Nowadays, due to the increasing demand for energy and the limitations of fossil fuels as non-renewable and environmentally polluting sources, the need for using renewable energy sources is felt more than ever. One of the energy sources that is increasingly being used is thermal energy. Thermal energy storage systems provide the necessary potential for energy saving and reducing the negative effects of energy consumption on the environment. Thermal energy can be stored in materials and various systems by two methods of sensible and latent heat. One of the most important and common methods of thermal energy storage is the use of phase change materials. These materials store thermal energy as latent heat during phase change and release energy when needed. Phase change materials adapt themselves to thermal fluctuations naturally and intelligently without the use of mechanical equipment and only through their inherent tendency to phase change, resulting in energy savings. The problem that reduces the performance of these materials is their low specific heat capacity and thermal conductivity coefficient. In this study, paraffin and eutectic salt were used as phase change materials by the self-assembly method on a calcium carbonate shell bed to facilitate heat transfer. The resulting products of the synthesis included organic-mineral and mineral-mineral microcapsules. The microstructure images obtained from the dilute suspension showed a suitable distribution of microcapsules compared to the thick suspension and sediment. Field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were performed to check the morphology, phase and ensure the formation of bonds. Also, differential scanning calorimetry (DSC) and thermal conductivity tests were performed to eva‎luate the thermal behavior of microcapsules such as melting point, freezing point and heat capacity. The results show that the microstructure images obtained from the dilute suspension showed a proper distribution of microcapsules compared to the thick suspension and sediment. On the other hand, the use of vacuum atmosphere oven improved the morphology of microcapsules compared to air atmosphere due to the removal of the surface tension factor. The results of the differential scanning calorimetry test showed that the mineral-mineral microcapsules obtained from the suspension have good chemical compatibility and thermal stability in the temperature range of 400-800 degrees Celsius. The microcapsules in the suspension, having a high latent heat, showed the ability to store thermal energy at a high temperature. In the thermal conductivity test, the suspension containing mineral-mineral microcapsules had a higher thermal conductivity coefficient than the sediment at different temperatures. Therefore, microcapsules of inorganic-inorganic phase change materials obtained from suspension have a high capability for thermal energy storage applications.

علي اشرفي

مهران نحوي , عباس بهرامي