Ground thermal energy system, control device, control method, and program

Abstract

A ground thermal energy system (1) according to the present disclosure includes a well (2), piping (3) including an end portion on a side extending toward the well (2) , and a heat exchanger (4) provided to the piping (3) . The piping (3) includes , at the end portion , a pump pipe (71) connected to a pump (72) configured to pump groundwater in the well (2) , and a plurality of water injection pipes (75) each provided with a flow control valve (77).

Description

Geothermal energy utilization system, control device, control method, and program

[0001] This disclosure relates to a geothermal energy utilization system, a control device, a control method, and a program. This application claims priority to Japanese Patent Application No. 2021-78634, filed May 6, 2021, the contents of which are incorporated herein by reference.

[0002] BACKGROUND ART In recent years, geothermal energy utilization systems that utilize groundwater as a heat or cold source have been proposed.

[0003] For example, Patent Document 1 proposes a groundwater heat exchange device in which a lift pipe and a reduction pipe are inserted into each of two wells, groundwater from one well is pumped up through the lift pipe, and the groundwater, after being used for heat, is injected into the other well through the reduction pipe.

[0004] JP 2011-21804 A

[0005] In the groundwater heat exchange device disclosed in Patent Document 1, in order to maintain a constant temperature of the water injected into the water injection well, it is necessary to adjust the water injection flow rate according to the load, outside temperature, etc. However, in the configuration disclosed in Patent Document 1, the water injection flow rate is adjusted only by the pump, and it is desirable to make the adjustment of the water injection flow rate even easier.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a geothermal energy utilization system, a control device, a control method, and a program that make it easier to adjust flow rate.

[0007] In order to solve the above problems, the geothermal energy utilization system of the present disclosure comprises a well, a pipe having an end extending to the well, and a heat exchanger provided on the pipe, and the pipe has at its end a pumping pipe connected to a pump capable of pumping groundwater in the well, and multiple water injection pipes each equipped with a flow control valve.

[0008] The control device according to the present disclosure includes a pump operation control unit that operates a pump provided on a pumping pipe provided on one of a pair of wells to pump groundwater from the pumping pipe, and a valve opening control unit that adjusts the opening of flow control valves provided on each of a plurality of water injection pipes provided on the other well so that the groundwater pumped from the pumping pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through a plurality of water injection pipes provided on the other well.

[0009] The control method disclosed herein operates a pump installed on a riser pipe installed in one of a pair of wells to pump groundwater from the riser pipe, and adjusts the opening of flow control valves installed on each of multiple water injection pipes installed in the other well so that the groundwater pumped from the riser pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through multiple water injection pipes installed in the other well.

[0010] The program disclosed herein causes a computer to execute a method of operating a pump installed on a pumping pipe installed in one of a pair of wells to pump groundwater from the pumping pipe, and adjusting the opening of flow control valves installed on each of multiple water injection pipes installed in the other well so that the groundwater pumped from the pumping pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through multiple water injection pipes installed in the other well.

[0011] The geothermal energy utilization system, control device, control method, and program disclosed herein can facilitate flow rate adjustment.

[0012] Fig. 1 is a diagram showing a schematic configuration of a geothermal energy utilization system according to an embodiment of the present disclosure; Fig. 2 is a system diagram of a geothermal energy utilization system according to an embodiment of the present disclosure; Fig. 3 is a block diagram of a control device according to an embodiment of the present disclosure; Fig. 4 is a flowchart showing the procedure of a control method according to an embodiment of the present disclosure; Fig. 5 is a diagram showing an example of the hardware configuration of a computer included in the control device according to an embodiment of the present disclosure.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In all drawings, the same or corresponding components are denoted by the same reference numerals, and common descriptions will be omitted.

[0014] <Embodiment> An embodiment of a geothermal utilization system according to the present disclosure will be described with reference to Figures 1 to 4. (Configuration of geothermal utilization system) As shown in Figures 1 and 2, a geothermal utilization system 1 mainly includes a well 2, piping 3, a heat exchanger 4, and a flow rate adjustment system 7. For example, the geothermal utilization system 1 may include a pair of wells 2.

