Use of multiple storage elements to improve the second law efficiency of a thermal energy storage system. Part II: Completion of the analysis and presentation of results

Abstract

This work investigates the use of multiple storage units connected in series to improve the thermodynamic efficiency of a sensible heat thermal energy storage system. The study is focused on two-element systems which are shown to have entropy generation numbers up to 38% smaller than those of the corresponding single-storage-element systems. Thus, the use of only two storage elements in series can provide rather dramatic increases in the thermodynamic efficiency of a thermal energy storage system. Also, the heat exchanger sizes (NTU's) predicted for the two-element systems are shown to be small enough to be practical.