JP2022172656A - Underground heat utilization system, control device, control method, and program - Google Patents

Abstract

To provide an underground heat utilization system, a control device, a control method, and a program that facilitate the control of water injecting temperature under a low load.SOLUTION: An underground heat utilization system comprises a water pumping well, a water injecting well, a pipe extending to the water injecting well from the water pumping well, a pump capable of supplying groundwater to the water injecting well from the water pumping well via the pipe, a heat exchanger provided in the pipe, a control valve provided in the pipe, and capable of regulating the flow rate of the groundwater in the pipe, and a control device for regulating the flow rate of the groundwater to be injected into the water injecting well by controlling the control valve so as to reduce the flow rate in the pipe when the operating frequency of inverter control of the pump becomes the lowest frequency.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a geothermal heat utilization system, a control device, a control method, and a program.

In recent years, geothermal heat utilization systems have been proposed that use groundwater as a heat source or a cold heat source.

For example, Patent Literature 1 proposes a geothermal heat utilization system that includes a pumping well and an injection well, pumps up groundwater from the pumping well, and exchanges heat with a load side using a heat exchanger. Such a geothermal heat utilization system stores heat by injecting groundwater that has passed through a heat exchanger into a well.

JP 2018-173256 A

In the geothermal heat utilization system disclosed in Patent Literature 1, in order to keep the temperature of water injected into the water injection well constant, it is necessary to reduce the water injection flow rate at low load.
However, when inverter control is performed in the pump disclosed in Patent Document 1, it may be difficult to control the water injection temperature at low loads when the water injection flow rate is smaller than the water injection flow rate at the lowest frequency of inverter control.

The present disclosure has been made to solve the above problems, and aims to provide a geothermal heat utilization system, a control device, a control method, and a program that make it easy to control the water injection temperature at low load.

In order to solve the above problems, the geothermal heat utilization system according to the present disclosure includes a pumped well, a water injection well, a pipe extending from the pumped well to the water well, and from the pumped well through the pipe. A pump capable of supplying groundwater to a water injection well, a heat exchanger provided in the pipe, a control valve provided in the pipe and capable of adjusting the flow rate of the groundwater in the pipe, and inverter control of the pump and a control device that adjusts the flow rate of the groundwater injected into the water injection well by controlling the control valve so as to throttle the flow rate in the pipe when the operating frequency of becomes the lowest frequency.

The control device according to the present disclosure is an inverter control of a pump that feeds the groundwater from the pumping well to the injection well according to the temperature of the groundwater that is pumped up from the pumping well and injected into the injection well through the heat exchanger. a pump operation control unit that adjusts an operating frequency; and a control valve opening/closing control unit that adjusts the opening degree of the control valve.

The control method according to the present disclosure is an inverter control of a pump that feeds the groundwater from the pumping well to the water injection well according to the temperature of the groundwater that is pumped up from a water pumping well and injected into the water injection well through a heat exchanger. Adjusting the operating frequency, and opening a control valve provided in a pipe for sending the groundwater to the water injection well according to the temperature of the groundwater to be injected into the water injection well when the operation frequency becomes the lowest frequency. adjust the degree.

A program according to the present disclosure is stored in a computer, according to the temperature of groundwater that is pumped up from a pumping well and injected into the injection well via a heat exchanger, an inverter of a pump that sends the groundwater from the pumping well to the injection well. A control valve provided in a pipe that adjusts a control operating frequency and feeds the groundwater into the water injection well according to the temperature of the groundwater that is injected into the water injection well when the operation frequency becomes the lowest frequency. to execute a method for adjusting the opening of the

According to the geothermal heat utilization system, the control device, the control method, and the program of the present disclosure, it is easy to control the water injection temperature at low load.

1 is a diagram showing a schematic configuration of a geothermal heat utilization system according to an embodiment of the present disclosure; FIG. 1 is a diagram showing a schematic configuration of a geothermal heat utilization system and a load equipment side according to an embodiment of the present disclosure; FIG. 1 is a system diagram of a geothermal heat utilization system according to an embodiment of the present disclosure; FIG. FIG. 4 is a diagram showing the flow of groundwater and medium when the load equipment side operates in the cooling mode in the geothermal heat utilization system according to the embodiment of the present disclosure. FIG. 4 is a diagram showing the flow of groundwater and medium when the load facility side operates in heating mode in the geothermal heat utilization system according to the embodiment of the present disclosure. 1 is a block diagram of a control device according to an embodiment of the present disclosure; FIG. FIG. 4 is a diagram showing the flow of groundwater and medium when the load equipment side operates in the cooling tower mode in the geothermal heat utilization system according to the embodiment of the present disclosure. FIG. 4 is a diagram showing the flow of groundwater and medium when the load equipment side operates in the refrigerator mode in the geothermal heat utilization system according to the embodiment of the present disclosure. 4 is a flow chart showing procedures of a control method according to an embodiment of the present disclosure; It is a figure showing an example of hardware constitutions of a computer with which a control device concerning an embodiment of this indication is provided.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. The same reference numerals are given to the same or corresponding configurations in all the drawings, and common explanations are omitted.

