Use of clays in the latent heat storage and production of shape-stabilized composite phase change materials

In order to meet the ever-increasing energy demand all over the world, it is important to use energy effectively and efficiently or to store it with appropriate processes. Phase change materials (PCMs) are new generation energy storage materials that allow thermal energy to be stored as latent heat and allow large amounts of heat to be stored or released during the phase change from liquid to solid or from solid to liquid. In recent years, various approaches have been applied to eliminate some of the disadvantages of these materials with appropriate methods and to ensure their stability in form. On the other hand, these materials are not suitable for direct use in energy conversion processes due to leakage problems and large volume changes during phase transition. In addition, the performance of PCMs in thermal energy storage systems is significantly limited due to their low thermal conductivity. In this study, the usability of clays used in many industries as support materials in the design of organic-based composite phase change materials was investigated. Organic-based PCM/clay composites were successfully produced in different compositions. Thermal properties of composite PCMs were determined by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). In addition, morphological properties and chemical structures of the obtained composites were investigated using Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR), respectively. The chemical composition of the refractive clay used as support material was determined and lauric acid composite PCMs were prepared in various compositions. The leakproof composite material with the highest PCM content was modified with expanded graphite in order to improve its thermal properties. The thermal conductivity was improved and the leakproof composite was found to have a melting enthalpy of 63.6 J/g and a crystallization enthalpy of -61.7 J/g. It was concluded that the obtained shape-stablized composite can be used in energy storage applications such as solar energy storage and thermoregulation of buildings with its suitable thermal energy storage capacity and phase transition temperatures. Keywords: Thermal energy storage, Phase change material, Heat transfer