Storage-type water heater

Abstract

To provide a hot water storage type water heater with high energy saving performance.SOLUTION: A hot water storage type water heater 100 is equipped with a controlling portion 11. The controlling portion 11 calculates dump power by subtracting an estimated value of use power of an electric apparatus 170 from an estimated value of supply power supplied from a photovoltaic power generation device 110 in a day time zone of the next day, performs a first boiling-up operation for boiling up hot water with a first heating performance by using the dump power in the day time zone, and performs a second boiling-up operation for boiling up it with a second heating performance by using power supplied from a commercial power supply 120 in a night time zone of the day. The controlling portion 11 predicts day time boiling-up generated calorific value when boiling up hot water by the first boiling-up operation, calculates night time boiling-up generated calorific value by subtracting the day time boiling-up generated calorific value from a total boiling-up calorific value of a day, decides the second heating performance with the optimal boiling efficiency, and decides boiling-up time of the second boiling-up operation on the basis of the night time boiling-up generated calorific value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a storage type water heater. [Background technology]

[0002] Storage-type water heaters that use electricity during the nighttime to perform boiling operations are widely used. In addition, in homes, facilities, and other buildings equipped with solar power generation, surplus electricity generated by solar power generation that is not consumed by other equipment in the building is used to perform boiling operations in the storage-type water heaters, and the surplus electricity is stored in a hot water storage tank as thermal energy. As shown in Patent Document 1, in conventional storage-type water heaters, when this surplus power is greater than a preset power setting, the heating capacity of the heating device is increased above the standard heating capacity, thereby making effective use of the surplus power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-191991 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, when surplus power is greater than the preset power, the heating capacity is increased above the standard heating capacity, which increases the amount of water boiled during the day and accordingly decreases the amount of water boiled at night.However, since the heating capacity at night is constant, water is boiled at a heating capacity higher than necessary, resulting in low energy-saving performance.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a storage-type water heater that has high energy-saving performance even when the amount of water heated at night is reduced. [Means for solving the problem]

[0006] The hot water storage type water heater of the present disclosure is installed in a building that receives power from a solar power generation device, and is equipped with a hot water storage tank for storing hot water, a heating unit for heating the hot water in the hot water storage tank, and a control unit for controlling the heating unit. The control unit calculates surplus power by subtracting a predicted value of the power consumption of electrical equipment used in the building from a predicted value of the power supply from the solar power generation device during the daytime hours of the next day, and performs a first boiling operation during the daytime hours to boil hot water at a first heating capacity using the surplus power, and performs a second boiling operation during the nighttime hours of the same day to boil hot water at a second heating capacity that is lower than the heating capacity required to boil the entire capacity of the hot water storage tank using power supplied from a commercial power source. The control unit predicts the amount of heat generated during daytime boiling when boiling water in the first boiling operation, and calculates the amount of heat generated during nighttime boiling by subtracting the amount of heat generated during daytime boiling from the total amount of heat generated during the day. The control unit determines the second heating capacity so as to optimize boiling efficiency, and determines the boiling time of the second boiling operation based on the amount of heat generated during nighttime boiling. [Effects of the Invention]

[0007] The hot water storage type water heater according to the present disclosure has the effect of having high energy-saving performance even when the amount of water boiled at night is reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the configuration of a storage type hot water heater according to a first embodiment. [Figure 2] 1 is a diagram showing a system configuration in a house in which a hot water storage type water heater according to a first embodiment is installed. [Figure 3] 1 is a diagram showing an outline of boiling control in the hot water storage type water heater according to the first embodiment. FIG. [Figure 4] 1 is a diagram showing an outline of boiling control in the hot water storage type water heater according to the first embodiment. FIG. [Figure 5] 1 is a diagram showing an outline of boiling control in the hot water storage type water heater according to the first embodiment. FIG. [Figure 6]3 is a flowchart showing the operation of the storage type hot water heater according to the first embodiment. [Figure 7] 3 is a diagram showing a data table included in the hot water storage type water heater according to the first embodiment. FIG. [Figure 8] 6(a) to 6(c) are diagrams showing examples of the start timing of the second boiling operation. [Figure 9] FIG. 10 is a diagram showing an example in which the heating capacity of the second boiling operation is changed midway. [Figure 10] 2 is a diagram showing an example of the hardware configuration of a control unit included in the hot water storage type water heater according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a hot water storage type water heater according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals. Duplicate descriptions of these parts will be appropriately simplified or omitted.

[0010] Embodiment 1 FIG. 1 is a diagram showing the configuration of a storage type water heater 100 according to the first embodiment. As shown in FIG. 1, the storage type water heater 100 includes a tank unit 10, an HP unit 50 that uses a heat pump cycle, a remote control 60 that issues operation commands and changes set values, and a communication control device 70 that receives information from a Home Energy Management System (HEMS) controller (described later). The HP unit 50 and the tank unit 10 are connected via an HP supply pipe 80, an HP return pipe 81, and electrical wiring (not shown). The tank unit 10 includes a built-in control unit 11. The operation of various valves, pumps, and the like provided in the tank unit 10 and the HP unit 50 is controlled by the control unit 11, which is electrically connected to these. The control unit 11 and the remote control 60 are connected to be able to communicate with each other. The control unit 11 and the communication control device 70 are also connected to be able to communicate with each other.

