Analysis of the discharge process of a TES-based electricity storage system
Matteo Pecchini, Simone Peccolo, Alberto Benato, Francesco De Vanna, Anna Stoppato
Abstract
Carnot battery is considered one of the most promising technologies for large-scale electricity storage. Among the available configurations, the so-called Integrated Energy Storage System (I-ESS) demonstrated its ability to compete with other large-scale storage technologies, such as pumped hydro and compressed air energy storage. However, an investigation that focusses on the performance of Brayton-based Carnot batteries under part-load conditions and adopts an off-design mathematical model is still lacking in the literature. Therefore, to predict the behaviour in part load, the characteristic curves of the turbine and compressor are included in the mathematical model of the I-ESS in conjunction with a properly tuned control system. In addition, to highlight the need to adopt off-design models of critical devices, a comparison between the developed model and various simplified models has also been performed. The results show that the average discharge efficiency of the I-ESS reaches 27%, while the maximum depth of discharge is 64%. When using simplified models, the error in the depth of discharge calculation varies from 7 to 23%. Therefore, this study highlights the crucial importance of adopting an off-design model to better predict the behaviour and performance of Brayton-based Carnot batteries without overestimating parameters such as the depth of discharge or the electricity production. • The discharge performance of an innovative configuration of Carnot battery is investigated. • The off-design model of the system has been built with accurate models of the turbomachinery. • The discharge efficiency, the depth of discharge, and the electricity production is evaluated under different operating conditions. • The performance of the off-design model is compared with that obtained using simplified models of the system. • The comparison between models shows that the error in the depth of discharge evaluation can be up to 23% using simplified models.