Phase-change modularized fused salt energy storage device and working method thereof

Abstract

The invention provides a phase-change modularized fused salt energy storage device and a working method thereof, and belongs to the technical field of fused salt energy storage. Comprising a heat accumulator, a fused salt storage tank is arranged in the heat accumulator, the fused salt storage tank comprises a fused salt inlet pipe, an overheating section coil pipe and a phase change section coil pipe are arranged in the fused salt storage tank, the overheating section coil pipe and the phase change section coil pipe are respectively connected with an external steam pocket, and electric heating rods are arranged on the periphery in the heat accumulator. Solid molten salt is rapidly heated and melted through an electric heating rod, high-energy-density heat storage is achieved in combination with a heat storage body, and it is ensured that the system has the long-time and large-capacity heat storage capacity; in the heat release process, feed water is heated into superheated steam by arranging a phase change section coil pipe and an overheating section coil pipe in the fused salt storage tank, phase change latent heat of fused salt is fully utilized, steam is continuously generated through the coil pipe heat exchanger, stable heat energy is output, and industrial or power generation requirements are met. The phase change modular heat storage device has the advantages of being compact in structure, low in cost, high in energy storage density and high in flexibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of molten salt energy storage, and in particular relates to a phase-change modular molten salt energy storage device and a working method thereof. Background Art

[0002] In today's energy sector, energy storage technology, as a key link in balancing energy supply and demand and improving energy efficiency, is receiving increasing attention. Molten salt energy storage technology, with its unique advantages such as high-temperature stability, relatively high energy storage density, and environmental friendliness, has shown broad application prospects in areas such as solar thermal power generation and industrial waste heat recovery. However, existing molten salt energy storage solutions face numerous challenges in practical application, particularly in the comprehensive utilization of molten salt's latent and sensible heat. This, to a certain extent, has hindered the further development and large-scale promotion of molten salt energy storage technology.

[0003] In traditional molten salt energy storage systems, it's often difficult to balance the latent and sensible heat of the molten salt. The sensible heat of the molten salt refers to the heat absorbed or released during temperature changes, while the latent heat is the heat absorbed or released during phase changes (such as from solid to liquid or vice versa). Traditional designs typically focus on utilizing the sensible heat of the molten salt, heating it to increase its temperature to store energy and then cooling it down when the energy is needed. While this energy storage method is simple and straightforward, it has significant limitations.

[0004] On the one hand, due to insufficient utilization of latent heat, traditional solutions require the use of large amounts of molten salt to meet the same heat storage requirements. This large amount of molten salt not only increases the size and weight of the energy storage device, but also significantly increases the cost of the device. The procurement, storage, transportation, construction, and maintenance of the molten salt require significant capital investment, making molten salt energy storage technology uncompetitive economically and difficult to widely adopt in the energy market.

[0005] On the other hand, traditional molten salt energy storage systems require the molten salt to remain liquid throughout operation through insulation or electrical heating. Furthermore, if the system is not used for an extended period, the salt must be drained and then recharged and dissolved before the next use, increasing operating costs. To overcome the shortcomings of traditional molten salt energy storage solutions, modular molten salt energy storage systems have emerged. This new type of energy storage system, through its unique design and technological innovations, efficiently utilizes the phase change heat of the molten salt, offering significant advantages in multiple areas. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a phase-change modular molten salt energy storage device and a working method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a phase-change modular molten salt energy storage device, comprising a heat storage body, a molten salt storage tank arranged inside the heat storage body, the molten salt storage tank comprising a molten salt inlet pipe, a spiral coil arranged inside the molten salt storage tank, the spiral coil comprising an overheating section coil and a phase change section coil, the overheating section coil and the phase change section coil are respectively connected to an external steam drum, and electric heating rods are arranged around the inside of the heat storage body.

[0008] The superheating section coil is located above the interior of the molten salt storage tank, and the phase change section coil is located below the interior of the molten salt storage tank.

[0009] A plurality of coil supports are vertically arranged on the outside of the spiral coil.

[0010] Partitions are horizontally arranged inside the molten salt storage tank to divide the molten salt storage tank into different spaces through the partitions.

[0011] The heat storage body is made of heat storage material, preferably graphite solid material.

[0012] The molten salt inlet pipe is provided with a molten salt inlet valve.

[0013] The external steam drum is connected with a circulation pump.

