3D printed smart windows for adaptive solar modulations

Vanadium dioxide (VO2) based thermochromic smart window is considered as the most promising approach for economizing building energy consumption. However, the high phase transition temperature (τc), low luminous transmission (Tlum), and solar modulation (ΔTsol) impose an invertible challenge for commercialization. Currently, smart window research surprisingly assumes that the sunlight radiates in one direction which is obviously 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. To maximize energy-saving performance, the architecture of the structures (tilt, thickness, spacing, and width) and tungsten (W) doped VO2 can be custom-designed according to the solar elevation angle variation at the midday between seasons and tackle the issue of compromised Tlum and ΔTsol with W-doping. The energy consumption simulations in different cities prove the efficiency of such dynamic modulation. This first attempt to adaptively regulate the solar modulation by considering the solar elevation angle together with one of the best reported thermochromic properties (τc = 40 °C, Tlum(average) = 40.8%, ΔTsol = 23.3%) may open a new era of real-world-scenario smart window research.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Accepted versio