[0015] (Well Configuration) As shown in FIG. 1 , a pair of wells 2 extend from the ground OG into the aquifer LY. For example, the pair of wells 2 includes a first well 2A and a second well 2B. The geothermal heat utilization system 1 pumps groundwater from one of the first well 2A and the second well 2B, exchanges heat in a heat exchanger 4, and then injects the heat-exchanged groundwater into the other of the first well 2A and the second well 2B. In other words, the geothermal heat utilization system 1 has two operating modes: one in which groundwater is pumped from the first well 2A and injected into the second well 2B, and one in which groundwater is pumped from the second well 2B and injected into the first well 2A. In the following description, the first well 2A or the second well 2B that pumps groundwater will be referred to as the pumping well 21, and the first well 2A or the second well 2B that injects groundwater will be referred to as the injection well 22. That is, the first well 2A and the second well 2B may function as a pumping well 21 or as a water injection well 22. However, in the following, for the sake of simplicity, the explanation will be centered on the case where the first well 2A is used as the pumping well 21 and the second well 2B is used as the water injection well 22, and heat exchange is performed in the heat exchanger 4.

[0016] Each well 2 includes a casing 2a embedded in a borehole HOL drilled underground from the surface OG to the aquifer LY. The casing 2a is cylindrical and extends in the vertical direction.

[0017] Each well 2 has an opening 2c at its top. For example, the opening 2c may be an opening at the top of the casing 2a.

[0018] The casing 2a has a strainer 2b consisting 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 groundwater from the inside of the casing 2a to the aquifer LY. For example, a well cover (not shown) that closes the opening at the top of the casing 2a may be provided.

[0019] (Piping configuration) As shown in Figures 1 and 2, the piping 3 has an end on the side extending to the well 2. The piping 3 is equipped with a water lifting pipe 71 and multiple water injection pipes 75 at the end. For example, the piping 3 may be equipped with a water lifting pipe 71 and multiple water injection pipes 75 at the end on the side extending to each of the pair of wells 2. For example, in this embodiment, the piping 3 is equipped with a water lifting pipe 71 and multiple water injection pipes 75 at each end on both sides of the pair of wells 2. In other words, the piping 3 is equipped with a water lifting pipe 71 and multiple water injection pipes 75 at the end 3a on the first well 2A side and the end 3b on the second well 2B side, respectively. The water lifting pipe 71 and multiple water injection pipes 75 are branched off from the ends 3a and 3b of the piping 3, respectively.

[0020] The pumping pipe 71 extends from the ground OG into the inside of the well 2. Both ends of the pumping pipe 71 may be immersed in the groundwater of the well 2. When the well 2 on the side where the pumping pipe 71 is installed functions as the pumping well 21, the pumping pipe 71 pumps groundwater from the well 2 (pumping well 21).

[0021] A pump 72 is provided on the lift pipe 71. The pump 72 pumps water from the well 2 to the pipe 3. For example, when the well 2 functions as a pumping well 21, the pump 72 pumps water from the well 2 to the pipe 3. For example, the pump 72 may pump groundwater in the well 2 into the pipe 3. For example, the pump 72 may be provided on the lift pipe 71 and immersed in the groundwater in each well 2. For example, the output of the pump 72 may be changed by inverter control.

[0022] A check valve 73 is provided in the riser pipe 71. The check valve 73 is provided on the riser pipe 71 closer to the heat exchanger 4 than the pump 72. The check valve 73 is provided on the pump 72 side than the connection between the riser pipe 71 and the ends 3a and 3b of the piping 3. When water is injected from the piping 3 through the water injection pipe 75 into the well 2 on the side where the check valve 73 is provided, the check valve 73 prevents some of the injected groundwater from flowing back into the pump 72.

[0023] At the ends 3a and 3b of the piping 3 on the side of each well 2 (first well 2A, second well 2B), multiple water injection pipes 75 each extend from the ground OG into the well 2. Both ends of each water injection pipe 75 may be immersed in the groundwater of the well 2. In this embodiment, for example, two water injection pipes 75 are provided. Three or more water injection pipes 75 may be provided. When the well 2 in which the multiple water injection pipes 75 are provided functions as a water injection well 22, the multiple water injection pipes 75 inject groundwater into the well 2 (water injection well 22).

