Thermal storage system

Abstract

In thermal energy storage power generation, we provide a thermal energy storage system that can efficiently raise the temperature of the heat transfer medium using an electric heater. [Solution] The heat storage system 10 comprises a heat storage tank 20 configured to store a heat transfer medium HHM and extending in a first direction X, and a heating unit 11 configured to heat the heat transfer medium and in contact with the heat storage tank 20 in a second direction Y, wherein the heating unit 11 includes one or more heating tubes 13 configured through which the heat transfer medium flows and into the heat storage tank 20, and one or more electric heaters 14 configured to heat the heating tubes 13, wherein in the first direction X, the heating tubes 13 and the electric heaters 14 extend over approximately the entire length of the heat storage tank 20.

Description

Technical Field

[0001] The present invention relates to a heat storage system, and more specifically, to a heat storage system used for heat storage power generation.

Background Art

[0002] For the upcoming decarbonized society, the introduction of renewable energy is progressing. Also, the CO2 emissions from thermal power generation using fossil fuels are a concern. Since the power supply and demand change moment by moment, heat storage power generation has attracted attention from the perspective of fulfilling the power adjustment function that thermal power has conventionally played. In heat storage power generation, power can be stored when surplus power is generated by renewable energy, and the stored power can be supplied when the power demand increases. Heat storage power generation has the advantage of being able to achieve lower costs compared to batteries and hydrogen.

[0003] As a heat storage method for heat storage power generation, a heat storage method using molten salt has been proposed. For example, Patent Document 1 discloses a high-temperature heat medium supply unit that heats and supplies a heat medium in which molten salt is melted, a high-temperature heat storage tank that stores the high-temperature heat medium supplied from the high-temperature heat medium supply unit, a low-temperature heat storage tank that stores the low-temperature heat medium after the high-temperature heat medium is cooled, and a steam generation unit that generates high-pressure steam and low-temperature heat medium supplied to a load part by heat exchange between the heat medium and steam.

[0004] Also, Non-Patent Document 1 discloses a system in heat storage power generation in which molten salt taken out from a low-temperature side tank is electrothermally converted by a heater and the heated molten salt is transferred to a high-temperature side tank.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006] [Non-Patent Document 1] Toru Okazaki, "Innovative Retrotechnology Necessary for a Decarbonized Society," [online], Japan Society of Applied Physics, January 14, 2022, [Retrieved October 7, 2024], Internet<URL:https: / / www.jsap.or.jp / columns / gx / e1-9> [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, since the maximum heat resistance temperature of an electric heater is about 800°C, the maximum temperature at which an electric heater heats the heat transfer medium is also about 800°C. This temperature is lower than the heating temperature achieved by a boiler. Therefore, when a system for storing a heat transfer medium (hereinafter referred to as the "thermal storage system") that heats the heat transfer medium to a high temperature in thermal energy storage power generation is constructed using an electric heater, it is necessary to heat the heat transfer medium more efficiently than when the thermal storage system is constructed using a boiler.

[0008] Therefore, one of the objectives of the present invention is to provide a heat storage system that can efficiently raise the temperature of a heat transfer medium using an electric heater in heat storage power generation. [Means for solving the problem]

[0009] (1) The heat storage system of the present invention is a heat storage system used for thermal energy storage power generation, comprising a tank configured to store a heat transfer medium and extending in a first direction, and a heating unit configured to heat the heat transfer medium and in contact with the tank in a second direction intersecting the first direction, wherein the heating unit is configured such that the heat transfer medium flows through it and the high-temperature heat transfer medium reaches the tank. The system includes one or more flow channels configured for inflow and one or more electric heaters configured for heating the flow channels, wherein in the first direction, the flow channels and the electric heaters extend over substantially the entire length of the tank.

[0010] In the thermal energy storage system of (1), the flow path and electric heater constituting the heating unit extend over a long distance, approximately the entire length of the tank in the first direction. Even in this case, since the heating unit is in contact with the tank in the second direction, the tank provides support, and the electric heater and flow path are stably erected in the first direction. Furthermore, in the thermal energy storage system of (1), since the electric heater and flow path extending over a long distance in the first direction are stably erected in the first direction, the heat transfer medium flowing through the flow path can be heated by the electric heater over a long distance in the first direction. Therefore, in thermal energy storage power generation of (1), it is possible to efficiently raise the temperature of the heat transfer medium using the electric heater.

[0011] Here, "approximately the total length of the tank" may include not only the same length as the total length of the tank in the first direction, but also cases where the total length differs from the total length of the tank in the first direction by, for example, about 1 / 10 or less.

[0012] (2) The heat storage system of (1) may further include a mechanism for filling the tank with the heat transfer medium.

[0013] According to the heat storage system of (2), it becomes easy to introduce the heat transfer medium into the heating tube.

[0014] (3) In the heat storage system of (1), the heating unit may be in contact with the outer surface of the tank in the second direction.

[0015] In the heat storage system of (3), the heating unit is located outside the tank, so the tank prevents the heat from the heating unit from being transferred in the second direction to the heat transfer medium stored in the tank.

[0016] (4): In the heat storage system of (1), the heating unit may be in contact with the inner surface of the tank in the second direction.

[0017] In the heat storage system of (4), the heating unit is located inside the tank, which suppresses heat leakage from the electric heater to the outside and allows the heat transfer medium to be heated to a higher temperature more efficiently.

[0018] (5): In the heat storage system of (4), an insulating section may be provided between the heating unit and the heat transfer medium stored in the tank in the second direction.

[0019] In the heat storage system of (5), an insulating section is placed between the heating unit and the heat transfer medium stored in the tank in the second direction, so that the heat from the heating unit located inside the tank is suppressed from being transferred to the heat transfer medium stored in the tank along the second direction. As a result, according to the heat storage system of (5), temperature stratification is easily formed in the heat transfer medium stored in the tank.

[0020] (6) In any of the heat storage systems of (1) to (5), a temperature stratification is formed in the heat transfer medium stored in the tank, with a high-temperature heat transfer medium stored on the upper side in the first direction, and a heat transfer medium at a lower temperature than the high-temperature heat transfer medium stored on the lower side in the first direction, and the lower end of the flow path in the first direction may be configured to allow the low-temperature heat transfer medium stored in the tank to flow in.

[0021] According to the thermal energy storage system of (6), since a high-temperature heat transfer medium and a low-temperature heat transfer medium are contained in a single tank, a separate tank for storing the low-temperature heat transfer medium can be omitted in thermal energy storage power generation. Furthermore, in the thermal energy storage system of (6), the other end of the flow path in the first direction is configured to allow the low-temperature heat transfer medium stored in the tank to flow in. This allows the low-temperature heat transfer medium stored in one tank to be heated in the flow path and then returned to one side of the tank in the first direction via one end of the flow path. As a result, in the thermal energy storage mode in which the low-temperature heat transfer medium is heated and the high-temperature heat transfer medium is stored in the tank, it is possible to keep the liquid level in the tank at a roughly constant level, thereby suppressing the creation of unnecessary space in the tank.

[0022] (7): In the heat storage system of (6), in the second direction, the heating unit is in contact with the inner peripheral surface of the tank, and the other end of the flow path in the first direction may be inclined so as to project inward in the second direction as it goes from the other side to the one side in the first direction.

[0023] According to the heat storage system of (7), since the other end of the flow path in the first direction is inclined so as to project inward in the second direction as it goes from the other side to the one side in the first direction, the low-temperature heat medium stored in the tank easily flows into the flow path through the other end of the flow path.

[0024] (8): In the heat storage system of any one of (1) to (7), each of the plurality of electric heaters and the plurality of flow paths is formed in a rod shape, and in the heating unit, the electric heaters may be uniformly arranged.

[0025] According to the heat storage system of (8), since the plurality of electric heaters are uniformly arranged, the plurality of flow paths can be uniformly heated, and as a result, the heat medium can be heated to a higher temperature more efficiently. Further, according to the heat storage system of (8), since the plurality of electric heaters are not localized, it is possible to suppress some of the plurality of electric heaters from being locally heated to a high temperature.

[0026] (9): In the heat storage system of any one of (1) to (7), the electric heater may be formed in a planar shape.

[0027] According to the heat storage system of (9), the number of electric heaters included in the heating unit can be reduced.

[0028] (10): In the heat storage system of any one of (1) to (9), a plurality of the electric heaters may be accommodated inside one of the flow paths.

[0029] According to the heat storage system of (10), the number of flow paths included in the heating unit can be reduced. [Effects of the Invention]

[0030] According to the present invention, a heat storage system is provided that can efficiently raise the temperature of a heat transfer medium using an electric heater in a heat storage power generation system. [Brief explanation of the drawing]

[0031] [Figure 1] This figure schematically shows a thermal energy storage power generation system according to the first embodiment of the present invention. [Figure 2] This diagram illustrates the thermal storage system of the thermal storage power generation system shown in Figure 1, and schematically shows a cross-section of the thermal storage system in the second direction. [Figure 3] This diagram illustrates the thermal storage system of the thermal storage power generation system shown in Figure 1, and schematically shows a cross-section of the thermal storage system in a first direction. [Figure 4] This is a schematic cross-sectional view in the second direction showing a modified example (modification 1) of the heat storage system shown in Figure 2. [Figure 5] This figure illustrates a heat storage system according to a second embodiment of the present invention, and schematically shows a cross-section of the heat storage system in a second direction. [Figure 6] This figure illustrates a heat storage system according to a second embodiment of the present invention, and schematically shows a cross-section of the heat storage system in a first direction. [Figure 7] This is a diagram illustrating the heating unit elements that constitute the heating unit according to the third embodiment of the present invention. [Figure 8] This figure illustrates a modified example (modified example 2) of the heating unit element shown in Figure 7. [Figure 9] This figure illustrates a heat storage system according to a fourth embodiment of the present invention, and schematically shows a cross-section of the heat storage system in a second direction. [Figure 10] This figure illustrates a heat storage system according to a fifth embodiment of the present invention, and schematically shows a cross-section of the heat storage system in a second direction. [Figure 11] Figure 10 is a diagram illustrating the heating unit elements that make up the heating unit of the heat storage system shown. [Figure 12] This figure schematically shows a thermal energy storage power generation system according to the sixth embodiment of the present invention. [Figure 13] Figure 12 is a diagram illustrating the thermal storage system of the thermal storage power generation system shown, and schematically shows a cross-section of the thermal storage system in a first direction. [Figure 14] This figure schematically shows a modified example (modified example 3) of the thermal energy storage power generation system according to the sixth embodiment of the present invention. [Figure 15] This diagram illustrates the thermal storage system of the thermal storage power generation system shown in Figure 14, and schematically shows a cross-section of the thermal storage system in a first direction. [Modes for carrying out the invention]

[0032] The following examples illustrate embodiments for implementing the heat storage system according to the present invention, along with the accompanying drawings. The embodiments illustrated below are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified and improved from the following embodiments without departing from its spirit. In addition, in the accompanying drawings, the dimensions of each component may be exaggerated or reduced, or hatching may be omitted, in order to facilitate understanding.

