Multi-objective optimization of adaptive radiative smart window regulated with phase change materials for interior visible lighting and building energy management

Visible lighting and energy-saving are dual needs of energy efficiency and occupant comfort in modern buildings. In this study, a smart window based on phase-change material VO₂ is designed and optimized to address the critical challenges in building energy management. The proposed phase-adaptive radiative (PAR) coating is a multilayer nanostructure consisting of TiO₂/VO₂/TiO₂/Ag and polydimethylsiloxane (PDMS). For different VO₂ phases, visible transmittance T_vis > 0.6 and emissivity difference in the atmospheric window Δε_AW = 0.422 can be achieved, which means the PAR window can transfer interior heat to the outside through thermal radiation for cooling or minimize thermal emission for insulation, while ensuring the transmission of visible light for natural daylighting. Compared to normal glass, the PAR window has an average temperature drop of 14.8°C. The year-round energy-saving calculation for four different cities in China indicates that the PAR window can save 22%–32% of the annual cooling and heating energy consumption by seamlessly transitioning between two phases of VO₂ modes. The multi-objective optimization of the phase-adaptive radiative smart window provides a potential strategy for energy saving.