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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. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a new type of solar energy based power generation system using supercritical carbon dioxide and heat storage. The power generation cycle uses supercritical carbon dioxide as the working fluid and integrates the supercritical carbon dioxide cycle with an efficient high-temperature heat storage. The analysis shows that the new power generation system has significantly higher solar energy conversion efficiency in comparison to the conventional water-based (steam) system. At the same time, the heat storage not only overcomes the intermittent nature of solar energy but also improves the overall system efficiency. The study further reveals that the high temperatures and high pressures are favorable for solar energy storage and power generation. Moreover the expander and the heat storage/regenerator are found to be the key components that determine the overall system performance. [Copyright &y& Elsevier]

Abstract: Electrical energy storage technologies for stationary applications are reviewed. Particular attention is paid to pumped hydroelectric storage, compressed air energy storage, battery, flow battery, fuel cell, solar fuel, superconducting magnetic energy storage, flywheel, capacitor/supercapacitor, and thermal energy storage. Comparison is made among these technologies in terms of technical characteristics, applications and deployment status. [Copyright &y& Elsevier]