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

Abstract

Provided is a heat storage body capable of suppressing the corrosion of graphite. 【Solution means】The heat storage body 10 is adopted, which includes a substrate 1 made of graphite and metal particles 4 filled inside the substrate, and a coating layer made of either one or both of carbon and ceramics is provided on the surface of the metal particles 4.

Description

Technical Field

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

Background Art

[0002] For the realization of a decarbonized society, the conversion from fossil fuels to renewable natural energy such as sunlight, wind power, wave power, or geothermal energy is in progress. The output of these natural energies is greatly affected by natural conditions. Therefore, for example, in power generation derived from natural energy, it is considered difficult to control the output according to the fluctuating power demand.

[0003] Therefore, when the energy supply is excessive, the surplus energy is stored as thermal energy, and when the energy supply is insufficient, the stored thermal energy is taken out and sent to a steam turbine or the like for power generation. For this purpose, the development of heat storage technology is underway.

[0004] Patent Documents 1 and 2 describe a heat storage device that uses graphite, which is excellent in thermal conductivity and heat storage properties, as a heat storage body.

[0005] Patent Document 3 includes a heat medium that absorbs solar heat and a phase change medium that exchanges heat with the heat medium. By using oil or the like as the heat medium and lithium nitrate as the phase change medium, a heat storage device that stores and releases thermal energy by the latent heat and sensible heat during the solid-liquid phase change of the phase change medium is described.

[0006] Patent Document 4 describes a heat storage device including a heat storage material containing graphite and a nitrate that is a phase change material.

[0007] Patent Documents 5 and 6 describe an energy storage device having a molded body made of graphite and a phase change material housed inside the molded body. As the phase change material, a metal such as aluminum with a high melting point is used. Patent Documents 5 and 6 describe that a high-temperature heat medium fluid can be obtained and high thermal efficiency can be obtained in power generation such as a Brayton cycle.

[0008] The energy storage device described in Patent Documents 5 and 6, which has a molded body made of graphite and a phase change material housed inside the molded body, uses a metal such as aluminum with a relatively high melting point as the phase change material, so it can be used at a higher temperature compared to non-metallic phase change materials. However, the molded body made of graphite is manufactured by molding graphite in a bulk state. Since graphite is a porous body having a large number of pores, when aluminum as the phase change material changes to a liquid state, there is a risk of it invading the pores of the graphite and corroding the graphite.

[0009] Non-Patent Document 1 describes the reactivity between graphite and liquid metal. Aluminum and magnesium used as phase change materials corrode graphite when they come into contact with graphite in a liquid state. That is, it is described that there is a risk of graphite being eroded.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0011] [Non-Patent Document 1] "<Reference> Compatibility of Graphite with Metals", Kingo Sudo, Bulletin of the Tohoku University Mineral Processing and Smelting Research Institute, Vol. 19, No. 1, p. 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 body, a heat storage device, and a heat storage system that are capable of suppressing 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; and metal particles filled inside the substrate, A heat storage medium, 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 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] 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] A heat storage material according to any one of [1] to [4], An electric heater installed inside the base of the heat storage body and configured to heat the heat storage body by energization. A heat storage device, wherein a plurality of through holes are provided in the base of the heat storage body so as to penetrate in the axial direction of the base and allow a heat transfer medium fluid to flow therethrough. [6] A heat storage system comprising the heat storage body according to any one of [1] to [4]. A heat storage device, wherein a plurality of through holes are provided in the base of the heat storage body so as to penetrate in the axial direction of the base and allow a heat transfer medium fluid to flow therethrough. [7] The heat storage device according to [5], and An external power source capable of energizing the electric heater provided in the heat storage device, A heat exchanger, A fluid circulation mechanism configured to circulate a heat transfer medium fluid between the heat storage device and the heat exchanger, A control unit configured to control the heat storage system such that during heat storage, the electric heater of the heat storage device is energized by the external power source, and during heat dissipation, the heat transfer medium fluid is circulated between the heat storage body and the heat exchanger by the fluid circulation mechanism. A heat storage system comprising the above components. [8] The heat storage system according to [7], wherein a plurality of the heat storage devices are provided, and each of the heat storage devices is connected in parallel to the heat exchanger. [9] The heat storage device according to [6], and An external heat source configured to heat a first heat transfer medium fluid, A heat exchanger, A fluid supply mechanism configured to supply the first heat transfer medium fluid heated by the external heat source to the heat storage device, A fluid circulation mechanism configured to circulate a second heat transfer medium fluid between the heat storage device and the heat exchanger, A control unit configured to control the heat storage system such that during heat storage, the first heat transfer medium fluid heated by the external heat source is supplied to the heat storage device by the fluid supply mechanism, and during heat dissipation, the second heat transfer medium fluid is circulated between the heat storage device and the heat exchanger by the fluid circulation mechanism. A heat storage system comprising the above components.

