Round-trip efficiency and power output of Pumped Thermal Energy systems with realistic component constraints

This paper examines the potential of Pumped Thermal Energy Storage (PTES) systems using a MATLAB/Simulink model, motivated by the discrepancy between round-trip efficiency (RTE) values reported in the literature and those achieved by existing prototypes. Consequently, this work focuses on system configurations that respect temperature limits of currently available turbomachinery. The influence of key loss mechanisms like turbomachinery isentropic efficiency, heat-exchanger losses, and thermal storage losses on the RTE is analyzed. The results show that isentropic losses dominate system performance and lead to unused storage capacity. Turbine efficiency is found to have a stronger impact on performance than compressor efficiency. Heat-exchanger and storage losses also significantly reduce the RTE, while pressure losses play a minor role. In addition it is found that the output power can be substantially lower than the input power, which is critical when defining suitable use cases. A full charge–storage–discharge cycle is simulated using both modest and optimistic efficiency assumptions. Under highly favorable conditions, the maximum RTE is found to be 36.2%. • Modeling of an air-based closed-loop Brayton-PTES system. • Efficiency for PTES systems determined based on realistic component constraints. • Reduction of power output in a PTES system analyzed. • Analysis of storage capacity utilization. • Discharge cycle optimization for high efficiencies.