A research team at The Hong Kong Polytechnic University (PolyU) has developed a simple and affordable hydrogel coating that not only enhances the heat dissipation in solar panels for cooling their "hot spots" effectively, but also increases power generation efficiency, ultimately supporting Hong Kong's goal of achieving urban carbon neutrality. Hot spots, often caused by partial shading, have long been the culprit behind diminishing power generation efficiency of solar panels, compromising the stability of entire power supply systems over time. This PolyU innovation offers an effective and robust solution to a key industry pain point.
The groundbreaking hydrogel cooling technology was developed by a PolyU team led by Prof. YAN Jerry, Chair Professor of Energy and Buildings, together with Dr LIU Junwei, Research Assistant Professor of the Department of Building Environment and Energy Engineering. The team's research showed that after applying the hydrogel coating to solar panels, hot-spot temperatures could be lowered by up to 16°C, with the power output increased by as much as 13%. When applied to "rooftop and building-integrated photovoltaic (BIPV) systems", the hydrogel coating is expected to mitigate nearly half of the power losses caused by hot spots, significantly improving the long-term stability and efficiency of solar photovoltaics for building electricity supplies.
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 demands our attention, as they not only reduce power generation efficiency due to the elevated operating temperatures, but also pose potential fire risks in severe cases. According to existing research that investigated 3.3 million photovoltaic panels, 36.5% exhibited thermal defects with the defective modules registering an average temperature increase of over 21°C, accelerating the ageing and degradation of solar panels. The PolyU hydrogel coating not only delivers excellent cooling performance but also demonstrates outstanding durability, making it suitable for long-term outdoor use.
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."