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

Advantages of the Invention

[0014] According to the present invention, even when the metal particles contained in the substrate made of graphite are liquefied, the coating layer can prevent the liquefied metal from coming into contact with the graphite, suppress the erosion of the graphite, and provide a highly reliable heat storage body, heat storage device, and heat storage system.

Brief Description of the Drawings

[0015]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0016] Hereinafter, a heat storage body, 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 includes a substrate made of graphite and metal particles filled inside the substrate, and a coating layer made of either one or both of carbon and ceramics is provided on the surface of the metal particles.

[0018] The substrate made of graphite is composed of a lump of graphite, and specifically, a block body made of graphite can be exemplified. The shape of the substrate is not particularly limited, and a prismatic or cylindrical shape can be exemplified. Graphite has high thermal stability and thermal conductivity and is suitable as a material for the heat storage body as in this embodiment. Inside the substrate made of graphite, the metal particles coated with the coating layer are held in a dispersed state.

[0019] As will be described later, the substrate made of graphite is manufactured, for example, by firing polyphenyl, polyphenyl ether or its derivative, or firing a low-molecular pitch.

[0020] The metal particles absorb and store heat during heat storage and release the stored heat during heat dissipation. The metal particles preferably change the phase (solid, liquid) when absorbing or releasing heat. Any material that changes the phase when absorbing or releasing heat can store or release a large amount of thermal energy. Also, the metal particles are preferably substances with a higher melting point than non-metal phase change substances such as inorganic salts and organic substances and excellent thermal conductivity.

[0021] Examples of the metal particles include one or more of aluminum, aluminum alloy, magnesium, magnesium alloy, manganese, manganese alloy, copper, copper alloy, zinc, zinc alloy, silicon, and silicon alloy. Preferably, it is aluminum or an aluminum alloy, and more preferably aluminum.

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

[0023] Also, the content of the metal particles with respect to the substrate made of graphite is not particularly limited, but for example, in terms of volume%, the range of 10% to 50% is preferred.

[0024] Next, the coating layer that coats the metal particles will be described. The coating layer is composed of either one or both of carbon and ceramics. That is, it may be a coating layer made of a carbon layer, a coating layer made of a ceramic layer, or a coating layer in which a carbon layer and a ceramic layer are laminated.

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

[0026] The ceramics constituting the coating layer are stable at a high temperature of 1000 ° C. or higher and have a sufficient coating effect. The ceramics are preferably any one of silicon carbide, zirconium carbide, and silicon dioxide. By providing a coating layer made of these ceramics, it is possible to prevent the metal particles liquefied during heat storage from flowing out of the coating layer and prevent the erosion of the graphite constituting the substrate.

[0027] The thickness of the ceramic layer is not particularly limited, whether the ceramic layer is used alone or laminated with the carbon layer. For example, a range of 20 μm to 200 μm is preferable.

[0028] The carbon constituting the coating layer is preferably pyrolytic carbon. As the pyrolytic carbon, for example, that generated by pyrolyzing hydrocarbons such as acetylene is preferable. The pyrolytic carbon has, for example, a density of 0.7 g / cm 3 or more and 2.1 g / cm 3 or less.

[0029] Among the pyrolytic carbons, those with a relatively low density can absorb the volume change when the metal particles undergo a volume change. Therefore, when the metal particles expand or contract in volume during heat storage or heat release, the stress applied to the graphite substrate can be relaxed, and cracking and damage of the graphite substrate can be suppressed. In order to exhibit such an effect, the density of the pyrolytic carbon is preferably 0.7 g / cm 3 or more and 1.2 g / cm 3 or less.

[0030] On the other hand, among the pyrolytic carbons, those with a relatively high density can, like the ceramics, prevent the liquefied metal particles from flowing out of the coating layer during heat storage, and it is expected to suppress the corrosion of the graphite constituting the substrate. In order to exhibit such an effect, the density of the pyrolytic carbon is preferably 1.5 g / cm 3 or more and 2.1 g / cm 3 or less.

