A carnot cell energy storage system

Abstract

This application provides a Carnot battery energy storage system, relating to the field of energy storage and power supply technology. The energy storage system includes: a heat pump thermal storage system consisting of a compressor, a first heat exchanger, a regenerator, a turbine, and a second heat exchanger connected in sequence; a low-temperature molten salt storage tank, the first heat exchanger, and a high-temperature molten salt storage tank connected in sequence; a steam generation system including a preheater, an evaporator, and a superheater connected in sequence; a reheater and superheater both connected to the high-temperature molten salt storage tank; a reheater and superheater both connected to the evaporator; and a connection between the low-temperature molten salt storage tank and the preheater; a steam turbine power generation system; and a waste steam heat recovery system. This application utilizes the existing steam turbine power generation system of a decommissioned unit, only adding a heat pump thermal storage system, a steam generation system, and a waste steam heat recovery system to replace the boiler, thereby achieving energy storage retrofitting, reducing costs, and minimizing resource waste.

Description

Technical Field

[0001] This application relates to the field of energy storage and power supply technology, and in particular to a Carnot battery energy storage system. Background Technology

[0002] Renewable energy sources (such as wind and solar power) are characterized by intermittency, volatility, and randomness. For example, during periods of low electricity load, surplus electricity from wind and solar power requires efficient storage technology to achieve inter-period regulation. Therefore, a stable and efficient energy storage system, such as the Carnot battery energy storage system, is needed.

[0003] In related technologies, the Carnot battery energy storage system requires the construction of a new compressed air storage tank, a molten salt storage tank, and supporting heat exchange equipment. It utilizes compressed air for energy storage and molten salt for heat storage. During the charging phase, surplus electrical energy is used to drive the compressor to compress air and heat the molten salt heat storage medium. During the discharging phase, the molten salt heat energy is converted into electrical energy through a steam generation system.

[0004] However, building new Carnot battery systems is costly, and a large number of retired units (such as retired thermal power units) have not been fully utilized, resulting in a waste of resources. Summary of the Invention

[0005] This application provides a Carnot battery energy storage system that makes full use of retired thermal power units and reduces resource waste.

[0006] To achieve the above objectives, the technical solution of this application is as follows:

[0007] On one hand, this application provides a Carnot battery energy storage system, comprising: a heat pump thermal storage system, the heat pump thermal storage system including a low-temperature molten salt tank, a high-temperature molten salt tank, and a compressor, a first heat exchanger, a regenerator, a turbine, and a second heat exchanger connected in sequence, the low-temperature molten salt tank, the first heat exchanger, and the high-temperature molten salt tank being connected in sequence; a steam generation system, the steam generation system including a reheater and a preheater, an evaporator, and a superheater connected in sequence, the reheater and superheater being connected to the outlet of the high-temperature molten salt tank, the reheater and superheater being connected to the evaporator, and the inlet of the low-temperature molten salt tank being connected to the preheater; a steam turbine power generation system, the reheater and preheater being connected to the steam turbine power generation system; and a waste steam heat recovery system, the steam turbine power generation system being connected to the waste steam heat recovery system, the waste steam heat recovery system being connected to the second heat exchanger.

[0008] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment has a first heat exchanger, a regenerator, and a second heat exchanger, each having a first inlet, a first outlet, a second inlet, and a second outlet. The compressor outlet is connected to the first inlet of the first heat exchanger, the first outlet of the first heat exchanger is connected to the first inlet of the regenerator, the first outlet of the regenerator is connected to the inlet of the compressor, the second outlet of the regenerator is connected to the inlet of the turbine, the outlet of the turbine is connected to the first inlet of the second heat exchanger, the first outlet of the second heat exchanger is connected to the second inlet of the regenerator, and both the second inlet and the second outlet of the second heat exchanger are connected to the waste heat recovery system.

[0009] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment includes a steam turbine power generation system comprising a high-pressure cylinder and a medium-pressure cylinder, a low-pressure cylinder, a condenser, a low-pressure heating group, a deaerator, and a high-pressure heating group connected in sequence. The reheater, preheater, evaporator, and superheater each have a second inlet and a second outlet, and the second inlet of the preheater is connected to the high-pressure heating group.

[0010] The working fluid flowing in from the second inlet of the preheater passes through the evaporator and the superheater in sequence. It then flows from the second outlet of the superheater into the inlet of the high-pressure cylinder. The second inlet of the reheater is connected to the outlet of the high-pressure cylinder, and the second outlet of the reheater is connected to the inlet of the intermediate-pressure cylinder.

[0011] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment includes a high-voltage heating group comprising a first high-voltage heater, a second high-voltage heater and a third high-voltage heater connected in sequence. Both the high-voltage cylinder and the intermediate-pressure cylinder have at least two air extraction ports. The two air extraction ports of the high-voltage cylinder are respectively connected to the first high-voltage heater and the second high-voltage heater. One air extraction port of the intermediate-pressure cylinder is connected to the third high-voltage heater, and the other air extraction port of the intermediate-pressure cylinder is connected to the deaerator.

[0012] The working fluid flowing out of the deaerator flows sequentially through the first high-pressure heater, the second high-pressure heater, and the third high-pressure heater into the second inlet of the preheater.

[0013] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment includes a low-pressure heating group comprising at least two low-pressure heaters connected in sequence, a low-pressure cylinder having at least two low-pressure exhaust ports, the two low-pressure exhaust ports being connected one-to-one with the second inlets of the two low-pressure heaters, the first inlet of one low-pressure heater being connected to the first outlet of the condenser, and the first outlet of the other low-pressure heater being connected to the deaerator.

