Angular-Dependent Energy-Saving Smart Windows.

Abstract

Windows are responsible for nearly 50% of the building's heat loss. Most current smart window designs solely consider the season-accompanied temperature change but often overlook the solar zenith angle variation. This work addresses this critical gap by leveraging the potential of dynamic metasurfaces and engineering the angular and thermal dual-responsiveness into structural engineering via scalable and industrially compatible mesh printing and spray-coating. The season-dependent solar/thermal radiation dual-modulation smart window, which is composed of a structured reconfigured vanadium dioxide (VO₂) array-based Fabry-Perot resonator, dynamically responds to variations in both solar zenith angle and temperature. The proposed smart window achieves promising luminance transmittance (36.8%), solar modulation (30.8%), and broadband infrared emissivity modulation (0.4). It outperforms the commercial low-emissivity glass and the state-of-the-art designs in energy-saving performance simulation and daylight illumination. Furthermore, the device shows promising color rendering performance and near-daylight color temperature, ensuring superior visual comfort and color neutrality over conventional smart windows. The integration of metasurfaces and phase-change materials provides a promising strategy to dynamically modulate optical responses across different wavelengths, which could have potentially wide applications not limited to energy-saving building facades.