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

[0032] The two-layer coating layer of the coating layer, that is, the coating layer laminated in the order of carbon and ceramics from the surface side of the metal particles, has an inner carbon layer with a density of 0.7 g / cm 3 or more and 1.2 g / cm 3By using the following pyrolytic carbon, the volume change of metal particles due to expansion or contraction during heat storage or heat release can be mitigated by the carbon layer, and the leakage of metal particles that have changed into a liquid during heat storage to the outside can be prevented by the ceramic layer.

[0033] Also, for the three-layer coating layer among the coating layers, that is, the coating layer laminated in the order of carbon, ceramic, and carbon from the surface side of the metal particles, the inner carbon layer has a density of 0.7 g / cm 3 or more and 1.2 g / cm 3 or less of pyrolytic carbon, and the outer carbon layer has a density of 1.5 g / cm 3 or more and 2.1 g / cm 3 or less of pyrolytic carbon. By doing so, the volume change of metal particles due to expansion or contraction during heat storage or heat release can be mitigated by the inner carbon layer, and the leakage of metal particles that have changed into a liquid during heat storage to the outside can be prevented by the ceramic layer and the outer carbon layer.

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

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

[0036] When coating the metal particles with a carbon layer, the metal particles are placed in a reaction vessel, the temperature inside the vessel is raised to 500 - 600 °C, and then acetylene gas as a coating raw material gas and argon gas are ejected from a gas introduction nozzle provided in the reaction vessel, and while the metal particles are being fluidized, pyrolytic carbon is attached to the surface of the metal particles by the thermal decomposition of acetylene gas. By controlling the flow rate ratio of acetylene gas and argon gas, the density of pyrolytic carbon can be adjusted. As the coating raw material gas, in addition to acetylene gas, a mixed gas of acetylene and propylene may be used.

[0037] When coating metal particles with a ceramic layer, the metal particles are placed in a reaction vessel, the temperature inside the vessel is raised to 1000 - 1700 °C, and then methyltrichlorosilane is supplied as a coating raw material gas from a gas introduction nozzle provided in the reaction vessel, so that silicon carbide as a ceramic adheres to the surface of the metal particles. When forming zirconium carbide, it is preferable to use zirconium bromide and methane as the coating raw material gas. Also, when forming silicon dioxide, the metal particles may be immersed in an organic silane solution such as tetraethoxysilane at room temperature - 60 °C and reacted, so that silicon dioxide adheres to the surface of the metal particles.

[0038] As described above, according to the heat storage body of the present embodiment, by forming a coating layer containing at least a ceramic layer or a carbon layer on the surface of the metal particles, it is possible to prevent the liquefied metal particles from leaking to the substrate during heat storage, and suppress the corrosion of the graphite constituting the substrate. Also, by forming a coating layer containing a carbon layer, when the metal particles expand in volume during heat storage, the stress applied to the substrate can be relaxed, preventing damage to the substrate.

[0039] (Second Embodiment) Next, the heat storage device of the second embodiment will be described. As shown in FIGS. 1C and 1D, the heat storage device 101 of the present embodiment includes a heat storage body 10 and an electric heater 2 installed inside the substrate 1 constituting the heat storage body 10 to heat the heat storage body 10 by energization, and a plurality of through holes 3 are provided in the substrate 1 constituting the heat storage body 10 so as to penetrate in the axial direction of the substrate 1 and allow a heat medium fluid to flow through.

[0040] Note that the axial direction of the substrate 1 is the height direction of the prism or cylinder when the shape of the substrate 1 is a prism or a cylinder. Also, when the shape of the substrate 1 is other than a prism or a cylinder, the axial direction is the longitudinal direction when looking at the entire shape of the substrate 1.

[0041] The heat storage body 10 is composed of a substrate 1 made of graphite and metal particles 4 included inside the substrate 1, similar to the heat storage body of the first embodiment. A coating layer (not shown) is provided on the surface of the metal particles 4, similar to the first embodiment.

[0042] The electric heating body 2 has, for example, a rod shape as shown in FIGS. 1C and 1D. The electric heating body 2 is inserted inside the substrate 1 such that its longitudinal direction is along the axial direction of the substrate 1 constituting the heat storage body 10. A plurality of electric heating bodies 2 are provided, and the electric heating bodies 2 are arranged at regular intervals.

