[Objective] With the increasing penetration of renewable energy in power systems

conventional coal-fired units are required to operate more flexibly and provide enhanced peak-shaving capability. To address this challenge

this study proposes a solar-coal complementary power generation system that integrates a tower-type concentrated solar power system with an extraction steam thermal energy storage scheme. The objective is to improve the operational flexibility and peak regulation performance of coal-fired units while maintaining favorable economic performance

thereby facilitating the large-scale integration of renewable energy into power grids. [Methods] Based on measured hourly direct normal irradiance(DNI) data over a full year from a representative region in Inner Mongolia

a comprehensive annual performance and economic evaluation model of the proposed system is established. The model considers the coupled operation of the coal-fired unit

the tower solar field

and the molten salt thermal storage system under varying solar and load conditions. The steam extraction rate and thermal storage duration are selected as key decision variables. A multi-objective optimization framework is developed to simultaneously maximize the annual peak-shaving capacity and annual economic benefit while minimizing the total investment. The non-dominated sorting genetic algorithm II(NSGA-II) is employed to obtain the Pareto-optimal solution set. Subsequently

the technique for order preference by similarity to ideal solution(TOPSIS) is applied to rank the Pareto solutions and identify the optimal compromise scheme suitable for engineering implementation. [Results] The optimization results indicate that under the 50% turbine heat acceptance(THA) operating condition

the optimal configuration corresponds to a thermal storage duration of 5.28 h and a steam extraction rate of 102.46 t/h. Under this configuration

the annual peak-shaving capacity reaches 22.16 MW

with an annual revenue of 40.14 million yuan

a total investment of 229.11 million yuan

and a net present value(NPV) of 142.49 million yuan. In addition

under the 30% boiler maximum continuous rating(BMCR) and 25% BMCR operating conditions

the net present values are 81.50 million yuan and 113.00 million yuan

respectively

demonstrating that the system maintains good economic performance even at deep peak-load shaving conditions. The results reveal that appropriate coordination between steam extraction capacity and thermal storage scale plays a critical role in balancing peak-shaving capability and economic benefits across different operating scenarios. [Conclusion] By reasonably configuring the steam extraction rate and thermal storage duration

the proposed solar-coal complementary system can significantly enhance the operational flexibility and peak-shaving performance of coal-fired units without compromising economic viability. The established multi-objective optimization framework effectively captures the trade-offs among peak regulation capability

economic benefit

and investment cost. The findings of this study provide valuable theoretical support and practical guidance for the optimal design and engineering application of tower-type CSP-coal-fired hybrid power generation systems.