As the world transitions from fossil fuels to sustainable, green, and clean energy, photovoltaic (PV) technology has emerged as a critical method for harnessing renewable energy. With its high efficiency, low operational costs, and long lifespan, PV systems have garnered significant attention. However, in tropical regions, high operating temperatures and intense solar radiation often compromise the efficiency and durability of these systems. Therefore, it is essential to find effective and convenient cooling technologies for solar cells.
This research introduces a sodium polyacrylate-lithium chloride (PAAS-LiCl) composite material and outlines its streamlined manufacturing process. This material serves as a low-cost evaporative cooling layer attached to the back of photovoltaic panels. It utilizes the hygroscopic properties of the desiccant to absorb moisture at night and achieve cooling through evaporation during the day. Experimental results demonstrated that a 10 mm thick hydrogel layer could achieve an evaporative cooling power of 373 W/m² under laboratory conditions. In an environment with a temperature of 38°C, this cooling layer can reduce peak temperature by 14.1°C, thereby enhancing the maximum output power of the solar panels by 12.9%. This cooling strategy has the potential to extend the lifespan of photovoltaic panels by over 200% and reduce electricity costs by 18%. Combining this passive cooling strategy with durable hydrogel materials and scalable manufacturing processes provides a viable solution for large-scale deployment in solar power plants.
The related work titled Streamlined fabrication of an inexpensive hygroscopic composite for low maintenance evaporative cooling of solar panels was published in Mater. Sci. Eng. R-Rep.. This study proposes a passive cooling strategy based on an adsorption-evaporation mechanism by attaching the PAAS-LiCl composite hydrogel to the back of solar cells, effectively achieving a daily cooling cycle (Figure 1).
A simplified preparation process without crosslinking agents was established, which produced a composite material exhibiting excellent moisture absorption capacity, structural stability, and environmental adaptability under high humidity conditions (Figure 2). Indoor simulation experiments confirmed its evaporative cooling efficiency, achieving a peak cooling power of 247 W/m² and a temperature drop of 11.8°C under 1 kW/m² solar irradiation (Figure 3). Outdoor testing over 21 days showed that this cooling layer achieved a maximum temperature reduction of 14.1°C and a 12.9% increase in photovoltaic conversion efficiency in an environment of 37°C and 53% relative humidity, demonstrating sustained moisture absorption and evaporation cycling capabilities (Figure 4).
Economic and stability analyses further indicate that this hydrogel material is low-cost and supports recyclability. It maintains over 90% performance even after a year of aging and exposure to heavy rain, meeting the demands for long-term outdoor deployment (Figure 5).
Summary: This study presents an efficient method for manufacturing PAAS-LiCl composite materials, which passively cool photovoltaic cells by absorbing atmospheric moisture at night and evaporating during the day, all while maintaining low maintenance costs. The hydrogel composite material employs a more economical synthesis method, enhancing its feasibility for widespread application. Its solid-state structure can be directly adhered to the back of photovoltaic panels without additional adhesives, reliably supporting weight changes due to nighttime moisture absorption and rain exposure, significantly reducing maintenance needs. Notably, due to the equilibrium effect of LiCl, the moisture stored in the hydrogel is gradually released during the day, eliminating the need for frequent replacement of the hydrogel film for better cooling performance. This hydrogel, integrated into solar panels, can significantly lower temperatures during the day, achieving a maximum drop of 14.1°C and enhancing power conversion efficiency from 13.1% to 14.7%. It can effectively reabsorb moisture overnight, exhibiting resilient regenerative cycling capabilities suitable for various climate conditions. This cooling strategy is expected to extend the lifespan of photovoltaic panels by over 200% and reduce the levelized cost of electricity by 18%. Its flexibility allows for integration into various designs, making it suitable for solar power plants and heat-prone applications, ultimately increasing energy output and extending the lifespan of solar panels.
Paper information: Fang H., Dang S., Kumar P., et al. Streamlined fabrication of an inexpensive hygroscopic composite for low maintenance evaporative cooling of solar panels. Mater. Sci. Eng. R-Rep. 2025, 165: 101016. https://doi.org/10.1016/j.mser.2025.101016.
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