[0014] The working fluid flowing out of the first outlet of the condenser flows sequentially through the low-pressure heater, deaerator and high-pressure heating group into the second inlet of the preheater.

[0015] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment includes a waste heat recovery system comprising a circulating pump, a cold water storage tank, a third heat exchanger, and a hot water storage tank connected in sequence. The hot-side inlet of the third heat exchanger is connected to a low-pressure cylinder, the hot-side outlet of the third heat exchanger is connected to a condenser, the cold-side inlet of the third heat exchanger is connected to the outlet of the cold water storage tank, the cold-side outlet of the third heat exchanger is connected to the inlet of the hot water storage tank, the inlet of the cold water storage tank is connected to the second outlet of the second heat exchanger, and the outlet of the hot water storage tank is connected to the second inlet of the second heat exchanger.

[0016] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment, including a waste heat recovery system, further includes a first valve, a second valve, a third valve, and a fourth valve. The third heat exchanger is connected to a cold water storage tank via the second valve, and the cold-side outlet of the third heat exchanger is connected to a hot water storage tank via the fourth valve. The inlet of the cold water storage tank is connected to the second heat exchanger via the first valve, and the outlet of the hot water storage tank is connected to the second heat exchanger via the third valve. The first and fourth valves are both open during charging, and the second and third valves are both open during discharging.

[0017] In one possible implementation, the Carnot battery energy storage system and waste heat recovery system provided in this application embodiment further include a fifth valve. The third heat exchanger is connected to the low-pressure cylinder through the fifth valve. The fifth valve is used to open during discharge to regulate the flow rate from the exhaust port of the low-pressure cylinder into the third heat exchanger.

[0018] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment further includes a first drive unit having a first shaft, with a compressor and a turbine both connected to the first shaft. The first drive unit is configured to drive the compressor to compress gas during peak power load periods.

[0019] In one possible implementation, the Carnot battery energy storage system provided in this application embodiment further includes a second drive member, the second drive member having a second shaft, and the high-pressure cylinder, the medium-pressure cylinder and the low-pressure cylinder are all connected to the second shaft.

[0020] This application provides a Carnot battery energy storage system, which includes: a heat pump thermal storage system; a steam generation system; a steam turbine power generation system; and a waste heat recovery system. During the charging phase, the heat pump thermal storage system of this application converts surplus electricity during off-peak hours into molten salt thermal energy and stores it. Simultaneously, the heat stored in the waste heat recovery system is used as a low-temperature heat source, effectively improving the coefficient of performance (COP) of the heat pump. During the discharging phase, the stored molten salt thermal energy is converted into electrical energy through the steam generation system and the steam turbine power generation system. Simultaneously, the waste heat from the steam turbine power generation system is collected by the waste heat recovery system and supplied for use during the charging phase. The recovery of waste heat reduces the cold-end loss of the steam turbine power generation system and improves round-trip efficiency. This application transforms decommissioned coal-fired power plant units into energy storage power plants. Utilizing the original steam turbine power generation system of the decommissioned unit, only the heat pump thermal storage system, steam generation system, and waste heat recovery system need to be added to replace the boiler, thereby achieving energy storage transformation. This avoids the duplication of high-cost equipment such as compressed air storage tanks and molten salt storage tanks, reducing costs and minimizing resource waste. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0022] Figure 1 This is a schematic diagram of the structure of the Carnot battery energy storage system provided in an embodiment of this application.

[0023] Explanation of reference numerals in the attached figures:

[0024] 100-Heat pump thermal storage system; 110-Low-temperature molten salt storage tank; 120-High-temperature molten salt storage tank; 130-Compressor; 140-First heat exchanger; 150-Regenerator; 160-Turbine; 170-Second heat exchanger; 180-Molten salt pump; 200-Steam generation system; 210-Reheater; 220-Preheater; 230-Evaporator; 240-Superheater; 300-Steam turbine power generation system; 310-High-pressure cylinder; 320-Intermediate-pressure cylinder; 330-Low-pressure cylinder; 340-Condenser; 350-Low-pressure heating group; 35 1-Low-pressure heater; 360-Deaerator; 370-High-pressure heating group; 371-First high-pressure heater; 372-Second high-pressure heater; 373-Third high-pressure heater; 380-Feed water pump; 390-Condensate pump; 400-Waste heat recovery system; 410-Cold water storage tank; 420-Third heat exchanger; 430-Hot water storage tank; 500-First drive unit; 600-Second drive unit; 440-First valve; 450-Second valve; 460-Third valve; 470-Fourth valve; 480-Fifth valve.

[0025] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0026] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended application.

[0027] It should be noted that in the description of the embodiments of this application, the terms "upper", "lower", "inner", "outer" and other terms indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description, and are not intended to indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this application.

[0028] Furthermore, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0029] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] The steam Rankine cycle is an ideal cycle process that uses steam as the working fluid. It mainly includes isentropic compression, isobaric heating, isentropic expansion, and an isobaric condensation process, and is used for the power cycle of steam plants.

[0031] In related technologies, the Carnot battery energy storage system requires the construction of a new compressed air storage tank, a molten salt storage tank, and supporting heat exchange equipment. It utilizes compressed air for energy storage and molten salt for heat storage. During the charging phase, surplus electrical energy is used to drive the compressor to compress air and heat the molten salt heat storage medium. During the discharging phase, the molten salt heat energy is converted into electrical energy through a steam generation system.

