Enhanced Thermal Performance of Nitrate Salts Composite with Compressed Expanded Graphite for Solar Thermal Energy Storage

This research endeavors to enhance the performance of nitrate salts by incorporating expanded graphite (EG) to develop efficient and sustainable energy storage solutions tailored for medium-temperature range applications. The targeted domains for application encompass industrial processes, solar cooking, and solar power generation. In order to achieve this, a composite phase change material (PCM) is developed by saturating a compressed expanded graphite (CEG) matrix with molten PCM, and CEG is created by compressing EG to achieve the desired porosity. The primary goal is to leverage expanded graphite's high thermal conductivity to improve the composite PCM's overall heat transfer capabilities. The research involves characterizing the thermal properties of nitrate salts and the composite PCM, including measurements of melting and solidification temperatures, latent heat capacity, and thermal conductivity. These measurements are carried out using established experimental techniques to ensure accuracy and reliability. Notably, the study evaluates the thermo-physical properties of PCM-CEG composites across various temperature ranges of nitrate salts. The findings reveal a significant enhancement in thermal conductivity when expanded graphite is introduced into the composite. Differential scanning calorimetry (DSC) is used to assess the effective latent heat capacity and melting temperature of the PCM-CEG composite. It is observed that the effective latent heat capacity closely corresponds to the mass fraction of PCM in the composite, and the incorporation of graphite does not significantly impact the melting temperature of the PCM.