[0011] The HP unit 50 functions as a heating section for heating low-temperature water guided from the hot water storage tank 12 provided in the tank unit 10. The HP unit 50 has a compressor 51, a water-refrigerant heat exchanger 52, an expansion valve 53, and an air heat exchanger 54 connected in a ring shape by refrigerant piping 55 to form a heat pump cycle. The water-refrigerant heat exchanger 52 is used to exchange heat between the refrigerant flowing through the refrigerant piping 55 and the low-temperature water guided from the tank unit 10. The remote control 60 is equipped with a display section 61 that displays information such as the status of the hot water storage type water heater 100, an operation section 62 such as switches operated by the user, a speaker (not shown), a microphone (not shown), etc.

[0012] Tank unit 10 incorporates the following various components, pipes, etc. Hot water storage tank 12 is for storing hot water. A first water supply pipe 13a is connected to a water inlet 12a provided at the bottom of hot water storage tank 12. Water supplied from a water source such as a tap is adjusted to a predetermined pressure by a pressure reducing valve 14 and flows into hot water storage tank 12 through first water supply pipe 13a. A hot water inlet outlet 12b provided at the top of hot water storage tank 12 is connected to a hot water supply pipe 15 and a hot water delivery pipe 16 for supplying hot water stored in hot water storage tank 12 to the outside of storage-type hot water heater 100.

[0013] Hot water is stored in the hot water storage tank 12 so that a temperature difference occurs between the top and bottom, as high-temperature water heated using the HP unit 50 flows into the hot water inlet 12b and low-temperature water from the first water supply pipe 13a flows into the hot water storage tank 12 through the water inlet 12a. A plurality of hot water temperature sensors 17, 18 are attached at different heights to the surface of the hot water storage tank 12. These hot water temperature sensors 17, 18 detect the temperature distribution of the hot water in the hot water storage tank 12, thereby determining the amount of hot water remaining in the hot water storage tank 12 and controlling the start and stop of the hot water boiling operation in the hot water storage tank 12 by the HP unit 50.

[0014] The tank unit 10 incorporates a heat source pump 19 and a bath heat exchanger 20. The heat source pump 19 is a pump for circulating hot water through various pipes (described later) inside the tank unit 10, and is provided on the HP supply pipe 80. The bath heat exchanger 20 is a heat exchanger for using high-temperature hot water supplied from the hot water storage tank 12 and the HP unit 50 to heat the water to be heated on the secondary side (such as bath water or heating water).

[0015] In this embodiment, the secondary side configuration of bath heat exchanger 20 is illustrated and explained using bath supply piping 21 and bath return piping 22, which circulate hot and cold water in bathtub 82. Bath heat exchanger 20 is installed between bath supply piping 21 and bath return piping 22. Also, installed midway along bath return piping 22 are a bath circulation pump 23 for circulating bath water and a bath return temperature sensor 24 for detecting the temperature of the bath water leaving bathtub 82. Furthermore, installed midway along bath supply piping 21 is a bath supply temperature sensor 25 for detecting the temperature of the hot water leaving bath heat exchanger 20 after heat exchange.

[0016] One end of water outlet piping 26 is connected to water outlet 12c provided at the bottom of hot water storage tank 12, and the other end of water outlet piping 26 is connected to port a of three-way valve 27. One end of hot water outlet piping 28 is connected to port b of three-way valve 27, and the other end of hot water outlet piping 28 is connected to the primary outlet of bath heat exchanger 20. Furthermore, HP supply piping 80 is connected to port c of three-way valve 27.

[0017] The three-way valve 27 is a flow path switching means having ports a and b through which hot and cold water flows in and port c through which hot and cold water flows out, and is configured to be able to switch between the flow path from port a to port c and the flow path from port b to port c. That is, the three-way valve 27 switches the hot and cold water flow path within the tank unit 10 between two flow path configurations: one in which the water outlet pipe 26 is connected to the HP supply pipe 80, and one in which the hot water outlet pipe 28 is connected to the HP supply pipe 80.

[0018] One end of a first bypass pipe 29 is connected to a hot water inlet 12d provided between the center and bottom of the hot water storage tank 12, and the other end of the first bypass pipe 29 is connected to port a of a four-way valve 30. A second bypass pipe 31 branches off from the HP supply pipe 80 midway and is connected to port b of the four-way valve 30. Furthermore, an HP return pipe 81 is connected to port c of the four-way valve 30, and the hot water supply pipe 16 is connected to port d of the four-way valve 30.

[0019] The four-way valve 30 is a flow path switching means having ports b and c through which hot and cold water flows in and ports a and d through which hot and cold water flows out, and is configured to be able to switch between a flow path from port b to port a, a flow path from port c to port a, a flow path from port b to port d, and a flow path from port c to port d. That is, the four-way valve 30 switches the hot water flow path within the tank unit 10 among four flow path configurations: a configuration in which the second bypass pipe 31 and the first bypass pipe 29 are connected; a configuration in which the HP return pipe 81 and the first bypass pipe 29 are connected; a configuration in which the second bypass pipe 31 and the hot water supply pipe 16 are connected; and a configuration in which the HP return pipe 81 and the hot water supply pipe 16 are connected.

[0020] One end of a hot water inlet pipe 32 is connected to the hot water supply pipe 16, and the other end of the hot water inlet pipe 32 is connected to the primary inlet of the bath heat exchanger 20. One end of the hot water supply pipe 15 is connected to the hot water inlet outlet 12b, and the other end branches off and is connected to a hot water mixing valve 33 and a bath mixing valve 34, respectively. The hot water mixing valve 33 is connected to one end of a first hot water supply pipe 35, and the other end of the first hot water supply pipe 35 is connected to a hot water tap 36.