[0033] (First Embodiment) Figure 1 is a schematic diagram showing a thermal energy storage power generation system according to the first embodiment. As shown in Figure 1, the thermal energy storage power generation system 1 is a system for performing thermal energy storage power generation, and the electricity generated by the thermal energy storage power generation system 1 may be supplied to consumers 9, etc. The thermal energy storage power generation system 1 mainly comprises a power generation unit 2, a steam generation unit 3, a thermal energy storage system 10, and a power supply unit 8. The power supply unit 8 is capable of supplying power to the heat-generating element of the thermal energy storage system 10, which will be described later. The power supply unit 8 is not particularly limited, but may be a generator that uses renewable energy, such as a wind turbine or a solar power generator.

[0034] The thermal energy storage power generation system 1 is configured to be able to switch as needed between a power generation mode, in which power is generated by operating the power generation unit 2 and the steam generation unit 3, and a thermal energy storage mode, in which a high-temperature heat transfer medium (hereinafter referred to as "high-temperature heat transfer medium HHM") is stored in the thermal energy storage system 10 by operating the thermal energy storage system 10.

[0035] The power generation unit 2 generates electricity by operating (rotating) a steam turbine with steam V generated in the steam generation unit 3. This electricity is supplied to consumers 9, etc. The temperature of the steam V supplied to the power generation unit 2 may be, for example, around 600°C. The power generation unit 2 is also equipped with a condenser that cools the steam V from the steam turbine into water W, and the water W generated by this condenser, etc., is returned to the steam generation unit 3 through the piping 5. This water W is then used to... In the steam generation unit 3, the water is heated and converted back into steam V, which is then supplied to the power generation unit 2 via the piping 4.

[0036] The steam generation unit 3 heats the water W supplied from the power generation unit 2 to generate steam V. Specifically, the steam generation unit 3 heats the water W with a high-temperature heat transfer medium HHM supplied from the heat storage system 10 to generate steam V. The temperature of the high-temperature heat transfer medium HHM may be, for example, 600°C or higher, and more specifically, it may be around 650-700°C. Furthermore, the high-temperature heat transfer medium HHM used in the steam generation unit 3 becomes a low-temperature heat transfer medium (hereinafter referred to as "low-temperature heat transfer medium LHM") as it heats the water W. This low-temperature heat transfer medium LHM is supplied to the heat storage system 10 through the piping 7. The temperature of the low-temperature heat transfer medium LHM may be, for example, around 200-400°C.

[0037] The heat transfer medium is a solution in which a predetermined molten salt is molten. The molten salt can be appropriately selected according to the conditions of thermal energy storage power generation. For example, such a molten salt may be selected from the group consisting of NaNO2, LiNO3, NaNO3, KNO3, NaOH, KOH, LiCl, NaCl, KCl, Li2CO3, Na2CO3, K2CO3, a mixture of LiF and BeF2, a mixture of LiF, NaF and KF, and a mixture of LiF, BeF2, ThF4 and UF4, from the viewpoint of being easy to handle and having a relatively low specific heat. Furthermore, the solvent for melting the molten salt can be appropriately selected according to the conditions of thermal energy storage power generation. For example, from the viewpoint of easily forming temperature stratification, a silicone oil may be used.

[0038] The heat storage system 10 is configured to heat the low-temperature heat transfer medium LHM to produce a high-temperature heat transfer medium HHM, and to store at least the high-temperature heat transfer medium HHM. That is, when the heat storage system 10 operates in heat storage mode, the high-temperature heat transfer medium HHM is stored in the heat storage system 10. On the other hand, in power generation mode, the high-temperature heat transfer medium HHM stored in the heat storage system 10 is supplied to the steam generation unit 3 through the piping 6, and in this embodiment, the low-temperature heat transfer medium LHM is supplied from the steam generation unit 3 to the heat storage system 10 through the piping 7.

[0039] The heat storage system 10 of this embodiment will be described further below. Figure 2 is a schematic diagram showing a cross-section of the heat storage system 10 in a second direction. Figure 3 is a schematic diagram showing a cross-section of the heat storage system 10 in a first direction. As shown in Figures 2 and 3, the heat storage system 10 comprises a heat storage tank 20 (tank) and a heating unit 11.

[0040] The heat storage tank 20 is made of a material with excellent heat insulation properties, and may be made of, for example, an insulating material used to insulate steam pipes in a power plant. The heat storage tank 20 extends in a first direction X and is formed in a cylindrical shape (in this embodiment, cylindrical) with a bottom 22. In this embodiment, the first direction X is the vertical direction. In the first direction X, the other end (lower side) of the heat storage tank 20 is the bottom 22, and the one end (upper side) of the heat storage tank 20 is open. The second direction Y is a direction that intersects the first direction X, and may be a direction perpendicular to the first direction X. If the heat storage tank 20 is cylindrical, the second direction Y is the radial direction of the heat storage tank 20 (bottom 22). Here, the "circle" in "cylindrical" includes both a perfect circle and an ellipse. In the second direction Y, the side approaching the center of the heat storage tank 20 is defined as "inside," and the side moving away from the center of the heat storage tank 20 is defined as "outside."

[0041] The dimensions and external shape of the heat storage tank 20 can be selected as appropriate. For example, the height of the heat storage tank 20 (length in the first direction X) may be around 40m. The external diameter of the heat storage tank 20 (length in the second direction Y) and the thickness of the heat storage tank 20 (difference between the external and internal diameters) can also be selected as appropriate. Furthermore, the external shape of the heat storage tank 20 can be a cylinder, for example, to reduce the amount of insulation material used, so that the surface area per unit volume of the heat storage tank is small. It can be a shape as well.

[0042] The heat storage tank 20 has a wall portion 21 extending upward (to one side) in the first direction X from the outer circumference of the bottom portion 22. The thickness of the heat storage tank 20 is the thickness of the wall portion 21. The wall portion 21 has a cylindrical shape (in this embodiment, cylindrical) and has an outer surface 21A and an inner surface 21B. In the second direction Y, the length from the outer surface 21A to the inner surface 21B is the thickness of the wall portion 21, which is the thickness of the heat storage tank 20. The heat storage tank 20 also has an upper wall 21U that closes the upper side of the heat storage tank 20.

[0043] The storage area SA of the heat storage tank 20 is formed by the inner circumferential surface 21B of the wall portion 21, the upper surface 22A of the bottom portion 22, and the upper wall 21U. At least high-temperature heat transfer medium HHM is stored in this storage area SA of the heat storage tank 20.

[0044] In this embodiment, a portion of the upper wall 21U is in communication with the accumulator AC, and the storage area SA is filled with the heat transfer medium by the accumulator AC. In this embodiment, the accumulator AC is positioned above the upper wall 21U and absorbs the volume change of the heat transfer medium caused by temperature changes in the heat transfer medium. Thus, in this embodiment, the heat storage system 10 further includes the accumulator AC, which is a mechanism for filling the tank with the heat transfer medium. Note that the mechanism for filling the tank with the heat transfer medium is not limited to the accumulator AC.

[0045] The heating unit 11 is in contact with the wall portion 21 of the heat storage tank 20 in the second direction Y. In this embodiment, the heating unit 11 is in contact with the outer peripheral surface 21A of the wall portion 21. In this embodiment, the heating unit 11 includes a plurality of heating tubes 13 and a plurality of electric heaters 14. In Figures 2 and 3, for convenience, only some of the heating tubes 13 and electric heaters 14 that constitute the heating unit 11 are shown. Also, in Figure 2, heating tubes 13 and electric heaters 14 that are not shown are indicated by dots.

[0046] Each of the multiple heating tubes 13 is made of a material with excellent thermal conductivity, such as a steel pipe, or more specifically, a carbon steel pipe. The dimensions of each of the multiple heating tubes 13 can be selected as appropriate, but for example, the diameter (outer diameter) may be about 5.4 mm and the height (total length in the first direction X) may be about 40 m. Each of the multiple heating tubes 13 extends over approximately the entire length of the heat storage tank 20 (approximately the entire length of the wall portion 21) in the first direction X. Also, since the diameter of the heating tube 13 is small compared to the height of the heating tube 13, the heating tube 13 has an elongated shape.

[0047] As shown in Figure 3, the lower end 13D of the heating tube 13 (the other end in the first direction X) is configured to be in fluid communication with the lower region of the storage area SA of the heat storage tank 20. Therefore, the heat transfer medium stored in the lower region of the storage area SA can flow into the heating tube 13 through the lower end 13D. The upper end 13U of the heating tube 13 (the other end in the first direction X) is formed to slope downward from slightly above the upper wall 21U of the wall portion 21 of the heat storage tank 20 toward the storage area SA.

