Fused salt energy storage system with seal

Abstract

The invention provides a fused salt energy storage system with a seal, and relates to the technical field of energy storage. The fused salt energy storage system comprises a high-temperature storage tank used for storing hot fused salt; the low-temperature storage tank is used for storing the cold molten salt; the nitrogen supply device is used for conveying nitrogen into the high-temperature storage tank and the low-temperature storage tank; the balance pipeline is used for balancing the internal pressure of the high-temperature storage tank and the low-temperature storage tank; a heat exchange working medium flows through the heat exchange device, the hot molten salt stored in the high-temperature storage tank can flow through the heat exchange device and exchange heat with the flowing heat exchange working medium in the heat exchange device, and the hot molten salt becomes cold molten salt after releasing heat and enters the low-temperature storage tank; or the cold fused salt stored in the low-temperature storage tank can flow through the heat exchange device and exchanges heat with the flowing heat exchange working medium in the heat exchange device, and the cold fused salt becomes hot fused salt after absorbing heat and enters the high-temperature storage tank. The fused salt energy storage system solves the problems that in the prior art, ternary salt in fused salt energy storage is prone to oxidation, so that the melting point of fused salt rises, and the heat storage efficiency is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly to a molten salt energy storage system with a seal. Background Art

[0002] In the field of solar thermal energy storage, molten salt is a commonly used heat storage medium, mainly using binary salts. Since its chemical properties are relatively stable, special nitrogen sealing is not required. However, with the development of coal-fired power molten salt heat storage technology, the application of ternary salts has gradually increased. Ternary salts are prone to oxidation to form nitrates during storage, resulting in an increase in the melting point of the molten salt. This not only reduces the heat storage efficiency but may also pose safety hazards and affect the heat storage efficiency. Therefore, there is an urgent need to design a sealing system to prevent the oxidation reaction of ternary salts, thereby improving the heat storage performance of the heat storage system. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a molten salt energy storage system with a seal, which is used to solve the problem that ternary salts in molten salt energy storage in the prior art are prone to oxidation, resulting in an increase in the melting point of the molten salt and a reduction in the heat storage efficiency.

[0004] To achieve the above purpose, on the one hand, the present invention provides a molten salt energy storage system with a seal, and the molten salt energy storage system with a seal includes: A high-temperature storage tank for storing hot molten salt; A low-temperature storage tank for storing cold molten salt; A nitrogen supply device connected to the high-temperature storage tank and the low-temperature storage tank through pipelines, and used to transport nitrogen into the high-temperature storage tank and the low-temperature storage tank to prevent the hot molten salt in the high-temperature storage tank and the cold molten salt in the low-temperature storage tank from oxidizing; A balance pipeline connected between the high-temperature storage tank and the low-temperature storage tank, and used to balance the internal pressures of the high-temperature storage tank and the low-temperature storage tank; A heat exchange device connected to the high-temperature storage tank and the low-temperature storage tank. The heat exchange device is configured to have a heat exchange medium flowing through it. The hot molten salt stored in the high-temperature storage tank can flow through the heat exchange device and exchange heat with the flowing heat exchange medium. After the hot molten salt releases heat, it becomes cold molten salt and enters the low-temperature storage tank. After the heat exchange medium absorbs heat, it rises in temperature and is discharged from the heat exchange device. Or the cold molten salt stored in the low-temperature storage tank can flow through the heat exchange device and exchange heat with the flowing heat exchange medium. After the cold molten salt absorbs heat, it becomes hot molten salt and enters the high-temperature storage tank. After the heat exchange medium loses heat, it drops in temperature and is discharged from the heat exchange device.

[0005] Specifically, the nitrogen supply device includes: a nitrogen generator and a gas storage tank; The nitrogen generator is used to generate nitrogen and transport the generated nitrogen to the gas storage tank; The gas storage tank is respectively connected to the high-temperature storage tank and the low-temperature storage tank through pipelines, and is used to store nitrogen and transport the stored nitrogen to the high-temperature storage tank and the low-temperature storage tank.

