JP7601182B2 - Hot water production system - Google Patents

Description

The present invention relates to a hot water production system.

Conventionally, hot water production systems are known. For example, Patent Document 1 shows a system that uses a heat pump to produce hot water for hot water cleaning or hot water sterilization of workpieces such as food.

JP 2009-133522 A

Currently, many factories and businesses are working on "decarbonization" to move away from fossil fuels in order to reduce emissions of _CO2, a typical greenhouse gas. Therefore, as shown in Patent Document 1, systems using heat pumps are increasingly being adopted as systems for producing hot water. However, heat pumps have the characteristic that, if the hot water outlet temperature is low, the COP (coefficient of performance) is high and the effect of reducing _CO2 emissions is also high, but if the hot water outlet temperature is increased, the COP becomes low and the effect of reducing _CO2 emissions also decreases. In addition, if the hot water outlet temperature is increased, the running costs also increase because the COP is low.

The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a hot water production system that is highly effective in reducing _CO2 emissions and can reduce running costs even when the outlet hot water temperature is increased.

The present invention provides a water heater comprising: a first heating means (e.g., first heating means 2) for heating water to a target hot water supply temperature while passing the water through a heat pump water heater (e.g., a water heater of a heat pump water heater system 10); a second heating means (e.g., second heating means 3) for indirect heat exchange between the water heated to the target hot water supply temperature by the first heating means and steam generated by a steam boiler (e.g., a steam boiler device 30) and adjusted to a target steam pressure, and for raising the temperature of the water to a target hot water outlet temperature that is set higher than the target hot water supply temperature; and a control means for controlling the first heating means and the second heating means. The second heating means includes a heating heat exchanger (e.g., heating heat exchanger 210, second heating heat exchanger 220) that indirectly exchanges heat between the hot water heated by the water heater and the steam generated in the steam boiler, a hot water tank (e.g., hot water tank 40) that stores the hot water heated by the heating heat exchanger, and a hot water storage temperature sensor (e.g., hot water storage temperature sensor 41) that detects the temperature of the hot water in the hot water tank, and the control means relates to a hot water production system that adjusts the output sharing between the water heater and the steam boiler so that the detected temperature of the hot water storage temperature sensor becomes the set target hot water outlet temperature.

In addition, it is preferable that the second heating means has a steam header (e.g., steam header 51) that collects steam generated in the steam boiler, and a heating steam supply valve (e.g., heating steam supply valve 54) that adjusts the amount of steam supplied from the steam header, and that the control means has a boiler control unit (e.g., boiler control unit 120) that controls the steam boiler so that the header pressure of the steam header becomes the target steam pressure, and a steam supply control unit (e.g., steam supply control unit 130) that controls the heating steam supply valve so that the detected temperature of the hot water temperature sensor becomes the set target hot water outlet temperature.

The second heating means includes a first water level sensor (e.g., first water level sensor 42) that detects the water level in the hot water tank, a heating steam supply line (e.g., heating steam supply line L2) that supplies steam generated by the steam boiler to the heating heat exchanger, and a heating steam supply valve (e.g., heating steam supply valve 54) provided in the heating steam supply line, and the first heating means includes a water supply line that supplies water to the water heater, a hot water supply line that supplies hot water heated by the water heater to the heating heat exchanger, and a hot water supply temperature sensor that detects the hot water supply temperature of the hot water circulating through the hot water supply line, and the control means detects a water level in the hot water tank when the water level in the hot water tank drops. When the water level detected by the first water level sensor falls below a first set water level, the supply of service water via the water supply line and the supply of hot water via the hot water supply line are started, and when the water level detected by the first water level sensor rises above a second set water level that is higher than the first set water level, the supply of service water via the water supply line and the supply of hot water via the hot water supply line are stopped, and when the supply of service water is being performed, it is preferable to control the water heater so that the temperature detected by the hot water supply temperature sensor becomes the target hot water supply temperature, and to control the opening of the heating steam valve so that the temperature detected by the hot water storage temperature sensor becomes the target hot water outlet temperature.

The system further includes a bypass water supply line (e.g., bypass water supply line L5) that supplies water to the hot water tank without passing through the water heater, a bypass water supply valve (e.g., bypass water supply valve 62) provided on the bypass water supply line, a backup steam supply line (e.g., backup steam supply line L12) that supplies steam generated by the steam boiler to the hot water tank, and a backup steam supply valve (e.g., backup steam supply valve 212) provided on the backup steam supply line, and the control means preferably opens the bypass water supply valve when the water level detected by the first water level sensor falls below a third set water level that is lower than the first set water level when the water level in the hot water tank falls, and controls the opening of the heating steam supply valve and the backup steam supply valve so that the temperature detected by the hot water storage temperature sensor becomes the target hot water outlet temperature, and closes the bypass water supply valve when the water level detected by the first water level sensor exceeds a fourth set water level that is higher than the third set water level when the water level in the hot water tank rises.

Furthermore, it is preferable that the temperature zone for controlling the opening degree of the backup steam supply valve is a lower temperature zone than the temperature zone for controlling the opening degree of the heating steam supply valve.

The system further includes a bypass water supply line that supplies water to the hot water tank without passing through the water heater, a bypass water supply valve provided on the bypass water supply line, a circulation line (e.g., stored water circulation line L13) through which the hot water stored in the hot water tank is circulated, an auxiliary heat exchanger that performs indirect heat exchange between the hot water flowing through the circulation line and steam, and a return temperature sensor (e.g., return temperature sensor 222) that detects the temperature of the hot water returning from the auxiliary heat exchanger to the hot water tank. The heating steam supply line is connected to the heating heat exchanger and the auxiliary heat exchanger. Steam generated by the steam boiler is supplied to the auxiliary heat exchanger, and the control means opens the bypass water supply valve when the water level detected by the first water level sensor falls below a third set water level that is lower than the first set water level when the water level in the hot water tank falls, and controls the opening of the heating steam supply valve so that the temperature detected by the return temperature sensor becomes the target hot water outlet temperature, and preferably closes the bypass water supply valve when the water level detected by the first water level sensor exceeds a fourth set water level that is higher than the third set water level when the water level in the hot water tank rises.

In addition, it is preferable that the heating steam supply line circulates the steam generated in the steam boiler through the auxiliary heat exchanger, and then through the heating heat exchanger.

In addition, a bypass water supply line that supplies water to the hot water tank without passing through the water heater, a bypass water supply valve provided on the bypass water supply line, a preheating heat exchanger (e.g., preheating heat exchanger 75) that indirectly exchanges heat between the water flowing through the bypass water supply line and steam, a preheating steam supply line (e.g., preheating steam supply line L10) that supplies steam generated by the steam boiler to the preheating heat exchanger, and a preheating steam supply valve provided on the preheating steam supply line. and a steam valve (e.g., a preheating steam supply valve 76), and the control means preferably opens the bypass water supply valve and the preheating steam supply valve when the water level detected by the first water level sensor falls below a third set water level that is lower than the first set water level when the water level in the hot water tank falls, and closes the bypass water supply valve when the water level detected by the first water level sensor rises above a fourth set water level that is higher than the third set water level when the water level in the hot water tank rises.

Furthermore, it is preferable that the first heating means includes a plurality of the water heaters (e.g., water heaters 11, 12, 13), the hot water tank is set with a plurality of water level thresholds for changing the number of the water heaters in operation, and the control means executes a number control to increase the number of the water heaters in operation by one each time the water level detected by the first water level sensor falls below the water level threshold by one step when the water level in the hot water tank falls, and executes a number control to decrease the number of the water heaters in operation by one each time the water level detected by the first water level sensor rises above the water level threshold by one step when the water level in the hot water tank rises.

Further, the first heating means includes a plurality of the water heaters (e.g., water heaters 11, 12, 13), the hot water tank is set with a plurality of water level thresholds for changing the number of the water heaters in operation and/or the target hot water temperature, the water heaters are capable of switching between a plurality of target hot water temperatures in a temperature range higher than a first temperature and lower than the target hot water outlet temperature, and the control means executes control to raise the target hot water temperature of the water heater by one step while maintaining the number of the water heaters in operation when the water level detected by the first water level sensor exceeds the water level threshold by one step during operation with the target hot water temperature of the water heater set to the first temperature, and executes control to raise the target hot water temperature of the water heater by one step while maintaining the number of the water heaters in operation when the water level detected by the first water level sensor exceeds the water level threshold by one step during operation with the target hot water temperature of the water heater increased by one step or more. and, while decreasing the number of operating water heaters by one, control is executed to return the target hot water temperature to the first temperature, or while maintaining the number of operating water heaters, control is executed to further increase the target hot water temperature of the water heater by one step, and while operating with the target hot water temperature of the water heater set to the first temperature, when the water level detected by the first water level sensor falls one step below the water level threshold, control is executed to increase the number of operating water heaters by one and simultaneously increase the target hot water temperature of the water heater by one or more steps, and while operating with the target hot water temperature of the water heater increased by one or more steps, when the water level detected by the first water level sensor falls one step below the water level threshold, control is executed to decrease the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters.

It is also preferable to provide a water supply tank (e.g., water supply tank 60) for storing water to be supplied to the water heater and/or water to be supplied to the steam boiler, and a switching means (e.g., switching means 80) for switching the destination of the hot water supplied from the water heater to the hot water tank or the water supply tank.

Furthermore, it is preferable that the first heating means includes a plurality of the water heaters (e.g., water heaters 11, 12, 13), the hot water tank is set with a plurality of water level thresholds for changing the number of hot water heaters, and the control means controls the switching means to increase the number of hot water heaters for the hot water tank by one each time the water level detected by the first water level sensor falls below the water level threshold by one step when the water level in the hot water tank falls, and to simultaneously decrease the number of hot water heaters for the water supply tank by one each time, and to control the switching means to decrease the number of hot water heaters for the hot water tank by one each time the water level detected by the first water level sensor exceeds the water level threshold by one step when the water level in the hot water tank rises, and to simultaneously increase the number of hot water heaters for the water supply tank by one each time.

It is also preferable to provide a second water level sensor that detects the water level of the water supply tank, and the control means stops the water heater that is supplying hot water to the water supply tank when the water level detected by the second water level sensor reaches the water supply stop water level, and operates the water heater that is stopped when the detected water level reaches the water supply start water level.

It is also preferable to provide a water supply tank for storing water to be supplied to the water heater and/or water to be supplied to the steam boiler, and a drain recovery line for recovering steam drain generated in the heating heat exchanger in the water supply tank.

The present invention also relates to a hot water production method including a first heating step of heating water to a target hot water temperature while flowing it through a heat pump water heater, and a second heating step of indirectly exchanging the water heated to the target hot water temperature in the first heating step with steam generated in a steam boiler, the steam being adjusted to a target steam pressure, to heat the water to a target hot water outlet temperature that is set higher than the target hot water temperature , wherein the second heating step indirectly heat exchanges the hot water heated by the water heater with the steam generated in the steam boiler in a heating heat exchanger, stores the heated water in a hot water tank, detects the temperature of the hot water in the hot water tank with a hot water storage temperature sensor, and adjusts the output share of the water heater and the steam boiler so that the detected temperature of the hot water storage temperature sensor becomes the set target hot water outlet temperature when the first heating step and the second heating step are performed.

According to the present invention, it is possible to provide a hot water producing system that is highly effective in reducing CO ₂ emissions and is also capable of reducing running costs, even when the outlet hot water temperature is increased.

1 is a schematic diagram showing a hot water producing system according to a first embodiment of the present invention; FIG. 2 is a diagram showing a heat pump circuit of the water heater of the embodiment. FIG. 2 is a functional block diagram showing a configuration of a control unit in the embodiment. FIG. 4 is a schematic diagram for explaining the hot water storage control of the embodiment. A diagram showing the number of operating water heaters and the total amount of make-up water in the hot water storage control of the above embodiment. FIG. 6 is a diagram showing a modified example of the hot water storage control shown in FIG. 5 . FIG. 1 is a schematic diagram showing a first comparative example in which a hot water production system is constructed using only steam from a steam boiler device as a heating means. FIG. 11 is a schematic diagram showing a second comparative example in which a hot water production system is constructed using only a heat pump hot water supply system as a heating means. FIG. 2 is a schematic diagram showing the hot water producing system of the embodiment. 6 is a graph showing the effects of the above embodiment. FIG. 4 is a schematic diagram showing a hot water producing system according to a second embodiment of the present invention. FIG. 11 is a schematic diagram showing a hot water producing system according to a third embodiment of the present invention. FIG. 11 is a schematic diagram showing a hot water producing system according to a fourth embodiment of the present invention. FIG. 13 is a schematic diagram showing a hot water producing system according to a fifth embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the contents of the hot water temperature control in the embodiment.

First Embodiment
Hereinafter, a hot water producing system 1 according to a first embodiment of the present invention will be described with reference to the drawings. In this specification, the term "line" is a general term for a line, such as a flow path, a pathway, or a pipe, through which a fluid can flow.

FIG. 1 is a schematic diagram showing a hot water producing system 1 of the present embodiment.
The hot water production system 1 of this embodiment comprises a first heating means 2 that heats water W1 to a first temperature by flowing it through (passing it once) through a condenser of a heat pump water heater, and a second heating means 3 that indirectly exchanges heat with the water W1 heated by the first heating means 2 and steam S generated in a steam boiler to heat the water W1 to a second temperature higher than the first temperature.

