Heat storage body, heat storage device, and heat storage system

Abstract

To provide a heat storage body that can inhibit corrosion of graphite.SOLUTION: A heat storage body 10 is employed that comprises a base body 1 made of graphite and metal particles 4 filled inside the base body, the surface of the metal particles 4 being provided with a coating layer composed of one or both of carbon and ceramics.SELECTED DRAWING: Figure 1D

Description

[Technical Field]

[0001] The present invention relates to a heat storage medium, a heat storage device, and a heat storage system. [Background technology]

[0002] To realize a decarbonized society, there is a shift from fossil fuels to renewable natural energy sources such as solar, wind, wave, and geothermal. The output of these natural energy sources is greatly affected by natural conditions. For example, when generating electricity from natural energy sources, it is considered difficult to control output in response to fluctuating power demand.

[0003] Therefore, when there is an excess of energy supply, it is possible to store the surplus energy as thermal energy, and when there is a shortage of energy supply, the stored thermal energy can be extracted and sent to a steam turbine or the like to generate electricity, and heat storage technology for this purpose is being developed.

[0004] Patent Documents 1 and 2 describe heat storage devices that use graphite, which has excellent thermal conductivity and heat storage properties, as a heat storage medium.

[0005] Patent Document 3 describes a heat storage device that includes a heat medium that absorbs solar heat and a phase change medium that exchanges heat with the heat medium, and uses oil or the like as the heat medium and lithium nitrate as the phase change medium, thereby storing and releasing thermal energy using latent heat and sensible heat generated when the phase change medium changes from solid to liquid.

[0006] Patent Document 4 describes a heat storage device equipped with a heat storage material containing graphite and nitrate, which is a phase change material.

[0007] Patent Documents 5 and 6 describe an energy storage device having a graphite compact and a phase change material housed inside the compact. The phase change material is a metal such as aluminum, which has a high melting point. Patent Documents 5 and 6 describe that a high-temperature heat transfer fluid is obtained, and high thermal efficiency can be achieved in power generation using a Brayton cycle or the like.

[0008] The energy storage devices described in Patent Documents 5 and 6, which have a graphite compact and a phase change material housed inside the compact, use a metal such as aluminum, which has a relatively high melting point, as the phase change material, and are therefore capable of use at higher temperatures than non-metallic phase change materials. However, the graphite compact is manufactured by molding graphite into a bulk form, and because graphite is a porous material with many pores, there is a risk that when the aluminum serving as the phase change material liquefies, it will penetrate the pores of the graphite and corrode the graphite.

[0009] Non-Patent Document 1 describes the reactivity of graphite with liquid metals, and states that aluminum and magnesium, which are used as phase-change materials, corrode graphite when they come into contact with graphite in a liquid state, i.e., there is a risk that graphite may be eroded. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2023 / 049136 [Patent Document 2] Japanese Patent Application Publication No. 2017-036841 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-47992 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-48943 [Patent Document 5] Special Publication No. 2023-509299 [Patent Document 6] International Publication No. 2023 / 115098 [Non-patent literature]

[0011] [Non-Patent Document 1] "<Reference> Compatibility of Graphite with Metals", Kingo Sudo, Bulletin of the Tohoku University Mineral Dressing and Smelting Research Institute, Vol. 19, No. 1, pp. 69-78, published October 28, 1963 (URL: http: / / hdl.handle.net / 10097 / 32443) Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a heat storage medium, a heat storage device, and a heat storage system that can suppress corrosion of graphite. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention employs the following configuration. [1] A substrate made of graphite; metal particles filled inside the substrate, A heat storage body, wherein the surfaces of the metal particles are provided with a coating layer made of either or both of carbon and ceramics. [2] The heat storage medium according to [1], wherein the coating layer is a two-layer coating layer in which carbon and ceramics are laminated in this order from the surface side of the metal particles, or a three-layer coating layer in which carbon, ceramics, and carbon are laminated in this order. [3] The heat storage medium according to [2], wherein the ceramic is any one of silicon carbide, zirconium carbide, and silicon dioxide. [4] The heat storage medium according to [1], wherein the metal particles are one or more of aluminum, aluminum alloy, magnesium, magnesium alloy, manganese, manganese alloy, copper, copper alloy, zinc, zinc alloy, silicon, and silicon alloy. [5] The heat storage medium according to any one of [1] to [4], an electric heater that is installed inside the base of the heat storage body and heats the heat storage body by passing electricity; The heat storage device, wherein the base of the heat storage body is provided with a plurality of through holes that pass through the base in the axial direction and allow a heat transfer fluid to flow therethrough. [6] The heat storage medium according to any one of [1] to [4] is provided, The heat storage device, wherein the base of the heat storage body is provided with a plurality of through holes that pass through the base in the axial direction and allow a heat transfer fluid to flow therethrough. [7] The heat storage device according to [5], an external power source capable of energizing the electric heating body provided in the heat storage device; A heat exchanger; a fluid circulation mechanism that circulates a heat transfer medium fluid between the heat storage device and the heat exchanger; a control unit that controls the external power source to energize the electric heating body of the heat storage device during heat storage, and the fluid circulation mechanism to circulate the heat medium fluid between the heat storage body and the heat exchanger during heat release; A heat storage system comprising: [8] A plurality of the heat storage devices are provided, The heat storage system according to [7], wherein each of the heat storage devices is connected in parallel to the heat exchanger. [9] The heat storage device according to [6], an external heat source for heating the first heat transfer fluid; A heat exchanger; a fluid supply mechanism that supplies a first heat medium fluid from the external heat source to the heat storage device; a fluid circulation mechanism that circulates a second heat medium fluid between the heat storage device and the heat exchanger; a control unit that controls the fluid supply mechanism to supply the first heat medium fluid heated in the external heat source to the heat storage device during heat storage, and controls the fluid circulation mechanism to circulate the second heat medium fluid between the heat storage device and the heat exchanger during heat release; A thermal storage system comprising:

