[Objective] To address the issues of insufficient renewable energy integration into the power grid and the high exhaust steam loss in coal-fired power units

a novel Carnot Battery system integrated with a steam ejector is proposed to provide a technical solution for the flexibility transformation of coal-fired units. [Methods] This study designed two new systems

System Ⅰ and Ⅱ

utilizing turbine exhaust steam and extraction steam as low-temperature heat sources. System Ⅱ introduces a steam ejector

which uses exhaust from the intermediate-pressure turbine to entrain the exhaust steam

thereby increasing the cold source temperature of the heat storage cycle. Based on the EBSILON Professional

thermodynamic modeling was conducted to compare the coefficient of performance(CCOP)

round-trip efficiency(ηRTE)

and exergy loss of each system

followed by a techno-economic assessment. [Results] Thermodynamic analysis indicates that the exhaust steam losses of System Ⅰ and Ⅱ are reduced by 38.19 MW and 39.62 MW

respectively

compared to the reference system. Benefiting from the elevated cold source temperature

the CCOP of both systems increased to 1.36 and 1.42. Sensitivity analysis shows that System Ⅱ achieves an optimal round-trip efficiency of 61.51% at a cold source outlet temperature of 55 ℃

an improvement of 2.11 percentage points over the reference system. In terms of techno-economic performance

System Ⅱ performs best

with a dynamic payback period of 9.44 years and a levelized cost of storage as low as 2 094.59 yuan/(MW·h). [Conclusion] The novel System Ⅱ not only effectively reduces energy consumption and improves energy storage efficiency but also demonstrates significant economic competitiveness

which is of great importance for promoting the low-carbon transition of China's energy industry.