Storage battery control method, storage battery control device, and storage battery system

Abstract

In a control performed on a high-temperature-operation-type storage battery that is capable of charging and discharging, the temperature of a storage battery is maintained at a prescribed maintenance temperature higher than the lower-limit value of an operation temperature range for the storage battery by heating the storage battery using a heater attached to a storage battery in a standby state in which discharge from the storage battery is not performed, a first discharge start preparation time that is a timing at which heating performed by the heater is stopped and a second discharge start preparation time that is a timing at which a heat radiation means is operated are set so that the temperature of the storage battery reaches the lower-limit value of the operation temperature range at a timing when a scheduled discharge start time arrives, heating performed by the heater is stopped at the timing when the first discharge start preparation time arrives, and the heat radiation means is operated at the timing when the second discharge start preparation time arrives.

Description

Storage battery control method, storage battery control device, and storage battery system

[0001] The present invention relates to temperature control of a storage battery, and more particularly to temperature control taking into account the discharge start time.

[0002] There are an increasing number of cases where storage batteries connected to the power grid are being used in the electricity market. In Japan, there are three electricity markets: the wholesale electricity market, the capacity market, and the supply-demand balancing market. Energy storage businesses predict the electricity price in each market and bid in that market, or buy and sell electricity through bilateral contracts with power companies.

[0003] For example, in the wholesale electricity market, a day is divided into 30-minute trading units (frames), and electricity is bought and sold for each frame. Energy storage businesses submit bids by specifying the frame to sell and the amount of electricity to sell (discharged electricity) and the frame to buy and the amount of electricity to purchase (charged electricity). They then sell and buy electricity for the frames they win, receiving and paying compensation.

[0004] For each frame, the compensation obtained from selling electricity = market price x power sold, so the more frames (i.e., longer periods) and higher power sold during times when the market price is high, the more revenue can be earned. Therefore, there is a demand for battery control technology that enables high-power discharge during times when the market price is high.

[0005] As a storage battery that can be utilized in the above-described electricity market, a sodium-sulfur battery (NaS battery), which is a high-temperature operating storage battery, is already known (see, for example, Patent Document 1). In general terms, in a NaS battery, a battery assembly formed by connecting a plurality of unit cells in series and parallel is housed in a housing (container) equipped with a heat dissipation device (fan) and a heating device (heater), thereby forming a module battery. The unit cell has a structure in which sulfur, which is a positive electrode active material, and metallic sodium, which is a negative electrode active material, are housed and isolated by, for example, a solid electrolyte tube. A battery unit formed from one or more module batteries is used as a NaS battery for various applications.

[0006] The discharge time of a storage battery tends to become longer as the storage battery is used for multiple purposes, such as buying and selling electricity in multiple markets. Moreover, in the case of an NaS battery such as that disclosed in Patent Document 1, the battery temperature needs to be kept within a predetermined allowable range during operation, but the longer the discharge time, the higher the battery temperature tends to become.

[0007] When the battery temperature reaches the upper limit of the allowable range, discharging must be stopped. Therefore, in order to ensure sufficient discharge time, it is necessary to suppress the rise in battery temperature.

[0008] Patent Document 1 discloses a method in which, when it is determined that the predicted value (predicted temperature) of the temperature of a discharging storage battery (more specifically, the temperature inside its casing) at a certain point in the future is higher than a predetermined specified temperature, the storage battery control device controls the heat dissipation device provided in the casing prior to the arrival of that point in time, thereby increasing the amount of heat dissipation and preventing the battery temperature from exceeding the upper limit of the allowable range.

[0009] By performing such control, the storage battery disclosed in Patent Document 1 prevents the battery temperature from exceeding the upper limit of the allowable range due to the heat of reaction generated by the reaction between sodium and sulfur during discharge. Furthermore, excessive cooling of the inside of the housing by the heat dissipation device is avoided. This makes it possible to shorten or eliminate the heating time by the heater. This leads to a reduction in power consumption during operation of the storage battery and also contributes to improving the system efficiency of the storage battery.

[0010] Patent document 1 also discloses a configuration in which, if it is determined that the predicted value (predicted temperature) of the battery temperature after discharge at a certain point in the future is higher than a predetermined target temperature at the start of the next discharge, the control device controls the heat dissipation device to increase the amount of heat dissipation, thereby preventing the battery temperature from exceeding the target temperature.

[0011] Furthermore, Patent Document 1 also discloses a mode in which a storage battery control device creates a heat dissipation schedule based on a pre-set charge / discharge schedule, which increases the amount of heat dissipation in advance of the period when the temperature of the storage battery increases due to heat generated by charging and discharging the storage battery.

[0012] On the other hand, if the standby state in which the battery temperature is maintained by the heater without discharging is prolonged, i.e., if the discharge interval is long, it is sufficient to maintain the battery temperature near the lower limit of the allowable range (e.g., 305°C to 305.1°C), but to perform such control, it is necessary to repeatedly turn the heater on and off in short cycles (e.g., every 10 seconds). If such heater on / off is performed by a mechanical relay, the life of the relay contacts and coil will be shortened and the relay will need to be replaced more frequently, which is not preferable.

[0013] Furthermore, if the discharge interval is long, heating with a heater while operating the fan increases the power consumed by the heater by the amount of heat dissipated by the fan. In consideration of this, in order to minimize the heater power, the fan may be turned off to minimize the amount of heat dissipation. However, in this case, the temperature inside the housing rises, and discharging begins with heat trapped inside the housing. Therefore, the reaction heat generated during discharging may reduce the effectiveness of the heat dissipation control disclosed in Patent Document 1, which is intended to prevent the battery temperature at some point in the future from exceeding the upper limit of the allowable range.

[0014] Furthermore, Patent Document 1 does not specifically disclose the optimal timing for operating the heat dissipation device to increase the heat dissipation capacity in the heat dissipation control. If the timing for increasing the heat dissipation amount is too early, it becomes necessary to operate the heater to prevent the battery temperature from falling below the lower limit of the allowable range.

[0015] If the timing for increasing the amount of heat dissipation is too late, the battery temperature at the start of discharge will be significantly higher than the lower limit of the allowable range, and the reaction heat generated during discharge will cause the temperature inside the housing to exceed the upper limit of the allowable range.

[0016] International Publication No. 2016 / 136507

[0017] The present invention has been made in view of the above-mentioned problems, and has an object to realize a storage battery control method that can increase the discharge capacity of a storage battery compared to conventional methods.

[0018] In order to solve the above problem, a first aspect of the present invention is a control method for a high-temperature operating storage battery that can be charged and discharged, which, during standby when not discharging from the storage battery, maintains the temperature of the storage battery at a predetermined maintenance temperature that is higher than a lower limit of the operating temperature range of the storage battery by heating the storage battery with a heater associated with the storage battery, sets a first discharge start preparation time that is a timing to stop heating by the heater and a second discharge start preparation time that is a timing to activate a heat dissipation means associated with the storage battery so that the temperature of the storage battery reaches the lower limit of the operating temperature range at a scheduled discharge start time, and stops heating by the heater at the timing when the first discharge start preparation time is reached and activates the heat dissipation means at the timing when the second discharge start preparation time is reached.

[0019] A second aspect of the present invention is a control method for a storage battery according to the first aspect, characterized in that by performing arithmetic processing based on the flow of heat in and out of the storage battery per unit time associated with the operation of the heater and the heat dissipation means, a predicted profile of temperature change from a predetermined initial time to the discharge start time is specified according to the timing of stopping heating by the heater and operating the heat dissipation means, and the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile in which the temperature at the discharge start time is the lower limit value is set to the first and second discharge start preparation times, respectively.

[0020] A third aspect of the present invention is a control method for a storage battery according to the second aspect, characterized in that in the calculation process, the predicted profile is determined by taking into account the contribution of past operations of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

[0021] A fourth aspect of the present invention is a control method for a storage battery according to any one of the first to third aspects, characterized in that the first and second discharge start preparation times are set to the same time.

[0022] A fifth aspect of the present invention is a control method for a storage battery according to any one of the first to third aspects, characterized in that the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

[0023] A sixth aspect of the present invention is the method for controlling a storage battery according to any one of the first to third aspects, characterized in that the operating temperature range is 280°C to 350°C.

[0024] A seventh aspect of the present invention is a method for controlling a storage battery according to any one of the first to third aspects, characterized in that the storage battery includes an assembled battery comprised of a plurality of single cells, each of which is a sodium-sulfur battery, housed in a housing.