<Embodiment>
An embodiment of a geothermal heat utilization system according to the present disclosure will be described with reference to FIGS. 1 to 9. FIG.
(Configuration of geothermal heat utilization system)
As shown in FIGS. 1 to 3, the geothermal heat utilization system 1 includes a plurality of wells 2, piping 3, a heat exchanger 4, a temperature adjustment system 7 (see FIG. 3), and a pump 31. Prepare the Lord.

(Composition of the well)
As shown in FIG. 1, a plurality of wells 2 extend from above ground OG into aquifer LY.
For example, the plurality of wells 2 comprises a first well 2A and a second well 2B.
The underground heat utilization system 1 draws up groundwater from one of the first well 2A and the second well 2B, and after heat exchange with the heat exchanger 4, Groundwater after heat exchange is injected into the other. In other words, the geothermal heat utilization system 1 has two functions, one for pumping up groundwater from the first well 2A and pouring it into the second well 2B, and the other for pumping up groundwater from the second well 2B and pouring it into the first well 2A. It has a driving mode.
Here, in the following description, of the first well 2A and the second well 2B, the side from which groundwater is pumped up is referred to as a pumping well 21, and of the first well 2A and the second well 2B, the side to which groundwater is injected is water injection. It is called well 22 . That is, the first well 2A and the second well 2B may function as pumping wells 21 and may function as water injection wells 22, respectively.
However, in order to simplify the explanation below, the case where the first well 2A is the pumping well 21, the second well 2B is the water injection well 22, and the heat exchanger 4 performs heat exchange will be mainly explained.

Each well 2 comprises a casing 2a embedded in a borehole HOL drilled from the surface OG to the aquifer LY underground.
The casing 2a has a tubular shape extending in the vertical direction.

Each well 2 has an opening 2c at the top.
For example, opening 2c may be an opening in the top of casing 2a.

The casing 2a has a strainer 2b made up of, for example, a plurality of slits.
The strainer 2b allows the well 2 to take groundwater from the aquifer LY into the casing 2a and return the groundwater from the casing 2a to the aquifer LY.
For example, as shown in FIG. 3, a well cover 6 may be provided in the upper opening of the casing 2a to close the opening.

(Composition of piping and pump)
As shown in FIGS. 1 and 3, the pipe 3 extends inside the well 2 .
For example, both ends of the pipe 3 may be immersed in the ground water of the pumping well 21 and the pouring well 22 so as to connect the pumping well 21 and the pouring well 22 .
For example, one end of the pipe 3 is provided in the pumping well 21 and the other end of the pipe 3 is provided in the pumping well 22 so that the groundwater pumped by the pump 31 can flow from the pumping well 21 toward the water injection well 22 . may be provided in

A pump 31 is provided in the pipe 3 .
A pump 31 pumps water from the well 2 to the pipe 3 .
For example, the pump 31 pumps water from the well 2 to the pipe 3 when the well 2 functions as the pumping well 21 .
For example, pump 31 may pump groundwater in well 2 into pipe 3 .
For example, the pumps 31 may be provided at both ends of the pipe 3 and immersed in the ground water in each well 2 .
For example, the pump 31 may be able to change its output by inverter control.

A water injection valve 32 is provided in the pipe 3 .
The water injection valves 32 are provided at both ends of the pipe 3, respectively.
The water injection valves 32 may be arranged between the pumps 31 at both ends of the pipe 3 and the heat exchangers 4 .
For example, the water injection valve 32 may be immersed in groundwater within each well 2 .
The water injection valve 32 injects groundwater in the pipe 3 .
For example, when the well 2 functions as the water injection well 22, the water injection valve 32 injects the groundwater in the pipe 3 into the well 2 (the water injection well 22).
The water injection valve 32 is opened when the pressure inside the pipe 3 becomes higher than the set pressure, and the groundwater inside the pipe 3 is injected into the water injection well 22 .

As shown in FIG. 3, the piping 3 includes check valves 35a to 35d between the heat exchanger 4 and the pumping well 21 and the water injection well 22. As shown in FIG.
The check valves 35a to 35d are arranged so that the groundwater flows in the same direction to the heat exchanger 4 regardless of whether the groundwater is pumped up from the pumping well 21 or the water injection well 22. , controls the flow of groundwater in the pipe 3 .

For example, when groundwater is pumped up from the first well 2A, the groundwater in the pipe 3 flows from the first well 2A through the check valve 35a, the heat exchanger 4, and the check valve 35b in order, and then to the second well 2B. Water is injected. At this time, since the pressure in the pipe 3 is higher on the upstream side (first well 2A side) than the downstream side of the heat exchanger 4, water does not flow through the check valves 35c and 35d.
Similarly, when pumping up from the second well 2B, the groundwater in the pipe 3 passes through the check valve 35c, the heat exchanger 4, and the check valve 35d in order from the second well 2B and is injected into the first well 2A. be done. At this time as well, water does not flow through the check valves 35a and 35b because the pressure in the pipe 3 is higher on the upstream side (first well 2A side) of the heat exchanger 4 than on the downstream side.

(Configuration of heat exchanger)
The heat exchanger 4 exchanges heat between the groundwater in the pipe 3 and the medium on the load equipment 100 side.
For example, the heat exchanger 4 exchanges heat between the groundwater pumped up from the well 2 and flowing through the piping 3 and the medium on the load equipment 100 side. After the heat exchange, the groundwater flows from the heat exchanger 4 through the piping 3 and is injected into the well 2 .
For example, the heat exchanger 4 may be provided in the middle of the pipe 3 on the ground OG.

