A staggered solid heat storage system and operation method

Abstract

The present invention discloses a staggered solid heat storage system and operating method. The system consists of a heat medium inlet, a heat medium outlet, a water feed pump, an inlet header, an outlet header, heat charging pipes, heat release pipes, solid heat storage materials, and a control valve. The system is applicable to various heat storage systems using solid materials as the heat storage medium and can effectively address the problem of unstable heat release during solid heat storage systems. The system utilizes the constant temperature and pressure characteristics of water during phase change to stabilize the heat release process and utilizes a staggered layout to improve the uniformity of the temperature field of the solid heat storage system. Furthermore, a bypass is used to adjust the feed water temperature to control steam production, thereby ensuring that the steam parameters and flow rate during the heat release process are as stable as possible.

Description

Technical Field

[0001] The present invention belongs to the field of heat storage technology, and in particular relates to a staggered solid heat storage system and an operating method. Background Art

[0002] With the rapid growth of renewable energy sources such as wind and solar power, coupled with the increasing annual electricity consumption across society and the widening discrepancy between peak and valley power consumption, the grid is increasingly demanding low-cost, long-life energy storage technologies. Based on the quality of the energy stored, current energy storage technologies can be simply categorized into electrical storage, potential energy storage, and thermal storage. Electrical storage can be categorized into lithium batteries, flow batteries, and supercapacitors, potential energy storage into pumped hydro, compressed air, and flywheels, and thermal storage into solid-state thermal storage, molten salt thermal storage, and thermochemical storage.

[0003] Molten salt heat storage systems are currently widely used in applications such as solar thermal power plants and clean heating. They offer the advantages of high heat storage temperatures and long service life. However, this technology requires a high volume of molten salt for heat storage. For a heat storage temperature difference of 200°C and a heat storage capacity of 80MWh, the required volume of conventional molten salt is approximately 1,300 tons. The prices of single molten salts such as potassium nitrate, sodium nitrate, and calcium nitrate are significantly influenced by international markets and raw materials. Sharp increases in the costs of raw materials such as potassium chloride and nitric acid can lead to significant increases in molten salt prices, which directly impacts project investment costs and implementation schedules. Solid-state heat storage systems offer a simple and easy-to-implement heat storage technology. Their basic principle is to transfer heat to a solid heat storage material such as concrete or refractory bricks for storage. When heat is released, a heat transfer medium exchanges heat with the solid heat storage material. Solid-state heat storage materials are readily available and stable in price. Raw materials are not imported, making them insensitive to market price fluctuations. However, the disadvantage of the solid heat storage system is that the charging and discharging process is unstable. As heat is continuously released during the discharging process, the temperature of the solid heat storage material temperature field drops overall, resulting in a continuous decrease in the outlet temperature of the heat transfer medium during the discharging process, which affects the stability of the subsequent heat utilization system. Summary of the Invention

[0004] To solve the problem of unstable heat release in solid heat storage systems, the present invention proposes an interlaced solid heat storage system and operating method. The system utilizes the constant temperature and pressure characteristics of water phase change to stabilize the heat release process, uses an interlaced arrangement structure to improve the uniformity of the temperature field of the solid heat storage system, and uses a bypass to adjust the feed water temperature to control steam production, thereby making the steam parameters as stable as possible during the heat release process. The present invention is applicable to various heat storage systems using solid materials as heat storage media, and can effectively solve the problem of unstable heat release in solid heat storage systems.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0006] The embodiment of the present invention provides a staggered solid heat storage system, comprising a heat charging pipe with a heat medium inlet and a heat medium outlet at both ends, a water supply pump, an inlet header, an outlet header, a pressure regulating valve, a drain valve, a pressure reducing valve, a temperature regulating valve, a heat release pipe, and a solid heat storage material;

[0007] The heat charging pipe is horizontally arranged in the solid heat storage material; the outlet of the water supply pump is connected to the inlet of the inlet header and the thermostatic valve respectively; the inlet header includes a plurality of outlets, and the outlet header includes a plurality of inlets, and the outlets of the inlet header are respectively connected to the inlet of the outlet header through the heat release pipe;

[0008] The outlet of the outlet manifold is connected to the pressure regulating valve and the drain valve respectively; the drain valve and the temperature regulating valve are connected to the inlet of the pressure reducing valve respectively; the outlet of the pressure reducing valve is connected to the inlet of the water supply pump.

