Heat pump fused salt energy storage system and method coupled with steam turbine

Abstract

The invention relates to the technical field of compressed gas energy storage and renewable energy sources, in particular to a heat pump fused salt energy storage system and method coupled with a steam turbine. The system comprises a heat pump device, an energy storage device, an energy release device and a heat storage device. The heat pump device is used for converting external electric energy into heat and absorbing the heat, and is also used for absorbing the heat in the heat storage device; the energy storage device is connected with the heat pump device and used for storing heat absorbed in the heat pump device in the energy storage device. The energy storage device is connected with the energy release device and is used for transferring heat in the energy storage device into the energy release device; the energy releasing device is connected with the heat storage device and used for storing heat generated after the energy releasing device generates electricity outwards in the heat storage device. The molten salt heat pump device is used for replacing a boiler, the energy conversion rate is high, meanwhile, coal consumption is reduced, carbon dioxide emission is avoided, and environment friendliness is achieved. The heat pump device is used for heating the fused salt, the energy conversion efficiency is higher than that of electric heating fused salt, and the operation economical efficiency of the system is better.

Description

Technical Field

[0001] The present invention relates to the fields of compressed gas energy storage and renewable energy technology, and in particular to a heat pump molten salt energy storage system coupled with a steam turbine and a method thereof. Background Art

[0002] Traditional power grids are experiencing a severe imbalance between peak and off-peak loads, necessitating an urgent need for peak and off-peak regulation. Energy storage technology is a key means of peak regulation. By storing off-peak power and releasing it during peak demand periods, the grid's power system has battery-like storage capacity, significantly reducing the pressure on power generation and consumption.

[0003] To date, large-scale energy storage technologies primarily include pumped hydro, compressed gas, and molten salt. Molten salt storage uses metal salts as a heat storage medium, storing energy as heat in molten salt tanks. Molten salt storage offers numerous advantages, including unrestricted geographical conditions, high energy density, long heat storage time, and low scalability costs, complementing the characteristics of new energy sources. When power generation is needed, molten salt flows from the hot storage tank into a heat exchanger, heating the turbine feedwater to generate high-pressure steam that drives the turbine. After cooling from the work, the low-temperature molten salt flows back to the cold storage tank, awaiting re-entry into the heating cycle. However, most current molten salt storage systems use electricity to directly heat the molten salt to raise its temperature. However, the low efficiency of electric heating has hampered its development. Furthermore, condensing steam turbines all suffer from cold-end losses, which prevent the utilization of low-grade heat and hinder the improvement of cycle efficiency.

[0004] Based on the above statements and analysis of existing technologies, it can be seen that how to improve the conversion efficiency from electrical energy to molten salt thermal energy is the optimization direction of the molten salt energy storage system, and how to reduce the cold end loss of the steam turbine is the optimization direction for improving the efficiency of the steam turbine system. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a heat pump molten salt energy storage system and method coupled with a steam turbine to address the shortcomings of low efficiency and large cold-end losses of traditional molten salt energy storage systems. The present invention can utilize a heat pump device to circulate heat for the molten salt during the energy storage process, thereby achieving higher energy conversion efficiency.

[0006] The present invention provides the following technical solutions: A heat pump molten salt energy storage system coupled with a steam turbine, the system comprising a heat pump device, an energy storage device, an energy release device and a heat storage device; A heat pump device, used to convert external electrical energy into heat and absorb it, and also used to absorb heat from a heat storage device; The energy storage device is connected to the heat pump device and is used to store the heat absorbed by the heat pump device in the energy storage device; The energy storage device is connected to the energy release device to transfer heat in the energy storage device to the energy release device; The energy release device is connected to the heat storage device and is used to store the heat generated by the energy release device after generating electricity externally in the heat storage device.

[0007] Furthermore, the heat pump device includes an electric motor, a compressor, a molten salt heat exchanger, a regenerator, an expander, a first heat exchanger, and a voltage stabilizing unit, wherein: The electric motor is connected to the compressor; The outlet of the compressor, the first side of the molten salt heat exchanger, the first side of the regenerator, the expander, the first heat exchanger, the pressure stabilizing unit, the second side of the regenerator, and the inlet of the compressor are connected in sequence to form a circulation loop.

[0008] Furthermore, the energy storage device includes a molten salt heat exchanger, a high-temperature molten salt tank, a high-temperature molten salt pump, a low-temperature molten salt tank, a low-temperature molten salt pump and a steam generator, wherein: The outlet of the second side of the molten salt heat exchanger, the high-temperature molten salt tank, the high-temperature molten salt pump, the first side of the steam generator, the low-temperature molten salt tank, the low-temperature molten salt pump and the inlet of the second side of the molten salt heat exchanger are connected in sequence to form a circulation loop.