[0006] Specifically, the nitrogen supply device further includes: a nitrogen generation controller and a first pressure sensor; The first pressure sensor is disposed inside the gas storage tank, electrically connected to the nitrogen generation controller, and is used to detect the nitrogen pressure inside the gas storage tank and transmit the nitrogen pressure to the nitrogen generation controller; The nitrogen generation controller is electrically connected to the nitrogen generator and is used to control the nitrogen generator to turn on or off according to the nitrogen pressure inside the gas storage tank.

[0007] Specifically, the molten salt energy storage system with a seal further includes: a salt drainage tank, which is connected to the high-temperature storage tank, the low-temperature storage tank, and the gas storage tank through pipelines, and is used to temporarily store the hot molten salt of the high-temperature storage tank and / or the cold molten salt of the low-temperature storage tank.

[0008] Specifically, the nitrogen supply device includes: a pair of pressure balance valves, and one pressure balance valve is provided on each of the connecting pipelines between the gas storage tank and the high-temperature storage tank and between the gas storage tank and the low-temperature storage tank.

[0009] Specifically, the molten salt energy storage system with a seal further includes: safety valves respectively disposed on the high-temperature storage tank and the low-temperature storage tank.

[0010] Specifically, the molten salt energy storage system with a seal further includes: nitrogen discharge valves respectively disposed on the high-temperature storage tank and the low-temperature storage tank.

[0011] Specifically, the molten salt energy storage system with a seal further includes: a composition detection device, which is connected to the high-temperature storage tank and the low-temperature storage tank, and is used to detect the composition of the hot molten salt in the high-temperature storage tank and the composition of the cold molten salt in the low-temperature storage tank.

[0012] Specifically, the molten salt energy storage system with a seal further includes: a salt replenishing device, which is connected to the high-temperature storage tank and the low-temperature storage tank and is electrically connected to the composition detection device, and is used to specifically replenish the hot molten salt to the high-temperature storage tank according to the composition of the hot molten salt, and is also used to specifically replenish the cold molten salt to the low-temperature storage tank according to the composition of the cold molten salt.

[0013] Specifically, the molten salt energy storage system with a seal further includes: liquid level gauges respectively disposed in the high-temperature storage tank and the low-temperature storage tank, and the liquid level gauges are used to respectively detect the liquid level of the hot molten salt in the high-temperature storage tank and the liquid level of the cold molten salt in the low-temperature storage tank.

[0014] The sealed molten salt energy storage system provided by the present invention includes a high-temperature storage tank for storing hot molten salt and a low-temperature storage tank for storing cold molten salt. To prevent the oxidation of hot and cold molten salts, nitrogen is supplied to the high-temperature and low-temperature storage tanks through a nitrogen supply device. The nitrogen entering the high-temperature storage tank can isolate the hot molten salt from contact with air, and the nitrogen entering the low-temperature storage tank can isolate the cold molten salt from contact with air, thereby avoiding the oxidation of hot and cold molten salts. At the same time, a balance pipeline is connected between the high-temperature and low-temperature storage tanks. In this way, nitrogen can flow between the high-temperature and low-temperature storage tanks through the balance pipeline, so as to maintain the pressure balance inside the high-temperature and low-temperature storage tanks. A heat exchange device connected to the high-temperature and low-temperature storage tanks facilitates the heat exchange between the hot or cold molten salt and the flowing heat exchange working medium in the heat exchange device, so that the sealed molten salt energy storage system can store or release heat. The sealed molten salt energy storage system provided by the present invention solves the problem in the prior art that ternary salts in molten salt energy storage are prone to oxidation, resulting in an increase in the melting point of molten salt and a decrease in heat storage efficiency.

[0015] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent specific implementation section. Brief Description of the Drawings

[0016] The drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. They are used together with the following specific implementation to explain the embodiments of the present invention, but do not limit the embodiments of the present invention. In the drawings: Figure 1 is a layout schematic diagram of the sealed molten salt energy storage system provided by the present invention.

[0017] Description of the Reference Numerals in the Drawings 1 - High-temperature storage tank; 2 - Low-temperature storage tank; 3 - Salt draining tank; 4 - Gas storage tank; 5 - Nitrogen generator; 6 - Balance pipeline; 7 - Salt replenishing device; 8 - Pressure balance valve; 9 - Safety valve; 10 - Nitrogen discharge valve; 11 - Heat exchange device. Specific Embodiments

[0018] The following will describe in detail the specific embodiments of the embodiments of the present invention with reference to the drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention.

