Solid-liquid two-phase thermal energy storage system and working method thereof

Abstract

The present application discloses a solid-liquid two-phase thermal energy storage system and a working method thereof. The outlet of a liquid storage module splits into two paths: one path is communicated with a liquid inlet of a high-efficiency heat exchanger module via a second control valve, and the other path is communicated with the inlet of an electric heater via a first control valve. The outlet of the electric heater splits into two paths: one path is communicated with the liquid inlet of the high-efficiency heat exchanger module via a third control valve, and the other path is communicated with the inlet of a flow distribution module via a fourth control vale. A liquid outlet of the high-efficiency heat exchanger module is communicated with the inlet of the flow distribution module; the outlet of the flow distribution module is communicated with a liquid inlet of the uppermost solid heat storage module; overflow holes of each solid heat storage module are communicated with a liquid inlet of an adjacent solid heat storage module below said solid heat storage module; and overflow holes of the lowermost solid heat storage module are communicated with the inlet of the liquid storage module. The system and the working method thereof have the characteristics of reliable operation, small footprint, low investment and flexible assembly.

Description

A solid-liquid two-phase thermal storage system and its working method

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410485816.1, filed on April 22, 2024, entitled "A Solid-Liquid Two-Phase Thermal Storage System and Its Working Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of energy storage technology and relates to a solid-liquid two-phase thermal storage system and its working method. Background Technology

[0004] New energy power generation is characterized by randomness, intermittency, and high volatility. With the large-scale integration of new energy into the grid, it poses a severe challenge to the safe operation of the power grid. To absorb the increasing amount of new energy, thermal power generation has undergone continuous flexibility upgrades in recent years, and its inherent regulation potential has now been exhausted. Energy storage can further improve the power load regulation capacity on the existing basis, absorbing more new energy power.

[0005] Currently, large-scale energy storage methods mainly include battery energy storage, pumped hydro storage, compressed air energy storage, and thermal energy storage. Among these, thermal energy storage has significant advantages in terms of storage capacity, unit construction cost, and application scenarios, especially in coupled thermal power generation systems. Molten salt thermal energy storage technology accounts for a large proportion of the thermal energy storage field, mainly in single / double tank mode. Although single / double tank thermal energy storage technology is relatively mature, it also has problems such as large footprint, high investment cost, and large molten salt consumption. Therefore, there is a need for a unit-type thermal energy storage system that is reliable in operation, occupies less space, requires less investment, and is flexible in assembly.

[0006] Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solid-liquid two-phase thermal energy storage system and its operating method. This system and its operating method are characterized by reliable operation, small footprint, low investment, and flexible assembly.

[0008] To achieve the above objectives, this application discloses a solid-liquid two-phase thermal storage system, including a high-efficiency heat exchanger module, a flow equalization module, a liquid storage module, a first control valve, a second control valve, an electric heater, a third control valve, a fourth control valve, and several solid thermal storage modules.

[0009] The high-efficiency heat exchanger module, flow equalization module, various solid heat storage modules, and liquid storage module are arranged sequentially from top to bottom. The outlet of the liquid storage module is divided into two paths via a pump box and a pump outlet. One path is connected to the liquid inlet of the high-efficiency heat exchanger module via a second control valve, and the other path is connected to the inlet of the electric heater via a first control valve. The outlet of the electric heater is divided into two paths. One path is connected to the liquid inlet of the high-efficiency heat exchanger module via a third control valve, and the other path is connected to the inlet of the flow equalization module via a fourth control valve. The liquid outlet of the high-efficiency heat exchanger module is connected to the inlet of the flow equalization module. The outlet of the flow equalization module is connected to the liquid inlet of the uppermost solid heat storage module. The overflow hole of the upper solid heat storage module is connected to the liquid inlet of the lower solid heat storage module. The overflow hole of the lowermost solid heat storage module is connected to the inlet of the liquid storage module. The solid heat storage modules are filled with solid heat storage material.

