Energy storage system

Abstract

The goal is to secure the necessary amount of stored energy while keeping electricity purchase prices as low as possible. [Solution] An energy storage system comprising a storage battery that holds power and a charge / discharge control unit that controls the charging and discharging of the storage battery, further comprising: an acquisition unit that acquires price data indicating the price of electricity for each of a plurality of time slots set in a day; and a priority setting unit that refers to the price data and compares the price of electricity for each of the plurality of time slots on the day with each other to set the charging priority for each time slot, wherein the charge / discharge control unit is configured to determine whether or not to charge the storage battery in each time slot based on the charging priority.

Description

Technical Field

[0001] The present invention relates to a power storage system.

Background Art

[0002] Patent Document 1 describes a power storage system that purchases power when the electricity market price is lower than a predetermined reference value based on the electricity market price announced by the wholesale power exchange for the next day.

[0003] By using this power storage system, it becomes possible to operate to suppress the power purchase price for one day by charging during the daytime when the electricity market price is low and consuming the charged power at night when the price is high.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if charging is simply carried out during a time period when the price is lower than the reference value, there may be a case where power storage is completed before reaching the time period of the lowest price for one day and power cannot be purchased at the lowest price. Here, if the reference value is decreased in order to more reliably purchase power at the lowest price, there is a risk that the necessary amount of power storage cannot be secured.

[0006] Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to secure the necessary amount of power storage while suppressing the power purchase price as much as possible.

Means for Solving the Problems

[0007] In other words, the energy storage system according to the present invention is an energy storage system comprising a storage battery that holds power and a charge / discharge control unit that controls the charging and discharging of the storage battery, further comprising: an acquisition unit that acquires price data indicating the price of electricity for each of a plurality of time slots set in a day; and a priority setting unit that refers to the price data and compares the price of electricity for each of the plurality of time slots on that day with each other to set the charging priority for each time slot, wherein the charge / discharge control unit determines whether or not to charge the storage battery in each time slot based on the charging priority.

[0008] With this type of energy storage system, a high charging priority is set for time slots within the day when electricity prices are relatively low. By charging the necessary amount of energy during these high-priority time slots, it is possible to secure the required amount of stored energy while keeping electricity purchase costs down every day.

[0009] The charging and discharging control unit further comprises a calculation unit that calculates the number of time slots required to charge the current amount of stored energy in the battery to the target amount of stored energy for the day, and it is desirable that the charging and discharging control unit decide whether or not to perform charging in each time slot based on the number of required time slots and the charging priority. With this configuration, charging is performed for the required number of time slots during high-priority charging periods, allowing for efficient storage of the necessary amount of energy while keeping electricity costs down.

[0010] The charging priority is the ranking of each time slot when the multiple time slots are arranged in order of the lowest electricity price, and it is desirable for the charge / discharge control unit to determine to perform charging in a time slot in which the ranking of the charging priority is within the required number of time slots. With this configuration, charging is performed in order of the required number of time slots, starting with the time slots with the lowest electricity prices, minimizing the cost of purchasing electricity while ensuring efficient charging.

[0011] In each of the aforementioned time slots, it is desirable that the calculation unit calculates the required number of slots, and that the charge / discharge control unit determines whether or not to perform charging in the next time slot to be started based on the required number of slots. With this configuration, it is possible to appropriately determine whether or not to charge in the next time slot based on the latest current charge level and secure the necessary amount of charge. For example, if the amount of charge decreases due to power consumption, the number of required time slots increases, and charging can be performed even in time slots with a lower charging priority to secure the necessary amount of charge.

[0012] The system further includes a low-price day determination unit that determines whether each day is a low-price day based on the price data, and it is desirable that the target energy storage amount on low-price days be set to be greater than the target energy storage amount on non-low-price days. With this configuration, you can efficiently purchase electricity by changing the target storage amount according to the electricity price of the day. For example, on days when there is a large difference in electricity prices between time slots, there is a high probability that there is a time slot with very low prices. If you identify such days as low-price days and set a larger target storage amount, you can increase the amount of electricity charged during the low-price time slots and reduce the cost of purchasing electricity.

[0013] The target energy storage amount for each day should preferably be set based on past energy consumption for the same day of the week. With this configuration, it becomes possible to secure an efficient amount of stored energy, tailored to the trends in electricity consumption on each day of the week, that is, to the lifestyle of the consumer.

