Performance optimization of a thermally integrated pumped thermal electricity storage system based on finite time thermodynamics

Abstract The performance of thermally integrated pumped thermal electricity storage is fundamentally governed by internal thermodynamic irreversibilities. This study establishes a rigorous finite-time thermodynamic framework to analyze and optimize a system coupling a high-temperature heat pump with an organic Rankine cycle. By incorporating finite-rate heat transfer and annualized capital cost constraints, a comprehensive model is developed to evaluate the system’s round-trip efficiency. Parametric investigations demonstrate that the round-trip efficiency reaches a maximum of 71.29 % under optimal operating temperatures, though it remains highly sensitive to variations in storage temperature. The charge-discharge duration ratio is identified as a governing determinant, with the round-trip efficiency exhibiting a declining trend as this ratio increases. Furthermore, the synergy of internal heat transfer matching, quantified by specific conductance coefficients, proves crucial for performance enhancement. Global irreversibility is minimized under a symmetric configuration where the heat transfer conductance of the heat pump and the power cycle are balanced. Thermoeconomic optimization reveals a distinct performance peak, with the round-trip efficiency reaching 63.59 % at optimal dimensionless cost coefficients, forming a narrow “efficiency ridge” in the design space. This work provides a foundational theoretical basis for the optimization of irreversible pumped thermal electricity storage systems within the realm of non-equilibrium thermodynamics.