[0009] Furthermore, the energy release device includes: a steam generator, a generator, a first steam turbine, a second steam turbine, a condenser, a condensate pump, a low-pressure heater, a deaerator, a feed water pump and a high-pressure heater, wherein: The first outlet of the second steam turbine is connected to the first inlet of the condenser; the outlet of the condenser is connected to the first inlet of the low-pressure heater through the condensate pump; the first outlet of the low-pressure heater is connected to the first inlet of the deaerator; the outlet of the deaerator is connected to the first inlet of the high-pressure heater through the feedwater pump; The first outlet of the high pressure heater is connected to the first steam turbine inlet through the first pipeline on the second side of the steam generator; The first outlet of the first steam turbine is connected to the inlet of the second steam turbine through a second pipe on the second side of the steam generator.

[0010] Furthermore, the second outlet of the first steam turbine is connected to the second inlet of the high-pressure heater; and the second outlet of the high-pressure heater is connected to the second inlet of the deaerator.

[0011] Furthermore, the second outlet of the second steam turbine is connected to the second inlet of the low-pressure heater; and the second outlet of the low-pressure heater is connected to the second inlet of the condenser.

[0012] Further, the third outlet of the second steam turbine is connected to the third inlet of the deaerator; The fourth outlet of the second steam turbine is connected to the heat storage device.

[0013] Furthermore, the heat storage device includes a heat storage unit and a first heat exchanger, wherein: The fourth outlet of the second steam turbine is connected to the first inlet of the heat storage unit; The first outlet of the heat storage unit is connected to the second side inlet of the first heat exchanger; The second side outlet of the first heat exchanger is connected to the second inlet of the heat storage unit; The second outlet of the heat storage unit is connected to the third inlet of the condenser.

[0014] A method for storing molten salt energy in a heat pump coupled to a steam turbine is also provided, using the above-mentioned system, the method comprising: During the energy storage process, the heat pump device absorbs external electrical energy and heat from the heat storage device; The heat in the heat pump device is transferred to the energy storage device for storage; The heat stored in the energy storage device is transferred to the energy release device; The energy release device receives heat from the energy storage device and uses the heat to generate external electricity; Part of the heat generated by the energy release device is self-circulated in the energy release device; The remaining heat after the energy release device generates electricity is transferred to the heat pump device through the heat storage device.

[0015] Furthermore, the process of collecting heat by the heat pump device includes: The generator receives external electrical energy to drive the compressor. After the working fluid passes through the compressor, the temperature of the working fluid in the heat pump device increases. After passing through the first side of the molten salt heat exchanger, the heat is transferred to the second side of the molten salt heat exchanger, and the temperature drops to a first threshold value. The working medium whose temperature drops to the first threshold value enters the first side of the regenerator and transfers heat to the second side of the regenerator, after which the temperature of the working medium drops to the second threshold value; The working fluid whose temperature drops to the second threshold value expands through the expander, then enters the first side of the first heat exchanger to absorb heat transferred by the heat storage device, the second side of the regenerator to absorb heat transferred from the first side of the regenerator, and then enters the compressor.

[0016] Furthermore, the process of collecting heat by the heat pump device also includes: When the heat pump device has pressure fluctuations or is started or stopped, the working fluid whose temperature drops to the second threshold value enters the first side of the first heat exchanger to absorb the heat transferred by the heat storage device and enters the pressure stabilizing unit for storage or release.

[0017] Furthermore, the process of storing energy in the energy storage device includes: During the energy storage process, when the heat pump device is running, the second side of the molten salt heat exchanger will receive the heat transferred by the heat pump device, and the low-temperature molten salt in the low-temperature molten salt tank will be heated and transferred to the high-temperature molten salt tank through the low-temperature molten salt pump.

[0018] Furthermore, the process of the energy release device generating electricity externally includes: When the first steam turbine and the second steam turbine of the energy release device are in operation, the molten salt in the high-temperature molten salt tank is transferred to the steam generator through the high-temperature molten salt pump, and the low-temperature molten salt with the remaining heat after the high-temperature steam is generated in the steam generator enters the low-temperature molten salt tank; The high-temperature steam generated in the steam generator enters the first steam turbine (14) and generates first electricity externally; The temperature of the high-temperature steam after the first external power generation is reduced to a third threshold value; The high-temperature steam whose temperature drops to the third threshold value flows out from the first outlet of the first steam turbine, is heated again by the first steam generator, and then enters the second steam turbine to generate a second power externally; The temperature of the high-temperature steam after the second external power generation is reduced to a fourth threshold value; After the high-temperature steam whose temperature has dropped to the fourth threshold flows out from the first outlet of the second steam turbine, it passes through the first inlet of the condenser, the outlet of the condenser, the condensate pump, the first inlet of the low-pressure heater, the first outlet of the low-pressure heater, the first inlet of the deaerator, the outlet of the deaerator, the feed water pump and the first inlet of the high-pressure heater, the first outlet of the high-pressure heater, enters the steam generator for heating, and then enters the first steam turbine.

