Techno-economic and uncertainty analysis of a novel heat-power decoupling system used in a coal-fired combined heat and power unit under the electricity spot trading mode

With the large-scale development of renewable energy, coal-fired combined heat and power units face limited peak-regulation capability and reduced spot-market profitability due to inherent heat-power coupling characteristics. To enhance operational flexibility and economic performance, a molten salt-coupled steam accumulator system is proposed to enable full steam energy storage through coordinated utilization of sensible and latent heat. A steady-state thermodynamic model, an economic evaluation framework, and an uncertainty analysis model are developed to assess thermodynamic performance, economic feasibility, and robustness under spot-market operation. Results indicate that, under ideal insulation assumptions, complete storage of both the sensible and latent heat of steam can be achieved, with an ideal thermodynamic energy efficiency of 99.5%, significantly expanding the electrical load range in both heating and non-heating seasons. The integration of the molten salt-coupled steam accumulator system increases annual power-generation revenue by 1.18 million USD, reduces generation cost by 3.2 million USD, and provides an additional 0.56 million USD in capacity-related benefits. Financial evaluation yields a net present value of 11.7 million USD, an internal rate of return of 10.3%, and an equity internal rate of return of 26.5%, demonstrating economic feasibility. Sensitivity analysis identifies variable generation cost and equipment investment as dominant influencing factors, with net present value being most sensitive to the discount rate. The proposed molten salt-coupled steam accumulator framework, therefore, enhances the operational flexibility and spot-market profitability of coal-fired combined heat and power units and provides a generalizable approach for integrating full-energy thermal storage into combined heat and power plants.