[0009] In some embodiments, the heat release tube is vertically arranged in the solid heat storage material and is arranged vertically crosswise with the heat charging tube, so that the heat absorption of each heat release tube in the heat storage system is kept consistent during the heat release process; and the water entering the heat release tube is converted from liquid to vapor.

[0010] In some embodiments, when the liquid level in the outlet manifold exceeds the drain valve, the drain valve automatically drains the water; the flow rate through the drain valve gradually decreases from high to zero; the drain valve is used to automatically adjust the inlet water temperature of the feed water pump and stabilize the steam production.

[0011] In some embodiments, the temperature regulating valve is used to lower the temperature of the water outlet from the drain valve to prevent the water outlet after flowing through the pressure reducing valve from generating steam and affecting the operation of the water supply pump.

[0012] In some embodiments, the pressure regulating valve is used to adjust the steam pressure according to demand.

[0013] In some embodiments, a method for operating an interleaved solid thermal storage system is proposed, wherein the thermal storage system in any of the above embodiments is operated according to the following method, specifically including two modes: a heat charging mode and a heat releasing mode:

[0014] Heat charging mode: high-temperature heat transfer medium enters the heat charging pipe from the heat charging medium inlet, transfers heat to the solid heat storage material through the heat charging pipe and stores the heat in the solid heat storage material;

[0015] Heat release mode: the feed water is mixed with the outlet water of the pressure reducing valve and then sent to the inlet header and the temperature regulating valve respectively through the feed water pump; the water entering the inlet header passes through the heat release pipe and is partially converted into saturated steam in the heat release pipe before entering the outlet header; the saturated steam is separated in the outlet header and discharged through the pressure regulating valve; the saturated water is mixed with the low-temperature water after the temperature is adjusted by the temperature regulating valve through the drain valve and then enters the pressure reducing valve for decompression, and the decompressed water is mixed with the feed water and re-enters the feed water pump.

[0016] In some embodiments, the high-temperature heat transfer medium first flows transversely in the solid heat storage material, then turns downward and continues to flow transversely in the solid heat storage material until it flows to the heat medium outlet at the bottom of the solid heat storage material.

[0017] In some embodiments, the heat release process ends when the drain valve is completely closed and the water temperature in the outlet header is 10° C. lower than the temperature of saturated steam.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The staggered solid heat storage system and operation method of the present invention are applicable to various heat storage systems using solid materials as heat storage media, and can effectively solve the problem of unstable heat release process in solid heat storage systems. The system utilizes the constant temperature and pressure characteristics of water phase change to stabilize the heat release process, uses a staggered layout structure to improve the uniformity of the temperature field of the solid heat storage system, and uses a bypass to adjust the feed water temperature to control steam production, thereby making the steam parameters and flow rate as stable as possible during the heat release process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of an interlaced solid heat storage system proposed in one embodiment of the present invention.

[0021] In the figure: 1. Heat medium inlet; 2. Heat medium outlet; 3. Water supply pump; 4. Inlet header; 5. Outlet header; 6. Pressure regulating valve; 7. Drain valve; 8. Pressure reducing valve; 9. Temperature regulating valve; 10. Heat charging pipe; 11. Heat release pipe; 12. Solid heat storage material. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] like Figure 1 As shown, a staggered solid heat storage system consists of a heat medium inlet 1, a heat medium outlet 2, a water pump 3, an inlet header 4, an outlet header 5, a pressure regulating valve 6, a drain valve 7, a pressure reducing valve 8, a temperature regulating valve 9, a heat charging pipe 10, a heat releasing pipe 11 and a solid heat storage material 12.