The first heating means 2 is composed of a heat pump type hot water system 10 and includes a plurality of heat pump type hot water heaters, in this embodiment, a first heat pump type hot water heater 11, a second heat pump type hot water heater 12, and a third heat pump type hot water heater 13 (hereinafter also referred to as the first hot water heater 11, the second hot water heater 12, and the third hot water heater 13). Each of the heat pump type hot water heaters 11, 12, and 13 (hereinafter also referred to as the hot water heaters 11, 12, and 13) preferably has an electrically driven refrigerant compressor, and heats the water W1 supplied from a water supply tank 60 described below to a first temperature, for example, 50 to 70°C, by circulating it through the condenser of the heat pump type hot water system 10.

Here, the multiple water heaters 11, 12, 13 all have the same configuration, and each of the water heaters has a heat pump circuit 90. Therefore, the heat pump circuit 90 of the first water heater 11 will be described as a representative of these.
2, the heat pump circuit 90 of the first hot water heater 11 includes a refrigerant compressor 91, a condenser 92, an expansion valve 93, and an evaporator 94. The refrigerant compressor 91, the condenser 92, the expansion valve 93, and the evaporator 94 are connected in sequence in a ring shape by a refrigerant circulation line L7, thereby forming the heat pump circuit 90.

The electrically driven refrigerant compressor 91 has a motor 95 as a drive source, and compresses gaseous refrigerant R such as fluorocarbon gas into a high-temperature, high-pressure refrigerant. The condenser 92 condenses and liquefies the refrigerant R from the refrigerant compressor 91. The expansion valve 93 reduces the pressure and temperature of the refrigerant R by passing the refrigerant R sent from the condenser 92. The evaporator 94 evaporates the refrigerant R sent from the expansion valve 93 using the heat source water W8 sent through the heat source water supply line L8 as a heat source. Note that the heat source water supply line L8 is not shown in FIG. 1.

The heat source for the heat pump circuit 90 is not limited to heat source water such as waste hot water, but various heat source gases can be used, such as exhaust gas (combustion gas, exhaust steam, etc.) from factory equipment, cooling air containing waste heat, and outside air not containing waste heat.
In the case where the evaporator is structured such that the heat transfer surface is exposed to the outside, the heat source gas is supplied to the heat transfer surface by a fan (e.g., air ventilation). In the case where the evaporator is structured such that the heat transfer surface is present in a closed space (e.g., a shell), the heat source gas is supplied to the heat transfer surface by a blower.

In this way, in the heat pump circuit 90 of the first water heater 11, the refrigerant R absorbs heat from the outside and vaporizes in the evaporator 94, while the refrigerant R radiates heat to the outside and condenses in the condenser 92. Using this principle, the heat pump circuit 90 of the first water heater 11 pumps heat from the heat source water W8 in the evaporator 94, and heats the water W1 from the heat pump water supply line L3 in the condenser 92. The water W1, which has been heated by passing through the condenser 92 and turned into hot water, is then supplied to the second heating means 3 through the hot water supply line L1.

In addition, in the heat pump circuit 90 of the first hot water heater 11, the opening degree of the expansion valve 93 is adjusted so that the degree of superheating of the refrigerant R (the inlet refrigerant temperature of the refrigerant compressor 91) is constant, or the degree of subcooling of the refrigerant R (the inlet refrigerant temperature of the expansion valve 93) is constant.

The heat pump circuit 90 of the first hot water heater 11 may be configured so that its output can be changed. For example, the rotation speed of the motor 95 of the refrigerant compressor 91 may be changed by inverter control.

As shown in FIG. 1, each water heater 11, 12, 13 is provided with a water supply temperature sensor 14, 15, 16 that detects the water supply temperature from each water heater 11, 12, 13. Note that the water supply temperature sensor 14, 15, 16 may be provided in the water heater 11, 12, 13, or may be provided in the water supply line L1 downstream of the water heater 11, 12, 13 before the junction.

The hot water W1 (hereafter also referred to as hot water W1) that has been heated by multiple water heaters 11, 12, and 13 is merged into hot water by the hot water supply line L1, and is then further heated by the second heating means 3 and supplied to the hot water tank 40 described below.

Next, a description will be given of the second heating means 3. The second heating means 3 includes a steam boiler device 30, a heating heat exchanger 210, and a heating steam supply line L2 that supplies the steam S generated by the steam boiler device 30 to the heating heat exchanger 210.
The steam boiler device 30 is preferably a steam boiler having a gas-fired or oil-fired burner, and is composed of, for example, a plurality of once-through boilers 31 that generate steam S.
The second heating means 3 uses steam S generated by the steam boiler device 30 to raise the temperature of the water W1 heated by the first heating means 2 to a second temperature higher than the first temperature.

The heating steam supply line L2 includes a steam header 51 that collects the steam S generated in the multiple once-through boilers 31, a connection line 52 that connects the multiple once-through boilers 31 to the steam header 51, and a steam supply line 53 that supplies the steam S collected in the steam header 51 to the heating heat exchanger 210. The steam supply line 53 is provided with a heating steam supply valve 54. The steam header 51 is also provided with a pressure gauge 55 for detecting the header pressure.

The hot water supply line L1 is provided with the above-mentioned heating heat exchanger 210. The heating heat exchanger 210 is an indirect heat exchanger, and performs indirect heat exchange between the hot water W1 sent from the first heating means 2 and flowing through the hot water supply line L1, and the steam S from the steam boiler device 30 flowing through the steam supply line 53. As a result, the hot water W1 heated to a first temperature by the first heating means 2 is heated by the heating heat exchanger 210 to a second temperature higher than the first temperature, for example, 75 to 95°C. In this indirect heat exchange, mainly sensible heat of the steam S is utilized.
The hot water W1 heated by the heating heat exchanger 210 is supplied to the hot water tank 40 through a hot water supply line L1.

The hot water tank 40 stores the hot water W1 supplied from the second heating means 3 .
This hot water tank 40 is equipped with a stored hot water temperature sensor 41 that detects the temperature of the stored hot water TW (hereinafter also referred to as stored water TW), and a first water level sensor 42 that detects the water level WL of the stored hot water TW.

The hot water production system 1 of this embodiment includes a water supply tank 60 that stores water. The water stored in the water supply tank 60 is supplied to the water heaters 11, 12, and 13 via the heat pump water supply line L3.

Each water heater 11, 12, 13 is provided with a water supply pump 17, 18, 19 for supplying water W1 to each water heater 11, 12, 13. Note that the water supply pumps 17, 18, 19 may be provided in the water supply lines in the water heaters 11, 12, 13, or in the heat pump water supply line L3 after branching off to correspond to each water heater 11, 12, 13.

Water supply pumps 17, 18, and 19 are driven with their rotation speed adjusted, for example, by inverter control, thereby adjusting the amount of water supplied to water heaters 11, 12, and 13. A configuration may be adopted in which a flow rate adjustment valve is provided for each water heater 11, 12, and 13, and the amount of water supplied to water heaters 11, 12, and 13 is adjusted by controlling the opening degree of the flow rate adjustment valve. When a flow rate adjustment valve is provided, water supply pumps 17, 18, and 19 are driven at a predetermined rotation rate (constant drive frequency).

The water stored in the water supply tank 60 is supplied to the steam boiler unit 30 as boiler feed water via the boiler feed water line L4. A boiler feed water pump 32 is provided on the boiler feed water line L4. The boiler feed water pump 32 is driven, for example, by inverter control, so as to adjust the amount of water supplied to the steam boiler unit 30. The boiler feed water pump 32 may be provided for each of the multiple once-through boilers 31, or may be provided within the steam boiler unit 30. The amount of water supplied may be adjusted by a flow control valve.

The hot water production system 1 of this embodiment further includes a bypass water supply line L5 for supplying the service water stored in the water supply tank 60 directly to the hot water tank 40. The bypass water supply line L5 is provided with a bypass water supply pump 61 and a bypass water supply valve 62. When the bypass water supply valve 62 is opened, the service water stored in the water supply tank 60 is replenished as make-up water to the hot water tank 40. At this time, cold water W5 (hereinafter also referred to as cold water W5) is supplied into the hot water tank 40 through the bypass water supply line L5.

The hot water production system 1 of this embodiment includes a control unit 100 for performing various controls. FIG. 3 is a functional block diagram showing the configuration of the control unit 100. As shown in FIG. 3, the control unit 100 includes a hot water supply control unit 110, a boiler control unit 120, a steam supply control unit 130, and a hot water storage control unit 140.

As described above, the control unit 100 is composed of multiple functional blocks, but each block does not necessarily need to be physically separate, and the functions of multiple blocks may be realized by a single CPU. The control unit 100 may also be divided into two or more parts, taking into consideration the placement and wiring of the devices to be controlled. For example, from the perspective of independent control of water heaters and boilers, it is preferable to incorporate the functions of the water heater control unit 110 into the local control unit of each water heater, and the functions of the boiler control unit 120 into a unit control panel that controls a group of boilers.

The hot water supply control unit 110 controls the heat pump hot water supply system 10. More specifically, it controls the operation of the water heaters 11, 12, and 13, such as starting and stopping the operation of each of them. The hot water supply control unit 110 also controls the water supply pumps 17, 18, and 19 based on the temperatures detected by the hot water temperature sensors 14, 15, and 16 to adjust the amount of hot water W1 supplied from the water heaters 11, 12, and 13. For this adjustment of the amount of hot water supplied, it is preferable to use feedback control using a PID algorithm.
For example, in the case of the first water heater 11, the hot water supply control unit 110 controls the rotation speed of the water supply pump 17 to adjust the amount of hot water supply so that the temperature detected by the hot water supply temperature sensor 14 becomes a predetermined target hot water supply temperature. The same applies to the control of the second water heater 12 and the third water heater 13.
In addition, a flow rate adjustment valve may be provided corresponding to each of the water heaters 11, 12, and 13, and the amount of hot water supplied may be adjusted by controlling the opening degree of the flow rate adjustment valve.
As a result, hot water W1 supplied from water heaters 11, 12, and 13 is heated to a first temperature corresponding to the target hot water temperature so that the hot water W1 is always at the target hot water temperature.
When the amount of heat source input to the heat pump circuit is small, the amount of hot water supplied is reduced so that the hot water temperature is maintained at the target hot water temperature.

Here, the target hot water temperature is set, for example, to 50 to 85°C. More preferably, it is set to 50 to 70°C. This preferred target hot water temperature will be described later with reference to Figures 7 to 10.

The boiler control unit 120 controls the number of steam boiler units 30 to be increased or decreased based on the header pressure value detected by the pressure gauge 55 provided in the steam header 51. More specifically, the amount of deviation between the header pressure value and the target steam pressure value is calculated so that the header pressure value becomes the target steam pressure value, and the number of boilers to be increased or decreased is calculated. This number increase or decrease control is publicly known, as disclosed in, for example, JP 2015-140975 A, and therefore will not be described here.

The steam supply control unit 130 controls the opening of the heating steam supply valve 54 based on the temperature detected by the hot water storage temperature sensor 41. More specifically, the steam supply control unit 130 controls the opening of the heating steam supply valve 54 to adjust the supply amount of steam S so that the temperature detected by the hot water storage temperature sensor 41 becomes a predetermined target hot water storage temperature. It is preferable to use feedback control for adjusting this supply amount. For example, the operation amount for the heating steam supply valve 54 is calculated by a PID algorithm so that the temperature detected by the hot water storage temperature sensor 41 converges to the target hot water storage temperature, and the steam supply control unit 130 outputs an opening designation signal to the actuator circuit of the heating steam supply valve 54.
By performing such steam supply control, indirect heat exchange is performed between the hot water W1 and the steam S in the heating heat exchanger 210 so that the temperature of the stored water TW in the hot water tank 40 (hereinafter also referred to as the stored hot water temperature) is always at the target stored hot water temperature. As a result, the hot water W1 is heated to a second temperature corresponding to the target stored hot water temperature.

Here, the target hot water storage temperature is preferably set to a temperature higher than the target hot water supply temperature (first temperature) and is set to 75 to 95°C. This preferred target hot water storage temperature will be described later with reference to Figures 7 to 10.

The hot water storage control unit 140 controls the bypass water supply valve 62 and the water heaters 11, 12, and 13 based on the detection result of the first water level sensor 42.
4, the first water level sensor 42 is configured as an electrode type water level detector equipped with a plurality of electrodes, including a first electrode 421, a second electrode 422, a third electrode 423, a fourth electrode 424, and a fifth electrode 425. Although not shown, the first water level sensor 42 may further include an electrode that constitutes a common electrode and an electrode for detecting an abnormal water level.
Each of the electrodes 421 to 425 detects whether the water level WL of the stored water TW in the hot water tank 40 has reached the lower end of each electrode depending on whether the lower end of the electrode is immersed in water.

Here, the water level detected by the first electrode 421 is water level LL, the water level detected by the second electrode 422 is water level L, the water level detected by the third electrode 423 is water level M, the water level detected by the fourth electrode 424 is water level H, and the water level detected by the fifth electrode 425 is water level HH. As shown in FIG. 4, the electrodes are inserted into the hot water tank 40 so that the lower end is located at the lowest height position, that is, the first electrode 421, the second electrode 422, the third electrode 423, the fourth electrode 424, and the fifth electrode 425. The water levels detected by these electrodes become multiple water level thresholds for controlling changes in the number of water heaters 11, 12, and 13 in operation, etc.