[0025] An eighth aspect of the present invention is a control device for a high-temperature operating storage battery that can be charged and discharged, the storage battery comprising a heater for heating the storage battery and heat dissipation means, wherein during standby when no discharge is occurring from the storage battery, the heater heats the storage battery so that the temperature of the storage battery is maintained at a predetermined maintenance temperature that is higher than a lower limit of the operating temperature range of the storage battery, and a first discharge start preparation time that is a timing for stopping heating by the heater and a second discharge start preparation time that is a timing for activating the heat dissipation means are set so that the temperature of the storage battery reaches the lower limit of the operating temperature range at a scheduled discharge start time, and heating by the heater is stopped at the timing when the first discharge start preparation time is reached and the heat dissipation means is activated at the timing when the second discharge start preparation time is reached.

[0026] A ninth aspect of the present invention is a storage battery control device according to the eighth aspect, characterized in that by performing arithmetic processing based on the flow of heat in and out of the storage battery per unit time associated with the operation of the heater and the heat dissipation means, a predicted profile of temperature change from a predetermined initial time to the discharge start time is determined according to the timing of stopping heating by the heater and operating the heat dissipation means, and the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile at which the temperature at the discharge start time is the lower limit value is set to the first and second discharge start preparation times, respectively.

[0027] A tenth aspect of the present invention is a storage battery control device according to the ninth aspect, characterized in that in the calculation process, the predicted profile is determined by taking into account the contribution of past operations of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

[0028] An eleventh aspect of the present invention is a storage battery control device according to any one of the eighth to tenth aspects, characterized in that the first and second discharge start preparation times are set to the same time.

[0029] A twelfth aspect of the present invention is a control device for a storage battery according to any one of the eighth to tenth aspects, characterized in that the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

[0030] A thirteenth aspect of the present invention is the storage battery control device according to any one of the eighth to tenth aspects, characterized in that the operating temperature range is 280°C to 350°C.

[0031] A fourteenth aspect of the present invention is a storage battery control device according to any one of the eighth to tenth aspects, characterized in that the storage battery comprises a battery assembly consisting of a plurality of single cells, each of which is a sodium-sulfur battery, and a housing that houses the battery assembly.

[0032] A fifteenth aspect of the present invention is a storage battery system comprising a high-temperature operating storage battery capable of being charged and discharged, and a control device for the storage battery, wherein the storage battery comprises a heater for heating the storage battery and heat dissipation means, and the control device causes the heater to heat the storage battery during standby when no discharge is occurring from the storage battery, thereby maintaining the temperature of the storage battery at a predetermined maintenance temperature higher than a lower limit of the operating temperature range of the storage battery, sets a first discharge start preparation time which is a timing for stopping heating by the heater and a second discharge start preparation time which is a timing for activating the heat dissipation means so that the temperature of the storage battery reaches the lower limit of the operating temperature range at a timing when a scheduled discharge start time arrives, and stops heating by the heater when the first discharge start preparation time arrives and activates the heat dissipation means when the second discharge start preparation time arrives.

[0033] A sixteenth aspect of the present invention is a storage battery system according to the fifteenth aspect, characterized in that the control device performs arithmetic processing based on the flow of heat in and out of the storage battery per unit time associated with the operation of the heater and the heat dissipation means, thereby specifying a predicted profile of temperature change from a predetermined initial time to the discharge start time according to the timing of stopping heating by the heater and operating the heat dissipation means, and sets the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile in which the temperature at the discharge start time is the lower limit value to the first and second discharge start preparation times, respectively.

[0034] A 17th aspect of the present invention is a storage battery system according to the 16th aspect, characterized in that, in the calculation process, the control device identifies the predicted profile by including the contribution of past operation of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

[0035] An eighteenth aspect of the present invention is a storage battery system according to any one of the fifteenth to seventeenth aspects, characterized in that the first and second discharge start preparation times are set to the same time.

[0036] A nineteenth aspect of the present invention is a storage battery system according to any one of the fifteenth to seventeenth aspects, characterized in that the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

[0037] A twentieth aspect of the present invention is the storage battery system according to any one of the fifteenth to seventeenth aspects, characterized in that the operating temperature range is 280°C to 350°C.

[0038] A twenty-first aspect of the present invention is a storage battery system according to any one of the fifteenth to seventeenth aspects, characterized in that the storage battery comprises an assembled battery composed of a plurality of single cells, each of which is a sodium-sulfur battery, and a housing that houses the assembled battery.

[0039] According to the first to twenty-first aspects of the present invention, the discharge capacity of the storage battery can be increased while reducing the operating load on the heater, compared to conventional control aspects.

[0040] 1 is a diagram showing a general configuration of a storage battery system 100. FIG. 1 is a schematic vertical cross-sectional view showing a specific embodiment of a storage battery 12. FIG. 2 is a diagram showing a schematic electrical connection mode of a plurality of single cells 14 in a battery assembly 16 housed in a box body 42. FIG. 3 is a block diagram showing functional components of a storage battery control device 10. FIG. 4 is a diagram for explaining improved control. FIG. 5 is a diagram showing a comparison of a predicted profile PF2 of battery temperature in improved control with predicted profiles PF2α and PF2β of battery temperature in conventional control α and conventional control β. FIG. 6 is a diagram showing the effect of improved control on discharge capacity. FIG. 7 is a diagram showing the effect of improved control on discharge capacity. FIG. 8 is a diagram for explaining a modified example of improved control. FIG. 9 is a block diagram of a first configuration example of an application example. FIG. 10 is a block diagram of a second configuration example of an application example.

[0041] 1 is a diagram showing a schematic configuration of a storage battery system 100 according to this embodiment. The storage battery system 100 mainly includes a storage battery control device 10 and a storage battery (storage battery main body) 12 that is to be controlled by the storage battery control device 10.

[0042] Figure 2 is a schematic vertical cross-sectional view showing one specific embodiment of the storage battery 12. The storage battery 12 is generally a module battery having a configuration in which an assembled battery 16 composed of a plurality of cells 14 is housed in a housing 18. Although shown separately in Figure 1 for convenience, the housing 18 further includes a heat sink 22 and a heater 24 as temperature maintaining means 20 for maintaining the temperature of the storage battery 12 (more specifically, the temperature inside the housing 18) within a certain allowable range (operating temperature range) during operation of the storage battery 12. A temperature sensor 26 for measuring the temperature inside the housing 18 is also provided.

[0043] 2 does not necessarily reflect the actual location of the temperature sensor 26. The actual location of the temperature sensor 26 within the housing 18 may be determined as appropriate, and multiple temperature sensors 26 may be arranged.

[0044] As shown in Fig. 2, the housing 18 is made up of a box 42 and a lid 44 that closes the opening of the box 42. Fig. 3 is a diagram schematically showing the electrical connection state of the plurality of cells 14 in the battery assembly 16 housed in the box 42.

[0045] The box 42 has a generally rectangular parallelepiped shape and includes four side walls (first side wall 68a to fourth side wall 68d) and one bottom wall, with an opening on the side facing the bottom wall. The box 42 is placed and fixed on a horizontal base 40 made of, for example, steel, with the opening facing vertically upward.

[0046] Box 42 is made of, for example, a stainless steel plate and has a box-like shape with a hollow portion 48. Cover 44 includes a top wall 52 and a canopy 54. Like box 42, cover 44 is also made of, for example, a stainless steel plate and has a box-like shape with a hollow portion 56.

[0047] The hollow portion 48 of the box 42 and the hollow portion 56 of the lid 44 are both airtightly sealed spaces, and are structured to be able to communicate with the outside space by means of vacuum valves (not shown). These hollow portions 48 and 56 are each evacuated with the vacuum valves open (the air in the hollow portions is discharged to the outside space), and then the vacuum valves are closed to disable communication with the outside space. This allows the box 42 and the lid 44 to have a vacuum insulation structure.

[0048] The plurality of cells 14 that make up the battery pack 16 are housed in the box 42 with their axial direction aligned with the vertical direction (the direction from the bottom wall of the box 42 toward the opening).

[0049] In this embodiment, the unit cells 14 are assumed to be sodium-sulfur batteries (NaS batteries) that use sulfur as a positive electrode active material and metallic sodium as a negative electrode active material. In a NaS battery, for example, sulfur impregnated in graphite felt and metallic sodium are housed in a cylindrical aluminum container (cell) while being separated by a solid electrolyte tube made of β-alumina.

[0050] During discharge from the storage battery 12, an exothermic reaction occurs in each cell 14, in which metallic sodium reacts with sulfur to produce sodium polysulfide, causing the temperature of the storage battery 12 to rise. However, the heat resistance of the components of the NaS battery cell 14, particularly the solid electrolyte tube, aluminum container, and α-alumina insulating ring interposed between the two when they are joined, as well as the glass joints, TCB joints, and aluminum welds that seal between these components, is limited. Furthermore, if these components come into contact with highly chemically active substances such as sodium, sulfur, and sodium polysulfide at high temperatures for long periods of time, corrosion and deterioration are likely to occur. Therefore, it is undesirable for the temperature of the cell 14 to exceed a certain value due to continued discharge, i.e., the continued exothermic reaction.

