Fabrication of energy saving windows via solution process

• Main Author: Zhou, Chengzhi
• Other Authors: Chan Siew Hwa
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/155792
• Institution: Nanyang Technological University

The building systems consume over 40% of total energy. Windows are the least energy-efficient part, as heat is always transferred in the undesired direction. Therefore, the development of energy-saving windows has obtained tremendous attentions over the past decades. There are various fabrication methods for energy-saving windows; the solution-based process is one of the most promising ones with the advantages of low fabrication cost and facile scalability. In this thesis, the fabrication of energy-saving windows via solution-based methods have been investigated. The energy-saving performance has been enhanced by, for the first time, introducing the solar elevation angle as a new parameter, as well as the customization design. Meanwhile, a bamboo-derived transparent composite has been developed, which combines the low-emissivity coating and enhanced radiative cooling (RC), which has rarely been explored for window applications in the literature. A vanadium dioxide (VO2) based smart window for adaptive solar modulations has been presented in the first project. Although VO2 is recognized as the most promising thermochromic material for energy-saving windows, the high transition temperature (τc), low luminous transmission (Tlum), and solar modulation (ΔTsol) impose invertible challenges for commercialization. Conventional smart window research assumes solar radiation as a static process, which is not valid as most regions receive solar radiation at various angles in different seasons. For the first time, solar elevation angle is considered, and 3D printing technology is employed to fabricate tilted microstructures for modulating solar transmission dynamically. The issues of compromised Tlum and ΔTsol, high τc are tackled by introducing W-doped VO2 and customized design. The energy consumption simulations prove the efficiency of such dynamic modulation. best reported thermochromic properties were achieved, where τc = 40 °C, Tlum(average) = 40.8%, ΔTsol = 23.3%. In the conventional smart windows, the long-wavelength infrared (LWIR) has not been taken into consideration. In the second project, the transparent bamboo composite with high radiative cooling has been fabricated via a simple solution-based process. The LWIR emissivity(εLWIR) of 0.3 has been achieved for the side facing indoor environment to prevent the heat exchange. The εLWIR of near unity (0.95) has been achieved for the other side to promote the radiative cooling. The energy consumption simulations have been performed in Singapore, suggesting up to 89% enhancement for the energy-saving performance, comparing with the commercial low-E glass.