Control method for electric water heaters and electric water heaters

Abstract

The present invention provides a control method for an electric water heater connected to a commercial power supply and a power generation device that minimizes the purchase of electricity from the commercial power supply and efficiently consumes surplus power from the power generation device. [Solution] A control method for an electric water heater 18 having a hot water storage tank 21 and connected to a distribution board 12 together with a commercial power supply 11 and a power generator 14, wherein a current sensor 35 is provided in the power supply line 31 between the distribution board 12 and the commercial power supply 11, and the power consumption of the electric water heater 18 is controlled in real time based on the current detection value continuously measured by the current sensor 35.

Description

Technical Field

[0001] The present invention relates to a control method for an electric water heater and an electric water heater.

Background Art

[0002] In the power supply system shown in Patent Document 1, a power generation device is provided in a home or the like. In such a power supply system, power generation and consumption are performed at the installation location, so power transmission loss is small. Furthermore, in the power supply system of Patent Document 1, since the commercial power supply is connected via AC / DC conversion and DC / DC conversion, the connection bus is controlled to have a predetermined voltage value without being affected by the voltage value of the commercial power system. Therefore, it is possible to operate an electric temperature riser (electric water heater) based on the voltage detected by the voltage detection means arranged on the connection bus.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in a power supply system in which an electric water heater equipped with a commercial power supply, a power generation device, and a hot water storage tank is directly connected by an alternating voltage without being converted to direct current, the voltage of the commercial power supply varies depending on the balance between the power load of surrounding houses and the power generation device. Therefore, the alternating voltage cannot be used for the purpose of controlling the power consumption of the electric water heater.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a control method for an electric water heater and an electric water heater that can efficiently consume surplus power of a power generation device by suppressing power purchase from a commercial power supply as much as possible in an electric water heater connected to a commercial power supply and a power generation device.

Means for Solving the Problems

[0006] The characteristic configuration of the control method for electric water heaters according to the present invention is: A control method for an electric water heater having a hot water storage tank and connected to a distribution board together with a commercial power supply and a power generation device, wherein a current sensor is provided in the power supply line between the distribution board and the commercial power supply, and the power consumption of the electric water heater is controlled in real time based on the current detection value continuously measured by the current sensor.

[0007] This configuration allows for real-time control of the electric water heater's power consumption based on current detection values ​​measured by a current sensor installed between the distribution board and the commercial power supply. The current flowing between the distribution board and the commercial power supply (current detection value measured by the current sensor) is completely unaffected by the power load of surrounding houses or power generation equipment, and can measure the surplus power of the power generation equipment and the power purchased from the commercial power supply in the house where the electric water heater is installed. Therefore, the power consumption of the electric water heater can be controlled in real time based on the current detection values ​​continuously measured by the current sensor. This allows for efficient consumption of surplus power generated by the power generation equipment when selling it, and reduces the amount of electricity purchased from the commercial power supply when buying electricity from the commercial power supply. As a result, electricity purchased from the commercial power supply can be minimized, and surplus power generated by the power generation equipment can be efficiently consumed by the electric water heater.

[0008] Further characteristic features of the control method for electric water heaters according to the present invention are: The current sensor is configured to measure the current detected from the distribution board to the commercial power supply, and controls the power consumption of the electric water heater in real time so that the current detected value becomes a first predetermined value.

[0009] This feature configuration allows for real-time control of the electric water heater's power consumption based on the detected current from the distribution panel to the commercial power supply. Current flows from the distribution panel to the commercial power supply when surplus power is generated by the power generation device. In such cases, by controlling the power consumption of the electric water heater so that the detected current value is set to a lower predetermined value, the surplus power from the power generation device can be efficiently consumed by the electric water heater.

[0010] Further characteristic features of the control method for electric water heaters according to the present invention are: The current sensor is configured to measure the current detected from the commercial power supply to the distribution board, and controls the power consumption of the electric water heater in real time so that the current detected value becomes a second predetermined value.

[0011] This feature configuration allows for real-time control of the power consumption of the electric water heater based on the current detected from the commercial power supply to the distribution panel. By controlling the power consumption of the electric water heater so that the detected current is set to a lower predetermined value, the amount of electricity purchased from the commercial power supply can be minimized.