[0019] Furthermore, the process of the energy release device releasing energy to the outside also includes: The high-temperature steam whose temperature is reduced to a fifth threshold value enters the deaerator from the second outlet of the first steam turbine through the second inlet and the second outlet of the high-pressure heater.

[0020] Furthermore, the high-temperature steam whose temperature drops to a sixth threshold flows out from the second outlet of the second steam turbine and then passes through the second inlet and the second outlet of the low-pressure heater in sequence into the condenser, and / or, The high-temperature steam whose temperature is reduced to the seventh threshold flows out from the third outlet of the second steam turbine and then enters the deaerator from the third inlet of the deaerator, and / or, The high-temperature steam whose temperature drops to the fourth threshold value enters the heat storage device from the fourth outlet of the second steam turbine, and enters the condenser after storing heat.

[0021] Furthermore, the high-temperature steam whose temperature is reduced to a fourth threshold value flows out from the fourth outlet of the second steam turbine and enters the heat storage device, including: In the energy release process, when the first steam turbine and the second steam turbine of the energy release device are in operation, the high-temperature steam whose temperature drops to the fourth threshold value flows out from the fourth outlet of the second steam turbine, passes through the first inlet of the heat storage unit, stores the heat in the heat storage device, and finally enters the condenser from the second outlet of the heat storage unit through the third inlet of the condenser.

[0022] Technical effects and advantages of the present invention: The power generation system of the present invention replaces the boiler with a molten salt heat pump device, has a high energy conversion rate, reduces coal consumption, has no carbon dioxide emissions, and is environmentally friendly.

[0023] The present invention utilizes a heat pump device to heat molten salt, and the energy conversion efficiency is higher than that of electrically heated molten salt, and the operation economy of the system is better.

[0024] The heat pump device of the present invention is equipped with a pressure stabilization unit. When the heat pump pressure is high, the system pressure is reduced by partially storing the carbon dioxide working fluid in a storage tank. When the heat pump pressure is low, the system pressure is increased by releasing some of the carbon dioxide working fluid stored in the storage tank into the heat pump device. This allows the use of additional storage tanks to ensure stable pressure during the circulation process. Furthermore, the start and stop of the heat pump device can be buffered and controlled (the working fluid is stored in the storage tank when the heat pump device is stopped and released from the storage tank when the heat pump device is started), making the system more stable and safe.

[0025] The present invention utilizes the heat of the exhaust steam of the last stage of the steam turbine to provide cold end heat to the heat pump device, thereby achieving maximum utilization of heat and making the overall efficiency of the system higher.

[0026] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram of a heat pump molten salt energy storage system coupled to a steam turbine provided in an embodiment of the present application.

[0028] In the figure: 1. Electric motor; 2. Compressor; 3. Molten salt heat exchanger; 4. Regenerator; 5. Expander; 6. First heat exchanger; 7. Voltage stabilizing unit; 8. High-temperature molten salt tank; 9. High-temperature molten salt pump; 10. Low-temperature molten salt tank; 11. Low-temperature molten salt pump; 12. Steam generator; 13. Generator; 14. First steam turbine; 15. Second steam turbine; 16. Condenser; 17 Condensate pump; 18. Low-pressure heater; 19. Deaerator; 20. Feedwater pump; 21. High-pressure heater; 22. Heat storage unit. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] To address the deficiencies of the prior art, the present invention discloses a heat pump molten salt energy storage system coupled with a steam turbine, such as Figure 1 As shown, the system includes a heat pump device, an energy storage device, an energy release device and a heat storage device; the heat pump device is used to convert external electrical energy into heat and absorb it, and is also used to absorb heat in the heat storage device; wherein the heat converted from the external electrical energy is high-grade heat, and the heat of the heat storage device is low-grade heat (including final stage extraction steam and exhaust steam).

[0031] The energy storage device is connected to the heat pump device and is used to store the heat absorbed by the heat pump device in the energy storage device; the energy storage device is connected to the energy release device and is used to transfer the heat in the energy storage device to the energy release device; The energy release device is connected to the heat storage device and is used to store the heat generated by the energy release device after generating electricity externally in the heat storage device.

