Heat storage system and method based on alkali chloride solid solution composite phase change material

Abstract

The invention provides a heat storage system and method based on an alkali chloride solid solution composite phase change material. The heat storage system comprises a heat collection assembly, a high-temperature heat storage assembly, a high-temperature circulation assembly, a heat exchange assembly, a low-temperature heat storage assembly, a low-temperature circulation assembly, a dissolving tank, a stirrer, a temperature control assembly and a powder grinding device. Raw materials are placed in the dissolving tank, and precursor slurry is prepared under the stirring of the stirrer; dehydrating the precursor slurry by a temperature control assembly to obtain precursor powder, heating the precursor powder according to a set heating strategy and a set cooling strategy, and then cooling to obtain an original alkali metal chloride solid solution; and the original alkali metal chloride solid solution is ground by the grinding device, and the ground alkali metal chloride solid solution is obtained and serves as the fused salt heat storage medium. In this way, the working temperature and stability of the fused salt heat storage medium can be improved, in the heat exchange process, fused K atoms can play a role of a nucleating agent, crystallization is facilitated, the supercooling phenomenon is avoided, and the photo-thermal utilization rate is increased.

Description

Technical Field

[0001] The present invention relates to the field of photothermal energy storage technology, and in particular to a heat storage system and method based on an alkali metal chloride solid solution composite phase change material. Background Art

[0002] In the process of solar thermal power generation, molten salt heat storage technology is a key link in solving the intermittent and fluctuating nature of solar energy and regulating the mismatch between supply and demand. Therefore, the development of safe and efficient molten salt heat storage media and heat storage systems is of great significance.

[0003] Currently, the common molten salt heat storage media in solar thermal power generation technology are binary alkali metal nitrate mixtures and ternary alkali metal nitrate mixtures (KNO3 / NaNO3, KNO3 / NaNO3 / NaNO2), and their operating temperature is 550°C.

[0004] However, alkali metal nitrate mixtures such as binary alkali metal nitrate mixtures and ternary alkali metal nitrate mixtures have low operating temperatures, poor thermal stability, and low light and heat utilization rates. Summary of the Invention

[0005] The present invention provides a heat storage system and method based on an alkali metal chloride solid solution composite phase change material, which is used to solve the defects of the molten salt heat storage medium in the prior art, such as low operating temperature, poor thermal stability, and low light and heat utilization rate.

[0006] In one aspect, the present invention provides a heat storage system based on an alkali metal chloride solid solution composite phase change material, comprising a solid solution preparation device and a heat storage device; the heat storage device comprises a heat collection component, a high-temperature heat storage component, a high-temperature circulation component, a heat exchange component, a low-temperature heat storage component, and a low-temperature circulation component;

[0007] The heat collecting assembly, the high-temperature heat storage assembly, the high-temperature circulation assembly, the heat exchange assembly, the low-temperature heat storage assembly and the low-temperature circulation assembly are cyclically connected;

[0008] The solid solution preparation device includes a dissolution tank, a stirrer, a temperature control component and a grinder;

[0009] The raw materials are placed in the dissolution tank and the precursor slurry is prepared under stirring by the stirrer; wherein the raw materials include NaCl, KCl and deionized water;

[0010] The temperature control component is used to dehydrate the precursor slurry to obtain a precursor powder, and according to a set heating strategy and a cooling strategy, heat the precursor powder and then cool it to obtain an original alkali metal chloride solid solution;

[0011] The grinder is used to grind the original alkali metal chloride solid solution to obtain a ground alkali metal chloride solid solution, wherein the ground alkali metal chloride solid solution is filled into the heat collecting assembly.

[0012] According to a heat storage system based on an alkali metal chloride solid solution composite phase change material provided by the present invention, the heating strategy includes:

[0013] After heating the precursor powder to a first preset temperature according to a first heating rate, the heating rate is gradually reduced according to a preset first step length until it is reduced to a second heating rate, and the second heating rate is maintained until a heating end condition is met.

