Use of multiple storage elements to improve the second law efficiency of a thermal energy storage system. Part I: Analysis of the storage process

Abstract

This investigation explores the possibility of improving the thermodynamic efficiency of a sensible heat thermal energy storage system by employing multiple storage units in series. Specifically, the practically-important systems composed of two storage units connected in series are investigated in detail. The paper is presented in two parts. Part I contains a detailed definition of the problem and the analysis of the storage process. The completion of the analytical model and presentation of the results are given in Part II.