Advanced Hydrogel-Based Cooling for High-Efficiency, Durable Photovoltaic Systems

A research team has developed a simple, affordable, and highly effective hydrogel-based cooling technology that addresses one of the solar industry's most persistent challenges: hot spots. These localized areas of overheating, caused by partial shading from leaves, bird droppings, dust, or cell defects, have long plagued photovoltaic systems by diminishing power generation efficiency, accelerating module degradation, and in severe cases, posing fire risks. Research examining over 3.3 million photovoltaic panels revealed that 36.5% exhibit thermal defects, with affected areas registering an average temperature increase of over 21°C. For every 1°C rise in operating temperature, a c-Si solar panel loses approximately 0.4-0.5% of its efficiency — a compounding problem that compromises the long-term stability and returns of solar installations worldwide.

The team has engineered a multi-layer hydrogel coating that fundamentally solves this problem. The coating is primarily made from polyacrylamide (PAM), a water-absorbing gel matrix. To enhance its strength and durability, hydroxyethyl cellulose (HEC) — a natural polymer — is added to reinforce the gel network, preventing the cracking and shrinkage that plague conventional hydrogels. Leafy-patterned cotton threads are embedded within the gel to actively transport water to the hottest areas, ensuring uniform and sustained cooling across the entire panel surface. A thin, porous outer layer of polytetrafluoroethylene (PTFE, commonly known as Teflon) repels dust while controlling the rate of water evaporation, maintaining long-term performance with minimal maintenance.

The technology delivers exceptional cooling performance. In real-world tests, the hydrogel coating reduced hot-spot temperatures by 16.2°C — over 50% more effective than conventional hydrogels — while delivering cooling power of 463.8 watts per square meter. This temperature reduction translates directly into enhanced energy production, with power output increasing by 13% under hot-spot conditions. Critically, the coating demonstrates outstanding durability for long-term outdoor use. Traditional hydrogels can experience volumetric shrinkage of up to 46% after extended use, leading to cracking and failure. The team's innovative formulation, incorporating HEC and cotton threads, limits shrinkage to just 34%, ensuring reliable, maintenance-free performance under real-world conditions including UV exposure, temperature fluctuations, and humidity.

The economic case for the technology is compelling. Modeling shows annual power generation increases of 7.0% in Singapore, 6.5% in Hong Kong, and 5.9% in Tianjin. Adding the hydrogel system increases the cost of a solar panel by approximately 10.7%. However, in regions with high electricity prices and abundant sunlight, this marginal cost is recovered rapidly — with payback periods as short as 3.2 years in Singapore and 4.5 years in Hong Kong. As production scales and costs decline, the technology will become increasingly accessible across all markets. On a global scale, this innovation has the potential to offset approximately 50% of power generation losses caused by hot spots in Building-Integrated Photovoltaic (BIPV) systems, making a pivotal contribution to the advancement of solar energy technology and urban carbon neutrality.

The coating can be easily applied to the backsheet of existing solar panels without any modification to circuit designs, making it a cost-effective, drop-in solution for both new installations and existing systems. The hydrogel coating can be directly laminated onto the backside of the photovoltaic panel, where strong hydrogen-bond interactions enable robust interfacial adhesion between the hydrogel and the backsheet. This ease of integration minimizes installation costs and operational disruption, while the passive, self-regulating cooling requires no external energy input and is compatible with rainwater harvesting for water supply.