[0014] According to a heat storage system based on an alkali metal chloride solid solution composite phase change material provided by the present invention, the cooling strategy includes:

[0015] According to the first cooling rate, the precursor powder is cooled to a second preset temperature, and after maintaining the second preset temperature for a preset time, the cooling rate is gradually increased according to a preset second step length until it reaches the second cooling rate, and the second cooling rate is maintained until the cooling end condition is met.

[0016] According to a heat storage system based on an alkali metal chloride solid solution composite phase change material provided by the present invention, the chemical formula of the original alkali metal chloride solid solution and the chemical formula of the ground alkali metal chloride solid solution are both: Na .6 K .4 Cl, Na .5 K .5 Cl or Na .4 K .6 Cl.

[0017] According to a heat storage system based on an alkali metal chloride solid solution composite phase change material provided by the present invention, at least one of the heat collection component, the high-temperature heat storage component and the low-temperature heat storage component is filled with a porous expanded graphite material matrix.

[0018] According to the present invention, a heat storage system based on an alkali metal chloride solid solution composite phase change material further includes a controller, a first temperature sensor and a second temperature sensor;

[0019] The first temperature sensor is used to collect the inlet temperature of the heat exchange component;

[0020] The second temperature sensor is used to collect the outlet temperature of the heat exchange component;

[0021] The controller is used to determine the change value of the heat exchange efficiency of the heat exchanger based on the inlet temperature and the outlet temperature. If the change value of the heat exchange efficiency indicates a decrease and is greater than a preset threshold, it is determined that there is a blockage in the low-temperature circulation loop between the heat exchange component and the heat collection component.

[0022] According to the present invention, a heat storage system based on an alkali metal chloride solid solution composite phase change material further includes a vibration device;

[0023] The vibration device is arranged on at least one of the low-temperature circulation pipe of the low-temperature circulation loop, the low-temperature heat storage component and the low-temperature circulation component;

[0024] The controller is further configured to control the vibration device to vibrate.

[0025] According to a heat storage system based on an alkali metal chloride solid solution composite phase change material provided by the present invention, the controller is also used to determine the degree of blockage based on the change value of the heat exchange efficiency when it is determined that the low-temperature circulation loop is blocked, and determine the vibration parameters of the vibration device based on the degree of blockage.

[0026] According to the present invention, a heat storage system based on an alkali metal chloride solid solution composite phase change material further comprises:

[0027] The controller is further configured to control the vibration device to vibrate for a preset time period, and if the change in heat exchange efficiency is still greater than a preset threshold, send an instruction to stop heat exchange.

[0028] On the other hand, the present invention also provides a heat storage method based on an alkali metal chloride solid solution composite phase change material, which is applied to the heat storage system based on an alkali metal chloride solid solution composite phase change material as described in any one of the above items, and the method comprises:

[0029] Placing raw materials in the dissolution tank of the heat storage system and stirring them with the stirrer of the heat storage system to prepare a precursor slurry; wherein the raw materials include NaCl, KCl and deionized water;

[0030] Dehydrating the precursor slurry using the temperature control component of the heat storage system to obtain a precursor powder, and heating the precursor powder according to a set heating strategy and cooling strategy, and then cooling it to obtain an original alkali metal chloride solid solution;

[0031] The original alkali metal chloride solid solution is ground using the grinder of the heat storage system to obtain a ground alkali metal chloride solid solution, wherein the ground alkali metal chloride solid solution is filled into the heat collection component in the heat storage device of the heat storage system to complete heat storage and heat exchange.

[0032] The present invention provides a heat storage system and method based on an alkali metal chloride solid solution composite phase change material. In a dissolution tank, NaCl, KCl, and deionized water are stirred by an agitator to prepare a precursor slurry. The precursor slurry is dehydrated by a temperature control component to obtain a precursor powder. After the precursor powder is heated according to a set heating strategy and cooling strategy, the precursor powder is cooled to obtain the original alkali metal chloride solid solution. The original alkali metal chloride solid solution is ground by a grinder to obtain a ground alkali metal chloride solid solution, which is used as a molten salt heat storage medium for a heat storage device to complete the heat storage and heat exchange process. In this way, the operating temperature and stability of the molten salt heat storage medium can be improved based on the characteristics of the alkali metal chloride solid solution. During the heat exchange process, the K atoms in the molten salt heat storage medium can act as a nucleating agent, which is beneficial to crystallization to avoid supercooling, improve heat release efficiency, and thus improve the photothermal utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 This is one of the structural schematic diagrams of a heat storage system based on an alkali metal chloride solid solution composite phase change material provided in an embodiment of the present invention;

