Forced convection single-tank fused salt-solid energy storage device

Abstract

The invention discloses a forced convection single-tank fused salt-solid energy storage device which comprises a heat storage tank body, and the interior of the heat storage tank body is divided into a central fused salt filling area and a peripheral mixed filling area through an annular partition plate; the mixed filling area is filled with a mixture of solid particles and fused salt, the fused salt filling area is filled with pure fused salt, and through holes used for blocking the solid particles and allowing the fused salt to pass through are formed in the partition plate; the device is further provided with a forced convection disturbance device, the forced convection disturbance device comprises a liquid collecting barrel vertically arranged in the center of the fused salt filling area, a piston and a driving piece, through holes are formed in the barrel wall of the liquid collecting barrel, the driving piece drives the piston to move in the liquid collecting barrel in a reciprocating mode, and forced circulation convection is formed in the heat storage tank body by sucking and discharging fused salt. Temperature stratification in the tank is broken through forced convection, the temperature uniformity and the heat exchange efficiency in the heat charging and discharging process are improved, local overtemperature or solidification is effectively avoided, and the overall operation safety and economical efficiency of the energy storage system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid energy storage technology, and particularly relates to a forced convection single-tank molten salt-solid energy storage device. BACKGROUND

[0002] Molten salt energy storage is widely used in the field of solar thermal power generation, and the mainstream scheme adopts a double-tank molten salt heat storage system, which uses binary or ternary molten salt as a heat storage medium. However, the double-tank system has problems of large storage tank volume and high cost, and the technical scheme of single-tank molten salt-solid hybrid energy storage can reduce the energy storage cost and has significant advantages, but still faces many challenges.

[0003] Among them, the problem of single-tank thermocline is particularly important: after large-capacity design of molten salt energy storage, the temperature difference between the upper and lower layers of the storage tank is large, the temperature of the upper layer is too high, and the temperature of the lower layer is low, which can easily cause local overheating or condensation to affect heat transfer. At present, there is a design scheme of designing a stirring pump at the top of the storage tank, but such a long-axis pump can only stir the molten salt in the height area of the impeller during use, and cannot fully stir the molten salt in each layer of the tank. After being applied to the heat storage mode of solid + molten salt, due to the blockage of the solid, the stirring power may not be sufficient to fully mix the molten salt in the tank.

[0004] Therefore, there is an urgent need for an energy storage device that can realize axial forced convection in the tank, enhance overall mixing, and enhance temperature uniformity. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a forced convection single-tank molten salt-solid energy storage device, which solves the problem that the temperature difference between the upper and lower layers of the storage tank is large in the prior art, and the stirring method of the prior art cannot uniformly adjust the temperature in the storage tank.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A forced convection single-tank molten salt-solid energy storage device, comprising a heat storage tank body and a molten salt electric heater, the inside of the heat storage tank body is provided with a partition plate, the partition plate divides the internal space of the heat storage tank body into a mixed filling area in the periphery and a molten salt filling area in the center; the mixed filling area is filled with a mixture of solid particles and molten salt, and the molten salt filling area is filled with molten salt; the partition plate is provided with through holes for blocking the solid particles and allowing the molten salt to pass through; further comprising a forced convection disturbance device, the forced convection disturbance device is installed in the molten salt filling area and comprises a liquid collecting cylinder, a piston and a driving member; the cylinder wall of the liquid collecting cylinder is also provided with through holes, the piston is driven to reciprocate in the liquid collecting cylinder by the driving member to suck the molten salt into the liquid collecting cylinder or discharge the molten salt out of the liquid collecting cylinder, so as to form a convection in the heat storage tank body.

[0008] Through the above settings, the partition plate is used to divide the pure molten salt area and the mixed filling area in the single tank, which not only retains the fluidity of the molten salt, but also improves the heat storage density and structural stability through the solid particles; the forced convection disturbance device drives the molten salt to form a circulating flow in the tank through the reciprocating movement of the piston in the collecting cylinder with a through hole, effectively breaks the temperature stratification caused by the density difference, realizes the temperature homogenization of the whole tank, and improves the heat exchange efficiency and system operation reliability.

[0009] Further, the driving member includes a transmission motor and a telescopic connecting rod; the collecting cylinder is vertically arranged at the center of the molten salt filling area, the transmission motor is located above the center of the collecting cylinder, one end of the telescopic connecting rod is in transmission connection with the transmission motor, and the other end extends into the inside of the collecting cylinder; the piston is arranged at the bottom of the telescopic connecting rod and moves in the collecting cylinder with the telescopic connecting rod to drive the molten salt to flow.