[10] A plurality of the heat storage devices are provided, [9] The heat storage system according to [9], wherein each of the heat storage devices is connected in parallel to the external heat source and connected in parallel to the heat exchanger. [Effects of the Invention]

[0014] According to the present invention, even if metal particles contained in a substrate made of graphite are liquefied, the coating layer prevents the liquefied metal from coming into contact with the graphite, thereby suppressing erosion of the graphite, and a highly reliable heat storage body, heat storage device, and heat storage system can be provided. [Brief explanation of the drawings]

[0015] [Figure 1A] 1 is a cross-sectional view showing a metal particle provided in a heat storage body according to a first embodiment of the present invention; [Figure 1B] 1 is a cross-sectional view showing a metal particle provided in a heat storage body according to a first embodiment of the present invention; [Figure 1C] FIG. 4 is a schematic perspective view showing a heat storage device according to a second embodiment of the present invention. [Figure 1D] FIG. 1D is a diagram showing a heat storage device according to a second embodiment of the present invention, and is a cross-sectional schematic diagram taken along line AA' in FIG. 1C. [Figure 2A] FIG. 4 is a schematic perspective view showing a heat storage device according to a third embodiment of the present invention. [Figure 2B] FIG. 2B is a diagram showing a heat storage device according to a third embodiment of the present invention, and is a cross-sectional schematic diagram taken along line AA' in FIG. 2A. [Figure 3] FIG. 10 is a schematic diagram showing the configuration of a heat storage system according to a fourth embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing the configuration of a heat storage system according to a fifth embodiment of the present invention. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of a heat storage system according to a sixth embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of a heat storage system according to a seventh embodiment of the present invention. [Figure 7] FIG. 13 is a schematic diagram showing the configuration of a heat storage system according to an eighth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a heat storage medium, a heat storage device, and a heat storage system according to embodiments of the present invention will be described with reference to the drawings.

[0017] (First embodiment: heat storage body) The heat storage body of this embodiment comprises a substrate made of graphite and metal particles filled inside the substrate, and the surface of the metal particles is provided with a coating layer made of either carbon or ceramics, or both.

[0018] The graphite substrate is composed of graphite lumps, and specifically, a graphite block can be exemplified. The shape of the substrate is not particularly limited, and examples thereof include a rectangular pillar shape and a cylindrical shape. Graphite has high thermal stability and thermal conductivity, making it suitable as a material for a heat storage body such as that of this embodiment. Metal particles coated with a coating layer are held in a dispersed state inside the graphite substrate.

[0019] As will be described later, the graphite substrate is produced, for example, by calcining polyphenyl, polyphenyl ether or a derivative thereof, or by calcining low molecular weight pitch.

[0020] The metal particles absorb and store heat during heat storage, and release the stored heat during heat release. It is preferable that the metal particles change phase (solid or liquid) when absorbing or releasing heat. A material that changes phase when absorbing or releasing heat can store or release a large amount of thermal energy. Furthermore, it is preferable that the metal particles have a higher melting point and excellent thermal conductivity than non-metallic phase-change materials such as inorganic salts and organic substances.

[0021] The metal particles are preferably one or more of aluminum, aluminum alloy, magnesium, magnesium alloy, manganese, manganese alloy, copper, copper alloy, zinc, zinc alloy, silicon, or silicon alloy. Aluminum or aluminum alloy is preferred, and aluminum is more preferred.

[0022] The average equivalent circle diameter of the metal particles is not particularly limited, but is preferably in the range of, for example, 0.5 mm to 5 mm.

[0023] The content of the metal particles relative to the graphite substrate is not particularly limited, but is preferably in the range of 10% to 50% by volume, for example.

[0024] Next, the coating layer that coats the metal particles will be described. The coating layer is made of either carbon or ceramic, or both. That is, the coating layer may be made of a carbon layer, a ceramic layer, or a laminate of a carbon layer and a ceramic layer.