[0035] Figure 2 This is the second structural schematic diagram of the heat storage system based on the alkali metal chloride solid solution composite phase change material provided by an embodiment of the present invention;

[0036] Figure 3 This is a flow chart of a heat storage method based on an alkali metal chloride solid solution composite phase change material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0038] Currently, the most common molten salt heat storage media used in solar thermal power generation technology are binary and ternary alkali metal nitrate mixtures (KNO3 / NaNO3, KNO3 / NaNO3 / NaNO2), operating at 550°C. However, these alkali metal nitrate mixtures, such as binary and ternary alkali metal nitrate mixtures, have low phase transition temperatures, poor thermal stability, and low solar thermal efficiency.

[0039] Sodium chloride (NaCl) has the advantages of high thermal stability and low cost, and its operating temperature can reach 800°C. In addition, the increase in the operating temperature of the molten salt heat storage medium is conducive to the increase in steam temperature, thereby improving energy efficiency. Therefore, NaCl is one of the heat storage media with the most development potential. However, when NaCl is used as the molten salt heat storage medium in the heat storage system, the inorganic chloride salt suffers from supercooling and phase separation during use. The molten salt needs to be below the condensation point to begin crystallization, and it cannot change phase in time, resulting in untimely release and utilization of heat.

[0040] Therefore, in response to the defects of NaCl as a molten salt heat storage medium, further research found that mixing a certain amount of potassium chloride (KCl) in NaCl is beneficial to the crystallization phase transition of the molten salt heat storage medium, which can effectively avoid the problems of supercooling and phase separation during the use of inorganic chloride salts. Specifically, when NaCl and KCl are mixed, unlike simple physical mixing, the two are fully mixed at the lattice scale, forming an alkali metal chloride solid solution NaKCl(ss). This alkali metal chloride solid solution is based on the NaCl lattice, with a small amount of K atoms mixed in the lattice to form a new crystal. Among them, after the K atoms are mixed to form the solid solution NaKCl(ss), there are interactions between the metal atoms within the lattice, resulting in changes in the physical and chemical properties of the inorganic chloride salt. By forming crystal defects, the melting point is caused, making the freezing point of the molten salt system much lower than that of pure salt NaCl. In addition, after the solid solution NaKCl(ss) is formed, the K atoms play a role in promoting nucleation, which is beneficial to the crystallization phase transition of the molten salt system. Therefore, the physical and chemical properties of NaKCl(ss) can effectively avoid the problem of supercooling during the use of inorganic chloride salts.

[0041] Based on this research finding, the present invention provides the following technical solutions:

[0042] Figure 1 This is one of the structural schematic diagrams of the heat storage system based on the alkali metal chloride solid solution composite phase change material provided in an embodiment of the present invention.

[0043] like Figure 1As shown, the heat storage system based on the alkali metal chloride solid solution composite phase change material provided in an embodiment of the present invention includes a solid solution preparation device and a heat storage device; wherein, the heat storage device includes a heat collection component 6, a high-temperature heat storage component 9, a high-temperature circulation component 10, a heat exchange component 12, a low-temperature heat storage component 11, and a low-temperature circulation component 13. The heat collection component 6, the high-temperature heat storage component 9, the high-temperature circulation component 10, the heat exchange component 12, the low-temperature heat storage component 11, and the low-temperature circulation component 13 are cyclically connected so that the ground alkali metal chloride solid solution prepared by the solid solution preparation device is fed into the heat collection component 6 to complete the heat storage and heat exchange functions. The heat collection component 6 can collect solar energy or waste heat from coal burning, waste incineration, etc., which is not specifically limited in this embodiment.

[0044] Continue to see Figure 1 The solid solution preparation device includes a dissolution tank, an agitator, a temperature control component and a grinder.

[0045] In a specific implementation process, raw materials including NaCl and KCl are placed in the dissolution tank, and deionized water is added at a solid-liquid ratio of 1:5, and the mixture is uniformly stirred for a period of time (such as 4 hours) using a stirrer to prepare a precursor slurry.