[0032] In a specific embodiment of the present invention, Figure 1 The heat pump device includes an electric motor 1, a compressor 2, a molten salt heat exchanger 3, a regenerator 4, an expander 5, a first heat exchanger 6, and a voltage stabilizing unit 7, wherein the electric motor 1 is connected to the compressor 2, and the outlet of the compressor 2, the first side of the molten salt heat exchanger 3, the first side of the regenerator 4, the expander 5, the first heat exchanger 6, the voltage stabilizing unit 7, the second side of the regenerator 4, and the inlet of the compressor 2 are connected in sequence to form a circulation loop.

[0033] In one specific embodiment of the present invention, the generator 1 in the heat pump device drives the compressor 2, allowing the relatively high-temperature heat pump fluid to enter the compressor 2, increasing its pressure and further raising its temperature. The high-temperature fluid at the outlet of the compressor 2 transfers heat to the energy storage device through the first side of the molten salt heat exchanger 3. After the first side of the molten salt heat exchanger 3 transfers heat to the energy storage device, the heat pump fluid still at a certain temperature enters the first side of the regenerator 4, the expander 5, and the first side of the first heat exchanger 6, where it is converted into a low-temperature fluid. After entering the first side of the regenerator 4, the heat pump fluid still at a certain temperature enters the expander 5 for expansion and the first side of the first heat exchanger 6 for heating. Using the heat from the heat storage device, the expansion generates electricity, offsetting some of the power consumed by the compressor 2 while also raising the temperature of the fluid flowing out of the expander 5 and the first side of the first heat exchanger 6, thus facilitating heat recovery. After passing through the second side of the regenerator 4, the heat pump fluid returns to the inlet of the compressor 2, completing the energy storage cycle.

[0034] In a specific embodiment of the present invention, when the system stops operating or in other circumstances, the working fluid, after entering the expander 5 for expansion and being heated on the first side of the first heat exchanger 6, is directly stored in the pressure stabilizing unit 7; when the system operates normally, the working fluid flows out of the pressure stabilizing unit 7, passes through the second side of the regenerator 4, and returns to the inlet of the compressor 2, completing the energy storage cycle.

[0035] In a specific embodiment of the present invention, Figure 1 The energy storage device includes a molten salt heat exchanger 3, a high-temperature molten salt tank 8, a high-temperature molten salt pump 9, a low-temperature molten salt tank 10, a low-temperature molten salt pump 11 and a steam generator 12, wherein the outlet of the second side of the molten salt heat exchanger 3, the high-temperature molten salt tank 8, the high-temperature molten salt pump 9, the first side of the steam generator 12, the low-temperature molten salt tank 10, the low-temperature molten salt pump 11 and the inlet of the second side of the molten salt heat exchanger 3 are connected in sequence to form a circulation loop.

[0036] In a specific embodiment of the present invention, Figure 1 During the energy storage process, when the heat pump device is running, the low-temperature molten salt in the low-temperature molten salt tank 10 passes through the low-temperature molten salt pump 11 and enters the second side of the molten salt heat exchanger 3, causing the molten salt medium temperature to rise and be stored in the high-temperature molten salt tank 8. This achieves heat storage during the energy storage process (i.e., the operation of the heat pump device).

[0037] In a specific embodiment of the present invention, Figure 1 The energy release device includes: a steam generator 12, a generator 13, a first steam turbine 14, a second steam turbine 15, a condenser 16, a condensate pump 17, a low-pressure heater 18, a deaerator 19, a feedwater pump 20, and a high-pressure heater 21; wherein the first steam turbine 14 includes one inlet and two outlets, and the second steam turbine 15 includes one inlet and four outlets, wherein the first outlet of the second steam turbine 15 is connected to the first inlet of the condenser 16 for transferring part of the residual heat of the steam to the condenser 16; the outlet of the condenser 16 is connected to the first inlet of the low-pressure heater 18 through the condensate pump 17; the first outlet of the low-pressure heater 18 is connected to the first inlet of the deaerator 19; the outlet of the deaerator 19 is connected to the first inlet of the high-pressure heater 21 through the feedwater pump 20; the first outlet of the high-pressure heater 21 is connected to the inlet of the first steam turbine 14 through the first pipeline on the second side of the steam generator 12; and / or The second outlet of the second steam turbine 15 is connected to the second inlet of the low-pressure heater 18; the second outlet of the low-pressure heater 18 is connected to the second inlet of the condenser 16, and / or, The third outlet of the second steam turbine 15 is connected to the third inlet of the deaerator 19, and / or The fourth outlet of the second steam turbine 15 is connected to the heat storage device.

[0038] The first outlet of the first steam turbine 14 is connected to the inlet of the second steam turbine 15 through a second pipe on the second side of the steam generator 12. The second outlet of the first steam turbine 14 is connected to the second inlet of the high-pressure heater 21; and the second outlet of the high-pressure heater 21 is connected to the second inlet of the deaerator 19.

