A thermal power unit peak shaving and heat supply system based on hierarchical energy storage

Abstract

This invention belongs to the field of thermal power generation and energy storage technology, and provides a peak-shaving heating system for thermal power units based on graded energy storage. It includes a graded energy storage subsystem and a graded energy release heating subsystem. In the graded energy storage subsystem, the outlet of the cold salt tank is connected to the low-temperature inlet of the steam-salt heat exchanger and the molten salt electric heater; the low-temperature outlets of the steam-salt heat exchanger and the molten salt electric heater are connected to the inlet of the hot salt tank; the outlet of the demineralized water tank is connected to the low-temperature inlet of the steam-water heat exchanger and the hot water electric heater; the low-temperature outlets of the steam-water heat exchanger and the hot water electric heater are connected to the inlet of the hot water storage tank; and the high-temperature outlet of the steam-salt heat exchanger is connected to the high-temperature inlet of the steam-water heat exchanger. In the graded energy release heating subsystem, the outlet of the hot water storage tank is connected to the low-temperature inlet of the water-salt evaporator; the outlet of the hot salt tank is connected to the high-temperature inlet of the water-salt evaporator; and the high-temperature outlet of the water-salt evaporator is connected to the inlet of the cold salt tank. This solution improves energy storage capacity and peak-shaving flexibility, balancing molten salt usage with efficient peak-shaving energy storage.

Description

Technical Field

[0001] This invention relates to the fields of thermal power generation and energy storage technology, and in particular to a peak-shaving heating system for thermal power units based on graded energy storage. Background Technology

[0002] In the process of transforming into a new power system, the functional positioning of thermal power units has changed from the traditional main power generation source to a regulating power source that supports the safe and stable operation of the power grid, and needs to undertake key auxiliary services such as peak shaving, frequency regulation, spinning reserve and inertial support.

[0003] However, the peak-shaving capacity of existing thermal power units is typically only 20%-30%. During low-load operation, problems such as decreased main unit efficiency and increased plant power consumption arise, resulting in poor overall operational economy. Therefore, it is urgent to avoid prolonged low-load operation. The application of energy storage technology provides a solution to this problem. By storing surplus electrical or thermal energy during off-peak hours and releasing it during peak hours, thermal power units can be maintained within their high-efficiency load range.

[0004] Molten salt, due to its high energy density, good stability, and clean and environmentally friendly properties, has become the preferred medium for energy storage in thermal power units. Energy storage is typically achieved through molten salt electric heaters or steam heaters, releasing heat during peak periods for heating or power generation. However, molten salt has inherent technical drawbacks: its melting point and crystallization point are relatively high; even low-melting-point ternary molten salts still have a minimum operating temperature exceeding 190°C, limiting the usable temperature range and hindering the full recovery of the large amount of latent heat in steam. Furthermore, molten salt is expensive and faces safety and environmental pressures. Therefore, achieving efficient peak-shaving energy storage with less molten salt usage has become a pressing technical challenge in current practical applications.

[0005] In summary, existing molten salt energy storage systems for thermal power units suffer from technical problems such as limited temperature utilization, insufficient energy recovery, and high molten salt consumption. Summary of the Invention

[0006] This invention provides a peak-shaving heating system for thermal power units based on graded energy storage, which solves the defects of existing molten salt energy storage systems for thermal power units, such as limited temperature utilization, insufficient energy recovery, and large molten salt consumption.

[0007] This invention provides a peak-shaving heating system for thermal power units based on graded energy storage, the system comprising: a graded energy storage subsystem and a graded energy release heating subsystem; The graded energy storage subsystem includes: a steam-salt heat exchanger, a steam-water heat exchanger, a molten salt electric heater, a hot water electric heater, a demineralized water tank, a hot salt tank, a cold salt tank, and a hot water storage tank; The outlet of the cold salt tank is connected to the low-temperature inlet of the steam-salt heat exchanger and the molten salt electric heater; the low-temperature outlet of the steam-salt heat exchanger and the low-temperature outlet of the molten salt electric heater are connected to the inlet of the hot salt tank; the outlet of the demineralized water tank is connected to the low-temperature inlet of the steam-water heat exchanger and the hot water electric heater; the low-temperature outlet of the steam-water heat exchanger and the hot water electric heater is connected to the inlet of the hot water storage tank; and the high-temperature outlet of the steam-salt heat exchanger is connected to the high-temperature inlet of the steam-water heat exchanger. The graded energy release heating subsystem includes: a water-salt evaporator, a hot salt tank, a cold salt tank, and a hot water storage tank; The outlet of the hot water storage tank is connected to the low-temperature inlet of the water-salt evaporator, the outlet of the hot salt tank is connected to the high-temperature inlet of the water-salt evaporator, and the high-temperature outlet of the water-salt evaporator is connected to the inlet of the cold salt tank.