[0025] In particular, as the coating layer 5 in which a carbon layer and a ceramic layer are laminated, a two-layer coating layer in which a carbon layer 6 and a ceramic layer 7 are laminated in this order from the surface side of the metal particle 4, as shown in Fig. 1A, is preferred. Also, as the coating layer 5, a three-layer coating layer in which a carbon layer 6, a ceramic layer 7, and a carbon layer 6 are laminated in this order from the surface side of the metal particle 4, as shown in Fig. 1B, is preferred.

[0026] The ceramics that make up the coating layer are stable and have sufficient coating effect even at high temperatures of 1000°C or higher. The ceramic is preferably one of silicon carbide, zirconium carbide, and silicon dioxide. By providing a coating layer made of these ceramics, metal particles that liquefy during heat storage are prevented from leaking out of the coating layer, and erosion of the graphite that makes up the base can be prevented.

[0027] The thickness of the ceramic layer is not particularly limited whether the ceramic layer is used as a single layer or laminated with a carbon layer, but is preferably in the range of 20 μm to 200 μm, for example.

[0028] The carbon constituting the coating layer is preferably pyrolytic carbon. For example, pyrolytic carbon produced by pyrolyzing hydrocarbons such as acetylene is preferable. Pyrolytic carbon has a density of, for example, 0.7 g / cm. 3 More than 2.1g / cm 3 The following is good:

[0029] Among pyrolytic carbons, those with a relatively low density can absorb volume changes when metal particles undergo volume changes. Therefore, when the volume of metal particles expands or contracts during heat storage or heat release, the stress applied to the graphite substrate can be alleviated, and cracking or breakage of the graphite substrate can be suppressed. To achieve this effect, the density of pyrolytic carbon must be 0.7 g / cm 3 More than 1.2g / cm 3 It would be better if it was below.

[0030] On the other hand, pyrolytic carbon with a relatively high density is expected to be able to prevent the metal particles that liquefy during heat storage from leaking out of the coating layer, as with ceramics, and to suppress corrosion of the graphite that constitutes the substrate. In order to achieve this effect, the density of pyrolytic carbon must be 1.5 g / cm 3 More than 2.1g / cm 3 It would be better if it was below.

[0031] The thickness of the inner or outer carbon layer is preferably in the range of, for example, 20 to 100 μm. Also, when the coating layer is a single carbon layer, the thickness of the carbon layer may be in the above range.

[0032] The two-layer coating, that is, the coating layer in which carbon and ceramics are laminated in this order from the surface side of the metal particle, has an inner carbon layer with a density of 0.7 g / cm 3 More than 1.2g / cm 3By using the following pyrolytic carbon, the carbon layer can mitigate the volume change of the metal particles that accompanies expansion or contraction during heat storage or heat release, and the ceramic layer can prevent the metal particles that have turned into liquid during heat storage from leaking out.

[0033] The three-layer coating, that is, the coating layer stacked in the order of carbon, ceramics, and carbon from the surface side of the metal particle, has an inner carbon layer with a density of 0.7 g / cm 3 More than 1.2g / cm 3 The outer carbon layer is made of pyrolytic carbon with a density of 1.5 g / cm 3 More than 2.1g / cm 3 By using the following pyrolytic carbon, the inner carbon layer can mitigate the volume change of the metal particles that accompanies expansion or contraction during heat storage or heat release, and the ceramic layer and outer carbon layer can prevent the metal particles that turn into liquid during heat storage from leaking out to the outside.

[0034] The heat storage body of this embodiment is manufactured, for example, by mixing metal particles with a coating layer and a graphite raw material, such as polyphenyl, polyphenyl ether, or a derivative thereof, or low-molecular-weight pitch, and then firing the mixture. The graphite raw material is graphitized by firing to form a substrate. At this time, the metal particles can be contained in a dispersed state inside the substrate.

[0035] Examples of methods for forming a coating layer on metal particles include the following methods.

[0036] To coat metal particles with a carbon layer, the metal particles are placed in a reaction vessel, the vessel is heated to 500-600°C, and then acetylene and argon gases are injected from a gas inlet nozzle installed in the reaction vessel as coating source gases. The acetylene gas is pyrolyzed while the metal particles are flowing, resulting in the deposition of pyrolytic carbon on the surface of the metal particles. The density of the pyrolytic carbon can be adjusted by controlling the flow rate ratio of acetylene gas to argon gas. In addition to acetylene gas, a mixed gas of acetylene and propylene can also be used as the coating source gas.

[0037] To coat metal particles with a ceramic layer, the metal particles are placed in a reaction vessel, the vessel is heated to 1000 to 1700°C, and methyltrichlorosilane is supplied as a coating source gas from a gas inlet nozzle installed in the reaction vessel, thereby adhering silicon carbide as a ceramic to the surface of the metal particles. To form zirconium carbide, zirconium bromide and methane are preferably used as the coating source gas. To form silicon dioxide, the metal particles may be immersed in an organosilane solution such as tetraethoxysilane at room temperature to 60°C and reacted to adhere silicon dioxide to the surface of the metal particles.

