Power-storage temperature system, power-storage temperature system for energy storage system, and method for adjusting temperature of power storage unit

Abstract

A power-storage temperature system (1) comprises: a plurality of power storage units (2A)-(2C) that are electrically connected in parallel; and a circulation system (3) that circulates a circulating fluid, which is for adjusting the temperatures of the plurality of power storage units (2A)-(2C), through a plurality of flow path members (6A)-(6C) that are connected to the power storage units (2A)-(2C). According to differences in the internal states of the power storage units (2A)-(2C), the temperatures of the power storage units (2A)-(2C) are individually adjusted or adjusted to different temperatures by the temperature adjustment capacity of the circulating fluid flowing through the flow path members (6A)-(6C).

Description

Battery Temperature System, Battery Temperature System for Energy Storage System, and Temperature Adjustment Method for Battery Unit

[0001] The present invention relates to a technology for adjusting the temperature of a battery unit.

[0002] In recent years, the demand for energy storage systems (ESS, also referred to as power storage stations) has been increasing. An ESS includes a battery bank in which a plurality of cells are connected in series. A large-capacity ESS is configured by connecting a plurality of battery banks (an example of a battery unit) in parallel.

[0003] An ESS is operated over a long period (for example, 20 years). Along with the operation, the deterioration of cells progresses, and it is known that particularly high-temperature cells deteriorate rapidly. Patent Document 1 discloses a technology for controlling the temperature of a battery unit.

[0004] Japanese Patent Application Laid-Open No. 2020-140955

[0005] The battery units may have different temperatures suitable for maintaining performance due to differences in the internal states of the cells such as SOH (State Of Health) and internal resistance. If the deterioration of some battery units progresses more than that of other battery units, some battery units become bottlenecks, and the performance of the entire energy storage system decreases. This problem is not limited to energy storage systems, and the same problem exists in battery units connected in parallel.

[0006] The battery temperature system includes a plurality of battery units electrically connected in parallel, and a circulation system that circulates a circulating liquid for adjusting the temperature of the plurality of battery units through a plurality of flow path members connected to each of the battery units. According to the temperature adjustment ability of the circulating liquid flowing through the flow path members, each of the battery units is individually temperature-adjusted or adjusted to different temperatures according to the differences in the internal states of each of the battery units.

[0007] =]] The present invention can control the temperature of each battery unit to a temperature suitable for the internal state such as SOH and internal resistance. Therefore, it is possible to suppress the performance degradation of some battery units and maintain the performance of the entire battery unit.

[0008] System configuration diagram of the energy storage temperature unit Plan view of the plate and energy storage unit Diagram of Figure 2 viewed from direction A Correlation table of SOH-temperature System configuration diagram of the energy storage system Block diagram of the CMU Block diagram of the BMU Diagram showing SOH after a predetermined period has elapsed after the start of operation Diagram showing SOH after a predetermined period has elapsed after the start of operation

[0009] (Outline of this Embodiment) An embodiment of the present invention of an energy storage temperature system will be described below. (1) The energy storage temperature system comprises a plurality of energy storage units electrically connected in parallel, and a circulation system that circulates a circulating liquid for adjusting the temperature of the plurality of energy storage units through a plurality of flow path members connected to each of the energy storage units, and adjusts the temperature of each energy storage unit individually or to a different temperature according to the differences in the internal state of each energy storage unit by the temperature adjustment capacity of the circulating liquid flowing through the flow path members. An energy storage unit is a collection of cells connected in series or in series and parallel, and includes an energy storage pack and an energy storage bank. The circulating liquid is a liquid that adjusts the temperature of the energy storage units by exchanging heat with the energy storage units, and includes cooling water and hot water. The temperature adjustment capacity is the cooling capacity by the cooling water and the heating capacity by the hot water.

[0010] According to the energy storage temperature system in (1), each energy storage unit can be controlled to a temperature suitable for maintaining performance based on differences in internal states such as SOH and internal resistance. Therefore, performance degradation in some energy storage units can be suppressed, and the overall performance of the energy storage units can be maintained. This configuration allows the actual capacity between energy storage units to be kept constant without limiting the input / output of the energy storage units, thus reducing the frequency of energy storage unit replacement and improving cost-effectiveness. Furthermore, by controlling the temperature of the energy storage units to minimize differences in internal states, it is expected that the internal states will be made uniform among multiple energy storage units.

