Energy storage system and operation method thereof

Abstract

The invention relates to the technical field of energy storage, in particular to an energy storage system and an operation method thereof. Comprising a heat storage tank, a plurality of sealed storage tanks are arranged in the heat storage tank, metal potassium is arranged in the sealed storage tanks, and fused salt is arranged between the heat storage tank and the sealed storage tanks; a fused salt outlet of the heat storage tank is connected with an electric heater and a heat exchanger through a salt outlet pipeline, and a fused salt circulating pump is arranged at the end, close to the heat storage tank, of the salt outlet pipeline. A fused salt outlet of the electric heater and a fused salt outlet of the heat exchanger are connected with a fused salt inlet of the heat storage tank through a salt inlet pipeline, and the heat exchanger is provided with a water inlet and a steam outlet. According to the energy storage system, vaporization latent heat brought by state change of metal potassium is adopted for energy storage, the occupied area of the fused salt storage tank is greatly saved, only the fused salt is adopted as a heat-conducting medium, and therefore the use amount of the fused salt is greatly reduced, and fused salt investment is reduced.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to an energy storage system and an operating method thereof. Background Art

[0002] High-temperature heat storage is a branch of the energy storage field. It has the advantages of mature technology, safety and efficiency, and is not restricted by geographical conditions. It has been rapidly developed. The types of high-temperature heat storage mainly include high-temperature steam heat storage, hot water heat storage, solid heat storage, molten salt heat storage, etc. Among them, molten salt heat storage is the most widely used. It is mainly used in solar thermal power generation, coupled thermal power unit peak regulation, independent energy storage power station, green electricity heating and other fields. Molten salt heat storage technology can be combined with existing coal-fired power plants. While storing energy on a large scale, it can also achieve deep peak regulation, frequency regulation, and external heating for coal-fired power plants.

[0003] At present, the field of molten salt heat storage mainly adopts a double-tank molten salt heat storage system, which has two molten salt storage tanks, a low-temperature tank and a high-temperature tank. When storing energy, the molten salt in the low-temperature tank is pumped out using a molten salt pump to absorb heat (it can absorb the energy of sunlight on the absorber, or it can be the heat energy provided by electric heating). The temperature of the molten salt rises and flows into the high-temperature tank, and the heat energy is stored; when releasing energy, the molten salt in the high-temperature tank is pumped out using a molten salt pump, exchanges heat with water, generates steam for external use, and the temperature of the molten salt drops and flows back to the low-temperature tank, completing a cycle.

[0004] When the molten salt storage system is in operation, the molten salt is continuously circulated between the low-temperature storage tank and the high-temperature storage tank. Both the low-temperature storage tank and the high-temperature storage tank need to meet all molten salt storage requirements, resulting in a large amount of storage space waste. In addition, since the specific heat capacity of molten salt is only 40% of that of water, the molten salt heat storage system requires a large amount of molten salt, which increases the system cost. Therefore, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide an energy storage system, which can save the floor space of the molten salt storage tank, reduce the amount of molten salt used, and reduce the system cost. The second object of the present invention is to provide an operation method of the above energy storage system.

[0006] The present invention provides an energy storage system, comprising a heat storage tank, wherein a plurality of sealed storage tanks are arranged inside the heat storage tank, wherein metallic potassium is arranged inside the sealed storage tank, and molten salt is arranged between the heat storage tank and the sealed storage tank; the molten salt outlet of the heat storage tank is respectively connected to an electric heater and a heat exchanger through a salt outlet pipeline, and a molten salt circulation pump is arranged at one end of the salt outlet pipeline close to the heat storage tank; the molten salt outlet of the electric heater and the molten salt outlet of the heat exchanger are connected to the molten salt inlet of the heat storage tank through a salt inlet pipeline, the water inlet of the heat exchanger is connected to a water supply pipeline, and the steam outlet of the heat exchanger is connected to a steam supply pipeline.