[0038] As described above, according to the heat storage medium of this embodiment, by forming a coating layer including at least a ceramic layer or a carbon layer on the surface of the metal particles, it is possible to prevent the metal particles that liquefy during heat storage from leaking to the base and to suppress corrosion of the graphite that constitutes the base. Furthermore, by forming a coating layer including a carbon layer, it is possible to alleviate the stress applied to the base when the metal particles expand in volume during heat storage, and to prevent damage to the base.

[0039] (Second embodiment) Next, a heat storage device according to a second embodiment will be described. As shown in Figures 1C and 1D, the heat storage device 101 of this embodiment is equipped with a heat storage body 10 and an electric heating body 2 that is installed inside a base 1 that constitutes the heat storage body 10 and heats the heat storage body 10 when electricity is passed through it, and is configured so that the base 1 that constitutes the heat storage body 10 is provided with a plurality of through holes 3 that penetrate the base 1 in the axial direction and allow a heat transfer medium fluid to flow through.

[0040] The axial direction of the base 1 refers to the height direction of the prism or cylinder when the base 1 has a prismatic or cylindrical shape. When the base 1 has a shape other than a prismatic or cylindrical shape, the axial direction refers to the longitudinal direction when the base 1 is viewed as a whole.

[0041] Similar to the heat storage body of the first embodiment, the heat storage body 10 is composed of a substrate 1 made of graphite and metal particles 4 contained inside the substrate 1. Similar to the first embodiment, the surfaces of the metal particles 4 are provided with a coating layer (not shown).

[0042] 1C and 1D, the electric heating element 2 is rod-shaped, for example. The electric heating element 2 is inserted into the base 1 so that its longitudinal direction is along the axial direction of the base 1 constituting the thermal storage body 10. A plurality of electric heating elements 2 are provided, and the electric heating elements 2 are arranged at regular intervals.

[0043] The electric heater 2 is preferably made of a material that generates heat when electricity is applied, such as a nickel-chromium alloy.

[0044] The through holes 3 are provided so as to penetrate the base 1. For example, as shown in FIGS. 1C and 1D, the through holes 3 penetrate the base 1 so that their longitudinal direction is along the axial direction of the base 1 constituting the heat storage body 10. The through holes 3 open to the front surface 1a of the base 1 on one side in the axial direction of the base 1, and this opening serves as an inlet 3a for the heat transfer medium fluid. The through holes 3 also open to the back surface opposite the front surface 1a on the other side in the axial direction of the base 1, and this opening serves as an outlet for the heat transfer medium fluid.

[0045] In FIGS. 1C and 1D, the cross-sectional shape of the through-hole 3 is circular, but there are no particular limitations on the cross-sectional shape, and it may be any of elliptical, rectangular, and triangular.

[0046] A heat transfer fluid can be passed through the through holes 3. As the heat transfer fluid, one type of inert gas selected from nitrogen, helium, argon, and carbon dioxide can be used to prevent oxidation of the graphite.

[0047] The operation of the heat storage device 101 of this embodiment will be described. During heat storage, electricity is applied to the electric heater 2 from an external power source, causing the electric heater 2 to generate heat. The generated heat propagates through the graphite constituting the base 1, reaches the metal particles 4, and raises the temperatures of the graphite and the metal particles 4. The metal particles 4 have a larger heat capacity per unit volume than graphite, so they can store a large amount of heat. The metal particles 4 may also be melted and liquefied by heat. Because the metal particles 4 are provided with a coating layer, even if the metal particles 4 liquefy, they remain inside the coating layer and do not come into contact with the graphite constituting the base 1, thereby suppressing corrosion of the graphite. Therefore, the heat storage device 101 of this embodiment can store a larger amount of heat than conventional heat storage devices that do not have a coating layer.

[0048] Next, during heat dissipation, a relatively low-temperature heat transfer fluid is introduced into the through holes 3 from the inlet 3a of the through holes 3, circulates inside the heat storage device 101, and then is discharged from the outlet. The heat transfer fluid introduced from the inlet 3a needs to be at a temperature lower than that of the graphite and metal particles 4 in the heat storage state. While the heat transfer fluid flows through the through holes 3, heat exchange occurs between the heat transfer fluid and the graphite and metal particles 4 in the heat storage state, and the temperature of the heat transfer fluid increases while the temperatures of the graphite and metal particles 4 decrease. The high-temperature heat transfer fluid is then taken out from the outlet.

[0049] More specifically, for example, during heat storage, surplus electricity from natural energy or the like is used to energize the electric heater 2, generating heat and heating the metal particles 4 above their melting point, thereby storing heat. During heat release, a low-temperature heat transfer fluid is introduced into the through holes 3, and a high-temperature heat transfer fluid is extracted. This is then sent to, for example, an external heat exchanger, generating high-temperature steam. Then, by using the high-temperature steam, it is possible to generate electricity using a steam turbine or a gas turbine.

[0050] (Third embodiment) Next, a heat storage device 201 according to a third embodiment will be described. 2A and 2B, the heat storage device 201 of this embodiment is provided with a heat storage body 10, and is configured such that a base 1 constituting the heat storage body 10 is provided with a plurality of through holes 13 that penetrate the base 1 in the axial direction and allow a heat transfer fluid to circulate. The axial direction of the base 1 is the same as in the second embodiment.

