: Thermal energy storage (TES) is an important method to store the energy in the form of heat by passing hot heat transfer fluid into the storage domain, where single or double storage tank is usually used to store the heat energy. Thermal energy storage systems could help in integrating the energy sources (solar and wind energy) of intermittent nature and thus providing continuous energy based on the demand. In the present study, a lab scale storage vessel is used with 8" diameter and 23.63" height. Air is used as working fluid with inlet temperature of 95 and gravel is used as storage materials. A numerical model was built using finite element method to solve governing equations. COMSOL Multiphysics software is used to solve the problem numerically and validate the experimental results. The focus of the present study is on the analysis of heat losses to the ambient and their influence on the thermal performance and storage efficiency. The amount of heat loss rate is calculated which a significant parameter to quantify the system performance. Therefore, the main studied parameters are temperature, energy and efficiency of the storage system. The amount of energy stored into the bed is low due to the heat losses based on the experimental and numerical results. Charging efficiency is 43.3% at 0.0004 kg/s and 55% at 0.006 kg/s. The heat loss rate per unit area increases with the increase the time, leading to a reduction in thermal performance
Mohammad M.S. Al-Azawii (Mon,) studied this question.