Energy Storage Capacity of Microencapsulated Phase Change Materials

The problem of phase change processes in confined systems for thermal energy storage has been addressed by several authors. Thermomechanical models have been developed to estimate key parameters such as melting times and energy storage capacity of confined phase change materials. Although volume expansion is limited through encapsulation, the density changes during melting have a significant impact on latent heat storage physics. Recently, it has been shown that within the incompressible limit, inner pressure, latent heat, energy density, and melting times are ill-estimated. Melting rates are profoundly affected by the compressibility of the solid phase. In this work, two configurations of confined phase change materials are considered: microencapsulated salts in a shell with a free outer surface and microcapsules with a fixed shell-matrix interface. It is found that although the latent and sensible heat absorbed decrease with the shell’s thickness, the energy density is greatly improved when the proposed model is applied to salts with higher compressibilities. Finally, it is found that close to the isochoric limit, melting times are significantly increased, showing a major disadvantage in composite salt-matrix systems.