Abstract: The three dimensional models of ordered and disordered pack for phase change storage capsule were established in this paper.The influence of ordered and disordered pack on the heat transfer characteristics of packed bed thermal energy storage system was investigated.A new method to determine the finish time of heat storage is proposed by analyzing the key performance indexes such as heat storage capacity,heat storage time,heat storage efficiency and temperature distribution.The results show that the ordered pack attains the highest performance,disordered pack attains the least heat storage capacity,and stacked pack attains the lowest heat storage efficiency.It is also observed that as the flow rate of heat transfer fluid increases,the thermal storage process accelerates and consequently the heat storage efficiency of packed bed thermal energy storage system decreases.