[0032] However, building new Carnot battery systems is costly, and a large number of decommissioned thermal power units’ equipment (such as steam turbines, boilers, and plant land) are not being fully utilized, resulting in a waste of resources.

[0033] In view of this, this application provides a Carnot battery energy storage system, which includes: a heat pump thermal storage system; a steam generation system; a steam turbine power generation system; and a waste heat recovery system. During the charging phase, the heat pump thermal storage system of this application converts surplus electricity during off-peak hours into molten salt thermal energy and stores it, while simultaneously using the heat stored in the waste heat recovery system as a low-temperature heat source, effectively improving the coefficient of performance (COP) of the heat pump. During the discharging phase, the stored molten salt thermal energy is converted into electrical energy through the steam generation system and the steam turbine power generation system, while the waste heat from the steam turbine power generation system is collected by the waste heat recovery system and supplied for use during the charging phase. The recovery of waste heat reduces the cold-end loss of the steam turbine power generation system and improves round-trip efficiency. This application transforms decommissioned coal-fired power plant units into energy storage power plants, utilizing the original steam turbine power generation system of the decommissioned units. Only a heat pump thermal storage system, a steam generation system, and a waste heat recovery system are needed to replace the boiler, thereby achieving energy storage transformation. This avoids the duplication of high-cost equipment such as compressed air storage tanks and molten salt storage tanks, reducing costs and minimizing resource waste.

[0034] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] This application provides a Carnot battery energy storage system, such as Figure 1As shown, it includes: a heat pump thermal storage system 100, which includes a low-temperature molten salt storage tank 110, a high-temperature molten salt storage tank 120, and a compressor 130, a first heat exchanger 140, a regenerator 150, a turbine 160, and a second heat exchanger 170 connected in sequence; a steam generation system 200, which includes a reheater 210 and a preheater 220, an evaporator 230, and a superheater 240 connected in sequence. All superheaters 240 are connected to the outlet of the high-temperature molten salt storage tank 120. The first outlet of the reheater 210 and the first outlet of the superheater 240 are both connected to the first inlet of the evaporator 230. The inlet of the low-temperature molten salt storage tank 110 is connected to the first outlet of the preheater 220. The steam turbine power generation system 300 is connected to both the reheater 210 and the preheater 220. The waste steam heat recovery system 400 is connected to both the steam turbine power generation system and the waste steam heat recovery system 400. The waste steam heat recovery system 400 is connected to the second heat exchanger 170.

[0036] This energy storage system converts electrical energy into thermal energy stored in high-temperature molten salt through a heat pump cycle, and converts the thermal energy back into electrical energy through a steam Rankine cycle. At the same time, it utilizes the waste heat recovery system 400 to recover and reuse cold-end waste heat, thus forming a complete and efficient Carnot battery energy storage cycle.

[0037] In this embodiment of the heat pump heat storage system 100, the compressor 130 compresses gas and heats the low-temperature molten salt in the first heat exchanger 140 to form high-temperature molten salt, which is then stored in the high-temperature molten salt storage tank 120.

[0038] In this heat pump heat storage cycle, the complete flow path of the working fluid is as follows: it flows out from the outlet of the compressor 130, enters the first inlet of the first heat exchanger 140, releases heat, and flows out from its first outlet; then it enters the first inlet of the regenerator 150, cools, and flows out from its first outlet; then it enters the inlet of the turbine 160, expands, does work, and flows out from its outlet; then it enters the first inlet of the second heat exchanger 170, absorbs heat, and flows out from its first outlet; then it returns to the second inlet of the regenerator 150, is preheated, and flows out from its second outlet; finally, it returns to the inlet of the compressor 130, completing the heat pump cycle.

[0039] The regenerator 150 improves heat pump performance by lowering the outlet temperature of the working fluid at the first heat exchanger 140 and heating the outlet temperature of the second heat exchanger 170. The regenerator 150 achieves heat recovery within the system by lowering the temperature of the working fluid entering the turbine 160 to recover more work, and by preheating the working fluid entering the compressor 130 to reduce compression power consumption, thereby significantly improving the overall coefficient of performance (COP) of the heat pump cycle.

[0040] In the steam generation system 200, the molten salt in the high-temperature molten salt storage tank 120 heats the feedwater through the superheater 240 and the reheater 210 to generate high-temperature and high-pressure steam; the molten salt in the low-temperature molten salt storage tank 110 participates in the steam generation process through the preheater 220, and is stored in the low-temperature molten salt storage tank 110 after releasing heat.

[0041] The steam generation system 200 replaces the function of the original power plant boiler. Utilizing the sensible heat storage characteristics of molten salt, it efficiently transfers the stored heat energy to water / steam through the cascade heat exchange of the superheater 240, reheater 210, evaporator 230 and preheater 220, thereby driving the operation of the steam turbine.