[0051] On the other hand, the conductivity of sodium ions in the solid electrolyte β-alumina and the conductivity of the positive electrode active material sulfur and sulfur-impregnated graphite felt increase with increasing temperature. In other words, the higher the temperature due to heat generated by discharge, the lower the internal resistance of the storage battery 12. Therefore, from the perspective of charge / discharge efficiency, it is preferable to operate the storage battery 12 at high temperatures. Moreover, considering the diffusibility of the active material in the positive electrode and the equilibrium of the exothermic reaction during discharge, operation at low temperatures is disadvantageous in terms of charge recovery.

[0052] Considering the utilization of heat generated by the exothermic reaction during discharge and the constraints imposed by the characteristics of the materials and components that make up the NaS battery, the storage battery 12 is generally operated within a temperature range of 280° C. to 350° C. Therefore, in this embodiment, this temperature range is considered to be the operating temperature range of the storage battery 12.

[0053] In addition, the operating temperature range of the storage battery 12 may be set to 305°C to 360°C, with priority given to reducing the internal resistance of the battery and improving charge / discharge recovery.

[0054] The battery assembly 16 is composed of one or more blocks 64, each of which is composed of several cells 14. Although not shown in Fig. 2, a positive electrode external terminal 60 and a negative electrode external terminal 62 are provided on the outside of the box 42, and the one or more blocks 64 are connected in series from the positive electrode external terminal 60 to the negative electrode external terminal 62. Each block 64 is composed of two or more strings 66, each of which has two or more cells 14 connected in series, connected in parallel.

[0055] However, although FIG. 3 shows the battery assembly 16 connected to the positive electrode external terminal 60 and the negative electrode external terminal 62 that are respectively arranged on the outside of the opposing first side wall 68 a and second side wall 68 b of the box body 42 that is rectangular in plan view, and the battery assembly 16 connected along the opposing third side wall 68 c and fourth side wall 68 d, this is merely a schematic diagram, and the actual arrangement of the battery assembly 16 and the connection between the positive electrode external terminal 60 and the negative electrode external terminal 62 are not limited to this.

[0056] The storage battery 12 is connected to the DC side of a PCS (AC-DC converter: Power Conversion System) (not shown), the AC side of which is connected to a load, an external system, etc. via a transformer.

[0057] In this embodiment, the charging and discharging operation of the storage battery 12 is controlled by a charging and discharging control unit 2 (FIG. 4) provided in the storage battery control device 10, which will be described later.

[0058] Although the storage battery 12 may be used alone, in order to obtain higher output and power capacity, a battery unit in which multiple storage batteries 12 are electrically connected and integrated three-dimensionally may be used.

[0059] 2, heaters 24 are provided on the inner bottom surface and inner wall surface of the box 42 as part of the temperature maintaining means 20. The heaters 24 are used to maintain the storage battery 12 at a predetermined temperature during standby when no discharge is occurring, or to raise the temperature of the storage battery 12 (the temperature inside the housing 18) in order to operate a stopped storage battery 12. The heaters 24 are resistance heaters that are heated by external current, and their ON / OFF operation is performed by a mechanical relay. The ON / OFF operation of the heater 24 is controlled by a heater control unit 5 (FIG. 4) (described later) provided in the battery control device 10.

[0060] The gaps between the box 42 and the battery assembly 16 and the gaps between the cells 14 are filled with sand 46. The sand 46 also covers the openings of the box 42. The sand 46 not only transfers heat from the heater 24 to the cells 14 and absorbs heat generated by the cells 14, but also absorbs any contents that may leak out of the cells 14. Examples of the sand 46 include expanded vermiculite and silica sand.

[0061] As described above, the housing 18 is also provided with a heat dissipation device 22 as a temperature maintaining means 20. Because the reaction between metallic sodium and sulfur that occurs in each cell 14 during discharge from the storage battery 12 is an exothermic reaction, the temperature of the storage battery 12 rises as the discharge continues. The heat dissipation device 22 is used to dissipate heat from within the housing 18 in order to suppress such a temperature rise and ensure the discharge time.

[0062] As shown in FIG. 2, the heat dissipation device 22 includes a metal duct 72 , an electrically insulating plate member 74 , and a fan 76 for circulating the fluid 70 through the duct 72 .

[0063] In the duct 72, a fluid introduction section 78, a heat transport section 80, and a heat release section 82 are arranged in this order from upstream to downstream, forming a flow path for the fluid 70. The fluid 70 flows through the duct 72 as shown by arrows AR. The plate member 74 is embedded in the sand material 46 between the battery assembly 16 and the duct 72.

[0064] The fluid introduction section 78 is a section provided along the first side wall 68a of the box body 42 and adjacent to the fan 76. However, the fluid introduction section 78 and the first side wall 68a of the box body 42 are spaced apart from each other by the interposition of a buffer material 84. The buffer material 84 preferably has a heat insulating function.

[0065] When the fan 76 is operated (turned on), the fluid 70 is introduced from the fluid inlet 78 into the duct 72. The operation of the fan 76 is controlled by a heat dissipation control unit 4 ( FIG. 4 ) described below that is provided in the battery control device 10. The fluid 70 may be a gas such as air, nitrogen gas, or helium gas.

[0066] More specifically, the fluid introduction unit 78 has a fluid supply unit 86 to which the fluid 70 is supplied from the fan 76, and a fluid guide unit 88 that communicates with the fluid supply unit 86 and guides the fluid 70 supplied to the fluid supply unit 86 to the heat transporting unit 80. The fluid supply unit 86 has an air chamber 90. Preferably, the duct of the air chamber 90 has a shape that gradually becomes larger toward the fluid guide unit 88.

[0067] The heat transporting part 80 is a part that is mainly installed between the top wall 52 of the lid 44 and the box 42. The heat generated in the box 42 is transported downstream by the fluid 70 that flows through the heat transporting part 80.

[0068] The lower surface 80a of the heat transporting part 80 faces the battery pack 16 (and the plate member 74), and the lower surface 80a is provided with a plurality of metal fins 92 extending toward the battery pack 16. The fins 92 are provided for the purpose of further improving the efficiency of heat transfer from the inside of the box body 42 to the heat transporting part 80.

[0069] Preferably, a plurality of support parts (not shown) for maintaining the shape of the pipe 94 are installed inside the pipe 94 of the heat transporting part 80. As such support parts, flat, corrugated or strip-shaped members can be used.

[0070] The heat release portion 82 is a portion that is open to the outside and is provided in contact with the second side wall 68b of the box body 42. When the fluid 70 is released from the heat release portion 82, heat generated within the housing 18 is released (dissipated) to the outside.

[0071] In the heat dissipation device 22 having the above configuration, as the fan 76 is driven, cooled (e.g., room temperature) fluid 70 is supplied from the fluid inlet 78 into the duct 72. Accordingly, heat generated within the housing 18 (particularly within the box 42) is transferred to the fluid 70 flowing through the heat transporting section 80, causing the fluid 70 to heat up. The heated fluid 70 is released to the outside through the heat releasing section 82, thereby dissipating heat from the housing 18. As described above, both the box 42 and the lid 44 have a thermally insulated structure. This forced heat dissipation (cooling) efficiently cools the inside of the housing 18. This allows the temperature of the storage battery 12 to be maintained within the operating temperature range, enabling the storage battery 12 to continue operating in an appropriate operating environment, even when the discharge output is high or the discharge time is long.

[0072] <Storage Battery Control Device> Next, a description will be given of the storage battery control device 10 that controls the operation of the storage battery 12. Fig. 4 is a block diagram showing functional components of the storage battery control device 10.

[0073] The battery control device 10 can be realized by a general-purpose or dedicated computer (control computer) equipped with a CPU, memory, storage, etc. By loading and executing a predetermined program stored in the storage into the CPU, the battery control device 10 mainly includes, as functional components, a charge / discharge schedule acquisition unit 1, a charge / discharge control unit 2, a temperature control schedule creation unit 3, a heat dissipation control unit 4, and a heater control unit 5.

[0074] The charge / discharge schedule acquisition unit 1 acquires a charge / discharge schedule SC1, which is data describing the charge and discharge schedule for the storage battery 12 in a predetermined format, and provides the charge / discharge schedule SC1 to the charge / discharge control unit 2 and the temperature control schedule creation unit 3.