[0010] Both the liquid storage module and the solid heat storage module are equipped with auxiliary electric heaters.

[0011] The solid heat storage module is equipped with filters at both the liquid inlet and the overflow hole.

[0012] The amount of solid thermal storage material is 80% to 90% of the effective volume of the solid thermal storage module.

[0013] The solid heat storage material is a granular material with a particle size between 10 and 30 mm.

[0014] The first, second, third, and fourth control valves are all arranged vertically.

[0015] This application discloses a working method for a solid-liquid two-phase thermal storage system, including a thermal storage process, a heat release process, and a direct heating process.

[0016] The heat storage process is as follows:

[0017] The first and fourth control valves are in the open state, while the second and third control valves are in the closed state. Driven by a pump, the lower-temperature liquid thermal storage material is drawn from the liquid storage module through the pump box and sent to the electric heater. After passing through the electric heater, the liquid thermal storage material's temperature rises, becoming a high-temperature liquid thermal storage material. It then flows evenly into the uppermost solid thermal storage module through the flow equalization module, exchanging heat with the solid thermal storage material there, causing the temperature of the solid thermal storage material to gradually rise. Under the action of gravity, the liquid thermal storage material flows through the filter and overflow hole into the next layer of solid thermal storage module, thus heating the solid thermal storage material in each layer of solid thermal storage module step by step, and the temperature of the liquid thermal storage material gradually decreases until it flows back into the liquid storage module, entering the next heating cycle. The thermal storage process stops when the temperature inside all solid thermal storage modules reaches the set value.

[0018] The heat release process is as follows:

[0019] The second control valve is in the open state, while the first, fourth, and third control valves are in the closed state. Driven by the pump, the higher-temperature liquid heat storage material is drawn from the liquid storage module through the pump box and sent to the high-efficiency heat exchanger module to heat the steam-water system. After being cooled by the high-efficiency heat exchanger module, the liquid heat storage material flows into the flow equalization module. The flow equalization module evenly distributes the cooled liquid heat storage material into the solid heat storage modules, where it fully contacts and heats the solid heat storage material. The liquid heat storage material is continuously heated by each solid heat storage module, and its temperature gradually increases. The higher-temperature liquid heat storage material eventually flows into the liquid storage module for another round of heat release until it reaches the minimum allowable temperature, at which point the heat release process ends. During the heat release process, the pump output is matched with the steam-water parameters at the inlet and outlet of the high-efficiency heat exchanger module to ensure stable steam-water parameters.

[0020] The direct heating process is as follows:

[0021] The first and third control valves are in the open state, while the second and fourth control valves are in the closed state. Driven by the pump, the cooler liquid heat storage material is drawn from the liquid storage module through the pump box and sent to the electric heater. After passing through the electric heater, the liquid heat storage material enters the high-efficiency heat exchanger module to heat the steam and water. The cooled liquid heat storage material flows into the flow equalization module, which evenly distributes the cooled liquid heat storage material into the solid heat storage modules. Under the influence of gravity, the liquid heat storage material passes through each layer of solid heat storage modules and enters the liquid storage module for the next round of direct heating cycle. The end time of this process is determined according to actual needs. During the direct heating process, the pump output is matched with the power of the electric heater and the steam and water parameters at the inlet and outlet of the high-efficiency heat exchanger module to ensure stable steam and water parameters.

[0022] This application has the following beneficial effects:

[0023] The solid-liquid two-phase thermal storage system and its operating method described in this application utilize liquid-solid two-phase thermal storage materials for heat storage and release during specific operation. This fully leverages the safety, stability, and high heat capacity per unit volume of solid thermal storage materials, along with the high heat transfer coefficient of liquid thermal storage materials. These two materials are cleverly combined within a unit-based thermal storage system, with heat release achieved through an external high-efficiency heat exchanger. Furthermore, it should be noted that this application utilizes a combination of solid and liquid thermal storage materials for heat storage, effectively avoiding the drawbacks of using a single type of thermal storage material. This significantly improves the stability of the thermal storage system, reduces the cost per unit of heat storage, and minimizes the floor space required. Simultaneously, the unit-based modular design allows for greater flexibility in adapting to different thermal storage scenarios and facilitates assembly and maintenance. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the structure of this application;

[0025] Figure 2 is a schematic diagram of the internal structure of the solid thermal storage module 10.