[0014] Setting charging priorities across the entire day necessitates considering electricity prices during periods when discharge is expected (e.g., nighttime), which increases the computational load. Therefore, it is desirable for the priority setting unit to set the charging priority by comparing the electricity prices of multiple time slots included in the charging period set for one day. With this configuration, the amount of computation can be reduced by, for example, setting the charging period while excluding the time frame in which discharge is expected. Furthermore, if the power charged during the rechargeable period can be used up during periods outside of that rechargeable period, it is possible to prevent situations where there is a surplus of power every day and optimize the charging and discharging cycle.

Advantages of the Invention

[0015] According to the present invention as described above, it is possible to secure the necessary power storage amount while suppressing the power purchase price as much as possible.

Brief Description of the Drawings

[0016] [Figure 1] Schematic diagram showing the configuration of a power storage system according to an embodiment of the present invention. [Figure 2] Explanatory diagram for explaining price data in the same embodiment. [Figure 3] Explanatory diagram for explaining priority data in the same embodiment. [Figure 4] Flowchart for explaining the priority setting process in the same embodiment. [Figure 5] Flowchart for explaining the charging determination process in the same embodiment. [Figure 6] Schematic diagram showing the configuration of a power storage system according to the second embodiment.

Modes for Carrying Out the Invention

[0017] Hereinafter, an embodiment of a power storage system according to the present invention will be described with reference to the drawings. In addition, for any of the figures shown below, for the sake of clarity, they are schematically drawn with appropriate omissions or exaggerations. For the same components, the same reference numerals are given and the description is appropriately omitted.

[0018] <Basic Configuration of Power Storage System 100> Physically, the power storage system 100 is composed of a supplier server X of a power supplier and a power storage facility S provided in a building of a customer. The supplier server X and the power storage facility S are configured to be communicable through a communication network.

[0019] <Supplier Server X> The supplier server X is a server operated by the power supplier that transmits information regarding electricity prices to the energy storage facility S. Physically, the supplier server X is a computer equipped with a CPU, memory, communication interfaces, etc. The supplier server X may be a virtualized computer located in, for example, the cloud. The supplier server X communicates with each customer's energy storage equipment S, the Japan Electric Power Exchange (JEPX) server, etc., via the communication network N.

[0020] This supplier server X is configured to perform its functions as an acquisition unit 1 and a priority setting unit 2, as shown in Figure 1, by coordinating the CPU and peripheral devices according to a program stored in a predetermined area of ​​its memory.

[0021] The acquisition unit 1 acquires price data showing the electricity price for each of several time slots set within a day. In this embodiment, the price data is acquired via a communication network and stored in a predetermined area of ​​the supplier server X's memory in chronological order.

[0022] More specifically, the price data is data showing the electricity price in the market. As shown in Figure 2(a), the price data here shows the electricity price for the following day for each 30-minute time frame (hereinafter also referred to as "time frame"), and is the so-called contract price in the spot market (one-day-ahead market) provided by the Japan Electric Power Exchange. In the pricing data, time slots are set in 30-minute increments, dividing a day into 48 time slots (48 segments), with electricity prices set for each time slot. For example, if the first time slot (1st segment) is from 0:00 to 0:30, then the 11th time slot (11th segment) would be from 5:00 to 5:30.

[0023] The price of electricity for each time frame is expressed in units such as yen / kWh.

[0024] The priority setting unit 2 refers to price data and compares the electricity prices of multiple time slots on the day to set the charging priority for each time slot. For example, the priority setting unit 2 compares the electricity price of the first time slot with the electricity prices of the other time slots to set the relative charging priority for the first time slot on the day. Similarly, the electricity price of the Nth time slot is compared with the electricity prices of the other time slots to set the relative charging priority for the Nth time slot.

[0025] In this case, the priority setting unit 2 of this embodiment does not set a charging priority for all time slots set for a day by comparing them with all other time slots, but rather sets a charging priority for multiple time slots that are included in a partially set charging period within a day by comparing the electricity prices of those time slots with each other. In other words, it is configured so that no charging priority is set for time slots that are not included in the charging period.

[0026] The rechargeable period is an arbitrary period set within the time frame during which charging is expected to be possible. In this embodiment, the rechargeable period is set as the period within a day excluding the period during which discharge is expected, when the period during the day is set as the scheduled discharge period. For example, if the scheduled discharge period is set from 16:00 to 24:00, the period from 0:00 to 16:00 will be set as the rechargeable period. In this case, a charging priority is set for the 32 time slots included in the rechargeable period.

