WO2009087811A1

WO2009087811A1 - Heat-pump hot-water supply apparatus

Info

Publication number: WO2009087811A1
Application number: PCT/JP2008/070377
Authority: WO
Inventors: Kazuhiro Endoh; Yoshikazu Koto; Takayuki Fushiki; Mitsuo Nishikori
Original assignee: Hitachi Appliances, Inc.
Priority date: 2008-01-10
Filing date: 2008-11-10
Publication date: 2009-07-16
Also published as: KR20100114022A; CN101910747A; JP2009162458A

Abstract

This aims to provide a heat-pump hot-water supply apparatus for enhancing an energy efficiency at a hot-water tank boiling time for a midnight time period and for leveling a demand for an electric power. The heat-pump hot-water supply apparatus comprises a heat pump and a hot-water tank for reserving the water heated by the heat pump. The heat-pump hot-water supply apparatus further comprises setting means for setting a heating ability by using the ambient temperature, and control means for running the heat pump preferentially at the minimum of the heating ability set for the midnight time period by the setting means. The control means exercises control to run the heat pump with a heating ability higher than the minimum, if the boil cannot be completed for the midnight time period even by the preferential run of the heat pump with the minimum heating ability.

Description

Heat pump water heater

The present invention relates to a heat pump water heater that heats water in a hot water storage tank using a heat pump.

An example of a hot water storage type heat pump water heater that heats up in the midnight hours when electricity charges are cheap is described in Patent Document 1. In order to boil up at midnight and reduce heat dissipation loss, calculate the required boiling time based on the required amount of heating and the constant heating capacity of the heat pump, and this required boiling from the end time of midnight The time when the time is subtracted is set as the boiling start time, and the boiling operation is shifted to the latter half of the midnight time.

An example of a heat pump water heater provided with other boiling control means is disclosed in Patent Document 2. This calculates the heating capacity of the inverter heat pump by (necessary amount of heat / hot water storage time), and obtains the corresponding frequency from the graph showing the relationship between the heating capacity and the frequency. Inverter heat pumps are more efficient at low frequency operation than at high frequency operation. Therefore, hot water can be stored more efficiently than when hot water is stored at a constant output.

Patent Document 3 describes an example of a heat pump water heater having a small-capacity hot water storage tank. This is mainly to drive the heat pump cycle at night to store hot water in the hot water tank, and to drive the heat pump cycle appropriately during the day to store hot water in the hot water tank. In the case where there is no fear of running out of hot water, priority is given to the operation for increasing the heating capacity. When there is no concern about running out of hot water, the operation is given priority to the operating efficiency of the heat pump cycle to prevent the hot water from running out and increase the operating efficiency. The time zone timer gives priority to the heating capacity to prevent hot water outage during the time when hot water is most needed throughout the day (16: 00-22: 00), and prioritizes operating efficiency in other time zones. ing.
JP 2004-347171 A JP-A-9-68369 JP 2005-127588 A

In the heat pump hot water supply device described in Patent Document 1, the influence of the energy efficiency of the heat pump on the change in the outside air temperature during the midnight time zone is not considered. The heat pump has a characteristic that the higher the outside air temperature, the higher the COP, which is the ratio of the water heating capacity to the power consumption of the heat pump, so-called energy efficiency. Assuming that the midnight time zone is, for example, 11:00 pm to 7:00 am, the outside air temperature changes substantially from 11:00 pm, which is the midnight time zone start time, to 7:00 am, which is the midnight time zone end time. Therefore, by shifting the boiling operation in the latter half of the midnight time zone, the heat pump is operated in the midnight time zone when the outside air temperature is low, so that there is a problem that energy efficiency (COP) is lowered.

Further, in the heat pump hot water supply apparatus described in Patent Document 2, the frequency of the heat pump to be operated is determined from a graph showing the relationship between the heating capacity and the frequency calculated by (necessary heat amount / hot water storage time). The COP of the heat pump is operated at a higher frequency when operated at a lower frequency as in the heat pump hot water supply device described in Patent Document 2 if the compressor efficiency is constant or the decrease in the compressor efficiency accompanying a decrease in frequency is small. Is more energy efficient.

Incidentally, carbon dioxide is used as a refrigerant in heat pump water heaters that have been commercialized in recent years. Carbon dioxide has a pressure difference of 3 times higher than that of fluorocarbon, 1/3 cylinder volume, and 3 times higher discharge pressure (“Non-Freon Technology” edited by Heat Pump and Thermal Storage Center, p. 50, Ohmsha, Heisei) (Issued February 1, 2016). As described above, a compressor using carbon dioxide as a refrigerant has a high differential pressure of three times as high as that of fluorocarbon. Therefore, as the frequency of the compressor decreases, the effect of leakage in the compression chamber increases. As a result, the compressor efficiency decreases greatly. Therefore, the heat pump hot water supply apparatus using carbon dioxide as a refrigerant does not have higher energy efficiency as the frequency is lower, and there is a frequency at which the energy efficiency is highest. That is, the thing of the patent document 2 does not consider the boiling-up control means when the frequency where energy efficiency becomes the highest exists.