[0021] One end of a second hot water supply pipe 37 is connected to the bath mixing valve 34, and the other end of the second hot water supply pipe 37 is connected to the secondary outlet of the bath heat exchanger 20. A bath solenoid valve 38 that opens and closes the second hot water supply pipe 37 and a bath flow rate sensor 39 that detects the flow rate of hot water passing through the second hot water supply pipe 37 are provided midway along the second hot water supply pipe 37. One end of second water supply pipe 13b is connected to hot water mixing valve 33 and bath mixing valve 34, and the other end of second water supply pipe 13b is connected to pressure reducing valve 14. One end of third water supply pipe 13c is connected to pressure reducing valve 14, and the other end of third water supply pipe 13c is connected to a water source such as a tap. A temperature sensor 40 is provided midway along third water supply pipe 13c to detect the inlet water temperature of low-temperature water supplied from the water source. The first water supply pipe 13a, second water supply pipe 13b, and third water supply pipe 13c form a water supply line.

[0022] The hot water supply mixing valve 33 and the bath mixing valve 34 adjust the flow rate ratio between high-temperature hot water supplied from the hot water supply pipe 15 and low-temperature water supplied from the second water supply pipe 13b to generate hot water at the set temperature set by the user via remote control 60, and cause the hot water to flow into the first hot water supply pipe 35 and the second hot water supply pipe 37, respectively. The hot water whose temperature has been adjusted by the hot water supply mixing valve 33 is supplied from the first hot water supply pipe 35 via the hot water tap 36 to a faucet (not shown) such as a shower or faucet used by the user. Meanwhile, the hot water adjusted to the set temperature by the bath mixing valve 34 is supplied from the second hot water supply pipe 37 via the bath supply pipe 21 and the bath return pipe 22 to the bathtub 82.

[0023] Fig. 2 is a diagram showing a system configuration in a house A in which a hot water storage type water heater 100 according to the first embodiment is installed. As shown in Fig. 2, a solar power generation device 110 is installed on the roof of the house A. The solar power generation device 110 is a power generation module represented by, for example, a solar panel, and generates electricity by receiving sunlight. Also installed in the house A is a power conditioner 130 that converts DC power generated by the solar power generation device 110 into AC power that can be connected to a commercial power supply 120 system.

[0024] Furthermore, a distribution board 140, a power meter 150, and a HEMS controller 160 are installed inside the residence A. An outdoor air temperature sensor 170 for detecting outdoor air is also attached to the outer wall of the residence A. The building in which the hot water storage type water heater 100 is installed is not limited to the residence A, and may be, for example, a facility such as a sports gym or a nursing home. The solar power generation device 110 is not limited to being installed on the roof of the residence A, and may be installed in the garden of the residence A, for example.

[0025] A commercial power source 120 is connected to the distribution board 140 via a power meter 150. A power conditioner 130 is also connected to the distribution board 140. The distribution board 140 distributes the power supplied from the commercial power source 120 and the power converted by the power conditioner 130 to various electrical appliances 180 and storage type water heater 100 used in house A. A HEMS controller 160 is a controller of a home energy management system that manages the electrical appliances 180 and storage type water heater 100 in house A in an integrated manner.

[0026] The HEMS controller 160 is connected to the Internet 190 and acquires weather forecast information from a weather server or the like connected to the Internet 190. The weather forecast information includes sunshine forecast information and the like. The HEMS controller 160 is also connected to the power conditioner 130 so as to be able to communicate with it and acquires actual information on the amount of power generated by the solar power generation device 110. The HEMS controller 160 is also connected to the power meter 150 so as to be able to communicate with it and acquires actual information on the amount of power consumed by the electrical appliances 180 measured by the power meter 150. The HEMS controller 160 is also connected to the communication control device 70 so as to be able to communicate with it and transmits to the communication control device 70 the weather forecast information acquired from the Internet 190, the actual information on the amount of power generated by the power conditioner 130, and the actual information on the amount of power consumed by the power meter 150.

[0027] When the communication control device 70 receives weather forecast information, actual information on the amount of power generated, and actual information on the amount of power consumed, it transmits this information to the control unit 11 of the tank unit 10. Based on this information received from the communication control device 70, the control unit 11 determines the heating capacity and boiling time for the boiling operation during the nighttime hours of the day.

[0028] Next, an overview of the boiling control in the hot water storage type water heater 100 according to the first embodiment will be described with reference to Figures 3 to 5. In Figures 3 to 5, the nighttime period is from 11 PM to 7 AM, and the daytime period is from 7 AM to 5 PM, but these are not limited to these time periods and can be changed as appropriate depending on the time period for nighttime discount electricity rates, the time periods when the sun is up, etc.

[0029] FIG. 3 shows water heating control when the weather forecast for the next day is rain. When the weather forecast for the next day is rain, as shown in FIG. 3, there is little sunlight during the daytime hours, and therefore, in all of the time periods obtained by dividing the daytime hours into unit hours (hereinafter referred to as divided time periods), the predicted amount of power generated by the solar power generation device 110 the next day is less than the predicted amount of power consumed by the electrical appliances 180 in house A the next day. As a result, no surplus power is generated, and water heating is not performed during the daytime hours of the next day. Therefore, during the nighttime hours of the same day, the entire capacity of hot water in the hot water storage tank 12 is boiled at the third heating capacity. Here, the third heating capacity is the heating capacity required to boil the entire capacity of hot water in the hot water storage tank 12. In this example, the time width of the divided time periods (i.e., the time width of the unit time) is one hour.