[0027] The charging period is set in advance, for example, when the energy storage system 100 is implemented. The charging period may be changeable, and it does not necessarily have to be set. If it is not set, a charging priority is set for the entire time frame of the day.

[0028] In this embodiment, the charging priority is set as the rank of each time slot when multiple time slots included in the charging period are arranged in order of the lowest electricity price, as shown in Figure 2(b). For example, if the numbers indicating the charging priority are set as 1, 2, 3... in order of highest charging priority, then "1" will be set for the time slot with the lowest electricity price among the 1-32 time slots, and "5" will be set for the fifth lowest time slot.

[0029] The priority setting unit 2 collects the charging priorities for each time slot set in this way, compiles them into priority data on a daily basis, and transmits this data to the energy storage equipment S every day. The priority data in this embodiment is configured as a fixed-length data sequence formed by concatenating multiple fields, as shown in Figure 3, for example. The multiple fields include (1) a date field representing the date of the next day, (2) a region field identifying the region to be charged, and (3) a group of priority fields representing the charging priority for each time slot. Furthermore, it is preferable to add an LF (Line Feed) at the end of the priority data to indicate a data delimiter.

[0030] The regional field indicates the area where electricity is supplied. In Japan, this refers to one of several power areas established in accordance with the power transmission networks located throughout the country. The priority field group is provided for, for example, 32 time slots, and each priority field represents the charging priority in that time slot as a two-digit number.

[0031] This priority data is transmitted to the energy storage equipment S and stored in a predetermined area of ​​the supplier server X's memory in chronological order. Note that priority data does not necessarily have to include the date field or the region field.

[0032] <Energy Storage Equipment S> The energy storage system S has a charging function that receives power supplied from the commercial power source and charges the battery S1 with said power, an energy storage function that holds the charged power, and a discharge function that supplies the power stored in the battery S1 to loads installed in the building as needed. Physically, the energy storage system S comprises at least a battery S1 and a battery-side control device S2 that controls the charging and discharging of the battery S1. The energy storage system S of this embodiment is installed in buildings with relatively small electricity demands, such as houses, small businesses, or individual units in apartment buildings. However, the energy storage system S may also be installed in industrial buildings such as power generation facilities, substations, factories, or data centers where large-scale energy storage systems S are installed.

[0033] The battery S1 is a secondary battery that stores electricity and may consist of, for example, a lithium-ion battery, a lead-acid battery, a nickel-metal hydride battery, or a battery module combining these. Commercial power and a load are connected to the terminals of the battery S1.

[0034] The battery-side control device S2 is, physically, a dedicated or general-purpose computer equipped with a CPU, memory, communication equipment, input / output interfaces, etc. The battery-side control device S2 is configured to perform its functions as a calculation unit 3 and a charge / discharge control unit 4, as shown in Figure 1, by coordinating the CPU and peripheral devices according to a program stored in a predetermined area of ​​its memory.

[0035] The calculation unit 3 calculates the required number of time slots, which is the number of time slots needed to charge the current amount of stored energy in the battery S1 to the target amount of stored energy for the day. Specifically, the calculation unit 3 calculates the deficit to the target amount of stored energy from the difference between the target amount of stored energy and the current amount of stored energy, and calculates the required number of time slots by dividing this deficit by the amount of energy that can be charged per time slot (for example, 2 kWh / 30 minutes).

[0036] The current energy storage capacity is calculated based on, for example, the current and voltage of battery S1. The target energy storage capacity is set, for example, based on the total amount of electricity expected to be discharged during the planned discharge period. In this embodiment, the target energy storage capacity is set based on past electricity consumption on the same day of the week, for example, as the average of the electricity consumption for the two most recent days on the same day of the week. Furthermore, the target energy consumption may simply be the average of the daily energy consumption over a predetermined period in the past (for example, two weeks). Alternatively, the target energy consumption may be calculated by adding a predetermined amount of energy as a buffer to a value directly calculated from past energy consumption, or by multiplying that calculated value by a predetermined correction coefficient.

[0037] In this embodiment, the target amount of stored energy is set based on the attribute of the day of the week. However, the target amount of stored energy may also be set for other attributes of the day, such as weekdays and holidays, or for original attributes set by each consumer. In addition, the target energy storage capacity may simply be set to a fixed value such as the maximum energy storage capacity of battery S1 or a predetermined percentage of the maximum energy storage capacity.