[0046] After the precursor slurry is prepared, the precursor slurry can be transported to a temperature control assembly, which dehydrates the precursor slurry to obtain a precursor powder. The precursor powder is then heated and cooled according to a predetermined heating and cooling strategy to obtain the original alkali metal chloride solid solution. The temperature control assembly may include a heating device and a cooling device.

[0047] In a specific implementation process, the precursor slurry can be heated for a period of time (such as 4 hours) to dehydrate the precursor slurry to obtain a precursor powder, and then the precursor powder is continued to be heated. After the heating stop condition is reached, the heated fusion is cooled. After the cooling stop condition is reached, the original alkali metal chloride solid solution can be obtained.

[0048] In a specific implementation, the heating strategy includes heating the precursor powder to a first preset temperature at a first heating rate, then gradually reducing the heating rate according to a preset step size until it reaches a second heating rate, and then maintaining the second heating rate until a heating end condition is met. In other words, to reduce the impact of side reactions in the low-temperature stage, it is necessary to enter the high-temperature reaction zone as quickly as possible. At high temperatures, the diffusion rates of Na+ and K+ are significantly increased, promoting the mutual dissolution of ions in the crystal lattice and forming a uniform NaKCl(ss) solid solution.

[0049] Therefore, the precursor powder can be heated to a higher first preset temperature (400°C) at a higher first heating rate (such as 10°C / min), and the first preset temperature can be set according to the diffusion rate of Na+ and K+ obtained from the experiment. After the precursor powder is heated to the first preset temperature, in order to save energy and comprehensively consider the uniformity of the NaKCl (ss) solid solution, the heating rate can be gradually reduced according to the preset first step length until it is reduced to the second heating rate, and then the second heating rate is maintained until the heating end condition is met. Among them, the preset first step length can be a decrease rate of 1°C / 30s, the second heating rate can be 7°C / min, and the heating end condition is to reach the set heating time, such as 7 minutes, or to reach the set heating temperature, such as 700°C.

[0050] In a specific implementation process, the cooling strategy includes: cooling the precursor powder to a second preset temperature according to a first cooling rate, maintaining the second preset temperature for a preset time, gradually increasing the cooling rate according to a preset second step length until it reaches the second cooling rate, and maintaining the second cooling rate until the cooling end condition is met.

[0051] That is to say, in order to avoid stress or defects that may be caused by rapid quenching and to suppress low-temperature phase separation, at the same time, in order to improve preparation efficiency and avoid waiting for too long to cool, the precursor powder can be cooled to a second preset temperature (such as 500°C) at a lower first cooling rate (such as 4°C / min), and the second preset temperature can be set according to actual needs. After the precursor powder is cooled to the second preset temperature, the second preset temperature can be maintained for a preset time and a short heat preservation is performed to relieve the internal stress of the NaKCl (ss) solid solution. After reaching the heat preservation time, the cooling rate can be gradually increased according to the preset second step length until it increases to the second cooling rate, and the second cooling rate is maintained until the cooling end condition is met. Among them, the preset second step length can be a rising rate of 5°C / min, the second cooling rate can be 20°C / min), and the cooling end condition is to reach the set cooling time, such as 20min, or to reach the set cooling temperature of 25°C.

[0052] In a specific implementation process, under high temperature conditions, the types of solid solutions NaKCl(ss) formed under different Na / K molar ratios in the dissolution tank were tested, and the phase transition temperature and relative phase transition rate of the working fluid as a heat storage medium were tested. The data are shown in Table 1:

[0053] Table 1

[0054]

[0055]

[0056] Based on the above table, it can be seen that the formation of solid solution crystals can effectively improve the phase change rate of the molten salt heat storage medium. Among them, in Group 3, when the Na / K molar ratio in the dissolution pool was adjusted to 6:4, the relative phase change rate of the solid solution working fluid was formed to be optimal at 1.17, and the working temperature was relatively high, reaching 660°C; while in the experimental results, under other Na / K molar ratios, such as 8:2, 7:3, 3:7, etc., high-purity solid solutions could not be effectively formed, and a large amount of pure salt impurities were doped, resulting in supercooling and phase separation, which was not suitable as an ideal molten salt heat storage medium. Therefore, based on Table 1, it can be seen that after being processed by the temperature control component, the chemical formula of the original alkali metal chloride solid solution can be obtained as Na .6 K .4 Cl, Na .5 K .5 Cl or Na .4 K .6 However, considering the economic benefits, a high Na / K molar ratio scheme should be used as much as possible, that is, the chemical formula of the original alkali metal chloride solid solution is Na .6 K .4 When Cl is used, the economic benefits are relatively high.