[0030] Figure 4 shows water boiling control when the weather forecast for the next day is sunny. When the weather forecast for the next day is sunny, as shown in Figure 4, there is a lot of sunlight during the daytime hours, so in all divided time slots, the predicted amount of power generated by the solar power generation device 110 for the next day is higher than the predicted amount of power consumed by the electrical appliances 180 in house A for the next day. As a result, surplus power is generated during the daytime hours of the next day, and during the daytime hours of the next day, this surplus power is used to perform a first water boiling operation to boil water at a first heating capacity that is higher than the standard heating capacity. Note that the first heating capacity has a different value for each divided time slot. Then, during the nighttime hours of the same day, a second boiling operation is performed, which boils an amount of hot water that is less than the amount boiled by the first boiling operation at a second heating capacity. The second heating capacity is lower than the third heating capacity. Therefore, energy saving performance is higher than when boiling operation is performed at the third heating capacity.

[0031] FIG. 5 illustrates the water heating control when the weather forecast for the next day changes from sunny to rainy. If the weather forecast for the next day predicts sunny skies in the morning but rain in the afternoon, as shown in FIG. 5, the amount of sunshine in the morning will be high, so the predicted amount of power generated by solar power generation device 110 in the morning will be higher than the predicted amount of power consumed by electrical appliances 180 in house A in the morning. Also, the amount of sunshine in the afternoon will be low, so the predicted amount of power generated by solar power generation device 110 in the afternoon will be lower than the predicted amount of power consumed by electrical appliances 180 in house A in the afternoon. Therefore, surplus power will be generated in the morning, and a first water heating operation is performed in each divided time slot in the morning using this surplus power to boil water at a first heating capacity. Then, during the nighttime hours of the same day, a second water heating operation is performed in which an amount of water less than the amount boiled by the first water heating operation is boiled at a second heating capacity.

[0032] Next, the operation of the hot water storage type water heater 100 according to the first embodiment will be described with reference to the flowchart of FIG. 6. As shown in FIG. 6, the control unit 11 receives actual information on the amount of power generated and actual information on the amount of power consumed from the HEMS controller 160 via the communication control device 70 (step S10). Based on the received actual information on the amount of power generated, the control unit 11 predicts the power supply to be supplied from the solar power generation device 110 during the daytime hours of the following day. Based on the received actual information on the amount of power consumed, the control unit 11 also predicts the power consumption of the electrical appliances 180 used in the house A during the daytime hours of the following day (step S11). The control unit 11 then subtracts the predicted value of power consumption for each divided time slot into which the daytime hours are divided from the predicted value of power supply predicted in step S11 to calculate surplus power (step S12). Note that, when calculating the surplus power, past actual data on surplus power is also referenced. The actual information on the amount of power consumed also includes the amount of power consumed by the hot water storage type water heater 100 during the daytime hours.

[0033] Next, the minimum value of surplus power within the divided time slots calculated in step S12 is compared with a preset minimum surplus power for each divided time slot (step S13). If the minimum value of surplus power within any divided time slot is equal to or greater than the minimum surplus power, the amount of heat generated during daytime heating is predicted when a first heating operation is performed using the surplus power to boil water at a first heating capacity during the daytime hours of the following day (step S14). Furthermore, the amount of heat generated during daytime heating is subtracted from the total amount of heat generated during the day to calculate the amount of heat generated during nighttime heating (step S15). Here, the total amount of heat generated during the day is the amount of heat required to boil the amount of water required in a day, predicted from actual results over a certain period of time in the past.

[0034] Based on the amount of heat generated during nighttime boiling calculated in step S15, a second heating capacity that optimizes boiling efficiency and a boiling time for the second boiling operation are determined (steps S16 and S17). Specifically, the second heating capacity is determined using data table 200 shown in FIG. 7. As shown in FIG. 7, data table 200 is a table that lists heating capacities that optimize boiling efficiency for each outside air temperature, inlet water temperature, target hot water outlet temperature, and amount of remaining hot water in hot water storage tank 12. Data table 200 is stored in memory provided in control unit 11. The memory provided in control unit 11 will be described later.

[0035] At the start of the second heating operation, control unit 11 receives data on the outside air temperature detected by outside air temperature sensor 170. At the start of the second heating operation, control unit 11 also receives data on the inlet water temperature detected by temperature sensor 40. Control unit 11 also reads out target hot water outlet temperature data stored in memory. The target hot water outlet temperature data stored in memory is data previously input by the user operating operation unit 62 of remote control 60. At the start of the second heating operation, control unit 11 also receives temperature data on the hot water in hot water storage tank 12 detected by hot water storage temperature sensors 17 and 18. Control unit 11 determines the amount of hot water remaining in hot water storage tank 12 based on the received temperature data on the hot water in hot water storage tank 12.

[0036] Control unit 11 searches data table 200 using the outside air temperature, inlet water temperature, target outlet hot water temperature, and remaining hot water amount in hot water storage tank 12 obtained as described above, and extracts the heating capacity that optimizes the boiling efficiency as the second heating capacity (step S16). Furthermore, control unit 11 divides the nighttime boiling heat quantity calculated in step S15 by the second heating capacity extracted in step S16 to calculate the boiling time for the second boiling operation (step S17).