[0039] In a specific embodiment of the present invention, Figure 1 During the energy release process, when the energy release device is operating, the high-temperature molten salt in the high-temperature molten salt tank 8 passes through the high-temperature molten salt pump 9 and enters the first side of the steam generator 12, providing heat to the energy release device. At the same time, the molten salt medium temperature is reduced and stored in the low-temperature molten salt tank 10. This release of heat is achieved during the energy release process (i.e., the steam turbine operation process).

[0040] In a specific embodiment of the present invention, the heat storage device includes a heat storage unit 22 and a first heat exchanger 6, wherein the fourth outlet of the second steam turbine 15 is connected to the first inlet of the heat storage unit 22; the first outlet of the heat storage unit 22 is connected to the second side inlet of the first heat exchanger 6; the second side outlet of the first heat exchanger 6 is connected to the second inlet of the heat storage unit 22; and the second outlet of the heat storage unit 22 is connected to the third inlet of the condenser 16.

[0041] The heat lost at the cold end of the steam turbine is extracted through the final stage or exhaust steam of the second steam turbine 15 and stored in the heat storage unit 22. The heated low-temperature molten salt returns to the low-temperature molten salt tank 10. The steam after power generation passes through the condenser 16, condensate pump 17, low-pressure heater 18, deaerator 19, feedwater pump 20, and high-pressure heater 21, where it is reheated by the molten salt, completing the energy release cycle.

[0042] The high-temperature steam required for power generation by the first steam turbine 14 is generated by the feed water of the high-pressure heater 21 heated by the high-temperature molten salt tank 8. The reheated steam of the second steam turbine 15 is generated by the exhaust steam of the first steam turbine 14 heated by the high-temperature molten salt tank 8.

[0043] The circulating working medium of the heat pump device is gas: the working medium is selected according to the temperature range, and can be air, carbon dioxide, argon, etc.

[0044] The pressure reduction and heating units 5 and 6 in the heat pump device can be expanded, reduced in pressure and heated multiple times, and the heating heat comes from the heat stored in the heat storage unit 22 by the final extraction steam and exhaust steam of the second steam turbine 15 in the power generation process.

[0045] The pressure stabilizing unit 7 is: a pressure stabilizing unit is set after the pressure reducing and heating unit, which inflates and pressurizes the system when the system pressure is low, and stores and reduces the pressure of the system gas when the system pressure is high, so as to ensure the stability of the system operation.

[0046] The present invention also provides a heat pump molten salt energy storage method coupled with a steam turbine, the method comprising: The heat in the heat pump device is transferred to the energy storage device for storage; the heat stored in the energy storage device is transferred to the energy release device; the energy release device receives a portion of the heat stored in the heat storage device and uses the heat to release energy to the outside; the remaining heat stored in the heat storage device received by the energy release device is transferred to the heat pump device through the heat storage device.

[0047] The process of heat pump device collecting heat includes: Generator 1 drives compressor 2. The working fluid (1 MPa, 350°C) increases its pressure and temperature (5 MPa, 580°C) after passing through compressor 2. After passing through the first side of molten salt heat exchanger 3, the heat is transferred to the second side of molten salt heat exchanger 3, where the temperature drops to a first threshold value (5 MPa, 360°C). The working fluid whose temperature drops to the first threshold value (5 MPa, 360°C) enters the first side of the regenerator 4 and transfers heat to the second side of the regenerator 4, after which the temperature of the working fluid drops to the second threshold value (5 MPa, 60°C); the working fluid whose temperature drops to the second threshold value (5 MPa, 60°C) is expanded by the expander 5 (1 MPa, -15°C), and then enters the first side of the first heat exchanger 6 in sequence to absorb heat (1 MPa, 20°C) transferred from the heat storage device, and the second side of the regenerator 4 absorbs heat transferred from the first side of the regenerator 4, after which the working fluid temperature rises (1 MPa, 350°C) and enters the compressor 2.

[0048] In a specific embodiment of the present invention, the process of storing and releasing energy by the energy storage device includes: During the energy storage process, when the heat pump device is running, the second side of the molten salt heat exchanger 3 will receive the heat transferred by the heat pump device. At this time, the low-temperature molten salt in the low-temperature molten salt tank 10 is heated by the low-temperature molten salt pump 11 and enters the high-temperature molten salt tank 8.

[0049] Energy release process: When the energy release device is running, the heat in the high-temperature molten salt 8 is transferred to the steam generator 12 through the high-temperature molten salt pump 9. The low-temperature molten salt with the remaining heat after the high-temperature steam generated in the steam generator 12 enters the low-temperature molten salt tank 10, waiting for the heat of the next energy storage process.