[0057] In a specific implementation process, the obtained original alkali metal chloride solid solution can be transported to a grinder, and the grinder is used to grind the original alkali metal chloride solid solution to obtain a ground alkali metal chloride solid solution. After obtaining the ground alkali metal chloride solid solution, the ground alkali metal chloride solid solution can be transported to the heat collection component 6 so that the heat storage device completes the heat storage and heat exchange process. The chemical formula of the ground alkali metal chloride solid solution is also: Na .6 K .4 Cl, Na .5 K .5 Cl or Na .4 K .6 Cl, the particle size of the ground alkali metal chloride solid solution is less than or equal to 5 μm, so that the fluidity of the ground alkali metal chloride solid solution is increased as much as possible to avoid clogging the pipeline of the heat storage system.

[0058] Experiments have shown that compared with traditional molten nitrate technology, this embodiment uses solid solution NaKCl(ss) as the molten salt heat storage medium, significantly improving the operating temperature to approximately 770 to 800°C. The energy efficiency of the heat storage system is improved by 10 to 30%.

[0059] In the heat storage system based on the alkali metal chloride solid solution composite phase change material of this embodiment, NaCl, KCl and deionized water are stirred in a dissolution tank by an agitator to prepare a precursor slurry, and the precursor slurry is dehydrated by a temperature control component to obtain a precursor powder. After the precursor powder is heated according to the set heating strategy and cooling strategy, the precursor powder is cooled to obtain the original alkali metal chloride solid solution. The original alkali metal chloride solid solution is ground by a grinder to obtain a ground alkali metal chloride solid solution, which is used as a molten salt heat storage medium for the heat storage device to complete the heat storage and heat exchange process. In this way, the operating temperature and stability of the molten salt heat storage medium can be improved based on the characteristics of the alkali metal chloride solid solution. During the heat exchange process, the K atoms in the molten salt heat storage medium can act as a nucleating agent, which is beneficial to crystallization to avoid supercooling, improve heat release efficiency, and thus improve the photothermal utilization rate.

[0060] In a specific implementation, the resulting alkali metal chloride solid solution is essentially an inorganic chloride salt, which is corrosive and can chemically corrode the metal surfaces of the heat collection assembly 6, the high-temperature heat storage assembly 9, the low-temperature heat storage assembly 11, and so on, threatening the safe operation of the heat storage system. Therefore, in this embodiment, at least one of the heat collection assembly 6, the high-temperature heat storage assembly 9, and the low-temperature heat storage assembly 11 can be filled with a porous expanded graphite material matrix. This can encapsulate the alkali metal chloride solid solution, prevent the alkali metal chloride solid solution from corroding the metal surfaces of key storage devices, and ensure the safe operation of the heat storage system.

[0061] In a specific implementation process, such as Figure 1 As shown, the heat collection assembly 6 may include a solar collector, a high-temperature molten salt heat collection pipe, and a molten salt valve. The high-temperature molten salt heat collection pipe is provided with a porous expanded graphite matrix. The high-temperature circulation assembly 10 and the low-temperature heat storage assembly 11 are provided with a porous expanded graphite matrix. The heat exchange assembly 12 may be a steam generator. The heat storage and heat exchange process of the heat storage device is as follows:

[0062] The solar collector focuses light onto the high-temperature molten salt heat collecting tube. Under high temperature, the solid solution NaKCl (ss) quickly forms liquid molten salt. Driven by the high-temperature circulation component 10 (such as a circulation pump, etc.), it flows through the molten salt valve and enters the high-temperature heat storage component 9. After sufficient heat exchange with the heat exchange component 12, the molten salt phase changes and crystallizes back to a solid solution. Driven by the low-temperature heat storage component 11 (such as a circulation pump, etc.), it enters the low-temperature heat storage component 11 and finally circulates back to the high-temperature molten salt heat collecting tube.