[0037] Next, during the nighttime hours of the day, control unit 11 performs a second boiling operation to boil water at the second heating capacity extracted in step S16 for the boiling time calculated in step S17 (step S18).Furthermore, during the daytime hours of the next day, control unit 11 performs a first boiling operation to boil water at the first heating capacity in the divided time slot where the minimum value of surplus power is greater than the minimum surplus power (step S19). Furthermore, in step S13, as a result of comparing the minimum value of surplus power with a preset minimum surplus power for each divided time period, if the minimum value of surplus power for all divided time periods is less than the minimum surplus power, control unit 11 performs a third boiling operation in the nighttime period on that day, boiling water at a third heating capacity higher than the second heating capacity (step S20). Here, the third heating capacity is the heating capacity required to boil the entire capacity of hot water storage tank 12 from a low water temperature state to the target hot water outlet temperature.

[0038] By performing the above-described operations, when the hot water storage type water heater 100 according to the first embodiment performs the first boiling operation using surplus electricity during the daytime hours of the following day, it boils hot water during the nighttime hours of that day at a second heating capacity that is lower than the third heating capacity required to boil the entire capacity of hot water in the hot water storage tank 12. Furthermore, the second heating capacity is the capacity that optimizes boiling efficiency. Therefore, the hot water storage type water heater 100 according to the first embodiment can achieve improved and optimized efficiency during boiling, thereby improving energy-saving performance.

[0039] Next, a specific example of the boiling control in the hot water storage type water heater 100 according to the first embodiment will be described. First, the boiling time in the second boiling operation will be described. When the first heating capacity in the first boiling operation is α, the minimum value of surplus power for each divided time period is β, and a value determined based on the coefficient of performance when the HP unit 50 is operating stably is γ, the first heating capacity α is calculated using the following formula (1).

[0040] α = β × γ …(1)

[0041] Furthermore, when the boiling time during the daytime is b, the boiling time b is the time when the surplus power is equal to or greater than the preset minimum surplus power, and the first boiling heat quantity c is calculated using the following formula (2).

[0042] c = α × b …(2)

[0043] Furthermore, when the amount of heat required for total boiling in one day calculated from the average value of past performance is a, and the amount of heat generated by boiling during the nighttime hours is d, the amount of heat d is calculated using the following formula (3).

[0044] d=ac …(3)

[0045] Next, when the second heating capacity is e, the second heating capacity e is set to the heating capacity that optimizes the boiling efficiency, which is extracted from data table 200 consisting of the outside air temperature, inlet water temperature, target outlet hot water temperature, and amount of remaining hot water in hot water storage tank 12, with reference to the outside air temperature at the start of the nighttime period, the inlet water temperature, the target outlet hot water temperature, and the amount of remaining hot water in hot water storage tank 12. Then, the boiling time (minutes) in the second boiling operation is calculated using the following formula (4) so that the total amount of heat generated by boiling for the day does not change.

[0046] Boiling time (min) = d / e / 60 … (4)

[0047] Here, for example, if the predicted surplus power β for each time period is 2.0 kW and the value γ, which is determined based on the coefficient of performance when the HP unit 50 is operating stably, is 3, and these are substituted into equation (1), the first heating capacity α becomes 6.0 kW. Furthermore, if the boiling time b during the daytime is 50 minutes and this is substituted into equation (2) together with the first heating capacity α, the first boiling heat quantity c generated by the first boiling operation becomes 18 MJ.

[0048] Furthermore, if the heat quantity a required for total boiling per day, calculated from the average value of past performance, is set to 37 MJ and substituted into equation (3) together with the first boiling heat quantity c, the heat quantity d generated by nighttime boiling operation will be 19 MJ. Also, if the second heating capacity e, determined based on the outside air temperature at the start of the nighttime hours, the inlet water temperature, the target outlet hot water temperature, and the amount of remaining hot water in the hot water storage tank 12, is set to 3.0 kW and substituted into equation (4) together with the heat quantity d, the boiling time in second boiling operation will be 105.6 (minutes).

[0049] Next, the time period during which the second boiling operation is performed will be described. When the amount of heat generated in the second boiling operation is the amount of heat generated during nighttime boiling, the boiling time during the second boiling operation is the time required to ensure the amount of heat generated during nighttime boiling when the control unit 11 boils water at the second heating capacity. The second boiling operation is performed during the entire nighttime hours or during part of the nighttime hours.

[0050] When the control unit 11 performs the second boiling operation throughout the entire nighttime period, the heating capacity, which determines the amount of heat required for boiling, can be relatively reduced. Furthermore, a reduction in the heating capacity improves the heating efficiency of the second boiling operation. Thus, by having the control unit 11 perform the second boiling operation throughout the entire nighttime period, the efficiency of the boiling operation can be improved and the boiling operation can be optimized.

[0051] On the other hand, when the control unit 11 performs the second boiling operation using a part of the nighttime period, the second boiling operation may be started simultaneously with the start time of the nighttime period, as shown in Fig. 8(a). Also, as shown in Fig. 8(b), the second boiling operation may be started in accordance with the timing at which boiling is completed at the end time of the nighttime period. Furthermore, as shown in Fig. 8(c), the second boiling operation may be performed during a time period of the nighttime period that does not include the start time or end time of the nighttime period.

