A smart window assembled with energy storage and optical modulation capability for building energy saving

Phase change materials (PCM) hold promise for enhancing the performance of building transparent envelope structures. Using PCM alone in window lacks the ability to regulate the indoor light environment, a drawback that photochromic materials can effectively address. Herein, this study successfully synthesized a novel light-modulating phase change material named SPCM@PC-film through the spinning drop method, by combining shaped phase change material (SPCM) with photochromic film (PC film). The transmittance of this composite material reaches 62.10 % under high-temperature conditions, which can fully meet indoor lighting requirements. Compared with SPCM, SPCM@PC-film exhibits significantly lower transmittance for infrared and ultraviolet rays, demonstrating excellent light-blocking performance. A comparative analysis of the regulatory effects of SPCM smart windows (W1) and SPCM@PC-film smart windows (W2 and W3) on indoor thermal and optical environments revealed that W2 achieved the optimal performance, with the PC film facing the outdoor side. W2 not only effectively reduced indoor temperature but also maintained indoor illumination. Furthermore, under simulated outdoor conditions in summer, W2 reduced indoor temperature by up to 1.66 ℃ while keeping indoor illumination stable within 2000 lx. Moreover, during the noon period, W2 cut indoor temperature by 2.75 ℃ at most and illumination by 1088 lx, maintaining it at 1704 lx. These results fully demonstrate that the SPCM@PC-film smart window has the ability to create a more comfortable indoor thermal and optical environment.