Energy and Exergy Analyses of an Open Thermochemical Energy Storage System: Methodology and Illustrative Application

Abstract

Thermal energy storage (TES) is a developed technology for storing thermal energy that can diminish environ- mental impacts and provide more efficient and environmentally friendly energy systems. Among various types of TES systems, thermochemical TES is an advanced method with the potential for higher energy storage densities and more compact systems. The evaluation of such systems is improved significantly when exergy analysis is used to complement energy analysis. Here, a general open thermochemical TES is investigated using energy and exergy analyses. An example using experimental data is presented to illustrate the analyses. Efficiencies are determined for the overall TES cycle and its charging, storing and discharging processes. The overall energy and exergy efficiencies for system considered in the illustrative example are determined to be 69% and 23%, respectively. This result indicates that the efficiency of the thermochemical TES based on exergy is much lower than that based on energy, and that there is a significant margin for loss reduction and efficiency improvement.