[0043] The electric heating body 2 is preferably made of a material that generates heat when energized, for example, preferably made of a nickel-chromium alloy or the like.

[0044] The through-hole 3 is provided so as to penetrate the substrate 1. For example, as shown in FIGS. 1C and 1D, the through-hole 3 penetrates the substrate 1 such that its longitudinal direction is along the axial direction of the substrate 1 constituting the heat storage body 10. The through-hole 3 opens to the surface 1a of the substrate 1 on one side in the axial direction of the substrate 1, and this opening serves as the inlet 3a for the heat medium fluid. The through-hole 3 also opens on the back surface facing the surface 1a on the other side in the axial direction of the substrate 1, and this opening serves as the outlet for the heat medium fluid.

[0045] In FIGS. 1C and 1D, the cross-sectional shape of the through-hole 3 is circular, but the cross-sectional shape is not particularly limited and may be any of an elliptical shape, a rectangular shape, or a triangular shape.

[0046] The through-hole 3 is capable of allowing the heat medium fluid to flow through. As the heat medium fluid, in order to prevent the oxidation of graphite, one kind of inert gas selected from nitrogen, helium, argon, and carbon dioxide can be used.

[0047] The operation of the heat storage device 101 according to this embodiment will be described. During heat storage, the electric heater 2 is energized from an external power source to generate heat in the electric heater 2. The generated heat propagates through the graphite constituting the base body 1 and reaches the metal particles 4, increasing the temperatures of the graphite and the metal particles 4. Since the metal particles 4 have a larger heat capacity per unit volume than graphite, a large amount of heat can be stored. Further, the metal particles 4 may melt due to heat and become liquid. Since 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 contact the graphite constituting the base body 1, suppressing the corrosion of the graphite. Therefore, the heat storage device 101 of this embodiment can store a larger amount of heat than a conventional heat storage device having no coating layer.

[0048] Next, during heat dissipation, a relatively low-temperature heat medium fluid is introduced into the through-hole 3 from the inlet 3a of the through-hole 3, circulated inside the heat storage device 101, and then led out from the outlet. The heat medium fluid introduced from the inlet 3a needs to be at a temperature lower than the temperatures of the graphite and the metal particles 4 in the heat storage state. While the heat medium fluid flows through the through-hole 3, heat exchange occurs between the heat medium fluid and the graphite and the metal particles 4 in the heat storage state, increasing the temperature of the heat medium fluid while decreasing the temperatures of the graphite and the metal particles 4. Then, the heated heat medium fluid at a high temperature is taken out from the outlet.

[0049] More specifically, for example, during heat storage, surplus power of natural energy or the like is used to energize and heat the electric heater 2 to heat the metal particles 4 above their melting points for heat storage. During heat dissipation, by introducing a low-temperature heat medium fluid into the through-hole 3, a high-temperature heat medium fluid is taken out and sent to, for example, an external heat exchanger to generate high-temperature steam. Then, by using the high-temperature steam, power generation by a steam turbine or a gas turbine becomes possible.

[0050] (Third Embodiment) Next, the heat storage device 201 according to the third embodiment will be described. As shown in FIGS. 2A and 2B, the heat storage device 201 of the present embodiment includes a heat storage body 10, and a plurality of through holes 13 that penetrate in the axial direction of the base body 1 and through which a heat medium fluid can flow are provided in the base body 1 constituting the heat storage body 10. Note that the axial direction of the base body 1 is the same as that in the case of the second embodiment.

[0051] The heat storage body 10 is composed of a base body 1 made of graphite and metal particles 4 contained inside the base body 1, similar to the heat storage body of the first embodiment. A coating layer is provided on the surface of the metal particles 4, similar to the first embodiment.

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

[0053] The through hole 13 is enabled to allow the heat medium fluid to flow through. As the heat medium fluid, in order to prevent the oxidation of graphite, one kind of inert gas selected from nitrogen, helium, argon, and carbon dioxide can be used.

[0054] The operation of the heat storage device 201 of the present embodiment will be described. During heat storage, a relatively high-temperature heat medium fluid is introduced into the through hole 13, allowed to flow inside the heat storage device 201, and then led out from the outlet. The heat medium fluid introduced from the inlet 13a needs to be at a higher temperature than the temperature of the graphite and the metal particles 4 in the state before heat storage.