[0063] However, in the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6, a solid solution circulates. In this process, although the particle size of the ground alkali metal chloride solid solution is small, it may still adhere to the pipe walls of each component in the low-temperature circulation loop, causing blockage. Therefore, in order to solve the above technical problems, the present invention provides the following technical solutions:

[0064] Figure 2 This is the second structural diagram of the heat storage system based on the alkali metal chloride solid solution composite phase change material provided by the embodiment of the present invention. Figure 2 As shown, the heat storage system based on alkali metal chloride solid solution composite phase change material provided by the embodiment of the present invention is Figure 1 On the basis of the illustrated embodiment, the system may further include a controller (not shown in the figure), a first temperature sensor 15 and a second temperature sensor 16 .

[0065] In a specific implementation process, the first temperature sensor 15 is arranged at the inlet of the heat exchange component 12, for collecting the inlet temperature of the heat exchange component 12; the second temperature sensor 16 is arranged at the outlet of the heat exchange component 12, for collecting the outlet temperature of the heat exchange component 12; the controller is used to determine the change value of the heat exchange efficiency of the heat exchanger based on the inlet temperature and the outlet temperature. If the change value of the heat exchange efficiency is greater than a preset threshold, it is determined that there is a blockage in the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6.

[0066] Specifically, when the low-temperature circulation loop is not blocked, the efficiency of the heat exchanger is generally maintained at a relatively stable value and is relatively high. However, if the low-temperature circulation loop is not blocked, the efficiency of the heat exchanger will decrease and become relatively unstable. Therefore, the heat exchange efficiency of the heat exchanger can be obtained by measuring the inlet temperature of the heat exchange component 12 and the outlet temperature of the heat exchange component 12, and compared with the heat exchange efficiency of the heat exchanger when it is not blocked to obtain the change in the heat exchange efficiency of the heat exchanger. If the change in the heat exchange efficiency of the heat exchanger indicates a decrease and is greater than a preset threshold, it is determined that the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6 is blocked.

[0067] Specifically, if there is a blockage in the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6, the inlet temperature of the heat exchange component 12 does not change much in a short period of time, while the outlet temperature of the heat exchange component 12 usually increases. The heat exchange efficiency of the heat exchange component 12 when the blockage occurs can be obtained, which is usually lower than the heat exchange efficiency of the heat exchange component 12 when no blockage occurs. Based on the heat exchange efficiency of the heat exchange component 12 when the blockage occurs and the heat exchange efficiency of the heat exchange component 12 when no blockage occurs, the change in the heat exchange efficiency of the heat exchange component 12 can be obtained. If the change in the heat exchange efficiency of the heat exchanger is greater than a preset threshold, it can be clearly determined that there is a blockage in the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6, so that corresponding measures can be taken later.

[0068] Continue to see Figure 2 The heat storage system further includes a vibration device 14 , which is disposed on at least one of the low-temperature circulation pipe of the low-temperature circulation loop, the low-temperature heat storage component 11 , and the low-temperature circulation component 13 . Figure 2 The low-temperature circulation piping, the low-temperature heat storage assembly 11, and the low-temperature circulation assembly 13 of the low-temperature circulation loop are used as an example for illustration. The number and location of the vibrating device 14 can be set according to actual needs. The vibrating device 14 can be an ultrasonic oscillator or other vibrator, and this embodiment does not impose specific limitations.

[0069] In a specific implementation process, when it is detected that the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6 is blocked, the controller can control the vibration device 14 to vibrate, thereby vibrating the molten salt heat storage medium in the low-temperature circulation loop and improving the fluidity of the low-temperature circulation loop.

[0070] In a specific implementation process, when the controller determines that the low-temperature circulation loop is blocked, it can determine the degree of blockage based on the change in the heat exchange efficiency, and determine the vibration parameters of the vibration device 14 based on the degree of blockage.