[0042] During the charging phase, the heat pump thermal storage system 100 of this embodiment converts surplus electricity during off-peak hours into molten salt thermal energy and stores it. Simultaneously, it uses the heat stored in the waste steam recovery system 400 as a low-temperature heat source, effectively improving the coefficient of performance (COP) of the heat pump. During the discharging phase, the stored molten salt thermal energy is converted into electrical energy via the steam generation system 200 and the turbine power generation system 300. Meanwhile, the waste steam heat from the turbine power generation system 300 is collected by the waste steam recovery system 400 and supplied for use during the charging phase. The recovery of waste steam reduces the cold-end loss of the turbine power generation system 300 and improves the round-trip efficiency. This application transforms decommissioned coal-fired power plant units into energy storage power plants. Utilizing the existing turbine power generation system 300 of the decommissioned unit, only the heat pump thermal storage system 100, the steam generation system 200, and the waste steam recovery system 400 need to be added to replace the boiler, thereby achieving energy storage transformation. This avoids the duplication of high-cost equipment such as compressed air storage tanks and molten salt storage tanks, reducing costs and minimizing resource waste.

[0043] It should be noted that during the discharge phase, part of the waste heat from the turbine power generation system 300 is collected by the waste heat recovery system 400 and stored in the hot water storage tank 430; during the charging phase, the heat stored in the hot water storage tank 430 by the waste heat recovery system 400 during the discharge phase is used as a low-temperature heat source.

[0044] The embodiments of this application make maximum use of the core equipment of the decommissioned units, such as steam turbine generator sets and auxiliary systems, realizing the transformation from traditional thermal power to large-scale physical energy storage, which is low-cost, highly efficient, and makes full use of resources.

[0045] Among them, such as Figure 1As shown, the first heat exchanger 140, the regenerator 150, and the second heat exchanger 170 each have a first inlet, a first outlet, a second inlet, and a second outlet. The outlet of the compressor 130 is connected to the first inlet of the first heat exchanger 140, the first outlet of the first heat exchanger 140 is connected to the first inlet of the regenerator 150, the second outlet of the regenerator 150 is connected to the inlet of the compressor 130, the second outlet of the regenerator 150 is connected to the inlet of the turbine 160, the outlet of the turbine 160 is connected to the first inlet of the second heat exchanger 170, and the first outlet of the second heat exchanger 170 is connected to the second inlet of the regenerator 150. Both the second inlet and the second outlet of the second heat exchanger 170 are connected to the waste heat recovery system 400.

[0046] Compressor 130 is used to compress the working fluid, increasing its pressure and temperature. The outlet of compressor 130 is connected to the first inlet of first heat exchanger 140, the first outlet of first heat exchanger 140 is connected to the first inlet of regenerator 150, and the second outlet of regenerator 150 is connected to the inlet of compressor 130. The second outlet of regenerator 150 is connected to the inlet of turbine 160, the outlet of turbine 160 is connected to the first inlet of second heat exchanger 170, the first outlet of second heat exchanger 170 is connected to the second inlet of regenerator 150, the second inlet of second heat exchanger 170 is connected to the outlet of hot water storage tank 430, and the second outlet of second heat exchanger 170 is connected to the inlet of cold water storage tank 410.

[0047] The second outlet of the first heat exchanger 140 is connected to the inlet of the high-temperature molten salt storage tank 120, and the second inlet of the first heat exchanger 140 is connected to the outlet of the low-temperature molten salt storage tank 110. The outlet of the low-temperature molten salt storage tank 110 is connected to the inlet of the high-temperature molten salt storage tank 120 via a molten salt pump 180 and the second inlet (cold fluid side) of the first heat exchanger 140. The molten salt pump 180 provides the power required for the flow of molten salt. The regenerator 150 reduces the temperature of the working fluid at the outlet of the first heat exchanger 140 while heating the working fluid at the outlet of the first heat exchanger 170, thereby increasing the inlet temperature of the compressor 130.

[0048] It should be noted that in this embodiment, the working fluid flows in a closed loop formed by the compressor 130, the first heat exchanger 140, the regenerator 150, the turbine 160, and the second heat exchanger 170, completing the processes of compression, heat release, heat recovery, expansion, and heat absorption. The molten salt is heated by the working fluid as a cold source in the first heat exchanger 140, completing heat storage. The working fluid flowing out of the compressor 130 sequentially passes through the first inlet of the first heat exchanger 140, the regenerator 150, the turbine 160, the first inlet of the second heat exchanger 170, the second inlet of the regenerator 150, and the inlet of the compressor 130, returning to the compressor 130. The working fluid flowing out of the low-temperature molten salt storage tank 110 flows through the first heat exchanger 140 into the high-temperature molten salt storage tank 120.

[0049] In one possible implementation, such as Figure 1 As shown in the embodiment of this application, the Carnot battery energy storage system and the turbine power generation system 300 include a high-pressure cylinder 310 and a medium-pressure cylinder 320, a low-pressure cylinder 330, a condenser 340, a low-pressure heating group 350, a deaerator 360, and a high-pressure heating group 370 connected in sequence. The superheater 240, the high-pressure cylinder 310, and the reheater 210 are connected in sequence. The reheater 210, the preheater 220, the evaporator 230, and the superheater 240 all have a second inlet and a second outlet. The second inlet of the preheater 220 is connected to the high-pressure heating group 370. The working fluid flowing in from the second inlet of the preheater 220 passes through the evaporator 230 and the superheater 240 in sequence, and flows into the inlet of the high-pressure cylinder 310 from the second outlet of the superheater 240. The second inlet of the reheater 210 is connected to the outlet of the high-pressure cylinder 310, and the second outlet of the reheater 210 is connected to the inlet of the medium-pressure cylinder 320.