[0007] Furthermore, an upper fixed plate and a lower fixed plate are provided inside the heat storage tank, the sealed storage tank is arranged through the upper fixed plate and the lower fixed plate, an upper guide ring and a lower guide ring are provided at the bottom of the upper fixed plate and the lower fixed plate respectively, and a fixed support is provided outside the sealed storage tank, and the fixed support is fixedly connected to the bottom of the upper guide ring.

[0008] Furthermore, a plurality of flow holes are respectively formed through the upper fixing plate and the lower fixing plate, and a diameter of the flow holes is greater than 50 mm and less than 100 mm.

[0009] Furthermore, a drainage channel is provided at the bottom of the flow hole, and the height of the drainage channel is the same as the diameter of the flow hole.

[0010] Furthermore, a buffer tank is provided between the molten salt circulation pump and the heat storage tank.

[0011] Furthermore, a water pump is provided on the water supply pipeline.

[0012] Furthermore, a molten salt distributor is provided inside the heat storage tank, and the molten salt distributor is located below the sealed storage tank.

[0013] Furthermore, a first valve and a second valve are respectively provided at the molten salt inlet and the molten salt outlet of the electric heater.

[0014] Furthermore, a third valve and a fourth valve are respectively provided at the molten salt inlet and the molten salt outlet of the heat exchanger.

[0015] The present invention provides an operating method of the above energy storage system, comprising the following steps:

[0016] (1) When storing energy, the molten salt circulation pump is started to transport the molten salt in the heat storage tank to the electric heater, converting the electrical energy into thermal energy. After heating, the high-temperature molten salt returns to the heat storage tank. The high-temperature molten salt in the heat storage tank heats the liquid metal potassium in the sealed storage tank. The liquid metal potassium absorbs a large amount of latent heat of vaporization during the process of absorbing heat and transforming into gaseous metal potassium, thereby completing heat storage;

[0017] (2) When releasing energy, start the molten salt circulation pump and turn off the electric heater to transport the high-temperature molten salt in the heat storage tank to the heat exchanger. The high-temperature molten salt exchanges heat with the water entering the heat exchanger and becomes low-temperature molten salt. The water absorbs heat and evaporates into high-temperature water vapor, which is supplied to the outside. The low-temperature molten salt returns to the heat storage tank and absorbs the heat of the gaseous metallic potassium in the sealed storage tank. The gaseous metallic potassium releases the latent heat of vaporization and turns into liquid metallic potassium, completing the energy release.

[0018] In summary, compared with the prior art, the present invention has the following advantages:

[0019] The technical solution of the present invention uses the latent heat of vaporization brought about by the state change of metallic potassium for energy storage, which greatly saves the floor space of the molten salt storage tank and only uses molten salt as the heat transfer medium, thereby greatly reducing the amount of molten salt used and reducing the investment in molten salt; at the same time, metallic potassium is stored in a sealed storage tank, and the filling pressure of the sealed storage tank can be adjusted according to the heat storage temperature range required by actual production, and the temperature adjustment is simple and convenient; the arranged electric heater can draw electricity from the power grid for heat storage, and belongs to a large-scale long-term energy storage system, and the connection with new energy systems such as photovoltaic and wind power is conducive to suppressing the volatility of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the structure of an energy storage system in an embodiment of the present invention;

[0022] Figure 2 It is a schematic diagram of the connection between the upper fixing plate, the lower fixing plate and the sealed storage tank in an embodiment of the present invention;

[0023] Figure 3 1 is a top view of a heat storage tank in an embodiment of the present invention.

