Comparative analysis of hybrid energy storage based on a gas–gas system and a conventional compressed air energy storage based on a recuperated gas turbine round trip efficiency, exergy losses, and heat exchanges start-up losses

Abstract

This paper presents a novel hierarchical gas turbine cycle cooperating with a hybrid compressed air energy storage and thermal energy storage. Conventional compressed air energy storage systems cannot use heat storage because they require recuperated gas turbines to achieve high efficiencies. The novelty of the proposed solution lies in the original combination of compressed air energy storage and heat storage using a system of two gas turbines, the so-called gas–gas system. Moreover, a detailed mathematical model of CAES with TES is presented including an original approach to modelling of CAES charging and discharging processes and recuperative heat exchanger start-up losses. The paper analyses also the influence of the main design parameters, such as electrical power, gas turbine inlet temperature, compressed air storage capacity and discharge time, main heat exchanger mean logarithmic temperature difference, and heat loss in thermal energy storage on machinery and cycle performance. The results of the analysis show, among other: the energy efficiency, carbon dioxide emissions per unit of input and output electric energy, and the main heat exchanger start-up losses during the round trip of charge/discharge cycle. Compared with a reference compressed air energy storage based on a recuperated gas turbine cycle, the proposed cycle achieves 73% less CO2 emission per unit input electric energy and 45% less CO2 emission per unit of output electric energy, while the round trip efficiency is lower by 0.8 pp. The start-up heat loss of the main heat exchanger is reduced by 34%.