Concise and high-precision modeling of PV modules with hygroscopic composite backplates for continuous passive cooling

Passive cooling using hygroscopic composite backplates is a promising approach for effective photovoltaic thermal management. However, accurately modeling their cooling performance remains a challenge, as existing methods often suffer from experimental discrepancies, oversimplified physics, and limited predictive accuracy. To address this, a concise model is established to simulate the heat and mass transfer process and continuous passive cooling performance of polyacrylamide/sodium alginate hydrogels integrated with calcium chloride, and validated with root mean square error less than 2 °C and mean relative error around 3 %, demonstrating enhanced accuracy and reliability. Then, a quantitative analysis of the impacts of salt content, water diffusion coefficient, and protective membranes on cooling performance indicates that moderate salt content and diffusion coefficients enable sustained efficient passive cooling, while the protective membrane's mass transfer resistance is 20 times lower than the air-side resistance, exerting negligible influence. Moreover, a 7-day simulation under different six climates demonstrates that power conversion efficiency relatively increases vary from −0.15 % and 1.03 %, and the greatest cooling effects are in subtropical monsoon and Mediterranean climate with average temperature reductions by 2.3 °C and 2.7 °C respectively. This model can serve as a preliminary tool for estimating the extended cooling effects of composite backplates across various regions and provide fundamental guidance for the design and fabrication of materials.