[0050] During power generation, the flow path of the water / steam working fluid is as follows: feedwater flowing out from the outlet of the high-pressure heating group 370 enters the second inlet of the preheater 220 and flows out from its second outlet; then it enters the second inlet of the evaporator 230 and flows out from its second outlet; then it enters the second inlet of the superheater 240, is heated into superheated steam, flows out from its second outlet, and enters the inlet of the high-pressure cylinder 310; after the high-pressure cylinder 310 performs work, the steam is discharged from its outlet and enters the second inlet of the reheater 210, is reheated, flows out from the second outlet of the reheater 210, and enters the inlet of the intermediate-pressure cylinder 320; after successively performing work in the intermediate-pressure cylinder 320 and the low-pressure cylinder 330, the exhaust steam is discharged into the condenser 340 for condensation; the condensate flows out from the outlet of the condenser 340, passes through the low-pressure heating group 350, the deaerator 360, and the high-pressure heating group 370 in sequence, and returns to the second inlet of the preheater 220, completing the power generation cycle.

[0051] The inlet of the high-pressure cylinder 310 is connected to the second outlet of the superheater 240, the outlet of the high-pressure cylinder 310 is connected to the second inlet of the reheater 210, the second outlet of the reheater 210 is connected to the inlet of the intermediate-pressure cylinder 320, and the outlet of the high-pressure heating group 370 is connected to the second inlet of the preheater 220.

[0052] The reheater 210 and superheater 240 are arranged in parallel. The molten salt from the outlet of reheater 210 and the molten salt from the outlet of superheater 240 are mixed and then sequentially enter evaporator 230 and preheater 220 to heat the feedwater. The low-temperature molten salt after heat release is finally stored in a low-temperature molten salt tank. It should be noted that the molten salt circulation in this application realizes the cascade utilization of energy. The highest temperature molten salt is first used for the high-requirement superheating and reheating processes. Subsequently, the molten salt with lower temperature is combined and continues to be used in the evaporation and preheating processes, thereby maximizing the utilization of molten salt heat and improving the system thermal efficiency. The working fluid flowing in from the second inlet of preheater 220 flows through evaporator 230 into superheater 240 and flows out from the second outlet of superheater 240 to high-pressure cylinder 310.

[0053] Understandably, during the discharge phase, the high-temperature molten salt flows out of the high-temperature molten salt storage tank 120 and splits into two paths: one enters the hot side of the superheater 240, and the other enters the hot side of the reheater 210. After the molten salt flowing out from the hot side of the superheater 240 and the reheater 210 mix, it flows sequentially through the hot side of the evaporator 230 and the hot side of the preheater 220. The low-temperature molten salt, after releasing heat, finally returns to the low-temperature molten salt storage tank 110, thus forming a molten salt loop.

[0054] During power generation, feedwater flows out from the high-pressure heating unit 370, enters the cold side of the preheater 220 where it is heated, then enters the cold side of the evaporator 230 where it is evaporated into saturated steam, and finally enters the cold side of the superheater 240 where it is heated into superheated steam. After the superheated steam enters the high-pressure cylinder 310 to do work, the exhaust steam returns to the cold side of the reheater 210 for reheating. The reheated steam then enters the intermediate-pressure cylinder 320 and the low-pressure cylinder 330 to continue doing work, thus forming a water or steam circuit.

[0055] Understandably, the feedwater is gradually heated into superheated steam in the preheater 220, evaporator 230, and superheater 240. After driving the high-pressure cylinder 310 to do work, it returns to the reheater 210 for reheating, and then enters the medium and low-pressure cylinders 330 to continue expanding and doing work. Finally, the exhaust steam is condensed and returned through the feedwater reheat system, forming a complete power generation cycle.

[0056] This application embodiment also includes a condensate pump 390, which is disposed between the condenser 340 and the low-pressure heater 351. The condensate pump 390 is used to drive the working fluid discharged from the condenser 340 into the low-pressure heater 351, and the working fluid (such as steam) flowing out of the low-pressure heater 351 can also return to the condenser 340.

[0057] In other embodiments, such as Figure 1As shown, the high-pressure heating group 370 includes a first high-pressure heater 371, a second high-pressure heater 372, and a third high-pressure heater 373 connected in sequence. Both the high-pressure cylinder 310 and the intermediate-pressure cylinder 320 have at least two exhaust ports. The two exhaust ports of the high-pressure cylinder 310 are respectively connected to the first high-pressure heater 371 and the second high-pressure heater 372. One exhaust port of the intermediate-pressure cylinder 320 is connected to the third high-pressure heater 373, and the other exhaust port of the intermediate-pressure cylinder 320 is connected to the deaerator 360. The working fluid flowing out of the deaerator 360 flows into the second inlet of the preheater 220 through the first high-pressure heater 371, the second high-pressure heater 372, and the third high-pressure heater 373 in sequence.

[0058] The high-pressure heating group 370 forms a multi-stage steam extraction and regeneration system, thereby ensuring cycle efficiency. The high-pressure heating group 370 uses the steam that has done some work in the high-pressure cylinder 310 and the intermediate-pressure cylinder 320 to preheat the feedwater, reducing the heat absorbed in the molten salt circuit and reducing the cold source loss of the condenser 340.

[0059] In some other embodiments, the low-pressure heating group 350 includes at least two low-pressure heaters 351 connected in sequence, the low-pressure cylinder 330 has at least two low-pressure exhaust ports, the two low-pressure exhaust ports are connected one-to-one with the second inlets of the two low-pressure heaters 351, the first inlet of one low-pressure heater 351 is connected to the first outlet of the condenser 340, the first outlet of the other low-pressure heater 351 is connected to the deaerator 360, and the working fluid flowing out from the first outlet of the condenser 341 flows into the second inlet of the preheater 220 in sequence through the low-pressure heater 351, the deaerator 360 and the high-pressure heating group 370.

