One of the drawbacks of solar energy is that the current technology produces little power on cloudy days and zero at night. People who have installed solar panels in their homes usually store energy during the day so that they can use it at night.
But now, researchers from Stanford have made a breakthrough, developing solar panels that work even at night.
According to a study published in the journal Applied Physics Letters, by modifying commercially available solar panels and exploiting a “radiative cooling” process, the new panels can serve as a continuous renewable power source for both day and nighttime.
The device, developed by Shanhui Fana, Sid Assawaworrarit, and Zunaid Omair, includes a thermoelectric generator that harvests electricity from the temperature difference between the ambient surroundings and the PV cell.
“We tend to think of the sun as the important renewable energy resource,” said Shanhui Fan, the lead researcher on the project. “The coldness of outer space is also an extremely important renewable energy resource.”
Technically speaking, the modified panels do not harvest solar energy at night. Instead, the researchers use radiative cooling. For example, when an object is facing the sky at night, it still radiates heat to the atmosphere, which means the object can become cooler than the air around it. The difference in temperature is then used to generate electricity.
While the modified solar panels still generate less energy (50 milliwatts per square meter), than what traditional paddles produce during the day (200 milliwatts per square meter), the researchers said that the energy could still be of use, especially at night when the demand for energy is lower.
“So, this is significantly lower,” explains Fan. “But it may potentially be useful for some of the low power density applications.” That might include nighttime lighting, charging devices, and keeping sensors and monitoring equipment online.”