[0055] While the high-temperature heat transfer medium fluid flows through the through-hole 13, heat exchange occurs between the graphite and the metal particles 4 in the state before heat storage, and the heat of the heat transfer medium fluid is propagated through the graphite constituting the base body 1 and reaches the metal particles 4, raising the temperatures of the graphite and the metal particles 4. Since the metal particles 4 have a larger heat capacity per unit volume than graphite, a large amount of heat can be stored. Further, the metal particles 4 may melt due to heat to become a liquid. Since 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 contact the graphite constituting the base body 1, suppressing the corrosion of the graphite. Therefore, the heat storage device 201 of the present embodiment can store a larger amount of heat than a conventional heat storage device having no coating layer.

[0056] Next, during heat dissipation, as in the second embodiment, a relatively low-temperature heat transfer medium fluid is introduced into the through-hole 13 from the inlet 13a of the through-hole 13, and after flowing the heat transfer medium fluid through the inside of the heat storage device 201, it is led out from the outlet. The heat transfer medium fluid introduced from the inlet 13a needs to be at a lower temperature than the temperatures of the graphite and the metal particles 4 in the heat storage state. While the heat transfer medium fluid flows through the through-hole 13, heat exchange occurs between the graphite and the metal particles 4 in the heat storage state, and while the temperature of the heat transfer medium fluid rises, the temperatures of the graphite and the metal particles 4 decrease. Then, the heated heat transfer medium fluid at a high temperature is taken out from the outlet.

[0057] More specifically, for example, during heat storage, the heat storage device 201 uses surplus power of natural energy or the like to heat the heat transfer medium fluid, circulates this through the through-hole 13, and heats the metal particles 4 above their melting points for heat storage. During heat dissipation, by introducing a low-temperature heat transfer medium fluid into the through-hole 13, a high-temperature heat transfer medium fluid is taken out, and this is sent to, for example, an external heat exchanger to generate high-temperature steam. Then, by using the high-temperature steam, power generation by a steam turbine or a gas turbine becomes possible.

[0058] (Fourth Embodiment) Next, the heat storage system 301 of the 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, the heat storage system 301 of the present embodiment includes a heat storage device 101, an external power source 302, a heat exchanger 303, a fluid circulation mechanism 304, and a control unit 305.

[0060] The external power source 302 supplies power to the electric heater 2 by energizing the electric heater 2 of the heat storage device 101.

[0061] The heat exchanger 303 receives, as the primary-side fluid, the heat medium fluid derived from the heat storage device 101 and performs heat exchange between the heat medium fluid and the secondary-side 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 the 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 energizes the electric heater 2 of the heat storage device 101 by the external power source 302 during heat storage, and circulates the heat medium fluid between the heat storage device 101 and the heat exchanger 303 by the fluid circulation mechanism 304 during heat dissipation.

[0064] Hereinafter, the operation of the heat storage system 301 will be described. During heat storage, a command is issued from the control unit 305 to the external power source 302, and power is supplied from the external power source 302 to the electric heater 2 to energize it. Thereby, heat is accumulated in the heat storage device 101. The operation of accumulating heat in the heat storage device 101 is as 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 medium fluid from the inlet 3a of the heat storage device 101 into the through-hole 3, circulate it inside the heat storage device 101, and then discharge it from the outlet 3b. The heat medium fluid that is discharged and heated to a high temperature is sent to the heat exchanger 303 through the flow path 304a, and heat exchange is performed with the secondary-side fluid (for example, water) in the heat exchanger 303. By the heat exchange, the water as the secondary-side fluid becomes high-temperature steam. On the other hand, the heat medium fluid that is cooled to a low temperature by the heat exchange is sent back to the heat storage device 101 again through the flow path 304a.

[0066] According to the heat storage system 301 of the present embodiment, when the energy supply is excessive, the excess energy is stored in the heat storage device 101 as heat energy. When the energy supply is insufficient, the heat energy stored in the heat storage device 101 is taken out, steam is generated in the heat exchanger 303, and the generated steam can be sent to a steam turbine or the like to generate electricity.

[0067] (Fifth Embodiment) Next, the heat storage system 401 of the fifth embodiment will be described. This heat storage system 401 is configured by connecting a plurality of, specifically four, heat storage devices 101 in parallel to one heat exchanger 303.