[0075] The charge / discharge schedule SC1 may be created outside the battery control device 10 and provided to the charge / discharge schedule acquisition unit 1, or the charge / discharge schedule acquisition unit 1 may have a function for creating the charge / discharge schedule SC1 realized by the above program, and the operator of the battery control device 10 may create the charge / discharge schedule SC1 using input means such as a mouse, keyboard, or touch panel (not shown) provided on the control computer.

[0076] The charge / discharge schedule SC1 describes, for example, the start and end times of charging and discharging, the output during discharging, the charge amount during charging, the operating temperature range, and the like.

[0077] The charge / discharge control unit 2 controls the charging and discharging operations of the storage battery 12 in accordance with the contents of the charge / discharge schedule SC1. The charge / discharge control unit 2 generally connects the storage battery 12 to the outside when the discharge start time described in the charge / discharge schedule SC1 arrives, starts discharging from the storage battery 12 to the outside, and then, when the discharge end time arrives, disconnects the storage battery 12 from the outside and ends the discharging. The charge / discharge control unit 2 also connects the storage battery 12 to the outside when the charge start time described in the charge / discharge schedule SC1 arrives, starts charging the storage battery 12 from the outside, and then, when the charge end time arrives, disconnects the storage battery 12 from the outside and ends the charging. Known control methods can be appropriately applied to control the charging and discharging operations of the storage battery 12.

[0078] The charge / discharge control unit 2 also monitors the measurement value of the temperature sensor 26. If the measurement value obtained from the temperature sensor 26 is within the operating temperature range but approaches the upper or lower limit of the range, or if the measurement value does not satisfy the operating temperature range, the charge / discharge control unit 2 stops or postpones the charge / discharge in accordance with the contents of the charge / discharge schedule SC1.

[0079] The temperature control schedule creation unit 3 generates a heat dissipation schedule SC2, which is the operation schedule for the fan 76 provided in the heat dissipation device 22, and a heater schedule SC3, which is the operation schedule for the heater 24, according to the description of the charge / discharge schedule SC1, and provides these to the heat dissipation control unit 4 and the heater control unit 5, respectively.

[0080] The heat radiation schedule SC2 describes a period (heat radiation control period) during which the heat radiation control unit 4 controls the fan 76. The heater schedule SC3 describes a period (heat control period) during which the heater control unit 5 controls the heater 24.

[0081] The heat radiation control unit 4 controls the operation (ON / OFF switching) of the fan 76 during the heat radiation control period described in the heat radiation schedule SC2. The heater control unit 5 controls the operation (ON / OFF switching) of the heater 24 during the heating control period described in the heater schedule SC3.

[0082] For example, the heat dissipation schedule SC2 may describe the timing of turning the fan 76 on / off during the heat dissipation control period, and the heat dissipation control unit 4 may turn the fan 76 on / off during the heat dissipation control period in accordance with the contents of the heat dissipation schedule SC2.

[0083] Alternatively, the heat dissipation schedule SC2 may describe one of the following control operations a to c for the entire heat dissipation control period or for each of several divided sub-periods, and the heat dissipation control unit 4 may turn the fan 76 ON / OFF in accordance with the described contents.

[0084] a) Switching the fan 76 ON / OFF depending on the temperature sensor measurement value; b) Keeping the fan 76 ON regardless of the temperature sensor measurement value; c) Keeping the fan 76 OFF regardless of the temperature sensor measurement value.

[0085] In addition, the heater schedule SC3 describes the timing of turning the heater 24 on and off during the heating control period, and the heater control unit 5 may be configured to turn the heater 24 on and off during the heating control period in accordance with the contents of the heater schedule SC3.

[0086] Alternatively, the heater schedule SC3 may describe any of the control operations d to f below for the entire heating control period or for each of several divided sub-periods, and the heater control unit 5 may turn the heater 24 ON / OFF in accordance with the described contents.

[0087] d) Switching the heater 24 ON / OFF depending on the temperature sensor measurement value; e) Keeping the heater 24 ON regardless of the temperature sensor measurement value; f) Keeping the heater 24 OFF regardless of the temperature sensor measurement value.

[0088] Regarding the ON / OFF switching of the heater 24 in d) above, the heater schedule SC3 may be written, for example, so that ON / OFF control is performed to set the temperature at the bottom surface of the box 42 to a target temperature. Furthermore, regarding the heater control operation d), the target temperature may be written for each of the divided multiple short periods.

[0089] In the battery control device 10 of the battery system 100 according to this embodiment having the above configuration, the charge / discharge control unit 2 controls the charge / discharge operation of the battery 12 in accordance with the charge / discharge schedule SC1, while the heat dissipation control unit 4 and the heater control unit 5 control the heat dissipation device 22 and the heater 24, respectively, in accordance with the heat dissipation schedule SC2 and the heater schedule SC3 created based on the charge / discharge schedule SC1. As a result, in the battery system 100, charge / discharge operations are performed while maintaining the temperature of the battery 12 (hereinafter simply referred to as the battery temperature) within a predetermined operating temperature range, and the temperature is maintained during standby when no charge / discharge operations are performed.

[0090] Generally speaking, when the temperature of the storage battery 12 rises (mainly during discharge), the heat dissipation control unit 4 controls the heat dissipation device 22 to suppress the temperature rise of the storage battery 12. When the storage battery 12 needs to be cooled (mainly after discharge is completed), the heat dissipation control unit 4 controls the heat dissipation device 22 to lower the battery temperature. When the storage battery 12 needs to be maintained at a predetermined temperature (mainly during standby and charging), the heater 24 is driven.

[0091] At this time, the temperature control schedule creation unit 3 creates a heat radiation schedule SC2 and a heater schedule SC3 based on the charge / discharge schedule SC1 so that the temperature of the storage battery 12 is appropriately controlled according to the start and end times of charge / discharge described in the charge / discharge schedule SC1. Then, the heat radiation control unit 4 controls the ON / OFF of the fan 76 of the heat radiation device 22 based on the created heat radiation schedule SC2. Also, the heater control unit 5 controls the ON / OFF of the heater 24 based on the created heater schedule SC3.

[0092] <Temperature control taking into account discharge start time> When the storage battery 12 discharges, the battery temperature rises as the discharge continues, eventually approaching the upper limit TU of the operating temperature range, even if heat is dissipated in parallel by the heat dissipation device 22. Discharge must be stopped before the battery temperature reaches the upper limit TU, and normally, the charge / discharge schedule SC1, as well as the heat dissipation schedule SC2 and heater schedule SC3, are created so that the battery temperature during discharge does not exceed the upper limit TU.

[0093] In contrast, after discharge is complete, reaction heat is no longer generated, so the battery temperature gradually decreases. Cooling can sometimes be accelerated by continuing to operate the heat dissipation device 22 for a certain period of time after discharge is complete. In any case, if the charge / discharge schedule SC1 includes a long standby period in which no discharge occurs after the previous discharge ends and before the next discharge begins, i.e., if the discharge interval is long, the battery temperature may drop to near the lower limit TL of the operating temperature range (e.g., 305°C to 305.1°C) during this standby period. Note that the heat dissipation device 22 is usually stopped during this temperature decrease.

[0094] From the viewpoint of making full use of the discharge capacity of the storage battery 12, it is considered preferable to make the battery temperature at the discharge start time as close as possible to the lower limit TL (=305°C) of the operating temperature range in order to delay as much as possible the timing at which the battery temperature reaches the upper limit TU of the operating temperature range. This is because the closer the battery temperature at the discharge start time is to the lower limit TL and the closer the battery temperature at the discharge end time is to the upper limit TU, the longer the discharge time will be.

[0095] This can be achieved, for example, by repeatedly turning the heater 24 on and off after the battery temperature reaches near the lower limit TL until the next discharge start time, thereby maintaining the battery temperature near the lower limit TL. Hereinafter, this type of control will be referred to as conventional control α.

[0096] However, in the case of the conventional control α, in order to maintain the battery temperature within a small temperature range of, for example, 0.1° C., it is necessary to repeatedly turn the heater 24 on and off in short cycles (for example, every 10 seconds).

[0097] However, operating the heater 24 based on the heater schedule SC3, which places such an operating load on the heater 24, is not desirable because it shortens the life of the contacts and coils of the relay (not shown) provided in the heater 24 and increases the frequency of relay replacement.

[0098] It is also possible to use the heat dissipation device 22 to maintain the temperature, but operating the fan 76 in addition to the heater 24 increases power consumption during standby, which is not desirable.

[0099] Alternatively, control may be performed to maintain the battery temperature higher than the lower limit TL until the discharge start time arrives in the standby state in order to reduce the number of times the heater 24 is turned on and off. Hereinafter, this type of control will be referred to as conventional control β.