[0048] As shown in Figures 2 and 3, in this embodiment, each of the multiple electric heaters 14 is formed in a rod shape. The electric heater 14 is not particularly limited, but in this embodiment, it is configured as a so-called sheathed heater. Each of the multiple electric heaters 14 has a configuration in which a heating element 15 is housed in a pipe 16 made of, for example, metal, which has excellent thermal conductivity. The heating element 15 is not particularly limited, but for example, it may be a coiled nichrome wire. Furthermore, the dimensions of each of the multiple electric heaters 14 can be selected as appropriate. However, for example, the diameter (outer diameter) may be about 5.4 mm and the height (total length in the first direction X) may be about 40 m. Each of the multiple electric heaters 14 extends over approximately the entire length of the heat storage tank 20 (approximately the entire length of the wall portion 21) in the first direction X. Also, since the diameter of the electric heater 14 is small compared to the height of the electric heater 14, the electric heater 14 has an elongated shape.

[0049] In this embodiment, the heating element 15 of the electric heater 14 extends over approximately the entire length of the electric heater 14 in the first direction X. Furthermore, a wiring 17 may be connected to, for example, the upper end of the heating element 15, and power may be supplied to the heating element 15 from the power supply unit 8 via this wiring 17. The electric heater 14 heats up when power is supplied to the heating element 15, causing the heating element 15 to generate heat.

[0050] As shown in Figure 2, in this embodiment, the plurality of heating tubes 13 and the plurality of electric heaters 14 are arranged outside the outer peripheral surface 21A of the wall portion 21 of the heat storage tank 20, and surround the entire circumference of the outer peripheral surface 21A. In this embodiment, the plurality of heating tubes 13 and the plurality of electric heaters 14 include a first group 11A that is in contact with the entire circumference of the outer peripheral surface 21A in the second direction Y (radial direction), a second group 11B that is outside the first group 11A and is in contact with the entire circumference of the first group 11A in the second direction Y, and a third group 11C that is outside the second group 11B and is in contact with the entire circumference of the second group 11B in the second direction Y. Note that the number of groups of the plurality of heating tubes 13 and the plurality of electric heaters 14 is not limited to three, but may be one (only the first group 11A), two (the first group 11A and the second group 11B), or four or more.

[0051] For the sake of explanation, Figure 3 schematically shows a cross-section of the heat storage system 10 in the first direction X when the heating unit 11 consists only of the first group 11A.

[0052] Furthermore, as shown in Figure 2, in this embodiment, in a heating unit 11 composed of multiple heating tubes 13 and multiple electric heaters 14, the multiple electric heaters 14 are uniformly arranged. Specifically, the multiple electric heaters 14 are uniformly arranged so that each of them does not touch each other and forms a unit consisting of one electric heater 14 and multiple heating tubes 13. Figure 2 shows an example in which the multiple electric heaters 14 are uniformly arranged by placing one electric heater 14 at the center of a group of heating tubes 13 arranged to form a regular hexagon when viewed from a first direction X. That is, in the example in Figure 2, a unit is formed by one electric heater 14 and six heating tubes 13.

[0053] Furthermore, for example, if the heating unit 11 consists only of the first group 11A, multiple electric heaters 14 may be uniformly arranged by placing one electric heater 14 for every N (N is a natural number) heating tubes 13 in the circumferential direction of the heat storage tank 20 (wall portion 21). More specifically, consider a modified example in which the heating unit 11 of Figure 2 consists only of the first group 11A. In this modified example, multiple electric heaters 14 are uniformly arranged by placing one electric heater 14 for every two heating tubes 13 in the circumferential direction. That is, in this modified example, the unit is formed by one electric heater 14 and two heating tubes 13 arranged in the circumferential direction of the heat storage tank 20.

[0054] In the heat storage mode, when power is supplied to the heating element 15, the multiple electric heaters 14 heat up, and the heat from the multiple electric heaters 14 is transferred to each of the multiple heating tubes 13. In this way, the multiple heating tubes 13 are heated. Furthermore, in this embodiment, as described above, the storage area SA is always filled with the heat transfer medium by the accumulator AC, and as a result, the heat transfer medium in the area below the storage area SA can flow into the lower end 13D of the heating tubes 13. Therefore, as the heating tubes 13 are heated, the heat transfer medium that has flowed into the heating tubes 13 The heat transfer medium is heated. The heat transfer medium is gradually heated along the first direction X by an electric heater 14 extending in the first direction X, and as a result, the temperature increases as it goes upwards in the first direction X. That is, the density of the heat transfer medium decreases as it goes upwards in the first direction X. Therefore, natural convection of the heat transfer medium occurs in the heating tube 13, and the heat transfer medium rises inside the heating tube 13 while gradually increasing in temperature. As a result, the heat transfer medium inside the heating tube 13 becomes a high-temperature heat transfer medium HHM and reaches the upper end 13U of the heating tube 13, and flows into the storage area SA of the heat storage tank 20 via the upper end 13U. In this way, the high-temperature heat transfer medium HHM is stored in the area above the storage area SA. Each of the multiple heating tubes 13 functions as a flow path configured to allow the heat transfer medium to flow and for the high-temperature heat transfer medium HHM to flow into the heat storage tank 20 via the upper end 13U (one end) in the first direction X.

[0055] Incidentally, as described above, in this embodiment, the heat storage tank 20 is made of a material with excellent heat insulation properties, so that the transfer of heat from the heating unit 11 to the storage region SA in the second direction Y is suppressed. Therefore, a temperature stratification is formed within the storage region SA. That is, in this embodiment, in the storage region SA, in the first direction X, the high-temperature heat transfer medium HHM is stored in the upper region with the heat transfer medium MHM in between, and the low-temperature heat transfer medium LHM is stored in the lower region with the heat transfer medium MHM in between. The heat transfer medium MHM is a heat transfer medium that is lower in temperature than the high-temperature heat transfer medium HHM and higher in temperature than the low-temperature heat transfer medium LHM. Therefore, the heat transfer medium that flows into the lower end portion 13D of the heating tube 13 is the low-temperature heat transfer medium LHM. For reference, Figure 3 shows the approximate boundaries between the storage area SA where the heat transfer medium MHM is stored and the upper area (where the high-temperature heat transfer medium HHM is stored), and the approximate boundaries between the storage area SA where the heat transfer medium MHM is stored and the lower area (where the low-temperature heat transfer medium LHM is stored), both indicated by dashed lines.

[0056] Thus, according to the heat storage system 10 of this embodiment, in heat storage mode, the low-temperature heat transfer medium LHM stored in the lower region of the storage area SA of the heat storage tank 20 is heated by the heating unit 11 to become the high-temperature heat transfer medium HHM, and this high-temperature heat transfer medium HHM is stored in the upper region of the storage area SA. On the other hand, in power generation mode, the high-temperature heat transfer medium HHM is supplied to the steam generation unit 3 via the piping 6 connected to the upper region of the storage area SA, and the low-temperature heat transfer medium LHM is supplied from the steam generation unit 3 to the lower region of the storage area SA via the piping 7 connected to the lower region of the storage area SA. Furthermore, even in power generation mode, the accumulator AC maintains a state in which the storage area SA is filled with the heat transfer medium.

[0057] As described above, the heat storage system 10 of this embodiment comprises a heat storage tank 20 (tank) configured to store a heat transfer medium and extending in a first direction X, and a heating unit 11 configured to heat the heat transfer medium and in contact with the heat storage tank 20 in a second direction Y intersecting the first direction X. The heating unit 11 includes one or more heating tubes 13 (flow channels) configured through which the heat transfer medium flows and through which the high-temperature heat transfer medium HHM flows into the heat storage tank 20, and one or more electric heaters 14 configured to heat the heating tubes 13. In the first direction X, the heating tubes 13 and electric heaters 14 extend over approximately the entire length of the heat storage tank 20.

[0058] In the heat storage system 10 of this embodiment, the heating tube 13 (flow path) and electric heater 14 constituting the heating unit 11 extend over a long distance, approximately the entire length of the heat storage tank 20 in the first direction X. Even in this case, since the heating unit 11 is in contact with the heat storage tank 20 in the second direction Y, the heat storage tank 20 acts as a support, and the electric heater 14 and heating tube 13 are stably erected in the first direction X. Furthermore, in the heat storage system 10, since the electric heater 14 and heating tube 13 extending over a long distance in the first direction X are stably erected in the first direction X, the heat transfer medium flowing through the heating tube 13 along the first direction X can be heated by the electric heater 14 over a long distance in the first direction X. Moreover, in the heat storage system 10, the heat storage tank 20 and the heating unit 11 are in the second direction Because the heat storage tank 20 and the heating unit 11 are in contact at point Y, piping is not required to transfer the high-temperature heat transfer medium HHM generated in the heating unit 11 to the heat storage tank 20, thus preventing a drop in the temperature of the heat transfer medium caused by flowing through such piping. Therefore, with the heat storage system 10, it is possible to efficiently raise the temperature of the heat transfer medium using the electric heater 14 in heat storage power generation.

[0059] Furthermore, in the heat storage system 10 of this embodiment, since the heating unit 11 is in contact with the outer surface 21A of the heat storage tank 20 in the second direction Y, the wall portion 21 of the heat storage tank 20 prevents the heat from the heating unit 11 from being transferred along the second direction Y to the heat transfer medium stored in the heat storage tank 20. As a result, in the heat storage system 10, as described above, a temperature stratification is formed within the storage region SA, and the low-temperature heat transfer medium LHM is stored in the region below the storage region SA. Therefore, with the heat storage system 10, since both the high-temperature heat transfer medium HHM and the low-temperature heat transfer medium LHM are contained in one heat storage tank 20, there is no need to provide a separate tank for storing the low-temperature heat transfer medium LHM in the heat storage power generation system 1.