[0052] For example, if the amount of heat generated by the second boiling operation is 40.5 MJ and the second heating capacity is 4.5 kW, the boiling time in the second boiling operation is 40.5 MJ / 4.5 kW = 9000 seconds = 2.5 hours. If the nighttime period is from 11:00 PM to 7:00 AM, and the second boiling operation starts at the same time as the start of the nighttime period, the start time of the second boiling operation will be 11:00 PM and the end time will be 1:30 AM. Similarly, if the second boiling operation starts in time to coincide with the completion of boiling at the end of the nighttime period, the start time of the second boiling operation will be 4:30 and the end time will be 7:00. Furthermore, if the second boiling operation is performed during a time period within the nighttime period that does not include the start time or end time of the nighttime period, if the start time of the second boiling operation is 1:00, the end time will be 3:30.

[0053] At the start of the nighttime period, many users are still using hot water for bathing, etc. Therefore, by starting the second boiling operation at the same time as the start of the nighttime period using control unit 11, the high-temperature hot water boiled by the second boiling operation can be immediately consumed by users. As a result, the second boiling operation can be used to boil water with optimal heating capacity, while minimizing heat loss caused by storing the boiled high-temperature hot water in hot water storage tank 12 for a long period of time.

[0054] Furthermore, by the time the nighttime period ends, many users have already used hot water to prepare breakfast, etc. Therefore, by having control unit 11 start the second boiling operation in time with the completion of boiling at the end of the nighttime period, users can immediately consume the high-temperature hot water boiled by the second boiling operation. As a result, the second boiling operation can be used to boil water with optimal heating capacity, while minimizing heat loss caused by storing the boiled high-temperature hot water in hot water storage tank 12 for a long period of time.

[0055] Furthermore, if there are many other water heaters that are set to start the second boiling operation at the same time as the start time of the nighttime period, or that are set to complete boiling at the end time of the nighttime period, the boiling time periods of these water heaters can be staggered by having the control unit 11 perform the second boiling operation during a time period that does not include the start time or end time of the nighttime period. In this way, the boiling time periods of other water heaters can be staggered, which makes it possible to perform boiling at the optimal heating capacity through the second boiling operation, while contributing to load leveling of the entire power system.

[0056] Next, the change in the second heating capacity in the second boiling operation will be described. In the second boiling operation, if boiling at the second heating capacity cannot secure the heat generation amount for nighttime boiling within the nighttime hours, the control unit 11 changes the second heating capacity to a heating capacity that will complete boiling within the nighttime hours. For example, if the amount of heat generated by nighttime boiling operation is 86.4 MJ and the second heating capacity is 2.5 kW, the boiling time in second boiling operation is 86.4 MJ / 2.5 kW = 34,560 seconds = 9.6 hours. If the nighttime period is from 11:00 PM to 7:00 AM, the second heating capacity cannot ensure the amount of heat generated by nighttime boiling during the 8 hours of the nighttime period.

[0057] Therefore, the control unit 11 changes the second heating capacity to 3.0 kW, which will complete boiling within the nighttime period. That is, when the second heating capacity is changed to 3.0 kW, the boiling time in the second boiling operation becomes 86.4 MJ / 3.0 kW = 28,800 seconds = 8.0 hours, and boiling can be completed within the nighttime period. In this way, by changing the second heating capacity, a sufficient amount of boiling water can be ensured during the second boiling operation, and a situation in which the amount of high-temperature hot water in the hot water storage tank 12 becomes insufficient can be prevented.

[0058] Next, a case where the first boiling operation is not performed will be described. In the flowchart shown in Fig. 6, if the minimum value of surplus power in all divided time periods is less than the minimum surplus power (step S13), the third boiling operation is performed in the nighttime period (step S20). In this case, the first boiling operation is not performed in the daytime period. The reason why the first boiling operation is not performed is as follows. That is, if the minimum value of surplus power is less than the power required for boiling, performing the first boiling operation requires the use of commercial power as well, which may undermine the benefits for the user. For this reason, the first boiling operation is not performed when the minimum value of surplus power is less than the preset minimum surplus power.

[0059] For example, if the surplus power obtained by subtracting the power used by other electrical equipment 180 from the power supplied from solar power generation device 110 is 1.2 kW and the preset minimum surplus power is 1.33 kW, the first boiling operation is not performed. In this way, by not performing the first boiling operation when the minimum value of surplus power is less than the power required for boiling, the use of commercial power can be reduced, thereby improving energy-saving performance.

[0060] Next, a case where the second heating capacity is changed during the second boiling operation will be described. 9, during the second boiling operation, control unit 11 may change the second heating capacity according to the outside air temperature, inlet water temperature, target outlet hot water temperature, and amount of remaining hot water in hot water storage tank 12. In other words, if there are fluctuations in the outside air temperature, inlet water temperature, target outlet hot water temperature, and amount of remaining hot water in hot water storage tank 12 during the second boiling operation, control unit 11 may re-extract the heating capacity from data table 200 and continue the second boiling operation at the re-extracted heating capacity.

[0061] If the second heating capacity is changed during the second boiling operation, the time required to generate the heat required for boiling during the nighttime period changes, so the time required for boiling is recalculated. That is, the calorific value Q1 of the hot water already boiled before the second heating capacity was changed is subtracted from the calorific value generated during nighttime boiling, and the remaining calorific value Q2 is divided by the changed second heating capacity to calculate the boiling time required after changing the second heating capacity. Note that if the changed boiling time does not fit within the nighttime period, the second heating capacity is changed again so that boiling is completed before the end of the nighttime period.

