New Cooling Hydrogel Could Boost Solar Panel Efficiency by 12%
Researchers have created an innovative hydrogel composite that captures moisture overnight and provides evaporative cooling for solar panels during daylight hours. The system has been successfully tested in both laboratory and outdoor settings across two continents.
A team led by researchers from King Abdullah University of Science and Technology (KAUST) in Saudi Arabia has developed an affordable passive cooling technology for photovoltaic panels.
The technology utilizes a composite of polyacrylic acid sodium salt (PAAS) and lithium chloride (LiCl) hydrogel applied to the back of solar modules. "Our focus is on materials that enable passive cooling," explained researcher Qiaoqiang Gan. "These thin materials can be applied to various systems requiring cooling, such as greenhouses and solar cells, without compromising their performance."
The researchers created the composite by combining LiCl and PAAS in a 2:1 ratio. After mixing, they poured the solution into a mold and cured it for an hour to form a flat shape. This specific ratio was chosen to ensure the material remains effective under challenging conditions, including relative humidity above 90% and temperatures exceeding 30°C.
"The composite takes advantage of the desiccant's moisture-absorbing properties, collecting humidity at night and enabling evaporative cooling during the day," the researchers noted. "In this formulation, PAAS molecules enhance water storage capacity through their highly water-attracting carboxylate groups. While LiCl crystals serve as moisture-absorbing agents, the stored water is released gradually throughout the day thanks to the balanced LiCl content, eliminating the need for cooling layer replacement."
For testing, the team used a polycrystalline silicon solar panel measuring 54 mm × 54 mm. They applied a 7 mm thick layer to its back, which expanded to approximately 10 mm after absorbing water. Testing occurred in laboratories in Saudi Arabia and the United States, with field tests in Thuwal, Saudi Arabia (21 days) and Buffalo, New York (one month).
"Our laboratory tests showed remarkable cooling performance," reported the team. "When subjected to continuous solar radiation of 1 kW/m² for 3 hours, the cooling power reached 373 W/m², decreasing to 187 W/m² after extending to 12 hours. Under simulated real-world outdoor solar conditions, the system delivered an average cooling power of 160 W/m², peaking at 247 W/m² between 10-11 am."
In outdoor testing in Saudi Arabia, with ambient temperature at 37°C and 53% relative humidity, the system achieved a sustained evaporative cooling power of 175 W/m². "We recorded temperature reductions up to 14.1°C around midday (12.5°C on average from 12:00-13:00), resulting in a significant increase in power conversion efficiency from 13.1% to 14.7%—approximately a 12.2% improvement," the researchers stated.
The U.S. testing revealed that the enhanced cooling efficiency could extend solar panel operational lifespan by over 200% and reduce electricity costs by 18%. The material costs approximately $56/m² (USD 37), which the team highlighted as "lower than most previous hydrogel or non-hydrogel cooling methods."