[0100] However, such control has a drawback in terms of ensuring the above-mentioned discharge time.

[0101] In this embodiment, taking these points into consideration, the temperature control schedule creation unit 3 creates a heat release schedule SC2 and a heater schedule SC3 so that the battery temperature during standby is basically maintained at a temperature higher than the lower limit TL of the operating temperature range, as in the conventional control β, while temperature control (hereinafter also referred to as improved control) is performed to bring the battery temperature closer to the lower limit TL when the discharge start time arrives.

[0102] FIG. 5 is a diagram illustrating the improved control performed in this embodiment. FIG. 5 shows a predicted battery temperature profile PF1 for a certain day when the improved control is performed under a scheduled charge / discharge schedule SC1, and a profile (heater power profile) PFh showing the heater power consumption. The heater power profile PFh shown in FIG. 5 has intermittent peaks, which indicates that the heater 24 is intermittently turned on.

[0103] 5, the discharge start time t1 is set to 9:00 and the discharge end time t2 is set to 12:00 in the charge / discharge schedule SC1, so that the discharge time Δta is set to 3 hours. Also, the lower limit TL of the operating temperature range of the storage battery 12 is set to 305°C.

[0104] In the improved control, a temperature slightly higher than the lower limit TL of the operating temperature range (310°C in FIG. 1 ) is first set as the standby target maintenance temperature TS of the storage battery 12, and the battery temperature is maintained at the standby target maintenance temperature TS. In this case, even if the temperature drops slightly below the standby target maintenance temperature TS, no problems occur with the storage battery 12, and the battery temperature is controlled more gently than in the conventional control α, where the battery temperature is maintained near the lower limit TL. For example, the maintained temperature range can be a range of ±1°C centered on the standby target maintenance temperature TS.

[0105] The temperature control schedule creation unit 3 describes the standby target maintenance temperature TS and the maintenance temperature range in the heater schedule SC3. The heater control unit 5 then controls the heater 24 so that the temperature of the storage battery 12 during standby is maintained at the standby target maintenance temperature TS described in the heater schedule SC3.

[0106] On the other hand, as described above, it is preferable to keep the battery temperature at the discharge start time as close as possible to the lower limit TL of the operating temperature range. In consideration of this, in the improved control performed in this embodiment, the battery temperature, which is basically maintained at the standby target maintenance temperature TS higher than the lower limit TL as described above, is lowered to the lower limit TL at the timing when the discharge start time arrives.

[0107] However, in practice, the battery temperature may be lowered to a temperature within the operating temperature range that is close to the lower limit TL (hereinafter referred to as the lower limit temperature). For example, the battery temperature may be lowered to a temperature within the temperature maintenance range in the standby state under conventional control α. For simplicity, the following will be expressed as lowering the battery temperature to the lower limit TL of the operating temperature range, including such cases.

[0108] The battery temperature can be reduced by stopping the heater 24 and driving the fan 76. However, if these timings are too early, the battery temperature is predicted to fall below the lower limit TL before the discharge start time arrives, which ultimately makes it necessary to operate the heater 24 again, which is undesirable. Conversely, if the timing is too late, the battery temperature will remain higher than the lower limit TL when the discharge start time arrives, which is also undesirable.

[0109] In this embodiment, the temperature control schedule creation unit 3 sets the discharge start preparation time t0 in advance based on the start-time predicted temperature profile PFs, and when the discharge start preparation time t0 arrives, the heater control unit 5 stops heating by the heater 24 and the heat dissipation control unit 4 drives the fan 76.

[0110] The predicted start temperature profile PFs is a profile derived by the temperature control schedule creation unit 3 and indicates the relationship between an arbitrary time until the new discharge start time t1 and a predicted value of the battery temperature (predicted discharge start temperature) Ta at the discharge start time t1 when heating by the heater 24 is stopped at that time and the fan 76 is driven. Figure 5 also shows the predicted start temperature profile PFs and a predicted battery temperature profile PF1α when heating by the heater 24 is stopped at a certain time tk and the fan 76 is driven.

[0111] The temperature control schedule creation unit 3 derives the start-time predicted temperature profile PFs through a simulation (arithmetic processing) that takes into account the heat input and output to and from the storage battery 12 per unit time. Known techniques can be applied to such a simulation. For example, the following two modes are exemplified.

[0112] [First Mode] The time from a certain initial time to the discharge start time t1 is divided into predetermined time increments (unit time) Δt. Then, at time tk, when the kth time increment Δt has elapsed from the initial time, heating by the heater 24 is stopped and the fan 76 is driven. In this case, the change in heat quantity ΔH(m) contributing to the temperature change occurring during a certain time increment m (the mth time increment from the initial time) is the sum of the heat quantity heat(m) generated by the heater 24 and the heat quantity loss(m) dissipated by the fan 76 during that time increment m, and is expressed as follows:

[0113] ΔH(m)=-loss(m)+heat(m) (1) However, until time tk arrives, that is, in the range of m<k, the heater 24 and fan 76 are turned on / off according to the battery temperature, so heat(m) is the amount of heat generated when the heater 24 is turned on / off. Also, loss(m) is the amount of heat dissipated when the fan 76 is turned on / off according to the battery temperature.

[0114] On the other hand, after time tk arrives, that is, in the range m≧k, heating by the heater 24 is stopped and the fan 76 is driven, so heat(m) becomes 0 and loss(m) is the amount of heat dissipation when the fan 76 is turned on.

[0115] The temperature change of the storage battery from the initial time until time interval m has elapsed can be considered as the accumulation of temperature changes per unit time up to time interval m, so the temperature of the storage battery 12 at time interval m, Temp(m), can be expressed by the following equation: where C is the heat capacity of the storage battery 12 (a known constant).

[0116] Temp(m) = Temp(m -1) + ΔH(m) × Δt / C (2) By setting a time increment k corresponding to time tk and sequentially calculating the values ​​of Temp(m) from the initial time to discharge start time t1 according to equation (2), it is possible to obtain a predicted profile of the battery temperature when heating by the heater 24 is stopped and the fan 76 is driven at any time tk between the initial time and discharge start time t1. The battery temperature Temp(m) at discharge start time t1 in this prediction profile becomes the predicted discharge start temperature Ta.

[0117] The temperature control schedule creation unit 3 repeatedly generates a predicted profile while gradually delaying the time tk from the initial time (while changing the time increment k so that this occurs), thereby deriving a start-time predicted temperature profile PFs, which is a predicted profile in which the predicted discharge start temperature Ta becomes the lower limit value TL.

[0118] [Second Aspect] In the case of the storage battery 12 according to this embodiment, the box 42 is filled with sand 46, and therefore the heat capacity is large. Furthermore, the larger the storage battery 12, the larger the heat capacity. In the case of a storage battery 12 with such a large heat capacity, the effects of heat generation by the heater 24 and heat dissipation by the fan 76 do not immediately appear as a temperature change.

[0119] In this embodiment, a simulation is performed taking this point into consideration. Specifically, ΔH(m) is derived based on the following equation (3) instead of the above equation (1). This embodiment is effective when the heat capacity of the storage battery 12 is larger than the heat generation amount of the cells 14, the heat generation amount of the heater 24 during warmth keeping (standby), and the heat dissipation amount of the fan 76.

[0120]

[0121] Here, TRf(n×Δt) and TRh(n×Δt) are the contribution rates of the pre-operation of the fan 76 and the heater 24 to the temperature change in the target time step (unit time) n, respectively, as defined below.

[0122] TRf(n×Δt): The ratio of the amount of heat dissipated from the storage battery 12 when the fan 76 operates at a certain time interval mn to the temperature change at the temperature reference point at the time interval m that is a time n×Δt after the time interval mn; TRh(n×Δt): The ratio of the amount of heat generated from the heater 24 when the heater 24 heats the storage battery 12 at a certain time interval mn to the temperature change at the time interval m that is a time n×Δt after the time interval mn.

[0123] Here, the temperature reference point is a predetermined position (for example, the center position) within the storage battery 12 that is set as the target position for the predicted temperature.

[0124] Furthermore, N is the number of past time increments that are considered to contribute to the temperature change at time increment m. The value of N may be the same as the number of time increments from the initial time to time increment m, or may be set to the number of past time increments that actually contribute to the temperature change at time increment m if the contribution of temperature changes at time increments that are longer than a certain amount of time to the temperature change at time increment m can be ignored.

[0125] TRh(n×Δt) is preferably set based on the temperature change at the temperature reference point when the heater 24 is turned on for a unit time while the storage battery 12 is kept warm (standby).