In this embodiment, the hot water storage control unit 140 controls the bypass water supply valve 62 and the water heaters 11, 12, and 13 based on the detection result of the first water level sensor 42. More specifically, when the hot water storage control unit 140 detects that the first water level sensor 42 has fallen below the water level LL, it opens the bypass water supply valve 62. Furthermore, when the water level in the hot water tank 40 is falling, the hot water storage control unit 140 executes a number control to increase the number of operating water heaters by one each time the water level detected by the first water level sensor 42 falls below the water level threshold by one step, and when the water level in the hot water tank 40 is rising, the hot water storage control unit 140 executes a number control to decrease the number of operating water heaters by one each time the water level detected by the first water level sensor 42 exceeds the water level threshold by one step. This number control is performed, for example, at water level H, water level M, and water level L when the water level is falling, and at water level M, water level H, and water level HH when the water level is rising.
In addition, the hot water storage control unit 140 may control the water heaters 11 , 12 , and 13 via the hot water supply control unit 110 .

Here, a specific description will be given of a case where the water level WL in the hot water tank 40 changes from a state in which it is located within the range of water level LL to water level L shown in FIG.
The water TW stored in the hot water tank 40 is supplied to a hot water demand point (not shown) through the hot water outlet line L6. When the amount of hot water W6 supplied from the hot water tank 40 to the hot water demand point exceeds the amount of hot water W1 supplied to the hot water tank 40 from the water heaters 11, 12, and 13 as the first heating means 2, the water level WL in the hot water tank 40 drops (see arrow A in FIG. 4). When the lower end of the first electrode rod 421 is exposed above the water surface at a certain point in time, the first water level sensor 42 detects that the water level WL has fallen below the water level LL.

When the hot water storage control unit 140 detects that the water level WL has fallen below the water level LL, it determines that the hot water tank 40 is on the verge of a drought, and operates all three water heaters 11, 12, and 13 to supply as much hot water W1 as possible to the hot water tank 40, while opening the bypass water supply valve 62 to supply the cold water W5 stored in the water supply tank 60 directly to the hot water tank 40.

In this way, when the water level WL falls below the water level LL, i.e., when the hot water tank 40 is on the verge of running out of water, the water level WL is quickly restored by supplying hot water W1 heated by the first heating means 2 as well as cold water W5 that has not passed through the first heating means 2.

By carrying out such control, the water level WL recovers (see arrow B in FIG. 4). Then, when the water surface comes into contact with the second electrode 422 and the tip of the second electrode 422 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level L.
When the hot water storage control unit 140 detects that the water level WL has exceeded the water level L (entered the range between the water level L and the water level M), it determines that the hot water tank 40 has recovered from the state immediately before the drought, and closes the bypass water supply valve 62. Note that, since the water level WL is still not high at this point, the operation of all three water heaters 11, 12, and 13 continues.

Next, when the water level WL rises further and the tip of the third electrode rod 423 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level M (entered the range between water level M and water level H).
At this time, it is determined that there is a little excess water in the storage tank, so one of the three water heaters is stopped, and only two water heaters continue to operate. For example, of the water heaters 11, 12, and 13, the third water heater 13 is stopped, and only the first and second water heaters 11 and 12 continue to operate. The bypass water supply valve 62 is kept closed.

Next, when the water level WL rises further and the tip of the fourth electrode rod 424 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level H (entered the range between water level H and water level HH).
At this time, it is determined that there is more water storage capacity, and two of the three water heaters are stopped, while only one water heater continues to operate. For example, of the water heaters 11, 12, and 13, the second and third water heaters 12 and 13 are stopped, while only the first water heater 11 continues to operate. Note that the bypass water supply valve 62 remains closed.

Next, when the water level WL rises further and the tip of the fifth electrode rod 425 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level HH.
At this time, it is determined that the amount of stored water is sufficient, and the operation of yet another water heater is stopped. That is, the operation of all water heaters 11, 12, and 13 is stopped. Note that the bypass water supply valve 62 is maintained in a closed state.

Next, a case where the water level WL starts to drop from this state will be described.
When the water level WL drops (see arrow C in Figure 4) and the lower end of the fourth electrode rod 424 is exposed from the water surface, the first water level sensor 42 detects that the water level WL has fallen below water level H (entered the range between water level M and water level H).
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level H, it resumes the operation of only one of the three water heaters. For example, among the water heaters 11, 12, and 13, it resumes the operation of the first water heater 11.

Here, if the water level WL rises after it falls below the water level H and the tip of the fifth electrode rod 425 is submerged in the water surface, i.e., if it is detected that the water level WL has risen above the water level HH, it is determined that the amount of stored water has again become sufficient, and as described above, all water heaters 11, 12, and 13 are stopped operating.

On the other hand, after the water level WL falls below the water level H, when the water level WL falls further (see arrow D in Figure 4) and the lower end of the third electrode rod 423 is exposed from the water surface, the first water level sensor 42 detects that the water level WL has fallen below the water level M (entered the range from water level L to water level M).
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level M, it operates only two of the three water heaters. For example, among the water heaters 11, 12, and 13, it operates the first and second water heaters 11 and 12.

From this state, when the water level WL drops further and the lower end of the second electrode rod 422 becomes exposed above the water surface, the first water level sensor 42 detects that the water level WL has fallen below the water level L (entered the range between water level LL and water level L).
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level L, it operates all three water heaters 11, 12, and 13.

If the water level WL drops further from this state and the lower end of the first electrode rod 421 becomes exposed above the water surface, i.e., if it is detected that the water level WL has fallen below the water level LL, the hot water storage control unit 140 determines that the hot water tank 40 is on the verge of a drought, and as described above, puts all three water heaters 11, 12, and 13 into operation and opens the bypass water supply valve 62.

In this way, the number of water heaters in operation is increased or decreased depending on the water level WL in the hot water tank 40, so the water level WL in the hot water tank 40 can be appropriately managed. In addition, power consumption can be reduced.

As shown in FIG. 4, the hot water storage control unit 140 shifts the number of water heaters in operation in a given water level range between when the water level is rising and when the water level is falling. For example, in the water level range between water level L and water level M, the number of water heaters in operation when the water level is rising is three, while the number of water heaters in operation when the water level is falling is two. This is to prevent a situation in which water heaters are frequently started and stopped when the water level WL fluctuates near the water level threshold. This reduces the risk of failure of water heaters and hot water supply control equipment (such as water supply pumps and water supply valves).

Instead of shifting the number of operating water heaters in a predetermined water level range between when the water level rises and when the water level falls, a status check time may be provided. In other words, when it is determined that the water level WL has remained below a predetermined water level threshold for a first predetermined time, control such as switching the number of operating water heaters may be performed.
For example, if it is determined that the water level WL has remained below the water level HH for a predetermined period of time during the process of the water level WL decreasing as shown by arrow C in Fig. 4, the number of operating water heaters is switched from 0 to 1. By setting a status check time in this manner, it is possible to prevent a situation in which the water heaters are frequently started and stopped, even if the number of operating water heaters in the water level range of H to HH, which is a predetermined water level range, is the same when the water level is rising and falling. Note that similar status check times are set for other water level thresholds as well.

A configuration may be adopted in which, when it is determined that the water level WL has remained above a predetermined water level threshold for a second predetermined time, control is performed such as switching the number of water heaters in operation. For example, during the process of the water level WL rising as shown by arrow B in FIG. 4, when it is determined that the water level WL has remained above the water level LL for a predetermined time, the bypass water supply valve 62 may be closed. Furthermore, when it is determined that the water level WL has risen and remained above the water level L for a predetermined time, the number of water heaters in operation may be switched from three to two. Note that similar status confirmation times are set for other water level thresholds as well.

By such control, it is possible to perform control such as changing the number of water heaters in operation based on the status confirmation time for the water level WL to continue to fall or the status confirmation time for the water level WL to continue to rise.
The set value of the state check time is preferably adjustable. By making the set value of the state check time adjustable, it is possible to set a first predetermined time as a delay time corresponding to a water level width required to confirm that the water level continues to fall, taking into consideration the difference in the rate at which the water level falls depending on the cross-sectional area of the hot water tank 40, when the water level falls below the water level threshold. Alternatively, it is possible to set a second predetermined time as a delay time corresponding to a water level width required to confirm that the water level continues to rise, taking into consideration the difference in the rate at which the water level rises depending on the cross-sectional area of the hot water tank 40, when the water level exceeds the water level threshold.
The setting value of the status check time can be adjusted manually or automatically, and can be set to a value greater than 0. The status check time is measured using an internal timer of the control unit 100 or the like.

The first water level sensor 42 is not limited to an electrode-type water level detector, and various water level detectors can be used. For example, five float-type water level detectors may be provided to detect each water level threshold. Also, an electrode-type water level detector and a float-type water level detector may be used in combination. Furthermore, multiple water level thresholds may be detected using a water level detection unit such as a pressure-type water level sensor that can measure continuous water levels. The number of water level thresholds to be detected is not limited to five.

Figure 5 is a diagram showing the number of operating water heaters 11, 12, and 13 and the total amount of make-up water when the water level rises. The horizontal axis represents the water level WL in the hot water tank 40, and the vertical axis represents the total amount of make-up water. In Figure 5, the amount of hot water supplied from the first heat pump water heater 11 is represented as "HP1", the amount of hot water supplied from the second heat pump water heater 12 is represented as "HP2", and the amount of hot water supplied from the third heat pump water heater 13 is represented as "HP3".

When the water level WL rises after falling below the water level LL, as shown in FIG. 5, hot water W1 is supplied from the three water heaters 11, 12, and 13, and cold water W5 is supplied directly from the water supply tank 60 until the water level WL exceeds the water level L. The total amount of make-up water at this time is as shown on the vertical axis of FIG. 5.

Thereafter, when the water level WL exceeds the water level L, the bypass water supply valve 62 is closed. Therefore, the total amount of make-up water decreases as shown in FIG.
Further thereafter, when the water level WL exceeds the water level M, the operation of the third water heater 13 is stopped, and only the operation of the first and second water heaters 11, 12 is continued. Therefore, the total amount of make-up water is further reduced as shown in FIG.
Further, when the water level WL subsequently exceeds the water level H, the operation of the second water heater 12 is stopped and only the operation of the first water heater 11 is continued. Therefore, the total amount of make-up water is further reduced as shown in FIG.
Then, when the water level WL exceeds the water level HH, the operation of the first water heater 11 is also stopped, and the operation of all three water heaters is stopped.

In this embodiment, the hot water temperature from the water heaters 11, 12, and 13 is controlled to be constant. For example, the target hot water temperature is set to 70°C. The water heaters 11, 12, and 13 supply hot water W1 at a first temperature that corresponds to this target hot water temperature.

Note that stopping the operation of the water heaters described above also includes stopping the supply of hot water from the water heaters, such as stopping the operation of the water supply pumps 17, 18, and 19 and closing the flow control valves corresponding to each water heater 11, 12, and 13. It also includes stopping the operation of the refrigerant compressor 91 to stop the circulation of refrigerant in the heat pump circuit.

The priority of which of the water heaters 11, 12, and 13 to stop/restart may be determined appropriately based on the state and operation history of each water heater. It may also be determined in advance.

In this way, the number of water heaters in operation is controlled according to the water level WL in the hot water tank 40, so the water level WL in the hot water tank 40 can be appropriately managed. Also, power consumption can be reduced.

Fig. 6 is a modified example of the hot water storage control shown in Fig. 5. In this modified example, a configuration for detecting the water level threshold value in more detail may be adopted as shown in Fig. 6. Here, the water levels LL, L, M1, M2, M3, M4, H, and HH are set as detectable water level threshold values in order from the lowest water level.
In this modification, in addition to changing the number of operating water heaters, the target hot water temperature of the water heater is changed. Specifically, the water heater is capable of switching the target hot water temperature between multiple stages within a temperature range higher than a first temperature and lower than a second temperature.

In more detail, in this modified example, when the water heater is operating with its target hot water temperature set to the first temperature, if the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, control is executed to increase the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters, and when the water heater is operating with its target hot water temperature increased by one step, control is executed to decrease the number of operating water heaters by one and at the same time return the target hot water temperature to the first temperature. In addition, when the water heater is operating with the target hot water temperature set to the first temperature, if the water level detected by the first water level sensor 42 falls one step below the water level threshold, control is executed to increase the number of operating water heaters by one and to raise the target hot water temperature of the water heater by one step, and when the water heater is operating with the target hot water temperature of the water heater raised one step, control is executed to lower the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters.

FIG. 6 is a diagram showing the number of operating water heaters 11, 12, and 13, the hot water temperature, and the total amount of make-up water when the water level is rising.
For example, consider a case where the water level WL falls below the water level LL, and then rises to a position between the water level L and the water level M1. At this time, the target hot water temperature of the three water heaters 11, 12, and 13 is set to 70° C. (first temperature).
When the water level WL rises further from this state and exceeds the water level M1, control is executed to raise the target hot water temperature of water heaters 11, 12, and 13 by one step to 80° C. while maintaining the number of operating water heaters 11, 12, and 13. Here, the temperature when raised by one step is set to a temperature lower than the target hot water storage temperature (second temperature) of hot water tank 40.