When the water that has passed through the heat exchanger 4 is hot water, the geothermal heat utilization system 1 performs hot water heat storage by injecting hot water into the well 2 .
When the water that has passed through the heat exchanger 4 is cold water, the geothermal heat utilization system 1 stores cold water heat by injecting cold water into the well 2 .
Here, "hot water" means water with a temperature higher than the initial temperature of the groundwater in the aquifer, and "cold water" means water with a temperature lower than the initial temperature of the groundwater in the aquifer. That is.
For example, the initial ground temperature of groundwater in an aquifer is 18°C.

(Configuration of load equipment)
As shown in FIG. 2 , the load facility 100 uses a medium that has undergone heat exchange with groundwater in the pipe 3 in the heat exchanger 4 .
The load equipment 100 is, for example, an air conditioning system that includes a heat source machine 110 and an air conditioner 120 .
For example, the heat source device 110 may be a heat pump equipped with a condenser, an evaporator, a compressor, and the like.
The air conditioner 120 performs air conditioning of the space in which the air conditioner 120 is installed by exchanging heat with the medium supplied from the heat source device 110 .
For example, the load facility 100 can be switched between a cooling mode and a heating mode as an air conditioning system.
The load equipment 100 has a piping system 101 for forming a medium flow between the heat exchanger 4, the heat source equipment 110, and the air conditioner 120 according to each operation mode. The piping system 101 is appropriately provided with on-off valves (not shown), and the medium is routed between the heat exchanger 4, the heat source device 110, and the air conditioner 120 according to each operation mode of the air conditioning system. circulate with

In this embodiment, the load equipment 100 may further include a cooling tower 130 and a second heat exchanger 140 .

The cooling tower 130 cools the cooling water with heat of vaporization when the cooling water is brought into contact with the air and vaporized. Cooling tower 130 circulates cooling water to and from second heat exchanger 140 .
The second heat exchanger 140 exchanges heat between the medium of the piping system 101 on the air conditioning system side and the cooling water on the cooling tower 130 side.
The second heat exchanger 140 cools the medium in the piping system 101 on the air conditioning system side by heat exchange with the cooling water cooled by the cooling tower 130 .
The configuration and application of the load equipment 100 are not limited to those described above, and can be changed as appropriate.

As shown in FIG. 4 , when cooling operation is performed on the load equipment 100 side and hot water heat storage is performed in the injection well 22 , the second well 2B is the pumping well 21 and the first well 2A is the injection well 22 . The groundwater is pumped up by the pump 31 of the second well 2B which becomes the pumping well 21 and sent to the heat exchanger 4. - 特許庁The heat exchanger 4 exchanges heat between the groundwater in the pipe 3 and the medium flowing through the pipe system 101 on the load equipment 100 side. On the load equipment 100 side, the medium cooled by heat exchange in the heat exchanger 4 is sent to the heat source equipment 110 and heat-exchanged in the heat source equipment 110 . Accordingly, the air conditioner 120 connected to the heat source device 110 can cool the room. On the other hand, the medium heated by the heat exchange in the heat source equipment 110 is sent again to the heat exchanger 4 and circulated. The heat exchanger 4 heats the groundwater by exchanging heat between the heated medium and the groundwater flowing through the pipe 3 . The geothermal heat utilization system 1 stores hot water heat by injecting heated groundwater into the water injection well 22 through the pipe 3 .

As shown in FIG. 5 , when heating operation is performed on the load equipment 100 side and cold water heat storage is performed in the water injection well 22 , the first well 2A is the pumping well 21 and the second well 2B is the water injection well 22 . The pump 31 of the first well 2A serving as the pumping well 21 draws up groundwater and feeds it into the heat exchanger 4. - 特許庁The heat exchanger 4 exchanges heat between the groundwater in the pipe 3 and the medium flowing through the pipe system 101 on the load equipment 100 side. On the load equipment 100 side, the medium heated by heat exchange in the heat exchanger 4 is sent to the heat source equipment 110 and heat-exchanged in the heat source equipment 110 . Accordingly, the air conditioner 120 connected to the heat source device 110 can heat the room. On the other hand, the medium cooled by heat exchange in the heat source equipment 110 is sent to the heat exchanger 4 again and circulated. The heat exchanger 4 exchanges heat between the cooled medium and the groundwater flowing through the pipe 3, thereby cooling the groundwater. The geothermal heat utilization system 1 stores cold water heat by injecting cooled groundwater into the water injection well 22 through the pipe 3 .

(Configuration of temperature control system)
As shown in FIG. 3, the temperature regulation system 7 includes a pump controller 71, a control valve 72, and a control device 80. The temperature adjustment system 7 adjusts the water injection temperature of the water injection well 22 by adjusting the flow rate of the groundwater that is injected into the water injection well 22 .

A pump controller 71 controls the operation of the pump 31 .
For example, a pump controller 71 may be provided associated with each well 2 pump 31 .
For example, the pump controller 71 has an inverter circuit (not shown) and performs inverter control of the pump 31 .
The pump controller 71 adjusts the rotation speed of the pump 31 by varying the operating frequency of the inverter control by the inverter circuit under the control of the control device 80, which will be described later.
The pump controller 71 adjusts the rotation speed of the pump 31 by varying the operating frequency of the inverter control by the inverter circuit, and adjusts the flow rate of groundwater injected into the injection well 22 from the pipe 3 via the heat exchanger 4 .
Hereinafter, the inverter-controlled operating frequency of the pump 31 is also referred to as "the operating frequency of the pump 31".