[0051] Similar to the heat storage body of the first embodiment, the heat storage body 10 is composed of a substrate 1 made of graphite and metal particles 4 contained inside the substrate 1. Similar to the first embodiment, the surfaces of the metal particles 4 are provided with a coating layer.

[0052] The through hole 13 has the same configuration as the through hole 3 of the second embodiment, and penetrates the base 1 so that its longitudinal direction is along the axial direction of the base 1 constituting the heat storage body 10. The through hole 13 has an inlet 13a for the heat transfer fluid on one side in the axial direction of the base 1, and has an outlet 13a for the heat transfer fluid on the other side in the axial direction, that is, on the back surface opposite to the front surface 1a.

[0053] A heat transfer fluid can flow through the through holes 13. As the heat transfer fluid, one type of inert gas selected from nitrogen, helium, argon, and carbon dioxide can be used to prevent oxidation of the graphite.

[0054] The operation of the heat storage device 201 of this embodiment will be described. During heat storage, a relatively high-temperature heat transfer fluid is introduced into the through holes 13, circulated inside the heat storage device 201, and then discharged from the outlet. The heat transfer fluid introduced from the inlet 13a needs to be at a higher temperature than the temperature of the graphite and metal particles 4 before heat storage.

[0055] While the high-temperature heat transfer fluid flows through the through holes 13, heat exchange occurs between the graphite and the metal particles 4, which are in a state before heat storage. The heat of the heat transfer fluid propagates through the graphite that constitutes the base 1, reaches the metal particles 4, and raises the temperature of the graphite and the metal particles 4. The metal particles 4 have a larger heat capacity per unit volume than graphite, so they can store a large amount of heat. The metal particles 4 may also be melted and liquefied by heat. Because the metal particles 4 are provided with a coating layer, even if the metal particles 4 liquefy, they remain inside the coating layer and do not come into contact with the graphite that constitutes the base 1, thereby suppressing corrosion of the graphite. Therefore, the heat storage device 201 of this embodiment can store a larger amount of heat than conventional heat storage devices that do not have a coating layer.

[0056] Next, during heat dissipation, as in the second embodiment, a relatively low-temperature heat transfer fluid is introduced into the through holes 13 from the inlet 13a of the through holes 13, circulates through the heat storage device 201, and then is discharged from the outlet. The heat transfer fluid introduced from the inlet 13a needs to be at a temperature lower than that of the graphite and metal particles 4 in the heat storage state. While the heat transfer fluid flows through the through holes 13, heat exchange occurs between the heat transfer fluid and the graphite and metal particles 4 in the heat storage state, and the temperature of the heat transfer fluid increases while the temperatures of the graphite and metal particles 4 decrease. The high-temperature heat transfer fluid is then taken out from the outlet.

[0057] More specifically, for example, during heat storage, the heat storage device 201 uses surplus electricity from natural energy or the like to heat a heat transfer fluid, which is then circulated through the through-holes 13 to heat the metal particles 4 above their melting point, thereby storing heat. During heat release, low-temperature heat transfer fluid is introduced into the through-holes 13, and high-temperature heat transfer fluid is extracted and sent to, for example, an external heat exchanger to generate high-temperature steam. Then, by using the high-temperature steam, it becomes possible to generate electricity using a steam turbine or a gas turbine.

[0058] (Fourth embodiment) Next, a heat storage system 301 according to a fourth embodiment will be described. This heat storage system 301 includes the heat storage device 101 of the second embodiment.

[0059] That is, as shown in FIG. 3, a heat storage system 301 of this embodiment includes a heat storage device 101, an external power supply 302, a heat exchanger 303, a fluid circulation mechanism 304, and a control unit 305.

[0060] The external power supply 302 supplies power to the electric heating element 2 by energizing the electric heating element 2 of the thermal storage device 101 .

[0061] The heat exchanger 303 receives the heat medium fluid delivered from the heat storage device 101 as a primary fluid, and performs heat exchange between the heat medium fluid and a secondary fluid.

[0062] The fluid circulation mechanism 304 includes a flow path 304a and a pump (not shown). The flow path 304a is provided between the inlet 3a and outlet 3b of the through-hole 3 of the heat storage device 101 and the heat exchanger 303. The pump has a function of circulating the heat medium fluid between the heat storage device 101 and the heat exchanger 303.

[0063] The control unit 305 causes the external power source 302 to energize the electric heater 2 of the heat storage device 101 during heat storage, and causes the fluid circulation mechanism 304 to circulate the heat medium fluid between the heat storage device 101 and the heat exchanger 303 during heat release.

[0064] The operation of the heat storage system 301 will be described below. During heat storage, the control unit 305 issues a command to the external power supply 302, and the external power supply 302 supplies power to the electric heating element 2 to energize it. This causes heat to be stored in the heat storage device 101. The operation of storing heat in the heat storage device 101 is the same as that described in the second embodiment.