[0008] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the steam-salt heat exchanger is connected in parallel with the molten salt electric heater, and the steam-water heat exchanger is connected in parallel with the hot water electric heater.

[0009] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the inlet and outlet of the hot water electric heater are respectively provided with a first shut-off valve and a second shut-off valve, and the outlet of the demineralized water tank is equipped with a demineralized water pump. When using electrical energy for energy storage, the first shut-off valve, the second shut-off valve, and the demineralized water pump are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank flows through the low temperature side of the hot water electric heater for electric heating. After heating, it becomes high temperature saturated water and is stored in the hot water storage tank.

[0010] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the inlet and outlet of the steam-water heat exchanger on the low-temperature side are respectively provided with a third shut-off valve and a fourth shut-off valve. When using steam extraction from a steam turbine for energy storage, the third shut-off valve, the fourth shut-off valve, and the demineralized water pump are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank flows through the low-temperature side of the steam-water heat exchanger for steam heating. After heating, it becomes high-temperature saturated water and is stored in the hot water storage tank.

[0011] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the salt inlet and salt outlet of the molten salt electric heater are respectively provided with a fifth shut-off valve and a sixth shut-off valve, and the outlet of the cold salt tank is equipped with a cold salt pump. When using electrical energy for energy storage, the fifth shut-off valve, the sixth shut-off valve, and the cold salt pump are opened. The cold salt from the outlet of the cold salt tank flows through the low-temperature side of the molten salt electric heater for electric heating. After heating, it becomes hot salt and is stored in the hot salt tank.

[0012] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the salt inlet and salt outlet on the low-temperature side of the steam-salt heat exchanger are respectively provided with a seventh shut-off valve and an eighth shut-off valve. When using steam extraction from a steam turbine for energy storage, the seventh shut-off valve, the eighth shut-off valve, and the cold salt pump are opened. The cold salt from the outlet of the cold salt tank flows through the low-temperature side of the steam-salt heat exchanger for steam heating. After heating, it becomes hot salt and is stored in the hot salt tank.

[0013] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, a ninth shut-off valve is provided at the high-temperature side steam inlet of the steam-salt heat exchanger. When using steam extracted from a steam turbine for energy storage, the ninth shut-off valve is opened, and the steam extracted from the steam turbine flows sequentially through the high-temperature side of the steam-salt heat exchanger and the high-temperature side of the steam-water heat exchanger, becoming low-temperature saturated water and then sent to the unit's deaerator.

[0014] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the inlet and outlet of the hot water storage tank are respectively provided with a tenth shut-off valve and an eleventh shut-off valve. During the energy release heating process, the tenth and eleventh shut-off valves are opened, and the high-temperature saturated water from the outlet of the hot water storage tank flows through the low-temperature side of the water-salt evaporator to evaporate and superheat, and is finally sent to the steam pipeline network for external heating.

[0015] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, the hot water storage tank is equipped with a bypass valve. During the energy storage phase, when the liquid level in the hot water storage tank reaches the limit, the bypass valve is opened, and the high-temperature saturated water flows through the low-temperature side of the water-salt evaporator to evaporate and superheat, and is directly sent to the steam pipeline network for external heating.

[0016] According to the peak-shaving heating system for thermal power units based on graded energy storage provided by the present invention, a hot salt pump is installed at the outlet of the hot salt tank. During the energy release and heating process, the hot salt pump is turned on, and the hot salt from the outlet of the hot salt tank flows through the high-temperature side of the water-salt evaporator. After heat exchange, it becomes cold salt and is stored in the cold salt tank.