A control valve 72 is provided in the pipe 3 .
For example, a control valve 72 may be provided between each well 2 and heat exchanger 4 .
For example, in this embodiment, the control valve 72 may be provided closer to the water injection well 22 than the heat exchanger 4 .
The control valve 72 can adjust the flow rate of groundwater in the pipe 3 .
The control valve 72 adjusts the flow rate of groundwater in the pipe 3 by opening and closing the flow path in the pipe 3 .
The control valve 72 adjusts the flow rate of groundwater in the pipe 3 by adjusting the degree of opening thereof.
The control valve 72 adjusts the flow rate of groundwater in the pipe 3 under the control of the control device 80 .
The control valve 72 adjusts the degree of opening when the operating frequency of the pump 31 drops to the lowest frequency.
For example, the minimum frequency depends on the type of pump and may vary by pump manufacturer.

(Configuration of control device)
The controller 80 adjusts the flow rate of groundwater injected into the injection well 22 .
The control device 80 adjusts the operating frequency of the pump 31 and the opening degree of the control valve 72 so that the temperature of the groundwater injected into the injection well 22 is constant.
The control device 80 adjusts only the operating frequency of the pump 31 in a region where the operating frequency of the pump 31 is equal to or higher than the lowest frequency, thereby adjusting the flow rate of the groundwater injected into the water injection well 22 .
For example, controller 80 may be controllably connected to each pump controller 71 .
For example, controller 80 may be controllably connected to each control valve 72 .
For example, when the operating frequency of the pump 31 drops to the lowest frequency, the controller 80 adjusts the opening of the control valve 72 to adjust the flow rate of groundwater injected into the injection well 22 .
When the operating frequency of the pump 31 drops to the lowest frequency, the control device 80 narrows (reduces) the opening of the control valve 72 to reduce the flow rate of the groundwater injected into the injection well 22 .
For example, the control device 80 reduces the operating frequency of the pump 31 to the lowest frequency and adjusts the flow rate of groundwater injected into the water injection well 22 by adjusting the opening of the control valve 72. It may be kept at the lowest frequency.
Further, when the opening degree of the control valve 72 is reduced to a preset minimum opening degree, the control device 80 performs heat exchange with the medium on the side of the load equipment 100 cooled in the cooling tower 130 in the heat exchanger 4. to adjust the flow rate of the groundwater injected from the pipe 3 to the injection well 22 .

As shown in FIG. 6 , the control device 80 includes a pump operation control section 81 , a control valve opening/closing control section 82 and a load side flow path control section 83 .

The pump operation control unit 81 adjusts the rotation speed of the pump 31 by varying the operating frequency of inverter control by the inverter circuit of the pump controller 71 .
The pump operation control unit 81 adjusts the operating frequency of the pump 31 for pumping the groundwater from the pumping well 21 according to the temperature of the groundwater injected into the water injection well 22 .
The pump operation control unit 81 adjusts the flow rate of groundwater injected from the pipe 3 into the injection well 22 by varying the operating frequency of the pump 31 based on a map or the like stored in advance.
For example, when the load facility 100 performs the cooling operation and the hot water heat storage is performed in the water injection well 22, the pump operation control unit 81 determines the difference between the actual injection temperature of the groundwater injected into the water injection well 22 from the pipe 3 and the set temperature. The operating frequency of pump 31 is controlled based on the difference.
For example, when the load facility 100 performs heating operation and cold water heat storage is performed in the water injection well 22, the pump operation control unit 81 determines the difference between the actual injection temperature of the groundwater injected into the water injection well 22 from the pipe 3 and the set temperature. The operating frequency of pump 31 is controlled based on the difference.
The pump operation control unit 81 controls the pump controller 71 so as to adjust the operating frequency (output) of the pump 31 according to the required water injection temperature based on a map or the like stored in advance.
The pump operation control unit 81 stores, for example, the lower limit of the operating frequency at which the pump 31 can stably operate as the lowest frequency. The pump operation control section 81 controls the pump controller 71 so as to adjust the operation of the pump 31 in a frequency range equal to or higher than a preset minimum frequency.

The control valve opening/closing control unit 82 adjusts the flow rate of groundwater in the pipe 3 by opening and closing the control valve 72 .
The control valve opening/closing control unit 82 adjusts the flow rate of groundwater in the pipe 3 by adjusting the opening degree of the control valve 72 .
The control valve opening/closing control unit 82 adjusts the opening degree of the control valve 72 when the operating frequency of the pump 31 has decreased to the lowest frequency.
The control valve opening/closing control unit 82 adjusts the opening degree of the control valve 72 according to the temperature of the groundwater injected into the injection well 22 when the operating frequency of the pump 31 becomes the lowest frequency.

