Abstract: [Objectives] Due to the poor operational flexibility of combined heat and power (CHP) units under heat supply conditions, molten salt heat storage technology, as a commonly used medium- and high-temperature heat storage technology, can effectively enhance the peak-shaving performance of the units. Therefore, molten salt heat storage is coupled with CHP units to improve their operational flexibility, and research on thermal economic efficiency is conducted. [Methods] This study models a 300 MW subcritical CHP unit coupled with molten salt heat storage using Ebsilon software. Under the unit’s rated heat supply conditions, a heat storage and release scheme using two types of molten salt materials and two types of heat source steam is proposed. The effects of molten salt and steam-water parameters on the unit’s thermal economic efficiency and peak-shaving performance are investigated. [Results] During heat storage, a smaller additional solar salt flow rate and a feedwater return location closer to the feedwater pump resulted in better thermal economic efficiency, with the maximum power generation efficiency reaching 61.28%. During heat release, increases in solar salt flow rate and drain extraction flow rate of No. 2 high-pressure heater, as well as decreases in preheated condensate water flow can all improve the unit’s thermal economic efficiency, with the maximum power generation efficiency reaching 68.44%. During the heat storage and release processes, increasing the solar salt flow rate and the temperature of high-temperature Hitec salt can both enhance the unit’s thermal economic efficiency. When the solar salt flow rate and the temperature of high-temperature Hitec salt are 228 t/h and 345 ℃, respectively, the unit achieves optimal thermal economic efficiency, with the power generation efficiency reaching 65.88%. [Conclusions] The research findings can provide theoretical guidance for the analysis of peak-shaving performance and thermal economic efficiency of CHP units coupled with molten salt heat storage systems.

Key words: thermal power generation, combined heat and power units, molten salt thermal storage, thermoelectric decoupling, Ebsilon modeling, thermal economic efficiency, peak-shaving performance