Numerical analysis of phase change materials for use in energy-efficient buildings

Due to the efficient performance in energy storage density, solar thermal energy storage (TES, especially latent type) applications are drawing more attention in the research field of solar energy. Among all of the types of solar thermal storage technologies, the latent heat storage system using phase change materials is the most efficient way of storing thermal energy. It has some dominant factors such as high density energy storage and isothermal operations, i.e., very small temperature range for heat storage and removal. Thus, latent heat storage systems have greater applicability over the other types of TES systems. This chapter initially presents an analysis of a latent-type solar thermal energy storage (TES) system involving some of the important cases carried out comprising the application of ambient conditions with various geometries and working conditions. The analysis is carried out in MATLAB® and COMSOL®, which contains transient simulations of latent heat storage functioning with 1D and 2D modeling. It comprises the validation of numerical 1D analysis with corresponding analytical solution, observation of the change in thermophysical properties at the melting point, etc. Further in this study, the phase change material (PCM) is assumed to be incorporated in a brick wall structure, which can improve its thermal performance. A 1D numerical model on COMSOL Multiphysics is developed to analyze the thermal performance of the PCM-filled brick wall unit. The numerical model and the adopted hypotheses are illustrated in detail. The comparison between temperature distributions of a simple brick wall and a brick wall with a PCM layer is presented. The results show that using the numerical tool, it can be observed that the thermal performance of the PCM-filled brick wall is efficient over the simple brick wall without PCM. This concept of the PCM-impregnated building structure is found to be successful in shifting the energy requirement of the equipped building sector from a high peak electricity demand period to an off-peak period.