[0038] The charge / discharge control unit 4 controls the charging of the storage battery S1 by determining whether or not to charge the storage battery S1 in each time frame based on the charging priority. The charge / discharge control unit 4 in this embodiment makes a decision on charging based on the required number of frames and the charging priority, and more specifically, it decides to charge if the charging priority ranking of the next time frame to start is within the required number of frames calculated before the start of that time frame.

[0039] <Operation of Energy Storage System 100> Next, referring to the flowcharts in Figures 4 and 5, we will explain examples of the charging priority setting process and the charging decision execution process for the energy storage system 100.

[0040] <Charging priority setting process> First, the acquisition unit 1 acquires the price data for the following day, which is published daily by the Japan Electric Power Exchange, on the same day. In this embodiment, the acquisition unit 1 acquires, for example, the price data published at 10:00 by 15:00 (step STT11).

[0041] Next, the priority setting unit 2 refers to the price data for the following day, sorts the electricity prices for the 1st to 32nd time slots included in the charging period in ascending order of price, and sets a charging priority (rank) for each time slot in descending order of price (step STT12). In this case, if there are time slots with the same electricity price, it is preferable to set a higher charging priority for the earlier time slot. This priority setting process S12 is executed, for example, at 17:00 every day.

[0042] Then, the priority setting unit 2 transmits priority data indicating the set charging priority from the supplier server X to the energy storage equipment S (step STT13). This transmission is performed, for example, at 19:00. Upon receiving the priority data, the energy storage device S stores it in a predetermined area of ​​the memory of the battery-side control device S2.

[0043] In this way, priority data is set and transmitted to the energy storage facility S on the same day that the price data for the following day is released.

[0044] <Execution process for determining charging> In this embodiment, the process for determining the charge in the next time frame is configured to be executed in the time frame immediately preceding it. Specifically, the calculation unit calculates the number of time slots required for charging when it is a predetermined time before each time slot (for example, 5 minutes before) (steps ST21 and ST22).

[0045] The charge / discharge control unit then determines whether or not to perform charging based on the calculated number of required slots and priority data previously received from the supplier server X (step ST23). In this embodiment, if the charging condition of required slots ≥ priority is met, charging is performed in the next time slot (step ST24); otherwise, charging is not performed in the next time slot (step ST25).

[0046] In this way, the required number of time slots is calculated for each time slot, and a decision is made as to whether or not to charge in the next time slot.

[0047] <Effects of this embodiment> In this embodiment of the energy storage system, a high charging priority is set for time slots within the day when electricity prices are relatively low. By charging the necessary amount during these high-priority time slots, it is possible to secure the required amount of stored energy while keeping electricity purchase costs down on a daily basis.

[0048] Furthermore, by charging only the required number of time slots from the highest-priority time slots, the necessary amount of charge can be secured without wasting energy. In addition, by not setting the target amount of stored energy to the maximum capacity of the battery, the period of full charge can be reduced, thereby lowering the load on the battery.

[0049] By making the decision of whether or not to charge based on a simple comparison between the required number of slots and the ranking, the load on this computational process can be reduced.

[0050] By setting target energy storage amounts for each day of the week, it becomes possible to secure an efficient amount of energy storage that matches the lifestyle of the consumer.

[0051] By setting the charging period to a portion of the day, the computational load can be reduced compared to a configuration that sets charging priorities and makes charging decisions for the entire day. Furthermore, by setting the charging period to exclude times when electricity demand is high and electricity prices are high, such as from 4 PM to midnight, it is possible to prevent missing out on charging during times when electricity prices are low.

[0052] <Second Embodiment> The energy storage system 200 according to the second embodiment further includes a low-cost day determination unit 5, as shown in Figure 6. The low-cost day determination unit 5 in this embodiment is configured to perform its functions through a supplier server X.

[0053] The low-price day determination unit 5 determines whether each day is a low-price day with low electricity prices. Specifically, the low-price day determination unit 5 compares the price of the most expensive time slot within a day with the price of the least expensive time slot within a day. If the price difference exceeds a predetermined low-price day determination value, the unit determines that the day is a low-price day.

[0054] When the acquisition unit 1 acquires price data, the low-price day determination unit 5 determines whether the day corresponding to the price data is a low-price day. If it determines that it is a low-price day, it sets a low-price day flag; if it determines that it is not a low-price day, it sets a non-low-price day flag.

[0055] In this embodiment, when it is determined to be a low-cost day, the target amount of stored energy for that day is set to be higher than the target amount of stored energy on days other than low-cost days.

