'Middle East Technical University, Faculty of Architecture'
Abstract
A thermal energy storage unit designed to be used in a solid particle concentrated solar energy system is analysed with the help of a commercial Computational Fluid Dynamics tool. Hydrodynamics of the bubbling fluidized sand bed of which dimensions are 0.28 m x 1 m x 0.025 m to be used as direct contact heat exchanger are modelled and validated. Geldart B type particles with diameter of 275 micron and density of 2500 kg/m3 are used in modelling of bubbling fludized sand bed. Syamlal O’Brien drag model with restitution coefficient of 0.99 and specularity coefficient of 0.1 predicts the reported experimental data well in terms of bed expansion ratio, temporal voidage profile and pressure drop across the bed. According to thermal model results, linear relation between interphase heat transfer coefficient and bed temperature is observed. Lifetime of a single bed is found as about 5000 seconds. The obtained thermal results are used to model a particle based storage system for Ivanpah Solar Power Plant. Air Brayton cycle with thermal efficiency of 0.264 can produce 178 MW electricity for 11.22 hours. For Ivanpah, 26304 metric tons silica sand are found to be required for daily storage. M.S. - Master of Scienc