[0060] Furthermore, in the heat storage system 10 of this embodiment, the lower end 13D (the other end in the first direction) of the heating tube 13 (flow channel) is configured to allow the low-temperature heat transfer medium LHM stored in the heat storage tank 20 to flow in. As a result, the low-temperature heat transfer medium LHM stored in the heat storage tank 20 is heated to a high temperature in the heating tube 13, and then the high-temperature heat transfer medium HHM can be returned to the upper side of the storage area SA via the upper end 13U (the other end in the first direction) of the heating tube 13. Consequently, in the heat storage mode, in conjunction with the action of the accumulator AC, the storage area SA of the heat storage tank 20 is always kept full.

[0061] Furthermore, in the heat storage system 10 of this embodiment, since the multiple electric heaters 14 are uniformly arranged, the multiple heating tubes 13 can be heated uniformly, and as a result, the heat transfer medium can be heated to a high temperature more efficiently. In addition, in the heat storage system 10, since the multiple electric heaters 14 are not localized, localized overheating of some of the electric heaters 14 is suppressed.

[0062] However, the arrangement and configuration of the multiple heating tubes 13 and the multiple electric heaters 14 can be changed as appropriate; for example, the multiple electric heaters 14 do not need to be uniformly arranged.

[0063] (Variation 1) Furthermore, a heat storage system 10A according to Modification 1, as shown in Figure 4, may also be constructed. Figure 4 is a schematic cross-sectional view in the second direction Y showing the heat storage system 10A. In Figure 4, components similar to those in the heat storage system 10 are denoted by the same reference numerals as in Figure 2. As shown in Figure 4, in the heat storage system 10A, a planar electric heater 114 is used instead of a rod-shaped electric heater 14. That is, the heat storage system 10A comprises a heating unit 111 including a plurality of heating tubes 13 and a plurality of planar electric heaters 114. In the first direction X, the electric heater 114 extends over approximately the entire length of the heat storage tank 20 (approximately the entire length of the wall portion 21). The electric heater 114 has a cylindrical shape, and the thickness of the electric heater 114 (the difference between the outer diameter and the inner diameter) may be approximately the same as, for example, the outer diameter of the heating tube 13. Therefore, the electric heater 114 has a thin shape based on its total length in the first direction X.

[0064] The heating unit 111 includes an electric heater 114 (first electric heater 114) that is in contact with the outer peripheral surface 21A of the wall portion 21 of the heat storage tank 20 and surrounds the outer peripheral surface 21A all around, a plurality of heating tubes 13 (first heating tube group) that are in contact with the outer peripheral surface of the first electric heater 114 and surround the first electric heater 114 all around, and an electric heater that is in contact with the first heating tube group and surrounds the first heating tube group from the outside all around. It is equipped with a heater 114 (second electric heater 114). According to this modified example 1, since the electric heater is formed in a planar shape, the number of electric heaters included in the heating unit can be reduced.

[0065] In Modification 1, the number of electric heaters 114 is not limited to two; there may be only one (only the first electric heater 114), or there may be three or more. For example, if there are three electric heaters 114, multiple heating tubes 13 (second heating tube group) may be arranged outside the second electric heater 114, and the third electric heater 114 may be arranged outside the second heating tube group. In addition, an insulating material (not shown) may be placed outside the outermost electric heater 114. Such insulating material suppresses heat leakage from the heating unit 111 to the outside, and as a result, the heat transfer medium can be heated to a higher temperature more efficiently.

[0066] (Second Embodiment) Next, a heat storage system according to the second embodiment will be described. Figure 5 is a diagram illustrating the heat storage system 210 according to this embodiment, and schematically shows a cross-section of the heat storage system 210 in the second direction Y. Figure 6 is a diagram illustrating the heat storage system 210, and schematically shows a cross-section of the heat storage system 210 in the first direction X. In Figures 5 and 6, components similar to those in the first embodiment are denoted by the same reference numerals as in Figures 2 and 3, thereby omitting redundant explanations. The heat storage system 210 can be applied to the heat storage power generation system 1 as a substitute for the heat storage system 10 according to the first embodiment shown in Figure 1.

[0067] As shown in Figures 5 and 6, the heat storage system 210 comprises a heat storage tank 20, a heating unit 211, and an insulating section 201. In other words, the heat storage system 210 differs from the heat storage system 10 in that the configuration of the heating unit 211 is different from that of the heating unit 11, and that it includes an insulating section 201.

[0068] The heating unit 211 is in contact with the inner circumferential surface 21B of the wall portion 21 of the heat storage tank 20 in the second direction Y. This heating unit 211 includes a plurality of heating tubes 213 (flow channels) and a plurality of electric heaters 214. For convenience, in Figures 5 and 6, only some of the heating tubes 213 and electric heaters 214 that constitute the heating unit 211 are shown. In Figure 5, heating tubes 213 and electric heaters 214 that are not shown are indicated by dots.

[0069] Each of the multiple heating tubes 213 is made of a material with excellent thermal conductivity, such as a steel pipe, or more specifically, a carbon steel pipe. The dimensions of each of the multiple heating tubes 213 can be selected as appropriate, but for example, the diameter (outer diameter) may be about 5.4 mm and the height (total length in the first direction X) may be slightly less than 40 m. In this embodiment, the height of the heating tubes 213 may be slightly lower than the heat storage tank 20 (wall portion 21), for example, about 38 m. That is, each of the multiple heating tubes 213 extends over approximately the entire length of the heat storage tank 20 (wall portion 21) in the first direction X, but the upper end 213U (one end in the first direction X) of each of the multiple heating tubes 213 is located slightly lower than the upper wall 21U of the heat storage tank 20 (wall portion 21). Furthermore, since the diameter of the heating tube 213 is smaller than the height of the heating tube 213, the heating tube 213 has an elongated shape.

[0070] As shown in Figure 6, the lower end 213D of the heating tube 213 (the other end in the first direction X) is configured to be in fluid communication with the lower region of the storage area SA of the heat storage tank 20. Therefore, the heat transfer medium stored in the lower region of the storage area SA can flow into the heating tube 213 from the lower end 213D. In this embodiment, the lower end 213D is configured such that it moves from the lower side (the other side) to the upper side (the one side) in the first direction X, and in the second direction Y. It slopes inward, bulging outwards.

[0071] As shown in Figures 5 and 6, in this embodiment, each of the multiple electric heaters 214 is formed in a rod shape. The electric heater 214 is not particularly limited, but in this embodiment, it is configured as a so-called sheathed heater. That is, each of the multiple electric heaters 214 has a configuration in which a heating element 215 is housed inside a pipe 16. The heating element 215 is not particularly limited, but for example, it may be a coiled nichrome wire. The dimensions of each of the multiple electric heaters 214 can be selected as appropriate, but for example, the diameter (outer diameter) may be about 5.4 mm and the height (total length in the first direction X) may be about 40 m. Each of the multiple electric heaters 214 extends over approximately the entire length of the heat storage tank 20 (wall portion 21) in the first direction X. Also, since the diameter of the electric heater 14 is small compared to the height of the electric heater 214, the electric heater 214 has an elongated shape.

[0072] As shown in Figure 6, in this embodiment, in the first direction X, the total length of the heating element 215 is shorter than the total length of the electric heater 14 (the total length of the pipe 16). That is, in this embodiment, the lower end 215D of the heating element 215 is above the lower end 16D of the pipe 16. Wiring 17 may be connected to, for example, the upper end of the heating element 215, and power may be supplied to the heating element 215 from the power supply unit 8 via this wiring 17. The electric heater 214 heats up when power is supplied to the heating element 215 and the heating element 215 generates heat.

[0073] As shown in Figure 5, in this embodiment, the plurality of heating tubes 213 and the plurality of electric heaters 214 are arranged inside the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21), and surround the entire circumference of the inner circumferential surface 21B. In this embodiment, the plurality of heating tubes 213 and the plurality of electric heaters 214 include a first group 211A that is in contact with the entire circumference of the inner circumferential surface 21B in the second direction Y (radial direction), a second group 211B that is inside the first group 211A and is in contact with the entire circumference of the first group 211A in the second direction Y, and a third group 211C that is inside the second group 211B and is in contact with the entire circumference of the second group 211B in the second direction Y. Furthermore, the number of groups of multiple heating tubes 213 and multiple electric heaters 214 is not limited to three; it may be one (only the first group 211A), two (the first group 211A and the second group 211B), or four or more. In this embodiment, the heating unit 211, which is composed of multiple heating tubes 213 and multiple electric heaters 214, has the multiple electric heaters 214 uniformly arranged.

[0074] For the sake of explanation, Figure 6 schematically shows a cross-section of the heat storage system 210 when the heating unit 211 consists only of the first group 211A.

[0075] As shown in Figures 5 and 6, in this embodiment, the heat insulating portion 201 is positioned inside the heating unit 211. The heat insulating portion 201 has a cylindrical shape (in this embodiment, cylindrical) and surrounds the heating unit 211 by contacting the entire inner circumference of the heating unit 211 in the circumferential direction. The heat insulating portion 201 may be placed on the upper surface 22A of the bottom 22 of the heat storage tank 20. The inner circumferential surface 201A of the heat insulating portion 201 forms most of the storage area SA. That is, in the second direction Y, the heat insulating portion 201 is positioned between the heating unit 211 and the heat transfer medium stored in the heat storage tank 20. The material forming the heat insulating portion 201 is not particularly limited as long as it has excellent heat insulating properties.

[0076] As shown in Figure 6, in this embodiment, in the first direction X, the upper end 201U of the heat insulating portion 201 is at the same position as the upper end 213U of the heating tube 213, or slightly lower than the upper end 213U. Also, in the first direction X, a portion of the lower end 201D of the heat insulating portion 201 is a notched portion 201DC. In the first direction X, the upper part of the notched portion 201DC The end 201DU is located approximately at the same position as the upper end 213DU of the lower end 213D of the heating tube 213. The lower end 213D of the heating tube 213 is inclined so that it is located inward as it approaches the upper end 213DU. The notch 201DC of the heat insulating section 201 is located inward relative to the lower end 213D of the heating tube 213. Therefore, the lower end 213D of the heating tube 213 is in fluid communication with the bottom of the storage area SA via the notch 201DC. That is, the lower end 201D of the heating tube 213 (the other end in the first direction X) is configured to allow the heat transfer medium stored in the heat storage tank 20 to flow in. In this embodiment, in the first direction X, the upper end 201DU of the notch 201DC of the heat insulating section 201 is located at the same position as the lower end 215D of the heating element 215 of the electric heater 214, or slightly below the lower end 215D.

[0077] In the heat storage mode, when power is supplied to the heating element 215, the multiple electric heaters 214 heat up, and the heat from the multiple electric heaters 214 is transferred to each of the multiple heating tubes 213. In this way, the multiple heating tubes 213 are heated. In this embodiment, the storage area SA is always filled with a heat transfer medium by the accumulator AC, so that the heat transfer medium in the area below the storage area SA can flow into the lower end 213D of the heating tube 13. Therefore, when the heating tube 213 is heated, the heat transfer medium that has flowed into the heating tube 213 is heated, causing natural convection, and the high-temperature heat transfer medium HHM flows into the storage area SA of the heat storage tank 20 via the upper end 213U (one end) of the heating tube 213. Here, as described above, in this embodiment, in the first direction X, the upper end 213U of the heating tube 213 is slightly below the upper wall 21U of the heat storage tank 20 (i.e., in this embodiment, the upper end 213U of the heating tube 213 does not penetrate the upper wall 21U), so that the high-temperature heat transfer medium HHM does not leak out of the heat storage tank 20. In this way, the high-temperature heat transfer medium HHM is stored in the upper region of the storage area SA. Each of the multiple heating tubes 213 functions as a flow path configured such that the heat transfer medium flows through it and the high-temperature heat transfer medium HHM flows into the heat storage tank 20 via the upper end 213U (one end) in the first direction X.

[0078] Incidentally, as described above, in this embodiment, the heat insulating portion 201 is positioned above the upper end 213DU of the lower end 213D of the heating tube 213. Therefore, the transfer of heat from the electric heater 214 generated above the upper end 213DU of the lower end 213D of the heating tube 213 to the storage area SA is suppressed. Also, as described above, in this embodiment, in the first direction X, the upper end 201DU of the notch portion 201DC of the heat insulating portion 201 is at the same position as the lower end 215D of the heating element 215 of the electric heater 214, or slightly below the lower end 215D. In other words, in the first direction X, the lower end 215D of the heating element 215 of the electric heater 214 is at the same position as the upper end 201DU of the notch portion 201DC of the heat insulating portion 201, or slightly above it. Therefore, the transfer of heat from the electric heater 214 to the lowest region of the storage region SA (the region below the upper end 201DU of the notch 201DC of the insulating portion 201) is suppressed, as this region is in fluid communication with the lower end 213D of the heating tube 213. With this configuration, the transfer of heat from the heating unit 211 to the storage region SA along the second direction Y is suppressed, and a temperature stratification is formed within the storage region SA. Thus, in this embodiment, the low-temperature heat transfer medium LHM is stored in the lower region of the storage region SA. Consequently, the heat transfer medium flowing into the lower end 213D of the heating tube 213 is the low-temperature heat transfer medium LHM. For reference, Figure 6 shows the approximate boundary between the region where the heat transfer medium MHM is stored and the upper region (the region where the high-temperature heat transfer medium HHM is stored) and the approximate boundary between the region where the heat transfer medium MHM is stored and the lower region (the region where the low-temperature heat transfer medium LHM is stored) in the storage region SA, respectively, as dashed lines.

[0079] As described above, the heat storage system 210 of this embodiment comprises a heat storage tank 20 (tank) configured to store a heat transfer medium and extending in a first direction X, and a heating unit 211 configured to heat the heat transfer medium and in contact with the heat storage tank 20 in a second direction Y intersecting the first direction X. The heating unit 211 comprises one or more heating pipes 213 (flow channels) configured through which the heat transfer medium flows and the high-temperature heat transfer medium HHM flows into the heat storage tank 20. The system includes one or more electric heaters 214 configured to heat the heating tube 213, and in a first direction X, the heating tube 213 and the electric heaters 214 extend over approximately the entire length of the heat storage tank 20.

[0080] In the heat storage system 210 of this embodiment, the heating tube 213 (flow channel) and electric heater 214 constituting the heating unit 211 extend over a long distance, approximately the entire length of the heat storage tank 20 in the first direction X. Even in this case, since the heating unit 211 is in contact with the heat storage tank 20 in the second direction Y, the heat storage tank 20 acts as a support, and the electric heater 214 and heating tube 213 are stably erected in the first direction X. Furthermore, in the heat storage system 210, since the electric heater 214 and heating tube 213 extending over a long distance in the first direction X are stably erected in the first direction X, the heat transfer medium flowing through the heating tube 213 along the first direction X can be heated by the electric heater 214 over a long distance in the first direction X. Furthermore, with the thermal energy storage system 210, the thermal energy storage tank 20 and the heating unit 211 are in contact in the second direction Y, and thus the thermal energy storage tank 20 and the heating unit 211 are integrated. Therefore, piping is not required to transfer the high-temperature heat transfer medium HHM generated in the heating unit 211 to the thermal energy storage tank 20, and the temperature drop of the heat transfer medium caused by flowing through such piping is prevented. Accordingly, with the thermal energy storage system 210, it is possible to efficiently raise the temperature of the heat transfer medium using the electric heater 214 in thermal energy storage power generation.

[0081] Furthermore, in the heat storage system 210 of this embodiment, since the heating unit 211 is in contact with the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21) in the second direction Y, heat leakage from the electric heater 214 to the outside is suppressed, and the heat transfer medium can be heated to a higher temperature more efficiently.

[0082] Furthermore, in the heat storage system 210 of this embodiment, since an insulating section 201 is arranged between the heating unit 211 and the heat transfer medium stored in the heat storage tank 20 in the second direction Y, the transfer of heat from the heating unit 211, which is located inside the wall portion 21 of the heat storage tank 20, to the heat transfer medium stored in the heat storage tank 20 along the second direction Y is suppressed. As a result, with the heat storage system 210, a temperature stratification is formed in the heat transfer medium stored in the heat storage tank 20, and the low-temperature heat transfer medium LHM is stored in the region below the storage region SA. Therefore, with the heat storage system 210, since both the high-temperature heat transfer medium HHM and the low-temperature heat transfer medium LHM are contained in one heat storage tank 20, a tank for storing the low-temperature heat transfer medium LHM can be omitted in the heat storage power generation system 1.

[0083] Furthermore, in the heat storage system 210 of this embodiment, the lower end 213D (the other end in the first direction) of the heating tube 213 (flow channel) is configured to allow the low-temperature heat transfer medium LHM stored in the heat storage tank 20 to flow in. As a result, the low-temperature heat transfer medium LHM stored in the heat storage tank 20 can be heated to a high temperature in the heating tube 213, and then the high-temperature heat transfer medium HHM can be returned to the upper side of the storage area SA via the upper end 213U (the other end in the first direction) of the heating tube 213. Consequently, in the heat storage mode, the liquid level in the storage area SA of the heat storage tank 20 is kept approximately constant, and the occurrence of unnecessary space in the storage area SA is suppressed.

[0084] In this embodiment as well, as described in Modification 1, the rod-shaped electric heater 214 may be changed to a planar electric heater.

[0085] (Third embodiment) Next, a heating unit according to the third embodiment will be described. Figure 7 is a diagram illustrating the heating unit elements constituting the heating unit according to this embodiment, and schematically shows a cross-section of the heating unit elements in the first direction X. Figure 7 shows a heating unit element 311A ​​that constitutes a heating unit 311 which replaces the heating unit 211 in the heat storage system 210 according to the second embodiment. In Figure 7, the same configuration as in the second embodiment The same reference numerals are used for these elements as in Figures 5 and 6, thereby omitting redundant explanations.

[0086] The heating unit 311 includes one or more heating unit elements 311A, as shown in Figure 7, which are erected in a first direction X while in contact with the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21). For example, the heating unit 311 may be configured by arranging a plurality of heating unit elements 311A ​​in contact with the inner circumferential surface 21B along the circumferential direction of the inner circumferential surface 21B (for example, all around).

[0087] In addition, the heating unit 311 may be replaced by the heating unit 11 in the heat storage system 10 according to the first embodiment. In this case, the heating unit 311 includes one or more heating unit elements 311A ​​shown in Figure 7, which are erected in the first direction X while in contact with the outer peripheral surface 21A of the heat storage tank 20 (wall portion 21).

[0088] As shown in Figure 7, the heating unit element 311A ​​includes one heating tube 313 (flow channel), a plurality of rod-shaped electric heaters 214, and a plurality of reinforcing members 318.

[0089] The heating tube 313 may be formed with larger dimensions (outer diameter) than the heating tube 213 according to the second embodiment, and extends over approximately the entire length of the heat storage tank 20 (wall portion 21) in the first direction X. Although not shown in the figures, the lower end of the heating tube 313 (the other end in the first direction X) is configured to allow the low-temperature heat transfer medium LHM stored in the heat storage tank 20 to flow in. Multiple rod-shaped electric heaters 214 are housed inside one heating tube 313 (flow channel).

[0090] Each of the multiple reinforcing members 318 may be made of a material that is highly rigid, resistant to high temperatures, and resistant to corrosion by the heat transfer medium, and may be formed in the form of a thin plate. Each of the multiple reinforcing members 318 connects the inner circumferential surface of the heating tube 313 to some of the multiple electric heaters 214. In the example shown in Figure 7, the multiple reinforcing members 318 are arranged in a grid pattern. With such multiple reinforcing members 318, the multiple electric heaters 214 arranged inside one heating tube 313 are stably erected. Here, since the heat transfer medium flows along the first direction X, it can flow inside the heating tube 313 without being obstructed by the reinforcing members 318 even when the reinforcing members 318 are arranged as in Figure 7.

[0091] The total length of the reinforcing member 318 in the first direction X may be about the same as that of the heating tube 313, and the reinforcing member 318 may be arranged continuously without interruption in the first direction X, or it may be shorter than that of the heating tube 313, and multiple reinforcing members 318 may be arranged intermittently in the first direction X.

[0092] According to this embodiment, since multiple electric heaters 214 can be housed within a single heating tube 313 (flow path), the number of heating tubes 313 (flow paths) constituting the heating unit 311 can be reduced.

[0093] Furthermore, the reinforcing member 318 may be made of a material with excellent thermal conductivity. In this case, in addition to the electric heater 214, the heat transfer medium flowing through the heating tube 313 is also heated by the reinforcing member 318, making it possible to raise the temperature of the heat transfer medium more efficiently. In other words, the reinforcing member 318 can perform a function of promoting heat transfer.

[0094] (Modification 2) Furthermore, as a modified example of the heating unit element 311A ​​(modification example 2), the heating unit element 311Aa shown in Figure 8 may be constructed. The heating unit element 311Aa is constructed using a single reinforcing member 318A as a substitute for the reinforcing member 318. The reinforcing member 318A is rigid The reinforcing member 318 may be made of a material that is highly durable, resistant to high temperatures, and resistant to corrosion by the heat transfer medium, and has a honeycomb shape. The reinforcing member 318 is fixed to the inner circumferential surface of one heating tube 313. As a result, multiple compartments 318AG are formed in a grid pattern inside the heating tube 313. One electric heater 214 is housed in each of these compartments 318AG. Thus, in the modified example 2, multiple electric heaters 214 are housed inside one heating tube 313 (flow channel). Even with this modified example 2, multiple electric heaters 214 arranged inside one heating tube 313 can be stably erected, and the number of heating tubes 313 (flow channels) constituting the heating unit 311 can be reduced.

[0095] (Fourth Embodiment) Next, a heat storage system according to the fourth embodiment will be described. Figure 9 is a diagram illustrating the heat storage system 410 according to this embodiment, and schematically shows a cross-section of the heat storage system 410 in the second direction Y. In Figure 9, components similar to those described in the first to third embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0096] As shown in Figure 9, the heat storage system 410 of this embodiment comprises a heat storage tank 20, a heating unit 411, and an insulating section 201. The heating unit 411 is in contact with the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21) in the second direction Y, and the insulating section 201 is positioned inside the heating unit 411. Therefore, the heating unit 411 can be considered a substitute for the heating unit 211 of the second embodiment (see Figure 5).

[0097] The heating unit 411 includes one flow path 413 and a plurality of rod-shaped electric heaters 214 arranged inside the one flow path 413. In this embodiment, one flow path 413 is formed as a space between the heat insulating section 201 and the wall 21 of the heat storage tank 20. As described in the second embodiment, the heat insulating section 201 has a cylindrical shape and is placed on the upper surface 22A of the bottom 22 of the heat storage tank 20, so it is stably upright in the first direction X. Therefore, the flow path 413, which is the space between the heat insulating section 201 and the wall 21 of the heat storage tank 20, can also be interpreted as being stably upright in the first direction X. Furthermore, as described above, since the flow path 413 is the space between the heat insulating section 201 and the wall 21 of the heat storage tank 20, it extends over approximately the entire length of the heat storage tank 20 (wall 21) in the first direction X.

[0098] Incidentally, although not shown in Figure 9, reinforcing members such as the reinforcing member 318 shown in Figure 7 or the reinforcing member 318A shown in Figure 8 may be placed within the flow path 413. With such reinforcing members, multiple electric heaters 214 are stably erected within the flow path 413 along the first direction X.

[0099] The lower end of the flow path 413 (the other end in the first direction X) is in fluid communication with the lowest part of the storage area SA of the heat storage tank 20 (the area below the upper end 201DU of the notch 201DC) via the notch 201DC of the heat insulating section 201 (see Figure 6). In other words, the lower end of the flow path 413 (the other end in the first direction X) is configured to allow the low-temperature heat transfer medium LHM stored in the heat storage tank 20 to flow in. The low-temperature heat transfer medium LHM that flows into the lower end of the flow path 413 flows upward within the flow path 413 and is heated by the electric heater 214 located within the flow path 413 to become the high-temperature heat transfer medium HHM. This high-temperature heat transfer medium HHM then flows into the heat storage tank 20 via the upper end of the flow path 413 (the one end in the first direction X).

[0100] The heat storage system 410 of this embodiment can achieve the same effects as the heat storage system 210 of the second embodiment. Furthermore, since the heating unit 411 of the heat storage system 410 of this embodiment can be formed by a single flow path 413, the number of flow paths (heating tubes) can be reduced.

[0101] (Fifth embodiment) Next, a heat storage system according to the fifth embodiment will be described. Figure 10 is a diagram illustrating the heat storage system 510 according to this embodiment, and schematically shows a cross-section of the heat storage system 510 in the second direction Y. In Figure 10, components similar to those described in the first to fourth embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0102] As shown in Figure 10, the heat storage system 510 of this embodiment comprises a heat storage tank 20 and a heating unit 511. The heating unit 511 is in contact with the outer peripheral surface 21A of the heat storage tank 20 (wall portion 21) in the second direction Y. Therefore, the heating unit 511 can be considered a substitute for the heating unit 11 of the first embodiment (see Figure 2).

[0103] The heating unit 511 is composed of one or more heating unit elements 511A. In the example shown in Figure 10, multiple heating unit elements 511A are arranged along the circumferential direction of the outer surface 21A of the heat storage tank 20 (wall portion 21). That is, in this embodiment, the heat storage tank 20 is surrounded from the outside by the heating unit 511, which consists of multiple heating unit elements 511A. Each of the multiple heating unit elements 511A is in contact with the outer surface 21A of the heat storage tank 20 (wall portion 21).

[0104] Figure 11 is a diagram illustrating the heating unit element 511A. In Figure 11, components similar to those described in the first to fourth embodiments are denoted by the same reference numerals, and redundant explanations are omitted.

[0105] As shown in Figure 11, the heating unit element 511A has a roughly rectangular parallelepiped shape overall, in which the length (width) in the second direction Y is smaller than the length (height) in the first direction X. The heating unit element 511A includes a plurality of planar electric heaters 514, a plurality of heating tubes 13 (flow channels), and two heat insulating sections 501.

[0106] The electric heater 514 extends along approximately the entire length of the (wall portion 21) of the heat storage tank 20 in the first direction X. The thickness (length in the second direction Y) of the electric heater 514 is smaller than the height (total length in the first direction X), and may be, for example, about the same size as the diameter (outer diameter) of the heating tube 13. Figure 11 shows an example in which the heating unit element 511A includes four electric heaters 514. The multiple electric heaters 514 are arranged in the second direction Y.

[0107] In the second direction Y, some of the heating tubes 13 are arranged between adjacent electric heaters 514, 514 in the third direction Z, which is perpendicular to the first direction X and the second direction Y. In the first direction X, the total length of each of the heating tubes 13 is approximately equal to the total length of the electric heater 514. Although not shown in Figure 11 for convenience, the upper end 13U of the heating tube 13 (one end in the first direction X) is formed to slope diagonally downward from slightly above the upper wall 21U of the heat storage tank 20 (wall portion 21) toward the inside of the wall portion 21, as described in the first embodiment (see Figure 3).

[0108] The two insulation sections 501 include an insulation section 501 ("inner insulation section 501") positioned on the inside of the innermost electric heater 514 ("inner electric heater 514") among the multiple electric heaters 514, and an insulation section 501 ("outer insulation section 501") positioned on the outside of the outermost electric heater 514 ("outer electric heater 514" among the multiple electric heaters 514). The insulation section 501 is formed in a plate shape. The material used to form the insulation section 501 is not particularly limited as long as it has excellent heat insulation properties. The outer surface of the inner insulation section 501 is in general complete contact with the inner surface of the inner electric heater 514, and the inner surface of the outer insulation section 501 is in general complete contact with the outer surface of the outer electric heater 514. The thickness (length in the second direction Y) is smaller than the height of the heat insulating section 501 (total length in the first direction X), and may be, for example, about the same size as the thickness of the electric heater 514.

[0109] As shown in Figure 10, the heating unit element 511A extends in the first direction X over approximately the entire length of the heat storage tank 20 (wall portion 21) with the inner surface 501A of the inner insulation portion 501 in contact with the outer surface 21A of the heat storage tank 20 (wall portion 21).

[0110] According to the heat storage system 510, which includes a heating unit 511 consisting of one or more heating unit elements 511A having the above-described configuration, the same effects as the heat storage system 10 of the first embodiment can be obtained.

[0111] Furthermore, with the heat storage system 510, since the heat insulation sections 501 are arranged on both sides of the heating unit element 511A in the second direction Y, heat leakage from the electric heater 514 to the outside is suppressed, and as a result, the heat transfer medium can be heated to a higher temperature more efficiently. In addition, with the heat storage system 510, since the electric heater 514 of the heating unit element 511A is formed in a planar shape, the number of electric heaters can be reduced.

[0112] Furthermore, as described above, the heating unit element 511A is formed in a rectangular parallelepiped shape by arranging multiple electric heaters 514, multiple heating tubes 13 (flow channels), and two heat insulating sections 501 in the second direction Y, so the heating unit element 511A itself can stand on its own. In the heat storage system 510, the heating unit element 511A is erected in contact with the outer surface 21A of the wall section 21, which allows for a more stable arrangement of the heating unit.

[0113] In this embodiment, an example in which the heating unit 511 is composed of multiple heating unit elements 511A has been described, but the heating unit 511 may also be composed of a single heating unit element 511A. For example, the heating unit 511 may be composed of a single heating unit element 511A shown in Figure 11. Alternatively, the heating unit 511 may be composed of a single cylindrical heating unit element 511A by forming the heating unit element 511A in a cylindrical shape so as to surround the entire circumference of the outer peripheral surface 21A of the wall portion 21.

[0114] (Sixth Embodiment) Next, a thermal energy storage power generation system according to the sixth embodiment will be described. Figure 12 is a schematic diagram showing the thermal energy storage power generation system 600 of this embodiment. As shown in Figure 12, the thermal energy storage power generation system 600 of this embodiment differs from the thermal energy storage power generation system 1 in that it includes a tank 601 for storing the low-temperature heat transfer medium LHM (hereinafter referred to as the "low-temperature tank 601"), but the other configurations are generally the same as those of the thermal energy storage power generation system 1 of the first embodiment. Therefore, in Figure 12, the same reference numerals are used for components that are the same as those of the thermal energy storage power generation system 1, and redundant explanations are omitted.

[0115] As shown in Figure 12, the thermal energy storage power generation system 600 of this embodiment is a system for performing thermal energy storage power generation, and the electricity generated by the thermal energy storage power generation system 600 may be supplied to consumers 9, etc. The thermal energy storage power generation system 600 mainly comprises a power generation unit 2, a steam generation unit 3, a thermal energy storage system 610, a low-temperature tank 601 as a tank, piping 602, a pump P, and a power supply unit 8. The power supply unit 8 is capable of supplying power to the heating element 15 of the thermal energy storage system 610.

[0116] In the thermal energy storage power generation system 600, in power generation mode, a high-temperature heat transfer medium HHM is supplied from the thermal energy storage system 610 to the steam generation unit 3 through piping 6, while a low-temperature heat transfer medium LHM is supplied from the steam generation unit 3 to the low-temperature tank 601 through piping 607. In the heat storage mode, the low-temperature heat transfer medium LHM stored in the low-temperature tank 601 flows into the piping 602 through the action of the pump P and is supplied to the heat storage system 610 via the piping 602. This low-temperature heat transfer medium LHM is then heated in the heat storage system 610 to become the high-temperature heat transfer medium HHM, and this high-temperature heat transfer medium HHM is stored in the storage area SA of the heat storage tank 20 of the heat storage system 610.

[0117] Figure 13 is a diagram illustrating the heat storage system 610, and schematically shows a cross-section of the heat storage system 610 in a first direction X. In Figure 13, components similar to those described in the first to fifth embodiments are denoted by the same reference numerals, and redundant explanations are omitted. As shown in Figure 13, the heat storage system 610 comprises a heat storage tank 20 as a tank and a heating unit 611.

[0118] The heating unit 611 is in contact with the inner circumferential surface 21B of the wall portion 21 of the heat storage tank 20 in the second direction Y. This heating unit 611 includes a plurality of heating tubes 613 (flow channels) and a plurality of electric heaters 14. The plurality of heating tubes 613 and the plurality of electric heaters 14 are arranged inside the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21) and surround the entire circumference of the inner circumferential surface 21B. The plurality of heating tubes 613 and the plurality of electric heaters 14 may include a first group that is in contact with the entire circumference of the inner circumferential surface 21B in the second direction Y (radial direction), a second group that is inside the first group and is in contact with the entire circumference of the first group in the second direction Y, and one or more groups that are further inside the second group (see Figure 5). In addition, the plurality of electric heaters 14 may be uniformly arranged in the heating unit 611. For convenience, Figure 13 shows one of the multiple heating tubes 613 that make up the heating unit 611 and one of the multiple electric heaters 14 that make up the heating unit 611.

[0119] Each of the multiple heating tubes 613 is made of a material with excellent thermal conductivity, such as a steel pipe, or more specifically, a carbon steel pipe. The dimensions of each of the multiple heating tubes 613 can be selected as appropriate, for example, the diameter (outer diameter) may be about 5.4 mm and the height may be slightly less than 40 mm. In this embodiment, the height of the heating tubes 613 may be slightly lower than the heat storage tank 20 (wall portion 21), for example, about 38 mm. That is, each of the multiple heating tubes 613 extends over approximately the entire length of the heat storage tank 20 (wall portion 21) in the first direction X, but the upper end 613U of each of the multiple heating tubes 613 (one end in the first direction X) is located slightly lower than the upper wall 21U of the heat storage tank 20 (wall portion 21). Also, since the diameter of the heating tubes 613 is small compared to the height of the heating tubes 613, the heating tubes 613 have an elongated shape.

[0120] The lower end 613D of the heating tube 613 (the other end in the first direction X) is configured to be in fluid communication with the piping 602. Therefore, the low-temperature heat transfer medium LHM flowing through the piping 602 by the pump P can flow into the heating tube 613 via the lower end 613D.

[0121] In the heat storage mode, when power is supplied to the heating element 15, the multiple electric heaters 14 heat up, and the heat from the multiple electric heaters 14 is transferred to each of the multiple heating tubes 613. In this way, the multiple heating tubes 613 are heated. As described above, the low-temperature heat transfer medium LHM stored in the low-temperature tank 601 flows into the multiple heating tubes 613 through their respective lower ends 613D (the other end). Therefore, as the heating tubes 613 are heated, the low-temperature heat transfer medium LHM that has flowed into the heating tubes 613 is heated, and by natural convection becomes a high-temperature heat transfer medium HHM, which reaches the upper end 613U (the other end) of the heating tube 613, and this high-temperature heat transfer medium HHM flows into the storage area SA of the heat storage tank 20 through the upper end 613U (the other end). Here, as described above, in this embodiment, in the first direction X, the upper end 613U of the heating tube 613 is the heat storage tank Because it is located slightly below the upper wall 21U of 20, leakage of the high-temperature heat transfer medium HHM outwards from the heat storage tank 20 is suppressed. In this way, the high-temperature heat transfer medium HHM is stored in the storage area SA. Each of the multiple heating tubes 613 functions as a flow path through which the heat transfer medium flows, and the high-temperature heat transfer medium HHM flows into the heat storage tank 20 via the upper end 613U (one end) in the first direction X.

[0122] On the other hand, in power generation mode, high-temperature heat transfer medium HHM is supplied from the storage area SA of the heat storage tank 20 to the steam generation unit 3 via piping 6, and low-temperature heat transfer medium LHM is supplied from the steam generation unit 3 to the low-temperature tank 601 via piping 607.

[0123] As described above, the heat storage system 610 of this embodiment comprises a heat storage tank 20 (tank) configured to store a heat transfer medium and extending in a first direction X, and a heating unit 611 configured to heat the heat transfer medium and in contact with the heat storage tank 20 (tank) in a second direction Y intersecting the first direction X. The heating unit 611 includes one or more heating tubes 613 (flow channels) configured through which the heat transfer medium flows and through which the high-temperature heat transfer medium HHM flows into the heat storage tank 20 (tank), and one or more electric heaters 14 configured to heat the heating tubes 613. In the first direction X, the heating tubes 613 and electric heaters 14 extend over approximately the entire length of the heat storage tank 20 (tank).

[0124] In the heat storage system 610 of this embodiment, the heating tube 613 (flow channel) and electric heater 14 constituting the heating unit 611 extend over a long distance, approximately the entire length of the heat storage tank 20 in the first direction X. Even in this case, since the heating unit 611 is in contact with the heat storage tank 20 in the second direction Y, the electric heater 14 and heating tube 613 are stably erected in the first direction X. Furthermore, in the heat storage system 610, since the electric heater 14 and heating tube 613 extending over a long distance in the first direction X are stably erected in the first direction X, the heat transfer medium flowing through the flow channel along the first direction X can be heated by the electric heater 14 over a long distance in the first direction X. Furthermore, with the thermal energy storage system 610, the thermal energy storage tank 20 and the heating unit 611 are in contact in the second direction Y, and thus the thermal energy storage tank 20 and the heating unit 611 are integrated. Therefore, piping is not required to transfer the high-temperature heat transfer medium HHM generated in the heating unit 611 to the thermal energy storage tank 20, and the temperature drop of the heat transfer medium caused by flowing through such piping is prevented. Accordingly, with the thermal energy storage system 610, it is possible to efficiently raise the temperature of the heat transfer medium using an electric heater in thermal energy storage power generation.

[0125] Incidentally, in this embodiment, unlike the second embodiment, there is no heat insulating section inside the heating unit 611. Therefore, the heat generated in the heating unit 611 is transferred to the storage area SA along the second direction Y. Accordingly, according to this embodiment, a high-temperature heat transfer medium HHM can be stored at a generally constant temperature throughout the entire storage area SA.

[0126] Furthermore, in this embodiment, the low-temperature heat transfer medium LHM stored in the low-temperature tank 601 is circulated to the heating pipe 613 erected in the heat storage tank 20 by a pump P provided in the piping 602. Therefore, unlike the first to fifth embodiments, the low-temperature heat transfer medium LHM can be circulated to the heating pipe 613 without a mechanism to fill the storage area with the heat transfer medium, such as an accumulator AC.

[0127] Furthermore, in this embodiment, since the flow of the heat transfer medium within the heating tube 613 is by natural convection, there is no need to circulate the heat transfer medium within the heating tube 613 using the power of the pump P. Therefore, according to this embodiment, it is possible to perform the heat storage mode by reducing the suction force of the pump P.

[0128] In this sixth embodiment, an example was described in which the heating unit 611 is in contact with the inner circumferential surface 21B of the heat storage tank 20 (wall portion 21). However, the heating unit 611 may also be in contact with the outer circumferential surface 21A of the heat storage tank 20 (wall portion 21).

[0129] (Variation 3) Furthermore, although the sixth embodiment described an example in which the heating unit 611 is erected on the heat storage tank 20 which serves as a tank, a modified example (modification 3) may be constructed in which the heating unit 611 is erected on the inner or outer surface of the low-temperature tank 601 which serves as a tank. Modification 3 will be described below.

[0130] Figure 14 is a schematic diagram showing the thermal energy storage power generation system 600A of the modified example 3. In Figure 14, components similar to those in the thermal energy storage power generation system 1,600 are denoted by the same reference numerals, and redundant explanations are omitted. As shown in Figure 14, in the thermal energy storage power generation system 600A, in the heat storage mode, the low-temperature heat transfer medium LHM stored in the low-temperature tank 601 is heated by a heating pipe erected in the low-temperature tank 601 to become a high-temperature heat transfer medium HHM, and this high-temperature heat transfer medium HHM flows through the pipe 602 by the action of a pump P provided in the pipe 602 and is stored in the thermal energy storage tank 20. That is, in the thermal energy storage power generation system 600A, the thermal energy storage system 610A includes a low-temperature tank 601 configured to store the heat transfer medium and extending in a first direction, and a heating unit configured to heat the heat transfer medium and in contact with the low-temperature tank 601 in a second direction Y that intersects the first direction X.

[0131] Figure 15 is a diagram illustrating the heat storage system 610A, and schematically shows a cross-section of the heat storage system 610A in a first direction X. In Figure 15, components similar to those described in the first to sixth embodiments are denoted by the same reference numerals, and redundant explanations are omitted. As shown in Figure 15, the heat storage system 610A comprises a low-temperature tank 601 as a tank and a heating unit 11.

[0132] As described in the first embodiment, the heating unit 11 is in contact with the outer circumferential surface of the tank wall. In the third modified example, the heating unit 11 is in contact with the outer circumferential surface of the low-temperature tank 601 wall. That is, the heating tube 13 and electric heater 14 constituting the heating unit 11 are erected on the outer circumferential surface of the low-temperature tank 601 wall. The lower end 13D of the heating tube 13 is in communication with the storage area SA of the low-temperature tank 601. On the other hand, the upper end 13U of the heating tube 13 is near the upper end of the low-temperature tank 601 and is connected to the piping 602.

[0133] In the modified example 3, the low-temperature heat transfer medium LHM stored in the storage area SA of the low-temperature tank 601 can flow into the heating tube 13 via the lower end 13D of the heating tube 13 by the action of the pump P provided in the piping 602. In the heat storage mode, multiple heating tubes 13 are heated by multiple electric heaters 14. Therefore, the low-temperature heat transfer medium LHM that flows into the heating tube 13 from the lower end 13D is heated and becomes a high-temperature heat transfer medium HHM by natural convection, reaching the upper end 13U of the heating tube 13. The high-temperature heat transfer medium HHM then flows through the piping 602 from the upper end 13U of the heating tube 13 to the heat storage tank 20 by the action of the pump P, and is stored in the heat storage tank 20.

[0134] On the other hand, in power generation mode, high-temperature heat transfer medium HHM is supplied from the storage area SA of the heat storage tank 20 to the steam generation unit 3 via piping 6, and low-temperature heat transfer medium LHM is supplied from the steam generation unit 3 to the low-temperature tank 601 via piping 607.

[0135] As described above, the heat storage system 610A of the modified example 3 is configured to store a heat transfer medium and includes a low-temperature tank 601 (tank) extending in a first direction X, and a heating element configured to heat the heat transfer medium and in contact with the low-temperature tank 601 (tank) in a second direction Y intersecting the first direction X. The system includes a heating unit 11. The heating unit 11 includes one or more heating tubes 13 (flow channels) through which a heat transfer medium flows, causing a high-temperature heat transfer medium HHM to flow into the heat storage tank 20 (tank), and one or more electric heaters 14 configured to heat the heating tubes 13. In the first direction X, the heating tubes 13 and electric heaters 14 extend over approximately the entire length of the low-temperature tank 601 (tank).

[0136] According to Modification 3, the heating tube 13 (flow channel) and electric heater 14 constituting the heating unit 11 extend over a long distance, approximately the entire length of the low-temperature tank 601 in the first direction X. Even in this case, since the heating unit 11 is in contact with the low-temperature tank 601 in the second direction Y, the electric heater 14 and heating tube 13 are stably erected in the first direction X. Furthermore, according to Modification 3, since the electric heater 14 and heating tube 13 extending over a long distance in the first direction X are stably erected in the first direction X, the heat transfer medium flowing through the flow channel along the first direction X can be heated by the electric heater 14 over a long distance in the first direction X. Therefore, according to Modification 3, it is possible to efficiently raise the temperature of the heat transfer medium using an electric heater in thermal energy storage power generation.

[0137] Furthermore, in the third modified example, the low-temperature heat transfer medium LHM stored in the low-temperature tank 601 is circulated to the heating pipe 13 erected in the low-temperature tank 601 by a pump P provided in the piping 602. Therefore, unlike the first to fifth embodiments, the low-temperature heat transfer medium LHM can be circulated to the heating pipe 13 without a mechanism to fill the storage area with the heat transfer medium, such as an accumulator AC.

[0138] Furthermore, in Modification 3, since the circulation of the heat transfer medium within the heating tube 13 is by natural convection, there is no need to circulate the heat transfer medium within the heating tube 13 using the power of the pump P. Therefore, according to Modification 3, it is possible to reduce the suction force of the pump P and execute the heat storage mode.

[0139] In Modification 3, an example was described in which the heating unit is in contact with the outer circumferential surface of the low-temperature tank 601. However, the heating unit may also be in contact with the inner circumferential surface of the low-temperature tank 601. In this case, however, care should be taken to place an insulating section between the heating unit and the storage area SA of the low-temperature tank 601.

[0140] Although the present invention has been described above with reference to the embodiments and modifications described above, the present invention is not limited thereto.

[0141] For example, in the first to fifth embodiments described above, an example was described in which a mechanism for filling the tank with a heat transfer medium (e.g., an accumulator AC) is provided. However, if the heat transfer medium flows into the heating tube, it is not essential to provide a mechanism for filling the tank with the heat transfer medium.

[0142] Those skilled in the art can modify the heat storage system of the present invention as appropriate in accordance with conventionally known knowledge. Such modifications, insofar as they still possess the configuration of the present invention, are of course included within the scope of the present invention. [Explanation of Symbols]

[0143] 10, 10A, 210, 410, 510, 610, 610A… Heat storage system, 11, 111, 211, 311, 411, 511, 611… Heating unit, 13, 213, 313, 613… Heating tube (flow channel), 13U… Upper end (one end), 14, 114, 214, 514… Electric heater, 20… Heat storage tank (tank), 21… Wall section, 21A… Outer surface, 21B… Inner surface, 201… Insulation section, 213U… Upper end (one end), 413… Flow channel, 601… Low temperature tank (tank), 613U… Upper end (one end), HHM… High temperature heat transfer medium (heat transfer medium), LHM… Low temperature heat transfer medium (heat transfer medium), MHM… Heat transfer medium, AC… Accumulator (tank) (Mechanism filled with a heat transfer medium), X...first direction, Y...second direction

Claims

1. A heat storage system used for thermal energy storage power generation, A tank configured to store a heat transfer medium and extending in a first direction, A heating unit configured to heat the heat transfer medium and in contact with the tank in a second direction intersecting the first direction, Equipped with, The aforementioned heating unit is One or more flow paths are configured such that the heat transfer medium flows through them and the high-temperature heat transfer medium flows into the tank, One or more electric heaters configured to heat the aforementioned flow path and Includes, In the first direction, the flow path and the electric heater extend over approximately the entire length of the tank in a heat storage system.

2. The heat storage system according to claim 1, further comprising a mechanism for filling the tank with the heat transfer medium.

3. The heat storage system according to claim 1, wherein in the second direction, the heating unit is in contact with the outer circumferential surface of the tank.

4. The heat storage system according to claim 1, wherein in the second direction, the heating unit is in contact with the inner circumferential surface of the tank.

5. The heat storage system according to claim 4, wherein in the second direction, an insulating section is disposed between the heating unit and the heat transfer medium stored in the tank.

6. A temperature stratification is formed in the heat transfer medium stored in the tank, with a high-temperature heat transfer medium stored on one side in the first direction, and a heat transfer medium at a lower temperature than the high-temperature heat transfer medium stored on the other side in the first direction. The heat storage system according to any one of claims 1 to 5, wherein the other end of the flow path in the first direction is configured to allow the low-temperature heat transfer medium stored in the tank to flow into it.

7. In the second direction, the heating unit is in contact with the inner circumferential surface of the tank. The heat storage system according to claim 6, wherein the other end of the flow path in the first direction is inclined to protrude inward in the second direction as it moves from the other side to the one side in the first direction.

8. Each of the multiple electric heaters and the multiple flow channels is formed in a rod shape. The heat storage system according to any one of claims 1 to 4, wherein the electric heaters are uniformly arranged in the heating unit.

9. The heat storage system according to any one of claims 1 to 4, wherein the electric heater is formed in a planar shape.

10. A heat storage system according to any one of claims 1 to 4, wherein a plurality of the electric heaters are housed inside one of the flow channels.

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