[0019] Figure 1 is a layout schematic diagram of the sealed molten salt energy storage system. As Figure 1 shown, on the one hand, the present invention provides a sealed molten salt energy storage system, and the sealed molten salt energy storage system includes: A high-temperature storage tank 1 for storing hot molten salt; A low-temperature storage tank 2 for storing cold molten salt; A nitrogen supply device is connected to a high-temperature storage tank 1 and a low-temperature storage tank 2 through pipelines, and is used to transport nitrogen into the high-temperature storage tank 1 and the low-temperature storage tank 2 to prevent the molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2 from oxidizing; A balance pipeline 6 is connected between the high-temperature storage tank 1 and the low-temperature storage tank 2 and is used to balance the internal pressures of the high-temperature storage tank 1 and the low-temperature storage tank 2; A heat exchange device 11 is connected to the high-temperature storage tank 1 and the low-temperature storage tank 2. The heat exchange device 11 is arranged to have a heat exchange working medium flowing through it. The molten salt stored in the high-temperature storage tank 1 can flow through the heat exchange device 11 and exchange heat with the flowing heat exchange working medium in the heat exchange device 11. After the molten salt releases heat, it becomes cold molten salt and enters the low-temperature storage tank 2. After the heat exchange working medium absorbs heat, it rises in temperature and is discharged from the heat exchange device 11. Or the cold molten salt stored in the low-temperature storage tank 2 can flow through the heat exchange device 11 and exchange heat with the flowing heat exchange working medium in the heat exchange device 11. After the cold molten salt absorbs heat, it becomes molten salt and enters the high-temperature storage tank 1. After the heat exchange working medium loses heat, it drops in temperature and is discharged from the heat exchange device 11.

[0020] In the molten salt energy storage system with a seal provided by the present invention, the high-temperature storage tank 1 stores molten salt, and the low-temperature storage tank 2 stores cold molten salt. In order to prevent the molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2 from oxidizing, a nitrogen supply device is provided to supply nitrogen to the high-temperature storage tank 1 and the low-temperature storage tank 2. The nitrogen entering the high-temperature storage tank 1 and the low-temperature storage tank 2 can squeeze out the air in the high-temperature storage tank 1 and the low-temperature storage tank 2, thereby preventing the molten salt and the cold molten salt from coming into contact with air, and further preventing the molten salt and the cold molten salt from oxidizing. In order to keep the pressures in the high-temperature storage tank 1 and the low-temperature storage tank 2 balanced, a balance pipeline 6 is provided between the high-temperature storage tank 1 and the low-temperature storage tank 2. Nitrogen can flow between the high-temperature storage tank 1 and the low-temperature storage tank 2 through the balance pipeline 6, thereby balancing the pressures in the high-temperature storage tank 1 and the low-temperature storage tank 2. A heat exchange device 11 is provided and connected to the high-temperature storage tank 1 and the low-temperature storage tank 2. In this way, when the molten salt energy storage system with a seal stores heat, the cold molten salt in the low-temperature storage tank 2 is sent into the heat exchange device 11 to exchange heat with the heat exchange working medium flowing through the heat exchange device 11. After the cold molten salt absorbs the heat of the heat exchange working medium, it rises in temperature and becomes molten salt and is discharged from the heat exchange device 11 and enters the high-temperature storage tank 1 for storage. After the heat exchange working medium loses heat, its temperature drops and it is discharged from the heat exchange device 11; when the molten salt energy storage system with a seal releases heat, the molten salt in the high-temperature storage tank 1 is sent into the heat exchange device 11, and the molten salt exchanges heat with the heat exchange working medium in the heat exchange device 11. After the molten salt releases heat, it drops in temperature and becomes cold molten salt and enters the low-temperature storage tank 2. After the heat exchange working medium absorbs the heat of the molten salt, it rises in temperature and is discharged from the heat exchange device 11. The molten salt energy storage system with a seal provided by the present application can prevent the molten salt and the cold molten salt from oxidizing by transporting nitrogen into the high-temperature storage tank 1 and the low-temperature storage tank 2. At the same time, the molten salt and the cold molten salt exchange heat with the heat exchange working medium in the heat exchange device 11, and the heat release and heat storage of the molten salt energy storage system with a seal can be completed, solving the problem that in the prior art, ternary salts in molten salt energy storage are prone to oxidation, resulting in an increase in the melting point of the molten salt and a reduction in the heat storage efficiency.