[0012] Further characteristic features of the control method for electric water heaters according to the present invention are: The hot water storage tank is equipped with a temperature sensor that measures the temperature of the hot water inside the tank, and the electric water heater operates at its rated output when the hot water temperature measured by the temperature sensor is below a threshold.

[0013] In electric water heaters, if the water temperature in the storage tank is lower than a predetermined value, the electric water heater cannot supply water at the appropriate temperature. Therefore, in this feature configuration, when the water temperature in the storage tank is lower than a predetermined value, the electric water heater is operated at its rated output. This allows the electric water heater to quickly heat the water in the storage tank, thus suppressing the problem of supplying cold water from the electric water heater.

[0014] Further characteristic features of the control method for electric water heaters according to the present invention are: The hot water storage tank is equipped with a temperature sensor that measures the temperature of the hot water inside the tank. When the hot water temperature measured by the temperature sensor is above a threshold, the power consumption of the electric water heater is controlled in real time based on the current detection value continuously measured by the current sensor.

[0015] In electric water heaters, if the water temperature in the storage tank is below a predetermined threshold, the electric water heater cannot supply hot water at the appropriate temperature. Therefore, in this feature configuration, when the water temperature in the storage tank is above the threshold, the power consumption of the electric water heater is controlled in real time based on the current detection value continuously measured by the current sensor. As a result, the electric water heater can efficiently control power consumption while supplying hot water at the appropriate temperature from the storage tank.

[0016] Further characteristic features of the control method for electric water heaters according to the present invention are: The electric water heater comprises an AC / DC converter that converts alternating current voltage to direct current voltage, a semiconductor switch, and an electric heater that heats the hot water stored in the hot water storage tank. The power consumption of the electric heater can be controlled by adjusting the DC voltage by operating the semiconductor switch in real time based on the detected current value.

[0017] This configuration allows for quick and reliable control of the power consumption of the electric heater that heats the hot water in the hot water storage tank. This is achieved by operating a semiconductor switch in real time based on the current detection value between the distribution board and the commercial power supply to adjust the DC voltage.

[0018] Further characteristic features of the control method for electric water heaters according to the present invention are: The power generation device is configured to include at least one of a photovoltaic power generation device, a fuel cell, and a gas engine.

[0019] According to this feature configuration, any of the following can be used as the power generation device: a solar power generation device, a fuel cell, or a gas engine, and the power consumption of the electric water heater can be efficiently controlled.

[0020] A further characteristic configuration of the control method of the electric water heater according to the present invention is that the electric water heater is configured to include either an electric water warmer or an electric instant water heater in a thermos bottle.

[0021] According to this characteristic configuration, as the electric water heater, either an electric water warmer or an electric instant water heater in a thermos bottle can be used, and the power consumption of the electric water heater can be efficiently controlled.

[0022] A characteristic configuration of the electric water heater according to the present invention is that it is an electric water heater having a hot water storage tank and connected to a commercial power supply and a power generation device in a switchboard, a current sensor provided in a power supply line between the switchboard and the commercial power supply, and a control circuit for controlling the operation of the electric water heater, wherein the control circuit is configured to be able to control the power consumption of the electric water heater in real time based on a current detection value continuously measured by the current sensor.

[0023] According to this characteristic configuration, based on the current detection value measured by the current sensor provided between the switchboard and the commercial power supply, the power consumption of the electric water heater can be controlled in real time. The current flowing between the switchboard and the commercial power supply (the current detection value measured by the current sensor) can measure the surplus power of the power generation device and the purchased power from the commercial power supply in the house where the electric water heater to be controlled is installed without being affected by the power load of the surrounding houses or the power generation device at all. Therefore, the power consumption of the electric water heater can be controlled in real time based on the current detection value continuously measured by the current sensor. As a result, when selling the surplus power generated by the power generation device, the surplus power can be efficiently consumed, and when buying power from the commercial power supply, the amount of power purchased from the commercial power supply can be suppressed. As a result, it is also possible to suppress the power purchase from the commercial power supply as much as possible and efficiently consume the surplus power of the power generation device with the electric water heater.