Moreover, in the heat pump hot water supply apparatus described in Patent Document 3, the operation that prioritizes the heating capacity and the operation that prioritizes the operation efficiency are switched, but the control means for switching the operation in the midnight time zone is not considered. .

An object of the present invention is to obtain a heat pump water heater that can maintain high energy efficiency and can contribute to leveling of electric power demand.

In order to achieve the above object, the present invention provides a heat pump water heater comprising a heat pump and a hot water storage tank for storing hot water heated by the heat pump, and setting means for setting the heating capacity using the outside air temperature; Control means for preferentially operating the heat pump with a minimum value of the heating capacity set by the setting means during midnight hours, and the control means preferentially operates the heat pump with the minimum value of the heating capacity If the heating cannot be completed in the midnight time alone, the heat pump is controlled to operate with a heating capacity higher than the minimum value of the heating capacity.

According to the present invention, the priority is given to the control of operating the heat pump with the heating capacity at which the energy efficiency is substantially the highest in the predetermined time zone where the electric power demand is small in the midnight time zone where the electricity rate is low. It is possible to obtain a heat pump hot water supply device that can increase energy efficiency during boiling and contribute to leveling of power demand.
Other objects, features and advantages of the present invention will become apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.

Hereinafter, Example 1 of the heat pump hot water supply apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram of the heat pump water heater 100.

The heat pump hot water supply apparatus 100 includes a hot water storage tank unit 1 and a heat pump unit 2. The hot water storage tank unit 1 is connected to a hot water storage tank 11, a hot water discharge pipe 12 connected to the upper part of the hot water storage tank 11, a water supply pipe 13 connected to the lower part of the hot water storage tank 11, and the other of the water supply pipe 13. The water supply fitting 14 connected to the water supply outside the apparatus, the pressure reducing valve 15 for adjusting the water taken in from the water supply fitting 14 to an appropriate water pressure, the hot water from the tap water pipe 12 and the water supply pipe 13 were branched. A hot water supply mixing valve 17 for mixing low temperature water from the water supply branch pipe 16, one of the hot water supply mixing valves 17 connected downstream of the hot water supply mixing valve 17 and the other connected to a hot water supply terminal outside the apparatus, and hot water supply therebetween And a hot water supply pipe 18 including a flow rate sensor 19.

The hot water storage tank 11 is connected to the lower part of the hot water storage tank 11, the other is connected to the heat pump outlet pipe 21 connected to the heat pump unit 2, the upper part of the hot water storage tank 11, and the other is connected to the heat pump unit 2. A heat pump return pipe 22 is provided, and the hot water in the hot water storage tank 11 can be circulated through the heat pump unit 2.

A plurality of tank temperature sensors 30 provided on the side surface of the hot water storage tank 11, a water supply temperature sensor 31 provided on the water supply pipe 13, and a hot water supply temperature sensor 32 provided on the hot water supply pipe 18 detect the temperature of each part, and the temperature information is obtained. The hot water storage tank control unit 23 communicates with a heat pump control unit 58 and a remote controller (not shown), which will be described later, and controls the hot water storage tank unit 1.

The heat pump circuit 3 of the heat pump unit 2 exchanges heat between the compressor 51 that compresses the refrigerant to form a high-temperature refrigerant, and the refrigerant that has been compressed by the compressor 51 and becomes hot and the water supplied from the hot water storage tank unit 1. A water refrigerant heat exchanger 52, an expansion valve 53 for depressurizing the refrigerant that has exited the water refrigerant heat exchanger 52, and an evaporator 54 for evaporating the low-temperature and low-pressure refrigerant that has exited the expansion valve 53 are connected by a refrigerant line. Has been. Carbon dioxide is used as a refrigerant, enabling boiling of hot water.

The compressor 51 can be controlled in capacity by inverter control, and its rotation speed is variable from low speed to high speed. The evaporator 54 is an air refrigerant heat exchanger, and heat is exchanged between a large amount of outdoor air and the decompressed refrigerant by the outdoor fan 55.

The water-refrigerant heat exchanger 52 includes a refrigerant-side heat transfer tube 52a and a water-side heat transfer tube 52b, and the refrigerant flow in the refrigerant-side heat transfer tube 52a and the water flow in the water-side heat transfer tube 52b are opposed to each other. It has become. Then, the high-temperature and high-pressure refrigerant and the low-temperature water exchange heat. That is, when the water having a low temperature passes through the water-side heat transfer pipe 52b at the inlet of the water-refrigerant heat exchanger 52 (below the water-refrigerant heat exchanger 52 in the drawing), the water-refrigerant heat exchange is performed. The temperature is raised to a predetermined temperature set by a heat pump control unit 58 described later at the outlet of the vessel 52 (upper side of the water-refrigerant heat exchanger 52 in the drawing).