[0050] The working fluid of the heat pump device increases its temperature and pressure through the compressor 2, stores heat in the high-temperature molten salt tank 8 through the molten salt heat exchanger 3, and is heated, expanded and depressurized at the first side of the regenerator 4 to ensure the inlet temperature of the compressor 2; then, the working fluid of the heat pump device recovers pressure energy through the expander 5 and the first heat exchanger 6; finally, the working fluid of the heat pump device increases its temperature through the second side of the regenerator 4, circulates in the heat pump device, and converts electrical energy into heat of the molten salt.

[0051] In the case of multiple expansion and heating of the expander 5 and the first heat exchanger 6, in order to avoid the presence of liquid at the outlet of the expander 5 due to the inlet temperature of the expander 5 being too low, it is necessary to use the heat stored in the heat storage unit 22 of the last-stage extraction steam and exhaust steam of the second steam turbine 15 during the energy release stage to provide the heat required by the step-down expander 5 and the first heat exchanger 6.

[0052] At the same time, there is a certain temperature requirement for the working fluid of the heat pump device after pressure reduction and heating before entering the regenerator 4. This part of heat also needs to be provided by the heat stored in the heat storage unit 22 of the last stage extraction steam and exhaust steam of the second steam turbine 15 during the energy release stage.

[0053] In a specific embodiment of the present invention, the process of the energy release device releasing energy to the outside includes: The high-temperature steam generated in the steam generator 12 enters the first steam turbine 14 and generates first electricity for the generator 13; The temperature of the high-temperature steam after the first power generation is reduced to a third threshold value (about 350°C); The high-temperature steam having a temperature reduced to a third threshold value (about 350° C.) flows out from the first outlet of the first steam turbine 14 , is reheated by the first steam generator 12 , and then enters the second steam turbine 15 to generate the second power for the generator 13 . The temperature of the high-temperature steam after the second power generation is reduced to a fourth threshold value (about 30-80°C); After the high-temperature steam whose temperature has dropped to the fourth threshold flows out from the first outlet of the second steam turbine 15, it passes through the first inlet of the condenser 16, the outlet of the condenser 16, the condensate pump 17, the first inlet of the low-pressure heater 18, the first outlet of the low-pressure heater 18, the first inlet of the deaerator 19, the outlet of the deaerator 19, the feed water pump 20 and the first inlet of the high-pressure heater 21, the first outlet of the high-pressure heater 21, enters the steam generator 12 for heating, and then enters the first steam turbine 14.

[0054] The high-temperature steam whose temperature is reduced to a fifth threshold value (about 400° C.) enters the deaerator 19 from the second outlet of the first steam turbine 14 through the second inlet and the second outlet of the high-pressure heater 21 .

[0055] The high-temperature steam whose temperature drops to the sixth threshold value (about 150° C.) flows out from the second outlet of the second steam turbine 15 , passes through the second inlet and the second outlet of the low-pressure heater 18 in sequence, and enters the condenser 16 .

[0056] The high-temperature steam whose temperature has been reduced to the seventh threshold value flows out from the third outlet of the second steam turbine 15 and then enters the deaerator 19 from the third inlet of the deaerator 19 .

[0057] The low-temperature steam whose temperature is reduced to a fourth threshold value (about 30-80° C.) enters the heat storage device 22 from the fourth outlet of the second steam turbine 15 .

[0058] In a specific embodiment of the present invention, the low-temperature steam whose temperature is reduced to a fourth threshold value (about 30-80° C.) flows out from the fourth outlet of the second steam turbine 15 and enters the heat storage device, including: The low-temperature steam whose temperature drops to a fourth threshold value (about 30-80°C) flows out from the fourth outlet of the second steam turbine 15, passes through the first inlet of the heat storage unit 22, the first outlet of the heat storage unit 22 in sequence, enters the second side of the first heat exchanger 6, the second inlet of the heat storage unit 22, the second outlet of the heat storage unit 22, and then enters the condenser 16 from the third inlet of the condenser 16.

[0059] The power generation system of the present invention replaces the boiler by generating and storing heat through a molten salt heat pump device, has a high energy conversion rate, reduces coal consumption, emits no carbon dioxide, and is environmentally friendly.

[0060] At the same time, the present invention utilizes a heat pump device to heat the molten salt, and the energy conversion efficiency is higher than that of electrically heated molten salt, and the operation economy of the system is better.

[0061] At the same time, the heat pump device of the present invention is provided with a pressure stabilizing unit, which uses an additional storage tank to ensure the pressure stability of the circulation process, and can buffer and control the start and stop of the heat pump device, making the system more stable and safe.