[0011] (2) In the energy storage temperature system described in (1) above, the internal state of the energy storage unit may be State of Health (SOH). The lower the SOH of the energy storage unit, the lower the temperature at which the energy storage unit may be controlled. SOH is an indicator of the deterioration state of the energy storage unit.

[0012] According to (2), a storage unit whose state of health (SOH) has deteriorated and become low can be controlled to a lower temperature than other storage units, thereby slowing down the deterioration process compared to other storage units. With this configuration, the SOH can be made uniform among the storage units, so that a decrease in the SOH of some storage units does not become a bottleneck and reduce the overall performance of the system.

[0013] (3) In the energy storage temperature system described in (1) or (2) above, the circulation system may have a plurality of flow adjusters provided for each of the plurality of flow path members. The plurality of flow adjusters may each adjust the flow rate of the circulating fluid flowing through the plurality of flow path members. The flow adjusters include all devices capable of adjusting the flow rate of the circulating fluid, such as electromagnetic valves.

[0014] According to (3), the temperature of each energy storage unit can be adjusted by adjusting the flow rate of the circulating fluid using a flow rate adjuster.

[0015] This technology can be applied to energy storage temperature systems and temperature control methods for energy storage units in Energy Storage Systems (ESS). ESS requires the installation of many energy storage units in a limited space (in other words, to improve energy density). Therefore, heat buildup is likely to occur depending on the installation location, and some energy storage units tend to overheat. Furthermore, ESS energy storage temperature systems are generally expensive and are operated over long periods. By applying this technology and individually controlling the temperature of each energy storage unit, a high cost-effectiveness can be achieved.

[0016] <Embodiment> 1. System Configuration Diagram 1 of the Energy Storage Temperature System 1 is a system configuration diagram of the Energy Storage Temperature System 1. The Energy Storage Temperature System 1 comprises a plurality of energy storage units 2A to 2C (collectively referred to as energy storage units 2) and a circulation system 3. The plurality of energy storage units 2A to 2C are collections of cells 12 connected in series or in series-parallel, and include energy storage packs and energy storage banks. The energy storage units 2A to 2C are equipped with sensors for acquiring the voltage V, current I, and temperature T of the energy storage units.

[0017] The circulation system 3 comprises a temperature control unit 4, circulation piping, a pump 8, a plurality of flow adjusters 9A to 9C, and a control device 10.

[0018] The circulation piping comprises a supply pipe 5, multiple branch pipes 6A to 6C, and a return pipe 7. The multiple branch pipes 6A to 6C branch off from the supply pipe 5 at point X in Figure 1 and merge with the return pipe at point Y in Figure 1. The circulating fluid circulates through the path of the temperature control unit 4, the supply pipe 5, the branch pipes 6A to 6C, and the return pipe 7. The supply pipe 5, the branch pipes 6A to 6C, and the return pipe 7 correspond to the "flow channel members" of the present invention.

[0019] Multiple branch pipes 6A to 6C correspond to multiple energy storage units 2A to 2C, and are connected to the multiple energy storage units 2A to 2C in a manner that allows for heat exchange. In this embodiment, as shown in Figures 2 and 3, the branch pipes 6 are built into the plate 14.

[0020] The plate 14 is a fixing member for the cell 12. The plate 14 is made of metal, and in this example, its top surface is the mounting surface for the cell 12. Each cell 12 of the energy storage unit 2 exchanges heat with the circulating fluid flowing through the branch pipe 6 via its bottom surface to regulate its temperature. An insulating thermal conductive material (e.g., a thermal interface material) may be interposed between the plate 14 and the cell 12. By interposing an insulating thermal conductive material, both insulation and thermal conductivity can be achieved between the plate 14 and the cell 12.