[0068] That is, as shown in FIG. 4, the heat storage system 401 of the present embodiment includes four heat storage devices 101, an external power source 302 connected to each heat storage device 101, one heat exchanger 303, a fluid circulation mechanism 404, and a control unit (not shown). Among these, the heat storage device 101, the external power source 302, the heat exchanger 303, and the control unit are the same as those described above.

[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 the through-hole 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 device 101 and the heat exchanger 303.

[0070] According to this heat storage system 401, similar to the heat storage system 301 of the fourth embodiment, when the energy supply is excessive, the surplus energy is stored in the heat storage device 101 as heat energy, and when the energy supply is insufficient, the heat energy stored in the heat storage device 101 is taken out, steam is generated 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, the heat storage system 501 of the 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 the present 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] The external heat source 502 heats the first heat medium 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 led out from the heat storage device 201 as the primary side fluid, and performs heat exchange between the second heat medium fluid and the secondary side 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 the 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] During heat storage, the control unit 505 causes the fluid supply mechanism 503 to supply the first heat medium fluid heated by the external heat source 502 to the heat storage device 201, and during heat dissipation, the fluid circulation mechanism 304 circulates the second heat medium fluid between the heat storage device 201 and the heat exchanger 303.

[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. Further, the control unit 505 issues a command to the fluid supply mechanism 503 to supply the heated first heat medium fluid to the heat storage device 201. Thereby, heat is stored in the heat storage device 201. The operation of storing heat in the heat storage device 201 is as 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 the relatively low-temperature second heat medium fluid from the inlet 13a of the heat storage device 201 into the through hole 13, circulate it inside the heat storage device 201, and then discharge it from the outlet 13b. The discharged second heat medium fluid that has been heated to a high temperature is sent to the heat exchanger 303 through the flow path 304a, and heat exchange is performed with the secondary fluid (for example, water) in the heat exchanger 303. By the heat exchange, the water as the secondary fluid becomes high-temperature steam. On the other hand, the second heat medium fluid that has been cooled to a low temperature by the heat exchange is sent back to the heat storage device 201 again through the flow path 304a.

[0080] According to the heat storage system 501 of the present embodiment, when the energy supply is excessive, the excess energy is stored in the heat storage device 201 as heat energy, and when the energy supply is insufficient, the heat energy stored in the heat storage device 201 is taken out to generate steam in the heat exchanger 303, and the generated steam can be sent to a steam turbine or the like for power generation.

[0081] (Seventh Embodiment) Next, the heat storage system 601 of the seventh embodiment will be described. This heat storage system 601 is configured such that a plurality of, specifically four, heat storage devices 201 are connected in parallel to one heat exchanger 303.

[0082] That is, as shown in FIG. 6, the heat storage system 601 of the present 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). Among these, the heat storage device 201, the external heat source 502, the fluid supply mechanism 503, the heat exchanger 303, and the control unit are as described above.

[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 the through hole 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 device 201 and the heat exchanger 303.

[0084] According to this heat storage system 601, similar to the heat storage system 501 of the sixth embodiment, when the energy supply is excessive, the excess energy is stored as thermal energy in the heat storage device 201. When the energy supply is insufficient, the thermal energy stored in the heat storage device 201 is taken out, steam is generated 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, the heat storage system 701 of the eighth embodiment will be described. This heat storage system 701 has substantially the same configuration as the heat storage system 401 of the fifth embodiment. The difference is 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 tube 704 is composed of an inner tube 704a and an outer tube 704b with a larger diameter than the inner tube. The inner tube 704a is inserted inside the outer tube 704b.

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

[0089] A heat medium fluid heated by the heat storage device 101 flows through the high-temperature flow path, while a low-temperature heat medium fluid after heat exchange in the heat exchanger 303 flows through the low-temperature flow path.

[0090] According to this embodiment, by using the double tube 704 as the flow path of the fluid circulation mechanism, the inner tube 704a through which the heated heat medium fluid flows is covered by the outer tube 704b, and the inner tube 704a does not directly contact the outside air, so the heat loss between the heat storage device 101 and the heat exchanger 303 can be suppressed.

[0091] Note that using a double tube as the flow path of the fluid circulation mechanism is not limited to this embodiment and may also be applied to the fluid circulation mechanisms of other embodiments.