Brief Description of the Drawings

[0024] [Figure 1] This is a schematic diagram showing a power supply system to which the present invention is applied. [Figure 2] This is a flowchart of the control method for an electric water heater according to the first embodiment. [Figure 3] This is a flowchart of the control method for an electric water heater according to the second embodiment. [Modes for carrying out the invention]

[0025] The following describes a control method for an electric water heater according to an embodiment of the present invention. While preferred embodiments are described below, these embodiments are provided to illustrate the present invention more concretely, and various modifications are possible without departing from the spirit of the invention. The present invention is not limited to the following description.

[0026] [First Embodiment] Figure 1 is a schematic diagram showing a power supply system according to an embodiment of the present invention. In Figure 1, reference numeral 10 denotes the power supply system. The power supply system 10 comprises a commercial power source 11, a distribution board 12, a power generation device 14 connected to the distribution board 12, household loads 16, and an electric water heater 18.

[0027] The power generation device 14 is comprised of at least one of the following: a solar power generation device that generates electricity using sunlight, a fuel cell, and a gas engine. The household load 16 is the electrical load in the household. The commercial power supply 11 and the distribution board 12 are connected by a power supply line 31. The distribution board 12 and the electric water heater 18 (AC / DC converter 23 described later) are connected by a power supply line 32. The distribution board 12 and the power generation device 14 are connected by a power supply line 33. The distribution board 12 and the household load 16 are connected by a power supply line 34. A current sensor 35 is attached to the power supply line 31.

[0028] The electric water heater 18 includes an AC / DC converter 23 that converts AC voltage to DC voltage, a semiconductor switch 24, and a control circuit 25 that controls their operation. In the electric water heater 18, the electric heater 22, AC / DC converter 23, semiconductor switch 24, and control circuit 25 are connected via a connection bus 36. The semiconductor switch 24 is configured to receive a control signal from the control circuit 25 and adjust the DC voltage flowing through the connection bus 36 in real time based on the current detection value measured by the current sensor 35.

[0029] The AC voltage transmitted from the distribution panel 12 to the electric water heater 18 is converted to a DC voltage by an AC / DC converter 23. The hot water storage tank 21 is equipped with an electric heater 22, which is configured to heat the hot water stored in the hot water storage tank 21. The electric heater 22 is connected to a connection bus 36 and operates on the power supplied from there, raising the temperature of the hot water in the hot water storage tank 21. The hot water storage tank 21 is also equipped with a hot water temperature sensor 26 that measures the temperature T of the hot water in the hot water storage tank 21.

[0030] The control circuit 25 consists of a microcomputer equipped with a CPU, ROM, memory, and input / output circuits, and monitors the operation of the AC / DC converter 23. If it detects excessive voltage or current, it stops supplying power to the connection bus 36.

[0031] Figure 2 is a flowchart showing the operation of the power supply system 10 when surplus power is generated by the power generation device 14 (i.e., when power is being sold). The flowchart in Figure 2 is executed when the power to the electric water heater 18 is turned on and by the control circuit 25.

[0032] In step #11, the current from the distribution board 12 to the commercial power supply 11 is measured by the current sensor 35, and the measured first current value (current detection value) A1 is transmitted to the control circuit 25 of the electric water heater 18. In step #12, the hot water temperature T of the hot water storage tank 21 is measured by the hot water temperature sensor 26, and the measured hot water temperature T is transmitted to the control circuit 25 of the electric water heater 18.

[0033] In step #13, it is confirmed whether the hot water temperature T of the hot water storage tank 21 satisfies the following conditions. Tset≦T <Tmax Here, Tset is the hot water supply setting temperature of the electric water heater 18, and Tmax is the design boiling temperature of the hot water storage tank 21.

[0034] In step #13, if the water temperature T satisfies the condition (step #13, Yes), then in step #14, it is confirmed whether the first current value (current detection value) A1 of the current sensor 35 is greater than or equal to the first predetermined value S1 (e.g., 100mA). The first predetermined value S1 can be set to any value (e.g., 0 to 100mA).

[0035] In step #14, if the first current value (current detection value) A1 satisfies the condition (step #14, Yes), then in step #15, the control circuit 25 transmits a control signal (e.g., a PWM control signal) to the semiconductor switch 24, and the power consumption of the electric heater 22 is controlled in real time so that the first current value (current detection value) A1 of the current sensor 35 becomes a first predetermined value S1 (e.g., 100mA).