[0021] Multiple flow adjusters 9A to 9C are located in multiple branch pipes 6A to 6C. The flow adjusters 9A to 9C adjust the flow rate of the circulating fluid flowing through the branch pipes 6A to 6C. The flow adjusters 9A to 9C may be electric valves that adjust the flow rate of the circulating fluid by adjusting the opening degree of the valve, or they may be solenoid valves that adjust the flow rate of the circulating fluid by adjusting the duty cycle of the valve opening and closing.

[0022] The temperature control unit 4 includes a tank for storing circulating fluid and a temperature control unit for adjusting the temperature of the circulating fluid. The circulating fluid is a liquid that can adjust the temperature of the energy storage unit 2 by exchanging heat with it, and includes cooling water and hot water.

[0023] The temperature control unit 4 is typically a chiller, and may be a cooling unit that cools the energy storage unit 2 by circulating cooling water, or a heating unit that heats the energy storage unit 2 by circulating hot water. This embodiment describes an example in which the temperature control unit 4 is a cooling unit.

[0024] The control device 10 includes a CPU 15 and a storage unit 16. The storage unit 16 stores a correlation table between the State of Health (SOH) and temperature of the energy storage unit 2 (see Figure 4).

[0025] The control device 10 is connected to each flow adjuster 9A to 9C via signal lines, and by sending commands to each flow adjuster 9A to 9C, it can individually adjust the flow rate of cooling water flowing through each branch pipe 6A to 6C (the cooling capacity of each energy storage unit 2A to 2C). By adjusting the flow rate of the cooling water, the temperature of each energy storage unit 2A to 2C can be individually adjusted.

[0026] The control device 10 is connected to each energy storage unit 2A to 2C via signal lines and acquires information on the voltage V, current I, and temperature T of each energy storage unit 2A to 2C. Based on the information on voltage V, current I, and temperature T, the control device 10 monitors the internal state of each energy storage unit 2A to 2C.

[0027] The internal state of the energy storage unit 2 is represented by, for example, the State of Health (SOH) and State of Charge (SOC). SOH is an indicator of the degradation state (health) of energy storage units 2A to 2C, and SOC is an indicator of the remaining capacity of energy storage units 2A to 2C. SOH can be calculated, for example, by actually measuring the battery capacity. It can also be calculated by methods that estimate capacity degradation based on the temperature environment and the time elapsed since manufacturing. SOC can be calculated, for example, by the current integration method or from the correlation between SOC and OCV.

[0028] SOH = Battery capacity / Initial battery capacity × 100 [%] SOC = Remaining capacity / Battery capacity × 100 [%]

[0029] 2. Temperature Control of Energy Storage Unit 2 The optimal temperature for maintaining the performance of energy storage unit 2 varies depending on the State of Health (SOH). For example, energy storage unit 2 with a low SOH will degrade more easily at the same temperature than energy storage unit 2 with a high SOH. By keeping energy storage unit 2 with a low SOH at a lower temperature than energy storage unit 2 with a high SOH, it is possible to slow down the progression of degradation.

[0030] The control device 10 monitors the State of Health (SOH) of each energy storage unit 2, and controls the temperature of energy storage units 2 with a lower SOH to a lower temperature than energy storage units 2 with a higher SOH.

[0031] In the example shown in Figure 1, the SOH of energy storage unit 2A is 90%, the SOH of energy storage unit 2B is 92%, and the SOH of energy storage unit 2C is 94%. The control device 10 controls the temperature of energy storage unit 2A to 20°C, the temperature of energy storage unit 2B to 23°C, and the temperature of energy storage unit 2C to 26°C by adjusting the flow rate of cooling water flowing through each branch pipe 6A to 6C.

[0032] By adjusting the temperature of energy storage unit 2A, which has a low SOH, to a lower temperature than that of energy storage units 2B and 2C, which have a high SOH, the progression of degradation can be slowed down, and the SOH of all energy storage units 2A, 2B, and 2C can be made uniform.

[0033] Furthermore, the correlation table between SOH and temperature recorded in the memory unit 16 may be a correlation table between the amount of SOH decrease and temperature over a predetermined period (for example, one year).

