An ultra-low-cost thermoelectric device captures the cold at night by generating electricity that powers an LED.
The research was published yesterday in the scientific journal Joule.
“The device is capable of generating energy at night, when the solar cells are not working,” underlines the first author of the research Aaswath Raman (@aaraman), assistant professor of materials science and engineering at the University of California, Los Angeles. “In addition to lighting there can be a whole range of applications for generating electricity in remote locations, or in any areas that need energy at night.”
The executioner of the night
While solar cells are now an established source of energy during the day, a system that does the same thing at night is lacking. L'solar power it can be stored in batteries for use when there is no sun, but this still comes at a high cost.
The device developed by Raman and Stanford University researchers Wei Li and Shanhui Fan bypasses the limitations of solar energy. It is based on the principles of radiative cooling. (A quick link to understand what it is, even if I explain it briefly below).
How does it work?
When a surface exposed to the air transmits its heat to the atmosphere, it loses heat and as a result of this passage it acquires a slightly colder temperature than the surrounding air.
This phenomenon can be easily observed: have you ever seen the small ice crystals that form in a meadow? The same principle can be used by exploiting these temperature passages to generate energy.
Raman and colleagues tested their low-cost generator on a Stanford roof for the first time under a cold December sky. The generator consists of a polystyrene surface covered with aluminum and protected by a small wind barrier. He stands on a table positioned one meter from the ground, and collects the heat that rises from the roof to the sky. When connected to a converter and a white LED, the device passively feeds the light. It is currently capable of generating 25 milliwatts of energy per square meter. Not much, but ongoing tests are already perfecting the system, obtaining up to 20 times the current energy.
At no cost
The whole system can be assembled with purchased or recycled components, and Raman believes it can have vast practical applications for this too.
“Our work shows how many opportunities there are to also create energy from radiative cooling, the temperature exchange that happens at night,” says the researcher. “It is a perfectly complementary technology to solar technology: it collects much less energy, but it can work when there is no sun.”
Research references:
Aaswath P. Raman, Wei Li, Shanhui Fan. Generating Light from Darkness. Joule, 2019; DOI: 10.1016 / j.joule.2019.08.009