[0036] In step #13, if the water temperature T does not meet the conditions (step #13, No), then in step #16, it is checked whether the water temperature T meets the following conditions. T <Tset Here, Tset is the hot water setting temperature of the electric water heater 18. Therefore, step #16 checks whether the water temperature T is less than the hot water setting temperature Tset.

[0037] In step #16, if the water temperature T satisfies the condition (step #16, Yes), then in step #17, the electric heater 22 is operated at its rated output. In other words, the power consumption of the electric heater 22 is not controlled by the control circuit 25.

[0038] In step #16, if the water temperature T does not satisfy the condition (step #16, No), then Tmax ≤ T will be satisfied. That is, since the water temperature T is greater than or equal to the design boiling temperature Tmax of the hot water storage tank 21, the semiconductor switch 24 is activated in step #18 to stop the electric heater 22.

[0039] In step #14, if the first current value (current detection value) A1 does not meet the condition (step #14, No), then the current from the distribution board 12 to the commercial power supply 11 is low, which is a state of selling electricity, and depending on the fluctuations in surplus power from the power generation device 14, there is a possibility that the electric heater 22 will be operated by purchased electricity. Therefore, in step #19, a control signal (e.g., a PWM control signal) is sent from the control circuit 25 to the semiconductor switch 24 to stop the electric heater 22.

[0040] As shown in the flow diagram in Figure 2, the power consumption of the electric water heater 18 is controlled so that the current flowing from the distribution board 12 to the commercial power supply 11 (first current value A1) reaches a predetermined value (first predetermined value S1). This allows for efficient consumption of surplus power generated by the power generation device 14 when it is sold. As a result, the purchase of electricity from the commercial power supply 11 is minimized, and the surplus power from the power generation device 14 is efficiently consumed by the electric water heater 18.

[0041] [Second Embodiment] Figure 3 is a flowchart showing the operation of the power supply system 10 when no surplus power is generated and power is supplied from the commercial power supply 11 (i.e., when power is purchased). The flowchart in Figure 3 is executed by the control circuit 25 when the power to the electric water heater 18 is turned on.

[0042] In step #21, the current from the commercial power supply 11 to the distribution board 12 is measured by the current sensor 35, and the measured second current value (current detection value) A2 is transmitted to the control circuit 25 of the electric water heater 18. In step #22, the water temperature sensor 26 measures the water temperature T, and the measured water temperature T is transmitted to the control circuit 25 of the electric water heater 18.

[0043] In step #23, it is confirmed whether the hot water temperature T in the hot water storage tank 21 satisfies the following conditions. Tset≦T <Tmax Here, Tset is the hot water supply setting temperature of the electric water heater 18, and Tmax is the design boiling temperature of the hot water storage tank 21.

[0044] In step #23, if the water temperature T satisfies the condition (step #23, Yes), then in step #24, it is confirmed whether the second current value (current detection value) A2 of the current sensor 35 is less than or equal to the second predetermined value S2 (e.g., 100mA). The second predetermined value S2 can be set to any value (e.g., 0 to 100mA).

[0045] In step #24, if the second current value (current detection value) A2 satisfies the condition (step #24, Yes), then in step #25, the control circuit 25 transmits a control signal (e.g., a PWM control signal) to the semiconductor switch 24, and the power consumption of the electric heater 22 is controlled in real time so that the second current value (current detection value) A2 of the current sensor 35 becomes a second predetermined value S2 (e.g., 100mA).

[0046] In step #23, if the water temperature T does not meet the conditions (step #23, No), then in step #26, it is checked whether the water temperature T meets the following conditions. T <Tset Here, Tset is the hot water setting temperature of the electric water heater 18. Therefore, in step #26, it is checked whether the water temperature T is less than the hot water setting temperature Tset.

[0047] In step #26, if the water temperature T satisfies the condition (step #26, Yes), then in step #27, the electric heater 22 is operated at its rated output. In other words, the power consumption of the electric heater 22 is not controlled by the control circuit 25.

[0048] In step #26, if the water temperature T does not satisfy the condition (step #26, No), then Tmax ≤ T will be satisfied. That is, since the water temperature T is greater than or equal to the design boiling temperature Tmax of the hot water storage tank 21, the semiconductor switch 24 is activated in step #28 to stop the electric heater 22.