Next, while the target hot water temperature of water heaters 11, 12, and 13 is being increased by one step to 80°C and the water level WL rises further and exceeds water level M2, the number of operating water heaters is reduced by one and control is executed to return the target hot water temperature to 70°C (first temperature).
Even when the water level WL continues to rise, control is similarly alternately performed between increasing the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters, and decreasing the number of operating water heaters by one while simultaneously returning the target hot water temperature to the original value.

Next, we consider a situation in which the water level WL exceeds the water level HH, and then the water level WL drops, for example, to a position between the water level M4 and the water level H, and the target hot water temperature of the water heater is set to 70°C (first temperature).
In this example, the number of operating water heaters in a given water level range is set to be the same when the water level is rising and when the water level is falling, using the above-mentioned method of checking the status. Therefore, the case when the water level is falling will also be described using FIG. 6.
When the water level WL falls further from a state in which it is between water level M4 and water level H and falls below water level M4, the number of water heaters in operation is increased by one to operate as two, and at the same time, the target hot water temperature of the water heater is raised by one step to 80°C.

Next, when the water level WL falls below water level M3 while the water heater is operating with its target hot water temperature set to 80°C, control is executed to lower the target hot water temperature of the water heater by one step back to 70°C while maintaining the number of operating water heaters.
Furthermore, even when the water level WL drops, control is performed alternately between increasing the number of operating water heaters by one and raising the target hot water temperature of the water heaters by one step, and returning the target hot water temperature to its original state while maintaining the number of operating water heaters.

In this modified example, the method of checking the status is used, but this is not limiting. As in the case described in FIG. 4, a method of shifting the number of water heaters in operation in a given water level range when the water level is rising and when the water level is falling may also be used.

In addition, when the water level rises, control may be performed to increase the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters, and if the water level rises further, control may be performed to increase the target hot water temperature of the water heater by another step while maintaining the number of operating water heaters.
For example, when the water level exceeds M1, control is executed to increase the target hot water temperature of water heaters 11, 12, 13 by one step to 75° C. while maintaining the number of operating water heaters 11, 12, 13. Then, during operation in this state, when the water level WL further rises and exceeds water level M2, control is executed to increase the target hot water temperature of water heaters 11, 12, 13 by another step to 80° C. while maintaining the number of operating water heaters 11, 12, 13. Furthermore, during operation in this state, when the water level WL further rises and exceeds water level M3, control is executed to reduce the number of operating water heaters by one and to return the target hot water temperature to 70° C. (first temperature).
When the water level is decreasing, the control is executed so as to perform the opposite operation.

In other words, when the water heater is operating with the target hot water temperature set to the first temperature, if the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, control is executed to increase the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters; and when the water heater is operating with the target hot water temperature of the water heater increased by one step or more, if the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, control is executed to reduce the number of operating water heaters by one and at the same time return the target hot water temperature to the first temperature, or control is executed to increase the target hot water temperature of the water heater by another step while maintaining the number of operating water heaters. In addition, when the target hot water temperature of the water heater is set to the first temperature and the detected water level of the first water level sensor 42 falls one step below the water level threshold, the number of operating water heaters is increased by one and at the same time control is executed to raise the target hot water temperature of the water heater by one or more steps (e.g., two steps); when the target hot water temperature of the water heater is increased by one or more steps (e.g., two steps) and the detected water level of the first water level sensor 42 falls one step below the water level threshold, control may be executed to lower the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters.

In general, increasing the target hot water temperature of the water heater reduces the amount of hot water that can be supplied, and lowering the target temperature of the water heater increases the amount of hot water that can be supplied. Taking this into consideration, by adopting the control shown in this modified example, it becomes possible to finely adjust the total amount of make-up water while keeping the number of operating heat pumps as constant as possible. This allows the water level in the hot water tank to be appropriately managed. Also, because it is possible to continue operating the heat pump as long as possible, it is possible to eliminate the problem of low-temperature water supply at the initial stage of restarting heat pump operation.

As described above, the hot water production system 1 of this embodiment comprises a first heating means 2 that heats the water W1 to a first temperature while circulating it through the condenser of the heat pump type hot water supply system 10, and a second heating means 3 that uses steam S generated by the steam boiler device 30 to raise the temperature of the water W1 heated by the first heating means 2 to a second temperature higher than the first temperature.
The effect of adopting this configuration will be described in detail with reference to FIGS.

FIG. 7 shows a first comparative example in which a hot water producing system is constructed using only steam S from a steam boiler device 30 as a heating means.
The temperature of hot water required by the hot water demand point varies depending on the application, but for example, when washing bottles for food or medicine, pasteurizing sterilization (sterilization of bottles), etc., hot water in the high temperature range of about 75° C. to 95° C. may be required. Here, a case will be described in which the hot water production system supplies hot water in the high temperature range, for example, hot water at 90° C., to the hot water demand point.

The hot water production system 5 in Fig. 7 uses only steam S from a steam boiler device 30 as a heating means. Here, the steam boiler has a gas-fired or oil-fired burner and generates steam using fossil fuels. Therefore, the _CO2 emissions and running costs of this hot water production system 5 are relatively high, and a significant reduction is required.

Therefore, as a heating means, it is conceivable to adopt a hot water production system using an electrically driven heat pump hot water supply system 10 that does not use fossil fuels and has a high COP (Coefficient of Performance).
8 shows a second comparative example in which a hot water production system 6 is constructed using only a heat pump type hot water supply system 10 as a heating means. The _CO2 emission coefficient of electricity (0.51 _kgCO2 /kWh) is larger than the _CO2 emission coefficient of city gas 13A (0.18 _kgCO2 /kWh), but when comparing the _CO2 emission per output, the heat pump with a higher COP has less CO2 emission than the steam boiler. In addition, the unit price of electricity (about 15 yen/kWh) is higher than the fuel unit price of city gas 13A (about 6.2 yen/kWh), but when comparing the running cost per output, the heat pump with a higher COP is cheaper than the steam boiler. Therefore, the hot water production system 6 has lower _CO2 emission and running cost than the hot water production system 5 of FIG. 7.

However, while a heat pump has a relatively high COP and is highly effective in reducing _CO2 emissions when the hot water temperature is low, when the hot water temperature is increased, the COP becomes relatively low and the effect of reducing _CO2 emissions decreases.
For example, the COP of a heat pump when supplying hot water at 90°C is equivalent to 2.8. Therefore, compared to the hot water production system 5 that uses only steam from a steam boiler as a heating means, the reduction in _CO2 emissions ( _CO2 emission reduction ratio) is only about 10%. In addition, the reduction in running costs (running cost reduction ratio) is also only about 20%.

Next, we will consider the hot water production system 1 of this embodiment, i.e., a hybrid hot water production system equipped with a first heating means 2 that heats the water W1 to a first temperature while circulating it through the condenser of the heat pump hot water supply system 10, and a second heating means 3 that uses steam S generated by the steam boiler device 30 to raise the temperature of the water W1 heated by the first heating means 2 to a second temperature higher than the first temperature.

In such a hot water production system 1, the heat pump hot water supply system 10 as the first heating means 2 heats the water W1 to a temperature range where it can be operated with high efficiency, for example to 70°C, and this heated hot water W1 can be heated to a high temperature range, for example to 90°C, using steam S from the steam boiler device 30, making it possible to produce hot water in the high temperature range with high efficiency.

Here, the COP of the heat pump when the hot water supply temperature is 70° C. is, for example, equivalent to 4.2, which is very high. In the hot water producing system 1 of this embodiment, the heat pump is responsible for heating up to a temperature range where such a high COP can be maintained.
For example, when it is desired to produce hot water at 90° C. using the hot water production system 1, the heat pump is responsible for heating up to 70° C. In this case, the heat pump is responsible for about 60% to 80% (load factor 60% to 80%) of the total heat output required to produce hot water at 90° C.
The steam boiler is responsible for raising the temperature from 70° C. to 90° C. At this time, the steam boiler is responsible for about 20% to 40% (load factor 20% to 40%) of the total thermal output required to produce hot water at 90° C.

When the heat pump and steam boiler are used in this combination, the hot water production system 1 reduces CO2 emissions by approximately 30%, which is extremely effective, compared to the hot water production system 5, which uses only steam from a steam boiler as a heating means. In addition, the running costs are also reduced by approximately 35%, which is also extremely effective.

In this way, by using the hot water producing system 1 of the present embodiment, it is possible to extremely effectively reduce CO ₂ emissions and running costs even when the outlet hot water temperature is increased.
Furthermore, with the hot water production system 1 of this embodiment, by appropriately adjusting the load factors of the heat pump and steam boiler, i.e., the share of thermal output (output allocation) of each, in accordance with the target hot water outlet temperature, it is possible to extremely effectively reduce _CO2 emissions and running costs.
It is preferable that the relationship between the heat pump and steam boiler output ratios according to the target hot water outlet temperature of the hot water production system 1 is stored in a table or a formula. For example, the target hot water outlet temperature can be configured to be set, and an appropriate heat pump and steam boiler output ratio is set according to the set target hot water outlet temperature.

FIG. 10 is a graph showing the CO ₂ emission reduction ratio and the running cost reduction ratio when hot water of, for example, 90° C. is produced and dispensed using the hot water producing system 1 of this embodiment.

The horizontal axis of the graph in Fig. 10 represents the hot water temperature of the heat pump, and the vertical axis of the line graph in Fig. 10 represents the _CO2 emission reduction ratio and the running cost reduction ratio.
Here, the _CO2 emission reduction ratio indicates the proportion of _CO2 emissions that can be reduced by the hot water producing system 1 of this embodiment when the _CO2 emissions of the hot water producing system 5 that uses only steam from a steam boiler as heating means are taken as 100%. In other words, if the _CO2 emission reduction ratio is 25%, it means that by switching to the hot water producing system 1, 100% _CO2 emissions can be reduced to 75%.
On the other hand, the running cost reduction ratio indicates the percentage of the running cost that can be reduced by the hot water producing system 1 of this embodiment, assuming that the running cost of the hot water producing system 5 that uses only steam from a steam boiler as a heating means is 100%. In other words, if the running cost reduction ratio is 30%, it means that by switching to the hot water producing system 1, the running cost of 100% can be reduced to 70%.
The vertical axis of the bar graph in FIG. 10 indicates the output ratio of the heat pump and the steam boiler, that is, the share of the thermal output (output allocation) of each.
The bar graph showing the heat pump output rate is accompanied by the COP at the hot water supply temperature of the heat pump. The higher the hot water supply temperature, the lower the COP.

In the line graph of Figure 10, comparing the data for heat pump hot water supply temperature = 90°C with the data for heat pump hot water supply temperature = 50°C to 80°C, it can be seen that compared to producing hot water at 90°C using only a heat pump (data for heat pump hot water supply temperature = 90°C), heating to 50-80°C with a heat pump and then using steam to raise the temperature to 90°C clearly has a greater effect in reducing _CO2 emissions and running costs. For example, if the heat pump is used to heat to 50-70°C and then steam is used to raise the temperature to 90°C, the effects of reducing _CO2 emissions and running costs are greater.
Furthermore, from the trend of the line graph, it can be seen that the effects of the present invention can be obtained even if, for example, the temperature is raised to 85°C using a heat pump and then raised to 90°C using steam.

In this way, by using the hot water production system 1 of this embodiment, i.e., a hybrid hot water production system equipped with a first heating means 2 that heats the service water W1 to a first temperature while circulating it through the condenser of the heat pump hot water supply system 10, and a second heating means that uses steam S generated by the steam boiler device 30 to raise the temperature of the service water W1 heated by the first heating means 2 to a second temperature higher than the first temperature, it is possible to extremely effectively reduce _CO2 emissions and running costs even when the outlet hot water temperature of the system is increased.

The first heating means 2 of the hot water producing system 1 of this embodiment heats the water W1 to the first temperature while causing the water W1 to flow through the condenser of the heat pump water heater.
By adopting a configuration in which the hot water heated by the second heating means 3 does not return to the condenser but flows through it once, hot water W1 at the first temperature heated by the first heating means 2 is always additionally supplied, and this hot water is heated by the second heating means 3. Therefore, even when the hot water demand point requires a large amount of hot water to be discharged, it becomes easy to always discharge hot water at a stable temperature.
Furthermore, in the case where the hot water tank 40 is provided, even if the water level WL in the hot water tank 40 drops, hot water W1 at the first temperature heated by the first heating means 2 is always additionally supplied to the hot water tank 40 according to the level of the drop. Thus, with this configuration, the frequency of occurrence of a situation in which cold water W5 must be supplied to the hot water tank 40 is reduced. Therefore, the supply of cold water W5 rarely causes the temperature of the stored water TW in the hot water tank 40 to drop drastically.

The second heating means 3 of the hot water production system 1 of this embodiment indirectly exchanges heat between the water W1 heated by the first heating means 2 and the steam S generated by the steam boiler device 30, thereby raising the temperature of the water W1 to a second temperature higher than the first temperature.
In this way, by adopting indirect heat exchange as the heat exchange method, the temperature of the water W1 can be raised without directly supplying the steam S to the water W1. In other words, since the steam S is not mixed with the water W1, it is possible to prevent boiler chemicals such as boiler compound from being mixed into the hot water tank 40. Therefore, the quality of the water W1 can be maintained. In addition, the hot water storage control of the hot water tank 40 is not easily affected by disturbances that may occur when the steam S is directly supplied.

