Researchers at Stanford University created a solar panel that can be a “continuous renewable power source” during the day and at night.
Stanford University researchers developed a photovoltaic (PV) cell that uses a process known as radiative cooling to generate renewable energy 24 hours a day, seven days a week.
The researchers used an ordinary solar panel equipped with a thermoelectric generator to generate a small amount of electricity from the temperature difference between the solar cell and the air. Nighttime solar panels can produce enough energy to charge a mobile phone.
Modified solar panels that operate at night generate enough power to charge a phone or power an LED light, eliminating the need to store energy in off-grid batteries.
In simple words solar electricity is produced when the sun’s rays strike a relatively cool solar panel. The panel is made up of solar cells, which are layers of a semi-conducting material, usually silicon. When light shines on this material, it causes an electrical current to flow.
However, at night, solar panels radiate heat to outer space, which has a temperature of about 3 kelvin (-270.15°C), because heat travels in the direction of lower temperatures. As a result, the solar panel is cooler than the night air, a temperature difference that can be used to generate electricity.
Shanhui Fan of Stanford University in California and his colleagues accomplished this by adding a thermoelectric generator, a device that generates currents based on temperature differences, to an off-the-shelf solar cell.
According to the researcher, “The solar panel turned out to be a very efficient thermal radiator, at night, the solar panel can actually reach a temperature that’s below the ambient air temperature, and that’s a rather unusual opportunity for power harvesting.”