[0021] In one embodiment, as Figure 1 shown, the nitrogen supply device includes: a nitrogen generator 5 and a gas storage tank 4; The nitrogen generator 5 is used to produce nitrogen and transport the produced nitrogen to the gas storage tank 4; The gas storage tank 4 is respectively connected to the high-temperature storage tank 1 and the low-temperature storage tank 2 through pipelines, and is used to store nitrogen and transport the stored nitrogen to the high-temperature storage tank 1 and the low-temperature storage tank 2.

[0022] The nitrogen supply device further includes: a nitrogen production controller and a first pressure sensor; The first pressure sensor is arranged in the gas storage tank 4 and is electrically connected to the nitrogen production controller, and is used to detect the nitrogen pressure in the gas storage tank 4 and transmit the nitrogen pressure to the nitrogen production controller; The nitrogen production controller is electrically connected to the nitrogen generator 5, and is used to control the nitrogen generator 5 to start or stop according to the nitrogen pressure in the gas storage tank 4.

[0023] The nitrogen supply device includes: a pair of pressure balance valves 8, and one pressure balance valve 8 is arranged on each of the connecting pipelines between the gas storage tank 4 and the high-temperature storage tank 1 and between the gas storage tank 4 and the low-temperature storage tank 2.

[0024] In order to transport nitrogen to the high-temperature storage tank 1 and the low-temperature storage tank 2, a nitrogen generator 5 and a gas storage tank 4 are provided. The gas storage tank 4 is connected to the high-temperature storage tank 1 and the low-temperature storage tank 2 through pipelines, and one pressure balance valve 8 is arranged on the connecting pipeline between the gas storage tank 4 and the high-temperature storage tank 1, and another pressure balance valve 8 is arranged on the connecting pipeline between the gas storage tank 4 and the low-temperature storage tank 2. Through the provided pressure balance valves 8, the gas storage tank 4 can freely transport nitrogen to the high-temperature storage tank 1 or the low-temperature storage tank 2. The nitrogen produced by the nitrogen generator 5 is first stored in the gas storage tank 4, and then the nitrogen is transported from the gas storage tank 4 to the high-temperature storage tank 1 and the low-temperature storage tank 2. Transporting nitrogen from the gas storage tank 4 to the high-temperature storage tank 1 and the low-temperature storage tank 2 can ensure the stable pressure of the delivered nitrogen. In order to ensure sufficient nitrogen storage in the gas storage tank 4, a first pressure sensor is arranged in the gas storage tank 4 to detect the pressure in the gas storage tank 4. The nitrogen production controller is arranged on the nitrogen generator 5 and is electrically connected to the first pressure sensor. The nitrogen production controller controls the start or stop of the nitrogen generator 5 according to the pressure in the gas storage tank 4. When the pressure in the gas storage tank 4 drops to the lowest set pressure, the nitrogen production controller controls the nitrogen generator 5 to start working to generate nitrogen and supplement it to the gas storage tank 4. When the pressure in the gas storage tank 4 reaches the highest set pressure, the nitrogen production controller controls the nitrogen generator 5 to stop working. Controlling the start and stop of the nitrogen generator 5 according to the pressure value in the gas storage tank 4 can avoid unnecessary waste.

