PolyU’s Hydrogel Coating Boosts Solar Panel Efficiency, Advancing Urban Carbon Neutrality

A research team at The Hong Kong Polytechnic University (PolyU) has developed a cost-effective and easy-to-apply hydrogel coating that enhances heat dissipation in solar panels, effectively cooling “hot spots” and improving overall power generation efficiency. By tackling hot spots—often caused by partial shading and a key reason for reduced performance and system problems—the new technology provides a strong solution to a long-standing issue in the industry while helping Hong Kong reach its goal of being carbon neutral in cities.

The breakthrough hydrogel cooling technology was developed by a PolyU research team led by Prof. YAN Jerry, Chair Professor of Energy and Buildings, along with Dr LIU Junwei, Research Assistant Professor in the Department of Building Environment and Energy Engineering. The team’s findings show that applying the hydrogel coating can reduce hot-spot temperatures by up to 16°C and increase solar panel power output by as much as 13%. When used in rooftop and building-integrated photovoltaic (BIPV) systems, the coating is expected to offset nearly half of the power losses caused by hot spots, significantly enhancing the long-term efficiency and stability of solar power generation for buildings.

Prof. Yan said, “Our hydrogel cooling technology effectively addresses the hot-spot issues in solar panels without the need to modify existing circuit designs. It is cost-effective and user-friendly, making it suitable for various urban settings. Taking Hong Kong and Singapore as case studies, our team anticipates potential annual power generation increases of 6.5% and 7.0%, respectively. The estimated payback periods are notably short at just 4.5 years and 3.2 years. On a global scale, this innovation has the potential to offset approximately 50% of power generation losses caused by hot spots in BIPV systems, demonstrating its pivotal contribution to the advancement of solar energy technology.”

The impact of hot spots on solar photovoltaic systems warrants close attention, as they not only reduce power generation efficiency by raising operating temperatures but can also pose fire risks in severe cases. Research on 3.3 million photovoltaic panels found that 36.5% had thermal defects, causing those panels to heat up by more than 21°C on average, which speeds up their wear and tear. In this context, the PolyU hydrogel coating stands out for its effective cooling performance and exceptional durability, making it well suited for long-term outdoor applications.

Dr Liu added, “Our team has combined the natural polymer ‘hydroxyethyl cellulose’ and the fibrous material ‘leafy cotton thread’ with the hydrogel matrix to address the critical challenges of cracking and shrinkage, which affect conventional hydrogels during prolonged use. Traditional hydrogels can experience volumetric shrinkage of up to 46% after extended use, whereas our innovation significantly reduces cracking and shrinkage, limiting the volumetric shrinkage rate to 34%. Looking ahead, we hope to build upon this hydrogel evaporative cooling technology to advance the development and popularisation of emerging photovoltaic technologies.”

Source: The Hong Kong Polytechnic University