[0024] Explanation of the reference numerals: 1-heat storage tank; 101-upper fixed plate; 1011-upper guide ring; 102-lower fixed plate; 1021-lower guide ring; 103-flow hole; 104-drainage channel; 105-molten salt distributor; 2-sealed storage tank; 201-fixed support; 3-buffer tank; 4-molten salt circulation pump; 5-electric heater; 6-heat exchanger; 7-water feed pump; 8-salt outlet pipeline; 801-first salt outlet branch; 802-second salt outlet branch; 9-salt inlet pipeline; 901-first salt inlet branch; 902-second salt inlet branch; 10-first valve; 11-second valve; 12-third valve; 13-fourth valve. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] Example

[0029] An energy storage system, such as Figure 1 As shown, it includes a heat storage tank 1, and several sealed storage tanks 2 are installed inside the heat storage tank 1. The molten salt outlet of the heat storage tank 1 is connected to the electric heater 5 and the heat exchanger 6 respectively through the salt outlet pipe 8. The electric heater 5 and the heat exchanger 6 are connected to the molten salt inlet of the heat storage tank 1 through the salt inlet pipe 9. The heat exchanger 6 is provided with a water inlet and a steam outlet.

[0030] The heat storage tank 1 contains molten salt, which is located in the area between the inner wall of the heat storage tank 1 and the sealed storage tank 2. A molten salt outlet is provided at the lower part of the heat storage tank 1, and the molten salt outlet is connected to the salt outlet pipe 8. A molten salt circulation pump 4 is installed at one end of the salt outlet pipe 8 close to the heat storage tank 1, and a buffer tank 3 is installed between the molten salt circulation pump 4 and the heat storage tank 1. A first salt outlet branch pipe 801 and a second salt outlet branch pipe 802 are provided on the salt outlet pipe 8, and the first salt outlet branch pipe 801 is connected to the molten salt inlet of the electric heater 5, and the second salt outlet branch pipe 802 is connected to the molten salt inlet of the heat exchanger 6. A molten salt inlet is provided at the top of the heat storage tank 1, and the molten salt inlet is connected to the salt inlet pipe 9. A first salt inlet branch pipe 901 and a second salt inlet branch pipe 902 are provided on the salt inlet pipe 9, and the first salt inlet branch pipe 901 is connected to the molten salt outlet of the electric heater 5, and the second salt inlet branch pipe 902 is connected to the molten salt outlet of the heat exchanger 6. The first salt outlet branch pipe 801 is provided with a first valve 10, the first salt inlet branch pipe 901 is provided with a second valve 11, the second salt outlet branch pipe 802 is provided with a third valve 12, and the second salt inlet branch pipe 902 is provided with a fourth valve 13. A molten salt distributor 105 is provided inside the heat storage tank 1, and the salt inlet pipeline 9 extends into the heat storage tank 1 and is connected to the molten salt distributor 105, and the molten salt distributor 105 is located below the sealed storage tank 2.

[0031] The water inlet of the heat exchanger 6 is connected to a water supply pipeline, on which a water supply pump 7 is installed; the steam outlet of the heat exchanger 6 is connected to a steam supply pipeline to provide high-temperature steam to the outside.

[0032] The sealed storage tank 2 is filled with potassium metal, and the amount of potassium metal and the pressure inside the sealed storage tank 2 can be changed according to the heat storage temperature range required for actual production. The sealed storage tank 2 is tubular, with elliptical metal heads at both ends. The material is stainless steel, ceramics, and other materials that do not cause liquid metal brittle fracture with potassium metal. In order to ensure the sealing and thermal conductivity of potassium metal liquid, the wall thickness of the sealed storage tank 2 is 1-5 mm.

[0033] The molten salt filled between the heat storage tank 1 and the sealed storage tank 2 is used as a heat transfer medium. The molten salt in the heat storage tank 1 of this system includes but is not limited to binary molten salt, ternary molten salt, etc. An upper fixing plate 101 and a lower fixing plate 102 are installed inside the heat storage tank 1 to fix the sealed storage tank 2 to prevent the sealed storage tank 2 from moving due to the buoyancy of the molten salt. Figure 2As shown, the upper fixing plate 101 and the lower fixing plate 102 are respectively provided with mounting holes, the mounting holes of the upper fixing plate 101 are vertically aligned with the mounting holes of the lower fixing plate 102, the two ends of the sealed storage tank 2 are respectively located in the mounting holes of the upper fixing plate 101 and the lower fixing plate 102, and the outer wall of the sealed storage tank 2 is in contact with the mounting holes. The bottom of the upper fixing plate 101 and the lower fixing plate 102 are respectively fixed with an upper guide ring 1011 and a lower guide ring 1021, which are used to fix the radial position of the sealed storage tank 2, the inner walls of the upper guide ring 1011 and the lower guide ring 1021 are aligned with the mounting holes, the upper guide ring 1011 and the lower guide ring 1021 are respectively sleeved on the outside of the sealed storage tank 2, and the outer wall of the sealed storage tank 2 is fixedly installed with a fixed support 201, the top of the fixed support 201 is welded to the bottom of the upper guide ring 1011, and the fixed support 201 can be a ring plate, or a plurality of square plates arranged at intervals.