[0014] The superheating section coil comprises a superheating section coil inlet and a superheating section coil outlet.

[0015] The phase change section coil comprises a phase change section coil inlet and a phase change section coil outlet.

[0016] In the second aspect, the present invention provides a working method of a phase-change modular molten salt energy storage device, wherein molten salt is added to the molten salt storage tank through a molten salt inlet pipe; when storing heat, the electric heating rod is started to heat and melt the solid molten salt in the molten salt storage tank; when releasing heat, feed water enters an external steam drum, and the feed water enters the phase change section coil through a circulating pump. After absorbing heat, the feed water becomes unsaturated steam and enters the external steam drum. After steam-water separation in the external steam drum, the saturated steam enters the superheating section coil to absorb heat. After the saturated steam becomes superheated steam, it is sent out through the superheating section coil outlet for use.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a phase-change modular molten salt energy storage device, comprising a thermal accumulator, a molten salt storage tank disposed within the thermal accumulator, the molten salt storage tank including a molten salt inlet pipe, a spiral coil disposed within the molten salt storage tank, the spiral coil including an overheating section coil and a phase change section coil, the overheating section coil and the phase change section coil being respectively connected to an external steam drum, and electric heating rods disposed around the thermal accumulator. During operation, molten salt is added to the molten salt storage tank through the molten salt inlet pipe; during heat storage, the electric heating rods are activated to heat and melt the solid molten salt in the molten salt storage tank; during heat release, feed water enters the external steam drum, and the feed water enters the phase change section coil through a circulating pump. After absorbing heat, the feed water becomes unsaturated steam and enters the external steam drum. After steam-water separation in the external steam drum, saturated steam enters the superheating section coil to absorb heat. The saturated steam becomes superheated steam and is then delivered through the outlet of the superheating section coil for use. The solid molten salt is quickly heated and melted by an electric heating rod, and high-energy-density heat storage is achieved in combination with a heat storage body, ensuring that the system has a long-term, large-capacity heat storage capacity; during the heat release process, the feed water is heated to superheated steam by arranging two parts of coils, a phase change section and a superheat section, in the molten salt storage tank. The phase change latent heat of the molten salt is fully utilized, and steam is continuously generated through the coil heat exchanger to output stable thermal energy to meet industrial or power generation needs; the phase change modular heat storage device has a compact structure. Compared with traditional molten salt energy storage devices, under the same heat storage requirements, the amount of molten salt required for the modular device is greatly reduced, which not only reduces the procurement cost of molten salt, but also reduces the footprint and weight of the device, thereby reducing the construction and maintenance costs of the device; it has the advantages of low cost, high energy storage density and high flexibility, and the constructed phase change modular heat storage system can output industrial steam.

[0018] Furthermore, during operation, the spiral coil may be affected by factors such as internal fluid pressure, temperature changes, and external mechanical forces, resulting in deformation or vibration. Several coil supports are vertically arranged on the outside of the spiral coil to provide additional support for the coil, which can effectively resist these external forces and prevent the coil from excessive deformation or severe vibration.

[0019] Furthermore, the thermal storage element uses thermal storage materials. Using these materials to store heat can reduce the capacity requirements of energy supply equipment. Thermal storage materials have high heat capacity and rapid heat charge and discharge capabilities, enabling rapid response to system load changes. In a power system, when the power load suddenly increases, the thermal storage element can quickly release heat, driving the power generation equipment to increase output to meet the load demand; when the load decreases, the excess energy can be stored. This rapid response capability improves the flexibility and reliability of the power system.

[0020] Furthermore, the modular molten salt energy storage system allows the molten salt to undergo a phase transition within the tank, eliminating the need for a salt draining process. Upon use, the electric heating rods are instantly activated to melt the molten salt, saving operating costs. By optimizing the design and operating strategy, this system significantly reduces energy storage costs and offers greater flexibility and scalability. Each module can be operated and controlled independently, allowing for combination and adjustment based on actual needs. This not only improves the system's operating efficiency but also enhances system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of the overall structure of the device of the present invention; Figure 2 It is a perspective view of the overall structure of the device of the present invention; Figure 3 Schematic diagram of the working method of the present invention; Explanation of the reference numerals in the figure: 1. Molten salt storage tank; 2. Electric heating rod; 3. Phase change section coil inlet; 4. Phase change section coil outlet; 5. Superheat section coil inlet; 6. Superheat section coil outlet; 7. Superheat section coil; 8. Coil bracket; 9. Heat storage body; 10. Phase change section coil; 11. Partition; 12. Molten salt inlet valve; 13. External steam drum; 14. Circulation pump. DETAILED DESCRIPTION

[0023] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be considered as illustrative in nature and not restrictive.