[0024] The multiple water injection pipes 75 may have different pipe diameters. In this embodiment, the multiple water injection pipes 75 include a small-diameter water injection pipe 75A and a large-diameter water injection pipe 75B. The small-diameter water injection pipe 75A has a smaller pipe diameter than the large-diameter water injection pipe 75B. The large-diameter water injection pipe 75B has a larger pipe diameter than the small-diameter water injection pipe 75A. The small-diameter water injection pipe 75A and the large-diameter water injection pipe 75B may each have a smaller pipe diameter than the riser pipe 71. The small-diameter water injection pipe 75A and the large-diameter water injection pipe 75B may be configured so that the sum of the flow path cross-sectional area of ​​the small-diameter water injection pipe 75A and the flow path cross-sectional area of ​​the large-diameter water injection pipe 75B is equal to or greater than the flow path cross-sectional area of ​​the riser pipe 71.

[0025] Each of the multiple water injection pipes 75 is provided with a flow rate adjustment valve 77. A small diameter flow rate adjustment valve 77A is provided as the flow rate adjustment valve 77 in the small diameter water injection pipe 75A. A large diameter flow rate adjustment valve 77B is provided as the flow rate adjustment valve 77 in the large diameter water injection pipe 75B. The small diameter flow rate adjustment valve 77A has a smaller diameter than the large diameter flow rate adjustment valve 77B. The small diameter flow rate adjustment valve 77A has a diameter that matches the pipe diameter of the small diameter water injection pipe 75A. The large diameter flow rate adjustment valve 77B has a diameter that matches the pipe diameter of the large diameter water injection pipe 75B.

[0026] The flow rate control valve 77 adjusts the flow rate of groundwater flowing through the water injection pipe 75. When the well 2 functions as the water injection well 22, the flow rate control valve 77 adjusts the flow rate of groundwater flowing through the water injection pipe 75 provided in the water injection well 22. The flow rate control valve 77 can adjust the flow rate of groundwater in the water injection pipe 75 provided with the flow rate control valve 77 by adjusting its opening degree. When the operation of the geothermal energy utilization system 1 is to be stopped, the flow rate control valve 77 may be configured to stop the operation of the pump 72 after fully closing the flow rate control valve 77. This allows the geothermal energy utilization system 1 to stop operation while maintaining the groundwater in the pipe 3 in a pressurized state.

[0027] The valve opening degree can be adjusted independently for each of the multiple flow rate control valves 77 provided on the multiple water injection pipes 75. The flow rate control valve 77 of one of the multiple water injection pipes 75 may be closed, and water may be injected into the well 2 on the water injection side only from the other water injection pipe 75.

[0028] 2, the piping 3 is provided with check valves 35a to 35d between the heat exchanger 4 and the pair of wells 2. The check valves 35a to 35d control the flow of groundwater in the piping 3 so that the groundwater flows in the same direction toward the heat exchanger 4 regardless of whether the groundwater is pumped from the first well 2A or the second well 2B.

[0029] For example, when groundwater is pumped from the first well 2A, the groundwater in the pipe 3 passes from the first well 2A through the check valve 35a, the heat exchanger 4, and the check valve 35b, in that order, before being poured into the second well 2B. At this time, the pressure in the pipe 3 is higher upstream of the heat exchanger 4 (the first well 2A side) than downstream, so water does not flow through the check valves 35c and 35d. Similarly, when groundwater is pumped from the second well 2B, the groundwater in the pipe 3 passes from the second well 2B through the check valve 35c, the heat exchanger 4, and the check valve 35d, in that order, before being poured into the first well 2A. At this time, the pressure in the pipe 3 is higher upstream of the heat exchanger 4 (the second well 2B side) than downstream, so water does not flow through the check valves 35a and 35b.

[0030] (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 in the pipe 3 and the medium on the load equipment 100 side. After the heat exchange, the groundwater flows from the heat exchanger 4 through the pipe 3 and is injected into the well 2. For example, the heat exchanger 4 may be provided midway along the pipe 3 above ground OG.

