This paper presents numerical analysis on the performance of latent heat packed bed thermal energy storage system, which is composed of spherical capsules filled with sodium nitrate as phase change material and high temperature synthetic oil (Therminol 66) as Heat Transfer Fluid. The influence of capsule size, fluid temperature (Stefan number), Tank size (length and diameter) and fluid flow rate on the performance of the thermal energy storage system is investigated in the temperature range between 300 and 400 degrees C. The phase change process inside the capsule is modeled by enthalpy formulation method and the flow inside the system is predicted by extended brinkman equation. This model is validated using the already reported models. The ultimate aim of this investigation is to develop a packed bed thermal energy storage model to study and optimize the main components of the storage tank to use in concentrating solar power plants. (c) 2014 The Authors. Published by Elsevier Ltd.