[0034] like Figure 2 and Figure 3 As shown, in order to ensure the free flow of the molten salt inside the heat storage tank 1, a plurality of circular flow holes 103 are provided on the upper fixed plate 101 and the lower fixed plate 102. To ensure the strength of the upper fixed plate 101 and the lower fixed plate 102, the diameter of the flow hole 103 is greater than 50 mm and less than 100 mm. The flow holes 103 on the upper fixed plate 101 and the lower fixed plate 102 correspond one to one. At the same time, in order to minimize the disturbance of the flow hole 103 to the molten salt flow field, an annular drainage channel 104 is fixed at the bottom of the flow hole 103, and the height of the drainage channel 104 is the same as the diameter of the flow hole 103.

[0035] The operating method of the energy storage system provided by the present invention is as follows:

[0036] (1) During energy storage, the third valve 12 and the fourth valve 13 are closed, the first valve 10 and the second valve 11 are opened, and the molten salt pump 4 is started to send the molten salt in the heat storage tank 1 to the electric heater 5 through the buffer tank 3, and the electric energy on the grid side is converted into thermal energy to heat the molten salt, and the molten salt is heated and returned to the heat storage tank 1; the high-temperature molten salt in the heat storage tank 1 transfers heat with the sealed storage tank 2 to heat the liquid metallic potassium in the sealed storage tank 2; as the heat storage process continues, the temperature of the molten salt continues to rise, and after reaching the vaporization temperature of the metallic potassium, the liquid metallic potassium in the sealed storage tank 2 absorbs heat and becomes gaseous metallic potassium, absorbing a large amount of latent heat of vaporization, and completing heat storage. The latent heat of vaporization of metallic potassium is about 1000 times the specific heat of the molten salt, so a large amount of heat can be stored in a small volume.

[0037] (2) When releasing energy, close the first valve 10 and the second valve 11, turn off the electric heater 5, open the third valve 12 and the fourth valve 13, start the molten salt circulation pump 4, and the high-temperature molten salt passes through the buffer tank 3 and enters the heat exchanger 6 to exchange heat with water. The water absorbs heat and evaporates into high-temperature and high-pressure steam, which is supplied to the outside. As the system continuously releases energy, the temperature of the molten salt in the heat storage tank 1 continues to decrease, and the molten salt transfers heat with the sealed storage tank 2, absorbing the heat of the gaseous metallic potassium. The gaseous metallic potassium releases the latent heat of vaporization and becomes liquid metallic potassium, completing the heat release process.