The inlet side of the water-side heat transfer pipe 52b of the water-refrigerant heat exchanger 52 is connected to the above-described heat pump forward pipe 21, and a tank circulation pump 56, a water-refrigerant heat exchanger, and a water flow sensor 57 capable of capacity control in the middle of the pipe. Is arranged. Further, the outlet side of the water-side heat transfer tube 52b and the heat pump return tube 22 are connected.

Compressor discharge temperature sensor 35 provided on the refrigerant pipe on the outlet side of the compressor 51, outside air temperature sensor 36 provided on the air inlet side of the evaporator 54, and water refrigerant heat exchanger water inlet provided on the heat pump forward pipe 21 The water refrigerant heat exchanger water outlet temperature sensor 38 provided in the temperature sensor 37 and the heat pump return pipe 22 detects the temperature of each part, and sends the detected temperature information to the heat pump control unit 58. The heat pump control unit 58 is described above. The hot water storage tank control unit 23 and the heat pump unit 2 are controlled.

The operation during hot water supply will be described below. When a hot water supply terminal (not shown) connected to the hot water supply fitting 20 is opened, the hot water in the upper part of the hot water storage tank 11 flows into the hot water discharge pipe 12 by the water pressure of the water supply connected to the water supply fitting 14, and the low temperature supply water is supplied. The hot water and the low temperature water flow into the branch pipe 16 and flow out of the hot water supply terminal through the hot water supply mixing valve 17, the hot water supply flow rate sensor 19, and the hot water supply fitting 20. At that time, the flow rate sensor 19 detects the water flow, and the hot water storage tank control unit 23 supplies the hot water supply temperature sensor 32 from the hot water discharge pipe 12 so that the temperature detected by the hot water supply temperature sensor 32 becomes a hot water supply temperature set by a remote controller (not shown). The ratio of the high temperature water and the low temperature water from the feed water branch pipe 16 is controlled. Since the hot water at the upper part of the hot water storage tank 11 is used, the low temperature hot water is supplied to the lower part of the hot water storage tank 11.

The operation during hot water storage will be described below. When boiling hot water in the hot water storage tank 11, the heat pump control unit 58 controls the operation of the heat pump circuit 3 and the tank circulation pump 56. At this time, as will be described later, the rotational speed control of the compressor 51, the opening degree control of the expansion valve 53, and the rotational speed control of the tank circulation pump 56 are performed. Hot water flowing out from the lower part of the hot water storage tank 11 by the operation of the tank circulation pump 56 flows into the water / refrigerant heat exchanger 52 via the heat pump forward pipe 21 and is heated by the high-temperature refrigerant in the heat pump circuit 3, and passes through the heat pump return pipe 22. The hot water is stored by being returned to the upper part of the hot water storage tank 11.

Next, the operation of midnight boiling control will be described with reference to FIGS. The midnight time zone is a time zone during which the electricity rate is reduced, for example, from 11 pm to 7 am. In the flowchart of the late-night boiling control in FIG. 2, the hot water storage tank control unit 23 starts the late-night boiling control at 11:00 pm, which is the start time of the late-night time zone (S1). First, the boiling heat quantity Qa is set (S2). The boiling heat amount Qa is calculated as the sum of the average value, standard deviation, and preliminary heat amount of heat used over the past seven days.

Calculating the amount of heat used Qc for one day (from 11:00 pm on the previous day to 11:00 pm on the same day) using the following formula.

Qc = Qz1 + Qd−Qz (Equation 1)
Here, Qz1 is the remaining heat amount of the hot water storage tank 11 at 11:00 pm on the previous day, Qd is the heating amount of the heat pump unit 2, and Qz is the remaining heat amount at 11:00 pm on that day. The residual heat amounts Qz1 and Qz are divided in the vertical direction from the temperature difference between the temperature detected by each tank temperature sensor 30 of the hot water storage tank 11 and the temperature detected by the feed water temperature sensor 31 and the hot water storage tank 11 including each tank temperature sensor 30. Calculated as the sum of the product of volume, water density and specific heat. The heating amount Qd is calculated as an integral value of the operation time of a set value (necessary heating capacity) of the heating capacity of the heat pump unit 2 described later.

The hot water storage tank control unit 23 stores the amount of heat used for the past seven days, obtains an average value and standard deviation, and considers the amount of boiling heat Qa as the sum of the average value, standard deviation, and preliminary heat amount in consideration of variations in the amount of heat used. Set. The preliminary heat amount is, for example, a heat amount capable of supplying hot water at a hot water supply temperature of 42 ° C. and a hot water supply amount of 100 L.

