## 2 The TPUMSTSR Under RLV Model
### Consideration of the Operating Principles and Characteristics of TPUIMSTSR  
Thermal energy storage retrofitting has emerged as a promising solution to address the high coal consumption in thermal power units after RLV modifications. It stores excess heat generated by thermal power units and releases it during peak load periods, enhancing the units' PR capabilities. Furthermore, by optimizing unit operations through thermal energy storage systems, coal consumption and carbon emissions are reduced. Molten salt can operate stably at high temperatures across various thermal energy storage technologies. This feature makes it suitable for the high-temperature steam systems of thermal power units. Additionally, it offers high energy density and large storage capacity. Economically, molten salt materials are cost-effective, chemically stable, and have a long service life. Therefore, TPUIMSTSR provides significant advantages, with thermal efficiency exceeding 90%, and also provides the ability to complete charging and discharging processes within minutes, meeting the demands of rapid PR [35]. MSTS enables thermal power units to have a wider power generation range and has certain functions of typical energy storage systems; however, MSTS differs from energy storage systems. As a part of thermal power, MSTS stores high-temperature hot steam, and when it is necessary to increase the external power output of thermal power, the high-temperature hot steam is applied to thermal power. Therefore, MSTS only stores the thermal energy of the thermal power unit itself. The energy storage system, as an independent large-scale energy storage system, directly provides charging and discharging services, which means that its construction cost is not only relatively more expensive than the MSTS transformation within the thermal power plant, but the system also has lower efficiency. At the same time, there are restrictions on application scenarios and resources, which may conflict with the construction environment of the CS. The MSTS system consists of thermal storage tanks, heat exchangers, pumps, and pipeline systems. The thermal storage tank is used to store high-temperature molten salt. The heat exchanger transfers heat energy to the working fluid (such as water or steam). The pump and pipeline system ensure the circulation and transport of molten salt. In practice, the thermal storage tank is divided into high- and low-temperature dual-cycle storage tanks. The high-temperature storage tank is positioned between the boiler and the high-pressure cylinder of the steam turbine, while the low-temperature storage tank is placed between the steam turbine's working cylinder and the boiler. Heat charging occurs when the thermal power unit operates at low load or during surplus power generation periods. The high- and low-temperature storage tanks absorb excess thermal power from the boiler and the working cylinder of the steam turbine, respectively, and transfer it to the molten salt via heat exchangers, storing it within the tanks. A portion of the steam is diverted from the high-pressure turbine bypass or the low-pressure extraction port. The low-temperature thermal storage tank captures the underutilized waste heat in the low-temperature section (approximately 200-240 \({}^{\circ}\)C) of the turbine cylinder by integrating an auxiliary heat exchanger within the turbine casing. The bypassed steam reduces the flow into the low-pressure turbine, thereby decreasing power generation. Ultimately, this process maximizes the recovery and utilization of thermal energy throughout the entire system. This process reduces the minimum output of the thermal power unit. The heat discharging process takes place during peak load periods or when renewable energy output is insufficient.