[0025] In order to facilitate temporarily storing the molten salt discharged from the high-temperature storage tank 1 and the low-temperature storage tank 2 when the molten salt energy storage system with a seal fails, asFigure 1 As shown in the figure, the sealed molten salt energy storage system further includes: a desalting tank 3, which is connected to the high-temperature storage tank 1, the low-temperature storage tank 2 and the gas storage tank 4 through pipelines, and is used for temporarily storing the hot molten salt in the high-temperature storage tank 1 and / or the cold molten salt in the low-temperature storage tank 2. The desalting tank 3 can receive the hot molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2. In order to prevent the hot molten salt or cold molten salt from oxidizing in the desalting tank 3, nitrogen is supplied to the desalting tank 3 from the gas storage tank 4. When the desalting tank 3 is in an empty tank state without receiving hot molten salt or cold molten salt, the gas storage tank 4 transports nitrogen to the desalting tank 3 to fill the desalting tank 3 with nitrogen. In this way, when the hot molten salt or cold molten salt enters the desalting tank 3 for temporary storage, it can avoid contact between the hot molten salt or cold molten salt and air.

[0026] In order to prevent damage to the high-temperature storage tank 1 and the low-temperature storage tank 2 when the internal pressure of the high-temperature storage tank 1 and the low-temperature storage tank 2 abnormally increases or decreases, such as Figure 1 As shown in the figure, the sealed molten salt energy storage system further includes: safety valves 9 respectively arranged on the high-temperature storage tank 1 and the low-temperature storage tank 2. By arranging the safety valves 9, when the internal pressure of the high-temperature storage tank 1 and the low-temperature storage tank 2 is abnormal, the safety valves 9 will automatically open to release the excess pressure and protect the high-temperature storage tank 1 and the low-temperature storage tank 2. In order to prevent excessive nitrogen in the high-temperature storage tank 1 and the low-temperature storage tank 2 from causing too high pressure in the high-temperature storage tank 1 and the low-temperature storage tank 2, the sealed molten salt energy storage system further includes: nitrogen discharge valves 10 respectively arranged on the high-temperature storage tank 1 and the low-temperature storage tank 2. The arranged nitrogen discharge valves 10 can discharge the excess nitrogen in the high-temperature storage tank 1 or the low-temperature storage tank 2 to prevent the pressure in the high-temperature storage tank 1 and the low-temperature storage tank 2 from being too high.

[0027] Specifically, the sealed molten salt energy storage system further includes: a composition detection device, which is connected to the high-temperature storage tank 1 and the low-temperature storage tank 2, and is used for detecting the composition of the hot molten salt in the high-temperature storage tank 1 and the composition of the cold molten salt in the low-temperature storage tank 2.

[0028] Specifically, the sealed molten salt energy storage system further includes: a salt replenishing device 7, which is connected to the high-temperature storage tank 1 and the low-temperature storage tank 2 and is electrically connected to the composition detection device, and is used for specifically replenishing the hot molten salt to the high-temperature storage tank 1 according to the composition of the hot molten salt, and is also used for specifically replenishing the cold molten salt to the low-temperature storage tank 2 according to the composition of the cold molten salt.

[0029] To ensure the heat supply capacity of the molten salt energy storage system with a seal, a component detection device is connected to the high-temperature storage tank 1 and the low-temperature storage tank 2. The component detection device is used to detect the components of the hot molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2. Usually, the components of the hot molten salt and the cold molten salt are the same, and they are both made by mixing various types of inorganic compounds in a certain ratio. Changes in the components of the hot molten salt and the cold molten salt can affect the operating temperature of the hot molten salt and the cold molten salt, as well as the heat supply capacity of the hot molten salt and the cold molten salt. Therefore, a component detection device is set up to regularly detect the components of the hot molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2, and determine whether the components in the hot molten salt or the cold molten salt have changed according to the detection results. If the detection results show that the components of the hot molten salt and the cold molten salt have changed, the make-up salt device 7 is used to supplement the hot molten salt or the cold molten salt into the high-temperature storage tank 1 or the low-temperature storage tank 2 specifically. Taking the ternary salt as an example, the ternary salt components include potassium nitrate, sodium nitrite, and sodium nitrate. Among them, the component ratio of potassium nitrate, sodium nitrite, and sodium nitrate is 53% potassium nitrate, 7% sodium nitrate, and 40% sodium nitrite. If the component ratio of potassium nitrate in the ternary salt changes, it will cause changes in the operating temperature and heat supply capacity of the formed ternary salt. To ensure the stable operating temperature and heat supply capacity of the ternary salt, the make-up salt device 7 can specifically supplement the hot molten salt or the cold molten salt according to the component changes of the ternary salt, so as to restore the components of the ternary salt and ensure the heat supply capacity of the ternary salt.