[0071] Specifically, a correlation between the change in heat exchange efficiency, the degree of blockage, and vibration parameters can be established through a large amount of experimental data. Thus, after knowing the change in heat exchange efficiency, this correlation can be used to determine the degree of blockage in the low-temperature circulation loop and the corresponding vibration parameters, so that the vibration device 14 can be controlled based on the vibration parameters. The vibration parameters include vibration frequency, amplitude, vibration duration, etc.

[0072] In a specific implementation process, when the controller controls the vibration device 14 to vibrate, the change value of the heat exchange efficiency will be continuously obtained and compared with the preset threshold value. When the controller controls the vibration device 14 to vibrate for a preset time, if it is detected that the change value of the heat exchange efficiency is still greater than the preset threshold value, it means that the vibration method of the vibration device 14 cannot effectively solve the blockage of the low-temperature circulation loop. In order to avoid danger to the heat storage system, an instruction to stop heat exchange can be sent so that the heat storage system no longer exchanges heat.

[0073] The heat storage system based on the alkali metal chloride solid solution composite phase change material of this embodiment uses the inlet temperature and the outlet temperature of the heat exchanger to determine the change in the heat exchange efficiency of the heat exchanger. When the change in the heat exchange efficiency indicates a decrease and is greater than a preset threshold, it is determined that the low-temperature circulation loop between the heat exchange component 12 and the heat collection component 6 is blocked, and the vibration device 14 is controlled to vibrate to resolve the blockage of the low-temperature circulation loop. After the vibration device 14 vibrates for a period of time, if the low-temperature circulation loop is still blocked, the heat storage device is controlled to stop heat exchange, thereby avoiding danger to the heat storage system and improving the reliability and safety of the operation of the heat storage system.

[0074] Based on the same general inventive concept, the present invention also protects a heat storage method based on an alkali metal chloride solid solution composite phase change material. The heat storage method based on an alkali metal chloride solid solution composite phase change material provided by the present invention is described below. The heat storage method based on an alkali metal chloride solid solution composite phase change material described below and the heat storage system based on an alkali metal chloride solid solution composite phase change material described above can be referred to in correspondence with each other.

[0075] Figure 3 This is a flow chart of a heat storage method based on an alkali metal chloride solid solution composite phase change material provided by an embodiment of the present invention. Figure 3 As shown, the heat storage method based on the alkali metal chloride solid solution composite phase change material may include the following steps:

[0076] 301. Placing raw materials in a dissolving tank of the heat storage system and stirring them using a stirrer of the heat storage system to prepare a precursor slurry;

[0077] In a specific implementation process, the raw materials include NaCl, KCl and deionized water.

[0078] 302. Dehydrate the precursor slurry using the temperature control component of the heat storage system to obtain a precursor powder, and heat the precursor powder according to a set heating strategy and cooling strategy, and then cool it to obtain an original alkali metal chloride solid solution;

[0079] In a specific implementation process, the heating strategy includes:

[0080] After heating the precursor powder to a first preset temperature according to a first heating rate, gradually reducing the heating rate according to a preset first step length until it reaches a second heating rate, and maintaining the second heating rate until a heating end condition is met;

[0081] The cooling strategy includes:

[0082] According to the first cooling rate, the precursor powder is cooled to a second preset temperature, and after maintaining the second preset temperature for a preset time, the cooling rate is gradually increased according to a preset second step length until it reaches the second cooling rate, and the second cooling rate is maintained until the cooling end condition is met.

[0083] 303. Grind the original alkali metal chloride solid solution using the grinder of the heat storage system to obtain a ground alkali metal chloride solid solution, wherein the ground alkali metal chloride solid solution is filled into the heat collection component 6 in the heat storage device of the heat storage system to complete heat storage and heat exchange.

