Optimization of building envelope latent heat storage integration based on internal surface solar insolation profiles

Phase change materials (PCMs) utilize solar energy for latent heat storage (LHS), a method of storing thermal energy through a material’s solid to liquid phase change. When LHS systems are implemented in buildings the thermal energy stored and released during phase changes provides passive temperature regulation and reductions in total conditioning loads. Often, in PCM installations, the PCM is uniformly distributed across entire interior surfaces of a space disregarding the opportunity to optimize PCM placement based on daily and annual solar geometry trends. Strategic placement of PCM within interior surfaces can maximize solar energy storage while reducing material and implementation costs. The objective of this study was to determine ideal thermal storage placement within building spaces based on direct solar radiation rays. A MATLAB model which utilizes cartesian coordinates and solar ray tracing was developed to generate interior surface insolation exposure maps and was validated with ESP-r. The MATLAB model demonstrated a strong correlation with the insolation analysis tool used by ESP-r, thus validating the insolation exposure maps generated by the model. In general, it was found that for a small cubic space with a south facing window in the northern hemisphere, the floor received the largest portion of insolation exposure on an annual basis. Within this surface, northern and southern subsections received the largest portions of insolation exposure for typical heating and cooling seasons respectively, indicating the PCM placement could be tailored to subsections of the floor to optimize its performance during distinct conditioning periods.