[0024] The heat medium inlet 1 and the heat medium outlet 2 are respectively connected to the two ends of the heat charging pipe 10, and the heat charging pipe 10 is arranged horizontally in the solid heat storage material 12; the outlet of the water supply pump 3 is divided into two routes, one is connected to the inlet of the inlet header 4, and the other is connected to the temperature regulating valve 9; the inlet header 4 has multiple outlets, and the outlet header 5 has multiple inlets. Each outlet of the inlet header 4 is connected to an inlet of the outlet header 5 through a heat release pipe 11, and the heat release pipe 11 is vertically arranged in the solid heat storage material 12 and is arranged vertically crosswise with the heat charging pipe 10; the outlet of the outlet header 5 is divided into two routes, one is connected to the pressure regulating valve 6, and the other is connected to the temperature regulating valve 9 and the pressure reducing valve 8 through the drain valve 7, and the other side of the water outlet of the pressure reducing valve 8 is connected to the inlet of the water supply pump 3.

[0025] The staggered solid heat storage system of the present invention operates according to the following method:

[0026] Heat is generally not released during the charging process, but when the user does need to generate steam during the charging process, the charging mode and the heat release mode can be operated simultaneously. In the charging mode, when heat release is not in progress, there should be no liquid water in the outlet header 5 and the heat release pipe 11. Assuming that the heat transfer medium is thermal oil and the inlet temperature is 300°C, the 300°C thermal oil enters the heat storage pipe 10 through the heat medium inlet 1. The thermal oil first flows horizontally in the solid heat storage material 12, turns downward, and continues to flow horizontally in the solid heat storage material 12 until it reaches the heat medium outlet 2 at the bottom of the solid heat storage material 12. The thermal oil temperature becomes 120°C. The thermal oil transfers heat to the solid heat storage material 12 through the tank wall of the heat storage pipe 10, storing the heat in the solid heat storage material 12. Overall, the temperature of the solid heat storage material 12 is basically the same in the horizontal direction, but there is a significant temperature difference in the vertical direction, with the upper temperature being higher and the lower temperature being lower. The upper temperature does not exceed 300°C, and the lower temperature does not exceed 120°C.

[0027] During the heat release process, it is assumed that the target steam parameters are 1MPa and 10t / h. At the beginning of the heat release mode, the overall temperature of the solid heat storage material 12 is relatively high, and the heat transfer is maximum when the feed water temperature remains unchanged. In order to ensure the stability and continuity of the steam flow and temperature during the heat release process, the outlet flow of the feed water pump 3 is greater than 10t / h at this time. Assuming that the initial flow value is 25t / h, the feed water temperature is 30℃, the feed water pressure is 0.5MPa, and the feed water flow is the same as the target steam flow, which is 10t / h. The feed water is mixed with the water after the pressure reducing valve 8 and enters the feed water pump 3. The water flow after the pressure reducing valve 8 is 15t / h. The total flow at the outlet of the feed water pump 3 is 25t / h, of which 20t / h of water enters the inlet header 4, and 5t / h of water is sent to the front of the pressure reducing valve 8 through the temperature regulating valve 9 to reduce the temperature of the water after the drain valve 7; the water in the inlet header 4 enters the outlet header 5 through the heat release pipe 11, and the 10t / h of water is converted into steam in the process of passing through the heat release pipe 11. The 10t / h of water is converted into steam in the process of passing through the heat release pipe 11. During the process, the steam is converted into saturated water at a temperature of approximately 180°C. In the outlet header 5, the steam and water are separated, with 10t / h of saturated steam discharged through the pressure regulating valve 6 and 10t / h of saturated water discharged through the drain valve 7. After the drain valve 7, the 10t / h of 180°C saturated water is mixed with 5t / h of 30°C water. The temperature of the mixed water is approximately 130°C. The mixed water is then reduced in pressure to 0.5MPa by the pressure reducing valve 8 and mixed with the 10t / h of feed water before re-entering the feed pump 3. At this point, the temperature of the mixed water deviates significantly from the water temperature at the outlet of the feed pump 3. Based on the actual operating characteristics of the solid thermal storage system, the design parameters are adjusted to ensure that the temperature difference before and after the feed pump 3 is approximately the same. As the heat release process proceeds, the overall temperature of the solid heat storage material 12 decreases, but still shows a trend of high at the top and low at the bottom. The outlet flow of the water pump 3 gradually decreases from 25t / h to 10t / h. At this time, the drain valve 7 no longer discharges saturated water. When the water temperature in the outlet header 5 is lower than 170℃, the heat release process is considered to be over.

