Improvement in flowability of thermo-chemical storage material by using nanostructured additives

Abstract

Thermal energy storage is an advancing technology for storing energy that encourages clean energy systems without adversely affecting the environment. This technology allows us to use energy at different times by storing it temporarily. For example in a non-conventional energy source like solar thermal power plant, all its energy is produced during broad day light. The excess energy produced during a sunny day is usually stored in the thermal storage materials, which can later be used in the night to generate electricity. One such advantageous way of storing energy is through thermo-chemical storage. In a space craving society, high storage capability makes it an efficient way to store energy. However at present thermo-chemical storage is in its elementary stage, where in its limited to only one pilot scale system. Considering the thermodynamics and kinetics it has been shown that CaO/Ca(OH)2 reaction system is a potential gas/solid thermochemical heat storage system. However the behavior in a lab sized non-moving bed reactor was mainly dominated by heat and mass transfer limitations arising due to small particle size and changes in bulk properties. This was overcome to a certain level using a moving bed reactor but due to the change in the reactor type the flowability factor dominated adversely. Nevertheless during the recent studies at DLR it was found out that small amount of industrial grade SiO2 (Aerosil®) nanoparticles would enhance the flowability of Ca(OH)2 in a considerable way. But in contrast it effects the heat development leading to low thermal efficiency due to the formation of inert side products. In this study it is found out that small amount of nanostructured Al2O3 (Aeroxide®) not only plays a significant role in stabilizing cyclability and bulk properties but also contributes to the overall heat development.