[Objective] With the advancement of China's “dual carbon” goals and the accelerated construction of a new power system characterized by a high proportion of renewable energy

coal-fired power units are undergoing a fundamental transformation from base-load power sources to essential supporting and regulating assets. Enhancing the operational flexibility of these units

particularly their ability to accommodate fluctuating renewable generation

has therefore become an urgent and critical demand. Molten salt thermal energy storage(MSTES) technology

renowned for its significant advantages in large-scale storage capacity

high operational temperatures

and relatively low cost

exhibits a strong compatibility with the dynamic regulation requirements of coal-fired units. Consequently

it is widely regarded as a pivotal and promising technical approach for achieving substantial flexibility enhancements in the power sector. [Methods] To systematically address this challenge

this study proposed and designed three distinct MSTES coupling system configurations for coal-fired units: namely

the steam heating system

the electric-steam hybrid system

and the all-electric heating system. A representative 350 MW supercritical coal-fired unit was selected as the specific research object to ensure the practical relevance and applicability of the findings. The professional thermal system simulation software

EBSILON

was employed to construct high-fidelity models for each coupling configuration. These models underwent a rigorous calibration and verification process against design and operational data

ensuring that the simulation error for all key performance parameters was reliably controlled within an acceptable margin of 5%. Utilizing these validated models

the study conducted a comprehensive comparative analysis

systematically evaluating the peak-shaving capability(deep load reduction)

peak-load boosting capability(increased power output)

and primary frequency regulation performance of the three systems. Beyond technical performance

a detailed economic benefit analysis was performed

calculating and comparing key financial metrics including the static investment payback period

financial net present value(FNPV)

and financial internal rate of return(FIRR) for each option. [Results] The simulation results reveal clear and significant performance differentials among the proposed systems. In terms of peak-shaving performance

which is crucial for absorbing excess renewable power

the ranking is electric heating electric-steam hybrid steam heating. Notably

the electric heating system can reduce the unit's minimum technical load from 50% down to 0(theoretically enabling full shutdown while storing energy)

whereas the hybrid and steam systems lower it to 16.8% and 18.2%

respectively. For peak-load boosting

important for meeting daily high demand

the order is electricsteam hybrid steam heating electric heating. The hybrid and steam systems can boost the peak output from 80% to 100% of unit capacity

while the electric heating system increases it to 83%. Their corresponding sustainable peak output durations are 2 h

1.5 h

and 1.0 h

respectively. Regarding fast frequency regulation

the electric heating and electric-steam hybrid systems perform equally well and are substantially superior to the steam heating system. Both improve the comprehensive frequency regulation performance coefficient from a baseline of 0.98 to 5.7～7.7、5.7～7.7、0.98

indicating a much faster and more significant power response. The steam heating system showed no measurable improvement in this metric. From an economic standpoint

the all-electric heating system demonstrates the most favorable financial profile

with the shortest static payback period of 3.8 years

an FNPV of 285.53 million yuan

and the highest FIRR of 24.2%. The electric-steam hybrid system follows closely(5.0 years

280.09 million yuan

FIRR of 17.5%)

while the steam heating system also remains economically viable with a payback period of 5.2 years

an FNPV of 224.95 million yuan

and an FIRR of 17.0%. [Conclusion] The research results quantitatively elucidate and contrast the distinct performance trade-offs and economic characteristics inherent to different MSTES coupling pathways. The electric heating system offers superior economic returns and excels in deep peak-shaving and frequency response. In contrast

the hybrid system provides the best peak-load boosting capability. The steam heating system

while less flexible

remains a technically and economically feasible option. These detailed findings provide critical technical guidance and a robust

data-driven decision-making framework for power plant operators and planners. They are instrumental in selecting the most appropriate MSTES integration strategy for specific grid service needs

thereby facilitating the effective engineering application of MSTES technology to support the crucial flexibility enhancement of coal-fired power units within the evolving energy landscape.