[0056] In this embodiment, the priority setting unit 2 refers to the low-cost day flag and incorporates a low-cost day field indicating whether or not it is a low-cost day into the priority data, thereby transmitting the low-cost day information to the energy storage equipment S. Then, the calculation unit 3 of the energy storage equipment S refers to the low-cost day field of the priority data. If it is a low-cost day, it uses the target energy storage amount for low-cost days; otherwise, it uses the target energy storage amount for non-low-cost days. The target energy storage amount for low-cost days is set to a value greater than the target energy storage amount for non-low-cost days.

[0057] <Effects of the second embodiment> By determining which days are inexpensive and setting a high target storage amount for those days, it is possible to increase the amount of electricity charged during inexpensive time slots and reduce electricity purchase costs. On days with large price differences between time slots, there is a high probability that there are very inexpensive time slots, making it possible to appropriately identify inexpensive days. Furthermore, since such determination of inexpensive days is possible with only one day's worth of price data, the computational burden is small.

[0058] Furthermore, the determination of a low-price day may be based on a comparison with past price data or a comparison with a benchmark day's electricity price.

[0059] <Other Embodiments> Calculating the required number of time slots is not always necessary. In this case, for example, charging can be performed within a predetermined priority time slot.

[0060] In the above embodiment, the charging priority was set by assigning a priority order (1, 2, 3...) based on electricity prices, but it is not limited to this. For example, the charging priority may be set by classifying each time slot based on electricity prices.

[0061] The hardware configuration for performing functions such as the acquisition unit, priority setting unit, calculation unit, and charge / discharge control unit is not limited to the above embodiment. For example, functions such as the acquisition unit and priority setting unit may be performed using the energy storage equipment S or other control devices. Similarly, some or all of the functions such as the calculation unit and charge / discharge control unit may be performed using a supplier server or other control devices.

[0062] The communication device installed in the battery-side control unit should ideally be equipped with a SIM (Subscriber Identity Module), which is an IC card (or IC module) that records subscriber information for a mobile communication line. With this setup, the battery-powered control unit can easily perform wide-area communication. Furthermore, it simplifies line management, especially when moving.

[0063] The battery-side control unit preferably also includes a fan for cooling the communication equipment. This fan should operate based on a predetermined temperature condition, such as 35°C or higher.

[0064] The battery-side control device should ideally store power-related data such as the amount of electricity purchased, used, charged, and discharged for a predetermined period (e.g., the past month). This power-related data should be stored, for example, in 10ms increments.

[0065] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Explanation of Symbols]

[0066] 100, 200: Energy storage system X: Supplier Server S: Energy storage equipment S1: Battery S2: Battery-side control device 1: Acquisition part 2:Priority setting section 3: Calculation section 4: Charge / Discharge Control Unit 5: Low-cost day determination unit

Claims

1. An energy storage system comprising a battery for storing power and a charge / discharge control unit for controlling the charging and discharging of the battery, An acquisition unit that acquires price data showing the electricity price for each of several time slots set for one day, The system further includes a priority setting unit that refers to the price data and compares the electricity prices of the multiple time slots on the day with each other to set the charging priority for each time slot, The charge / discharge control unit is a power storage system that determines whether or not to charge the battery in each time frame based on the charging priority.

2. The system further includes a calculation unit that calculates the required number of time slots, which is the number of time slots necessary to charge the current amount of stored energy in the battery to the target amount of stored energy for the day. The energy storage system according to claim 1, wherein the charge / discharge control unit determines whether or not to perform charging in each time frame based on the required number of frames and the charging priority.

3. The charging priority is the ranking of each time slot when the multiple time slots are arranged in order of the lowest electricity price. The energy storage system according to claim 2, wherein the charge / discharge control unit determines to perform charging within a time frame in which the order of the charge priority is within the required number of frames.

4. The energy storage system according to claim 2 or 3, wherein the calculation unit calculates the required number of time slots in each of the aforementioned time slots, and the charge / discharge control unit determines whether or not to perform charging in the next time slot to be started based on the required number of time slots.

5. The system further includes a low-price day determination unit that determines whether each day is a low-price day based on the aforementioned price data. The energy storage system according to claim 2 or 3, wherein the target amount of energy stored on the low-cost day is set to be greater than the target amount of energy stored on days other than the low-cost day.

6. The energy storage system according to claim 2 or 3, wherein the target energy storage amount for each day is set based on past energy consumption on the same day of the week.

7. The energy storage system according to claim 1, wherein the priority setting unit sets the charging priority by comparing the electricity prices of multiple time slots included in a set charging period in one day.

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