[0031] If the water that has passed through the heat exchanger 4 is hot water, the geothermal energy utilization system 1 stores hot water heat by injecting hot water into the well 2. If the water that has passed through the heat exchanger 4 is cold water, the geothermal energy utilization system 1 stores cold water heat by injecting hot water into the well 2. Here, "hot water" refers to water with a temperature higher than the initial underground temperature of the groundwater in the aquifer, and "cold water" refers to water with a temperature lower than the initial underground temperature of the groundwater in the aquifer. For example, the initial underground temperature of the groundwater in the aquifer is 18°C.

[0032] (Configuration of Flow Rate Control System) The flow rate control system 7 includes a pump controller 74, the flow rate control valve 77, and a control device 80. The flow rate control system 7 adjusts the temperature of the groundwater injected into the water injection well 22 by adjusting the flow rate of the groundwater injected into the water injection well 22.

[0033] The pump controller 74 controls the operation of the pump 72. For example, the pump controller 74 may be provided in association with the pump 72 of each well 2. For example, the pump controller 74 has an inverter circuit (not shown) and performs inverter control of the pump 72. The pump controller 74 adjusts the rotation speed of the pump 72 by varying the operating frequency of the inverter control by the inverter circuit under the control of a control device 80 described below. The pump controller 74 adjusts the rotation speed of the pump 72 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 operating frequency of the inverter control of the pump 72 will also be referred to as the "operating frequency of the pump 72."

[0034] (Configuration of the control device) The control device 80 adjusts the flow rate of groundwater injected into the water injection well 22. The control device 80 adjusts the operating frequency of the pump 72 and the aperture of the flow control valve 77 so that the temperature of the groundwater injected into the water injection well 22 remains constant. In a region where the operating frequency of the pump 72 is equal to or higher than a predetermined minimum frequency, the control device 80 adjusts the flow rate of groundwater injected into the water injection well 22 by adjusting only the operating frequency of the pump 72. For example, the control device 80 may be controllably connected to each pump controller 74.

[0035] For example, the control device 80 may be controllably connected to each flow rate control valve 77. For example, when the operating frequency of the pump 72 drops to the minimum frequency, the control device 80 adjusts the aperture of the flow rate control valve 77 to adjust the flow rate of groundwater injected into the water injection well 22. When the operating frequency of the pump 72 drops to the minimum frequency, the control device 80 reduces the flow rate of groundwater injected into the water injection well 22 by throttling (reducing) the aperture of the flow rate control valve 77. For example, when the operating frequency of the pump 72 drops to the minimum frequency and the control device 80 is adjusting the flow rate of groundwater injected into the water injection well 22 by adjusting the aperture of the flow rate control valve 77, the control device 80 may maintain the operating frequency of the pump 72 at the minimum frequency.

[0036] For example, when the operating frequency of the pump 72 is lowered to the minimum frequency and the groundwater flow rate to the well 2 on the water injection side is smaller than a predetermined flow rate setting reference value, the control device 80 may open only the flow rate control valve 77 provided on the small diameter water injection pipe 75A of the two water injection pipes 75.

[0037] As shown in FIG. 3 , the control device 80 includes a pump operation control unit 81 and a valve opening control unit 82 .

[0038] The pump operation control unit 81 adjusts the rotation speed of the pump 72 by varying the operating frequency of the inverter control by the inverter circuit of the pump controller 74. The pump operation control unit 81 adjusts the operating frequency of the pump 72, which pumps groundwater from the pumping well 21, depending on 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 water injection well 22 by varying the operating frequency of the pump 72 based on a pre-stored map or the like. For example, when cooling operation is performed on the load equipment 100 side and hot water thermal storage is performed in the water injection well 22, the pump operation control unit 81 controls the operating frequency of the pump 72 based on the difference between the actual injection temperature of the groundwater injected from the pipe 3 into the water injection well 22 and the set temperature. For example, when heating operation is performed on the load equipment 100 side and cold water thermal storage is performed in the water injection well 22, the pump operation control unit 81 controls the operating frequency of the pump 72 based on the difference between the actual injection temperature of the groundwater injected from the pipe 3 into the water injection well 22 and the set temperature. The pump operation control unit 81 controls the pump controller 74 to adjust the operating frequency (output) of the pump 72 according to the required temperature of injected water based on a pre-stored map or the like. The pump operation control unit 81 stores, for example, the lower limit of the operating frequency at which the pump 72 can operate stably as the minimum frequency. The pump operation control unit 81 controls the pump controller 74 to adjust the operation of the pump 72 in a frequency range equal to or higher than the preset minimum frequency.

