Performance study of a packed bed in a closed loop thermal energy storage system

In order to reduce the cost of thermal energy recovery, a packed bed closed loop thermal energy storage system has been proposed and is investigated. The main components of the system include a closed air cycle, a heat exchanger, and a packed bed storage column. This paper is aimed at analyzing the performance of the packed bed in the system. Packed bed column experiments have been carried out to provide a basic understanding of the thermal energy storage process in the closed loop system with different flow directions in the packed bed and different energy storage temperatures. The detailed temperature distributions in the interior of the packed bed and the temperature differences along the axial and radial directions are presented. The influence of flow direction within the packed bed and structure of the gas distributer on the temperature distribution are also analyzed. The performance of packed beds in the closed loop thermal energy storage system is then evaluated based on energy and exergy analyses. These experimental results would be useful in the optimal design of the structure of packed bed columns and thus closed loop thermal energy storage systems.