Abstract
In the context of global efforts toward energy transition and carbon neutrality, thermal integrated pumped thermal energy storage (TIPTES) systems, especially those utilizing low-grade heat sources, have garnered significant attention due to their large capacity, flexibility, and environmental advantages. This paper explores a TIPTES system that harnesses industrial waste heat as a heat source. The system's heat pump (HP) subcycle and Organic Rankine Cycle (ORC) subcycle are equipped with regenerators to optimize system configuration and enhance efficiency. Five working fluids-R245fa, isobutane, isopentane, MM, and R1336mzz(Z)-are selected for analysis based on parametric evaporation temperature (T (1)) and thermal storage temperature (T (8)).Parameter analysis results reveal that both round-trip efficiency (η (ptp)) and exergy efficiency (η (ex)) increase with rising T (1), with the system using MM demonstrating optimal performance: at T1 of 70 °C, η (ptp) reaches 71.34 %, and η (ex) is 37.42 %. The η (ptp) for each system decreases as T8 increases, with the isobutane-based system showing the slowest decline; η (ptp) remains relatively unaffected by T (8), while η (ex) for the isobutane- and R245fa-based systems initially decreases and then increases with rising T (8).Key system parameters-T (1), T (8), and cold thermal storage temperature (T (7))-are further analyzed in a single-objective optimization focused on round-trip efficiency. Results indicate that the isopentane-based system performs optimally at T (8) of 388.65 K, T (7) of 359.15 K, and T (1) of 338.15 K, achieving a maximum round-trip efficiency of 71.60 %. This study offers theoretical insights to support the future development and application of TIPTES systems.