[0060] like Figure 1 As shown, there are four low-pressure heaters 351, which are connected in sequence.

[0061] The steam turbine power generation system also includes a feedwater pump 380, which is located between the deaerator 360 and the high-pressure heating group 370 and is used to drive the flow of the working fluid (such as feedwater).

[0062] The low-pressure heating group 350 and the high-pressure heating group 370 together form a feedwater regeneration system, which provides preliminary heating to the condensate and further recovers the energy extracted from the low-pressure cylinder 330.

[0063] This application proposes to convert decommissioned coal-fired power plant units into energy storage power plants, retaining the original steam turbine power generation system 300 and modifying it for energy storage, replacing the boiler with a steam generation system 200.

[0064] In some embodiments, such as Figure 1As shown, the waste heat recovery system 400 includes a circulating pump, a cold water storage tank 410, a third heat exchanger 420, and a hot water storage tank 430 connected in sequence. The hot side inlet of the third heat exchanger 420 is connected to the low-pressure cylinder 330, the hot side outlet of the third heat exchanger 420 is connected to the condenser 340, the cold side inlet of the third heat exchanger 420 is connected to the outlet of the cold water storage tank 410, the cold side outlet of the third heat exchanger 420 is connected to the inlet of the hot water storage tank 430, the inlet of the cold water storage tank 410 is connected to the second outlet of the second heat exchanger 170, and the outlet of the hot water storage tank 430 is connected to the second inlet of the second heat exchanger 170.

[0065] During the discharge phase, the pressurized water stored in the waste heat recovery system 400 serves as the working medium for waste heat recovery. Its flow path is as follows: it flows out from the outlet of the cold water storage tank 410, is pressurized by the circulating pump, and then enters the cold-side inlet of the third heat exchanger 420 through the second valve 450. After absorbing heat from the waste steam, it flows out from the cold-side outlet of the third heat exchanger 420 and enters the inlet of the hot water storage tank 430 through the fourth valve 470 for storage. During the charging phase, its path is as follows: it flows out from the outlet of the hot water storage tank 430, enters the second inlet of the second heat exchanger 170 through the third valve 460, releases heat and cools, then flows out from the second outlet of the second heat exchanger 170 and enters the inlet of the cold water storage tank 410 through the first valve 440.

[0066] The circulating pump is connected to the second outlet of the second heat exchanger 170 to provide the pressure differential required for the circulation of the heat storage pressurized water; the hot side inlet of the third heat exchanger 420 is connected to the low-pressure cylinder 330 through the fifth valve 480, the hot side outlet of the third heat exchanger 420 is connected to the condenser 340, the cold side inlet of the third heat exchanger 420 is connected to the cold water storage tank 410 through the second valve 450, and the cold side outlet of the third heat exchanger 420 is connected to the hot water storage tank 430 through the fourth valve 470.

[0067] The waste heat recovery system 400 transfers and stores the low-temperature waste heat from the turbine exhaust steam during the discharge phase in a hot water storage tank 430 via a third heat exchanger 420. During the charging phase, this stored heat is used to raise the temperature on the low-temperature side of the heat pump, thereby directly improving the performance of the heat pump and realizing the recovery and utilization of waste heat.

[0068] In some embodiments, such as Figure 1As shown, this embodiment of the application also includes a first valve 440, a second valve 450, a third valve 460, and a fourth valve 470. The third heat exchanger 420 is connected to the cold water storage tank 410 through the second valve 450. The cold side outlet of the third heat exchanger 420 is connected to the hot water storage tank 430 through the fourth valve 470. The inlet of the cold water storage tank 410 is connected to the second heat exchanger 170 through the first valve 440, and the outlet of the hot water storage tank 430 is connected to the second heat exchanger 170 through the third valve 460. The first valve 440 and the fourth valve 470 are both open during charging, and the second valve 450 and the third valve 460 are both open during discharging.

[0069] This application controls the flow direction and flow rate of the thermal storage pressurized water through two sets of valves working together. The first valve 440 and the fourth valve 470 are open during the charging process and closed during the discharging process, while the second valve 450 and the third valve 460 are closed during the charging process and open during the discharging process.

[0070] During discharge, the water circuit connects the third heat exchanger 420 to the water storage tank to collect waste heat; during charging, the water circuit connects the second heat exchanger 170 to the water storage tank to release heat, ensuring that the two modes do not interfere with each other and that the operation is stable and reliable.

[0071] In other embodiments, such as Figure 1 As shown, it also includes a fifth valve 480. The third heat exchanger 420 is connected to the low-pressure cylinder 330 through the fifth valve 480. The fifth valve 480 is located between the exhaust port of the third heat exchanger 420 and the exhaust port of the low-pressure cylinder 330. The fifth valve 480 is used to open during discharge to regulate the flow rate entering the third heat exchanger 420 from the exhaust port.

[0072] The fifth valve 480 regulates the steam flow rate of part of the low-pressure cylinder 330 to enter the third heat exchanger 420 for condensation, recovering the waste heat of the exhaust steam and storing it in the water tank.