[0017] The present invention provides a staged energy storage-based peak-shaving heating system for thermal power units. Through the setup of a staged energy storage subsystem and a staged energy release heating subsystem, it utilizes a dual-mode adaptive design of molten salt and high-temperature saturated water staged energy storage, and electric energy storage and steam energy storage. This not only breaks through the temperature limitations of traditional molten salt energy storage, enabling full recovery and utilization of latent heat of steam, but also significantly reduces the amount of molten salt used. At the same time, it allows thermal power units to always operate in the high-efficiency load range, avoiding efficiency losses during low-load operation, significantly improving the unit's energy storage capacity and peak-shaving flexibility, and also ensures heating stability through staged energy release. It can balance molten salt usage and high-efficiency peak-shaving energy storage, helping the power grid to better absorb new energy sources. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a thermal power unit peak-shaving heating system based on graded energy storage provided in an embodiment of the present invention.

[0020] Figure label: 1 is a steam-salt heat exchanger, 2 is a steam-water heat exchanger, 3 is a molten salt electric heater, 4 is a hot water electric heater, 5 is a demineralized water tank, 6 is a water-salt evaporator, 10 is a hot salt pump, 11 is a cold salt pump, 12 is a demineralized water pump, 20 is the ninth shut-off valve, 21 is the eighth shut-off valve, 22 is the seventh shut-off valve, 23 is the sixth shut-off valve, 24 is the fifth shut-off valve, 25 is the fourth shut-off valve, 26 is the third shut-off valve, 27 is the second shut-off valve, 28 is the first shut-off valve, 29 is the tenth shut-off valve, 30 is the eleventh shut-off valve, 31 is a bypass valve, 40 is a hot salt tank, 41 is a cold salt tank, 42 ​​is a hot water storage tank, 101 is a staged energy storage subsystem, and 102 is a staged energy release heating system. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] The following is combined Figure 1 This invention describes the detailed scheme of a peak-shaving heating system for thermal power units based on graded energy storage, as provided in an embodiment of the present invention.

[0023] like Figure 1 As shown, the thermal power unit peak-shaving heating system based on graded energy storage provided in this embodiment of the invention specifically includes: a graded energy storage subsystem 101 and a graded energy release heating subsystem 102.

[0024] The graded energy storage subsystem 101 specifically includes: a steam-salt heat exchanger 1, a steam-water heat exchanger 2, a molten salt electric heater 3, a hot water electric heater 4, a demineralized water tank 5, a hot salt tank 40, a cold salt tank 41, and a hot water storage tank 42.

[0025] The outlet of the cold salt tank 41 is connected to the low-temperature inlet of the steam-salt heat exchanger 1 and the molten salt electric heater 3. The low-temperature outlet of the steam-salt heat exchanger 1 and the low-temperature outlet of the molten salt electric heater 3 are connected to the inlet of the hot salt tank 40. The outlet of the demineralized water tank 5 is connected to the low-temperature inlet of the steam-water heat exchanger 2 and the hot water electric heater 4. The low-temperature outlet of the steam-water heat exchanger 2 and the hot water electric heater 4 are connected to the inlet of the hot water storage tank 42. The high-temperature outlet of the steam-salt heat exchanger 1 is connected to the high-temperature inlet of the steam-water heat exchanger 2.

[0026] In this embodiment, the cold salt tank 41 and the hot water storage tank 42 serve as the initial storage carriers for molten salt and high-temperature saturated water, respectively. The cold salt and the room-temperature demineralized water are introduced into the corresponding heat exchange or heating equipment through pipelines, and after energy conversion, they are transported to the hot salt tank 40 and the hot water storage tank 42 for storage. The steam-salt heat exchanger 1 and the steam-water heat exchanger 2 are connected in series on the high-temperature side, realizing the cascade utilization of the steam extracted heat from the steam turbine, which can improve the energy recovery efficiency.

[0027] The graded energy release heating subsystem 102 specifically includes: a water-salt evaporator 6, a hot salt tank 40, a cold salt tank 41, and a hot water storage tank 42.

[0028] The outlet of the hot water storage tank 42 is connected to the low-temperature inlet of the water-salt evaporator 6, the outlet of the hot salt tank 40 is connected to the high-temperature inlet of the water-salt evaporator 6, and the high-temperature outlet of the water-salt evaporator 6 is connected to the inlet of the cold salt tank 41.