The load-side flow path control unit 83 controls the flow of the medium in the load equipment 100 by switching valves and the like provided in the piping system 101 on the load equipment 100 side.
The load-side flow path control unit 83 controls the flow of the medium in the piping system 101 according to each operation mode such as cooling mode and heating mode.
When the opening degree of the control valve 72 reaches the preset minimum set opening degree and the injected water temperature does not reach the set temperature, the load side flow path control unit 83 changes the operation mode of the load equipment 100 side to the cooling tower mode described later. switch to
When the opening degree of the control valve 72 reaches the preset minimum setting opening degree in a state where the operating frequency of the pump 31 has decreased to the lowest frequency, the load side flow path control unit 83 changes the operation mode of the load facility 100 side. to cooling tower mode.
In the cooling tower mode, the medium cooled by the cooling water of the cooling tower 130 and the groundwater heat-exchanged by the heat exchanger 4 are injected into the injection well 22 .
Furthermore, the load-side flow path control unit 83 may switch the operation mode of the load equipment 100 side to a refrigerator mode, which will be described later.

As shown in FIG. 7, cooling tower mode may be utilized to cool groundwater for cold water heat storage.
In the cooling tower mode, the load equipment 100 sends the cooling water cooled by the heat of vaporization when it is vaporized in contact with the atmosphere in the cooling tower 130 to the second heat exchanger 140 . The second heat exchanger 140 exchanges heat between the cooling water and the medium of the piping system 101 . That is, in the second heat exchanger 140 , the cooling water cooled by the cooling tower 130 cools the medium in the piping system 101 . The cooled medium is sent to the heat exchanger 4 and exchanges heat with the underground water in the pipe 3 . As a result, the groundwater in the pipe 3 is cooled and injected into the injection well 22 to store cold water heat.

Also, as shown in FIG. 8, a refrigerator mode may be used to cool groundwater for cold water heat storage.
In the refrigerator mode, the load facility 100 uses the cooling tower 130 and the heat source machine 110 as refrigerators. In this case, the pump 31 of the first well 2A serving as the pumping well 21 draws up groundwater and feeds it into the heat exchanger 4 . The heat exchanger 4 exchanges heat between the groundwater in the pipe 3 and the medium flowing through the piping system 101 on the side of the load equipment 100 to cool the groundwater. On the load equipment 100 side, the medium heated by heat exchange in the heat exchanger 4 is sent to the heat source equipment 110 . The heat source equipment 110 connected to the cooling tower 130 via the second heat exchanger 140 cools the heated medium by heat exchange. The medium cooled by heat exchange in the heat source equipment 110 is sent to the heat exchanger 4 again and circulated. The heat exchanger 4 exchanges heat between the cooled medium and the groundwater flowing through the pipe 3, thereby cooling the groundwater. The geothermal heat utilization system 1 stores cold water heat by injecting cooled groundwater into the water injection well 22 through the pipe 3 .

The operation of the control device 80 of this embodiment will be described.
The operation of the control device 80 corresponds to an embodiment of the control method.
The control device 80 implements each step shown in FIG.

First, when the load equipment 100 side is operating in the cooling mode or the heating mode, the pump operation control unit 81 pumps water according to the set temperature of the groundwater injected into the water injection well 22 through the heat exchanger 4. The operating frequency of the inverter control of the pump 31 that feeds the groundwater from the well 21 to the water injection well 22 is adjusted (ST01: step of adjusting the operating frequency of the pump). As a result, the flow rate of water injected from the pumped well 21 to the water injection well 22 by the pump 31 is adjusted.

Following the execution of ST01, the pump operation control unit 81 determines whether or not the operating frequency of the inverter control of the pump 31 has decreased to the lowest frequency (ST02: Whether or not the operating frequency of the pump has decreased to the lowest frequency). a step of determining whether or not).

As a result of the determination in ST02, if the inverter-controlled operating frequency of the pump 31 has not decreased to the lowest frequency, the process returns to ST01, and the pump operation control unit 81 determines the water injection flow rate from the pumped well 21 to the water injection well 22 by the pump 31. continue to adjust
As a result of the determination in ST02, if the operating frequency of the inverter control of the pump 31 has decreased to the lowest frequency, the control valve opening/closing control unit 82 adjusts the control valve 72 is adjusted in the closing direction (ST03: step of adjusting the opening of the control valve). The control valve opening/closing control unit 82 adjusts the amount of water injected into the water injection well 22 by adjusting the opening degree of the control valve 72 . At this time, the inverter-controlled operating frequency of the pump 31 maintains the lowest frequency. That is, by closing the control valve 72 while the operating frequency of the inverter control of the pump 31 is the lowest frequency, the control device 80 further reduces the flow rate of the groundwater injected into the injection well 22 .

Following the execution of ST03, the control valve opening/closing control unit 82 determines whether or not the opening of the control valve 72 is the preset minimum opening (ST04: the opening of the control valve reaches the minimum setting). step of determining whether or not it is open).
As a result of the determination in ST04, if the degree of opening of the control valve 72 is not the minimum set degree of opening, the process returns to ST03, and the control valve opening/closing control section 82 continues the processing.
As a result of the determination in ST04, if the opening degree of the control valve 72 is the minimum set opening degree, the load side flow path control section 83 switches the operation mode of the load equipment 100 side to the cooling tower mode (ST05: load equipment side to the cooling tower mode). In the cooling tower mode, the geothermal heat utilization system 1 injects the medium cooled by the cooling water of the cooling tower 130 and the groundwater heat-exchanged by the heat exchanger 4 into the water injection well 22 . As a result, the groundwater in the pipe 3 is cooled and injected into the water injection well 22 to perform cold water heat storage.
For example, when cold water heat storage in the cooling tower mode cannot be performed due to high atmospheric temperature, the control device 80 may switch to the refrigerator mode and perform cold water heat storage in the refrigerator mode.