[0126] TRf(n×Δt) is preferably set based on the temperature change at the temperature reference point when charging and discharging are stopped, the heater 24 is turned off, and the fan 76 is turned on for a unit time.

[0127] It is preferable to set TRf(n×Δt) and TRh(n×Δt) so that the difference between the actual operating data and the calculated value of the reference point temperature is small.

[0128] The simulation time, which is the time from the initial time to the discharge start time t1, is preferably set so that TRf(n×Δt) and TRh(n×Δt) are sufficiently small. For example, a time of about 20 to 60 minutes is exemplified. Furthermore, the time increment Δt is preferably set to a time that is sufficiently small compared to the simulation time. For example, a setting of about 10 seconds to 5 minutes is exemplified.

[0129] If the charge / discharge interval is short and the previous charge / discharge time is included in the simulation time, the temperature change contribution of heat generated by charge / discharge may be taken into account.

[0130] The temperature control schedule creation unit 3 sets the time at which the predicted discharge start temperature Ta reaches the lower limit value TL in the derived predicted start temperature profile PFs as the discharge start preparation time t0. More specifically, the predicted discharge start temperature Ta does not have to exactly match the lower limit value TL, but may be a value closest to the lower limit value TL within the operating temperature range. For simplicity, in this embodiment, this case is also included and may be referred to as the predicted discharge start temperature Ta reaching the lower limit value TL.

[0131] In the case of performing a simulation in the first and second modes described above, the simulation result in which Temp(m) is greater than the lower limit TL at the discharge start time t1 and in which the time tk was set earliest is set as the predicted start temperature profile PFs, and the time tk in the predicted start temperature profile PFs is set as the discharge start preparation time t0. This is because in such a case, Temp(m) at the discharge start time t1, i.e., the predicted discharge start temperature Ta, becomes the lower limit TL (or is closest to the lower limit TL within the operating temperature range).

[0132] Then, a heat radiation schedule SC2 and a heater schedule SC3 are created so that the fan 76 is driven and the heater 24 is stopped at the discharge start preparation time t0.

[0133] The predicted profile PF1α shown in FIG. 5 indicates that if heating by the heater 24 is stopped and the fan 76 is driven at time tk, the battery temperature at the discharge start time will fall below the lower limit TL of the operating temperature range. Meanwhile, in the predicted start temperature profile PFs, the predicted discharge start temperature Ta is 305°C, which is the lower limit TL of the operating temperature range, when the time is 4:30. This means that the predicted profile PF1α when the time tk is 4:30 is the predicted profile PF1. Therefore, when the predicted start temperature profile PFs shown in FIG. 5 is obtained, 4:30 is set as the discharge start preparation time t0.

[0134] When the heat dissipation control unit 4 and the heater control unit 5 respectively control the fan 76 and the heater 24 of the heat dissipation device 22 according to the heat dissipation schedule SC2 and the heater schedule SC3, which are described so that the fan 76 operates and the heater 24 stops as described above, and the charge / discharge control unit 2 causes the storage battery 12 to discharge from the discharge start time t1 to the discharge end time t2, the battery temperature will change according to the predicted profile PF1 shown in Figure 5.

[0135] That is, the battery temperature, which has been maintained at the standby target maintenance temperature TS until the discharge start preparation time t0 (=4:30), is gradually lowered at the discharge start preparation time t0 by stopping the heater 24 and operating the fan 76. Then, at the scheduled discharge start time t1 (=9:00), when the battery temperature reaches the lower limit, discharge begins.

[0136] By controlling charging / discharging and temperature in this manner, in the storage battery system 100 according to this embodiment, it is possible to maximize the time from the start of discharging until the battery temperature reaches the upper limit TU of the operating temperature range. In other words, it is possible to ensure a longer discharge time. In other words, it is possible to discharge the storage battery 12 while making the most of its discharge capacity.

[0137] After the discharge start time t1 arrives, the battery temperature rises over time while the discharge is in progress. Then, immediately after the discharge ends at the discharge end time t2, the battery temperature reaches its highest point and then decreases.

[0138] The standby target maintenance temperature TS is preferably set to a temperature approximately 1°C to 5°C higher than the lower limit TL of the operating temperature range. If the difference between the two is excessively large, the power consumption of the heater 24 during standby increases, and the time from the discharge start preparation time t0 to the discharge start time t1 becomes longer, which is not desirable. Conversely, if the difference between the two is almost zero, the maintenance temperature range during standby cannot be suitably secured, and there is essentially no difference from the conventional control α, which is also not desirable.

[0139] 5 also shows the battery temperature reaching the standby target temperature TS again at 9:00 PM, at which point the heater 24, which had been off until then, is driven again, maintaining the battery temperature at the standby target temperature TS. At this time, the fan 76 is stopped from operating until at least 9:00 PM. The heater and fan 76 are also operated in accordance with the heat release schedule SC2 and the heater schedule SC3. The discharge start preparation time t0 for the next discharge start time is set in the same manner as described above.

[0140] In addition, if multiple discharges are expected in one charge / discharge schedule SC1 acquired by the charge / discharge schedule acquisition unit 1, the temperature control schedule creation unit 3 may be configured to set the discharge start preparation time t0 corresponding to the discharge start time t1 for each discharge in advance.

[0141] Furthermore, if the charge / discharge pattern in the newly acquired charge / discharge schedule SC1 is the same as the charge / discharge pattern in the previously acquired and applied charge / discharge schedule SC1, the discharge start preparation time t0 set for the previous charge / discharge schedule SC1 may be set as the discharge start preparation time t0 in the new charge / discharge schedule SC1.

[0142] 6 is a graph showing a comparison of the battery temperature prediction profile PF2 under the improved control performed in this embodiment with the battery temperature prediction profiles PF2α and PF2β under the conventional control α and conventional control β. The configuration of the storage battery 12 is the same, and in both cases, the discharge start time t1 is 9:00, the discharge end time t2 is 17:00, and the discharge power is 150 kW. A discharge power profile PFe is also shown in FIG. 6.

[0143] Here, as described above, conventional control α is a control that keeps the battery temperature near the lower limit TL of the operating temperature range after discharge ends and until the next discharge start time, after the battery temperature reaches near the lower limit TL of the operating temperature range after discharge ends.

[0144] As described above, conventional control β is also a control that maintains the battery temperature higher than the lower limit TL in the standby state until the discharge start time arrives in order to reduce the number of times the heater 24 is turned on and off. In the example shown in Figure 6, for ease of comparison, the maintained temperature in conventional control β is set to 310°C, the same as the standby target maintenance temperature TS.

[0145] As shown in Figure 6 and Table 1, in conventional control α, heating by heater 24 is stopped (heater 24 is turned OFF) at discharge start time t1, and heat dissipation by fan 76 of heat dissipation device 22 is started (fan 76 is turned ON) when the battery temperature reaches 320°C. The same is true for conventional control β.

[0146] Furthermore, the discharge start preparation time t0 under improved control identified by the temperature control schedule creation unit 3 was 6:30.

[0147] Table 1 lists the main features of the conventional control α, the conventional control β, and the improved control. Note that the "number of heater on / off cycles" in Table 1 indicates the number of times the heater 24 is turned on / off per hour in the standby state.

[0148]

[0149] As shown in Figure 6 and Table 1, the highest battery temperature (peak temperature) was 345°C under the improved control, which was lower than the peak temperature of 346°C under the conventional control α. This is because, under the conventional control α, discharge is initiated with heat trapped inside the casing 18, whereas under the improved control, discharge is initiated with the heat trapped inside the casing 18 having been released. On the other hand, under the conventional control β, the peak temperature was 349°C, which is close to the upper limit TU (= 350°C) of the operating temperature range.

[0150] Furthermore, when comparing the number of times the heater is turned on and off in the standby state, the number of times in the improved control and conventional control β is suppressed to 1 / 10 of the number of times in the conventional control α.

[0151] Taking these results into consideration, the battery temperature control mode performed in this embodiment, in which the battery temperature when the storage battery 12 is in standby mode is maintained higher than the lower limit TL of the operating temperature range and is reduced to the lower limit when the discharge start time arrives, can be said to be more preferable than the conventional control α in terms of ensuring the life of the mechanical relay while ensuring at least the same or greater discharge capacity as the conventional control α.

[0152] 7 and 8 are diagrams showing the effect of the improved control performed in this embodiment on discharge capacity. Fig. 7 shows predicted battery temperature profiles for the improved control and conventional control β when the discharge power is 210 kW, along with a discharge power profile PFe1. The configuration of the storage battery 12 is the same, and the discharge start time t1 is 9:00 and the discharge end time t2 is 12:00.

