Configuration design and peak shaving flexibility evaluation of a novel pumped thermal electricity storage system integrated with in-service thermal power plants based on thermo-economic analysis

The large-scale integration of high-penetration renewable electricity brings substantial challenges to grid security and operational stability. In response, thermo-mechanical energy storage represents a promising technical route to improve the operational flexibility of power systems. This work proposed a novel pumped thermal electricity storage system (PTES), which consists of a high temperature heat pump subsystem based on Brayton cycle, molten salt heat storage units and a Rankine-based thermal power plant. By utilizing the high-temperature heat pump to store electricity and low-grade heat from the thermal power plant, this system effectively decreases the deep peak shaving capacity. Simulation models were developed to analyze the impact of operation parameters during the charging and discharging process, and a system configuration design method targeting diverse optimization objectives is further proposed. Results reveal that the maximum heat engine efficiency of the heat storage system can reach 44.35%, and the coefficient of performance of the heat pump can reach to 1.292 through the parameter optimization of heat pump subsystem. The minimum output power of the PTES can decrease from 30.00% of rated load to 2.22% during the charging process. The overall system achieves a maximum equivalent round-trip efficiency of 53.72%, and the levelized cost of storage is minimized to 67.42 $/MWh, demonstrating both technical and economic viability of the proposed system.