In order to obtain such an effect, it is particularly preferable to use a heat pump type water heater having an electrically driven refrigerant compressor as the water heater and a steam boiler having a gas-fired or oil-fired burner as the steam boiler.
The effects of the present invention can be appropriately obtained by setting the first temperature to 50 to 85° C. and the second temperature to a temperature higher than the first temperature, 75 to 95° C. Preferably, the first temperature is set to 50 to 80° C. and the second temperature is set to a temperature higher than the first temperature, 75 to 95° C. More preferably, the first temperature is set to 50 to 70° C. and the second temperature is set to 75 to 95° C.
In this way, by combining a heat pump water heater having an electrically driven refrigerant compressor with a steam boiler having a burner that burns fossil fuel, and appropriately setting the temperature range for heating by each, it is possible to achieve a greater reduction in _CO2 emissions and a greater reduction in running costs than when high-temperature water is produced by a heat pump water heater alone or a steam boiler alone.

The hot water production system 1 of this embodiment is preferably provided with a hot water tank 40 for storing the hot water W1 delivered from the second heating means 3, but a configuration may be adopted in which the hot water W1 delivered from the second heating means 3 is directly supplied to a hot water demand point (not shown) without providing the hot water tank 40. In this case, it is preferable to provide a second heating means outlet hot water temperature sensor in the hot water supply line L1 downstream of the heating heat exchanger 210 instead of the storage hot water temperature sensor 41, and to control the opening degree of the heating steam supply valve 54 based on this second heating means outlet hot water temperature sensor.

In order to perform appropriate hot water storage control, it is preferable to have multiple water heaters constituting the heat pump hot water supply system 10, but it may be one. In the case of one water heater, the control by multiple water heaters described in this embodiment is not performed, and the hot water supply amount is controlled based on the water level WL of the hot water tank 40, and the hot water supply is controlled on and off.
In addition, when multiple water heaters are used, the number can be any number greater than or equal to two.

Although it is preferable to have a plurality of boilers constituting the steam boiler device 30, it may be a single boiler. In the case of a single boiler, the combustion rate may be controlled based on the measured steam pressure value and the target steam pressure value.
When multiple boilers are used, the number of boilers may be any number greater than or equal to two.
Furthermore, the boiler constituting the steam boiler device 30 may be a boiler other than a once-through boiler.

The hot water produced can be used for a variety of purposes, including but not limited to washing bottles for food or medicine and sterilizing them in a pasteurizer.
For example, hot water can be used in the food and beverage industry for purposes such as heating raw materials and processed products, washing bottles, and cleaning-in-place (CIP) of manufacturing equipment.
In addition, when steam is used in the food and beverage industry, the steam S generated by the steam boiler device 30 can be used for high-temperature cooking (frying, steaming, stir-frying), retort sterilization (sterilization of pouches and cans), stationary in place sterilization (SIP) of manufacturing equipment, and back-up for hot water production.
In the case of hot water use in the machinery field, it can be used for washing and degreasing.
Even in these applications, hot water in the high temperature range of approximately 75°C to 95°C may be required, and in cases where hot water in such a high temperature range is required, the hot water production system 1 of this embodiment can be particularly suitably used.

In addition, a configuration may be adopted in which a drain recovery line (not shown) is provided between the heating heat exchanger 210 and the water supply tank 60 to recover steam drain generated in the heating heat exchanger 210 in the water supply tank 60.
This allows the steam drain generated in the heating heat exchanger 210 to be effectively utilized for preheating the service water supplied to the heat pump hot water supply system 10 and the feed water supplied to the steam boiler device 30, and for water conservation.

The hot water production system 1 of this embodiment described above provides the following effects:

(1) The hot water production system 1 of this embodiment includes a first heating means 2 that heats service water W1 to a first temperature while flowing it through the condenser 92 of the heat pump water heaters 11, 12, and 13 of the heat pump water supply system 10, and a second heating means 3 that indirectly exchanges heat with the service water heated by the first heating means 2 with steam S generated in the steam boiler device 30 to heat the service water to a second temperature higher than the first temperature.
In this way, the first heating means 2 heats the water up to a temperature that can be efficiently heated by the heat pump water heaters 11, 12, and 13, and the water is further heated by indirect heat exchange with steam S, so that even if the outlet water temperature is increased, a hot water production system can be provided that is highly effective in reducing _CO2 emissions and running costs. In addition, since steam is used for heating, the temperature control responsiveness is also good. Furthermore, by adopting indirect heat exchange, it is possible to prevent boiler chemicals such as boiler compounds from being mixed into the hot water tank.

(2) The water heaters 11, 12, and 13 of the hot water production system 1 of this embodiment have an electrically driven refrigerant compressor 91, the steam boiler device 30 has a gas-fired or oil-fired burner, the first temperature is 50 to 70°C, and the second temperature is 75 to 95°C.
In this way, by combining a heat pump water heater having an electrically driven refrigerant compressor with a steam boiler having a burner that burns fossil fuel, and appropriately setting the temperature range for heating by each, it is possible to achieve a greater reduction in _CO2 emissions and a greater reduction in running costs than when high-temperature water is produced by a heat pump water heater alone or a steam boiler alone.

(3) The second heating means 3 of the hot water producing system 1 of this embodiment includes a heating heat exchanger 210 that indirectly exchanges heat between the hot water W1 heated by the water heaters 11, 12, 13 and the steam S generated by the steam boiler device 30, a hot water tank 40 that stores the hot water W1 heated by the heating heat exchanger 210, a heating steam supply line L2 that supplies the steam S generated by the steam boiler device 30 to the heating heat exchanger 210, and a heating steam supply valve 54 provided in the heating steam supply line L2.
This allows effective indirect heat exchange between the hot water W1 and the steam S at an appropriate position before entering the hot water tank 40.

(4) The second heating means 3 of the hot water production system 1 of this embodiment is equipped with a hot water storage temperature sensor 41 that detects the temperature of the hot water in the hot water tank 40, and controls the opening degree of the heating steam supply valve 54 so that the detected temperature of the hot water storage temperature sensor 41 becomes the target hot water storage temperature.
This makes it possible to appropriately control the temperature of the hot water in the hot water tank 40 .

(5) The hot water producing system 1 of this embodiment includes a first water level sensor 42 that detects the water level in the hot water tank 40, a bypass water supply line L5 that supplies water to the hot water tank 40 without going through a water heater, and a bypass water supply valve 62 provided in the bypass water supply line L5, and when the water level detected by the first water level sensor 42 falls below the set water level, the bypass water supply valve 62 is opened.
This allows water to be replenished through the bypass water supply line L5 at an appropriate time when the hot water in the hot water tank 40 becomes low.

(6) The hot water producing system 1 of this embodiment is equipped with a first water level sensor 42 that detects the water level in the hot water tank 40, and the first heating means 2 includes multiple water heaters 11, 12, and 13. The hot water tank 40 has multiple water level thresholds set therein for changing the number of operating water heaters 11, 12, and 13. When the water level in the hot water tank 40 drops, number control is executed to increase the number of operating water heaters 11, 12, and 13 by one each time the water level detected by the first water level sensor 42 falls below the water level threshold by one step, and when the water level in the hot water tank 40 rises, number control is executed to decrease the number of operating water heaters 11, 12, and 13 by one each time the water level detected by the first water level sensor 42 exceeds the water level threshold by one step.
In this way, the number of operating water heaters 11, 12, and 13 is increased or decreased depending on the water level in hot water tank 40, so that it is possible to appropriately manage the water level in hot water tank 40. Also, it is possible to reduce power consumption.

(7) The hot water production system 1 of this embodiment is equipped with a first water level sensor 42 that detects the water level in the hot water tank 40, and the first heating means 2 includes multiple water heaters 11, 12, 13. Multiple water level thresholds are set in the hot water tank 40 for changing the number of operating water heaters 11, 12, 13 and/or the target hot water temperature. The water heaters 11, 12, 13 are capable of switching between multiple target hot water temperatures within a temperature range higher than the first temperature and lower than the second temperature. During operation with the target hot water temperature of the water heater set to the first temperature, when the detected water level of the first water level sensor 42 exceeds the water level threshold by one step, control is executed to increase the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters, and the system is operated with the target hot water temperature of the water heater increased by one or more steps. During operation, when the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, control is executed to reduce the number of operating water heaters by one and at the same time return the target hot water temperature to the first temperature, or to increase the target hot water temperature of the water heater by another step while maintaining the number of operating water heaters; during operation with the target hot water temperature of the water heater set to the first temperature, when the water level detected by the first water level sensor 42 falls below the water level threshold by one step, control is executed to increase the number of operating water heaters by one and at the same time raise the target hot water temperature of the water heater by one or more steps; during operation with the target hot water temperature of the water heater raised by one or more steps, when the water level detected by the first water level sensor 42 falls below the water level threshold by one step, control is executed to lower the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters.
This makes it possible to appropriately manage the water level in the hot water tank 40. Also, it becomes possible to continue operation of the heat pump as long as possible, and it is possible to solve the problem of low-temperature water supply at the initial stage of restarting the operation of the heat pump.

(8) The water heaters 11, 12, and 13 of the hot water production system 1 of this embodiment are equipped with a water line that circulates water to the condenser 92, a flow control valve or a water supply pump 17, 18, and 19 provided on the water line, and a water supply temperature sensor 14, 15, and 16 that detects the hot water temperature of the water heaters 11, 12, and 13, and the opening of the flow control valve or the rotation speed of the water supply pump 17, 18, and 19 is controlled so that the detected temperature of the hot water temperature sensor 14, 15, and 16 becomes the target hot water temperature.
This allows the hot water temperatures of water heaters 11, 12, and 13 to be appropriately controlled.

(9) The hot water production system 1 of this embodiment includes a water supply tank 60 for storing water to be supplied to the water heaters 11, 12, and 13 and/or feed water to be supplied to the steam boiler device 30, and a drain recovery line for recovering steam drain generated in the heating heat exchanger 210 in the water supply tank 60.
This allows the steam drain generated in the heating heat exchanger 210 to be effectively utilized for preheating the water supplied to the water heaters 11, 12, and 13 and/or the feed water supplied to the steam boiler device 30, and for water conservation.

(10) The hot water production method of this embodiment includes a first heating process in which service water W1 is heated to a first temperature while being passed through condensers 92 of heat pump water heaters 11, 12, and 13 of heat pump water supply system 10, and a second heating process in which the service water heated in the first heating process is indirectly heat exchanged with steam S generated in steam boiler device 30 to heat the service water to a second temperature higher than the first temperature.
In this way, the water is heated in the first heating step up to a temperature that can be efficiently heated by the heat pump water heaters 11, 12, and 13, and further heating is performed by indirect heat exchange with steam S, so that even if the outlet temperature is increased, a hot water production system can be provided that is highly effective in reducing CO2 emissions and running costs. In addition, since steam is used for heating, the temperature control responsiveness is also good. Furthermore, by adopting indirect heat exchange, it is possible to prevent boiler chemicals such as boiler compounds from being mixed into the hot water tank.

Second Embodiment
Next, a second embodiment will be described with reference to Fig. 11. Note that the description of the same configuration as the first embodiment will be omitted.
The hot water producing system 1 of the second embodiment is equipped with, as an additional backup heating means, a backup steam supply line L12 that supplies steam S generated by the steam boiler device 30 to the hot water tank 40, and a backup steam supply valve 212 provided on the backup steam supply line L12.
FIG. 11 is a diagram showing a hot water producing system 1 according to a second embodiment of the present invention.

As shown in Fig. 11, in this embodiment, the steam supply line 53 (heating steam supply line L2) branches midway, one of which is connected to the heating heat exchanger 210 and the other of which is connected to the hot water tank 40. The line connected to the heating heat exchanger 210 is provided with a heating steam supply valve 54 similar to that of the first embodiment. On the other hand, the line connected to the hot water tank 40 constitutes a backup steam supply line L12, and this backup steam supply line L12 is provided with a backup steam supply valve 212.
These backup steam supply line L12 and backup steam supply valve 212 constitute additional backup heating means, and use steam from the steam boiler device 30 to heat the water TW stored in the hot water tank 40.

In this embodiment, as in the first embodiment, the water W1 heated by the first heating means 2 is further heated by the heating heat exchanger 210 constituting the second heating means 3. At this time, the heating steam supply valve 54 is controlled based on the temperature detected by the hot water temperature sensor 41 so that the temperature of the stored water TW in the hot water tank 40 becomes the target hot water temperature. However, in cases where a sudden load change occurs at the hot water demand point and cold water W5 is supplied from the bypass water supply line L5, it may be difficult to maintain the target hot water temperature.

Therefore, in this embodiment, the temperature of the water TW stored in the hot water tank 40 is increased by using the additional backup heating means described above.
Specifically, the hot water producing system 1 of this embodiment is capable of supplying steam S from the steam boiler device 30 into the hot water tank 40 via the backup steam supply line L12. By blowing the steam S into the hot water tank 40, direct heat exchange is performed between the hot water TW stored in the hot water tank 40 and the steam S from the steam boiler device 30.
In this way, by adopting direct heat exchange as the heat exchange method of the backup heating means, it becomes possible to utilize all of the heat of the steam S from the steam boiler device 30, i.e., sensible heat and latent heat, and the hot water TW stored in the hot water tank 40 can be quickly heated.