[0034] <Calculation Example> If there is a 5% difference in SOH between two energy storage units, and you want to reduce this to 0% over 5 years, then for energy storage unit 2 with a higher SOH, you should select a temperature table (temperature) that results in a 2% decrease in SOH, and for energy storage unit 2 with a lower SOH, you should select a temperature table (temperature) that results in a 1% decrease in SOH.

[0035] When adjusting the flow adjusters 9A to 9C to achieve the above temperatures, the adjustment method may be feedback control based on cell temperature measurements, or control by AI that has learned from previous flow adjustment results and cell temperatures.

[0036] 3. Explanation of Effects: According to this technology, it is possible to suppress the performance degradation of some energy storage units 2A to 2C, and maintain the overall performance of the energy storage units.

[0037] <Application Example> An example of applying this technology to an energy storage system S will be described. The energy storage system S is a system that is connected to the power grid G ​​and adjusts the supply and demand of electricity.

[0038] As shown in Figure 5, the energy storage system S comprises a PCS 30 and a power storage device 40. PCS 30 is an abbreviation for Power Conditioning System. The PCS 30 is a device that charges and discharges the power storage device 40 and is installed on the power line L, which is the main circuit.

[0039] The PCS 30 comprises a power conversion unit 31 and a power control unit 33. The power conversion unit 31 is a bidirectional inverter, a bidirectional converter capable of both forward conversion (AC to DC) and reverse conversion (DC to AC). The power control unit 33 controls the power conversion unit 31 and adjusts the supply and demand of power.

[0040] The energy storage system 40 is composed of multiple energy storage banks 50. In this example, it is composed of five energy storage banks 50A to 50E connected in parallel. Energy storage banks 50A to 50E are connected to the PCS 30 via a power line L.

[0041] The energy storage banks 50A to 50E are collections of multiple cells 61 and correspond to the energy storage unit 2. The multiple energy storage banks 50A to 50E may be housed in a single container or other housing, or they may be housed in separate housings such as battery panels.

[0042] Each of the energy storage banks 50A to 50E is connected to branch piping (omitted in Figures 5, 7, and 8) in a manner that allows for heat exchange, and the temperature can be adjusted for each energy storage bank by adjusting the flow rate of the cooling water.

[0043] As shown in Figure 5, the energy storage banks 50A to 50E consist of a current sensor 51, a BMU 55, and multiple energy storage modules 60 connected in series.

[0044] The power storage module 60 is composed of a plurality of cells 61 connected in series and a CMU 65. The plurality of cells 61 are fixed to a frame or a base and unitized. The cell 6 is a rechargeable power storage element, and various cells can be applied, such as non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries.

[0045] As shown in FIG. 6A, the CMU (Cell Management Unit) 65 includes a CPU 66 and a storage unit 67, and monitors the temperature of the power storage module 60 and the cell voltage of each cell 61.

[0046] The BMU (Battery Management Unit) 55 is installed for each of the power storage banks 50A to 50E. As shown in FIG. 6B, the BMU 55 includes a CPU 56 and a storage unit 57, and monitors the states of each of the power storage banks 50A to 50E.

[0047] Specifically, it monitors the current of the power storage banks 50A to 50E based on the measurement results of the current sensor 51. It is also connected to each CMU 65 via a communication line, and acquires information on the temperature of the power storage module 60 and the voltage of each cell 61 from the CMU 65.

[0048] Based on this information, the BMU 55 monitors the SOH of each of the power storage banks 50A to 50H, and notifies the circulation system 3 of the SOH information.

[0049] Based on the SOH information of each of the power storage banks 50A to 50E acquired from each BMU 55, the circulation system 3 adjusts the flow rate of the cooling water flowing through the branch pipes and adjusts the temperature of each of the power storage banks 50A to 50E.

[0050] FIGS. 7 and 8 show the SOH of each of the power storage banks 50A to 50H after a predetermined period has elapsed after the start of operation. FIG. 7 shows the case where the temperature is controlled to be constant regardless of the SOH (when this technology is not applied), and FIG. 8 shows the case where the temperature is adjusted according to the SOH (when this technology is applied).

