Polymer gel pulls in water vapor to cool solar panels
Given that solar panels lie in direct sunlight, it goes without saying that they can get pretty hot. Unfortunately, though, they also get less efficient as they heat up. That said, a new gel could help cool them … without using any electricity.
Developed at Saudi Arabia's King Abdullah University of Science and Technology (KAUST), the polymer gel contains both calcium chloride and carbon nanotubes. The material is very adhesive, so it can easily be applied to the back of existing photovoltaic panels.
At night, the calcium chloride – which is a powerful desiccant – draws water vapor out of the humid air and into the gel, where it's stored as a liquid. That gel expands as it takes on water, potentially doubling its dry weight.
In the daytime, the carbon nanotubes absorb solar heat from the panel. Once enough of that heat has been passed into the gel, the stored water gets hot enough that it turns back into vapor. It then evaporates out of the gel, carrying the heat away with it.
When the fully water-loaded material was tested on solar panels under artificial sunlight in a lab, it was found to reduce their temperature by a total of 10 ºC. An even greater temperature-drop was achieved when the gel was later tested outdoors under natural sunlight, improving a panel's efficiency at converting solar energy into electricity by up to 19 percent.
"We believe this cooling technology can fulfill the requirements of many applications because water vapor is everywhere and this cooling technology is easy to adapt to different scales," says postdoctoral researcher Renyuan Li. "The technology could be made as small as several millimeters for electronic devices, hundreds of square meters for a building, or even larger for passive cooling of power plants."
A paper on the study, which is being led by Prof. Peng Wang, was recently published in the journal Nature Sustainability.