[0049] In step #24, if the second current value (current detection value) A2 does not meet the condition (step #24, No), it indicates that there is a large amount of purchased electricity flowing from the commercial power supply 11 to the distribution board 12, which is necessary for controlling the power consumption of the electric heater 22 of the electric water heater 18. Depending on the fluctuations in surplus power from the power generation device 14, this could potentially cause the electric heater 22 to operate with even more purchased electricity. Therefore, in step #29, a control signal (PWM control signal) is sent from the control circuit 25 to the semiconductor switch 24 to stop the electric heater 22.

[0050] As shown in the flow diagram in Figure 3, by controlling the power consumption of the electric water heater 18 so that the current flowing from the commercial power supply 11 to the distribution board 12 (second current value A2) reaches a predetermined value (second predetermined value S2), the amount of electricity purchased from the commercial power supply 11 can be reduced. As a result, the amount of electricity purchased from the commercial power supply 11 can be minimized, and the surplus power from the power generation device 14 can be efficiently consumed by the electric water heater 18.

[0051] In another embodiment, the electric water heater 18 may be configured to include either an electric water heater or a thermos-type electric instant water heater.

[0052] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, provided that no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Explanation of Symbols]

[0053] 11:Commercial power supply 12: Switchboard 14: Power generation equipment 18: Electric water heater 21: Hot water storage tank 22: Electric heater 23: AC / DC Converter 24: Semiconductor switches 25: Control circuits 26: Water temperature sensor (temperature sensor) 31, 32, 33, 34: Power supply lines 35: Current Sensor A1: First current value (current detection value) A2: Second current value (current detection value) S1: 1st predetermined value S2: Second predetermined value T: Hot water temperature

Claims

1. A control method for an electric water heater having a hot water storage tank and connected to a distribution board together with commercial power and a power generation device, A current sensor is provided in the power supply line between the distribution panel and the commercial power supply. A control method for an electric water heater, which controls the power consumption of the electric water heater in real time based on a current detection value continuously measured by the current sensor.

2. The current sensor is configured to measure the current detection value from the distribution board to the commercial power supply, The method for controlling an electric water heater according to claim 1, wherein the power consumption of the electric water heater is controlled in real time so that the current detection value becomes a first predetermined value.

3. The current sensor is configured to measure the current detection value from the commercial power supply to the distribution panel. The method for controlling an electric water heater according to claim 1, wherein the power consumption of the electric water heater is controlled in real time so that the current detection value becomes a second predetermined value.

4. The hot water storage tank is equipped with a temperature sensor for measuring the temperature of the hot water inside the tank. A method for controlling an electric water heater according to any one of claims 1 to 3, wherein the electric water heater is operated at its rated output when the water temperature measured by the temperature sensor is below a threshold.

5. The hot water storage tank is equipped with a temperature sensor for measuring the temperature of the hot water inside the tank. A method for controlling an electric water heater according to any one of claims 1 to 3, wherein, when the water temperature measured by the temperature sensor is above a threshold, the power consumption of the electric water heater is controlled in real time based on a current detection value continuously measured by the current sensor.

6. The electric water heater comprises an AC / DC converter that converts alternating current voltage to direct current voltage, a semiconductor switch, and an electric heater that heats the hot water stored in the hot water storage tank. A control method for an electric water heater according to any one of claims 1 to 3, wherein the power consumption of the electric heater can be controlled by operating the semiconductor switch in real time based on the current detection value to adjust the DC voltage.

7. The method for controlling an electric water heater according to any one of claims 1 to 3, wherein the power generation device comprises at least one of a solar power generation device, a fuel cell, and a gas engine.

8. The method for controlling an electric water heater according to any one of claims 1 to 3, wherein the electric water heater comprises either an electric water heater or a thermos-type electric instant water heater.

9. An electric water heater having a hot water storage tank and connected to a distribution board together with commercial power and a power generation device, A current sensor is provided in the power supply line between the distribution board and the commercial power supply, The electric water heater comprises a control circuit that controls the operation of the electric water heater, The control circuit is configured to control the power consumption of the electric water heater in real time based on the current detection value continuously measured by the current sensor.

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