(Action and effect)
According to this embodiment, the geothermal heat utilization system 1 sends groundwater pumped up from the well 21 by the pump 31 to the heat exchanger 4 through the pipe 3 . Geothermal heat is utilized by exchanging heat between the groundwater and the medium on the load facility 100 side in the heat exchanger 4 . Groundwater that has passed through the heat exchanger 4 is injected into the water injection well 22 through the pipe 3 . The pump 31 adjusts the flow rate of the groundwater sent through the pipe 3 by inverter control. When the operating frequency of the inverter control of the pump 31 becomes the lowest frequency set in advance, the geothermal heat utilization system 1 throttles the flow rate in the pipe 3 by the control valve 72 to reduce the flow rate at the lowest frequency of the pump 31. It becomes possible to inject groundwater into the water injection well 22 at a flow rate smaller than that. As a result, the geothermal heat utilization system 1 can easily control the water injection temperature during low load.

Further, according to one example of this embodiment, the control valve 72 is provided closer to the water injection well 22 than the heat exchanger 4 .
Thereby, the geothermal heat utilization system 1 can control the water injection flow rate near the water injection well 22 . Therefore, the geothermal heat utilization system 1 can easily control the water injection temperature of the water injection well 22 .

Further, according to one example of the present embodiment, when the control device 80 adjusts the flow rate of groundwater in the pipe 3 by throttling the control valve 72, the operating frequency of the inverter control of the pump 31 is kept at the lowest frequency.
In this way, in a state where the control valve 72 is throttled to adjust the flow rate of the groundwater, by keeping the operating frequency of the inverter control of the pump 31 at the lowest frequency, the geothermal heat utilization system 1 can reduce the flow rate by the control valve 72. Adjustments can be made efficiently.

Further, according to one example of the present embodiment, when the opening degree of the control valve 72 reaches the minimum set opening degree, the control device 80 separates the medium cooled by the cooling water of the cooling tower 130 and the groundwater in the pipe 3. Groundwater that has been heat-exchanged and cooled by the heat exchanger 4 is injected into the injection well 22 .
When the degree of opening of the control valve 72 reaches the minimum set degree of opening, the flow rate of groundwater injected into the injection well 22 cannot be lowered any further. In such a case, by using the cooling tower 130 , the geothermal heat utilization system 1 can further adjust the temperature of the groundwater injected into the injection well 22 . As a result, the geothermal heat utilization system 1 can control the injection water temperature in a wider range during low load.

Further, according to one example of the present embodiment, the control device 80 includes a pump operation control section 81 and a control valve opening/closing control section 82 .
According to this control device 80 , the pump operation control section 81 adjusts the operating frequency of the inverter control of the pump 31 according to the temperature of the groundwater injected into the injection well 22 . By adjusting the flow rate of the groundwater injected into the injection well 22 , the controller 80 can adjust the temperature of the groundwater injected into the injection well 22 . When the operating frequency of the inverter control of the pump 31 becomes the preset minimum frequency, the control valve opening/closing control unit 82 adjusts the opening degree of the control valve 72 to reduce the flow rate in the pipe 3, thereby It is possible to inject groundwater into the injection well 22 at a flow rate less than that at the lowest frequency of 31 . This makes it easier for the control device 80 to control the injection water temperature when the load is low.

<Modification>
In the above-described embodiment, the program for realizing various functions of the control device 80 is recorded in a computer-readable recording medium, and the program recorded in this recording medium is read by a computer system such as a microcomputer. , to perform various processes. Here, various processes of the CPU of the computer system are stored in a computer-readable recording medium in the form of programs, and the above various processes are performed by reading and executing the programs by the computer. Computer-readable recording media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.

An example of the hardware configuration of the computer 190 that executes programs for realizing various functions of the control device 80 in the above embodiment will be described.

As shown in FIG. 10, a computer 190 provided in the control device 80 includes a processor 195, a memory 196, a storage/reproduction device 197, an Input Output Interface (hereinafter referred to as "IO I/F") 198, and communication and an Interface (hereinafter referred to as “communication I/F”) 199 .

For example, processor 195 may be a CPU.
For example, the memory 196 may be a medium such as a Random Access Memory (hereinafter referred to as “RAM”) that temporarily stores data used by programs executed by the control device 80 .
For example, the storage/playback device 197 may be a device for storing data or the like in external media such as a CD-ROM, DVD, or flash memory, or playing back data or the like from the external media.
For example, the IO I/F 198 may be an interface for inputting/outputting information between the control device 80 and another device.
For example, the communication I/F 199 may be an interface that performs communication between the control device 80 and another device via a communication line such as the Internet or a dedicated communication line.

<Other embodiments>
Although the embodiment of the present disclosure has been described above, the embodiment is shown as an example and is not intended to limit the scope of the present disclosure. This embodiment can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the gist of the present disclosure. This embodiment and its modifications are intended to be included in the scope and equivalents of the present disclosure as well as included in the scope and gist of the present disclosure.