[0010] Through the above settings, the collecting cylinder and the transmission motor are vertically arranged to drive the piston through the telescopic connecting rod, which is compact in structure and stable in transmission, can realize the precise up-down movement of the piston in the collecting cylinder, and thus reliably form the suction and discharge actions of the molten salt, and realize the controllable forced convection.

[0011] Further, the collecting cylinder includes a flow guide plate at the top, a solid cylinder segment at the upper part, and a porous cylinder segment at the middle and lower part, and the porous cylinder segment is provided with a through hole; the bottom of the collecting cylinder is located at the bottom of the tank cylinder, and the top of the collecting cylinder is higher than the filling height of the molten salt filling area.

[0012] Through the above settings, the collecting cylinder adopts a segmented structure of solid at the top and porous at the middle and lower part, and cooperates with the top flow guide plate to guide the flow of the molten salt; the solid cylinder wall and the flow guide plate at the middle and upper part are used when the telescopic connecting rod is pulled upward so that the molten salt passes above the solid filler, and a better convection enhancement effect is achieved.

[0013] Further, the flow guide plate is in an annular outward turning structure, and the outer edge of the flow guide plate is located above the mixed filling area, and the molten salt flowing down from the flow guide plate falls into the mixed filling area outside the partition plate.

[0014] Through the above settings, the flow guide plate adopts an annular outward turning structure and extends above the mixed filling area, so that the molten salt flowing out of the top of the collecting cylinder can directly fall into the peripheral mixed filling area, promoting the exchange of molten salt and heat transfer between the two areas, and enhancing the overall temperature uniformity.

[0015] Further, the hole diameter of the through hole on the partition plate is smaller than the minimum particle size of the solid particles.

[0016] Through the above settings, the partition plate and the through hole of the collecting cylinder can effectively block the solid particles from entering the inside of the partition plate and the collecting cylinder, prevent the equipment from being blocked, and also ensure the smooth flow of the molten salt and maintain the convection effect.

[0017] Furthermore, it also includes heat exchange tubes, which are disposed between the inner side of the partition and the forced convection disturbance device.

[0018] With the above setup, heat exchange tubes are installed in the molten salt filling area, allowing for efficient heat exchange by directly utilizing the molten salt flow enhanced by forced convection, thereby improving heat release power and speed.

[0019] Furthermore, the heat storage tank is equipped with multiple temperature sensors.

[0020] With the above setup, multiple temperature sensors are arranged inside the tank to monitor the temperature distribution at different heights and radial positions in real time, providing feedback for the control of the forced convection disturbance device and the heater, thus achieving precise temperature control.

[0021] Furthermore, the molten salt electric heater is inserted into the mixing and filling area, and several molten salt electric heaters are evenly arranged around the circumference of the heat storage tank.

[0022] With the above settings, multiple molten salt electric heaters are evenly inserted into the mixing and filling area and controlled independently. The heating power can be adjusted according to the temperature distribution, thereby improving the charging efficiency and safety.

[0023] Furthermore, the telescopic linkage is a worm gear structure, which achieves telescopic movement through meshing with the gears of the drive motor.

[0024] With the above settings, the telescopic linkage adopts a worm gear transmission structure, which provides smooth transmission, good self-locking, and precise displacement control of the piston, adapting to frequent start-stop and speed change operations.

[0025] Furthermore, a pressure sensor is provided at the bottom of the piston.

[0026] With the above settings, a pressure sensor is installed at the bottom of the piston to monitor the piston's movement resistance in real time. In case of blockage or abnormality, the system can be shut down in time for protection, thereby improving the safety and maintainability of the system operation.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This solution applies the molten salt-solid energy storage method to a single-tank thermal storage system. The forced convection disturbance device can replace the traditional stirring equipment to achieve forced convection within the single tank, realizing the flow and temperature mixing of the molten salt, avoiding local overheating or solidification caused by insufficient heat exchange during natural convection of the molten salt; it improves the temperature uniformity during heat charging and releasing, on the one hand, avoiding overheating of the electric heater tube surface during heat charging and improving heat charging efficiency; on the other hand, it increases the convective heat transfer coefficient during heat exchange, enhances heat release efficiency, and increases the overall energy storage utilization rate. Attached Figure Description

[0029] Figure 1This is a schematic diagram of the overall structure in this embodiment of the solution;

[0030] Figure 2 This is a top cross-sectional view of the device in this embodiment;

[0031] Figure 3 A schematic diagram of molten salt flow during the retraction of the telescopic linkage controlled by the drive motor;

[0032] Figure 4 A schematic diagram of molten salt flow during the extension of the telescopic linkage controlled by the drive motor;

[0033] Figure 5 for Figure 1 Enlarged view of point A in the middle.