[0026] Among them, 1 is the pump box, 2 is the pump, 3 is the first control valve, 4 is the second control valve, 5 is the electric heater, 6 is the third control valve, 7 is the fourth control valve, 8 is the high-efficiency heat exchanger module, 9 is the flow equalization module, 10 is the solid heat storage module, 11 is the auxiliary electric heater, 12 is the liquid storage module, 13 is the solid heat storage material, 14 is the filter screen, and 15 is the overflow hole. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present application, not all of them, and are not intended to limit the scope of the disclosure of the present application. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion regarding the concepts disclosed in the present application. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative effort should fall within the scope of protection of the present application.

[0028] The accompanying drawings show structural schematic diagrams according to embodiments disclosed in this application. These drawings are not drawn to scale, and some details have been enlarged and may have been omitted for clarity. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0029] Referring to Figures 1 and 2, the solid-liquid two-phase thermal energy storage system described in this application includes a pump box 1, a pump 2, a first control valve 3, a second control valve 4, an electric heater 5, a third control valve 6, a fourth control valve 7, a high-efficiency heat exchanger module 8, a flow equalization module 9, a solid thermal energy storage module 10, an auxiliary electric heater 11, a liquid storage module 12, a solid thermal energy storage material 13, a filter screen 14, and an overflow hole 15.

[0030] The high-efficiency heat exchanger module 8, the flow equalization module 9, each solid heat storage module 10, and the liquid storage module 12 are arranged sequentially from top to bottom. The outlet of the liquid storage module 12 is divided into two paths after passing through the pump box 1 and the pump 2. One path is connected to the liquid inlet of the high-efficiency heat exchanger module 8 via the second control valve 4, and the other path is connected to the inlet of the electric heater 5 via the first control valve 3. The outlet of the electric heater 5 is divided into two paths. One path is connected to the liquid inlet of the high-efficiency heat exchanger module 8 via the third control valve 6, and the other path is connected to the inlet of the flow equalization module 9 via the fourth control valve 7. The liquid outlet of the high-efficiency heat exchanger module 8 is connected to the inlet of the flow equalization module 9. The outlet of the flow equalization module 9 is connected to the liquid inlet of the uppermost solid heat storage module 10. The overflow hole 15 of the upper solid heat storage module 10 is connected to the liquid inlet of the lower solid heat storage module 10. The overflow hole 15 of the lowermost solid heat storage module 10 is connected to the inlet of the liquid storage module 12.

[0031] In this embodiment, both the liquid storage module 12 and the solid heat storage module 10 are equipped with auxiliary electric heaters 11.

[0032] In this embodiment, the solid heat storage module 10 is filled with solid heat storage material 13, and a filter screen 14 is provided at both the liquid inlet and the overflow hole 15 of the solid heat storage module 10.

[0033] In this embodiment, the solid heat storage modules 10 are stacked sequentially from top to bottom.

[0034] In this embodiment, the number of liquid storage modules 12 can be adjusted according to actual use as needed.

[0035] In this embodiment, the solid heat storage material 13 is filled inside the solid heat storage module 10, and the filling amount is 80% to 90% of the effective volume of the solid heat storage module 10.

[0036] In this embodiment, the high-efficiency heat exchanger module 8 is divided into a liquid heat storage material channel and a steam-water channel, which can efficiently transfer the heat of the liquid heat storage material to the water vapor. The liquid heat storage material can smoothly pass through the high-efficiency heat exchanger module 8 and enter the flow equalization module 9. At the same time, the liquid heat storage material will not remain in the high-efficiency heat exchanger module 8.

