A moisture-absorbing polymer-based composite, or hydrogel, is set to enhance solar panel efficiency and lifespan, offering a scalable, low-cost solution for hot and humid environments. The material, developed at KAUST, absorbs ambient moisture overnight and provides cooling by slowly releasing water throughout the day.

Solar panels are central to the clean energy transition, accounting for most renewable additions worldwide and reducing nearly 1.5 billion tons of carbon dioxide emissions annually. Discoveries of new materials and improved manufacturing techniques are crucial for this continued progress, as they enhance solar panel performance.

A key challenge for solar panels is that, alongside converting sunlight into electricity, they also absorb light as heat. This thermal buildup raises panel temperatures, reducing power output and shortening operational lifespan. Existing cooling systems designed to manage these effects often rely on external power sources to circulate water or air — an approach that is both energy-intensive and costly. These systems also require frequent maintenance.

To design a cheaper and greener alternative, a team led by Qiaoqiang Gan and postdoc Saichao Dang has created a hydrogel layer that uses natural evaporative cooling. Attached to the rear of solar panels, the layer operates autonomously, requiring no electricity or maintenance.

The hydrogel consists of lithium chloride salt embedded in a cross-linked polymer network formed by sodium polyacrylate. Through this microporous polymer matrix, the salt helps pull in moisture from the air. The polymer network contains tiny pores that trap water molecules and includes hydrophilic carboxylate groups, which further enhance water storage capacity.

“Each component plays a role,” says Dang. “By adjusting their proportions, we found a sweet spot where the gel can hold enough water and release it slowly throughout the day.”

Researchers fabricated the hydrogel using a straightforward process. They stirred the polymer powder into the salt solution for three minutes, poured the mixture into a mold, flattened it, and allowed it to cure at room temperature for one hour.

The hydrogel demonstrated sustained cooling and strong water uptake. In a long-term outdoor test at temperatures ranging from 25 C to 41 C and relative humidities of 31 to 91 percent, it reversibly absorbed and released water over 21 days without failure. At 38 C, it achieved a record temperature drop of 14.1 C, boosting power conversion efficiency by 12.9 percent.

“We expected a slow release but were surprised by how steady and how long the cooling lasted — even under strong sunlight for 10 hours,” Dang says.

Read more at KAUST Discovery.