<Appendix>
The geothermal heat utilization system 1, the control device 80, the control method, and the program described in the embodiment are grasped as follows, for example.

(1) The geothermal heat utilization system 1 according to the first aspect includes a pumped well 21, a water injection well 22, a pipe 3 extending from the pumped well 21 to the water injection well 22, and through the pipe 3, the A pump 31 capable of feeding groundwater from a pumping well 21 to the water injection well 22, a heat exchanger 4 provided in the pipe 3, and a heat exchanger 4 provided in the pipe 3 to adjust the flow rate of the groundwater in the pipe 3. When the operating frequency of the control valve 72 and the inverter control of the pump 31 becomes the lowest frequency, the control valve 72 is controlled to reduce the flow rate in the pipe 3, so that water is injected into the water injection well 22. and a control device 80 that adjusts the flow rate of the groundwater.

This geothermal heat utilization system 1 sends groundwater pumped up from a well 21 by a pump 31 to a heat exchanger 4 through a pipe 3 . Geothermal heat is utilized by exchanging heat between the groundwater and the medium on the load facility 100 side in the heat exchanger 4 . Groundwater that has passed through the heat exchanger 4 is injected into the water injection well 22 through the pipe 3 . The pump 31 adjusts the flow rate of the groundwater sent through the pipe 3 by inverter control. When the operating frequency of the inverter control of the pump 31 becomes the lowest frequency set in advance, the geothermal heat utilization system 1 throttles the flow rate in the pipe 3 by the control valve 72 to reduce the flow rate at the lowest frequency of the pump 31. It becomes possible to inject groundwater into the water injection well 22 at a flow rate smaller than that. As a result, the geothermal heat utilization system 1 can easily control the water injection temperature during low load.

(2) A geothermal heat utilization system 1 according to a second aspect is the geothermal heat utilization system 1 of (1), in which the control valve 72 is provided closer to the water injection well 22 than the heat exchanger 4. It is

Thereby, the geothermal heat utilization system 1 can control the water injection flow rate near the water injection well 22 . Therefore, the geothermal heat utilization system 1 can easily control the water injection temperature of the water injection well 22 .

(3) A geothermal heat utilization system 1 according to a third aspect is the geothermal heat utilization system 1 of (1) or (2), wherein the control device 80 throttles the control valve 72 so that the When regulating the flow of the groundwater in pipe 3, the operating frequency is kept at the lowest frequency.

In this way, in a state where the control valve 72 is throttled to adjust the flow rate of the groundwater, by keeping the operating frequency of the inverter control of the pump 31 at the lowest frequency, the geothermal heat utilization system 1 can reduce the flow rate by the control valve 72. Adjustments can be made efficiently.

(4) The geothermal heat utilization system 1 according to the fourth aspect is the geothermal heat utilization system 1 according to any one of (1) to (3), and A cooling tower 130 is provided on the side of the load facility 100 that uses a medium that exchanges heat with the groundwater, and the control device 80 cools by the cooling tower 130 when the opening of the control valve 72 reaches the minimum set opening. The groundwater that has undergone heat exchange in the heat exchanger 4 and the medium thus obtained is injected into the injection well 22 .

When the degree of opening of the control valve 72 reaches the minimum set degree of opening, the flow rate of groundwater injected into the injection well 22 cannot be lowered any further. In such a case, by using the cooling tower 130 , the geothermal heat utilization system 1 can further adjust the temperature of the groundwater injected into the injection well 22 . As a result, the geothermal heat utilization system 1 can control the injection water temperature in a wider range during low load.

(5) The control device 80 according to the fifth aspect controls the temperature of the groundwater pumped from the pumping well 21 and injected into the water injection well 22 via the heat exchanger 4. and a pump operation control unit 81 that adjusts the operating frequency of the inverter control of the pump 31 that feeds the groundwater, and the temperature of the groundwater that is injected into the water injection well 22 when the operating frequency becomes the lowest frequency. and a control valve opening/closing control unit 82 that adjusts the opening degree of a control valve 72 provided in the pipe 3 for feeding the groundwater to the water injection well 22 .

According to this control device 80 , the pump operation control section 81 adjusts the operating frequency of the inverter control of the pump 31 according to the temperature of the groundwater injected into the injection well 22 . By adjusting the flow rate of the groundwater injected into the injection well 22 , the controller 80 can adjust the temperature of the groundwater injected into the injection well 22 . When the operating frequency of the inverter control of the pump 31 becomes the preset minimum frequency, the control valve opening/closing control unit 82 adjusts the opening degree of the control valve 72 to reduce the flow rate in the pipe 3, thereby It is possible to inject groundwater into the injection well 22 at a flow rate less than that at the lowest frequency of 31 . This makes it easier for the control device 80 to control the injection water temperature when the load is low.

(6) In the control method according to the sixth aspect, according to the temperature of the groundwater that is pumped up from the pumping well 21 and injected into the water injection well 22 via the heat exchanger 4, Adjusting the operating frequency of the inverter control of the pump 31 that feeds the groundwater, and when the operating frequency becomes the lowest frequency, according to the temperature of the groundwater that is poured into the water well 22, the water well 22 The opening degree of the control valve 72 provided in the pipe 3 for feeding the groundwater is adjusted.

