Effects of Cavity-Shapes in 3D printed PCM encapsulation plates on sustainable thermal energy efficiency in buildings

This study investigates the integration of phase change materials (PCMs) into 3D-printed polylactic acid (PLA) plates to enhance thermal energy storage and improve energy efficiency in buildings. Capric acid (CA; assay: >= 99.0 %) was selected due to its high latent heat and reliable phase-change behavior. The PCM was encapsulated in cavity arrays of cubic, cylindrical, and spherical geometries, each consisting of 400 uniformly distributed voids fabricated via additive manufacturing. Thermal behavior of the PCM was characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Thermal performance was assessed through full-scale prototype test rooms subjected to real outdoor conditions across daily solar heating and night cooling cycles. Results demonstrated that spherical cavities led to superior insulation performance, reducing heat loss by 5.35 %-11.03 % and improving heat retention by 2.69 %-4.77 % compared to cubic and cylindrical shapes. The spherical configuration also maintained the most stable and narrow phase-change temperature window, consistently between 29.7 degrees C and 30.3 degrees C. Key transient heat diffusion parameters, including Biot number (Bi) and thermal diffusion time scale (td), were found to be significantly lower for spherical cavities, indicating more effective energy storage and release. This geometric advantage minimized indoor temperature fluctuations and improved thermal comfort. The use of 3D-printed PLA plates with tailored cavity designs represents a novel and scalable approach to passive thermal regulation. The findings underscore the promise of integrating PCMs into printed structures for sustainable building envelope applications, especially under climate-responsive design strategies.