Light-transmitting and energy-storing integrated PEG-HPMC phase change film for transparent building envelopes: Preparation, properties, and thermal regulation simulation

Phase-change materials (PCMs) show great potential for energy conservation in buildings; however, traditional PCMs are primarily used in non-transparent building envelopes and cannot meet the light transmission requirements of transparent building envelopes. Polyethylene glycol (PEG), a milky-white, translucent phase-change material, offers potential advantages for energy conservation in transparent building envelopes due to its high energy storage density and suitable phase-change temperature. Hydroxypropyl methylcellulose (HPMC) is a widely used film-forming matrix that offers excellent light transmittance, film-forming properties, and chemical stability, making it highly suitable as a support matrix for functional composite films. Therefore, this study utilized polyethylene glycol (PEG) as the phase change material and hydroxypropyl methylcellulose (HPMC) as the matrix to prepare a PEG-HPMC composite phase change film with integrated light transmission and energy storage capabilities. Through systematic characterization of chemical compatibility, microstructure, thermal properties, and light transmittance, the study revealed the influence of PEG loading on the synergistic interaction between optical and thermal properties, and further analyzed its thermal storage and temperature regulation characteristics using numerical simulation methods. The results show that PEG is uniformly dispersed in the HPMC matrix with good compatibility. At a PEG content of 60 wt%, the film exhibits a phase change enthalpy of 47.68 J/g and an average visible light transmittance of 62%, demonstrating excellent optical and thermal storage properties. In Xi'an, a 5-millimeter-thick PEG-HPMC film can reduce the temperature of the inner surface of the glass by 0.87°C. This indicates that the film can effectively improve the thermal inertia of transparent building envelopes, reduce temperature fluctuations, and offer a potential solution for lowering cooling loads in the summer. This study provides experimental and technical references for the development of integrated light-transmitting and energy-storage phase change films for transparent building envelopes, thereby supporting building energy conservation and green, low-carbon development.