[0029] In this embodiment, a heat exchange link is formed in the energy release stage: hot salt - high-temperature saturated water - steam. The high-temperature molten salt output from the hot salt tank provides a heat source for the water-salt evaporator. The high-temperature saturated water output from the hot water storage tank is converted into qualified steam through evaporation and superheating. At the same time, the cold salt flows back to the cold salt tank to complete the cycle, which can ensure the continuity and stability of heating.

[0030] In the aforementioned graded energy release heating subsystem 102, the salt storage temperature of the hot salt tank 40 can be determined according to the requirements of the heating steam parameters. For example, if the required heating steam temperature is 380℃, and the heat exchange end difference of the water-salt evaporator 6 is considered to be 20℃, then the salt storage temperature of the hot salt tank 40 is 400℃. The temperature of the hot water storage tank 42 can be determined slightly lower than the saturated water temperature corresponding to the heating steam pressure. For example, if the heating steam pressure is 1.2MPa, the corresponding saturated water temperature is 187℃, and the heat storage temperature of the hot water storage tank 42 is considered to be 5℃ lower than the saturation temperature, which can be set to 182℃. The above parameters can be flexibly set according to the actual application scenario, and are not specifically limited here.

[0031] It should be noted that this embodiment can construct a closed-loop energy flow system through the coordinated design of the two core subsystems of energy storage and energy release. The tiered energy storage subsystem is responsible for capturing and storing surplus energy, while the tiered energy release heating subsystem is responsible for converting and releasing energy on demand. This can achieve precise matching between energy storage and utilization, and thus adapt to the dual needs of peak shaving and heating of thermal power units in practical applications.

[0032] In one embodiment, such as Figure 1 As shown, the steam-salt heat exchanger 1 is connected in parallel with the molten salt electric heater 3, and the steam-water heat exchanger 2 is connected in parallel with the hot water electric heater 4.

[0033] Understandably, the parallel connection of steam-salt heat exchanger 1 with molten salt electric heater 3 and the parallel connection of steam-water heat exchanger 2 with hot water electric heater 4 provides the system with dual options for electric energy storage and steam energy storage, allowing for flexible switching of modes based on grid load and unit operating status.

[0034] In one embodiment, such as Figure 1 As shown, the inlet and outlet of the hot water electric heater 4 are respectively equipped with a first shut-off valve 28 and a second shut-off valve 27, and the outlet of the demineralized water tank 5 is equipped with a demineralized water pump 12.

[0035] When using electrical energy for energy storage, the first shut-off valve 28, the second shut-off valve 27, and the demineralized water pump 12 are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank 5 flows through the low temperature side of the hot water electric heater 4 for electric heating. After heating, it becomes high temperature saturated water and is stored in the hot water storage tank 42.

[0036] In one embodiment, such as Figure 1 As shown, the inlet and outlet of the water exchanger 2 on the low-temperature side are respectively equipped with a third shut-off valve 26 and a fourth shut-off valve 25.

[0037] When using steam extraction from a steam turbine for energy storage, the third shut-off valve 26, the fourth shut-off valve 25, and the demineralized water pump 12 are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank 5 flows through the low temperature side of the steam-water heat exchanger 2 for steam heating. After heating, it becomes high temperature saturated water and is stored in the hot water storage tank 42.

[0038] Understandably, after the corresponding shut-off valve and demineralized water pump 12 are opened, the ambient temperature demineralized water enters the low temperature side of the steam-water heat exchanger 2, exchanges heat with the high temperature steam turbine extraction steam, absorbs the steam heat and converts it into high temperature saturated water for storage, efficiently recovers the sensible heat and latent heat of the steam, avoids energy waste, and maintains the operating stability of the steam turbine.

[0039] In this embodiment, by controlling the on / off state of four shut-off valves and driving the demineralized water pump 12, the ambient temperature demineralized water flows precisely through the hot water electric heater 4, efficiently converting surplus electrical energy into heat energy. After being heated into high-temperature saturated water, it is stored in the hot water storage tank 42, realizing the directional conversion and storage of electrical energy into heat energy, and absorbing the surplus power during off-peak hours of the power grid.