[0062] Here, a specific example of boiling operation in accordance with specific assumed conditions is shown as follows. For example, at the start of the second boiling operation, if the outside air temperature is 12°C, the inlet water temperature is 9°C, the target outlet hot water temperature is 65°C, and the remaining hot water volume is 200L, the heating capacity with optimal boiling efficiency extracted from data table 200 is 3.8kW. Therefore, at the start of the second boiling operation, boiling was performed with a heating capacity of 3.8kW. However, if the outside air temperature drops during the second boiling operation, and the outside air temperature becomes 9°C, the inlet water temperature is 8°C, the target outlet hot water temperature is 65°C, and the remaining hot water volume is 170L, the heating capacity with optimal boiling efficiency extracted from data table 200 is 3.5kW. Therefore, the heating capacity is changed from 3.8kW to 3.5kW, and the second boiling operation is continued. In this way, even if the heating capacity determined at the start of the second boiling operation is no longer optimal in terms of boiling efficiency, by changing the heating capacity to one that provides optimal boiling efficiency during the second boiling operation, hot water can be boiled at optimal boiling efficiency throughout the entire period of the second boiling operation, thereby improving energy-saving performance.

[0063] Here, if control unit 11 reduces the second heating capacity in the middle of the second boiling operation, a situation may occur in which the user mistakenly believes that something is wrong with the fact that boiling is not progressing. Therefore, the control unit 11 displays "Heating capacity optimization" on the display unit 61 of the remote control 60, so that the user will not mistake the lack of progress in boiling for an abnormality when waiting for boiling to occur overnight, for example. In this way, by notifying the user using the remote control 60, the user can be made aware that the reduction in the second heating capacity during the second boiling operation is a correct operation. In addition to the display on the display unit 61, the notification of a decrease in heating capacity may be made by a buzzer sound or a voice message such as "Heating capacity is currently being optimized" from a speaker (not shown) provided on the remote control 60.

[0064] Fig. 10 is a diagram showing an example of the hardware configuration of the control unit 11 of the hot water storage type water heater 100 according to embodiment 1. Fig. 10 shows the hardware configuration when the functions of the control unit 11 are realized using hardware that executes a program. The control unit 11 has a processor 11a, a memory 11b, and an interface 11c.

[0065] The processor 11a is a CPU (Central Processing Unit). The processor 11a may be a processing device, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). Each function of the control unit 11 is realized by the processor 11a, software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 11b, which is an internal memory. The memory 11b is a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory).

[0066] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Furthermore, embodiments may be combined with each other, and some of the configurations may be omitted or modified without departing from the spirit of the invention.

[0067] Various aspects of the present disclosure are summarized below as appendices.

[0068] (Appendix 1) A hot water storage type water heater installed in a building to which power is supplied from a solar power generation device, the hot water storage tank for storing hot water, a heating unit for heating the hot water in the hot water storage tank, and a control unit for controlling the heating unit, The control unit calculating surplus power by subtracting a predicted value of power usage by electrical equipment used in the building from a predicted value of power supply from the solar power generation device during daytime hours on the next day; During the daytime hours, a first boiling operation is performed to boil water at a first heating capacity by utilizing the surplus power, and during the nighttime hours of the same day, a second boiling operation is performed to boil water at a second heating capacity that is lower than the heating capacity required to boil the entire capacity of the hot water storage tank by utilizing power supplied from a commercial power source, A daytime amount of heat generated by boiling water during the first boiling operation is predicted, and a nighttime amount of heat generated by boiling water is calculated by subtracting the daytime amount of heat generated by boiling water from a total amount of heat generated by boiling water for one day. A storage type hot water heater that determines the second heating capacity so as to optimize boiling efficiency and determines the boiling time of the second boiling operation based on the amount of heat generated during the nighttime boiling. (Appendix 2) The second heating capacity is data extracted from a data table that summarizes heating capacities that optimize boiling efficiency for each outside air temperature, inlet water temperature, target hot water outlet temperature, and amount of remaining hot water in the hot water storage tank, A hot water storage type water heater according to claim 1, wherein the boiling time of the second boiling operation is a time obtained by dividing the amount of heat generated during the night-time boiling operation by the second heating capacity. (Appendix 3) The control unit When the surplus power is equal to or greater than the minimum surplus power, the first boiling operation and the second boiling operation are performed, A hot water storage type water heater as described in Appendix 1 or Appendix 2, in which, when the surplus power is less than the minimum surplus power, instead of the first boiling operation and the second boiling operation, a third boiling operation is performed using power supplied from a commercial power source during the nighttime hours of the day to boil water at a third heating capacity higher than the second heating capacity. (Appendix 4) the control unit calculates the surplus power for each divided time period obtained by dividing the daytime time period; the first boiling operation and the second boiling operation are performed when the surplus power is equal to or greater than the minimum surplus power in any of the divided time periods obtained by dividing the daytime time period, The hot water storage type water heater according to claim 3, wherein the third boiling operation is performed when the surplus power is less than the minimum surplus power in all divided time periods obtained by dividing the daytime time period. (Appendix 5) The hot water storage type water heater according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the second boiling operation starts simultaneously with a start time of the nighttime period. (Appendix 6) The hot water storage type water heater according to any one of appendices 1 to 4, wherein the second boiling operation is started in accordance with the timing when boiling is completed at the end of the nighttime period. (Appendix 7) A hot water storage type water heater described in any one of Appendix 1 to Appendix 4, wherein the second boiling operation is performed during a time period within the nighttime period that does not include the start time or end time of the nighttime period. (Appendix 8) A hot water storage type water heater described in any one of Appendix 1 to Appendix 7, wherein, during the second boiling operation, if boiling using the second heating capacity is not sufficient to generate the heat required for night-time boiling within the nighttime hours, the control unit changes the second heating capacity to a heating capacity that will complete boiling within the nighttime hours. (Appendix 9) A hot water storage type water heater as described in Appendix 2, wherein the control unit re-extracts the second heating capacity from the data table when there is a change in the outside air temperature, inlet water temperature, target outlet water temperature, or amount of remaining hot water in the hot water storage tank during the second boiling operation, and recalculates the boiling time of the second boiling operation based on the re-extracted second heating capacity. (Appendix 10) Further provided with a notification unit that notifies the boiling operation status, A hot water storage type water heater as described in Appendix 9, wherein the control unit causes the notification unit to notify of a decrease in heating capacity when the second heating capacity decreases as a result of re-extracting the second heating capacity. [Explanation of symbols]