[0030] The molten salt energy storage system with a seal further includes: liquid level gauges respectively arranged in the high-temperature storage tank 1 and the low-temperature storage tank 2, and the liquid level gauges are used to detect the liquid level of the hot molten salt in the high-temperature storage tank 1 and the liquid level of the cold molten salt in the low-temperature storage tank 2 respectively.

[0031] If the reserves of the hot molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2 are small, it is easy to cause the temperature of the hot molten salt and the cold molten salt in the high-temperature storage tank 1 and the low-temperature storage tank 2 to lose heat faster. To avoid the too-fast temperature loss in the high-temperature storage tank 1 and the low-temperature storage tank 2, liquid level gauges are respectively arranged in the high-temperature storage tank 1 and the low-temperature storage tank 2 to detect the liquid level of the hot molten salt in the high-temperature storage tank 1 and the liquid level of the cold molten salt in the low-temperature storage tank 2. If the liquid levels in the high-temperature storage tank 1 and the low-temperature storage tank 2 are lower than the set liquid level, the make-up salt device 7 is used to specifically supplement molten salt into the high-temperature storage tank 1 and the low-temperature storage tank 2 to ensure the reserves of the hot molten salt in the high-temperature storage tank 1 and the cold molten salt in the low-temperature storage tank 2.

[0032] The sealed molten salt energy storage system provided by the present invention has a high-temperature storage tank for storing hot molten salt and a low-temperature storage tank for storing cold molten salt. To prevent the oxidation of hot molten salt and cold molten salt, nitrogen is supplied to the high-temperature storage tank and the low-temperature storage tank through a nitrogen supply device. The nitrogen entering the high-temperature storage tank can isolate the hot molten salt from contact with air, and the nitrogen entering the low-temperature storage tank can isolate the cold molten salt from contact with air, thereby avoiding the oxidation of hot molten salt and cold molten salt. At the same time, a balance pipe is connected between the high-temperature storage tank and the low-temperature storage tank. In this way, nitrogen can flow between the high-temperature storage tank and the low-temperature storage tank through the balance pipe, so as to maintain the pressure balance in the high-temperature storage tank and the low-temperature storage tank. A heat exchange device connected to the high-temperature storage tank and the low-temperature storage tank facilitates the heat exchange between the hot molten salt or cold molten salt and the flowing heat exchange medium in the heat exchange device, so that the sealed molten salt energy storage system can store heat or release heat. The sealed molten salt energy storage system provided by the present invention solves the problem in the prior art that ternary salts in molten salt energy storage are prone to oxidation, resulting in an increase in the melting point of the molten salt and a decrease in the heat storage efficiency.

[0033] The optional embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0034] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any suitable manner. To avoid unnecessary repetition, the embodiments of the present invention will not separately describe various possible combination methods.

[0035] In addition, any combination can be made between different embodiments of the present invention as long as it does not violate the idea of the embodiments of the present invention, and it should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. A sealed molten salt energy storage system, characterized in that: The sealed molten salt energy storage system comprises: A high temperature storage tank (1) for storing hot molten salt; A cryogenic storage tank (2) for storing cold molten salt; A nitrogen supply device is connected to the high-temperature storage tank (1) and the low-temperature storage tank (2) through a pipeline and is used to transport nitrogen to the high-temperature storage tank (1) and the low-temperature storage tank (2) to prevent oxidation of the hot molten salt in the high-temperature storage tank (1) and the cold molten salt in the low-temperature storage tank (2); A balancing pipe (6) connected between the high-temperature storage tank (1) and the low-temperature storage tank (2) and used to balance the internal pressures of the high-temperature storage tank (1) and the low-temperature storage tank (2); The heat exchange device (11) is connected to the high-temperature storage tank (1) and the low-temperature storage tank (2). The heat exchange device (11) is configured to have a heat exchange medium flowing through it. The hot molten salt stored in the high-temperature storage tank (1) can flow through the heat exchange device (11) and exchange heat with the heat exchange medium flowing through it in the heat exchange device (11). The hot molten salt releases heat to become cold molten salt and enters the low-temperature storage tank (2). The heat exchange medium absorbs heat and heats up before being discharged from the heat exchange device (11). Alternatively, the cold molten salt stored in the low-temperature storage tank (2) can flow through the heat exchange device (11) and exchange heat with the heat exchange medium flowing through it in the heat exchange device (11). The cold molten salt absorbs heat to become hot molten salt and enters the high-temperature storage tank (1). The heat exchange medium loses heat and cools before being discharged from the heat exchange device (11).