[0040] In one embodiment, such as Figure 1 As shown, the salt inlet and salt outlet of the molten salt electric heater 3 are respectively equipped with a fifth shut-off valve 24 and a sixth shut-off valve 23, and the outlet of the cold salt tank 41 is equipped with a cold salt pump 11.

[0041] When using electrical energy for energy storage, the fifth shut-off valve 24, the sixth shut-off valve 23, and the cold salt pump 11 are opened. The cold salt from the outlet of the cold salt tank 41 flows through the low-temperature side of the molten salt electric heater 3 for electric heating. After heating, it becomes hot salt and is stored in the hot salt tank 40.

[0042] In one embodiment, such as Figure 1 As shown, the salt inlet and salt outlet on the low-temperature side of the steam-salt heat exchanger 1 are respectively equipped with a seventh shut-off valve 22 and an eighth shut-off valve 21.

[0043] When using steam extraction from a steam turbine for energy storage, the seventh shut-off valve 22, the eighth shut-off valve 21, and the cold salt pump 11 are opened. The cold salt from the outlet of the cold salt tank 41 flows through the low-temperature side of the steam-salt heat exchanger 1 for steam heating. After heating, it becomes hot salt and is stored in the hot salt tank 40.

[0044] It is understandable that by using the cold salt pump 11 to deliver and control the shut-off valve, the cold salt flows through the low-temperature side of the steam-salt heat exchanger 1 to exchange heat with the steam extracted from the steam turbine, heating the cold salt into hot salt for storage, realizing the transfer of steam heat energy to molten salt. Combined with the stable storage characteristics of molten salt, the energy storage time is extended, and the peak-shaving response flexibility is improved.

[0045] In this embodiment, by means of the conveying action of the cold salt pump 11 and the path control of the four shut-off valves, the cold salt in the cold salt tank 41 flows through the molten salt electric heater 3, and the surplus electrical energy is used to heat the cold salt into hot salt and store it in the hot salt tank 40. This can give full play to the advantage of the high energy density of molten salt and achieve long-term and large-capacity storage of electrical energy.

[0046] In one embodiment, such as Figure 1 As shown, the high-temperature side steam inlet of the steam-salt heat exchanger 1 is equipped with a ninth shut-off valve 20.

[0047] When using steam extracted from a steam turbine for energy storage, the ninth shut-off valve 20 is opened, and the steam extracted from the steam turbine flows sequentially through the high-temperature side of the steam-salt heat exchanger 1 and the high-temperature side of the steam-water heat exchanger 2, becoming low-temperature saturated water and being sent to the unit's deaerator.

[0048] After the ninth shut-off valve 20 is opened, the steam extracted from the turbine passes through the high-temperature side of the steam-salt heat exchanger 1 and the steam-water heat exchanger 2 in sequence. After releasing heat in stages, it becomes low-temperature saturated water and is sent to the unit deaerator, thereby maximizing the recovery of steam energy and avoiding energy loss caused by direct steam discharge, thus improving the unit's thermal efficiency.

[0049] In one embodiment, such as Figure 1 As shown, the inlet and outlet of the hot water storage tank 42 are respectively equipped with a tenth shut-off valve 29 and an eleventh shut-off valve 30.

[0050] During the energy release heating process, the tenth shut-off valve 29 and the eleventh shut-off valve 30 are opened. The high-temperature saturated water from the outlet of the hot water storage tank 42 flows through the low-temperature side of the water-salt evaporator 6, where it evaporates and is superheated, and is finally sent to the steam pipeline network for external heating.

[0051] In this embodiment, the high-temperature saturated water output from the hot water storage tank 42 is precisely controlled by the tenth shut-off valve 29 and the eleventh shut-off valve 30. After being evaporated and superheated by the water-salt evaporator 6, it is converted into heating steam that meets the requirements and is directly sent into the steam pipeline network. This realizes the efficient conversion of stored thermal energy into heating energy and can ensure the heating demand during peak periods.

[0052] In one embodiment, such as Figure 1 As shown, the hot water storage tank 42 is equipped with a bypass valve 31.

[0053] During the energy storage phase, when the liquid level in the hot water storage tank 42 reaches the limit, the bypass valve 31 is opened, and the high-temperature saturated water flows through the low-temperature side of the water-salt evaporator 6 to evaporate and superheat, and is directly sent to the steam pipeline network for external heating.