[0069] 10 Tank unit, 11 Control unit, 12 Hot water storage tank, 40 Temperature sensor, 50 HP unit (heating unit), 60 Remote control (alarm unit), 61 Display unit, 62 Operation unit, 70 Communication control device, 82 Bathtub, 100 Hot water storage type water heater, 110 Solar power generation device, 120 Commercial power supply, 130 Power conditioner, 140 Distribution board, 150 Power meter, 160 HEMS controller, 170 Outdoor air temperature sensor, 180 Electrical equipment, 190 Internet, 200 Data table, A House.

Claims

1. A hot water storage type water heater installed in a building to which power is supplied from a solar power generation device, the hot water storage tank for storing hot water, a heating unit for heating the hot water in the hot water storage tank, and a control unit for controlling the heating unit, The control unit calculating surplus power by subtracting a predicted value of power usage by electrical equipment used in the building from a predicted value of power supply from the solar power generation device during daytime hours on the next day; During the daytime hours, a first boiling operation is performed to boil water at a first heating capacity by utilizing the surplus power, and during the nighttime hours of the same day, a second boiling operation is performed to boil water at a second heating capacity that is lower than the heating capacity required to boil the entire capacity of the hot water storage tank by utilizing power supplied from a commercial power source, A daytime amount of heat generated by boiling water during the first boiling operation is predicted, and a nighttime amount of heat generated by boiling water is calculated by subtracting the daytime amount of heat generated by boiling water from a total amount of heat generated by boiling water for one day. A storage type hot water heater that determines the second heating capacity so as to optimize boiling efficiency and determines the boiling time of the second boiling operation based on the amount of heat generated during the nighttime boiling.

2. The second heating capacity is data extracted from a data table that summarizes heating capacities that optimize boiling efficiency for each outside air temperature, inlet water temperature, target hot water outlet temperature, and amount of remaining hot water in the hot water storage tank, The hot water storage type water heater according to claim 1, wherein the boiling time of the second boiling operation is a time obtained by dividing the amount of heat generated during the nighttime boiling operation by the second heating capacity.

3. The control unit When the surplus power is equal to or greater than the minimum surplus power, the first boiling operation and the second boiling operation are performed, A hot water storage type water heater as described in claim 1 or claim 2, wherein when the surplus power is less than the minimum surplus power, instead of the first boiling operation and the second boiling operation, a third boiling operation is performed using power supplied from the commercial power source during the nighttime hours to boil water at a third heating capacity higher than the second heating capacity.

4. the control unit calculates the surplus power for each divided time period obtained by dividing the daytime time period; the first boiling operation and the second boiling operation are performed when the surplus power is equal to or greater than the minimum surplus power in any of the divided time periods obtained by dividing the daytime time period, The hot water storage type water heater according to claim 3, wherein the third boiling operation is performed when the surplus power is less than the minimum surplus power in all divided time periods obtained by dividing the daytime time period.

5. The hot water storage type water heater according to claim 1 or 2, wherein the second boiling operation starts simultaneously with a start time of the nighttime period.

6. The hot water storage type water heater according to claim 1 or 2, wherein the second boiling operation is started in accordance with the timing at which boiling is completed at the end of the nighttime period.

7. The hot water storage type water heater according to claim 1 or 2, wherein the second boiling operation is performed during a time period within the nighttime period that does not include a start time or an end time of the nighttime period.

8. A hot water storage type water heater as described in claim 1 or claim 2, wherein, during the second boiling operation, when boiling using the second heating capacity is not enough to secure the amount of heat generated for night-time boiling during the nighttime hours, the control unit changes the second heating capacity to a heating capacity that will complete boiling within the nighttime hours.

9. A hot water storage type water heater as described in claim 2, wherein the control unit re-extracts the second heating capacity from the data table when there is a change in the outside air temperature, inlet water temperature, target outlet water temperature, or amount of remaining hot water in the hot water storage tank during the second boiling operation, and recalculates the boiling time of the second boiling operation based on the re-extracted second heating capacity.

10. Further provided with a notification unit that notifies the boiling operation status, The hot water storage type water heater according to claim 9, wherein the control unit causes the notification unit to notify the decrease in heating capacity when the second heating capacity decreases as a result of re-extracting the second heating capacity.

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