[0065] Next, during heat dissipation, the control unit 305 issues a command to the fluid circulation mechanism 304 to introduce a relatively low-temperature heat transfer fluid from the inlet 3a of the heat storage device 101 into the through-holes 3, circulate the heat storage device 101, and then discharge the heat transfer fluid from the outlet 3b. The discharged and heated heat transfer fluid is sent to the heat exchanger 303 via the flow path 304a, where heat exchange occurs between the discharged heat transfer fluid and a secondary fluid (e.g., water). The water as the secondary fluid becomes high-temperature steam through the heat exchange. Meanwhile, the heat transfer fluid cooled by the heat exchange is sent back to the heat storage device 101 via the flow path 304a.

[0066] According to the heat storage system 301 of this embodiment, when there is an excess of energy supply, the surplus energy is stored as thermal energy in the heat storage device 101, and when there is an insufficient energy supply, the thermal energy stored in the heat storage device 101 is extracted to generate steam in the heat exchanger 303, and the generated steam is sent to a steam turbine or the like to generate electricity.

[0067] (Fifth embodiment) Next, a heat storage system 401 according to a fifth embodiment will be described. This heat storage system 401 has a plurality of, specifically four, heat storage devices 101 connected in parallel to one heat exchanger 303.

[0068] 4, the heat storage system 401 of this embodiment includes four heat storage devices 101, external power supplies 302 connected to the heat storage devices 101, one heat exchanger 303, a fluid circulation mechanism 404, and a control unit (not shown). Of these, the heat storage devices 101, the external power supplies 302, the heat exchangers 303, and the control unit are as already described.

[0069] The fluid circulation mechanism 404 includes a flow path 404a and a pump (not shown). The flow path 404a is provided between the inlet 3a and the outlet 3b of each of the through holes 3 of the four heat storage devices 101 and the heat exchanger 303. The pump has a function of circulating the heat medium fluid between the heat storage devices 101 and the heat exchanger 303.

[0070] According to this heat storage system 401, similarly to the heat storage system 301 of the fourth embodiment, when there is an excess supply of energy, the surplus energy is stored as thermal energy in the heat storage device 101, and when there is a shortage of energy supply, the thermal energy stored in the heat storage device 101 is extracted to generate steam in the heat exchanger 303, and the generated steam can be sent to a steam turbine or the like to generate electricity.

[0071] (Sixth embodiment) Next, a heat storage system 501 according to a sixth embodiment will be described. This heat storage system 501 includes the heat storage device 201 of the third embodiment.

[0072] That is, as shown in FIG. 5, the heat storage system 501 of this embodiment includes a heat storage device 201, an external heat source 502, a fluid supply mechanism 503 that supplies a first heat medium fluid from the external heat source 502 to the heat storage device 201, a heat exchanger 303, a fluid circulation mechanism 304, and a control unit 505.

[0073] An external heat source 502 heats the first heat transfer fluid.

[0074] The fluid supply mechanism 503 includes a flow path 503a provided between the inlet 13a of the through hole 13 of the heat storage device 201 and the external heat source 502, and a pump (not shown) that supplies the first heat medium fluid from the external heat source 502 to the heat storage device 201.

[0075] The heat exchanger 303 receives the second heat medium fluid delivered from the heat storage device 201 as a primary fluid, and performs heat exchange between the second heat medium fluid and the secondary fluid.

[0076] The fluid circulation mechanism 304 includes a flow path 304a and a pump (not shown). The flow path 304a is provided between the inlet 13a and outlet 13b of the through-hole 13 of the heat storage device 201 and the heat exchanger 303. The pump has a function of circulating the second heat medium fluid between the heat storage device 201 and the heat exchanger 303.

[0077] The control unit 505 controls the fluid supply mechanism 503 to supply the first heat medium fluid heated in the external heat source 502 to the heat storage device 201 during heat storage, and controls the fluid circulation mechanism 304 to circulate the second heat medium fluid between the heat storage device 201 and the heat exchanger 303 during heat dissipation.

[0078] The operation of the heat storage system 501 will be described below. During heat storage, the control unit 505 issues a command to the external heat source 502 to heat the first heat medium fluid. The control unit 505 also issues a command to the fluid supply mechanism 503 to supply the heated first heat medium fluid to the heat storage device 201. This causes heat to be stored in the heat storage device 201. The operation of storing heat in the heat storage device 201 is the same as that described in the third embodiment.

[0079] Next, during heat dissipation, the control unit 505 issues a command to the fluid circulation mechanism 304 to introduce a relatively low-temperature second heat medium fluid from the inlet 13a of the heat storage device 201 into the through-holes 13, circulate through the heat storage device 201, and then discharge it from the outlet 13b. The discharged and heated second heat medium fluid is sent to the heat exchanger 303 via the flow path 304a, where heat exchange occurs between the discharged second heat medium fluid and a secondary fluid (e.g., water). The water as the secondary fluid becomes high-temperature steam through the heat exchange. Meanwhile, the second heat medium fluid, cooled by the heat exchange, is sent back to the heat storage device 201 via the flow path 304a.