Next, the boiling temperature target value tp is set (S3). The boiling temperature tp is calculated by the following formula.

tp = Qa / (ρ · c · V · α) + twi (Equation 2)
However, in order to prevent Legionella bacteria generation, when the calculated boiling temperature target value tp is less than 65 ° C, the temperature is set to 65 ° C. Here, Qa is the amount of heating heat, ρ is the water density, c is the specific heat of water, V is the volume of the hot water storage tank 11, α is the volumetric efficiency, and twi is the feed water temperature detected by the feed water temperature sensor 31 in FIG. . In order to protect the heat pump circuit 3, the volumetric efficiency α stops boiling when the water inlet temperature of the water-refrigerant heat exchanger 52 is lower than the boiling temperature tp, for example, 55 ° C. This is because the raised temperature tp is not considered.

Next, the boiling time Tn is set (S4). As mentioned above, the midnight time is 8 hours from 11:00 pm to 7:00 am. The boiling time Tn is set to 5 hours, for example. The five hours are assumed to be from 1:00 am to 6:00 am during the midnight time when the power demand is reduced. This boiling time Tn may be changed according to the season (calendar), for example, in consideration of the power demand for each season.

Next, the minimum value Wmin and the maximum value Wmax of the heating capacity of the heat pump unit 2 are set (S5). 3A and 3B show the relationship between the outside air temperature and the minimum value Wmin and the maximum value Wmax of the heating capacity when the boiling temperature target value tp is 70 ° C. or higher and lower than 70 ° C., respectively. That is, the minimum value Wmin and the maximum value Wmax of the heating capacity can be determined from the boiling temperature target value tp and the outside air temperature (the detected value of the outside air temperature sensor 36). FIG. 4 shows the relationship between the heating capacity of the heat pump unit 2 and COP (ratio of heating capacity to power consumption) when the boiling temperature target value is less than 70 ° C. and the outside air temperature is ta in FIG. 3B. The heating capacity is changed mainly by changing the rotation speed (frequency) of the compressor 51. The heat pump unit 2 exhibits the characteristic that the COP has the highest value for the heating capacity. The minimum heating capacity of the heat pump unit 2 shown in FIG. 3B is the heating capacity at which the COP shown in FIG. In addition, the maximum value of the heating capacity in FIG. 3B is the heating capacity at which boiling is completed at the maximum in 8 hours in the midnight hours when there is no hot water supply in the midnight hours at each outside temperature. Therefore, in FIG. 3B, the COP is higher when operating with a small heating capacity than when operating with a large heating capacity.

Next, the required heating capacity W of the heat pump unit 2 is calculated (S6). The required heating capacity W is calculated by the following formula.

W = (Qa−Qz) / (Tn · β) (Equation 3)
Here, Qa is the above-mentioned amount of heating, Qz is the amount of residual heat at 11:00 pm on the same day, Tn is the above-mentioned boiling time, and β is the heating efficiency. The heating efficiency β is the average heating capacity of the heating pump unit 2 when the heating capacity is less than the required heating capacity W at the start-up or near the completion of the heating, or when the outside air temperature is low. The value is set according to the outside air temperature.

Next, it is determined whether the calculated required heating capacity W is within the range between the minimum value Wmin and the maximum value Wmax of the heating capacity of the heat pump unit 2 set in step S5, and necessary processing is performed for each case. Perform (S7 to S15).

If the required heating capacity W is less than the minimum heating capacity value Wmin set in step S5 (S7Y), the required heating capacity W is set to the minimum value Wmin (S8), and the boiling time Tn is reversed with the changed required heating capacity. Calculate (S9). At this time, the boiling time Tn is calculated by the following formula.

Tn = (Qa−Qz) / (W · β) (Equation 4)
By this calculation, the boiling time Tn becomes shorter than the value set in step S4, 5 hours. Therefore, it is possible to complete the boiling between 1:00 am and 6:00 am when the power demand is reduced in the midnight time zone.

Next, the end time shift time Tf is set (S10). At this time, since the boiling end time is shifted from 7:00 am in the midnight time zone to 6:00 am when the amount of power demand is small, the end time shift time Tf is set to 1 hour.

If the required heating capacity W is not less than the minimum heating capacity Wmin set in step S5 (S7N), and if it is not less than the maximum value Wmax (S11Y), the required heating capacity W is set to the maximum value Wmax (S12) and changed. On the contrary, the boiling time Tn is calculated based on the required heating capacity (S13). At this time, the boiling time Tn is calculated by the same formula as (Equation 4). By this calculation, the boiling time Tn becomes longer than the value set in step S4, 5 hours. Therefore, boiling cannot be completed only from 1 am to 6 am during the midnight hours when power demand is low, and from 6 am to 7 am otherwise. It is necessary to perform boiling operation from 11:00 pm the previous day to 1 am the next day.

Next, the end time shift time Tf is set (S14). At this time, the end time shift time Tf is set to 0 hours so that the boiling end time is not shifted and the end time of the midnight time zone is set to 7:00 am.