This control method adjusts the operating frequency of the inverter control of the pump 31 according to the temperature of the groundwater injected into the injection well 22 . Thereby, the temperature of the groundwater injected into the water injection well 22 can be adjusted by adjusting the flow rate of the groundwater. When the operating frequency of the inverter control of the pump 31 becomes the preset minimum frequency, the control method is to reduce the flow rate in the pipe 3 by adjusting the opening degree of the control valve 72, thereby reducing the minimum frequency of the pump 31. It is possible to inject groundwater into the injection well 22 at a flow rate smaller than that in . This makes it easier for the control method to control the injection water temperature at low load.

(7) The program according to the seventh aspect is stored in the computer 190 according to the temperature of the groundwater that is pumped up from the pumping well 21 and injected into the water injection well 22 via the heat exchanger 4. The operating frequency of the inverter control of the pump 31 for feeding the groundwater to the well 22 is adjusted, and when the operating frequency becomes the lowest frequency, the water injection is performed according to the temperature of the groundwater injected into the water injection well 22. A method of adjusting the opening degree of the control valve 72 provided in the pipe 3 for sending the groundwater to the well 22 is executed.

According to this program, the computer 190 adjusts the inverter-controlled operating frequency of the pump 31 according to the temperature of the groundwater injected into the injection well 22 . Thereby, the temperature of the groundwater injected into the water injection well 22 can be adjusted by adjusting the flow rate of the groundwater. When the operating frequency of the inverter control of the pump 31 reaches the preset minimum frequency, the computer 190 adjusts the opening degree of the control valve 72 to reduce the flow rate in the pipe 3, thereby reducing the minimum frequency of the pump 31. It is possible to inject groundwater into the injection well 22 at a flow rate smaller than that in . This makes it easier for the program to control the injection water temperature at low loads.

1 Geothermal heat utilization system 2 Well 2A First well 2B Second well 2a Casing 2b Strainer 2c Opening 3 Piping 4 Heat exchanger 6 Well lid 7 Temperature control system 21 Pumping well 22... Water injection well 31... Pump 32... Water injection valves 35a to 35d... Check valve 71... Pump controller 72... Control valve 80... Control device 81... Pump operation control unit 82... Control valve opening/closing control unit 83... Load side flow path control Part 100... Load facility 101... Piping system 110... Heat source equipment 120... Air conditioner 130... Cooling tower 140... Second heat exchanger 190... Computer 195... Processor 196... Memory 197... Storage/reproduction device 198... IO I/F
199...Communication I/F
HOL: Borehole LY: Aquifer OG: Ground level ST01: Step for adjusting the operating frequency of the pump ST02: Step for determining whether or not the operating frequency of the pump has decreased to the minimum frequency ST03: Adjusting the degree of opening of the control valve Step ST04: Step ST05 for determining whether or not the opening of the control valve is the minimum set opening: Step for switching the operation mode of the load facility to the cooling tower mode

Claims (7)

pumping wells and
an injection well;
a pipe extending from the pumping well to the water injection well;
a pump capable of sending groundwater from the pumping well to the water injection well through the pipe;
a heat exchanger provided in the pipe;
A control valve provided in the pipe and capable of adjusting the flow rate of the groundwater in the pipe;
A control device that adjusts the flow rate of the groundwater injected into the injection well by controlling the control valve to reduce the flow rate in the pipe when the operating frequency of the inverter control of the pump becomes the lowest frequency. and a geothermal heat utilization system. The geothermal heat utilization system according to claim 1, wherein the control valve is provided closer to the water injection well than the heat exchanger. when the controller adjusts the flow rate of the groundwater in the pipe by throttling the control valve, keeping the operating frequency at the lowest frequency;
The geothermal heat utilization system according to claim 1 or 2. A cooling tower is provided on the load facility side using a medium that exchanges heat with the groundwater in the pipe in the heat exchanger,
When the degree of opening of the control valve reaches the minimum set degree of opening, the control device injects the medium cooled by the cooling tower and the groundwater heat-exchanged by the heat exchanger into the water injection well. Item 4. The geothermal heat utilization system according to any one of Items 1 to 3. Pump operation control for adjusting the operating frequency of the inverter control of the pump that feeds the groundwater from the pumping well to the injection well according to the temperature of the groundwater pumped from the pumping well and injected into the injection well through the heat exchanger. Department and
A control valve that adjusts the degree of opening of a control valve provided in a pipe that feeds the groundwater into the water injection well according to the temperature of the groundwater that is injected into the water injection well when the operating frequency becomes the lowest frequency. and an opening/closing control unit. Adjusting the operating frequency of the inverter control of the pump that conveys the groundwater from the pumping well to the injection well according to the temperature of the groundwater that is pumped from the pumping well and injected into the injection well through the heat exchanger;
adjusting the opening degree of a control valve provided in a pipe feeding the groundwater into the water injection well according to the temperature of the groundwater injected into the water injection well when the operating frequency becomes the lowest frequency; . to the computer,
Adjusting the operating frequency of the inverter control of the pump that conveys the groundwater from the pumping well to the injection well according to the temperature of the groundwater that is pumped from the pumping well and injected into the injection well through the heat exchanger;
A method of adjusting the degree of opening of a control valve provided in a pipe that feeds the groundwater into the water injection well according to the temperature of the groundwater that is injected into the water injection well when the operating frequency becomes the lowest frequency. program to run.

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