In the hot water producing system of this embodiment, the steam supply control unit 130 controls the backup steam supply valve 212 in addition to the steam supply control described in the first embodiment.
For example, the steam supply control unit 130, in cooperation with the hot water storage control unit 140, performs control to open the backup steam supply valve 212 when opening the bypass water supply valve 62. Also, when closing the bypass water supply valve 62, the steam supply control unit 130 performs control to close the backup steam supply valve 212.

Specifically, when it is detected that the water level WL in the hot water tank 40 has dropped below the water level LL, it is determined that the hot water tank 40 is about to enter a state of drought, and similarly to the first embodiment, all three water heaters 11, 12, 13 are operated to supply as much hot water W1 as possible to the hot water tank 40, and the bypass water supply valve 62 is opened to directly replenish the cold water W5 stored in the water supply tank 60 to the hot water tank 40 (see arrow A in Fig. 4). At this time, in this embodiment, taking into consideration that the temperature of the stored water TW in the hot water tank 40 drops due to the supply of cold water W5, the backup steam supply valve 212 is fully opened to supply as much steam S as possible to the hot water tank 40.
In this manner, by fully opening the backup steam supply valve 212 and supplying steam S, the temperature of the stored water TW in the hot water tank 40, which has been lowered by the supply of cold water W5, is raised as quickly as possible.

Then, when it is detected that the water level WL in the hot water tank 40 has risen and exceeded the water level L (entered the range between water level L and water level M), it is determined that the hot water tank 40 has recovered from the state immediately before the drought, and the bypass water supply valve 62 is closed, as in the first embodiment (see arrow B in FIG. 4). At this time, in this embodiment, the backup steam supply valve 212 is also closed.
During this time, the heating steam supply valve 54 is controlled based on the temperature detected by the hot water temperature sensor 41 so that the temperature of the stored water TW in the hot water tank 40 becomes the target hot water temperature.

With the above configuration, when the bypass water supply valve 62 is opened, the backup steam supply valve 212 is also opened at the same time, making it possible to respond to sudden load fluctuations that make it difficult to maintain the temperature of the hot water TW in the hot water tank 40. Furthermore, since heat is exchanged directly between the hot water TW and the steam S, the temperature of the hot water TW can be raised quickly.

In addition, the steam supply control unit 130 may be configured to control the opening degree of the heating steam supply valve 54 and the backup steam supply valve 212 so that the detected temperature of the hot water storage temperature sensor 41 becomes the target hot water storage temperature.
In this case, the temperature zone for controlling the opening degree of the backup steam supply valve 212 may be a temperature zone lower than the temperature zone for controlling the opening degree of the heating steam supply valve 54 .

For example, the heating steam supply valve 54 may be controlled so that the temperature of the stored water TW in the hot water tank 40 becomes the target hot water temperature (e.g., 90°C), while the backup steam supply valve 212 may be controlled when the temperature of the stored water TW in the hot water tank 40 falls below a predetermined temperature (e.g., 80°C) that is lower than the target hot water temperature.

Alternatively, the heating steam supply valve 54 and the backup steam supply valve 212 may be assumed to be a single steam supply valve, and an opening degree may be assigned to them, and feedback control may be performed using a PID algorithm or the like.
For example, the opening of the heating steam supply valve 54 from 0% (fully closed) to 100% (fully open) is assigned to the opening of the virtual steam supply valve from 0% (fully closed) to 50%, and the opening of the backup steam supply valve 212 from 0% (fully closed) to 100% (fully open) is assigned to the opening of the virtual steam supply valve from 50% to 100% (fully open).
Then, the operating amount for the virtual steam supply valve is calculated using a PID algorithm so that the detected temperature of the hot water storage temperature sensor 41 converges to the target hot water outlet temperature, and an opening degree designation signal is output from the steam supply control unit 130 to each of the actuator circuit of the heating steam supply valve 54 and the actuator circuit of the backup steam supply valve 212.
As a result, when the temperature of the stored water TW in the hot water tank 40 is stable near the target hot water temperature, such as when the bypass water supply valve is closed, the backup steam supply valve 212 is fully closed and the opening degree of the heating steam supply valve 54 is adjusted. On the other hand, when the temperature of the stored hot water in the hot water tank 40 drops significantly, such as when the bypass water supply valve 62 is opened, the heating steam supply valve 54 is fully opened and the opening degree of the backup steam supply valve 212 is adjusted.

This configuration allows steam to be supplied to the hot water tank 40 only when the temperature of the stored water TW in the hot water tank 40 is low. This makes it possible to prevent boiler chemicals such as boiler compounds from being mixed into the hot water tank 40 as much as possible.

The hot water production system 1 of this embodiment described above provides the following advantages in addition to (1) to (10).

(11) The hot water production system 1 of this embodiment is equipped with a backup steam supply line L12 that supplies steam S generated by the steam boiler device 30 to the hot water tank 40, and a backup steam supply valve 212 provided on the backup steam supply line L12, and controls the opening degrees of the heating steam supply valve 54 and the backup steam supply valve 212 so that the detected temperature of the hot water storage temperature sensor 41 becomes the target hot water storage temperature.
This makes it possible to perform heating by direct heat exchange between the hot water and the steam S. This makes it possible to cope with a sudden load change that makes it difficult to maintain the hot water temperature in the hot water tank 40.

(12) In the hot water producing system 1 of this embodiment, the temperature zone for controlling the opening degree of the backup steam supply valve 212 is a lower temperature zone than the temperature zone for controlling the opening degree of the heating steam supply valve 54.
This makes it possible to supply steam to the hot water tank 40 only when the temperature of the hot water in the hot water tank 40 is low. This makes it possible to prevent boiler chemicals such as boiler compound from being mixed into the hot water tank 40 as much as possible.

Third Embodiment
Next, a third embodiment will be described with reference to Fig. 12. Note that the description of the same configuration as the first embodiment will be omitted.
The hot water producing system 1 of the third embodiment further includes a stored water circulation line L13 through which the hot water stored in the hot water tank 40 is circulated, and as a second heating means 3, in addition to the heating heat exchanger 210 shown in the first embodiment (hereinafter referred to as the first heating heat exchanger 210 in this embodiment), a second heating heat exchanger 220 is provided which indirectly exchanges heat between the hot water circulating through the stored water circulation line L13 and steam S.
FIG. 12 is a diagram showing a hot water producing system 1 according to a third embodiment of the present invention.

12, in this embodiment, the hot water tank 40 is provided with a stored water circulation line L13 through which the hot water stored in the hot water tank 40 circulates. The stored water circulation line L13 is provided with a circulation pump 221 for circulating the hot water stored in the hot water tank 40, a second heating heat exchanger 220 for heating the hot water circulating through the stored water circulation line L13, and a return temperature sensor 222 for detecting the temperature of the hot water returning from the second heating heat exchanger 220 to the hot water tank 40.
The second heating heat exchanger 220 is supplied with steam S from the steam boiler device 30, and indirect heat exchange is carried out between the hot water circulating through the stored water circulation line L13 and the steam S from the steam boiler device 30.

In the present embodiment, the heating steam supply line L2 has a second heating heat exchanger 220 and a first heating heat exchanger 210 arranged in series downstream of the heating steam supply valve 54. Therefore, the steam S flowing through the heating steam supply line L2 flows through the second heating heat exchanger 220 and then the first heating heat exchanger 210.
With this configuration, it is possible to supply the water W1 heated by the steam S to the hot water tank 40 while giving priority to keeping the hot water TW stored in the hot water tank 40 warm.

The steam supply control unit 130 of this embodiment controls the opening of the heating steam supply valve 54 so that the temperature detected by the reflux temperature sensor 222 becomes the target reflux temperature. Specifically, the operation amount for the heating steam supply valve 54 is calculated by a PID algorithm so that the temperature detected by the reflux temperature sensor 222 converges to the target reflux temperature, and an opening designation signal is output from the steam supply control unit 130 to the actuator circuit of the heating steam supply valve 54.
This makes it possible to appropriately control the hot water temperature in the hot water tank.

As described above, the hot water producing system 1 of this embodiment is equipped with, as the second heating means 3, a first heating heat exchanger 210, a hot water tank 40 for storing hot water heated by the first heating heat exchanger 210, a stored water circulation line L13 through which the hot water stored in the hot water tank 40 is circulated, a second heating heat exchanger 220 for indirect heat exchange between the hot water circulating through the stored water circulation line L13 and steam, a heating steam supply line L2 for supplying steam S generated in the steam boiler device 30 to the first heating heat exchanger 210 and the second heating heat exchanger 220, and a heating steam supply valve 54 provided in the heating steam supply line L2.
This makes it possible to cope with a sudden load change that makes it difficult to maintain the hot water temperature in the hot water tank 40. In addition, since steam S is not mixed into the hot water tank 40, it is possible to prevent boiler chemicals such as boiler compound from being mixed into the hot water tank 40.

It is preferable that the second heating heat exchanger 220 and the first heating heat exchanger 210 are arranged in series so that steam S flows through them in this order, but these heat exchangers may be arranged in the reverse order.
The second heating heat exchanger 220 and the first heating heat exchanger 210 may be arranged in parallel. In this case, for example, the heating steam supply line L2 is branched midway so that steam S from the steam boiler device 30 can be supplied to each of the second heating heat exchanger 220 and the first heating heat exchanger 210. In this case, a heating steam supply valve may be provided on the line before the branching, or a heating steam supply valve may be provided on each of the lines after the branching.
The heating steam supply valve is controlled based on the detection results of each sensor, such as the reflux temperature sensor 222, the hot water storage temperature sensor 41 (not shown), the first water level sensor, etc. For example, the heating steam supply valve corresponding to the second heating heat exchanger 220 may be controlled based on the temperature detected by the reflux temperature sensor 222. The heating steam supply valve corresponding to the first heating heat exchanger 210 may be controlled based on the temperature detected by the hot water storage temperature sensor 41.

The circulation pump 221 may also be controlled based on the detection results of each sensor, such as the reflux temperature sensor 222, the hot water storage temperature sensor 41 (not shown), and the first water level sensor 42. For example, the drive of the circulation pump 221 may be controlled based on the temperature detected by the hot water storage temperature sensor 41. Specifically, the circulation pump 221 may be driven when the hot water storage temperature sensor 41 is lower than a predetermined temperature. The control of the circulation pump 221 may also be linked to the control of the heating steam supply valve, so that the circulation pump 221 is driven when the heating steam supply valve opens.

In addition, a configuration may be adopted in which a drain recovery line (not shown) is provided between the first heating heat exchanger 210 and/or the second heating heat exchanger 220 and the water supply tank 60, and steam drain generated in the first heating heat exchanger 210 and/or the second heating heat exchanger 220 is recovered in the water supply tank 60.
This allows the steam drain generated in the first heating heat exchanger 210 and/or the second heating heat exchanger 220 to be effectively utilized for preheating the service water supplied to the heat pump hot water supply system 10 and the feed water supplied to the steam boiler device 30, and for water conservation.

The hot water production system 1 of this embodiment described above provides the following advantages in addition to (1) to (10).

(13) In the hot water producing system 1 of this embodiment, the second heating means 3 includes a first heating heat exchanger 210 that indirectly exchanges heat between hot water W1 heated by the water heaters 11, 12, and 13 and steam S, a hot water tank 40 that stores the hot water W1 heated by the first heating heat exchanger 210, a stored water circulation line L13 through which the hot water TW stored in the hot water tank 40 is circulated, a second heating heat exchanger 220 that indirectly exchanges heat between the hot water TW circulating through the stored water circulation line L13 and steam S, a heating steam supply line L2 that supplies steam S generated in the steam boiler device 30 to the first heating heat exchanger 210 and the second heating heat exchanger 220, and a heating steam supply valve 54 provided in the heating steam supply line L2.
This makes it possible to cope with a sudden load change that makes it difficult to maintain the hot water temperature in the hot water tank 40. Also, it is possible to prevent boiler chemicals such as boiler compound from being mixed into the hot water tank 40.

(14) The heating steam supply line L2 of the hot water production system 1 of this embodiment circulates the steam S generated in the steam boiler device 20 through the second heating heat exchanger 220, and then through the first heating heat exchanger 210.
This allows the water W1 heated by the steam S to be supplied to the hot water tank while giving priority to keeping the hot water TW stored in the hot water tank 40 warm.

(15) In the hot water production system 1 of this embodiment, the second heating means 3 is equipped with a return temperature sensor 222 that detects the temperature of the hot water TW returning from the second heating heat exchanger 220 to the hot water tank 40, and the opening of the heating steam supply valve 54 is controlled so that the detected temperature of the return temperature sensor 222 becomes the target return temperature.
This makes it possible to appropriately control the hot water temperature in the hot water tank 40 .

(16) The hot water producing system 1 of this embodiment includes a water supply tank 60 for storing water to be supplied to the water heaters 11, 12, 13 and/or feed water to be supplied to the steam boiler apparatus 30, and a drain recovery line for recovering steam drain generated in the first heating heat exchanger 210 and/or the second heating heat exchanger 220 in the water supply tank 60.
This allows the steam drain generated in the first heating heat exchanger 210 and/or the second heating heat exchanger 220 to be effectively utilized for preheating the water supplied to the water heaters 11, 12, 13 and/or the feed water supplied to the steam boiler device 30, and for water conservation.