[0024] 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", "axial", "radial", "circumferential" and the like to 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, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0026] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0028] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0029] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0030] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0031] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] Example 1 A phase-change modular molten salt energy storage device, the structure of which is as follows: like Figures 1-3 As shown, a phase-change modular molten salt energy storage device includes a heat storage body 9, a molten salt storage tank 1 is arranged inside the heat storage body 9, and a spiral coil is arranged inside the molten salt storage tank 1. The spiral coil includes an overheating section coil 7 and a phase change section coil 10. The superheating section coil 7 is located above the inside of the molten salt storage tank 1, and the phase change section coil 10 is located below the inside of the molten salt storage tank 1. The superheating section coil 7 and the phase change section coil 10 are respectively connected to an external steam drum 13, the superheating section coil 7 includes a superheating section coil inlet 5 and a superheating section coil outlet 6, and the phase change section coil 10 includes a phase change section coil inlet 3 and a phase change section coil outlet 4; a plurality of coil supports 8 are vertically arranged on the outside of the spiral coil, and two partitions 11 are horizontally arranged inside the molten salt storage tank 1, and the molten salt storage tank 1 is divided into three spaces by the partition 11. Each of the three spaces of the molten salt storage tank 1 has a molten salt inlet pipe for adding molten salt. Electric heating rods 2 are arranged around the molten salt storage tank 1, that is, inside the heat storage body 9.

[0034] Preferably, the heat storage body 9 is a graphite heat storage material, but other heat storage materials can also be used. Heat storage materials can absorb and store energy and release it when needed, effectively solving the problem of mismatch between energy supply and demand in time and space.

[0035] Preferably, the molten salt inlet pipe is provided with a molten salt inlet valve 12. The molten salt inlet valve 12 controls the amount of salt entering, thereby adjusting the heat storage capacity of the modular device as a whole.

[0036] Preferably, the external steam drum 13 is connected to a circulating pump 14, which regulates the feedwater flow rate to accommodate varying load requirements. Steam-water separation is required within the steam drum to separate the steam and water. The circulating pump 14 delivers the working fluid from the phase change coil 10 into the external steam drum 13. By adjusting the flow rate and pressure, the circulating pump 14 controls the parameters of the working fluid entering the phase change coil 10, ensuring that the steam-water mixture enters the drum at an appropriate rate and in a suitable manner, improving its flow.

[0037] Preferably, partitions 11 are placed at intervals from the bottom of the molten salt storage tank 1 to separate the molten salt. Two partitions are present, dividing the molten salt into three small compartments and supporting the superheating coil 7 and phase change coil 10. The molten salt fills these small compartments in its liquid state, but its volume decreases in solid form, leaving gaps. This reduces the risk of damage to the equipment caused by volume changes during the molten salt phase transition.

[0038] As a preferred embodiment of this example, the size selection and thermodynamic performance parameters of a phase-change modular molten salt energy storage device are given. The structural parameters of the device are shown in Table 1 below.

[0039] Table 1 Size selection

[0040] Preferably, the thermodynamic performance parameters of the phase change modular device are given in Table 2 below: Table 2 Thermodynamic performance parameters

[0041] Example 2 A phase-change modular molten salt energy storage device, the working method of which is as follows: like Figure 3 As shown, molten salt is injected into the three-layer molten salt storage tank 1 separated by partitions 11 through three independent molten salt inlet pipes. After the molten salt is added, the molten salt inlet valve 12 is closed. During heat storage, the electric heating rod 2 is activated to melt the solid molten salt in the molten salt storage tank 1 and raise the temperature to 560°C. During heat release, the feed water enters the external steam drum 13 and is delivered by the circulating pump 14 through the phase change section coil inlet 3 to the phase change section coil 10. The saturated water working medium (feed water) absorbs heat and becomes unsaturated steam, which enters the external steam drum 13 through the phase change section coil outlet 4. After steam and water separation in the external steam drum 13, the saturated steam enters the superheat section coil 7 through the superheat section coil inlet 5 to absorb heat. The saturated steam becomes superheated steam and is then delivered for use through the superheat section coil outlet 6. At the same time, the molten salt releases heat and cools down until it solidifies.