When the required heating capacity W is within the range of the heating capacity set in step S5 (S11N), the boiling time Tn remains at the value set in step S4, 5 hours, and the power demand in the midnight time zone. It is possible to complete the boiling between 1 am and 6 am when the amount of water is reduced.

At this time, the end time shift time Tf is set (S15). In order to shift the boiling end time from 7:00 am in the midnight time zone to 6:00 am in which the amount of power demand is small, the end time shift time Tf is set to 1 hour.

As described above, after the boiling time Tn and the required heating capacity W are determined in steps S7 to S15, the boiling start time Ts is set (S16). The boiling start time Ts is calculated by the following formula.

Ts = midnight time end time−Tf−Tn (Equation 5)
Here, Tf is the aforementioned end time shift time, and Tn is the boiling time. The end time of the midnight time zone is 7:00 am.

Next, it is determined whether the current time has reached the boiling start time Ts (S17). When the current time reaches the boiling start time Ts (S17Y), the heat pump is operated (S18). When the current time does not reach the boiling start time Ts (S17N), the determination in step S17 is repeated. .

The heat pump operation (S18) is performed as follows. At this time, the hot water storage tank control unit 23 issues a heat pump operation command to the heat pump control unit 58, and gives the boiling temperature target value tp and the required heating capacity W. The heat pump control unit 58 controls the rotation speed of the compressor 51 so that the water outlet temperature detected by the water outlet temperature sensor 38 of the water refrigerant heat exchanger 52 becomes the boiling temperature target value tp.

Further, the heat pump control unit 58 controls the opening degree of the expansion valve 53 so that the discharge temperature detected by the compressor discharge temperature sensor 35 becomes a target value td0 calculated by the following equation.

Td0 = f (tp, thwi, ta, W) (Equation 6)
Here, tp is the boiling temperature target value, thwi is the water inlet temperature detected by the water inlet temperature sensor 37 of the water refrigerant heat exchanger 52, ta is the outside air temperature detected by the outside air temperature sensor 36, and W is the required heating capacity. The target value td0 of the discharge temperature is expressed by these functions f. The target value is set to a discharge temperature at which the COP of the heat pump unit 2 is substantially maximum. Here, since the target value is a function of the required heating capacity W, a highly efficient heat pump can be operated in the entire range of the minimum value Wmin and the maximum value Wmax of the heating capacity shown in FIG. 3B.

Further, the heat pump control unit 58 controls the rotational speed of the tank circulation pump 56 so that the water flow rate detected by the water flow rate sensor 57 of the water refrigerant heat exchanger 52 becomes the target value Lw0 calculated by the following equation.

Lw0 = W / ((ρ · c) (tp−thwi)) (Equation 7)
Here, W is the required heating capacity, ρ is the water density, c is the specific heat of water, tp is the boiling temperature target value, and thwi is the water inlet temperature detected by the water inlet temperature sensor 37 of the water refrigerant heat exchanger 52.

The heat pump control unit 58 performs a heating operation with a boiling temperature of tp and a heating capacity of W by controlling the rotation speed control of the compressor 51 and the rotation speed control of the tank circulation pump 56 described above.

During the heat pump operation, the hot water storage tank control unit 23 determines whether or not the predetermined tank temperature sensor 30 is equal to or higher than a preset boiling end temperature (S19). If it is not higher than the boiling end temperature (S19N), the determination in step S19 is repeated. If the boiling end temperature is reached (S19Y), the hot water storage tank control unit 23 issues a heat pump stop command to the heat pump control unit 58 (S20), and completes the midnight boiling (S21). In order to calculate the heating amount Qd, the time integration of the required heating capacity W is calculated during the heat pump operation.

As described in detail above, the midnight boiling operation is divided into three patterns (see FIGS. 5A to 5C). That is, in the first (FIG. 5A), the efficiency of the heat pump is reduced in a predetermined time zone (from 1 am to 6 am) in which the power demand is smaller in the late-night time zone (from 11 pm to 7 am). This is a pattern in which the heat pump is operated at a heating capacity that is substantially the highest. At this time, the time obtained by subtracting the required boiling time from the predetermined time zone end time (6:00 am) is set as the boiling start time, and the boiling operation is shifted to the latter half of the predetermined time zone.

The second (FIG. 5B) is a case where boiling cannot be completed in a predetermined time zone only by operation with the heating capacity with the highest efficiency. This is to operate the heat pump with a heating capacity higher than the heating capacity at which the efficiency of the heat pump is substantially maximum so that boiling is completed in a predetermined time period. At this time, the heat pump is operated with a heating capacity in which boiling is completed using substantially the entire time of a predetermined time zone (from 1 am to 6 am).

3rd (FIG. 5C) is a case where boiling cannot be completed within a predetermined time zone even if it is operated at the maximum heating capacity. The heat pump is operated at the maximum heating capacity so that boiling is completed at midnight. At this time, a time obtained by subtracting the required boiling time from the midnight time zone end time (7:00 am) is set as a boiling start time, and the heating operation is shifted to the latter half of the midnight time zone.