[0092] As described in several embodiments above, according to the present invention, by using a heat storage body including graphite and metal particles whose surfaces are coated with ceramics or carbon, erosion of graphite can be prevented even when the metal particles are liquefied during heat storage, and a heat storage body, a heat storage device, and a heat storage system with a large heat storage amount can be provided.

Examples

[0093] Hereinafter, the present invention will be described in more detail with reference to examples.

[0094] (Example) 1 kg of aluminum particles with an average particle size of 2 mm was prepared by weight. These aluminum particles were put into a reaction vessel, and after heating the inside of the reaction vessel to 600 °C, acetylene gas as a coating raw material gas and argon gas for fluidization were ejected from a gas introduction nozzle provided at the bottom of the reaction vessel to fluidize the aluminum particles while thermally decomposing the acetylene gas to deposit carbon atoms on the surface of the aluminum particles. At this time, 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 over 60 seconds to form 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 dried by heating to form a layer of ceramics made of silicon dioxide on the surface of the layer of pyrolytic carbon.

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

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

[0099] Using the manufactured heat storage bodies of the examples and comparative examples, heat storage systems shown in FIG. 3 were respectively configured. Then, for the heat storage systems of the examples and comparative examples, the state of the aluminum particles after repeating heat storage and heat release was investigated by the following method.

[0100] As a heat storage process, the heat storage body was heated to 1000° C. by electric heating to melt aluminum. Next, as a heat release process, nitrogen gas was introduced into and circulated through the heat storage body from a heat exchanger, and the heat exchanger was operated for 12 hours. During this time, the temperature of the heat storage body decreased to 400° C. Such a heat storage process and heat release process were defined as one cycle, and this cycle was repeated 20 times. Then, the heat storage body was cooled and cut, and the state of the aluminum particles on the cross section was observed.

[0101] In the heat storage body of the example, no gap was observed between the coated particles and the graphite of the substrate even after repeating the heat storage and heat release cycles, and penetration of aluminum into the graphite was not confirmed.

[0102] On the other hand, in the heat storage body of the comparative example, a gap was observed between the aluminum particles and the graphite of the substrate after repeating the heat storage and heat release cycles. This is considered to be because the molten aluminum penetrated into the graphite.

[0103] From the above, the effect of preventing leakage of molten aluminum by the coating layer was confirmed.

Explanation of Reference Numerals

[0104] 1... Substrate, 2... Electric heater, 3, 13 Through holes, 4... Metal particles, 5... Coating layer, 6... Layer made of carbon, 7... Layer made of ceramics, 10... Heat storage body, 101... Heat storage device, 301, 401, 501, 601, 701... Heat storage systems, 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 base made of graphite, and metal particles filled inside the base, are provided, A heat storage body, wherein a coating layer made of either carbon or ceramics or both is provided on the surface of the metal particles.

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

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

4. The heat storage body 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. A heat storage body according to any one of claims 1 to 4, and an electric heater installed inside the base of the heat storage body and heating the heat storage body by energization, are provided, A heat storage device, wherein a plurality of through holes capable of allowing a heat medium fluid to flow through in the axial direction of the base are provided in the base of the heat storage body.

6. A heat storage body according to any one of claims 1 to 4 is provided, A heat storage device, wherein a plurality of through holes capable of allowing a heat medium fluid to flow through in the axial direction of the base are provided in the base of the heat storage body.

7. A heat storage device according to claim 5, an external power source capable of energizing the electric heater provided in the heat storage device, a heat exchanger, a fluid circulation mechanism for circulating a heat medium fluid between the heat storage device and the heat exchanger, and a control unit for controlling to energize the electric heater of the heat storage device by the external power source during heat storage and to circulate the heat medium fluid between the heat storage body and the heat exchanger by the fluid circulation mechanism during heat dissipation. A heat storage system comprising the above.

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

9. A heat storage device according to claim 6, an external heat source for heating a first heat medium fluid, a heat exchanger, a fluid supply mechanism for supplying the first heat medium fluid from the external heat source to the heat storage device, a fluid circulation mechanism for circulating a second heat medium fluid between the heat storage device and the heat exchanger. A control unit that controls to supply the first heat medium fluid heated by the external heat source by the fluid supply mechanism to the heat storage device during heat storage, and to circulate the second heat medium fluid between the heat storage device and the heat exchanger by the fluid circulation mechanism during heat dissipation; A heat storage system comprising the same.

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

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