrene enclosure covered in aluminized mylar (which minimizes thermal radiation) and protected by a wind cover. Inside the protective layers, researchers made the device draw heat from the air and send it back into the atmosphere, using a black emitter.
The researchers managed to power an LED using a voltage boost converter, and measured that over 6 hours the device can generate as much as 25 milliwatts of energy per square meter. That's much lower than typical solar cells, but the advantage is that the device works at night, while solar cells have no sunlight to convert into energy.
The researchers say that with some modifications, the device could be used over a wider scale since the radiative cooler is simple (an aluminum disk covered in paint) and the other components are commercially available. For example, the researchers suggest increasing heat-exchange efficiency by reducing heat gain in the radiative cooling part of the device. The device may also work best in hotter and drier climates, the team noted.
"Our work highlights the many remaining opportunities for energy by taking advantage of the cold of outer space as a renewable energy resource," Raman said. "We think this forms the basis of a complementary technology to solar. While the power output will always be substantially lower, it can operate at hours when solar cells cannot."
This research was published Sept. 12 in the journal Joule.
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Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for Space.com for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace