Thermal energy storage device having temperature gradient

Abstract

The purpose of the present invention is to provide a thermal energy storage device which can smoothly store thermal energy in a single tank, and is convenient to operate and manage, and thus can be significantly expanded in utility compared to conventional thermal energy storage devices. The thermal energy storage device having a temperature gradient according to the present invention includes: a storage tank which contains heat storage fluids; a cell separation plate separating the storage tank into two or more cells; a cell connection pipe connecting an upper portion and a lower portion of neighboring cells; a low-temperature side pump for transferring a low-temperature heat storage fluid; and a high-temperature side pump for transferring a high-temperature heat storage fluid.

Description

Thermal energy storage device with temperature gradient

[0001] The present invention relates to a thermal energy storage device having a temperature gradient, and more specifically, to a thermal energy storage device having a temperature gradient that can convert high-temperature energy generated by solar energy or electricity generated by wind power, solar energy, etc. into high-temperature energy and store it.

[0002] With industrial development driving maximum energy consumption, active research is underway to prevent energy waste and utilize it more efficiently. One such area of ​​research involves energy storage systems (ESS), which store excess power generated by solar and wind power, which are difficult to balance, and then transmit it during temporary power shortages.

[0003] Molten salt systems are an example of high-temperature energy storage devices. In solar thermal systems, excess solar energy is collected to increase the temperature of synthetic oil or other materials, which are then used as a working fluid to store thermal energy in molten salt. In other words, thermal energy is stored as thermal energy. Meanwhile, solar or wind power converts excess electrical energy into thermal energy, which is then stored in molten salt. When electricity is needed, the energy stored in the high-temperature molten salt is used to generate electricity. This principle involves converting electrical energy into thermal energy for storage.

[0004] In addition to the molten salt method, batteries have traditionally been used to store electrical energy when generating power, such as solar or wind power. However, since battery storage is uneconomical when there is a large amount of surplus power, methods that convert electrical energy into thermal energy and store it are increasingly being adopted. As an example, Korean Patent Publication No. 2007-0022679 ("Method and Device for Storing Thermal Energy," February 27, 2007) discloses a device that heats the internal region of a graphite body when thermal energy needs to be stored, and recovers the heat using a heat exchanger when the thermal energy needs to be used, so as to store electrical energy or renewable energy during off-peak supply periods.

[0005] These energy storage technologies are currently undergoing active research and development, so in most cases they are designed to be optimized for their development purpose, which often results in a rather narrow range of applications. For example, the molten salt thermal storage device mentioned above is very suitable for storing high-temperature energy, especially solar thermal energy. However, to utilize it for solar or wind power, a separate device to convert electricity into heat is required, and it is not suitable for storing low-quality electrical energy, so there are many cases where it is not suitable for use. Furthermore, in the case of molten salt thermal storage devices, there is the problem of complex system configuration and operation because they store thermal energy by installing two tanks, a low-temperature storage tank and a high-temperature storage tank.

[0006] FIG. 1 illustrates a conceptual diagram of a conventional two-tank molten salt thermal energy storage system. Referring to FIG. 1, the conventional two-tank system will be described in more detail as follows. The "external heating source" in FIG. 1 literally refers to a place that collects heat to be used as energy from the outside, and can be, specifically, a solar thermal storage device, an electric heater, a nuclear reactor, etc. When the thermal storage fluid is heated by such an external heating source, the high-temperature thermal storage fluid is moved to a high-temperature tank and stored, as illustrated in FIG. 1. The high-temperature thermal storage fluid in the high-temperature tank generally forms a temperature environment of approximately 600°C. When the thermal energy of this high-temperature thermal storage fluid is transferred to an "external cooling source," the heat of the high-temperature thermal storage fluid can be transferred to a "heat source demander" using another medium. In this process, the high-temperature thermal storage fluid loses thermal energy and is "cooled," and therefore such a heat transfer device is called an "external cooling source." Meanwhile, the medium used here can be any medium that can effectively transfer heat and is economical and widely available. Specifically, water is commonly used, as shown in Figure 1. After thermal energy is supplied to the heat source demand through this medium, the low-temperature heat storage fluid, whose temperature has dropped, is moved to a low-temperature tank and stored. The low-temperature heat storage fluid within the low-temperature tank typically forms a temperature environment of approximately 200°C. This low-temperature heat storage fluid then moves to an external heat source to receive thermal energy, thereby achieving circulation of the heat storage fluid.

[0007] In this way, the conventional two-tank method uses two tanks: a high-temperature tank for storing high-temperature heat storage fluid and a low-temperature tank for storing low-temperature heat storage fluid. Accordingly, a considerable amount of space is required to install the two tanks separately, and since neither tank is completely filled, there is naturally a considerable amount of excess space at all times. Therefore, the conventional two-tank method inevitably leads to a considerable waste of space, which limits installation and capacity, and as mentioned above, there are problems such as complex configuration and operation.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] (Patent Document 1) Korean Patent Publication No. 2007-0022679 ("Method and Device for Storing Thermal Energy", February 27, 2007)

[0011] (Patent Document 2) Korean Patent Publication No. 2023-0113455 ("Electric and High-Temperature Energy Storage Device," July 31, 2023)

[0012] Accordingly, the present invention has been made to solve the problems of the prior art as described above, and the purpose of the present invention is to provide a thermal energy storage device that can smoothly store thermal energy in a single tank, is convenient to operate and manage, and thus can greatly expand the scope of application compared to the prior art. More specifically, the present invention provides a thermal energy storage device that sequentially stores thermal storage fluid in a single tank so as to have a temperature gradient by utilizing the density difference according to the temperature of the thermal storage fluid, and sequentially recovers the thermal energy so as to have a temperature distribution when necessary.

[0013] A thermal energy storage device (100) having a temperature gradient of the present invention for achieving the above-described purpose may include: a storage tank (101) in which a thermal storage fluid is stored; a cell separator (105) that separates the storage tank (101) into a plurality of cells; a cell connecting pipe (155) that connects the upper part of one cell and the lower part of the other cell among a pair of adjacent cells; a low-temperature pump (115) provided in a cell located at one end of the cells in the storage tank (101) to transport a low-temperature thermal storage fluid; and a high-temperature pump (125) provided in a cell located at the other end of the cells in the storage tank (101) to transport a high-temperature thermal storage fluid.

[0014] In addition, in the thermal energy storage device (100), a cell located at one end of the cells in the storage tank (101) is referred to as a low-temperature section (110), and a cell located at the other end of the cells in the storage tank (101) is referred to as a high-temperature section (120). The thermal storage fluid stored in the low-temperature section (110) is formed to have a lower temperature than the thermal storage fluid stored in the remaining cells, and the thermal storage fluid stored in the high-temperature section (120) is formed to have a higher temperature than the thermal storage fluid stored in the remaining cells, and a temperature gradient can be formed in the thermal storage fluid in the storage tank (101) so that the temperature of the thermal storage fluid stored in each cell gradually increases as it goes from the low-temperature section (110) to the high-temperature section (120).

[0015] In addition, the thermal energy storage device (100) may be provided with a low-temperature discharge pipe (111) connected to the low-temperature pump (115) in the low-temperature section (110) to discharge low-temperature heat storage fluid within the low-temperature section (110) to the outside, and a low-temperature inlet pipe (112) connected to a lower portion that is relatively lower in the low-temperature section (110) to receive low-temperature heat storage fluid from the outside, and a high-temperature discharge pipe (121) connected to the high-temperature pump (125) to discharge high-temperature heat storage fluid within the high-temperature section (120) to the outside, and a high-temperature inlet pipe (122) connected to a higher-temperature upper portion that is relatively higher in the high-temperature section (120) to receive high-temperature heat storage fluid from the outside.

[0016] In addition, the thermal energy storage device (100) may be formed such that the cell connecting pipe (155) connecting a pair of adjacent cells includes an upper circulation port (151) communicating with a relatively higher temperature upper portion within one cell on the low-temperature section (120) or the low-temperature section (110) side and a lower circulation port (151) communicating with a relatively lower temperature lower portion within the other cell on the high-temperature section (120) or the high-temperature section (120) side, and a heat storage fluid that is relatively high temperature when compared between the upper and lower portions among the heat storage fluids within one cell that are relatively low temperature when compared between the one cell and the other cell, and a heat storage fluid that is relatively low temperature when compared between the upper and lower portions among the heat storage fluids within the other cell that are relatively high temperature when compared between the one cell and the other cell, may be directly connected to each other, thereby minimizing the temperature difference between the heat storage fluids transported by passing through the cells. Additionally, the cell connection pipe (155) may be equipped with a flow controller (153) that controls the flow rate of the heat storage fluid passing through the cell connection pipe (155).

[0017] The above thermal energy storage device (100) can operate so that, in energy storage mode, high-temperature heat storage fluid heated by an external heating source flows into the high-temperature section (120) at the other end through the high-temperature inlet pipe (122), and as the heat storage fluid in the high-temperature section (120) is transferred from the other side to one side of the storage tank (101) through at least one cell connection pipe (155), a temperature gradient is formed so that the temperature of the cells changes from high to low as they go from the other side to one side, and the low-temperature heat storage fluid, whose temperature has decreased while being transferred, is transferred to an external heating source through the low-temperature section pump (115) provided in the low-temperature section (110) at the one end and heated again by the external heating source, thereby forming a circulation.

[0018] The above thermal energy storage device (100) can operate in an energy recovery mode such that, when a low-temperature heat storage fluid cooled from an external cooling source flows into the low-temperature section (110) at one end through the low-temperature inlet pipe (112), and as the heat storage fluid in the low-temperature section (110) is transferred from one side to the other side of the storage tank (101) through at least one cell connection pipe (155), a temperature gradient is formed so that the temperatures of the cells change from low to high as they go from one side to the other side, and the high-temperature heat storage fluid, whose temperature increases as it is transferred, is transferred to the external cooling source through the high-temperature section pump (125) provided in the high-temperature section (120) at the other end and is cooled again by the external cooling source, thereby forming a circulation.

[0019] In addition, the thermal energy storage device (100) may further include a unit (150) formed as at least one cell disposed between the low-temperature section (110) and the high-temperature section (120).

[0020] At this time, the thermal energy storage device (100) may include a plurality of unit parts (150), and at least one unit part (150) selected from the plurality of unit parts (150) forms a medium-temperature part (130), and the medium-temperature part (130) may be provided with a medium-temperature part pump (135), a medium-temperature discharge pipe (131) connected to the medium-temperature part pump (135) to discharge heat storage fluid within the medium-temperature part (130) to the outside, and a medium-temperature inlet pipe (132) connected to the inside of the medium-temperature part (130) to receive heat storage fluid from the outside.

[0021] In addition, when the thermal energy storage device (100) is a connection of a plurality of cells in which a temperature gradient is formed from low temperature to high temperature from one side to the other, a plurality of unit rows are stacked and connected in parallel so that a temperature gradient is formed from low temperature to high temperature from one side to the other throughout the stack, or a plurality of unit rows are stacked and connected in series so that a temperature gradient is formed from low temperature to high temperature sequentially following the unit rows.

[0022] At this time, the thermal energy storage device (100) is formed so that the temperature gradient direction within the unit column and the stacking arrangement direction of the unit columns are perpendicular to each other, and the temperature gradient direction is the horizontal direction, the stacking arrangement direction is the vertical direction, and the gravity direction is the height direction, so that the stacked body of the unit columns forms a rectangular parallelepiped, or the temperature gradient direction is the tangential direction, the stacking arrangement direction is the radial direction, and the gravity direction is the height direction, so that the stacked body of the unit columns forms a cylindrical shape.

[0023] In addition, the above thermal energy storage device (100) can be formed so that a thermal storage fluid can be circulated between the boundary surfaces between the unit columns.

[0024] Additionally, the thermal energy storage device (100) may further include a heat recovery pipe (140) formed in the form of a pipe that sequentially passes through the cells in the storage tank (101) from the low-temperature section (110) to the high-temperature section (120), and through which a heat recovery fluid is circulated inside.

[0025] In addition, the thermal energy storage device (100) may further include a bubble injection pipe (160) that introduces bubbling fluid into the lower part of the cells in the storage tank (101).

[0026] According to the present invention, there is a great effect in that high-temperature energy can be stored in a single tank in which the water level is maintained constant.

[0027] In addition, the number of tanks is minimized to a single tank, which in turn minimizes pumps, electrical equipment, and piping, resulting in an economic effect of minimizing initial investment and operating costs.

[0028] In addition, because the water level is constant, the water pressure applied to the storage tank is constant, and accordingly, there is no repetitive load due to changes in the water level, so the risk of structural fatigue destruction due to repetitive load is eliminated, which has the effect of increasing the structural safety of the tank.

[0029] Additionally, since the pumps installed in the storage tank are always guaranteed a stable water level, it is effective in preventing pump damage or instability in pump operation due to a drop in water level.

[0030] In addition, according to the present invention, not only is the device itself simple in structure, thereby improving ease of manufacture and economy, but it also has the effect of enabling simple large-capacity production by utilizing the module concept.

[0031] Figure 1 is a conceptual diagram of a conventional two-tank molten salt thermal energy storage system.

[0032] Figure 2 is a conceptual diagram of a thermal energy storage device having a temperature gradient of the present invention and its connection to the outside.

[0033] Figure 3 is a thermal energy storage device having a temperature gradient of the present invention.

[0034] Figure 4 is an embodiment having multiple cells.

[0035] Figure 5 is energy storage mode.

[0036] Figure 6 is the energy recovery mode.

[0037] Figure 7 shows the detailed configuration of the cell connector.

[0038] Figure 8 shows the inflow and outflow of heat storage medium in the medium temperature region.

[0039] Figure 9 shows large capacity using parallel configuration - parallel configuration 1 (arrow indicates energy release mode).

[0040] Figure 10 shows large capacity using parallel configuration - parallel configuration 2 (arrow indicates energy release mode).

[0041] Figure 11 shows a large capacity using a square serial configuration - a square serial configuration (arrow indicates energy release mode).

[0042] Figure 12 shows a large capacity using a circular serial configuration - a circular serial configuration (arrow indicates energy release mode).

[0043] Fig. 13 is an example of heat recovery using a pipe.

[0044]

[0045] **Explanation of symbols**

[0046] 100: Thermal energy storage device

[0047] 101: Storage tank 105: Cell separator

[0048] 110: Low temperature section 115: Low temperature section pump

[0049] 111: Low-temperature discharge pipe 112: Low-temperature inlet pipe

[0050] 120: High temperature section 125: High temperature section pump

[0051] 121: High temperature discharge pipe 122: High temperature inlet pipe

[0052] 130: Medium temperature section 135: Medium temperature section pump

[0053] 131: Medium temperature discharge pipe 132: Medium temperature inlet pipe

[0054] 140: Heat recovery pipe 141: Heat recovery inlet

[0055] 142: Heat recovery outlet 143: Heat recovery bypass

[0056] 150: Unit part 155: Cell connector

[0057] 151: Upper distribution port 152: Lower distribution port

[0058] 153: Flow regulator 160: Bubble injection tube

[0059] Hereinafter, a thermal energy storage device having a temperature gradient according to the present invention having the configuration described above will be described in detail with reference to the attached drawings.

[0060] Figure 2 illustrates a conceptual diagram of a thermal energy storage device with a temperature gradient of the present invention and its connection to the outside. Referring back to Figure 1, conventional two-tank thermal energy storage devices necessarily require two tanks: a high-temperature tank and a low-temperature tank. However, the thermal energy storage device of the present invention uses only a single storage tank, and instead, the interior of the storage tank is divided into multiple cells, and the temperature of the thermal storage fluid stored in each of the multiple cells is structured so that it gradually gradients from low to high temperature. At this time, since the temperature difference between closely spaced cells is not that large, the energy loss due to heat transfer is not significantly large. However, by sufficiently increasing the number of cells and increasing the distance between the low-temperature and high-temperature sections, the desired temperature difference between the low-temperature and high-temperature sections can be stably maintained. In this way, the thermal energy storage device of the present invention can stably store and operate a thermal storage fluid ranging from high to low temperature in a single tank by having a temperature gradient. Accordingly, as explicitly shown in Fig. 2, by reducing the number of tanks themselves, restrictions on installation space, etc. can be greatly alleviated, and various problems that occurred due to the need for two tanks in the past can be fundamentally resolved.

[0061] FIG. 3 illustrates the simplest configuration of a thermal energy storage device having a temperature gradient of the present invention. The thermal energy storage device (100) having a temperature gradient of the present invention may include: a storage tank (101) in which a thermal storage fluid is accommodated; a cell separator (105) that separates the storage tank (101) into a plurality of cells; a cell connecting pipe (155) that connects the upper part of one cell and the lower part of the other cell among a pair of adjacent cells; a low-temperature pump (115) provided in a cell located at one end of the cells in the storage tank (101) to transport a low-temperature thermal storage fluid; and a high-temperature pump (125) provided in a cell located at the other end of the cells in the storage tank (101) to transport a high-temperature thermal storage fluid. Fig. 4 illustrates an embodiment having multiple cells. By installing multiple cell separators (105) in this way, the storage tank can be divided into multiple cells, and accordingly, the temperature gradient can be made more gradual.

[0062] More specifically, the thermal energy storage device (100) of the present invention is provided with at least one cell separator (105) in the storage tank (101), thereby forming at least two cells, i.e., spaces isolated from each other. The storage tank (101) itself is sealed and insulated from the outside, so that heat exchange with the outside is minimized. The thermal storage fluid stored in each cell is blocked from heat exchange with each other to some extent by the cell separator (105) (of course, strictly speaking, some heat transfer may occur through conduction through the cell separator (105), but) so that the thermal storage fluid having a temperature difference can be stably stored in each cell. However, if the thermal storage fluid is only stored in each cell, energy cannot be stored or recovered, so the thermal storage fluid must be able to be transferred between cells. At this time, by means of the various configurations of the present invention to be described below, the internal temperature conditions of each cell can be maintained stably, while overall, energy storage or recovery operations can be smoothly performed.

[0063] First, among the cells in the storage tank (101), the cell located at one end is referred to as a low-temperature section (110), and among the cells in the storage tank (101), the cell located at the other end is referred to as a high-temperature section (120). Fig. 3 illustrates a case where the thermal energy storage device (100) is composed of only two cells, the low-temperature section (110) and the high-temperature section (120), and Fig. 4 illustrates a case where the device is composed of more cells. In a case like Fig. 4, the cell located between the low-temperature section (110) and the high-temperature section (120) is referred to as a unit section (150).

[0064] As described above, a heat storage fluid having a temperature difference can be stably stored between each cell separated by the cell separator (105). In the present invention, the heat storage fluid stored in the low-temperature section (110) is formed to have a lower temperature than the heat storage fluid stored in the remaining other cells, and the heat storage fluid stored in the high-temperature section (120) is formed to have a higher temperature than the heat storage fluid stored in the remaining other cells. If there are only two cells in the storage tank (101) as in Fig. 3, one of the two cells will become the low-temperature section (110), and the other cell will become the high-temperature section (120). Or, if there are two or more cells in the storage tank (101) as in Fig. 4, the cell at one end becomes the low-temperature section (110), the cell at the other end becomes the high-temperature section (120), and a temperature gradient can be formed in the heat storage fluid in the storage tank (101) so that the temperature of the heat storage fluid stored in each cell gradually increases as it goes from the low-temperature section (110) to the high-temperature section (120).

[0065] The low-temperature section (110) and the high-temperature section (120) are each provided with the low-temperature section pump (115) and the high-temperature section pump (125), respectively, and are formed to be able to discharge low-temperature or high-temperature heat storage fluid when necessary. More specifically, first, the low-temperature section (110) is provided with a low-temperature discharge pipe (111) that is connected to the low-temperature section pump (115) and discharges the low-temperature heat storage fluid within the low-temperature section (110) to the outside, and a low-temperature inlet pipe (112) that is connected to a lower portion that is relatively lower in the low-temperature section (110) and receives the low-temperature heat storage fluid from the outside. In addition, the high temperature section (120) is provided with a high temperature discharge pipe (121) that is connected to the high temperature section pump (125) and discharges the high temperature heat storage fluid within the high temperature section (120) to the outside, and a high temperature inlet pipe (122) that is connected to a relatively higher temperature upper portion within the high temperature section (120) and receives the high temperature heat storage fluid from the outside.

[0066] As described above, the low-temperature section (110), the high-temperature section (120), or the unit section (150) therebetween are separated from each other by the cell separator (105), and the cell separator (105) is also provided with the cell connection pipe (155) so that the heat storage fluid can move between the cells. However, the cell connection pipe (155) has the following configuration. The cell connection pipe (155) that connects a pair of neighboring cells to each other includes an upper circulation port (151) that communicates with a relatively higher temperature upper portion within one cell on the low-temperature section (120) or the low-temperature section (110) side, and a lower circulation port (151) that communicates with a relatively lower temperature lower portion within the other cell on the high-temperature section (120) or the high-temperature section (120) side. Accordingly, by means of the cell connecting pipe (155), among the heat storage fluids in one cell that are relatively low in temperature when compared between one cell and the other cell, the heat storage fluids that are relatively high in temperature when compared between the upper and lower parts, and among the heat storage fluids in the other cell that are relatively high in temperature when compared between one cell and the other cell, the heat storage fluids that are relatively low in temperature when compared between the upper and lower parts can be directly connected to each other. That is, the cell connecting pipe (155) has a structure that allows the fluids with the smallest temperature difference among the heat storage fluids in neighboring cells to directly meet each other. As a result, by forming it so as to minimize the temperature difference between the heat storage fluids transported through and between the cells, even if the heat storage fluids are transported between the cells, the temperature of the heat storage fluids stored in each cell can be maintained quite stably.

[0067] Below, the operation process of the thermal energy storage device (100) is described in more detail.

[0068] FIG. 5 illustrates an energy storage mode. The thermal energy storage device (100) having the temperature gradient, in the energy storage mode, can send a low-temperature thermal storage fluid to an external heating source, receive a high-temperature thermal storage fluid, and store the thermal storage fluid in the storage tank (101) while internally moving the thermal storage fluid through the cells and cell connecting pipes (155). To explain in more detail, in the energy storage mode, first, the high-temperature thermal storage fluid heated by the external heating source is introduced into the high-temperature section (120) at the other end through the high-temperature inlet pipe (122). Next, as the thermal storage fluid in the high-temperature section (120) is transferred from the other side to one side of the storage tank (101) through at least one cell connecting pipe (155), a temperature gradient is formed so that the temperatures of the cells change from high to low as they move from the other side to one side. Next, the low-temperature heat storage fluid, which has been transported and has its temperature lowered, is transferred to an external heating source through the low-temperature pump (115) provided in the low-temperature section (110) at one end, and is heated again by the external heating source, thereby forming a circulation.

[0069] Fig. 6 illustrates an energy recovery mode. The thermal energy storage device (100) having the temperature gradient, in the energy recovery mode, can send a high-temperature heat storage fluid to an external cooling source, receive a low-temperature heat storage fluid, and store the heat storage fluid in the storage tank (101) while internally moving the heat storage fluid through the cells and cell connection pipes (155). To explain in more detail, in the energy recovery mode, first, the low-temperature heat storage fluid cooled by the external cooling source is introduced into the low-temperature section (110) at one end through the low-temperature inlet pipe (112). Next, as the heat storage fluid in the low-temperature section (110) is transferred from one side of the storage tank (101) to the other side through at least one cell connection pipe (155), a temperature gradient is formed so that the temperatures of the cells change from low to high as they move from one side to the other. Next, the high temperature heat storage fluid, which has been transported and has a high temperature, is transferred to an external cooling source through the high temperature pump (125) provided in the high temperature section (120) at the other end, and is cooled again by the external cooling source, thereby completing circulation.

[0070] Fig. 7 illustrates a detailed configuration of a cell connecting pipe. The cell connecting pipe (155) may be in the form of a pipe having a circular cross-section as illustrated in the left drawing of Fig. 7, or may be in the form of a duct having a rectangular cross-section as illustrated in the right drawing of Fig. 7. In this case, it is preferable that the cell connecting pipe (155) be provided with a flow controller (153) that controls the flow rate of the heat storage fluid passing through the cell connecting pipe (155). If the flow rate inside the cell connecting pipe (155) is too low, mixing due to density difference inside the cell connecting pipe (155) may become large. To prevent this, the flow rate must be maintained above an appropriate speed. The flow controller (153) is provided for this purpose, and the flow controller (153) controls the flow rate by controlling the passage area of ​​the heat storage fluid. The above flow regulator (153) can be a valve if the cell connection pipe (155) is a pipe, or a damper if it is a duct.

[0071] Fig. 8 illustrates an embodiment in which a heat storage medium is introduced and introduced into a medium-temperature section. As described above, the thermal energy storage device (100) of the present invention may include a plurality of unit sections (150). At this time, at least one unit section (150) selected from the plurality of unit sections (150) may form a medium-temperature section (130). While the other unit sections (150) merely serve to store the heat storage fluid in an intermediate stage in which the heat storage fluid is transferred between one side and the other side, the medium-temperature section (130) may further introduce and introduce a heat storage fluid (such as molten salt) in the intermediate stage. More specifically, the intermediate temperature section (130) may be equipped with an intermediate temperature section pump (135), an intermediate temperature discharge pipe (131) connected to the intermediate temperature section pump (135) to discharge heat storage fluid within the intermediate temperature section (130) to the outside, and an intermediate temperature inlet pipe (132) connected to the inside of the intermediate temperature section (130) to receive heat storage fluid from the outside.

[0072] That is, the intermediate temperature section (130) has a similar shape to the low temperature section (110) or the high temperature section (120), and is formed so as to be able to introduce or discharge heat storage fluid at an appropriate intermediate temperature between the low temperature and the high temperature as needed. By introducing or introducing the intermediate temperature heat storage fluid in the middle in this way, it is possible to realize operations such as further expanding the system operation by connecting it to a separate external heating source or external cooling source, or improving the overall system performance by appropriately raising or lowering the temperature during the energy storage or recovery process.

[0073] The thermal energy storage device of the present invention, which has a temperature gradient, can be expanded in various ways. In the thermal energy storage device (100), a plurality of cells connected together to form a temperature gradient from low to high temperature from one side to the other are called a unit cell. Various capacities can be expanded depending on how these unit cells are stacked and arranged.

[0074] Figure 9 illustrates an embodiment of parallel configuration 1. In Figure 9, multiple unit rows are stacked and connected in parallel, thereby forming a temperature gradient from low temperature to high temperature from one side to the other throughout the stack. In other words, the unit rows are configured in parallel to increase the capacity. In this case, since the water head pressures of adjacent tanks are the same, the wall thickness of the intermediate tanks can be reduced. The arrows in Figure 9 indicate the fluid flow for the energy release mode.

[0075] Fig. 10 illustrates an embodiment of parallel configuration 2. Parallel configuration 2 changes the structure of parallel configuration 1 so that fluid can easily flow between adjacent unit rows. That is, the heat storage fluid is formed to be able to flow between the boundaries between unit rows. By doing so, the number of pumps and outlets can be reduced. The part indicated by the arrow in Fig. 10 is the boundary through which the fluid can pass, and an example of the structure of this boundary plate is shown at the end of the arrow. Meanwhile, the arrow in Fig. 10 also indicates the fluid flow for the energy release mode.

[0076] Figures 11 and 12 illustrate examples of large capacity using a series configuration. That is, multiple unit columns are stacked and connected in a series-connected manner, so that a temperature gradient is formed from low temperature to high temperature sequentially following the unit columns. Meanwhile, the temperature gradient direction within the unit column and the stacking direction of the unit columns are formed perpendicular to each other in both the parallel configuration and the series configuration. However, in the parallel configuration of Figures 9 and 10 or the series configuration of Figure 11, the temperature gradient direction is horizontal, the stacking direction is vertical, and the gravity direction is height, so that the stack of unit columns forms a rectangular parallelepiped. Meanwhile, in the series configuration of Figure 12, the temperature gradient direction is tangential, the stacking direction is radial, and the gravity direction is height, so that the stack of unit columns forms a cylindrical shape. The arrows in Figures 11 and 12 also indicate the fluid flow for the energy release mode.

[0077] Fig. 13 illustrates an embodiment of heat recovery using a pipe, and in this case, a heat recovery pipe (140) may be additionally provided. The heat recovery pipe is formed to recover heat in place of an external cooling source, and is formed in the form of a pipe that sequentially passes through the cells in the storage tank (101) from the low-temperature section (110) to the high-temperature section (120), so that a heat recovery fluid is circulated therein. As illustrated, a heat recovery inlet (141) is formed on the low-temperature section (110) side, and a heat recovery outlet (142) is formed on the high-temperature section (120) side, so that the heat recovery fluid can be introduced and discharged. In addition, a heat recovery bypass (143) is formed in the middle, so that a medium-temperature heat recovery fluid can be bypassed in the middle, if necessary. Various media can be used as the heat recovery fluid, and water and steam are generally widely used.

[0078] In addition, at this time, a bubble injection pipe (160) for introducing bubbling fluid into the lower part of the cells in the storage tank (101) may be further provided. The bubbling gas injected into the bubble injection pipe (160) can force a vigorous flow while passing through the heat storage fluid, thereby increasing the heat transfer rate to the heat recovery fluid.

[0079] The present invention is not limited to the above-described embodiments, and the scope of application is diverse. It goes without saying that anyone with ordinary skill in the art can make various modifications without departing from the gist of the present invention as claimed in the claims.

[0080] According to the present invention, high-temperature energy can be stored in a single tank with a constant water level, thereby minimizing the number of tanks, and thus minimizing pumps, electric equipment, piping, etc., thereby minimizing initial investment costs and operating costs, resulting in an economic effect.

Claims

1. A storage tank (101) containing a heat storage fluid; A cell separator (105) that separates the above storage tank (101) into multiple cells; A cell connector (155) connecting the upper part of one cell and the lower part of the other cell among a pair of neighboring cells; A low-temperature pump (115) provided in a cell located at one end of the cells in the above storage tank (101) to transport low-temperature heat storage fluid; A high temperature pump (125) provided in a cell located at the other end of the cells in the above storage tank (101) to transport high temperature heat storage fluid; A thermal energy storage device characterized by including:

2. In the first paragraph, the thermal energy storage device (100) Among the cells in the above storage tank (101), the cell located at one end is called a low-temperature section (110), and among the cells in the above storage tank (101), the cell located at the other end is called a high-temperature section (120). The heat storage fluid stored in the low-temperature section (110) is formed at a lower temperature than the heat storage fluid stored in the remaining other cells, and the heat storage fluid stored in the high-temperature section (120) is formed at a higher temperature than the heat storage fluid stored in the remaining other cells. A thermal energy storage device characterized in that a temperature gradient is formed in the thermal storage fluid in the storage tank (101) so that the temperature of the thermal storage fluid stored in each cell gradually increases as it moves from the low-temperature section (110) to the high-temperature section (120).

3. In the second paragraph, the thermal energy storage device (100) In the above low-temperature section (110), a low-temperature discharge pipe (111) is provided that is connected to the low-temperature section pump (115) and discharges the low-temperature heat storage fluid in the low-temperature section (110) to the outside, and a low-temperature inlet pipe (112) that is connected to a lower part that is relatively lower in the low-temperature section (110) and receives the low-temperature heat storage fluid from the outside. A thermal energy storage device characterized in that the high temperature section (120) is provided with a high temperature discharge pipe (121) that is connected to the high temperature section pump (125) and discharges the high temperature heat storage fluid within the high temperature section (120) to the outside, and a high temperature inlet pipe (122) that is connected to a relatively higher temperature upper portion within the high temperature section (120) and receives the high temperature heat storage fluid from the outside.

4. In the third paragraph, the thermal energy storage device (100) The cell connecting pipe (155) that connects a pair of neighboring cells to each other, It includes an upper circulation port (151) that communicates with a relatively higher temperature upper portion within one cell on the side of the low-temperature section (120) or the low-temperature section (110), and a lower circulation port (151) that communicates with a relatively lower temperature lower portion within the other cell on the side of the high-temperature section (120) or the high-temperature section (120). By allowing the heat storage fluid in one cell, which is relatively low temperature when comparing between one cell and the other cell, to be directly connected to the heat storage fluid in the other cell, which is relatively high temperature when comparing between the upper and lower portions, and the heat storage fluid in the other cell, which is relatively high temperature when comparing between one cell and the other cell, to be directly connected to the heat storage fluid in the upper and lower portions, A thermal energy storage device characterized in that it is formed to minimize the temperature difference between the thermal storage fluids transported through the cells.

5. In the fourth paragraph, the cell connection tube (155) A thermal energy storage device characterized by having a flow controller (153) that controls the flow rate of the thermal storage fluid passing through the cell connection pipe (155).

6. In the fourth paragraph, the thermal energy storage device (100) In energy storage mode, A high temperature heat storage fluid heated from an external heating source is introduced into the high temperature section (120) at the other end through the high temperature inlet pipe (122), As the heat storage fluid in the high temperature section (120) is transferred from the other side to one side of the storage tank (101) through at least one cell connection pipe (155), a temperature gradient is formed so that the temperature of the cells changes from high temperature to low temperature from the other side to one side. A thermal energy storage device characterized in that the low-temperature heat storage fluid, which has been lowered in temperature while being transported, is transferred to an external heating source through the low-temperature pump (115) provided in the low-temperature section (110) at one end and is heated again by the external heating source, thereby forming a circulation.

7. In the fourth paragraph, the thermal energy storage device (100) In energy recovery mode, A low-temperature heat storage fluid cooled from an external cooling source is introduced into the low-temperature section (110) at one end through the low-temperature inlet pipe (112), As the heat storage fluid in the low temperature section (110) is transferred from one side of the storage tank (101) to the other side through at least one cell connection pipe (155), a temperature gradient is formed so that the temperature of the cells changes from low temperature to high temperature from one side to the other. A thermal energy storage device characterized in that the high temperature heat storage fluid, which has increased in temperature while being transported, is transferred to an external cooling source through the high temperature pump (125) provided in the high temperature section (120) at the other end and is cooled again by the external cooling source, thereby forming a circulation.

8. In the fourth paragraph, the thermal energy storage device (100) A unit (150) formed as at least one cell disposed between the low-temperature section (110) and the high-temperature section (120); A thermal energy storage device characterized by further including:

9. In the 8th paragraph, the thermal energy storage device (100) It comprises a plurality of the above unit parts (150), and at least one of the above unit parts (150) selected from the plurality of the above unit parts (150) forms a medium temperature part (130), A thermal energy storage device characterized in that the above-mentioned medium-temperature section (130) is provided with a medium-temperature section pump (135), a medium-temperature discharge pipe (131) connected to the medium-temperature section pump (135) to discharge heat storage fluid within the medium-temperature section (130) to the outside, and a medium-temperature inlet pipe (132) connected to the inside of the medium-temperature section (130) to receive heat storage fluid from the outside.

10. In the fourth paragraph, the thermal energy storage device (100) When a connection of multiple cells that form a temperature gradient from low temperature to high temperature from one side to the other is called a unit cell, A temperature gradient is formed from low temperature to high temperature from one side to the other as multiple unit columns are stacked and connected in a parallel manner, or A thermal energy storage device characterized in that a temperature gradient is formed by sequentially following the unit columns by forming a plurality of unit columns in a stacked and serially connected form, thereby changing from low temperature to high temperature.

11. In the 10th paragraph, the thermal energy storage device (100) The temperature gradient direction within the unit column and the stacking direction of the unit columns are formed perpendicular to each other, Since the temperature gradient direction is horizontal, the stacking direction is vertical, and the gravity direction is height, the stack of unit columns forms a rectangular parallelepiped, or A thermal energy storage device characterized in that the temperature gradient direction is in the tangential direction, the stacking direction is in the radial direction, and the gravity direction is in the height direction, so that the stack of unit columns forms a cylindrical shape.

12. In the 10th paragraph, the thermal energy storage device (100) A thermal energy storage device characterized in that a thermal storage fluid is formed to be circulated between the boundaries between unit columns.

13. In the fourth paragraph, the thermal energy storage device (100) A heat recovery pipe (140) formed in the form of a pipe that sequentially passes through the cells in the storage tank (101) from the low-temperature section (110) to the high-temperature section (120), and through which heat recovery fluid is circulated inside; A thermal energy storage device characterized by further including:

14. In the fourth paragraph, the thermal energy storage device (100) A bubble injection pipe (160) that introduces bubbling fluid into the lower part of the cells in the above storage tank (101); A thermal energy storage device characterized by further including:

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