Photothermal transfer mechanism of aerogel governed by microscopic discrete structures

Owing to extremely low thermal conductivity, silica aerogels have attracted significant attention as advanced materials for improving building energy efficiency. Their microstructure plays a critical role in governing both radiative transfer and thermal conduction processes. However, existing studies rarely provide a consistent evaluation of solar extinction and thermal conductivity based on identical microstructural representations. In this study, a unified microstructural discretization framework is developed to evaluate solar extinction and heat conduction on the same aerogel geometry, using Monte Carlo ray tracing and lattice Boltzmann modeling. The effects of porosity and particle diameter on solar extinction coefficients and thermal conductivity were analyzed. Results for silica aerogels show that porosity and particle diameter both influence solar extinction, whereas heat conduction is primarily governed by porosity. Reducing porosity from 96.8% to 84.9% increases thermal conductivity by about 25%, while a 200% increase in particle diameter leads to only a 6% change. This framework is coupled with a dynamic heat transfer model to evaluate aerogel glazing systems in five typical cities. Compared with low-porosity structures, the optimized configurations demonstrate substantial improvements in annual energy performance, with relative increases of up to 107% in Beijing and 13% in Changsha under the studied conditions. This work provides a general framework for linking microstructure to energy behavior and supports the design of high-performance aerogel glazing systems.