[0084] In a specific implementation process, the above method can be implemented by an automated device, and the automated device can be controlled by a controller calling relevant logic instructions from a memory, wherein the logic instructions in the memory can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program code, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0085] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0086] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A heat storage system based on alkali metal chloride solid solution composite phase change material, characterized in that: It includes a solid solution preparation device and a heat storage device; the heat storage device includes a heat collection component, a high-temperature heat storage component, a high-temperature circulation component, a heat exchange component, a low-temperature heat storage component and a low-temperature circulation component; The heat collecting assembly, the high-temperature heat storage assembly, the high-temperature circulation assembly, the heat exchange assembly, the low-temperature heat storage assembly and the low-temperature circulation assembly are cyclically connected; The solid solution preparation device includes a dissolution tank, a stirrer, a temperature control component and a grinder; The raw materials are placed in the dissolution tank and the precursor slurry is prepared under stirring by the stirrer; wherein the raw materials include NaCl, KCl and deionized water; The temperature control component is used to dehydrate the precursor slurry to obtain a precursor powder, and according to a set heating strategy and a cooling strategy, heat the precursor powder and then cool it to obtain an original alkali metal chloride solid solution; The grinder is used to grind the original alkali metal chloride solid solution to obtain a ground alkali metal chloride solid solution, wherein the ground alkali metal chloride solid solution is filled into the heat collecting assembly.

2. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 1, characterized in that: The heating strategy includes: After heating the precursor powder to a first preset temperature according to a first heating rate, the heating rate is gradually reduced according to a preset first step length until it is reduced to a second heating rate, and the second heating rate is maintained until a heating end condition is met.

3. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 1, characterized in that: The cooling strategy includes: According to the first cooling rate, the precursor powder is cooled to a second preset temperature, and after maintaining the second preset temperature for a preset time, the cooling rate is gradually increased according to a preset second step length until it reaches the second cooling rate, and the second cooling rate is maintained until the cooling end condition is met.

4. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 1, characterized in that: The chemical formula of the original alkali metal chloride solid solution and the chemical formula of the ground alkali metal chloride solid solution are both: Na .6 K .4 Cl, Na .5 K .5 Cl or Na .4 K .6 Cl.

5. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 1, characterized in that: At least one of the heat collection component, the high-temperature heat storage component, and the low-temperature heat storage component is filled with a porous expanded graphite material matrix.

6. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 1, characterized in that: Also included is a controller, a first temperature sensor, and a second temperature sensor; The first temperature sensor is used to collect the inlet temperature of the heat exchange component; The second temperature sensor is used to collect the outlet temperature of the heat exchange component; The controller is used to determine the change value of the heat exchange efficiency of the heat exchanger based on the inlet temperature and the outlet temperature. If the change value of the heat exchange efficiency indicates a decrease and is greater than a preset threshold, it is determined that there is a blockage in the low-temperature circulation loop between the heat exchange component and the heat collection component.

7. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 6, characterized in that: Also included is a vibration device; The vibration device is arranged on at least one of the low-temperature circulation pipe of the low-temperature circulation loop, the low-temperature heat storage component and the low-temperature circulation component; The controller is further configured to control the vibration device to vibrate.

8. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 7, characterized in that: The controller is further configured to determine a degree of blockage based on a change in the heat exchange efficiency when determining that the low-temperature circulation loop is blocked, and determine vibration parameters of the vibration device based on the degree of blockage.

9. The heat storage system based on the alkali metal chloride solid solution composite phase change material according to claim 7, characterized in that: Also includes: The controller is further configured to control the vibration device to vibrate for a preset time period, and if the change in heat exchange efficiency is still greater than a preset threshold, send an instruction to stop heat exchange.

10. A heat storage method based on an alkali metal chloride solid solution composite phase change material, characterized in that: The method applied to the heat storage system of the alkali metal chloride solid solution composite phase change material according to any one of claims 1 to 9 comprises: Placing raw materials in the dissolution tank of the heat storage system and stirring them with the stirrer of the heat storage system to prepare a precursor slurry; wherein the raw materials include NaCl, KCl and deionized water; Dehydrating the precursor slurry using the temperature control component of the heat storage system to obtain a precursor powder, and heating the precursor powder according to a set heating strategy and cooling strategy, and then cooling it to obtain an original alkali metal chloride solid solution; The original alkali metal chloride solid solution is ground using the grinder of the heat storage system to obtain a ground alkali metal chloride solid solution, wherein the ground alkali metal chloride solid solution is filled into the heat collection component in the heat storage device of the heat storage system to complete heat storage and heat exchange.

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