2. The sealed molten salt energy storage system according to claim 1, characterized in that: The nitrogen supply device comprises: a nitrogen generator (5) and a gas storage tank (4); The nitrogen generator (5) is used to generate nitrogen and transport the generated nitrogen to the gas storage tank (4); The gas storage tank (4) is connected to the high-temperature storage tank (1) and the low-temperature storage tank (2) respectively through pipelines, and is used to store nitrogen and transport the stored nitrogen to the high-temperature storage tank (1) and the low-temperature storage tank (2).

3. The sealed molten salt energy storage system according to claim 2, characterized in that: The nitrogen supply device further includes: a nitrogen generation controller and a first pressure sensor; The first pressure sensor is arranged in the gas storage tank (4), is electrically connected to the nitrogen generation controller, and is used to detect the nitrogen pressure in the gas storage tank (4), and transmit the nitrogen pressure to the nitrogen generation controller; The nitrogen generator controller is electrically connected to the nitrogen generator (5) and is used to control the nitrogen generator (5) to be turned on or off according to the nitrogen pressure in the gas storage tank (4).

4. The sealed molten salt energy storage system according to claim 2, characterized in that: The sealed molten salt energy storage system further comprises: a salt draining tank (3), which is connected to the high-temperature storage tank (1), the low-temperature storage tank (2) and the gas storage tank (4) through a pipeline and is used for temporarily storing the hot molten salt in the high-temperature storage tank (1) and / or the cold molten salt in the low-temperature storage tank (2).

5. The sealed molten salt energy storage system according to claim 2, characterized in that: The nitrogen supply device comprises: a pair of pressure balancing valves (8), one pressure balancing valve (8) being arranged on the connecting pipe between the gas storage tank (4) and the high-temperature storage tank (1) and on the connecting pipe between the gas storage tank (4) and the low-temperature storage tank (2).

6. The sealed molten salt energy storage system according to claim 1, characterized in that: The sealed molten salt energy storage system further comprises safety valves (9) respectively arranged on the high-temperature storage tank (1) and the low-temperature storage tank (2).

7. The sealed molten salt energy storage system according to claim 1, characterized in that: The sealed molten salt energy storage system further comprises: nitrogen release valves (10) respectively arranged on the high-temperature storage tank (1) and the low-temperature storage tank (2).

8. The sealed molten salt energy storage system according to claim 1, characterized in that: The sealed molten salt energy storage system further comprises: a composition detection device connected to the high-temperature storage tank (1) and the low-temperature storage tank (2) and used for detecting the composition of the hot molten salt in the high-temperature storage tank (1) and detecting the composition of the cold molten salt in the low-temperature storage tank (2).

9. The sealed molten salt energy storage system according to claim 8, characterized in that: The sealed molten salt energy storage system further comprises: a salt replenishing device (7), connected to the high-temperature storage tank (1) and the low-temperature storage tank (2), and electrically connected to the composition detection device, and used for replenishing hot molten salt into the high-temperature storage tank (1) in a targeted manner according to the composition of the hot molten salt, and for replenishing cold molten salt into the low-temperature storage tank (2) in a targeted manner according to the composition of the cold molten salt.

10. The sealed molten salt energy storage system according to claim 1, characterized in that: The sealed molten salt energy storage system further comprises: liquid level gauges respectively arranged in the high-temperature storage tank (1) and the low-temperature storage tank (2), and the liquid level of the hot molten salt in the high-temperature storage tank (1) and the liquid level of the cold molten salt in the low-temperature storage tank (2) are respectively detected by the liquid level gauges.

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