Optical path model and energy performance optimization of aerogel glazing system filled with aerogel granules

Abstract

Aerogel glazing system (AGS) is an advanced energy-efficient glazing system. According to Lambert-Beer Law, the optical path is a significant parameter that influences the optical performance of AGS, and thus influences the thermal-energy performance. However, the optical path of the granular aerogel layer in AGS has never been calculated before. In this study, a model was newly proposed to calculate the optical path of the granular aerogel layer. Firstly, the optical path of a single aerogel granule was calculated through geometrical optics. Then, the inhomogeneous distribution of aerogel granules was transformed to a homogeneous distribution through an equivalent model. Finally, the optical path of the aerogel layer was calculated by integration. The calculated optical path was utilized to simulate the spectral transmittance of different AGSs which were compared to the experimental results to validate the accuracy of the model. The results showed that the maximum difference between the simulated value and measured value of solar transmittance is 2.1 %. The results also indicated that the influence of the granule diameter on solar transmittance is slighter than the filling thickness. The energy performances of AGSs with different aerogel granules and different filling thicknesses were also simulated and evaluated under different weather conditions. The results showed that P1F16 (the diameter is 1 mm and the filling thickness is 16 mm) could reduce 22 % heat loss/gain when facing horizon and 10 % heat loss/gain when facing east and west in hot summer and cold winter region. The results also showed that P1F16 could reduce 17.36 % heat gain in the whole year in hot summer and warm winter region. It is also noticed that changing the aerogel granule’s diameter and the filling thickness has little effect on the energy performance of aerogel glazing system when faced north orientation.