[0042] Preferably, the device allows the molten salt to undergo phase change and solidify in the storage tank. When storing heat again, the molten salt only needs to be heated again by the heating electrode. There is no need to continuously heat the molten salt to keep it in liquid state, thus saving operating costs.

[0043] The emergence of modular molten salt energy storage devices has brought new opportunities for the development of molten salt energy storage technology. With continued technological advancements and further cost reductions, modular molten salt energy storage devices are expected to be widely used in areas such as solar thermal power generation, industrial waste heat recovery, and distributed energy systems. In the field of solar thermal power generation, they can improve the efficiency and stability of power plants, solving the problems of intermittent and fluctuating solar energy. In industrial waste heat recovery, they can effectively recover and utilize the large amount of waste heat generated during industrial production, reducing energy consumption and production costs for enterprises. In distributed energy systems, they can serve as energy storage units, achieving optimal energy allocation and efficient utilization, and can be used for frequency regulation of thermal power units.

[0044] Finally, it should be noted that the above embodiments merely illustrate the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description. It is intended that all variations within the meaning and range of equivalents of the claims be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claim to which they relate.

[0045] In addition, it should be understood that although this specification describes the embodiments, not every embodiment contains only one independent technical solution. This description is for clarity only. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for the purpose of illustrating the technical concept of the present invention and cannot be used to limit the scope of protection of the present invention. Any changes made based on the technical solution in accordance with the technical concept proposed by the present invention fall within the scope of protection of the claims of the present invention.

Claims

1. A phase-change modular molten salt energy storage device, characterized in that: The invention comprises a heat accumulator (9), a molten salt storage tank (1) is arranged inside the heat accumulator (9), the molten salt storage tank (1) comprises a molten salt inlet pipe, a spiral coil is arranged inside the molten salt storage tank (1), the spiral coil comprises an overheating section coil (7) and a phase change section coil (10), the overheating section coil (7) and the phase change section coil (10) are respectively connected to an external steam drum (13), and electric heating rods (2) are arranged around the inside of the heat accumulator (9).

2. A phase-change modular molten salt energy storage device according to claim 1, characterized in that: The superheating section coil (7) is located above the interior of the molten salt storage tank (1), and the phase change section coil (10) is located below the interior of the molten salt storage tank (1).

3. A phase-change modular molten salt energy storage device according to claim 1, characterized in that: A plurality of coil supports (8) are vertically arranged on the outside of the spiral coil.

4. A phase-change modular molten salt energy storage device according to claim 1, characterized in that: A partition (11) is horizontally arranged inside the molten salt storage tank (1), and the partition (11) divides the molten salt storage tank (1) into different spaces.

5. The phase-change modular molten salt energy storage device according to claim 1, characterized in that: The heat storage body (9) is made of heat storage material.

6. The phase-change modular molten salt energy storage device according to claim 1, characterized in that: The molten salt inlet pipe is provided with a molten salt inlet valve (12).

7. The phase-change modular molten salt energy storage device according to claim 1, characterized in that: The external steam drum (13) is connected to a circulation pump (14).

8. The phase-change modular molten salt energy storage device according to claim 1, characterized in that: The superheating section coil (7) comprises a superheating section coil inlet (5) and a superheating section coil outlet (6).

9. The phase-change modular molten salt energy storage device according to claim 1, characterized in that: The phase change section coil (10) comprises a phase change section coil inlet (3) and a phase change section coil outlet (4).

10. The operating method of a phase-change modular molten salt energy storage device according to any one of claims 1 to 9, characterized in that: Molten salt is added to the molten salt storage tank (1) through the molten salt inlet pipe; when storing heat, the electric heating rod (2) is started to heat and melt the solid molten salt in the molten salt storage tank (1); when releasing heat, feed water enters the external steam drum (13), and the feed water enters the phase change section coil (10) through the circulation pump (14). After absorbing heat, the feed water becomes unsaturated steam and enters the external steam drum (13). After steam and water are separated in the external steam drum (13), the saturated steam enters the superheating section coil (7) to absorb heat, and the saturated steam becomes superheated steam and is sent out through the superheating section coil outlet (6) for use.

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