[0028] Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. A person skilled in the art, guided by the present invention, may make many modifications without departing from the spirit of the present invention, and all such modifications shall fall within the scope of protection of the present invention. Any insubstantial modification of the present invention using this concept shall constitute an infringement of the scope of protection of the present invention.

Claims

1. A method for operating an interleaved solid heat storage system, characterized in that: The system comprises: a heat charging pipe (10) with a heat charging medium inlet (1) and a heat charging medium outlet (2) respectively provided at both ends, a water supply pump (3), an inlet header (4), an outlet header (5), a pressure regulating valve (6), a drain valve (7), a pressure reducing valve (8), a temperature regulating valve (9), a heat release pipe (11), and a solid heat storage material (12); The heat charging pipe (10) is horizontally arranged in the solid heat storage material (12); the outlet of the water supply pump (3) is respectively connected to the inlet of the inlet header (4) and the temperature regulating valve (9); the inlet header (4) includes a plurality of outlets, the outlet header (5) includes a plurality of inlets, and the outlets of the inlet header (4) are respectively connected to the inlet of the outlet header (5) through the heat releasing pipe (11); the heat releasing pipe (11) is vertically arranged in the solid heat storage material (12) and is arranged perpendicularly to the heat charging pipe (10); The outlet of the outlet manifold (5) is connected to the pressure regulating valve (6) and the drain valve (7) respectively; the drain valve (7) and the temperature regulating valve (9) are connected to the inlet of the pressure reducing valve (8) respectively; the outlet of the pressure reducing valve (8) is connected to the inlet of the water supply pump (3), and the inlet of the water supply pump (3) also flows with water; when the liquid level in the outlet manifold (5) exceeds the drain valve (7), the drain valve (7) automatically drains water; The heat storage system operates in the following manner, specifically including two modes: a heat charging mode and a heat releasing mode: Heat charging mode: a high-temperature heat transfer medium enters the heat charging pipe (10) from the heat charging medium inlet (1), transfers heat to the solid heat storage material (12) through the heat charging pipe (10), and stores the heat in the solid heat storage material (12); Heat release mode: the feed water is mixed with the outlet water of the pressure reducing valve (8) and then sent to the inlet header (4) and the temperature regulating valve (9) respectively through the feed water pump (3); the water entering the inlet header (4) passes through the heat release pipe (11) and is partially converted into saturated steam in the heat release pipe (11) and then enters the outlet header (5); the saturated steam is separated in the outlet header (5) and discharged through the pressure regulating valve (6); the saturated water in the outlet header (5) is mixed with the low-temperature water after the temperature is adjusted by the temperature regulating valve (9) through the drain valve (7) and then enters the pressure reducing valve (8) for pressure reduction. The water after pressure reduction is mixed with the feed water and then enters the feed water pump (3) again; As the heat release process proceeds, the overall temperature of the solid heat storage material (12) decreases and shows a trend of being higher at the top and lower at the bottom. The outlet flow of the water supply pump (3) gradually decreases, and the flow through the drain valve (7) gradually decreases from high to zero. The drain valve (7) is used to automatically adjust the inlet water temperature of the water supply pump (3) and stabilize the steam production.

2. The operating method according to claim 1, characterized in that: The heat release tube (11) and the heat charging tube (10) are arranged in a vertical cross pattern, so as to keep the heat absorption of each heat release tube (11) consistent during the heat release process of the heat storage system; and to convert the water introduced into the heat release tube (11) from liquid to vapor.

3. The operating method according to claim 1, characterized in that: The temperature regulating valve (9) is used to reduce the temperature of the water outlet from the drain valve (7) to prevent the water outlet from generating steam after flowing through the pressure reducing valve (8), thereby affecting the operation of the water supply pump (3).

4. The operating method according to claim 1, characterized in that: The pressure regulating valve (6) is used to adjust the steam pressure according to demand.

5. The operating method according to any one of claims 1 to 4, characterized in that: The high-temperature heat transfer medium first flows transversely in the solid heat storage material (12), then turns downward and continues to flow transversely in the solid heat storage material (12) until it reaches the heat medium outlet (2) at the lower part of the solid heat storage material (12).

6. The operating method according to claim 5, characterized in that: When the drain valve (7) is completely closed and the water temperature in the outlet header (5) is 10°C lower than the temperature of saturated steam, the heat release process ends.

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