[0039] The valve opening control unit 82 adjusts the flow rate of groundwater in the pipe 3 by opening and closing the flow rate control valve 77. The valve opening control unit 82 adjusts the opening rate of the flow rate control valve 77 to adjust the flow rate of groundwater in the pipe 3. The valve opening control unit 82 adjusts the opening rate of the flow rate control valve 77 when the operating frequency of the pump 72 drops to the minimum frequency. When the operating frequency of the pump 72 drops to the minimum frequency, the valve opening control unit 82 adjusts the opening rate of the flow rate control valve 77 in accordance with the temperature of the groundwater injected into the water injection well 22.

[0040] In this embodiment, when the operating frequency of the pump 72 has dropped to its lowest frequency and the flow rate of groundwater into the water-injection well 2 is smaller than a predetermined reference flow rate, the valve aperture control unit 82 opens only the small-diameter flow control valve 77A provided on the small-diameter water injection pipe 75A of the two water injection pipes 75, and injects water only from the small-diameter water injection pipe 75A into the water-injection well 2. In this embodiment, when the operating frequency of the pump 72 has dropped to its lowest frequency and the flow rate of groundwater into the water-injection well 2 is smaller than a predetermined reference flow rate, the valve aperture control unit 82 may adjust the aperture of only the small-diameter water injection pipe 75A. In this embodiment, when the operating frequency of the pump 72 is reduced to the lowest frequency and the flow rate of groundwater into the water-injection well 2 is greater than a predetermined flow rate reference value, the valve aperture control unit 82 may open both the small-diameter flow control valve 77A provided on the small-diameter water injection pipe 75A and the large-diameter flow control valve 77B provided on the large-diameter water injection pipe 75B, and inject water into the water-injection well 2 through both the small-diameter water injection pipe 75A and the large-diameter water injection pipe 75B. In this embodiment, when the operating frequency of the pump 72 is reduced to the lowest frequency and the flow rate of groundwater into the water-injection well 2 is greater than a predetermined flow rate reference value, the valve aperture control unit 82 may adjust the aperture only using the large-diameter flow control valve 77B provided on the large-diameter water injection pipe 75B.

[0041] 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 a control method. The control device 80 performs each step shown in FIG.

[0042] First, when the load equipment 100 is operating in cooling mode or heating mode, the pump operation control unit 81 operates the pump 72 to pump groundwater from the pumping pipe 71 of one of the pair of wells 2, the pumping well 21 (ST01: step of operating the pump). As a result, the groundwater pumped from the pumping well 21 passes through the piping 3 and is sent to the heat exchanger 4. In the heat exchanger 4, the groundwater in the piping 3 exchanges heat with the medium on the load equipment 100 side. The groundwater that has passed through the heat exchanger 4 is injected into the other water injection well 22 through the water injection pipe 75. At this time, on the water injection well 22 side, the geothermal utilization system 1 injects water through all of the multiple water injection pipes 75 (the small-diameter water injection pipe 75A and the large-diameter water injection pipe 75B). During startup of the pump 72, the valve opening control unit 82 may initially open only the small-diameter flow control valve 77A, thereby injecting water into the water injection well 22 only through the small-diameter water injection pipe 75A. Thereafter, as the operating frequency of the pump 72 increases, the valve opening control unit 82 may gradually open the small-diameter flow control valve 77A, thereby increasing the water injection flow rate through the small-diameter water injection pipe 75A. Furthermore, once the operating frequency of the pump 72 has increased to a certain extent, the valve opening control unit 82 may further open the large-diameter flow control valve 77B, thereby injecting water into the water injection well 22 through both the small-diameter water injection pipe 75A and the large-diameter water injection pipe 75B. Thereafter, as the operating frequency of the pump 72 increases, the valve opening control unit 82 may further open the large-diameter flow control valve 77B, thereby increasing the water injection flow rate through the large-diameter water injection pipe 75B.

[0043] When the load equipment 100 is operating in cooling mode or heating mode, the pump operation control unit 81 adjusts the operating frequency of the inverter control of the pump 72 that sends groundwater from the pumping well 21 to the injection well 22, depending on the set temperature of the groundwater injected into the injection well 22 via the heat exchanger 4 (ST02: step of adjusting the operating frequency of the pump). This adjusts the flow rate of water injected from the pumping well 21 to the injection well 22 by the pump 72.

[0044] Following execution of ST02, the pump operation control unit 81 determines whether the operating frequency of the inverter control of the pump 72 has dropped to the minimum frequency (ST03: step of determining whether the operating frequency of the pump has dropped to the minimum frequency).

[0045] If the determination in ST03 shows that the operating frequency of the inverter control of the pump 72 has not dropped to the minimum frequency, the process returns to ST02, where the pump operation control unit 81 continues to adjust the flow rate of water injected by the pump 72 from the pumping well 21 to the water injection well 22. If the determination in ST03 shows that the operating frequency of the inverter control of the pump 72 has dropped to the minimum frequency, the valve opening control unit 82 adjusts the opening of the large-diameter flow control valve 77B in a direction toward closure, depending on the set temperature of the groundwater to be injected into the water injection well 22 (ST04: step of adjusting the opening of the large-diameter flow control valve). The valve opening control unit 82 adjusts the flow rate of water injected into the water injection well 22 by adjusting the opening of the large-diameter flow control valve 77B. At this time, the pump operation control unit 81 maintains the operating frequency of the inverter control of the pump 72 at the minimum frequency. In other words, by closing the large-diameter flow control valve 77B when the operating frequency of the inverter control of the pump 72 is at the lowest frequency, the control device 80 further reduces the flow rate of groundwater injected into the injection well 22.

[0046] Following execution of ST04, the valve aperture control unit 82 determines whether the large-diameter flow control valve 77B is fully closed (ST05: step of determining whether the large-diameter flow control valve is fully closed). If the determination in ST05 shows that the large-diameter flow control valve 77B is not fully closed, the process returns to ST04, and the valve aperture control unit 82 continues processing. If the determination in ST05 shows that the large-diameter flow control valve 77B is fully closed, the flow rate of the groundwater injected into the well 2 is lower than the set reference flow rate value. Therefore, water is injected into the water injection well 22 only through the small-diameter water injection pipe 75A. In this case, the valve aperture control unit 82 adjusts the aperture of the small-diameter flow control valve 77A in the closing direction in accordance with the set temperature of the groundwater injected into the water injection well 22 (ST06: step of adjusting the aperture of the small-diameter flow control valve). The valve opening control unit 82 adjusts the opening of the small-diameter flow control valve 77A to adjust the flow rate of water injected into the water injection well 22. At this time, the pump operation control unit 81 also maintains the operating frequency of the inverter control of the pump 72 at the minimum frequency. In other words, with the operating frequency of the inverter control of the pump 72 at the minimum frequency, the valve opening control unit 82 closes the small-diameter flow control valve 77A while injecting water into the water injection well 22 only through the small-diameter water injection pipe 75A. This allows the control device 80 to further reduce the flow rate of groundwater injected into the water injection well 22.

[0047] When the operation of the geothermal energy utilization system 1 is stopped, the valve opening control unit 82 fully closes the small-diameter flow control valve 77A and the large-diameter flow control valve 77B, and then the pump operation control unit 81 stops the operation of the pump 72. This allows the geothermal energy utilization system 1 to stop operation while maintaining the groundwater in the pipe 3 in a pressurized state. By maintaining the groundwater in the pipe 3 in a pressurized state (positive pressure), it is possible to prevent foreign matter and oxygen from entering the pipe 3 from the outside, and to prevent corrosion of the pipe 3, etc.