[0037] In this embodiment, the flow equalization module 9 can evenly distribute the liquid heat storage material to the uppermost solid heat storage module 10, ensuring that the liquid heat storage material and the solid heat storage material 13 in the solid heat storage module 10 can be in full contact.

[0038] In this embodiment, the solid heat storage material 13 is a granular material with a particle size between 10 and 30 mm and has good thermal stability.

[0039] In this embodiment, the first control valve 3, the second control valve 4, the third control valve 6 and the fourth control valve 7 are all arranged vertically, and the pipes connected to them all have a slope of not less than 10°.

[0040] In this embodiment, the filter screen 14 can filter particles with a maximum equivalent diameter of no more than 2 mm; the diameter of the overflow hole 15 is 10-20 mm, and the inlet of the overflow hole 15 is 10-20 mm higher than the bottom plate of the solid heat storage module 10; the number of overflow holes 15 can meet the flow rate of 1.5 times the maximum flow rate of the liquid heat storage material in each unit.

[0041] In this embodiment, the auxiliary electric heater 11 can operate stably within a temperature range of 600 to 800°C.

[0042] The specific working process for this application is as follows:

[0043] Heat storage process: The first control valve 3 and the fourth control valve 7 are in the open state, and the second control valve 4 and the third control valve 6 are in the closed state. The liquid heat storage material with a lower temperature is drawn out from the liquid storage module 12 through the pump box 1 under the drive of the pump 2 and sent into the electric heater 5. After passing through the electric heater 5, the temperature of the liquid heat storage material rises and becomes a high-temperature liquid heat storage material. Then, it flows evenly into the uppermost solid heat storage module 10 through the flow equalization module 9 and exchanges heat with the solid heat storage material 13 therein, so that the temperature of the solid heat storage material 13 gradually rises. Under the action of gravity, the liquid heat storage material flows into the next layer of solid heat storage module 10 through the filter screen 14 and the overflow hole 15, thereby heating the solid heat storage material 13 in each layer of solid heat storage module 10 step by step. The temperature of the liquid heat storage material also gradually decreases until the liquid heat storage material flows into the liquid storage module 12 again and enters the next round of heating cycle process. The heat storage process stops when the temperature inside all solid heat storage modules 10 reaches the set value. During the heat storage process, the set temperature of the solid heat storage module 10 is adjusted according to actual needs, and the heating power of the electric heater 5 can also be adjusted in real time according to the power supply load requirements. The output of the pump 2 is matched with the power of the electric heater 5 to ensure that the temperature of the liquid heat storage material output by the electric heater 5 is at the set value and remains stable.

[0044] Heat release process: The second control valve 4 is in the open state, while the first control valve 3, the fourth control valve 7, and the third control valve 6 are in the closed state. The high-temperature liquid heat storage material is drawn out from the liquid storage module 12 through the pump box 1 under the drive of the pump 2 and sent into the high-efficiency heat exchanger module 8 to heat the steam-water system. The liquid heat storage material cooled by the high-efficiency heat exchanger module 8 flows into the flow equalization module 9. The flow equalization module 9 evenly distributes the cooled liquid heat storage material into the solid heat storage module 10, where it fully contacts and heats the solid heat storage material 13. The liquid heat storage material is continuously heated by each solid heat storage module 10, and the temperature of the liquid heat storage material gradually increases. The high-temperature liquid heat storage material eventually flows into the liquid storage module 12 for the next round of heat release. The heat release process ends when the liquid heat storage material reaches the minimum allowable temperature. During the heat release process, the output of the pump 2 is matched with the steam-water parameters at the inlet and outlet of the high-efficiency heat exchanger module 8 to ensure the stability of the steam-water parameters.