[0073] The fifth valve 480 allows the amount of waste heat recovery to be controlled according to demand (such as the amount of heat source required by the heat pump or the power grid load), so as to achieve stable operation of the system.

[0074] In another possible implementation, such as Figure 1 As shown, the Carnot battery energy storage system provided in this application embodiment also includes a first drive unit 500. The first drive unit 500 has a first shaft, and the compressor 130 and the turbine 160 are both connected to the first shaft. The first drive unit 500 is configured to drive the compressor 130 to compress gas during peak power load, thereby converting electrical energy into circulating gas heat energy and exchanging heat with low-temperature molten salt from the molten salt pump 180 through the first heat exchanger 140.

[0075] The first drive unit 500 is an electric motor. The compressor 130 and the turbine 160 are coaxially connected to the first drive unit 500 (electric motor), resulting in a compact layout. The expansion work recovered by the turbine 160 is directly used to assist in driving the compressor 130, reducing the net input work of the electric motor and improving the energy storage efficiency of the heat pump.

[0076] The Carnot battery energy storage system provided in this application embodiment, such as Figure 1 As shown, it also includes a second drive unit 600, which has a second shaft, and the high-pressure cylinder 310, the medium-pressure cylinder 320 and the low-pressure cylinder 330 are all connected to the second shaft.

[0077] The second drive unit 600 is an electric motor. The high-pressure cylinder 310, the intermediate-pressure cylinder 320, and the low-pressure cylinder 330 are coaxially connected to the second drive unit 600 (generator), which has a compact layout and makes reasonable use of the drive.

[0078] The waste heat recovery system 400 includes a first valve 440, a cold water storage tank 410, a second valve 450, a third heat exchanger 420, a third valve 460, a hot water storage tank 430, and a fourth valve 470 connected in sequence. A circulating pump is connected to the second outlet of the second heat exchanger 170. The hot-side inlet of the third heat exchanger 420 is connected to the low-pressure cylinder 330 through a fifth valve 480. The hot-side outlet of the third heat exchanger 420 is connected to the condenser 340. The cold-side inlet of the third heat exchanger 420 is connected to the cold water storage tank 410 through a second valve 450. The cold-side outlet of the third heat exchanger 420 is connected to the hot water storage tank 430 through a fourth valve 470. The inlet of the cold water storage tank 410 is connected to the second outlet of the second heat exchanger 170 through a first valve 440. The outlet of the hot water storage tank 430 is connected to the second inlet of the second heat exchanger 170 through a third valve 460.

[0079] The process for renovating decommissioned units is as follows:

[0080] First, the boiler system of the decommissioned thermal power unit is dismantled, while the steam turbine power generation system 300 is retained. Second, a third heat exchanger 420 is connected to the outlet of the low-pressure cylinder 330 of the steam turbine power generation system 300 to form a waste heat recovery path. A superheater 240 and a reheater 210 are arranged in parallel between the high-pressure cylinder 310 and the intermediate-pressure cylinder 320 of the steam turbine power generation system 300 to form a steam generation system 200. A heat pump storage system 100, including a compressor 130, a first heat exchanger 140, a regenerator 150, and a turbine 160, is installed in the reserved space within the plant area and connected to the steam generation system 200 via molten salt pipelines. During the charging phase, the compressor 130 is driven by an electric motor to compress gas, converting electrical energy into circulating gas heat energy, which is then used to heat the molten salt in the low-temperature molten salt storage tank 110 via the first heat exchanger 140.

[0081] It should be noted that, in any of the above embodiments, as Figure 1 As shown, the feedwater and thermal storage pressurized water in the steam generation system 200 have the same meaning as water, representing a working fluid.

[0082] In the operation mode of the energy storage system of this application embodiment, during the discharge phase, the superheater 240 and reheater 210 of the steam generation system 200 heat the feedwater to generate steam, which drives the steam turbine power generation system 300 to generate electricity; during the discharge process, the waste heat of the exhaust steam of the steam turbine is recovered through the third heat exchanger 420, and the heat storage pressurized water is transported to the second heat exchanger 170 through the circulating pump for use as a low-temperature heat source for the heat pump heat storage system 100 during the charging phase.

[0083] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only.

[0084] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A Carnot battery energy storage system, characterized in that, include: A heat pump thermal storage system (100) includes a low-temperature molten salt storage tank (110), a high-temperature molten salt storage tank (120), and a compressor (130), a first heat exchanger (140), a regenerator (150), a turbine (160), and a second heat exchanger (170) connected in sequence. The low-temperature molten salt storage tank (110), the first heat exchanger (140), and the high-temperature molten salt storage tank (120) are connected in sequence. A steam generating system (200) includes a reheater (210) and a preheater (220), an evaporator (230) and a superheater (240) connected in sequence. The reheater (210) and the superheater (240) are both connected to the outlet of the high-temperature molten salt storage tank (120), and the reheater (210) and the superheater (240) are both connected to the evaporator (230). The inlet of the low-temperature molten salt storage tank (110) is connected to the preheater (220). A steam turbine power generation system (300), wherein the reheater (210) and the preheater (220) are both connected to the steam turbine power generation system (300); Waste heat recovery system (400), the steam turbine power generation system (300) is connected to the waste heat recovery system (400), and the waste heat recovery system (400) is connected to the second heat exchanger (170).