[0034] The reference numerals in the accompanying drawings include:

[0035] 1. Thermal storage tank; 2. Molten salt electric heater; 3. Heat exchange tube; 4. Baffle; 5. Molten salt filling area; 6. Mixing filling area; 9. Reinforcing steel; 10. Top flange; 11. Liquid collection cylinder; 12. Piston; 13. Drive motor; 14. Telescopic connecting rod; 15. Baffle plate; 16. Solid cylinder section; 17. Perforated cylinder section; 18. Gear. Detailed Implementation

[0036] The present invention will now be described in detail through specific embodiments:

[0037] A forced convection single-tank molten salt-solid energy storage device, such as Figure 1 and Figure 2 As shown, it includes a thermal storage tank 1, a molten salt electric heater 2, a heat exchange tube 3, and a forced convection disturbance device.

[0038] The heat storage tank 1 is a vertical container, which is cylindrical in this embodiment. An annular partition 4 is provided inside the heat storage tank 1. The partition 4 divides the internal space of the heat storage tank 1 into a central molten salt filling area 5 and an outer mixed filling area 6.

[0039] The mixed-fill region 6 is located outside the partition 4, and is filled with a mixture of solid particles and molten salt. The gaps between the solid particles are filled with molten salt. This design can significantly reduce the amount of pure molten salt used, thereby reducing costs, while the solid particles provide structural support and enhance the thermal storage density.

[0040] The molten salt filling area 5 is located inside the partition 4. This area is a pure molten salt medium area. A forced convection disturbance device is arranged in the center of the molten salt filling area 5.

[0041] The partition 4 is a porous plate, and the diameter of the through holes on the partition 4 is smaller than the minimum particle size of the solid particles, so as to prevent solid particles in the mixed filling area 6 from entering the lava filling area.

[0042] The molten salt electric heaters are of an insertion type. Multiple sets of molten salt electric heaters 2 are evenly distributed around the circumference of the heat storage tank 1 and inserted into the mixing and filling area 6, that is, into the heat storage medium in which solid particles and molten salt are mixed. They are fixed by the top flange 10 located above the top cover of the heat storage tank 1. During heat storage, the power of the molten salt electric heaters 2 is gradually increased to gradually raise the temperature of the heat storage medium in which solid particles and molten salt are mixed. In this embodiment, four sets of molten salt electric heaters 2 are configured. The four sets of molten salt electric heaters 2 adopt a regional independent control strategy. Based on the temperature feedback from the temperature sensors in different areas of the heat storage tank 1, the heating power of each group in each area is adjusted to achieve uniform and gradual heat storage temperature rise.

[0043] Multiple temperature sensors are arranged along the height and radial directions inside the thermal storage tank 1. In this embodiment, the temperature sensors are configured as "multi-point thermocouples", that is, the multi-point thermocouples are inserted vertically in the mixing and filling area 6 inside the storage tank, and multiple temperature detection points are set in the vertical direction to measure the temperature at various points in the mixing and filling area 6. Multiple temperature sensors are evenly arranged in the mixing and filling area 6.

[0044] The forced convection disturbance device is located at the center of the molten salt filling area 5, i.e., at the center of the thermal storage tank 1. This device is used to break up temperature stratification and achieve uniform heat exchange. The forced convection disturbance device includes a cylindrical liquid collection cylinder 11, a piston 12, and a drive component. The drive component includes a drive motor 13 and a telescopic connecting rod 14. The drive motor 13 is mounted above the top of the thermal storage tank 1, while the telescopic connecting rod 14 and the piston 12 are located inside the liquid collection cylinder 11.

[0045] The liquid collecting cylinder 11 is vertically installed at the center of the molten salt filling area 5 and coaxial with the heat storage tank 1. The liquid collecting cylinder 11 consists of three parts: a guide plate 15 at the top, a solid cylindrical section 16 at the top, and a porous cylindrical section 17 at the middle and lower parts. The guide plate 15 is configured with an annular outward-curving structure. The guide plate 15, the solid cylindrical section 16, and the porous cylindrical section 17 are coaxial and welded together. The bottom of the liquid collecting cylinder 11 is located at the bottom of the tank body, and the top of the liquid collecting cylinder 11 is higher than the filling height of the molten salt filling area 5.