In the present embodiment, it has been described that the boiling is completed at the predetermined time zone end time or the midnight time zone end time. However, for example, the heating of the heat pump is performed so that the boiling is completed with a margin before this time. The capacity may be reset to be slightly larger so that the operation time is slightly shorter.

The first operation pattern allows the heat pump to operate at a high efficiency because the heat pump is operated with a heating capacity at which the efficiency of the heat pump is substantially the highest.

In addition, since the heat pump is operated for a long time with a small heating capacity according to the first and second operation patterns, the heat pump boiling operation start time is advanced, and the operation time in the time zone when the outside air temperature is high in the operation midnight time zone The heat pump can be operated under the condition that the energy efficiency is increased.

In addition, since the heat pump operation is performed within a predetermined time period from 1 am to 6 am in which the power demand is reduced in the midnight time zone according to the first and second operation patterns, Can contribute to

Also, with the third operation pattern, boiling can be completed reliably in the midnight hours even when the amount of boiling heat is large.

Embodiment 2 of the present invention will be described with reference to FIG. The present embodiment differs from the first embodiment in the heat pump operation in step S18 of the midnight boiling control flowchart shown in FIG. In this embodiment, the heating capacity of the heat pump is set at regular intervals.

The hot water storage tank control unit 23 starts the heating capacity resetting control during the heat pump operation (S30). If the current heating capacity is less than the maximum value Wmax (S31Y), the heating capacity is reset. If the current heating capacity is the maximum value Wmax (S31N), the control is terminated without resetting the heating capacity (S32). That is, when the heat pump operation is performed within a predetermined time period from 1 am to 6 am, the heating capacity is reset.

To reset the heating capacity, first, the current heat quantity Qx is calculated (S33). The current amount of heat Qx is the temperature difference between the temperature detected by each tank temperature sensor 30 of the hot water storage tank 11 and the temperature detected by the feed water temperature sensor 31, and the volume of the hot water storage tank 11 including each tank temperature sensor 30 divided vertically. Calculated as the sum of the product of water density and specific heat.

Next, the remaining boiling time Tr is calculated (S34). The remaining boiling time Tr is calculated by the following formula.

Tr = Midnight time end time-Tf-current time (Equation 8)
Here, the end time of the midnight time zone is 7:00 am, and Tf is the end time shift time, which is one hour set in step S10 or S15 in FIG.

Next, the minimum value Wmin and the maximum value Wmax of the heating capacity of the heat pump unit 2 are set (S35). The setting method is the same as step S5 in FIG.

Next, the required heating capacity W of the heat pump unit 2 is calculated (S36). The required heating capacity W is calculated by the following formula.

W = (Qa−Qx) / (Tr · β) (Equation 9)
Here, Qa is the amount of heating heat described in the first embodiment, Qx is the above-described current heat amount, Tr is the above-described remaining heating time, and β is the heating efficiency described in the first embodiment.

Next, it is determined whether the calculated required heating capacity W is within the range between the minimum value Wmin and the maximum value Wmax of the heating capacity of the heat pump unit 2 set in step S35. Perform (S37 to S40). If the required heating capacity W is less than the minimum heating capacity Wmin set in step S35 (S37Y), the required heating capacity W is set to the minimum value Wmin (S38). If the required heating capacity W is greater than the maximum value Wmax (S39Y), the required heating capacity W is set to the maximum value Wmax (S40). In the case of step S39Y, since the required heating capacity is suppressed at the maximum value Wmax, boiling is not completed by 6 am of the predetermined time zone end time, but the excess time is small and the midnight time zone end time is reached. The boiling is completed by 7 am.

Next, the required heating capacity W is reset (S41). At this time, the hot water storage tank control unit 23 gives a new value of the required heating capacity W to the heat pump control unit 58. The heat pump control unit controls the operation of the heat pump unit 2 based on the new value of the required heating capacity W.

The hot water storage tank control unit 23 performs the above reset control of the heating capacity every time the timer elapses (S42).

As described above, by finely setting the heating capacity of the heat pump at regular intervals, the heat pump water heater can be made as small as possible within a predetermined time zone from 1:00 am to 6:00 am when the power demand is reduced in the midnight time zone. It is possible to operate with high efficiency by heating capacity. Moreover, boiling can be completed reliably within a predetermined time zone.

Embodiment 3 of the present invention will be described with reference to FIG. In the present embodiment, the boiling time Tn is changed from 5 hours to 8 hours in the late-night boiling control of the first embodiment. In FIG. 7, the same steps as those in FIG.

Steps S1 to S3 are the same as those in the first embodiment. The boiling time Tn in step S4 ′ is set to 8 hours in the midnight time zone (from 11 pm to 7 am). In step S6, the required heating capacity W is calculated by setting the boiling time Tn to 8 hours.