2. The Carnot battery energy storage system according to claim 1, characterized in that, The first heat exchanger (140), the regenerator (150), and the second heat exchanger (170) each have a first inlet, a first outlet, a second inlet, and a second outlet. The outlet of the compressor (130) is connected to the first inlet of the first heat exchanger (140), the first outlet of the first heat exchanger (140) is connected to the first inlet of the regenerator (150), the first outlet of the regenerator (150) is connected to the inlet of the compressor (130), the second outlet of the regenerator (150) is connected to the inlet of the turbine (160), the outlet of the turbine (160) is connected to the first inlet of the second heat exchanger (170), the first outlet of the second heat exchanger (170) is connected to the second inlet of the regenerator (150), and the second inlet and the second outlet of the second heat exchanger (170) are both connected to the waste heat recovery system (400).

3. The Carnot battery energy storage system according to claim 2, characterized in that, The steam turbine power generation system (300) includes a high-pressure cylinder (310) and a medium-pressure cylinder (320), a low-pressure cylinder (330), a condenser (340), a low-pressure heating group (350), a deaerator (360), and a high-pressure heating group (370) connected in sequence. The reheater (210), the preheater (220), the evaporator (230), and the superheater (240) all have a second inlet and a second outlet. The second inlet of the preheater (220) is connected to the high-pressure heating group (370). The working fluid flowing in from the second inlet of the preheater (220) passes sequentially through the evaporator (230) and the superheater (240), and flows from the second outlet of the superheater (240) into the inlet of the high-pressure cylinder (310). The second inlet of the reheater (210) is connected to the outlet of the high-pressure cylinder (310), and the second outlet of the reheater (210) is connected to the inlet of the intermediate-pressure cylinder (320).

4. The Carnot battery energy storage system according to claim 3, characterized in that, The high-pressure heating group (370) includes a first high-pressure heater (371), a second high-pressure heater (372), and a third high-pressure heater (373) connected in sequence. The high-pressure cylinder (310) and the intermediate-pressure cylinder (320) each have at least two exhaust ports. The two exhaust ports of the high-pressure cylinder (310) are respectively connected to the first high-pressure heater (371) and the second high-pressure heater (372). One exhaust port of the intermediate-pressure cylinder (320) is connected to the third high-pressure heater (373), and the other exhaust port of the intermediate-pressure cylinder (320) is connected to the deaerator (360). The working fluid flowing out of the deaerator (360) flows sequentially through the first high-pressure heater (371), the second high-pressure heater (372) and the third high-pressure heater (373) into the second inlet of the preheater (220).

5. The Carnot battery energy storage system according to claim 4, characterized in that, The low-pressure heating group (350) includes at least two low-pressure heaters (351) connected in sequence. The low-pressure cylinder (330) has at least two low-pressure exhaust ports. The two low-pressure exhaust ports are connected one-to-one with the second inlets of the two low-pressure heaters (351). The first inlet of one low-pressure heater (351) is connected to the first outlet of the condenser (340), and the first outlet of the other low-pressure heater (351) is connected to the deaerator (360). The working fluid flowing out from the first outlet of the condenser (340) flows sequentially through the low-pressure heater (351), the deaerator (360) and the high-pressure heating group (370) into the second inlet of the preheater (220).

6. The Carnot battery energy storage system according to any one of claims 3-5, characterized in that, The waste heat recovery system (400) includes a circulating pump, a cold water storage tank (410), a third heat exchanger (420), and a hot water storage tank (430) connected in sequence. The hot side inlet of the third heat exchanger (420) is connected to the low-pressure cylinder (330), the hot side outlet of the third heat exchanger (420) is connected to the condenser (340), the cold side inlet of the third heat exchanger (420) is connected to the outlet of the cold water storage tank (410), the cold side outlet of the third heat exchanger (420) is connected to the inlet of the hot water storage tank (430), the inlet of the cold water storage tank (410) is connected to the second outlet of the second heat exchanger (170), and the outlet of the hot water storage tank (430) is connected to the second inlet of the second heat exchanger (170).

7. The Carnot battery energy storage system according to claim 6, characterized in that, The waste heat recovery system (400) further includes a first valve (440), a second valve (450), a third valve (460), and a fourth valve (470). The third heat exchanger (420) is connected to the cold water storage tank (410) through the second valve (450). The cold side outlet of the third heat exchanger (420) is connected to the hot water storage tank (430) through the fourth valve (470). The inlet of the cold water storage tank (410) is connected to the second heat exchanger (170) through the first valve (440). The outlet of the hot water storage tank (430) is connected to the second heat exchanger (170) through the third valve (460). The first valve (440) and the fourth valve (470) are both open during charging, and the second valve (450) and the third valve (460) are both open during discharging.

8. The Carnot battery energy storage system according to claim 7, characterized in that, The waste heat recovery system (400) further includes a fifth valve (480), and the third heat exchanger (420) is connected to the low-pressure cylinder (330) through the fifth valve (480). The fifth valve (480) is used to open during discharge to regulate the flow rate from the exhaust port of the low-pressure cylinder (330) into the third heat exchanger (420).

9. The Carnot battery energy storage system according to any one of claims 1-5, characterized in that, It also includes a first drive unit (500) having a first shaft to which both the compressor (130) and the turbine (160) are connected, and the first drive unit (500) is configured to drive the compressor (130) to compress gas during peak power load.

10. The Carnot battery energy storage system according to any one of claims 3-5, characterized in that, It also includes a second drive unit (600) having a second shaft, wherein the high-pressure cylinder (310), the medium-pressure cylinder (320) and the low-pressure cylinder (330) are all connected to the second shaft.

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