[0153] As shown in Figure 7, in the prediction profile PF3 in the improved control, the peak temperature remained at 344°C, which was within a margin of the upper limit value TU of the operating temperature range, whereas in the prediction profile PF3β in the conventional control β, the peak temperature was 349°C, approaching the upper limit value TU.

[0154] In this way, the fact that the peak temperature of the improved control is lower than the peak temperature of the conventional control β means that the improved control has a smaller risk of the battery temperature exceeding the upper limit value TU of the operating temperature range when the storage battery 12 is actually operated than the conventional control β.From another perspective, this also means that there is some leeway in terms of discharge power and discharge time.

[0155] 8 shows the predicted battery temperature profiles under the improved control and the conventional control β when the discharge power is set to 220 kW, along with the discharge power profile PFe2. The other conditions are the same as those used to obtain the predicted profile shown in FIG.

[0156] 8, in the predictive profile PF4 of the improved control, the peak temperature was 349° C., which remained below the upper limit TU of the operating temperature range, whereas in the predictive profile PF4β of the conventional control β, the peak temperature was 355° C., exceeding the upper limit TU. This means that, assuming the same discharge time, the improved control can increase the discharge power by approximately 5% compared to the conventional control β.

[0157] 7 indicates that further discharge is possible even after the discharge end time, which is three hours after the discharge start time, until the upper limit value TU is reached. This means that, assuming the same discharge power, the improved control can extend the discharge time compared to the conventional control β.

[0158] The results shown in Figures 6 to 8 indicate that by adopting the temperature control of the storage battery performed in this embodiment, it is possible to increase the discharge capacity compared to conventional control β while ensuring the life of the relay contacts and coils in the same way as conventional control β.

[0159] As explained above, according to this embodiment, the temperature of a high-temperature operating storage battery, which is maintained within the operating temperature range during operation when charging and discharging are performed and during standby when charging and discharging are not performed, during standby until charging begins is maintained at a predetermined standby target maintenance temperature that is higher than the lower limit value of the operating temperature range, and is reduced to a temperature equivalent to that lower limit value at the timing when a predetermined discharge start time arrives.This makes it possible to reduce the operating load on the heater and increase the discharge capacity of the storage battery compared to conventional control modes.

[0160] <Modification> Fig. 9 is a diagram illustrating a modification of the improved control. Hereinafter, the improved control in the above-described embodiment will be referred to as improved control A, and the improved control according to the modification will be referred to as improved control B. Fig. 9 shows a predicted profile PF5 of the battery temperature when improved control B is performed, along with the predicted profile PF1 of the battery temperature and the discharge power profile PFe when improved control A shown in Fig. 6 is performed. Note that the predicted profile PF5 differs from the predicted profile PF2 only in the behavior indicated by the dashed line; therefore, for simplicity of illustration, only this portion is shown by the dashed line in Fig. 9. The behavior in other ranges is the same as the predicted profile PF1.

[0161] In improved control A, heating by heater 24 is stopped and fan 76 is driven simultaneously at discharge start preparation time t0, whereas in improved control B, as shown in Figure 9, heating by heater 24 is stopped first at heater stop time t0h (first discharge start preparation time) which is earlier than discharge start preparation time t0 in improved control A, and then fan 76 is driven at fan drive time t0f (second discharge start preparation time), thereby causing the battery temperature to reach lower limit TL. Temperature control schedule creation unit 3 performs a simulation to obtain such a predicted profile PF5, derives a start-time predicted temperature profile PFs, and sets the heater stop time t0h and the fan drive time t0f.

[0162] 9, in the prediction profile PF5, the battery temperature drops after the heater stop time t0h arrives and the heater 24 is stopped by the heater control unit 5. Then, when the fan drive time t0f arrives and the heat dissipation control unit 4 drives the fan 76, the battery temperature changes in the same manner as in the prediction profile PF1.

[0163] From another perspective, it can be said that improved control A is a control mode in improved control B in which the first discharge start preparation time t0h and the second discharge start preparation time t0f are set to the same time.

[0164] Improved control B is slightly inferior to improved control A in terms of the effect of heat dissipation from the housing 18, but when the discharge start time is the same, improved control B stops the heater 24 earlier than improved control A, so improved control B has the advantage of reducing heater power more than improved control A. Improved control A is suitable when there is a small margin between the battery temperature and the upper limit of the temperature range to be maintained in the standby state, but improved control B is suitable when this margin is small.

[0165] <Application Example> Hereinafter, a system configuration example will be described in which a storage battery 12 connected to an external commercial power grid is used to bid for electricity trading in an electricity market. The electricity market may be a wholesale electricity market, a capacity market, or a supply-demand balancing market.

[0166] In this case, the charge / discharge schedule SC1 for the storage battery 12 is determined so as to maximize the predicted value of revenue (predicted revenue) obtained as the difference between the predicted value of revenue from discharge from the storage battery 12 (predicted revenue) and the predicted value of the power cost (predicted cost) for operating the heat dissipation device 22 and the heater 24 in conjunction with the use of the storage battery 12. When charging the storage battery 12 by purchasing electricity from the wholesale electricity market, the storage battery 12 is discharged (sold) during the day when the electricity price is high and charged (purchased) during the night when the electricity price is low, and revenue is obtained by subtracting the amounts of both.

[0167] In the following, two examples of system configurations that can be adopted when bidding for buying and selling electricity in the electricity market using the storage battery 12 will be described.

[0168] First Configuration Example FIG. 10 is a block diagram of a case where the charge / discharge schedule SC1 is created by an energy management system (EMS) 200 provided separately from the storage battery control device 10. In FIG.

[0169] The owners of the EMS 200 and the storage battery system 100 are not limited, but are expected to be electricity consumers, electricity retailers, power generation companies, grid storage battery operators, etc. When the EMS 200 and the storage battery system 100 are owned by an electricity consumer, they perform overall power control for the consumer, such as control of power generation in a solar power generation device. The EMS 200 is realized by a general-purpose or dedicated computer equipped with a CPU, memory, storage, etc., and is capable of communicating with the storage battery control device 10.

[0170] A predetermined program stored in the storage is read into the CPU and executed, and the EMS 200 is provided with a power market price prediction unit 201 and a charge / discharge plan creation unit 202 as its main functional components.

[0171] The electricity market price prediction unit 201 predicts the electricity price in the electricity market to which the discharged electricity of the storage battery 12 will be sold, and generates predicted market price information IP. The prediction is performed at least for each target period for which the charge / discharge schedule SC1 is created, by simulation based on previous sales and purchase records in the electricity market, expected electricity demand, weather forecasts, etc.

[0172] The charge / discharge plan creation unit 202 creates a charge / discharge schedule SC1 for the storage battery 12 based on the generated expected market price information IP. As a result, in this configuration example, the charge / discharge schedule acquisition unit 1 of the storage battery control device 10 is only responsible for acquiring the charge / discharge schedule SC1 created by the charge / discharge plan creation unit 202.

[0173] As described above, the charge / discharge schedule SC1 is determined so as to maximize the predicted profit, which is the difference between the predicted profit when the storage battery 12 discharges and the predicted cost expected for using the storage battery 12.

[0174] More specifically, the charge / discharge schedule SC1 created by the charge / discharge plan creation unit 202 is first transferred to the charge / discharge schedule acquisition unit 1 of the storage battery control device 10. In the storage battery control device 10, the temperature control schedule creation unit 3 creates a heat radiation schedule SC2α and a heater schedule SC3α, which are a provisional heat radiation schedule SC2 and a heater schedule SC3, based on the charge / discharge schedule SC1 acquired by the charge / discharge schedule acquisition unit 1. These heat radiation schedule SC2α and heater schedule SC3α are transferred to the charge / discharge plan creation unit 202 of the EMS 200.

[0175] Then, the charge / discharge planning unit 202 calculates the predicted income expected from discharging (selling electricity) from the storage battery 12 when the storage battery 12 operates based on the created charge / discharge schedule SC1, calculates the predicted cost based on the acquired heat dissipation schedule SC2α and heater schedule SC3α, and calculates the difference between these values ​​as the predicted revenue.

[0176] The calculation of the predicted profit in this manner is repeated while changing the contents of the charge / discharge schedule SC1, and the charge / discharge schedule SC1 that maximizes the predicted profit is determined as the actual charge / discharge schedule SC1 and is used by the charge / discharge control unit 2 to control the charge / discharge of the storage battery 12. In addition, the heat dissipation schedule SC2 and heater schedule SC3 created in accordance with the determined charge / discharge schedule SC1 are used by the heat dissipation control unit 4 and heater control unit 5 to control the heat dissipation device 22 and heater 24.