In step S7 ′, if the required heating capacity W is less than the minimum heating capacity Wmin set in step S5 (S7′Y), the required heating capacity W is set to the minimum value Wmin (S8), and the changed required heating capacity is Conversely, the boiling time Tn is calculated (S9).

In other cases (S7′N), it is assumed that the required heating capacity W is within the heating capacity set in step S5, and the value is used as it is. In addition, as described in Example 1, the maximum value Wmax of the heating capacity in FIG. 3 is completed at the maximum of 8 hours in the midnight time zone when there is no hot water supply in the midnight time zone at each external temperature. Since the heating capacity is set, the required heating capacity W is a value equal to or less than the maximum value Wmax.

The subsequent steps S16 to S21 are the same as those in the first embodiment.

As described above, by setting the heating time of the heat pump to 8 hours longer than 5 hours, the heat pump water heater can be operated with a smaller heating capacity for the same required boiling heat quantity, and high efficiency can be maintained. Can do.

Example 4 of the present invention will be described. In the present embodiment, the heat pump operation in step S18 in the flowchart of the late-night boiling control shown in FIG. 7 is different from the above-described third embodiment. In this embodiment, the heating capacity required for the heat pump multiplied by the coefficient k is used as the heating capacity for operating the heat pump.

Calculate the coefficient k using the following formula.

k = 1 + d-2d / Tn * T (Equation 10)
Here, d is a shift value, Tn is a boiling time of 8 hours, and T is a heat pump operation time. The coefficient k is a linear function of the operation time T. When T = 0, k = 1 + d, and when T = Tn, k = 1−d. That is, by multiplying the required heating capacity W by the coefficient k, the heating capacity of the heat pump becomes larger than the required heating capacity W in the first half of the midnight time zone, and becomes smaller than the required heating capacity W in the second half. In addition, when boiling is performed in 8 hours (in the case of step S7′N in FIG. 7), this control process is performed. The heating capacity of the heat pump is set within the range from the minimum value Wmin to the maximum value Wmax set in FIG.

With the above control, more than half of the late-night boiling heat quantity is boiled in the first half of the midnight time zone, so that it can be operated under the condition that the energy efficiency of the first half in which the outside air temperature is high in the midnight time zone is high. High efficiency can be maintained.

Example 5 of the present invention will be described. The present embodiment is different from the third embodiment in the setting method of the heating capacity minimum value Wmin in step S5 of the flowchart in the late-night boiling control of FIG. In the present embodiment, the heating capacity minimum value Wmin of the heat pump is set to approximately two thirds of the heating capacity maximum value Wmax.

8A and 8B show the relationship between the outside air temperature and the minimum value and the maximum value of the heating capacity of the heat pump unit 2 when the boiling temperature target value in this embodiment is 70 ° C. or higher and lower than 70 ° C., respectively. The minimum value Wmin of the heating capacity is set to approximately two thirds (66%) of the maximum value Wmax, which is larger than the minimum value Wmin indicating the heating capacity at which the efficiency of the heat pump shown in FIG. 3A and FIG. ). At this time, in the range of 66% to 100% of the maximum heating capacity of the heat pump, the energy efficiency increases as the heating capacity decreases.

With this control process, the heat pump unit 2 is operated at a boiling rate of 66% to 100% of the maximum heating capacity at midnight, and at least operates at 66% of the maximum heating capacity. The boiling time Tn calculated in step S9 in the flowchart of FIG. 7 is reduced, and therefore the boiling start time Ts calculated in S16 is shifted backward in the midnight time zone.

With the above control, it is possible to maintain high energy efficiency and to suppress an increase in the amount of power in the first half where the power demand is high during midnight hours.

In this embodiment, the heating capacity minimum value Wmin of the heat pump is set to approximately two thirds of the heating capacity maximum value Wmax, but the same effect can be obtained when the heating capacity is set to 50% to 80%.

In the above-mentioned embodiment, the time zone in which the electricity rate is reduced as the midnight time zone is used, but the present invention can be similarly applied to the time zone in which the hot water supply demand or the power demand is small.

Further, in the above embodiment, in order to obtain the required heating capacity, the rotation speed control of the compressor is performed so that the boiling temperature becomes the target value, and the rotation speed control of the tank circulation pump is controlled so that the water amount becomes the target value. However, from the relationship between the heating capacity and the compressor rotational speed, the rotational speed may be set, and the rotational speed of the tank circulation pump may be controlled so that the boiling temperature becomes the target value. Any control method can be used as long as the required heating capacity can be obtained.

According to the present invention, priority is given to the control of operating the heat pump with the heating capacity at which the energy efficiency is substantially the highest in the predetermined time zone, so the energy efficiency during the tank boiling operation of the heat pump water heater increases.
While the above description has been made with reference to exemplary embodiments, it will be apparent to those skilled in the art that the invention is not limited thereto and that various changes and modifications can be made within the spirit of the invention and the scope of the appended claims.

