Storage of Solar Energy by Application of Thermally Stratified Phase Change Materials. Experimental Research and Optimization

Main aspect when solar thermal energy storage (TES) is considered is thermal storage capacity in form of sensible heat, latent heat or chemical energy. In case of solar systems, solar TES provide a solution for mismatch between energy supply and energy demand. Higher capacity reduces the size of the system and increases overall efficiency [1]. Water is used in almost every system as working fluid due to characteristics like nontoxicity, abundance, high specific heat and suitability for wide range of heating applications [2]. Since the temperatures that occur in solar heat storage is above 0 °C and below 100 °C, no phase change of water can occur and energy is stored only as sensible heat. Wide variety of phase change materials (PCM) have been created and accepted as suitable to make use of latent heat storage (LHS). While use of phase change materials in latent thermal heat storage have been studied thoroughly, a lot less studies have been looking into use of different melting temperature phase change materials to enhance the efficiency of solar system. Solar systems in many cases are used in existing buildings where available space is limited. By increasing efficiency and energy density, it is possible to store more and take less space