Fourth Embodiment
Next, a fourth embodiment will be described with reference to Fig. 13. Note that the description of the same configuration as the first embodiment will be omitted.
The hot water producing system 1 of the fourth embodiment further includes a preheating heat exchanger 75 that performs indirect heat exchange between the service water W5 flowing through the bypass water supply line L5 and the steam S from the steam boiler device 30.
FIG. 13 is a diagram showing a hot water producing system 1 according to a fourth embodiment of the present invention.

As shown in FIG. 13, in this embodiment, a preheating heat exchanger 75 is provided in the bypass water supply line L5. The preheating heat exchanger 75 is an indirect heat exchanger that performs indirect heat exchange between the water (cold water) W5 from the water supply tank 60 supplied through the bypass water supply line L5 and the steam from the steam boiler device 30. The preheating heat exchanger 75 is provided downstream of the bypass water supply valve 62.

The steam supply line 53 (heating steam supply line L2) in this embodiment branches midway, with one branch connected to the heating heat exchanger 210 and the other branch connected to the preheating heat exchanger 75. The line connected to the heating heat exchanger 210 is provided with a heating steam supply valve 54 similar to that in the first embodiment. On the other hand, the line connected to the preheating heat exchanger 75 constitutes the preheating steam supply line L10, and this preheating steam supply line L10 is provided with a preheating steam supply valve 76.

These preheating heat exchanger 75, preheating steam supply line L10, and preheating steam supply valve 76 constitute additional preheating heating means and have the function of heating the water W5 supplied through the bypass water supply line L5.

In this embodiment, the hot water storage control unit 140 controls the preheating steam supply valve 76 in addition to the hot water storage control described in the first embodiment. Specifically, when the bypass water supply valve 62 is opened, the preheating steam supply valve 76 is also opened. This makes it possible to prevent a sudden drop in the temperature of the stored water TW in the hot water tank 40 due to the water W5 supplied through the bypass water supply line L5.

As in the first embodiment, the bypass water supply valve 62 opens when it is detected that the water level WL in the hot water tank 40 has fallen below the water level LL, i.e., when the hot water tank 40 is about to run out of water. This causes the cold water W5 stored in the water supply tank 60 to be directly supplied to the hot water tank 40, preventing the hot water tank 40 from running out of water, but naturally causes the temperature of the stored water TW in the hot water tank 40 to drop.

The preheating heat exchanger 75 in this embodiment is provided to prevent as much as possible a drop in the temperature of the stored water TW in the hot water tank 40 caused by the replenishment of the water W5 through the bypass water supply. That is, when the bypass water supply valve 62 is opened, the preheating steam supply valve 76 is also opened, so that the water W5 supplied to the hot water tank 40 through the bypass water supply line L5 is heated. This makes it possible to increase the temperature of the water W5 when replenishing the water W5 from the bypass water supply line L5 to the hot water tank 40.

In addition, a configuration may be adopted in which a drain recovery line (not shown) is provided between the heating heat exchanger 210 and/or the preheating heat exchanger 75 and the water supply tank 60, and the steam drain generated in the heating heat exchanger 210 and/or the preheating heat exchanger 75 is recovered in the water supply tank 60.
This allows the steam drain generated in the heating heat exchanger 210 and/or the preheating heat exchanger 75 to be effectively utilized for preheating the service water supplied to the heat pump hot water supply system 10 and the feed water supplied to the steam boiler device 30, and for water conservation.

The hot water production system 1 of this embodiment described above provides the following advantages in addition to (1) to (16).

(17) The hot water production system 1 of this embodiment includes a preheating heat exchanger 75 that indirectly exchanges heat between the water W5 flowing through the bypass water supply line L5 and steam, a preheating steam supply line L10 that supplies steam S generated in the steam boiler device 30 to the preheating heat exchanger 75, and a preheating steam supply valve 76 provided on the preheating steam supply line L10, and the preheating steam supply valve 76 is opened when the bypass water supply valve 62 is opened.
This allows the temperature of the make-up water to be increased when water is supplied to the hot water tank 40 from the bypass water supply line L5.

(18) The hot water production system 1 of this embodiment includes a water supply tank 60 that stores water to be supplied to the water heaters 11, 12, and 13 and/or feed water to be supplied to the steam boiler apparatus 30, and a drain recovery line that recovers steam drain generated in the heating heat exchanger 210 and/or the preheating heat exchanger 75 in the water supply tank 60.
This allows the steam drain generated in the heating heat exchanger 210 and/or the preheating heat exchanger 75 to be effectively utilized for preheating the water supplied to the water heaters 11, 12, 13 and/or the feed water supplied to the steam boiler device 30, and for water conservation.

Fifth Embodiment
Next, a fifth embodiment will be described with reference to Figures 14 to 15. Note that the description of the same configuration as the first embodiment will be omitted.
The hot water producing system 1 of the fifth embodiment further includes a switching means 80 that switches the supply destination of the hot water W1 supplied from the water heaters 11, 12, and 13 to the hot water tank 40 or the water supply tank 60.
FIG. 14 is a diagram showing a hot water producing system 1 according to a fifth embodiment of the present invention.

As shown in FIG. 14, in this embodiment, the hot water supply line L1 branches off midway, with one branch connected to the hot water tank 40 via the heating heat exchanger 210 and the other branch connected to the water supply tank 60. The hot water supply line connected to the water supply tank 60 constitutes the water supply tank hot water supply line L11.

Switching valves 81, 82, and 83 are provided as switching means 80 at branching portions of the hot water supply line L1 connected to each of the hot water heaters 11, 12, and 13. These switching valves 81, 82, and 83 function as switching means for switching the supply destination of the hot water supplied from each of the hot water heaters 11, 12, and 13 to the hot water tank 40 side or the water supply tank 60 side.
By providing such a switching means, the supply direction of hot water from each water heater 11, 12, 13 can be switched between the hot water tank 40 side and the water supply tank 60 side as necessary. This also makes it possible to continue the operation of the water heaters 11, 12, 13 as much as possible, and eliminates the problem of low-temperature water supply at the initial stage of restarting the operation of the heat pump water heaters 11, 12, 13.

In this embodiment, a second water supply tank 65 that supplies water to the heat pump water heaters 11, 12, and 13 is provided separately from the water supply tank 60. Water W1 from the second water supply tank 65 is supplied to the water heaters 11, 12, and 13 via a heat pump water supply line L3.

Next, the specific control of the switching valve 81 will be described.
The hot water storage control unit 140 controls the bypass water supply valve 62 and the switching valves 81 , 82 , and 83 based on the detection result of the first water level sensor 42 .
The hot water tank 40 includes a first water level sensor 42 shown in FIG. 4, similarly to the first embodiment.

In this embodiment, the hot water storage control unit 140 opens the bypass water supply valve 62 when the first water level sensor 42 detects that the water level has fallen below the water level LL.
In addition, when the water level in the hot water tank 40 drops, the hot water storage control unit 140 controls the switching valves 81, 82, 83 to increase the number of hot water heaters 11, 12, 13 for the hot water tank 40 by one each time the water level detected by the first water level sensor 42 falls one step below the water level threshold, while simultaneously decreasing the number of hot water heaters 11, 12, 13 for the water supply tank 60 by one; and when the water level in the hot water tank 40 rises, the hot water storage control unit 140 controls the switching valves 81, 82, 83 to decrease the number of hot water heaters 11, 12, 13 for the hot water tank 40 by one each time the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, while simultaneously increasing the number of hot water heaters 11, 12, 13 for the water supply tank 60 by one.
This control is performed, for example, at water level H, water level M, and water level L when the water level is decreasing, and at water level M, water level H, and water level HH when the water level is increasing.
In addition, the hot water storage control unit 140 may control the water heaters 11 , 12 , and 13 and the switching valves 81 , 82 , and 83 via the hot water supply control unit 110 .

Here, using FIG. 15, we will explain, for example, a case where the water level WL in the hot water tank 40 fluctuates. Note that we will not explain the same control as in FIG. 4 of the first embodiment.

First, the control when the water level WL is recovering (see arrow B in FIG. 4) will be described. When the water level WL rises and the tip of the third electrode rod 423 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level M.
At this time, it is determined that there is a little room left in the amount of water stored in the hot water tank 40, and only one of the three switching valves is switched to the water supply tank 60 side. For example, of the switching valves 81, 82, and 83, only the switching valve 83 is switched to the water supply tank 60 side. In other words, the switching means 80 is controlled so as to decrease the number of hot water heaters for the hot water tank 40 by one and simultaneously increase the number of hot water heaters for the water supply tank 60 by one.

Next, when the water level WL rises further and the tip of the fourth electrode rod 424 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level H.
At this time, it is determined that there is more water stored in the hot water tank 40, and two of the three changeover valves are switched to the water supply tank 60 side. For example, of the changeover valves 81, 82, and 83, the changeover valves 82 and 83 are switched to the water supply tank 60 side.

Next, when the water level WL rises further and the tip of the fifth electrode rod 425 is immersed in the water surface, the first water level sensor 42 detects that the water level WL has exceeded the water level HH.
At this time, it is determined that the amount of water stored in the hot water tank 40 has reached a sufficient level, and all three changeover valves 81, 82, 83 are switched to the water supply tank 60 side.

Next, a case where the water level WL starts to drop from this state will be described.
When the water level WL drops (see arrow A in FIG. 4) and the lower end of the fourth electrode rod 424 is exposed above the water surface, the first water level sensor 42 detects that the water level WL has fallen below the water level H.
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level H, it switches one of the three switching valves to the hot water tank 40 side. For example, of the switching valves 81, 82, and 83, it switches the switching valve 81 to the hot water tank 40 side.

If the water level WL rises after it falls below the water level H and the tip of the fifth electrode rod 425 is submerged in the water surface, it is determined that the amount of water stored in the hot water tank 40 is sufficient again, and all the switching valves 81, 82, and 83 are switched to the water supply tank 60 side as described above.

On the other hand, after the water level WL falls below the water level H, when the water level WL falls further (see arrow A in Figure 4) and the lower end of the third electrode rod 423 is exposed from the water surface, the first water level sensor 42 detects that the water level WL has fallen below the water level M.
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level H, it switches two of the three switching valves to the hot water tank 40 side. For example, of the switching valves 81, 82, and 83, the switching valves 81 and 82 are switched to the hot water tank 40 side.

From this state, when the water level WL further drops and the lower end of the second electrode rod 422 is exposed above the water surface, the first water level sensor 42 detects that the water level WL has fallen below the water level L.
When the hot water storage control unit 140 detects that the water level WL has fallen below the water level L, it switches all three switching valves 81, 82, and 83 to the hot water tank 40 side.

As a result, the hot water W1 heated by the first heating means 2 can be switched to the hot water tank 40 or the water supply tank 60 as needed to supply hot water. That is, the hot water W1 heated by the first heating means 2 that does not need to be supplied to the hot water tank 40 can be supplied to the water supply tank 60, which stores water for boiler supply and bypass supply. Therefore, the hot water W1 heated by the first heating means 2 can be used effectively. In addition, by controlling the switching means 80, it is possible to continue operation of the heat pump water heaters 11, 12, and 13 as much as possible, and the problem of low-temperature water supply at the initial stage of restarting the operation of the heat pump can be eliminated.

In order to effectively heat the water for the boiler feed water and the bypass feed water, it is preferable to separate the water supply tank into a water supply tank 60 for storing the water for the boiler feed water and the bypass feed water, and a second water supply tank 65 for storing the water for supply to the heat pump hot water supply system 10, and to supply the hot water W1 heated by the first heating means 2 to the water supply tank 60, but as shown in the first embodiment, the second water supply tank 65 may be shared with the water supply tank 60. In this case, the water supplied to the heat pump hot water supply system 10 is also heated.
In addition, the switching means 80 may be configured to be able to switch the supply destination of the hot water W1 from the water heaters 11, 12, and 13 to the hot water tank 40 or the second water supply tank 65.

As shown in FIG. 10, the hot water storage control unit 140 shifts the number of operating water heaters in a specified water level range (for example, a water level range between water level L and water level M) when the water level rises and when the water level falls. However, as in the first embodiment, instead of shifting the number of operating water heaters in a specified water level range when the water level rises and when the water level falls, a status confirmation time may be set. In other words, the configuration may be such that when it is determined that the water level WL has remained above/below a specified water level threshold for a specified period of time, control such as switching the switching valves 81, 82, and 83 is performed.

Furthermore, in this embodiment, a second water level sensor (not shown) may be provided in the water supply tank 60 to detect the water level in the water supply tank 60, and when the detected water level by the second water level sensor reaches a water supply stop water level, one of the water heaters 11, 12, and 13 that is currently supplying hot water to the water supply tank 60 may be stopped, and when the detected water level reaches a water supply start water level, the water heater that is stopped may be operated.
For example, when the water level WL is rising and exceeds the water level M, and one of the three water heaters, for example water heater 13, is supplying hot water to the water supply tank 60, when the water level detected by the second water level sensor of the water supply tank 60 reaches the water supply stop water level, the operation of the water heater 13 is stopped. Then, when the water level detected by the second water level sensor reaches the water supply start water level, the operation of the water heater 13 that had been stopped is resumed.
This allows the water level in the water supply tank 60 to be appropriately managed.

The hot water production system 1 of this embodiment described above provides the following advantages in addition to (1) to (18).