[0062] At the same time, the present invention utilizes the heat of the exhaust steam of the last stage of the steam turbine to achieve maximum utilization of the heat and make the overall efficiency of the system higher.

[0063] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A heat pump molten salt energy storage system coupled with a steam turbine, characterized in that: The system includes a heat pump device, an energy storage device, an energy release device and a heat storage device; A heat pump device, used to convert external electrical energy into heat and absorb it, and also used to absorb heat from a heat storage device; The energy storage device is connected to the heat pump device and is used to store the heat absorbed by the heat pump device in the energy storage device; The energy storage device is connected to the energy release device to transfer heat in the energy storage device to the energy release device; The energy release device is connected to the heat storage device and is used to store the heat generated by the energy release device after generating electricity externally in the heat storage device.

2. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 1, characterized in that: The heat pump device comprises an electric motor (1), a compressor (2), a molten salt heat exchanger (3), a regenerator (4), an expander (5), a first heat exchanger (6) and a voltage stabilizing unit (7), wherein: The motor (1) is connected to the compressor (2); The outlet of the compressor (2), the first side of the molten salt heat exchanger (3), the first side of the regenerator (4), the expander (5), the first heat exchanger (6), the pressure stabilizing unit (7), the second side of the regenerator (4), and the inlet of the compressor (2) are connected in sequence to form a circulation loop.

3. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 2, characterized in that: The energy storage device includes a molten salt heat exchanger (3), a high-temperature molten salt tank (8), a high-temperature molten salt pump (9), a low-temperature molten salt tank (10), a low-temperature molten salt pump (11) and a steam generator (12), wherein: The outlet of the second side of the molten salt heat exchanger (3), the high-temperature molten salt tank (8), the high-temperature molten salt pump (9), the first side of the steam generator (12), the low-temperature molten salt tank (10), the low-temperature molten salt pump (11) and the inlet of the second side of the molten salt heat exchanger (3) are connected in sequence to form a circulation loop.

4. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 1, characterized in that: The energy release device includes: a steam generator (12), a generator (13), a first steam turbine (14), a second steam turbine (15), a condenser (16), a condensate pump (17), a low-pressure heater (18), a deaerator (19), a feed water pump (20) and a high-pressure heater (21), wherein: The first outlet of the second steam turbine (15) is connected to the first inlet of the condenser (16); the outlet of the condenser (16) is connected to the first inlet of the low-pressure heater (18) through the condensate pump (17); the first outlet of the low-pressure heater (18) is connected to the first inlet of the deaerator (19); the outlet of the deaerator (19) is connected to the first inlet of the high-pressure heater (21) through the feed water pump (20); The first outlet of the high-pressure heater (21) is connected to the inlet of the first steam turbine (14) through the first pipe on the second side of the steam generator (12); The first outlet of the first steam turbine (14) is connected to the inlet of the second steam turbine (15) through a second pipe on the second side of the steam generator (12).

5. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 4, characterized in that: The second outlet of the first steam turbine (14) is connected to the second inlet of the high-pressure heater (21); and the second outlet of the high-pressure heater (21) is connected to the second inlet of the deaerator (19).

6. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 4, characterized in that: The second outlet of the second steam turbine (15) is connected to the second inlet of the low-pressure heater (18); and the second outlet of the low-pressure heater (18) is connected to the second inlet of the condenser (16).

7. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 4, characterized in that: The third outlet of the second steam turbine (15) is connected to the third inlet of the deaerator (19); The fourth outlet of the second steam turbine (15) is connected to the heat storage device.

8. The heat pump molten salt energy storage system coupled with a steam turbine according to claim 7, characterized in that: The heat storage device comprises a heat storage unit (22) and a first heat exchanger (6), wherein: The fourth outlet of the second steam turbine (15) is connected to the first inlet of the heat storage unit (22); The first outlet of the heat storage unit (22) is connected to the second side inlet of the first heat exchanger (6); The second side outlet of the first heat exchanger (6) is connected to the second inlet of the heat storage unit (22); The second outlet of the heat storage unit (22) is connected to the third inlet of the condenser (16).

9. A heat pump molten salt energy storage method coupled with a steam turbine, characterized in that: Using the system according to any one of claims 1 to 8, the method comprises: During the energy storage process, the heat pump device absorbs external electrical energy and heat from the heat storage device; The heat in the heat pump device is transferred to the energy storage device for storage; The heat stored in the energy storage device is transferred to the energy release device; The energy release device receives heat from the energy storage device and uses the heat to generate external electricity; Part of the heat generated by the energy release device is self-circulated in the energy release device; The remaining heat after the energy release device generates electricity is transferred to the heat pump device through the heat storage device.

10. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 9, characterized in that: The process of heat collection by a heat pump device includes: The generator (1) receives external electric energy to drive the compressor (2). After the working medium passes through the compressor (2), the temperature of the working medium in the heat pump device increases. After passing through the first side of the molten salt heat exchanger (3), the heat is transferred to the second side of the molten salt heat exchanger (3), and the temperature is reduced to a first threshold value. The working medium whose temperature has dropped to a first threshold value enters the first side of the regenerator (4) and transfers heat to the second side of the regenerator (4), whereupon the temperature of the working medium drops to a second threshold value; The working fluid, the temperature of which is reduced to the second threshold, expands through the expander (5) and then enters the first side of the first heat exchanger (6) to absorb heat transferred from the heat storage device, the second side of the regenerator (4) to absorb heat transferred from the first side of the regenerator (4), and then enters the compressor (2).

11. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 10, characterized in that: The process of heat collection by the heat pump device also includes: When the heat pump device has pressure fluctuations or is started or stopped, the working fluid whose temperature drops to a second threshold value enters the first side of the first heat exchanger (6) to absorb the heat transferred by the heat storage device, and the working fluid enters the pressure stabilizing unit (7) to be stored or released.

12. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 9, characterized in that: The process of storing energy in an energy storage device includes: During the energy storage process, when the heat pump device is in operation, the second side of the molten salt heat exchanger (3) receives the heat transferred by the heat pump device, and heats the low-temperature molten salt in the low-temperature molten salt tank (10) through the low-temperature molten salt pump (11) and transfers it to the high-temperature molten salt tank (8).

13. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 9, characterized in that: The process of the energy release device generating electricity includes: When the first steam turbine (14) and the second steam turbine (15) of the energy release device are in operation, the molten salt in the high-temperature molten salt tank (8) is transferred to the steam generator (12) through the high-temperature molten salt pump (9), and the low-temperature molten salt with the remaining heat after the high-temperature steam is generated in the steam generator (12) enters the low-temperature molten salt tank (10); The high-temperature steam generated in the steam generator (12) enters the first steam turbine (14) and generates first electricity externally; The temperature of the high-temperature steam after the first external power generation is reduced to a third threshold value; The high-temperature steam whose temperature has dropped to a third threshold value flows out from the first outlet of the first steam turbine (14), passes through the first steam generator (12), is heated again, and then enters the second steam turbine (15) to generate a second power externally; The temperature of the high-temperature steam after the second external power generation is reduced to a fourth threshold value; After the high-temperature steam whose temperature drops to the fourth threshold value flows out from the first outlet of the second steam turbine (15), it passes through the first inlet of the condenser (16), the outlet of the condenser (16), the condensate pump (17), the first inlet of the low-pressure heater (18), the first outlet of the low-pressure heater (18), the first inlet of the deaerator (19), the outlet of the deaerator (19), the first inlet of the feed water pump (20) and the high-pressure heater (21), the first outlet of the high-pressure heater (21), enters the steam generator (12), is heated, and then enters the first steam turbine (14).

14. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 13, characterized in that: The process of the energy release device releasing energy to the outside also includes: The high-temperature steam whose temperature is reduced to the fifth threshold value enters the deaerator (19) from the second outlet of the first steam turbine (14) through the second inlet of the high-pressure heater (21) and the second outlet of the high-pressure heater (21).

15. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 13, characterized in that: The high-temperature steam whose temperature has dropped to a sixth threshold value flows out of the second outlet of the second steam turbine (15), passes through the second inlet of the low-pressure heater (18), the second outlet of the low-pressure heater (18) and enters the condenser (16), and / or, The high-temperature steam whose temperature is reduced to the seventh threshold flows out from the third outlet of the second steam turbine (15) and enters the deaerator (19) from the third inlet of the deaerator (19), and / or, The high-temperature steam whose temperature drops to a fourth threshold value enters the heat storage device from the fourth outlet of the second steam turbine (15), and enters the condenser (16) after storing heat.

16. The heat pump molten salt energy storage method coupled with a steam turbine according to claim 15, characterized in that: The high-temperature steam whose temperature is reduced to a fourth threshold value flows out from the fourth outlet of the second steam turbine (15) and enters the heat storage device, including: In the energy release process, when the first steam turbine (14) and the second steam turbine (15) of the energy release device are in operation, the high-temperature steam whose temperature drops to the fourth threshold value flows out from the fourth outlet of the second steam turbine (15), passes through the first inlet of the heat storage unit (22), stores the heat in the heat storage device, and finally enters the condenser (16) from the second outlet of the heat storage unit (22) through the third inlet of the condenser (16).

Images