The Hong Kong Polytechnic University team has developed a hydrogel coating to mitigate PV hot spots without modifying module circuitry
The evaporative cooling layer is said to have reduced hot-spot temperature and increased power output
Hydroxyethyl cellulose and fibrous materials were incorporated into the hydrogel to reduce cracking and improve structural stability
Hot spots are a known challenge in solar modules and can arise from factors such as partial shading, cell mismatch, or internal defects. These conditions create localized heating, which reduces output power and accelerates module degradation. In severe cases, hot spots have also been associated with fire risks. Thermal management is one approach to mitigating the impact of hot spots.
Researchers at The Hong Kong Polytechnic University (PolyU) have developed a simple, cost-effective solution called hydrogel coating technology. The study was led by Prof. Yan Jinyue Jerry, Chair Professor of Energy and Buildings, together with Dr. Liu Junwei from the Department of Building Environment and Energy Engineering. Applying the hydrogel coating to the module is reported to reduce hot-spot temperatures by up to 16°C, resulting in an up to 13% increase in power output under test conditions.
The hydrogel coating is applied externally as an evaporative cooling layer and does not require modification of the module’s existing electrical circuit design. The research also claims that when deployed in rooftop and building-integrated photovoltaic (BIPV) systems, the coating could mitigate nearly half of the power losses associated with hot spots.
To improve durability, the researchers incorporated the natural polymer hydroxyethyl cellulose together with a fibrous reinforcement material described as leafy cotton thread into the hydrogel matrix. Conventional often develop cracks and shrink over time under prolonged outdoor exposure. Traditional hydrogels often develop cracks and shrink over time under prolonged outdoor exposure. The team reports that the modified formulation reduces volumetric shrinkage from up to 46% in conventional hydrogels to approximately 34%. Further development of the evaporative cooling concept could support broader applications in emerging photovoltaic technologies, according to Dr. Liu.