[0046] Through holes are uniformly provided on the wall of the porous section 17 of the liquid collecting cylinder 11. The shape of the through holes in the liquid collecting cylinder 11 can be various, such as circular, square, or triangular. In this embodiment, circular through holes are preferred to reduce the risk of solid particles clogging the cylinder. The diameter of the through holes on the liquid collecting cylinder 11 needs to be smaller than the diameter of the through holes on the partition plate 4 to reduce the probability of broken solid particles entering the liquid collecting cylinder 11. Preferably, the shape of the through holes on the liquid collecting cylinder 11 is consistent with that of the through holes on the partition plate 4, and the diameter of the through holes on the liquid collecting cylinder 11 is less than half the diameter of the solid particles.

[0047] The telescopic connecting rod 14 is a worm gear structure, with one end engaging with the drive motor 13 for transmission, and the other end extending into the liquid collecting cylinder 11. For example... Figure 5 As shown, the telescopic link 14 is driven by meshing with the gear 18 of the drive motor 13, thereby driving the telescopic link 14 to extend or retract, i.e., to pull the telescopic link 14 upward or extend it downward. The drive motor 13 is preferably a variable frequency motor, which is arranged in the middle of the top of the thermal storage tank 1. Through temperature feedback from the temperature sensor inside the thermal storage tank 1, the frequency of the drive motor 13 can be adjusted to control the extension and retraction rate of the telescopic link 14, thereby achieving the purpose of controlling and regulating the temperature inside the thermal storage tank 1.

[0048] Piston 12 is installed inside the collecting cylinder 11 and is located at the bottom of the telescopic connecting rod 14. The reciprocating movement of piston 12 is achieved by extending and retracting the telescopic connecting rod 14. The movement of piston 12 transports the heat medium, which is molten salt, thereby achieving radial transfer and mixing of the molten salt. In this embodiment, the piston 12 adopts a design combining a frustum and a cylinder, which facilitates the flow of molten salt from the through-hole of the collecting cylinder 11 during piston 12 movement, preventing molten salt blockage.

[0049] The forced convection disturbance device can be fixed by welding the guide plate 15 to the top of the upper heat storage tank 1, or by welding the bottom of the liquid collecting cylinder 11 to the bottom plate of the heat storage tank 1, or by welding both methods simultaneously. Preferably, the guide plate 15 is welded to the top of the upper heat storage tank 1, specifically configured such that the guide plate 15 and the top cover of the heat storage tank 1 are connected by a steel bar 9 or a flat iron.

[0050] When solid particles break down and deposit at the bottom of the liquid collection cylinder 11, and the resistance to the piston 12 increases or it cannot fully extend, a pressure sensor is installed at the bottom of the telescopic connecting rod 14. Through force feedback, the drive motor 13 is controlled to stop running, so that the device can be shut down for maintenance and cleaning.

[0051] Heat exchange tubes 3 are installed inside the partition 4 and between the forced convection disturbance device. When water flows through the heat exchange tubes, it enters from one side of the tubes, absorbs the heat stored in the molten salt, and then turns into steam to provide energy for users. Gas can also be passed through the heat exchange tubes for heat exchange in building heating, food drying, etc., or heat transfer oil can be passed through them for constant temperature control processes in food, pharmaceutical, metallurgy, chemical, and new energy industries. The heat exchange tubes 3 are arranged around the forced convection disturbance device and can be either serpentine or spiral-wound tubes. They are fixed between the forced convection disturbance device and the partition 4 by welding, with spiral-wound tubes being preferred to achieve uniform and sufficient heat exchange. The selection of structural parameters such as heat exchange area and tube diameter needs to be determined based on the heat storage capacity, heat exchange power, and heat exchange parameters.

[0052] In this scheme, the movement of piston 12 is controlled by the extension and retraction of telescopic link 14, thereby creating forced convection disturbance in the heat storage tank 1.

[0053] The steps to form a forced convection disturbance are as follows:

[0054] When the drive motor 13 controls the telescopic connecting rod 14 to retract, and the piston 12 moves upward from the lower part of the liquid collecting cylinder 11, as... Figure 3 As shown, the molten salt stored in the original collecting cylinder 11 is drawn upward and flows through the top guide plate 15 to diffuse in all directions. The guide plate 15 covers the molten salt filling area 5, and the outer edge of the guide plate 15 is located above the mixing filling area 6. The molten salt flowing down from the guide plate 15 falls into the mixing filling area 6 outside the partition plate 4 and flows downward from the top of the mixing filling area 6. Meanwhile, the molten salt in the original mixing filling area 6 will flow into the collecting cylinder 11 through the through hole on the cylinder wall of the collecting cylinder 11 that has been emptied by the piston 12 to replenish the molten salt, forming a forced circulation flow.