[0080] According to the heat storage system 501 of this embodiment, when there is an excess of energy supply, the surplus energy is stored as thermal energy in the heat storage device 201, and when there is an insufficient energy supply, the thermal energy stored in the heat storage device 201 is extracted to generate steam in the heat exchanger 303, and the generated steam is sent to a steam turbine or the like to generate electricity.

[0081] (Seventh embodiment) Next, a heat storage system 601 according to a seventh embodiment will be described. This heat storage system 601 has a plurality of, specifically four, heat storage devices 201 connected in parallel to one heat exchanger 303.

[0082] 6, the heat storage system 601 of this embodiment includes four heat storage devices 201, an external heat source 502 connected to each heat storage device 201, a fluid supply mechanism 503, one heat exchanger 303, a fluid circulation mechanism 504, and a control unit (not shown). Of these, the heat storage devices 201, the external heat source 502, the fluid supply mechanism 503, the heat exchanger 303, and the control unit are as already described.

[0083] The fluid circulation mechanism 504 includes a flow path 504a and a pump (not shown). The flow path 504a is provided between the inlet 13a and the outlet 13b of each of the through holes 13 of the four heat storage devices 201 and the heat exchanger 303. The pump has a function of circulating the second heat medium fluid between the heat storage devices 201 and the heat exchanger 303.

[0084] According to this heat storage system 601, similarly to the heat storage system 501 of the sixth embodiment, when there is an excess supply of energy, the surplus energy is stored as thermal energy in the heat storage device 201, and when there is a shortage of energy supply, the thermal energy stored in the heat storage device 201 is extracted to generate steam in the heat exchanger 303, and the generated steam can be sent to a steam turbine or the like to generate electricity.

[0085] (Eighth embodiment) Next, a heat storage system 701 according to an eighth embodiment will be described. This heat storage system 701 has almost the same configuration as the heat storage system 401 of the fifth embodiment, but differs in that a double pipe is used as the flow path of the fluid circulation mechanism.

[0086] As shown in FIG. 7, the heat storage device 101 and the heat exchanger 303 are connected by a double pipe 704 .

[0087] The double pipe 704 is composed of an inner pipe 704a and an outer pipe 704b having a larger diameter than the inner pipe 704a. The inner pipe 704a is inserted inside the outer pipe 704b.

[0088] The internal space of the inner pipe 704a is a high-temperature side flow path through which a high-temperature heat medium flows, while the space between the inner pipe 704a and the outer pipe 704b is a low-temperature side flow path through which a low-temperature heat medium flows.

[0089] The high-temperature side flow path is configured so that a heat transfer medium fluid heated by the heat storage device 101 flows, while the low-temperature side flow path is configured so that a low-temperature heat transfer medium fluid flows after heat exchange in the heat exchanger 303.

[0090] According to this embodiment, by using a double pipe 704 as a flow path of the fluid circulation mechanism, the inner pipe 704a through which the heated heat transfer fluid flows is covered by the outer pipe 704b, and the inner pipe 704a is not directly exposed to the outside air, thereby suppressing heat loss between the heat storage device 101 and the heat exchanger 303.

[0091] The use of double pipes as the flow paths of the fluid circulation mechanism is not limited to this embodiment, and may also be applied to fluid circulation mechanisms of other embodiments.

[0092] As described above in some embodiments, according to the present invention, a heat storage medium including graphite and metal particles whose surfaces are coated with ceramic or carbon can prevent erosion of the graphite even when the metal particles are liquefied during heat storage, and it is possible to provide a heat storage medium, heat storage device, and heat storage system with a large heat storage capacity. [Example]

[0093] The present invention will be described in more detail below with reference to examples.

[0094] (Example) One kilogram of aluminum particles with an average particle size of 2 mm was prepared. The aluminum particles were placed in a reaction vessel, and the vessel was heated to 600°C. Then, acetylene gas and argon gas were injected from a gas inlet nozzle at the bottom of the vessel. The aluminum particles were fluidized while the acetylene gas was pyrolyzed, depositing carbon atoms onto the surface of the aluminum particles. The flow rate ratio of acetylene gas to argon gas (C2H2 / (C2H2+Ar)) was set to 0.5, and this mixed gas was supplied into the reaction vessel for 60 seconds, forming a layer of pyrolytic carbon on the surface of the aluminum particles.

[0095] Next, the aluminum particles coated with a layer of pyrolytic carbon were immersed in a tetraethoxysilane solution and then heated and dried, thereby coating the surface of the pyrolytic carbon layer with a ceramic layer of silicon dioxide.

[0096] In this way, coated particles were produced in which a carbon layer and a ceramic layer were laminated on the surface of an aluminum particle, as shown in Figure 1A. The thickness of the pyrolytic carbon layer was 60 μm, and the density of the pyrolytic carbon layer was 1.0 g / cm. 3 The thickness of the layer made of silicon dioxide (ceramics) was 50 μm.

