Around 750 million people around the world do not have access to electricity at night. Although solar cells can provide energy during the day, conserving energy for later use requires significant battery storage. In an article published in Applied Physics Letters, researchers from Stanford University mention a photovoltaic cell capable of harvesting energy from the environment day and night and completely avoiding the need for batteries.
The device harnesses heat escaping from Earth to space - energy of the same order of magnitude as incoming solar radiation.
At night, solar cells radiate and lose heat to the sky, then reach a temperature several degrees lower than the surrounding air. The device under development uses a thermoelectric module that generates voltage and current at paremove the temperature gradient between the battery and the air. This process depends on the thermal design of the system, which includes a hot end and a cold end.
Sid Assawaworrarit, author of the research paper, said: "You want the thermoelectric component to have very good contact with the cold side (i.e. the solar cell) and the hot (i.e. the solar cell). If you don't have that, it's impossible to get much power from it."
The team demonstrated. how well their device generated electricity day and night. During the day, the device works in reverse and provides additional power to conventional solar cells.
It appears that this device is inexpensive and can in principle be integrated into existing solar cells. Additionally, thanks to its simplicity, it is possible to build in remote areas with limited resources.
Study author Zunaid Omair said: "What we did here was build the whole thing from commercially available components, with very good contact thermal, and the most expensive thing in the whole device is the thermoelectric itself”
Using electricity for night lighting requires several watts of power. The current installation can produce 50 milliwatts. per square meter, which means the lighting will require around 20 square meters of photovoltaic area
“None of these components are specifically designed for this purpose, so I think there is room. to improvement, in the sense that if people actually designed these components for our needs. For each of them, I think the performance could be better," said study author Shanhui Fan.
It is reported that the research team will optimize the insulation thermal and thermoelectric components of the deviceeil. Currently, they are investigating technical improvements to the solar cells themselves to improve radiative cooling performance without affecting their solar energy harvesting capabilities.