[0177] [Second configuration example] Figure 11 is a block diagram of a case in which the charge / discharge schedule SC1 is created by EMS 200, as in the first configuration example, but the heat release schedule SC2 and heater schedule SC3 are created by a schedule creation device 300 that is provided separately from the battery control device 10.

[0178] The schedule creation device 300 can be realized by a general-purpose or dedicated computer (control computer) equipped with a CPU, memory, storage, etc. A predetermined program stored in the storage is read into the CPU and executed, and the schedule creation device 300 mainly includes, as functional components, a charge / discharge schedule acquisition unit 301 and a temperature control schedule creation unit 303.

[0179] The charge / discharge schedule acquisition unit 301 and the temperature control schedule creation unit 303 have substantially the same functions as the charge / discharge schedule acquisition unit 1 and the temperature control schedule creation unit 3, respectively, of the storage battery control device 10 in the first configuration example. In this configuration example, the storage battery control device 10 includes only the charge / discharge control unit 2, the heat radiation control unit 4, and the heater control unit 5, due to the inclusion of the schedule creation device 300. In other words, in this Cabinet Order, the components related to the creation of the heat radiation schedule SC2 and the heater schedule SC3 and the components responsible for controlling the storage battery 12 are provided in separate devices.

[0180] The schedule creation device 300 is capable of communicating with the storage battery control device 10 and the EMS 200. As a result, the schedule creation device 300 and the storage battery control device 10 may be located remotely. For example, the functions of the schedule creation device 300 may be implemented by a general-purpose computer located in a location remote from the location of the storage battery control device 10.

[0181] In this configuration example, similarly to the first configuration example, the charge / discharge schedule SC1, the heat radiation schedule SC2, and the heater schedule SC3 are determined so as to maximize the expected profit.

[0182] That is, the charge / discharge schedules SC1 created with different contents are each transferred from the charge / discharge planning unit 202 to the charge / discharge schedule acquisition unit 301 of the schedule creation device 300. In the schedule creation device 300, the temperature control schedule creation unit 303 acquires the charge / discharge schedule SC1, and creates a heat radiation schedule SC2α and a heater schedule SC3α based on the acquired charge / discharge schedule SC1. These heat radiation schedule SC2α and heater schedule SC3α are then transferred to the charge / discharge planning unit 202 of the EMS 200.

[0183] Then, the EMS 200 determines the charge / discharge schedule SC1 that maximizes the predicted profit as the actual charge / discharge schedule SC1. The determined charge / discharge schedule SC1 is passed to the charge / discharge control unit 2 and used to control the charge / discharge of the storage battery 12. The heat radiation schedule SC2 and heater schedule SC3 created in accordance with the determined charge / discharge schedule SC1 are passed from the schedule creation device 300 to the charge / discharge control unit 2 and used by the heat radiation control unit 4 and heater control unit 5 to control the heat radiation device 22 and the heater 24.

Claims

1. A control method for a high-temperature operating storage battery capable of being charged and discharged, comprising: maintaining the temperature of the storage battery at a predetermined temperature higher than the lower limit of the operating temperature range of the storage battery by heating the storage battery with a heater associated with the storage battery during standby when no discharge is occurring from the storage battery; setting a first discharge start preparation time, which is the timing to stop heating by the heater, and a second discharge start preparation time, which is the timing to activate a heat dissipation means associated with the storage battery, so that the temperature of the storage battery reaches the lower limit of the operating temperature range at the timing when a scheduled discharge start time arrives; stopping heating by the heater at the timing when the first discharge start preparation time arrives, and activating the heat dissipation means at the timing when the second discharge start preparation time arrives.

2. A method for controlling a storage battery as described in claim 1, comprising: performing arithmetic processing based on the flow of heat into and out of the storage battery per unit time in association with the operation of the heater and the heat dissipation means, thereby specifying a predicted profile of temperature change from a predetermined initial time to the discharge start time according to the timing of stopping heating by the heater and operating the heat dissipation means; and setting the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile in which the temperature at the discharge start time is the lower limit value to the first and second discharge start preparation times, respectively.

3. A method for controlling a storage battery as described in claim 2, characterized in that in the calculation process, the predicted profile is determined by taking into account the contribution of past operations of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

4. A method for controlling a storage battery according to any one of claims 1 to 3, characterized in that the first and second discharge start preparation times are set to the same time.

5. A method for controlling a storage battery according to any one of claims 1 to 3, characterized in that the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

6. A method for controlling a storage battery according to any one of claims 1 to 3, wherein the operating temperature range is 280°C to 350°C.

7. A method for controlling a storage battery according to any one of claims 1 to 3, characterized in that the storage battery comprises an assembled battery comprised of a plurality of single cells, each of which is a sodium-sulfur battery, housed in a housing.

8. A control device for a high-temperature operating storage battery capable of being charged and discharged, the storage battery comprising: a heater for heating the storage battery; and heat dissipation means; during standby when the storage battery is not discharging, the heater heats the storage battery so that the temperature of the storage battery is maintained at a predetermined temperature higher than the lower limit of the operating temperature range of the storage battery; a first discharge start preparation time at which heating by the heater is stopped and a second discharge start preparation time at which the heat dissipation means is activated are set so that the temperature of the storage battery reaches the lower limit of the operating temperature range at the timing when a scheduled discharge start time arrives; heating by the heater is stopped at the timing when the first discharge start preparation time arrives, and the heat dissipation means is activated at the timing when the second discharge start preparation time arrives.

9. A storage battery control device as described in claim 8, characterized in that a predicted profile of temperature change from a predetermined initial time to the discharge start time is determined according to the timing of stopping heating by the heater and operating the heat dissipation means by performing arithmetic processing based on the flow of heat in and out of the storage battery per unit time in conjunction with the operation of the heater and the heat dissipation means, and the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile at which the temperature at the discharge start time becomes the lower limit value is set to the first and second discharge start preparation times, respectively.

10. A storage battery control device as claimed in claim 9, characterized in that in the calculation process, the predicted profile is determined by taking into account the contribution of past operations of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

11. A storage battery control device according to any one of claims 8 to 10, wherein the first and second discharge start preparation times are set to the same time.

12. A storage battery control device according to any one of claims 8 to 10, wherein the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

13. A storage battery control device according to any one of claims 8 to 10, wherein the operating temperature range is 280°C to 350°C.

14. A storage battery control device according to any one of claims 8 to 10, characterized in that the storage battery comprises: a battery assembly consisting of a plurality of single cells, each of which is a sodium-sulfur battery; and a housing that houses the battery assembly.

15. A storage battery system comprising: a high-temperature operating storage battery capable of being charged and discharged; and a control device for the storage battery, wherein the storage battery comprises: a heater for heating the storage battery; and heat dissipation means; and the control device, during standby when the storage battery is not discharging, causes the heater to heat the storage battery so that the temperature of the storage battery is maintained at a predetermined temperature higher than the lower limit of the operating temperature range of the storage battery; sets a first discharge start preparation time, which is the timing for stopping heating by the heater, and a second discharge start preparation time, which is the timing for activating the heat dissipation means, so that the temperature of the storage battery reaches the lower limit of the operating temperature range at the timing when a scheduled discharge start time arrives; stops heating by the heater when the first discharge start preparation time arrives, and activates the heat dissipation means when the second discharge start preparation time arrives.

16. A storage battery system as claimed in claim 15, wherein the control device performs arithmetic processing based on the flow of heat into and out of the storage battery per unit time in association with the operation of the heater and the heat dissipation means, thereby specifying a predicted profile of temperature change from a predetermined initial time to the discharge start time according to the timing of stopping heating by the heater and operating the heat dissipation means, and sets the timing of stopping heating by the heater and operating the heat dissipation means in the predicted profile in which the temperature at the discharge start time is the lower limit value to the first and second discharge start preparation times, respectively.

17. A storage battery system as described in claim 16, wherein the control device, in the calculation process, determines the predicted profile by taking into account the contribution of past operations of the heater and the heat dissipation means to the heat input and output in the storage battery per unit time.

18. A battery system according to any one of claims 15 to 17, wherein the first and second discharge start preparation times are set to the same time.

19. A storage battery system according to any one of claims 15 to 17, wherein the maintenance temperature is set to a temperature 1°C to 5°C higher than the lower limit of the operating temperature range.

20. A storage battery system according to any one of claims 15 to 17, wherein the operating temperature range is 280°C to 350°C.

21. A storage battery system according to any one of claims 15 to 17, characterized in that the storage battery comprises: an assembled battery consisting of a plurality of single cells, each of which is a sodium-sulfur battery; and a housing that houses the assembled battery.

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