[0054] Understandably, when the liquid level in the hot water storage tank 42 reaches the limit, the bypass valve 31 can be opened to directly introduce the excess high-temperature saturated water into the water-salt evaporator 6 to convert it into steam for heating, thus avoiding energy waste caused by the overflow of the storage tank. At the same time, it achieves seamless connection between energy storage and heating, improving the system's operational flexibility and energy utilization rate.

[0055] In one embodiment, such as Figure 1 As shown, a hot salt pump 10 is installed at the outlet of the hot salt tank 40.

[0056] When releasing energy for heating, the hot salt pump 10 is turned on, and the hot salt at the outlet of the hot salt tank 40 flows through the high-temperature side of the water-salt evaporator 6. After heat exchange, it becomes cold salt and is stored in the cold salt tank 41.

[0057] The hot salt pump 10 provides power for the flow of hot salt, allowing the high-temperature molten salt in the hot salt tank 40 to flow through the high-temperature side of the water-salt evaporator 6. After releasing heat, it becomes cold salt and flows back to the cold salt tank 41. This provides a stable heat source for the evaporation of high-temperature saturated water and completes the recycling of molten salt, thus ensuring the continuous and stable energy release process.

[0058] It is easy to see that the embodiments of the present invention use molten salt and high-temperature saturated water as heat storage media for graded energy storage, which can store electrical energy and steam energy. It can store the available energy in steam to the maximum extent, while keeping the thermal power unit operating in the high-efficiency load range, breaking through the temperature limit of molten salt energy storage, greatly reducing the amount of molten salt used, and improving the energy storage capacity and peak-shaving capacity of the thermal power unit.

[0059] Based on the above system structure, the workflow of the entire peak-shaving heating system for thermal power units based on graded energy storage is described below. It can be understood that the entire workflow of the peak-shaving heating system for thermal power units based on graded energy storage revolves around two core stages: energy storage and energy release for heating. Relying on the coordinated operation of the graded energy storage subsystem and the graded energy release heating subsystem, combined with dual thermal storage media and dual energy storage modes, it can achieve efficient energy storage and on-demand energy release. The specific workflow is as follows: In the electrical energy storage mode during the energy storage phase, for the molten salt side, the cold salt pump 11 at the outlet of the cold salt tank 41 is opened, as well as the fifth shut-off valve 24 at the inlet and the sixth shut-off valve 23 at the outlet of the molten salt electric heater 3. The cold salt in the cold salt tank flows into the low-temperature side of the molten salt electric heater 3 through the pipeline, and after being heated by electrical energy, it is converted into hot salt and then transported to the hot salt tank 40 for storage. For the water side, the demineralized water pump 12 at the outlet of the demineralized water tank 5 is opened, as well as the first shut-off valve 28 at the inlet and the second shut-off valve 27 at the outlet of the hot water electric heater 4. The room temperature demineralized water in the demineralized water tank flows into the low-temperature side of the hot water electric heater 4, and after being heated by electrical energy, it is converted into high-temperature saturated water and then sent to the hot water storage tank 42 for storage.

[0060] In the steam energy storage mode during the energy storage phase, for the molten salt side, the cold salt pump 11 is turned on, along with the seventh shut-off valve 22 at the low-temperature side inlet of the steam-salt heat exchanger 1 and the eighth shut-off valve 21 at the low-temperature side outlet. The cold salt flows through the low-temperature side of the steam-salt heat exchanger 1, exchanges heat with the high-temperature steam turbine extraction steam, and is heated into hot salt before being stored in the hot salt tank 40. For the water side, the demineralized water pump 12 is turned on, along with the third shut-off valve 26 at the low-temperature side inlet of the steam-water heat exchanger 2 and the fourth shut-off valve 25 at the low-temperature side outlet. The ambient temperature demineralized water flows into the low-temperature side of the steam-water heat exchanger 2, absorbs the heat from the steam turbine extraction steam, is converted into high-temperature saturated water, and is stored in the hot water storage tank 42.

