Energy and exergy analyses of a closed thermochemical energy storage system: Methodology and illustrative application

Abstract

Thermal energy storage (TES) is an advanced technology for storing thermal energy that can mitigate environmental impacts and facilitate more efficient and clean energy systems. Among various types of TES systems, thermochemical TES is a promising method with the potential for higher energy storage densities and greater compactness. The assessment of such systems is enhanced greatly when exergy analysis is used to complement energy analysis. Here, a general closed 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 example are determined to be 50% and 9%, 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.