Device generates electricity from the coldness of the universe
An international team of scientists has demonstrated that a measurable amount of electricity can be generated in a diode, directly from the coldness of the universe. The infrared semiconductor device faces the sky and uses the temperature difference between Earth and space to produce electricity.
The findings, published in Applied Physics Letters, may lead to the generation of electricity in a similar way to solar cells, but with the ability to power electronics at night.
“The vastness of the universe is a thermodynamic resource,” said study author Shanhui Fan. “In terms of optoelectronic physics, there is really this very beautiful symmetry between harvesting incoming radiation and harvesting outgoing radiation.”
In contrast to leveraging incoming energy as a normal solar cell would, the negative illumination effect allows electrical energy to be harvested as heat leaves a surface. Today’s technology does not have the capacity to capture energy over these negative temperature differences efficiently.
By pointing their device toward space, where temperatures approach mere degrees from absolute zero, the research group found enough of a temperature difference to generate power using an early design.
“The amount of power that we can generate with this experiment, at the moment, is far below what the theoretical limit is,” said study author Masashi Ono.
The group found that their negative illumination diode generated about 64 nW/m2 — a tiny amount of electricity, but an important proof of concept that the authors can improve on by enhancing the quantum optoelectronic properties of the materials they use.
Calculations were made after the diode created electricity, showing that, when atmospheric effects are taken into consideration, the current device can theoretically generate almost 4 W/m2 — roughly 1 million times what the group’s device generated and enough to help power machinery that is required to run at night. By comparison, today’s solar panels generate 100–200 W/m2.
While the results show promise for ground-based devices directed to the sky, Fan said the same principle could be used to recover waste heat from machines. For now, he and his group are focusing on improving their device’s performance.
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