[0061] In the steam flow process, the ninth shut-off valve 20 of the high-temperature side steam inlet of steam-salt heat exchanger 1 is opened. The steam extracted from the turbine first flows through the high-temperature side of steam-salt heat exchanger 1 to release heat, and then flows into the high-temperature side of steam-water heat exchanger 2 to continue to release heat. Finally, it becomes low-temperature saturated water and is sent to the unit deaerator for recycling.

[0062] In the bypass regulation stage, if the liquid level of the hot water storage tank 42 reaches the limit during the energy storage stage, the bypass valve 31 is opened, and the excess high-temperature saturated water flows directly into the low-temperature side of the water-salt evaporator 6. After evaporation and overheating, it is sent to the steam pipeline network for external heating, thus avoiding energy waste.

[0063] During the energy release and heating phase, on the hot salt side, the hot salt pump 10 at the outlet of the hot salt tank 40 can be opened. The high-temperature hot salt in the hot salt tank flows into the high-temperature side of the water-salt evaporator 6, releases heat, and becomes cold salt. It then flows back to the cold salt tank 41 through the pipeline, completing the molten salt cycle. On the water side, the tenth shut-off valve 29 at the inlet of the hot water storage tank 42 and the eleventh shut-off valve 30 at the outlet can be opened. The high-temperature saturated water in the hot water storage tank flows into the low-temperature side of the water-salt evaporator 6, absorbs the heat released by the hot salt, evaporates and superheats, and is converted into steam that meets the heating requirements. Finally, it is sent to the steam pipeline network for stable external heating.

[0064] In summary, the peak-shaving heating system for thermal power units based on graded energy storage provided in this embodiment of the invention has at least the following advantages compared with existing solutions: First, it has high energy utilization efficiency. It adopts staged energy storage of molten salt and high-temperature saturated water, which breaks through the temperature limit of traditional molten salt energy storage. The heat extracted by the steam turbine is transferred in stages through steam-salt heat exchanger and steam-water heat exchanger, which fully recovers the latent heat and sensible heat of the steam and avoids energy waste. In the energy release stage, dual-medium synergistic heat exchange is achieved through water-salt evaporator to ensure that the heat energy is efficiently converted into heating steam.

[0065] Secondly, it has strong operational flexibility. The steam-salt heat exchanger and molten salt electric heater, as well as the steam-water heat exchanger and hot water electric heater, are connected in parallel, supporting free switching between electric energy storage and steam energy storage modes. It can be dynamically adjusted according to the grid load and unit operating status. During the construction phase, a single energy storage mode can be selected as needed to adapt to different project investment levels and operational requirements.

[0066] Third, it balances peak-shaving capacity and operating costs, storing surplus electrical or thermal energy during off-peak hours to maintain thermal power units operating within their high-efficiency load range, avoiding efficiency decline and increased plant power consumption caused by low load; it also significantly reduces the amount of molten salt used, lowering molten salt procurement costs and safety and environmental pressures, thereby improving the overall operational reliability of the units.

[0067] Fourth, the system has better stability and adaptability. The hot water storage tank is equipped with a bypass valve, which can directly switch to the heating mode when the liquid level reaches the limit, realizing a seamless connection between energy storage and heating. Molten salt and high-temperature saturated water are recycled and reused. With precise shut-off valves and pump control, the continuous and stable energy storage and release process is ensured. At the same time, it helps the power grid to absorb new energy and strengthens the grid support capability.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A peak-shaving heating system for thermal power units based on graded energy storage, characterized in that, include: A tiered energy storage subsystem and a tiered energy release heating subsystem; The graded energy storage subsystem includes: a steam-salt heat exchanger, a steam-water heat exchanger, a molten salt electric heater, a hot water electric heater, a demineralized water tank, a hot salt tank, a cold salt tank, and a hot water storage tank; The outlet of the cold salt tank is connected to the low-temperature inlet of the steam-salt heat exchanger and the molten salt electric heater; the low-temperature outlet of the steam-salt heat exchanger and the low-temperature outlet of the molten salt electric heater are connected to the inlet of the hot salt tank; the outlet of the demineralized water tank is connected to the low-temperature inlet of the steam-water heat exchanger and the hot water electric heater; the low-temperature outlet of the steam-water heat exchanger and the hot water electric heater is connected to the inlet of the hot water storage tank; and the high-temperature outlet of the steam-salt heat exchanger is connected to the high-temperature inlet of the steam-water heat exchanger. The graded energy release heating subsystem includes: a water-salt evaporator, a hot salt tank, a cold salt tank, and a hot water storage tank; The outlet of the hot water storage tank is connected to the low-temperature inlet of the water-salt evaporator, the outlet of the hot salt tank is connected to the high-temperature inlet of the water-salt evaporator, and the high-temperature outlet of the water-salt evaporator is connected to the inlet of the cold salt tank.

2. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1, characterized in that, The steam-salt heat exchanger is connected in parallel with the molten salt electric heater, and the steam-water heat exchanger is connected in parallel with the hot water electric heater.

3. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1 or 2, characterized in that, The hot water electric heater is equipped with a first shut-off valve and a second shut-off valve at its inlet and outlet, respectively, and the demineralized water tank is equipped with a demineralized water pump at its outlet. When using electrical energy for energy storage, the first shut-off valve, the second shut-off valve, and the demineralized water pump are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank flows through the low temperature side of the hot water electric heater for electric heating. After heating, it becomes high temperature saturated water and is stored in the hot water storage tank.

4. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 3, characterized in that, The inlet and outlet of the low-temperature side of the steam-water heat exchanger are each equipped with a third shut-off valve and a fourth shut-off valve, respectively. When using steam extraction from a steam turbine for energy storage, the third shut-off valve, the fourth shut-off valve, and the demineralized water pump are opened. The ambient temperature demineralized water from the outlet of the demineralized water tank flows through the low-temperature side of the steam-water heat exchanger for steam heating. After heating, it becomes high-temperature saturated water and is stored in the hot water storage tank.

5. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1 or 2, characterized in that, The molten salt electric heater is equipped with a fifth shut-off valve and a sixth shut-off valve at its inlet and outlet, respectively, and a cold salt pump is installed at the outlet of the cold salt tank. When using electrical energy for energy storage, the fifth shut-off valve, the sixth shut-off valve, and the cold salt pump are opened. The cold salt from the outlet of the cold salt tank flows through the low-temperature side of the molten salt electric heater for electric heating. After heating, it becomes hot salt and is stored in the hot salt tank.

6. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 5, characterized in that, The salt inlet and salt outlet on the low-temperature side of the steam-salt heat exchanger are each equipped with a seventh shut-off valve and an eighth shut-off valve, respectively. When using steam extraction from a steam turbine for energy storage, the seventh shut-off valve, the eighth shut-off valve, and the cold salt pump are opened. The cold salt from the outlet of the cold salt tank flows through the low-temperature side of the steam-salt heat exchanger for steam heating. After heating, it becomes hot salt and is stored in the hot salt tank.

7. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1 or 2, characterized in that, The high-temperature side steam inlet of the steam-salt heat exchanger is equipped with a ninth shut-off valve. When using steam extracted from a steam turbine for energy storage, the ninth shut-off valve is opened, and the steam extracted from the steam turbine flows sequentially through the high-temperature side of the steam-salt heat exchanger and the high-temperature side of the steam-water heat exchanger, becoming low-temperature saturated water and then sent to the unit's deaerator.

8. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1, characterized in that, The inlet and outlet of the hot water storage tank are each equipped with a tenth shut-off valve and an eleventh shut-off valve, respectively. During the energy release heating process, the tenth and eleventh shut-off valves are opened, and the high-temperature saturated water from the outlet of the hot water storage tank flows through the low-temperature side of the water-salt evaporator to evaporate and superheat, and is finally sent to the steam pipeline network for external heating.

9. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1, characterized in that, The hot water storage tank is equipped with a bypass valve; During the energy storage phase, when the liquid level in the hot water storage tank reaches the limit, the bypass valve is opened, and the high-temperature saturated water flows through the low-temperature side of the water-salt evaporator to evaporate and superheat, and is directly sent to the steam pipeline network for external heating.

10. The peak-shaving heating system for thermal power units based on graded energy storage according to claim 1, characterized in that, A hot salt pump is installed at the outlet of the hot salt tank; During the energy release and heating process, the hot salt pump is turned on, and the hot salt from the outlet of the hot salt tank flows through the high-temperature side of the water-salt evaporator. After heat exchange, it becomes cold salt and is stored in the cold salt tank.

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