[0045] Direct heating process: The first control valve 3 and the third control valve 6 are in the open state, while the second control valve 4 and the fourth control valve 7 are in the closed state. Driven by pump 2, the cooler liquid heat storage material is drawn from the liquid storage module 12 through the pump box 1 and sent to the electric heater 5. After passing through the electric heater 5, the liquid heat storage material enters the high-efficiency heat exchanger module 8 to heat the steam and water. After cooling through the high-efficiency heat exchanger module 8, the liquid heat storage material flows into the flow equalization module 9. The flow equalization module 9 evenly distributes the cooled liquid heat storage material into the solid heat storage modules 10. Under the action of gravity, the liquid heat storage material passes through each layer of solid heat storage modules 10 and enters the liquid storage module 12 for the next round of direct heating cycle. The end time of this process is determined according to actual needs. During the direct heating process, the output of pump 2 is matched with the power of the electric heater 5 and the steam and water parameters at the inlet and outlet of the high-efficiency heat exchanger module 8 to ensure stable steam and water parameters.

[0046] System restart: After the system is put into operation for the first time or after a long period of shutdown, if the system temperature and the temperature of the solid heat storage material 13 are lower than the minimum allowable operating temperature, the auxiliary electric heater 11 will be turned on to raise the system temperature and the temperature of the solid heat storage material 13 to above the minimum allowable temperature, and then a proper heat storage process will be carried out, and the system will be able to operate normally.

[0047] It should be noted that in this application, there is no need to worry about the liquid heat storage material solidifying at low temperatures, which could cause the system to malfunction. In addition, in this application, all pipes with liquid heat storage material flowing through them have a downward slope, and there are reasonable overflow structures between modules. When the system stops operating, the liquid heat storage material in the system flows back to the liquid storage module 12 under the action of gravity, thus eliminating the need for a large-area heat tracing system.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of the claims of this application.

Claims

1. A solid-liquid two-phase thermal storage system, characterized in that, It includes a high-efficiency heat exchanger module (8), a flow equalization module (9), a liquid storage module (12), a first control valve (3), a second control valve (4), an electric heater (5), a third control valve (6), a fourth control valve (7), and several solid heat storage modules (10); The high-efficiency heat exchanger module (8), the flow equalization module (9), each solid heat storage module (10), and the liquid storage module (12) are arranged sequentially from top to bottom. The outlet of the liquid storage module (12) is divided into two paths after passing through the pump box (1) and the pump (2). One path is connected to the liquid inlet of the high-efficiency heat exchanger module (8) through the second control valve (4), and the other path is connected to the inlet of the electric heater (5) through the first control valve (3). The outlet of the electric heater (5) is divided into two paths. One path is connected to the liquid inlet of the high-efficiency heat exchanger module (8) through the third control valve (6), and the other path is connected to the liquid inlet of the high-efficiency heat exchanger module (8) through the third control valve (6). The four control valves (7) are connected to the inlet of the flow equalization module (9), the liquid outlet of the high-efficiency heat exchanger module (8) is connected to the inlet of the flow equalization module (9), the outlet of the flow equalization module (9) is connected to the liquid inlet of the uppermost solid heat storage module (10), the overflow hole (15) of the upper solid heat storage module (10) is connected to the liquid inlet of the lower solid heat storage module (10), and the overflow hole (15) of the lowermost solid heat storage module (10) is connected to the inlet of the liquid storage module (12). The solid heat storage module (10) is filled with solid heat storage material (13).

2. The solid-liquid two-phase thermal storage system according to claim 1, characterized in that, Both the liquid storage module (12) and the solid heat storage module (10) are equipped with auxiliary electric heaters (11).

3. The solid-liquid two-phase thermal storage system according to claim 1, characterized in that, A filter screen (14) is provided at both the liquid inlet of the solid heat storage module (10) and the overflow hole (15) of the solid heat storage module (10).

4. The solid-liquid two-phase thermal storage system according to claim 1, characterized in that, The amount of solid thermal storage material (13) is 80% to 90% of the effective volume of the solid thermal storage module (10).

5. The solid-liquid two-phase thermal storage system according to claim 1, characterized in that, The solid heat storage material (13) is a granular material with a particle size between 10 and 30 mm.