[0038] Compared with the traditional molten salt cold and hot dual-tank energy storage system, the energy storage system provided by the present invention has the following innovations: First, the present invention uses the latent heat of vaporization brought about by the state change of metallic potassium for energy storage, which greatly saves the floor space of the molten salt storage tank; second, the present invention only uses molten salt as a heat transfer medium, thereby greatly reducing the amount of molten salt used and reducing the investment in molten salt; third, in the present invention, liquid metallic potassium is stored in a sealed storage tank, and the filling pressure of the sealed storage tank can be adjusted according to the system heat storage temperature range, and the temperature adjustment is simple and convenient; fourth, in the present invention, the electric heater draws electricity from the power grid to store heat, which belongs to a large-scale long-term energy storage system, and the combination with new energy systems such as photovoltaic and wind power is conducive to suppressing the volatility of new energy.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An energy storage system, characterized in that: The invention comprises a heat storage tank (1), wherein a plurality of sealed storage tanks (2) are arranged inside the heat storage tank (1), wherein metallic potassium is arranged inside the sealed storage tank (2), and molten salt is arranged between the heat storage tank (1) and the sealed storage tank (2); the molten salt outlet of the heat storage tank (1) is respectively connected to an electric heater (5) and a heat exchanger (6) through a salt outlet pipe (8), and a molten salt circulation pump (4) is arranged at one end of the salt outlet pipe (8) close to the heat storage tank (1); the molten salt outlet of the electric heater (5) and the molten salt outlet of the heat exchanger (6) are connected to the molten salt inlet of the heat storage tank (1) through a salt inlet pipe (9), the water inlet of the heat exchanger (6) is connected to a water supply pipe, and the steam outlet of the heat exchanger (6) is connected to a steam supply pipe.

2. The energy storage system according to claim 1, characterized in that: An upper fixing plate (101) and a lower fixing plate (102) are provided inside the heat storage tank (1); the sealed storage tank (2) is arranged through the upper fixing plate (101) and the lower fixing plate (102); an upper guide ring (1011) and a lower guide ring (1021) are provided at the bottom of the upper fixing plate (101) and the lower fixing plate (102), respectively; a fixed support (201) is provided outside the sealed storage tank (2); the fixed support (201) is fixedly connected to the bottom of the upper guide ring (1011).

3. The energy storage system according to claim 2, characterized in that: The upper fixing plate (101) and the lower fixing plate (102) are respectively provided with a plurality of flow holes (103), and the diameter of the flow holes (103) is greater than 50 mm and less than 100 mm.

4. The energy storage system according to claim 3, characterized in that: A drainage channel (104) is provided at the bottom of the flow hole (103), and the height of the drainage channel (104) is the same as the diameter of the flow hole (103).

5. The energy storage system according to claim 1, characterized in that: A buffer tank (3) is provided between the molten salt circulation pump (4) and the heat storage tank (1).

6. The energy storage system according to claim 1, characterized in that: A water supply pump (7) is provided on the water supply pipeline.

7. The energy storage system according to claim 1, characterized in that: A molten salt distributor (105) is provided inside the heat storage tank (1), and the molten salt distributor (105) is located below the sealed storage tank (2).

8. The energy storage system according to claim 1, characterized in that: A first valve (10) and a second valve (11) are respectively provided at the molten salt inlet and the molten salt outlet of the electric heater (5).

9. The energy storage system according to claim 1, characterized in that: A third valve (12) and a fourth valve (13) are respectively provided at the molten salt inlet and the molten salt outlet of the heat exchanger (6).

10. An operating method of an energy storage system according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) When storing energy, the molten salt circulation pump (4) is started to transport the molten salt in the heat storage tank (1) to the electric heater (5), converting the electrical energy into thermal energy. The heated high-temperature molten salt is returned to the heat storage tank (1). The high-temperature molten salt in the heat storage tank (1) heats the liquid metal potassium in the sealed storage tank (2). The liquid metal potassium absorbs a large amount of latent heat of vaporization during the process of absorbing heat and converting into gaseous metal potassium, thereby completing heat storage; (2) When releasing energy, the molten salt circulation pump (4) is started and the electric heater (5) is turned off to transport the high-temperature molten salt in the heat storage tank (1) to the heat exchanger (6). The high-temperature molten salt exchanges heat with the water entering the heat exchanger (6) to become low-temperature molten salt. The water absorbs heat and evaporates into high-temperature water vapor, which is supplied to the outside. The low-temperature molten salt returns to the heat storage tank (1) to absorb the heat of the gaseous metallic potassium in the sealed storage tank (2). The gaseous metallic potassium releases the latent heat of vaporization and is converted into liquid metallic potassium, completing the energy release.

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