Thermochromic Transparent Wood Composites with Highly Efficient Broadband Optical Management Capability for Smart Window Applications

Project: Research

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Windows cause significant energy consumption (20-40%) in buildings because of their poor optical management and thermal insulation. Many previous studies developed various smart windows, such as thermochromic/electrochromic/photochromic smart windows, to reduce the heat gain/loss from/to the environment. However, most windows are made from glass and suffer from being heavy, brittle and poor thermal insulation. In this study, a novel thermochromic transparent wood composite (TTWC) is proposed for window applications that can block solar irradiance in summer, but allow the passing of solar irradiance in winter to maintain a warm indoor environment, reducing the energy needed for indoor heating, cooling and lighting.Besides, the TTWC can also demonstrate high optical transmittance for harvesting daylight, possess excellent thermal insulation capability, and is lightweight with remarkable mechanical strength, high ductility (eliminating safety issues) and is sustainable. This project aims to develop TTWCs and fundamentally study their optical and thermochromic properties to gain a scientific understanding of light scattering with thermochromism in hierarchically microstructured materials (wood). Our preliminary results demonstrated a TTWC with an intelligent optical regulation ability and an average visible transmittance of ~61%. Meanwhile, the solar modulation ability (the difference in solar transmittance between two temperature states) is ~38%, exhibiting promising transparency and thermochromism. Despite these encouraging results, several challenges need to be addressed since the influence of thermochromic particles on broadband optical management in wood is not fully understood, and a TTWC with high solar modulation ability remains undiscovered. This study will first develop a comprehensive optical model, focusing on the fundamental study of light scattering in wood with irregular wood fiber shapes. Next, the optical model will be modified by considering the Mie scattering effects due to the thermochromic particles dispersed in the TTWC. The parameters, such as different types of refractive-index matching materials; various types, concentrations, and particle sizes of thermochromic materials, etc. will be included in the model to estimate the optical and thermochromic properties of TTWCs. Guided by the model, optimized TTWC will be prepared and characterized. The model results will also be directly compared to experimental results. Finally, several model houses equipped with different windows and the optimized TTWC window will be built to evaluate the energy-saving performance under different conditions. Overall, this study will not only reveal the impact of thermochromism on a hierarchically micro-structured material and its related optical and thermochromic characteristics, but also opens new avenues for the development of thermochromic smart windows. 


Project number9043127
Grant typeGRF
Effective start/end date1/01/22 → …