6. The solid-liquid two-phase thermal storage system according to claim 1, characterized in that, The first control valve (3), the second control valve (4), the third control valve (6), and the fourth control valve (7) are all arranged in a vertical direction.

7. A method for operating the solid-liquid two-phase thermal storage system according to claim 1, characterized in that, This includes heat storage processes, heat release processes, and direct heating processes.

8. The operating method of the solid-liquid two-phase thermal storage system according to claim 7, characterized in that, The heat storage process is as follows: The first control valve (3) and the fourth control valve (7) are in the open state, and the second control valve (4) and the third control valve (6) are in the closed state. The liquid heat storage material with a lower temperature is drawn out from the liquid storage module (12) through the pump box (1) under the drive of the pump (2) and sent into the electric heater (5). After passing through the electric heater (5), the temperature of the liquid heat storage material rises and becomes a liquid heat storage material in a high-temperature state. Then, it flows evenly into the uppermost solid heat storage module (10) through the flow equalization module (9) and exchanges heat with the solid heat storage material (13) therein. This causes the temperature of the solid heat storage material (13) to gradually rise; under the action of gravity, the liquid heat storage material flows into the next layer of solid heat storage module (10) through the filter (14) and overflow hole (15), thereby heating the solid heat storage material (13) in each layer of solid heat storage module (10) step by step, and the temperature of the liquid heat storage material also gradually decreases until the liquid heat storage material flows into the liquid storage module (12) again, and the liquid heat storage material enters the next round of heating cycle process again until the temperature inside all solid heat storage modules (10) reaches the set value, and the heat storage process stops.

9. The operating method of the solid-liquid two-phase thermal storage system according to claim 7, characterized in that, The heat release process is as follows: The second control valve (4) is in the open state, and the first control valve (3), the fourth control valve (7), and the third control valve (6) are in the closed state. The high-temperature liquid heat storage material is drawn out from the liquid storage module (12) through the pump box (1) under the drive of the pump (2) and sent into the high-efficiency heat exchanger module (8) to heat the steam-water system. The liquid heat storage material cooled by the high-efficiency heat exchanger module (8) flows into the flow equalization module (9). The flow equalization module (9) evenly distributes the cooled liquid heat storage material into the solid heat storage module (10). The liquid heat storage material is fully contacted with the solid heat storage material (13) in the solid heat storage module (10) and heated. The liquid heat storage material is continuously heated by each solid heat storage module (10), and the temperature of the liquid heat storage material gradually increases. The liquid heat storage material with a higher temperature eventually flows into the liquid storage module (12) for another round of heat release. The heat release process ends when the liquid heat storage material reaches the minimum allowable temperature. During the heat release process, the output of the pump (2) matches the steam and water parameters at the inlet and outlet of the high-efficiency heat exchanger module (8) to ensure that the steam and water parameters are stable.

10. The operating method of the solid-liquid two-phase thermal storage system according to claim 7, characterized in that, The direct heating process is as follows: The first control valve (3) and the third control valve (6) are in the open state, and the second control valve (4) and the fourth control valve (7) are in the closed state. The liquid heat storage material with a lower temperature is drawn out from the liquid storage module (12) through the pump box (1) under the drive of the pump (2) and sent to the electric heater (5). After passing through the electric heater (5), the liquid heat storage material enters the high-efficiency heat exchanger module (8) to heat the steam and water. The liquid heat storage material that has been cooled by the high-efficiency heat exchanger module (8) flows into the flow equalization module (9). The flow equalization module (9) evenly distributes the liquid heat storage material with a lower temperature to the solid heat storage module (10). Under the action of gravity, the liquid heat storage material passes through each layer of solid heat storage module (10) and enters the liquid storage module (12) to carry out the next round of direct heating cycle. The end time of this process is determined according to actual needs. During the direct heating process, the output of the pump (2) and the power of the electric heater (5) are related to the flow rate of the liquid heat storage material. The steam and water parameters at the inlet and outlet of the high-efficiency heat exchanger module (8) are matched to ensure the stability of the steam and water parameters.

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