The systematic diagram of the heat pump hot-water supply apparatus which concerns on Example 1 of this invention. The flowchart which shows the midnight boiling control which concerns on Example 1 of this invention. The diagram which shows the relationship between the external temperature in case the boiling temperature target value in Example 1 of this invention is 70 degreeC or more, and the minimum value and the maximum value of the heating capability of a heat pump unit. The diagram which shows the relationship between the external temperature in case the boiling temperature target value in Example 1 of this invention is less than 70 degreeC, and the minimum value of heating capacity of a heat pump unit, and a maximum value. The diagram which shows the relationship between the heating capability of the heat pump unit in Example 1 of this invention, and COP. The figure which shows the time of the heat pump driving | operation in Example 1 of this invention. The figure which shows the time of the heat pump driving | operation in Example 1 of this invention. The figure which shows the time of the heat pump driving | operation in Example 1 of this invention. The flowchart which shows the heating capability reset control of the heat pump unit in Example 2 of this invention. The flowchart which shows the midnight boiling control in Example 3 of this invention. The diagram which shows the relationship between the minimum value and the maximum value of the outside temperature in case the boiling temperature target value in Example 5 of this invention is 70 degreeC or more, and the heating capability of a heat pump unit. The diagram which shows the relationship between the outside temperature in case the boiling temperature target value in Example 5 of this invention is less than 70 degreeC, and the minimum value and the maximum value of the heating capability of a heat pump unit.

Claims

A heat pump,
In a heat pump water heater comprising a hot water storage tank for storing hot water heated by the heat pump,
Setting means for setting the heating capacity using the outside air temperature, and control means for preferentially operating the heat pump with the heating capacity at which the energy efficiency of the heat pump is substantially maximized in the midnight hours,
When the heating means is not able to complete boiling in the midnight time zone only by preferentially operating the heat pump with a heating capacity at which the energy efficiency of the heat pump is substantially maximized, the energy efficiency is substantially reduced. A heat pump hot water supply apparatus, wherein the heat pump is controlled to operate with a heating capacity higher than a maximum heating capacity.
A heat pump,
In a heat pump water heater comprising a hot water storage tank for storing hot water heated by the heat pump,
Setting means for setting the heating capacity using the outside air temperature;
Control means for preferentially operating the heat pump at the minimum value of the heating capacity set by the setting means during midnight hours,
The control means operates the heat pump with a heating capacity higher than the minimum heating capacity when the heating pump cannot be completed in the midnight time zone simply by operating the heat pump preferentially with the minimum heating capacity. The heat pump hot water supply apparatus characterized by controlling so that it may be made.
3. The heat pump hot water supply apparatus according to claim 2, wherein the control means includes setting means for setting a minimum value of the heating capacity to a heating capacity at which the energy efficiency is substantially maximized.
3. The heat pump hot water supply apparatus according to claim 2, wherein the control means includes setting means for setting the minimum value of the heating capacity to a heating capacity larger than the heating capacity at which the energy efficiency is substantially maximum.
3. The heat pump hot water supply apparatus according to claim 2, wherein the minimum value of the heating capacity is set to 50 to 80% of the maximum value of the heating capacity.
3. The heat pump hot water supply apparatus according to claim 2, wherein the control device performs control so as to boil more than half of the total amount of heating heat in the midnight time zone in the first half of the midnight time zone.
A heat pump,
In a heat pump water heater comprising a hot water storage tank for storing hot water heated by the heat pump,
Setting means for setting the heating capacity using the outside air temperature;
Control means for preferentially operating the heat pump with a heating capacity at which the energy efficiency of the heat pump is substantially maximized in a predetermined time zone of a midnight time zone;
When the heating cannot be completed in the predetermined time period only by the operation at which the energy efficiency of the heat pump is substantially highest, the heat pump is operated with a heating capability higher than the heating capability at which the energy efficiency is substantially highest. Control means;
Control means for operating the heat pump also in the midnight time zone when the heating cannot be completed in the predetermined time zone even when the operation is performed with the maximum value of the heating capacity set by the setting means. Heat pump water heater.
The control means according to claim 7, wherein when the boiling cannot be completed in the predetermined time period, the heat pump is operated with a heating capacity larger than the heating capacity at which the energy efficiency is substantially highest in the midnight time period. A heat pump hot water supply apparatus comprising:
8. The heat pump hot water supply apparatus according to claim 7, further comprising control means for operating the heat pump at a maximum heating capacity in the midnight time zone when boiling cannot be completed in the predetermined time zone.
2. The heat pump hot water supply apparatus according to claim 1, further comprising setting means for setting the heating capacity of the heat pump at regular intervals within a midnight time zone.
2. A heat pump hot water supply apparatus according to claim 1, comprising a hot water storage tank control section and a heat pump control section to which a command for heating capacity is transmitted from the hot water storage tank control section.
2. The heat pump water heater according to claim 1, wherein carbon dioxide is used as a refrigerant of the heat pump.