(19) The hot water producing system 1 of this embodiment includes a water supply tank 60 for storing water to be supplied to the water heaters 11, 12, and 13 and/or water supply to the steam boiler apparatus 30, and a switching means for switching the supply destination of the hot water W1 supplied from the water heaters 11, 12, and 13 to the hot water tank 40 or the water supply tank 60.
This allows hot water W1 supplied from water heaters 11, 12, and 13 to be switched to hot water tank 40 or water supply tank 60 as needed. Also, by making the switchable, it is possible to continue operation of the heat pump as long as possible, and the problem of low-temperature water supply at the initial stage of restarting operation of the heat pump can be eliminated.
(20) The hot water producing system 1 of this embodiment includes a first water level sensor 42 that detects the water level in the hot water tank 40, and the first heating means 2 includes a plurality of water heaters 11, 12, and 13. The hot water tank 40 has a plurality of water level thresholds set therein for changing the number of hot water heaters 11, 12, and 13. When the water level in the hot water tank 40 drops, the number of hot water heaters 11, 12, and 13 for the hot water tank 40 is reduced by one each time the water level detected by the first water level sensor 42 falls below the water level threshold by one step. When the water level in the hot water tank 40 rises, the switching means 80 is controlled so that the number of hot water heaters 11, 12, 13 for the hot water tank 40 is decreased by one each time the water level detected by the first water level sensor 42 exceeds the water level threshold by one step, and at the same time, the switching means 80 is controlled so that the number of hot water heaters 11, 12, 13 for the water tank 60 is increased by one each time the water level detected by the first water level sensor 42 exceeds the water level threshold by one step.
This allows water to be supplied by switching between the hot water tank 40 and the water supply tank 60 as needed. In addition, by controlling the switching means 80, it is possible to continue operation of the heat pump as long as possible, and this makes it possible to solve the problem of low-temperature water supply at the initial stage of restarting the operation of the heat pump.

(21) The hot water production system 1 of this embodiment is equipped with a second water level sensor that detects the water level in the water supply tank 60, and when the water level detected by the second water level sensor reaches the water supply stop water level, the water heater that is supplying hot water to the water supply tank 60 is stopped, and when the detected water level reaches the water supply start water level, the water heater that is stopped is operated.
This allows the water level in the water supply tank 60 to be appropriately managed.

Although the above describes each preferred embodiment of the hot water production system of the present invention, the present invention is not limited to the above-mentioned embodiments and can be modified as appropriate. It is also possible to combine multiple embodiments.

1...hot water production system 2...first heating means 3...second heating means 10...heat pump type hot water supply system 11...first heat pump type hot water heater 12...second heat pump type hot water heater 13...third heat pump type hot water heater 14, 15, 16...hot water temperature sensor 17, 18, 19...water supply pump 30...steam boiler device 31...once-through boiler 40...hot water tank 41...hot water storage temperature sensor 42...first water level sensor 421...first electrode rod 422...second electrode rod 423...third electrode rod 424...fourth electrode rod 425... 5 electrode rod 51...steam header 52...connecting line 53...steam supply line 54...heating steam supply valve 55...pressure gauge 60...water supply tank 62...bypass water supply valve 75...preheating heat exchanger 76...preheating steam supply valve 80...switching means 81, 82, 83...switching valve 90...heat pump circuit 91...refrigerant compressor 92...condenser 93...expansion valve 94...evaporator 100...control unit 110...hot water supply control unit 120...boiler control unit 130...steam supply control unit 140...hot water storage control unit 210...heating heat exchanger (first heating heat exchanger)
212...Backup steam supply valve 220...Second heating heat exchanger L1...Hot water supply line L2...Heating steam supply line L3...Heat pump water supply line L4...Boiler water supply line L5...Bypass water supply line L6...Hot water outlet line L7...Refrigerant circulation line L8...Heat source water supply line L10...Preheating steam supply line L12...Backup steam supply line L13...Stored water circulation line W1...Water (hot water)
W5: Water (cold water)
W6: Hot water S: Steam R: Refrigerant TW: Hot water, stored water WL: Water level

Claims (15)

A first heating means for heating the water to a target hot water temperature while passing the water through the heat pump type hot water heater;
a second heating means for indirectly exchanging heat with the water heated to the target hot water supply temperature by the first heating means, the second heating means generating steam in a steam boiler and adjusting the steam pressure to a target hot water outlet temperature set higher than the target hot water supply temperature;
A control means for controlling the first heating means and the second heating means,
The second heating means is
a heating heat exchanger for indirectly exchanging heat between the hot water heated by the water heater and the steam generated by the steam boiler;
A hot water tank for storing hot water heated by the heating heat exchanger;
a hot water temperature sensor for detecting the temperature of the hot water in the hot water tank;
The control means adjusts the output sharing between the water heater and the steam boiler so that the temperature detected by the hot water storage temperature sensor becomes the set target hot water outlet temperature. The second heating means is
a steam header that collects steam generated in the steam boiler;
a heating steam supply valve for adjusting the amount of steam supplied from the steam header,
The control means
a boiler control unit that controls the steam boiler so that a header pressure of the steam header becomes the target steam pressure;
2. The hot water producing system according to claim 1, further comprising a steam supply control unit that controls the heating steam supply valve so that the temperature detected by the hot water storage temperature sensor becomes the set target hot water outlet temperature. The second heating means is
a first water level sensor for detecting a water level in the hot water tank;
a heating steam supply line for supplying steam generated in the steam boiler to the heating heat exchanger;
A heating steam supply valve provided in the heating steam supply line,
The first heating means is
A water supply line for supplying water to the water heater;
A hot water supply line that supplies hot water heated by the hot water heater to the heating heat exchanger;
a hot water temperature sensor for detecting a hot water temperature of the hot water flowing through the hot water supply line;
The control means
when the water level detected by the first water level sensor falls below a first set water level during a drop in the water level in the hot water tank, the supply of water through the water supply line and the supply of hot water through the hot water supply line are started;
when the water level detected by the first water level sensor exceeds a second set water level that is higher than the first set water level during a water level rise in the hot water tank, the supply of water through the water supply line and the supply of hot water through the hot water supply line are stopped;
When the water supply is in progress,
Controlling the water heater so that the temperature detected by the hot water temperature sensor becomes the target hot water temperature;
2. The hot water producing system according to claim 1, wherein an opening degree of the heating steam supply valve is controlled so that the temperature detected by the hot water storage temperature sensor becomes the target hot water outlet temperature. a bypass water supply line for supplying water to the hot water tank without passing through the water heater;
A bypass water supply valve provided in the bypass water supply line;
a backup steam supply line for supplying steam generated by the steam boiler to the hot water tank;
A backup steam supply valve provided in the backup steam supply line,
The control means
When the water level in the hot water tank drops and the detected water level of the first water level sensor falls below a third set water level that is lower than the first set water level, the bypass water supply valve is opened, and the opening degree of the heating steam supply valve and the backup steam supply valve is controlled so that the detected temperature of the hot water storage temperature sensor becomes the target hot water outlet temperature,
4. The hot water producing system according to claim 3, wherein when the water level in the hot water tank rises and the detected water level of the first water level sensor exceeds a fourth set water level that is higher than the third set water level, the bypass water supply valve is closed. The hot water production system according to claim 4, wherein the temperature zone for controlling the opening degree of the backup steam supply valve is a lower temperature zone than the temperature zone for controlling the opening degree of the heating steam supply valve. a bypass water supply line for supplying water to the hot water tank without passing through the water heater;
A bypass water supply valve provided in the bypass water supply line;
A circulation line through which the hot water stored in the hot water tank is circulated;
an auxiliary heat exchanger for indirectly exchanging heat between the hot water and steam circulating through the circulation line;
a return temperature sensor for detecting a temperature of the hot water returning from the auxiliary heat exchanger to the hot water tank;
the heating-use steam supply line supplies steam generated in the steam boiler to the heating-use heat exchanger and the auxiliary heat exchanger,
The control means
When the water level in the hot water tank drops and the detected water level of the first water level sensor falls below a third set water level that is lower than the first set water level, the bypass water supply valve is opened, and the opening degree of the heating steam supply valve is controlled so that the detected temperature of the return flow temperature sensor becomes the target hot water outlet temperature.
4. The hot water producing system according to claim 3, wherein when the water level in the hot water tank rises and the detected water level of the first water level sensor exceeds a fourth set water level that is higher than the third set water level, the bypass water supply valve is closed. The hot water production system according to claim 6, wherein the heating steam supply line circulates the steam generated in the steam boiler to the auxiliary heat exchanger, and then to the heating heat exchanger. a bypass water supply line for supplying water to the hot water tank without passing through the water heater;
A bypass water supply valve provided in the bypass water supply line;
a preheating heat exchanger for indirectly exchanging heat between the water flowing through the bypass water supply line and steam;
a preheating steam supply line for supplying steam generated in the steam boiler to the preheating heat exchanger;
A preheating steam supply valve provided in the preheating steam supply line,
The control means
When the water level in the hot water tank drops, if the detected water level of the first water level sensor falls below a third set water level that is lower than the first set water level, the bypass water supply valve is opened and the preheating steam supply valve is opened.
4. The hot water producing system according to claim 3, wherein when the water level in the hot water tank rises and the detected water level of the first water level sensor exceeds a fourth set water level that is higher than the third set water level, the bypass water supply valve is closed. The first heating means includes a plurality of the water heaters,
A plurality of water level thresholds are set in the hot water tank for changing the number of the water heaters in operation;
The control means
When the water level in the hot water tank is decreasing, a number control is executed to increase the number of the water heaters in operation by one each time the water level detected by the first water level sensor falls below the water level threshold by one step;
A hot water producing system as described in any one of claims 3 to 8, wherein when the water level in the hot water tank rises, a number control is performed to reduce the number of operating water heaters by one each time the detected water level of the first water level sensor exceeds the water level threshold by one step. The first heating means includes a plurality of the water heaters,
A plurality of water level thresholds are set in the hot water tank for changing the number of the hot water heaters in operation and/or the target hot water temperature;
The water heater is capable of switching a target hot water supply temperature among a plurality of stages within a temperature range higher than a first temperature and lower than the target hot water outlet temperature,
The control means
When the target hot water temperature of the water heater is set to the first temperature and the detected water level of the first water level sensor exceeds the water level threshold by one step, control is executed to increase the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters; when the target hot water temperature of the water heater is increased by one step or more and the detected water level of the first water level sensor exceeds the water level threshold by one step, control is executed to reduce the number of operating water heaters by one and at the same time return the target hot water temperature to the first temperature, or control is executed to increase the target hot water temperature of the water heater by another step while maintaining the number of operating water heaters;
A hot water production system as described in any of claims 3 to 8, wherein, during operation with the target hot water temperature of the water heater set to the first temperature, when the water level detected by the first water level sensor falls one step below the water level threshold, control is executed to increase the number of operating water heaters by one and at the same time raise the target hot water temperature of the water heater by one or more steps, and, during operation with the target hot water temperature of the water heater raised by one or more steps, when the water level detected by the first water level sensor falls one step below the water level threshold, control is executed to lower the target hot water temperature of the water heater by one step while maintaining the number of operating water heaters. a water supply tank for storing water to be supplied to the water heater and/or water to be supplied to the steam boiler;
The hot water producing system according to any one of claims 3 to 10, further comprising a switching means for switching a supply destination of the hot water supplied from the water heater to the hot water tank or the water supply tank. The first heating means includes a plurality of the water heaters,
The hot water tank is provided with a plurality of water level thresholds for changing the number of hot water heaters;
The control means
When the water level in the hot water tank is decreasing, the switching means is controlled so that the number of hot water heaters for the hot water tank is increased by one each time the water level detected by the first water level sensor falls below the water level threshold by one step, and at the same time, the number of hot water heaters for the water supply tank is decreased by one each time;
The hot water producing system of claim 11, wherein when the water level in the hot water tank rises, the switching means controls so as to reduce the number of hot water heaters for the hot water tank by one each time the detected water level of the first water level sensor exceeds the water level threshold by one step, while at the same time increasing the number of hot water heaters for the water supply tank by one. a second water level sensor for detecting a water level in the water supply tank;
The control means
The hot water producing system of claim 11 or claim 12, wherein when the detected water level of the second water level sensor reaches a water supply stop water level, the water heater that is supplying hot water to the water tank is stopped, and when the detected water level reaches a water supply start water level, the water heater that is stopped is operated. a water supply tank for storing water to be supplied to the water heater and/or water to be supplied to the steam boiler;
The hot water producing system according to any one of claims 3 to 13, further comprising: a drain recovery line that recovers steam drain generated in the heating heat exchanger and returns it to the water supply tank. A first heating step of heating the water to a target hot water temperature while passing the water through the heat pump water heater;
a second heating step of indirectly exchanging heat with steam generated by a steam boiler and adjusted to a target steam pressure, the second heating step heating the water heated to the target hot water supply temperature in the first heating step to a target hot water outlet temperature set higher than the target hot water supply temperature;
The second heating step includes storing the heated hot water in a hot water tank by indirect heat exchange between the hot water heated by the water heater and the steam generated by the steam boiler in a heating heat exchanger, and detecting the temperature of the hot water in the hot water tank with a hot water storage temperature sensor;
A hot water production method that adjusts the output distribution of the water heater and the steam boiler so that the detected temperature of the hot water storage temperature sensor becomes the set target hot water outlet temperature when the first heating process and the second heating process are performed.

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