[0055] When the drive motor 13 controls the extension of the telescopic connecting rod 14, and the piston 12 moves downward from the upper part of the liquid collecting cylinder 11, as... Figure 4 As shown, the molten salt originally stored in the collecting cylinder 11 is squeezed and ejected through the through hole of the collecting cylinder 11 to form a jet, increasing the flow of molten salt in the heat storage tank 1. The squeezed-out molten salt encounters the obstruction of the tube wall at the bottom of the heat storage tank 1 and flows upward along the wall. Meanwhile, the molten salt originally mixed and filled in the mixing area 6 flows into the collecting cylinder 11 through the through hole located above the piston 12 to replenish the molten salt, forming a forced circulation flow.

[0056] In this repeated process, a forced convection circulation with opposite flow directions is formed inside the heat storage tank 1. On the one hand, this breaks the natural stratification caused by the density difference of the molten salt itself, increasing the overall utilization rate of the molten salt. On the other hand, it enhances the flow intensity inside the heat storage tank 1, and the convective heat transfer on the surface of the heat exchange tube 3 increases the operating temperature range of the molten salt when releasing heat. It also helps to control the temperature on the surface of the molten salt electric heater 2, preventing the heating tube of the molten salt electric heater 2 from overheating and bursting, and preventing the molten salt near the tube surface from overheating and decomposing.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A forced convection single-tank molten salt-solid energy storage device, comprising a heat storage tank (1) and a molten salt electric heater (2), characterized in that, The heat storage tank (1) is provided with a partition (4) inside, which divides the internal space of the heat storage tank (1) into an outer mixed filling area (6) and a central molten salt filling area (5); the mixed filling area (6) is filled with a mixture of solid particles and molten salt, and the molten salt filling area (5) is filled with molten salt; the partition (4) is provided with through holes for blocking solid particles and allowing molten salt to pass through; It also includes a forced convection disturbance device, which is installed in the molten salt filling area (5) and includes a collection cylinder (11), a piston (12) and a driving component; the cylinder wall of the collection cylinder (11) is also provided with a through hole, and the piston (12) is driven by the driving component to move back and forth in the collection cylinder (11) to draw molten salt into the collection cylinder (11) or discharge it out of the collection cylinder (11) so as to form convection in the heat storage tank (1).

2. The forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, The driving component includes a drive motor (13) and a telescopic connecting rod (14); the liquid collecting cylinder (11) is vertically arranged at the center of the molten salt filling area (5), the drive motor (13) is located above the center of the liquid collecting cylinder (11), one end of the telescopic connecting rod (14) is connected to the drive motor (13) and the other end extends into the liquid collecting cylinder (11); the piston (12) is located at the bottom of the telescopic connecting rod (14) and moves in the liquid collecting cylinder (11) with the extension and retraction of the telescopic connecting rod (14) to drive the molten salt to flow.

3. A forced convection single-tank molten salt-solid energy storage device according to claim 1 or 2, characterized in that, The liquid collecting cylinder (11) includes a top guide plate (15), an upper solid cylinder section (16), and a middle and lower porous cylinder section (17), with through holes provided on the porous cylinder section (17); the bottom of the liquid collecting cylinder (11) is located at the bottom of the storage tank body, and the top of the liquid collecting cylinder (11) is higher than the filling height of the molten salt filling area (5).

4. A forced convection single-tank molten salt-solid energy storage device according to claim 3, characterized in that, The guide plate (15) is an annular outward-turned structure. The outer edge of the guide plate (15) is located above the mixing and filling area (6). Molten salt flowing down from the guide plate (15) falls into the mixing and filling area (6) outside the partition plate (4).

5. A forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, The diameter of the through holes on the partition (4) is smaller than the minimum particle size of the solid particles.

6. A forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, It also includes a heat exchange tube (3), which is disposed inside the partition plate (4) and between the forced convection disturbance device.

7. A forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, The heat storage tank (1) is equipped with multiple temperature sensors.

8. A forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, The molten salt electric heater (2) is inserted into the mixing and filling area (6), and several molten salt electric heaters (2) are evenly arranged around the heat storage tank (1).

9. A forced convection single-tank molten salt-solid energy storage device according to claim 2, characterized in that, The telescopic link (14) is a worm gear structure, which meshes with the gear (18) of the drive motor (13) to achieve telescopic movement.

10. A forced convection single-tank molten salt-solid energy storage device according to claim 1, characterized in that, A pressure sensor is provided at the bottom of the piston (12).

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