[0051] When the temperature is controlled to be constant regardless of the State of Health (SOH) (Figure 7: without application of this technology), the SOH of energy bank 50A is 85%, the SOH of energy bank 50B is 92%, the SOH of energy bank 50C is 80%, the SOH of energy bank 50D is 75%, and the SOH of energy bank 50E is 86%. There is variation in the SOH of energy banks 50A to 50E, and energy bank 50D, which has reached its end-of-life (SOH = 75%), needs to be replaced with a new one.

[0052] When the temperature is adjusted according to the State of Health (SOH) (Figure 8: Application of this technology), the SOH of energy bank 50A is 85%, the SOH of energy bank 50B is 87%, the SOH of energy bank 50C is 84%, the SOH of energy bank 50D is 85%, and the SOH of energy bank 50E is 86%. The SOH of energy banks 50A to 50E is uniform and has not reached the end of its product life.

[0053] By adjusting the temperature of energy storage banks 50A to 50H according to the State of Health (SOH) of each storage bank 50A to 50H, the SOH of energy storage banks 50A to 50E can be made uniform, and the replacement frequency of energy storage banks 50A to 50E can be reduced.

[0054] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments are also included in the technical scope of the present invention.

[0055] (1) In the above embodiment, the energy storage temperature system 1 was applied to the energy storage system S, but it may be applied to other uses as long as it is a system having multiple energy storage units that are electrically connected in parallel. For example, it may be applied to power supply systems such as HEVs and EVs.

[0056] (2) In the above embodiment, the energy storage unit 2 was cooled by circulating cooling water through the branch pipes 6A to 6C, but the energy storage unit 2 may also be heated by circulating hot water through the branch pipes 6A to 6C.

[0057] (3) In the above embodiment, the temperature of the energy storage unit 2 was adjusted according to the State of Health (SOH) of the energy storage unit 2, but it may also be adjusted according to the initial internal resistance of the energy storage unit 2. Specifically, an energy storage unit 2 with a high initial internal resistance may be adjusted to a lower temperature than other energy storage units 2 with a low initial internal resistance. SOH and initial internal resistance are examples of the internal state of the energy storage unit 2.

[0058] (4) In the above embodiment, the temperature of the energy storage unit 2 is adjusted to different temperatures according to differences in internal conditions (SOH) by the temperature control capacity of the circulating fluid (cooling water) flowing through the flow channel member (branch pipe, for example). The disclosure of the above embodiment can also be understood as adjusting the temperature of the energy storage unit 2 individually according to differences in internal conditions (SOH) by the temperature control capacity of the circulating fluid (cooling water) flowing through the flow channel member (branch pipe, for example).

[0059] 1. Energy storage temperature system 2A-2C Energy storage unit 3. Circulation system 4. Temperature control unit 6A-6C Branch piping (flow channel component) 8. Pump 9A-9C Flow adjuster 10. Control device

Claims

1. An energy storage temperature system comprising: a plurality of energy storage units electrically connected in parallel; and a circulation system that circulates a circulating liquid for adjusting the temperature of the plurality of energy storage units through a plurality of flow path members connected to each of the energy storage units, wherein the temperature adjustment capacity of the circulating liquid flowing through the flow path members allows for individual temperature adjustment or adjustment to different temperatures of each energy storage unit in accordance with differences in the internal state of each energy storage unit.

2. The energy storage temperature system according to claim 1, wherein the internal state of the energy storage unit is state of heat (SOH), and the lower the SOH of the energy storage unit, the lower the temperature of the energy storage unit.

3. The energy storage temperature system according to claim 1, wherein the circulation system has a plurality of flow adjusters provided for each of the plurality of flow path members, and the plurality of flow adjusters each adjust the flow rate of the circulating fluid flowing through the plurality of flow path members.

4. An energy storage temperature system for an energy storage system according to any one of claims 1 to 3.

5. A method for adjusting the temperature of energy storage units, wherein a circulating liquid is circulated through flow channel members connected to each of the energy storage units, and the temperature of each energy storage unit is individually adjusted or adjusted to a different temperature according to the differences in the internal state of each energy storage unit, based on the temperature adjustment capacity of the circulating liquid flowing through the flow channel members.

Images