[0097] Furthermore, the coated particles obtained in the above process were mixed with polyphenyl ether and then fired to produce a heat storage body of the example in which the coated particles were dispersed inside the graphite substrate. The coated particles were filled into the substrate so as to be in the range of 10% to 50% by volume.

[0098] (Comparative Example) 1 kg of aluminum particles with an average particle size of 2 mm was prepared. These aluminum particles were mixed with polyphenyl ether and then fired to produce a comparative example of a heat storage medium in which the aluminum particles were dispersed inside a graphite substrate. The aluminum particles were filled into the substrate so that the volume percentage was in the range of 10% to 50%.

[0099] The manufactured heat storage bodies of the example and comparative example were used to configure the heat storage systems shown in Fig. 3. Then, for the heat storage systems of the example and comparative example, the state of the aluminum particles after repeated heat storage and heat release was investigated by the following method.

[0100] In the heat storage process, the heat storage body was heated to 1000°C by electrical heating to melt the aluminum. Next, in the heat release process, nitrogen gas was introduced into the heat storage body from the heat exchanger and circulated, and the heat exchanger was operated for 12 hours. During this time, the temperature of the heat storage body dropped to 400°C. This heat storage process and heat release process constitute one cycle, and this cycle was repeated 20 times. After that, the heat storage body was cooled and cut to observe the state of the aluminum particles in the cross section.

[0101] In the heat storage material of the example, even after repeated cycles of heat storage and heat release, no voids were observed between the coated particles and the graphite substrate, and no penetration of aluminum into the graphite was confirmed.

[0102] On the other hand, in the heat storage material of the comparative example, after repeated cycles of heat storage and heat release, voids were observed between the aluminum particles and the graphite substrate, which is thought to be due to the penetration of molten aluminum into the graphite.

[0103] From the above, it was confirmed that the coating layer was effective in preventing leakage of molten aluminum. [Explanation of symbols]

[0104] 1...base, 2...electric heating element, 3, 13 through holes, 4...metal particles, 5...coating layer, 6...layer made of carbon, 7...layer made of ceramic, 10...heat storage element, 101...heat storage device, 301, 401, 501, 601, 701...heat storage system, 302...external power source, 303...heat exchanger, 304, 404, 504...fluid circulation mechanism, 305, 505...control unit, 502...external heat source, 503...fluid supply mechanism.

Claims

1. a substrate made of graphite; metal particles filled inside the substrate, A heat storage body, wherein the surfaces of the metal particles are provided with a coating layer made of either or both of carbon and ceramics.

2. The heat storage medium according to claim 1, wherein the coating layer is a two-layer coating layer in which carbon and ceramics are laminated in that order from the surface side of the metal particles, or a three-layer coating layer in which carbon, ceramics, and carbon are laminated in that order.

3. 3. The heat storage medium according to claim 2, wherein the ceramic is any one of silicon carbide, zirconium carbide, and silicon dioxide.

4. The heat storage medium according to claim 1, wherein the metal particles are one or more of aluminum, aluminum alloy, magnesium, magnesium alloy, manganese, manganese alloy, copper, copper alloy, zinc, zinc alloy, silicon, and silicon alloy.

5. The heat storage material according to any one of claims 1 to 4, an electric heater that is installed inside the base of the heat storage body and heats the heat storage body by passing electricity; The heat storage device, wherein the base of the heat storage body is provided with a plurality of through holes that pass through the base in the axial direction and allow a heat transfer fluid to flow therethrough.

6. The heat storage medium according to any one of claims 1 to 4 is provided, The heat storage device, wherein the base of the heat storage body is provided with a plurality of through holes that pass through the base in the axial direction and allow a heat transfer fluid to flow therethrough.

7. The heat storage device according to claim 5; an external power source capable of energizing the electric heating body provided in the heat storage device; A heat exchanger; a fluid circulation mechanism that circulates a heat transfer medium fluid between the heat storage device and the heat exchanger; a control unit that controls the external power source to energize the electric heating body of the heat storage device during heat storage, and the fluid circulation mechanism to circulate the heat medium fluid between the heat storage body and the heat exchanger during heat release; A heat storage system comprising:

8. A plurality of the heat storage devices are provided, The thermal storage system according to claim 7 , wherein each of the thermal storage devices is connected in parallel to the heat exchanger.

9. The heat storage device according to claim 6; an external heat source for heating the first heat transfer fluid; A heat exchanger; a fluid supply mechanism that supplies a first heat medium fluid from the external heat source to the heat storage device; a fluid circulation mechanism that circulates a second heat medium fluid between the heat storage device and the heat exchanger; a control unit that controls the fluid supply mechanism to supply the first heat medium fluid heated by the external heat source to the heat storage device during heat storage, and controls the fluid circulation mechanism to circulate the second heat medium fluid between the heat storage device and the heat exchanger during heat release; A thermal storage system comprising:

10. A plurality of the heat storage devices are provided, The thermal storage system according to claim 9 , wherein each of the thermal storage devices is connected in parallel to the external heat source and to the heat exchanger.

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