[0048] (Actions and Effects) According to this embodiment, the geothermal energy utilization system 1 can send groundwater pumped up from the well 2 by the pump 72 to the heat exchanger 4 through the lift pipe 71 and the piping 3. Meanwhile, when the geothermal energy utilization system 1 injects the groundwater that has passed through the heat exchanger 4 into the well 2 through the piping 3 and the water injection pipe 75, it can adjust the flow rate of the groundwater injected into the well 2 by adjusting the aperture of the flow rate adjustment valve 77 provided on the water injection pipe 75. In this case, a plurality of water injection pipes 75 are provided. Each of the plurality of water injection pipes 75 is provided with a flow rate adjustment valve 77. Therefore, by adjusting the aperture of the flow rate adjustment valve 77 in each of the plurality of water injection pipes 75, the geothermal energy utilization system 1 can more precisely adjust the flow rate of the groundwater injected into the well 2. For example, the geothermal energy utilization system 1 can adjust the flow rate of groundwater injected into the well 2 by opening the flow rate adjustment valves 77 of some of the multiple water injection pipes 75 and closing the flow rate adjustment valves 77 of the other water injection pipes 75. Therefore, the geothermal energy utilization system 1 can easily adjust the flow rate. Furthermore, since the pump 72 is provided on the riser pipe 71 and the flow rate adjustment valve 77 is provided on the water injection pipe 75, if a problem occurs that interferes with the pumping or injection of water, the user can easily identify the cause of the problem, whether it is on the riser pipe 71 side or the water injection pipe 75 side. Furthermore, since the user can replace the pump 72 or the flow rate adjustment valve 77 individually, maintenance can be performed easily and at low cost.

[0049] According to one example of this embodiment, the piping 3 is provided with a pumping pipe 71 and a plurality of water injection pipes 75 at the end of the piping 3 that extends to each of the pair of wells 2. As a result, the ends 3a, 3b that extend to each of the wells 2 are each provided with a plurality of water injection pipes 75, so that the geothermal energy utilization system 1 can easily adjust the flow rate of groundwater injected into each well 2.

[0050] Furthermore, according to one example of this embodiment, when the operation of the geothermal energy utilization system 1 is stopped, the geothermal energy utilization system 1 can stop the operation of the pump 72 after fully closing the flow control valve 77, thereby stopping the operation while maintaining the groundwater in the pipe 3 in a pressurized state. In this way, by maintaining the groundwater in the pipe 3 in a pressurized state (positive pressure), the geothermal energy utilization system 1 can prevent foreign matter and oxygen from entering the pipe 3 from the outside, and can prevent corrosion of the pipe 3, etc.

[0051] According to one example of this embodiment, the geothermal energy utilization system 1 further includes a valve opening control unit 82 that adjusts the opening of the flow rate control valve 77 in accordance with the flow rate of water injected into the well 2. As a result, the geothermal energy utilization system 1 can easily adjust the temperature of the injected water by using the valve opening control unit 82 to adjust the opening of the flow rate control valve 77 in accordance with the flow rate of water injected into the well 2.

[0052] Furthermore, according to one example of this embodiment, when the flow rate of groundwater injected into the well 2 is smaller than the set reference flow rate value, the valve opening control unit 82 opens only the flow rate adjustment valves 77 provided on some of the multiple water injection pipes 75. In this way, by providing multiple water injection pipes 75, it is possible to reduce the pipe diameter of each water injection pipe 75 and the diameter of the flow rate adjustment valves 77 provided on each water injection pipe 75. Therefore, when the flow rate of groundwater injected into the well 2 is small, the geothermal utilization system 1 can more precisely adjust the flow rate of groundwater in the small flow rate range by opening only the flow rate adjustment valves 77 of some of the multiple water injection pipes 75.

[0053] According to one example of this embodiment, the pipe diameters of the multiple water injection pipes 75 are different from one another. As a result, for example, when the flow rate of groundwater injected into the well 2 is small, the geothermal energy utilization system 1 can adjust the flow rate of the groundwater injected into the well 2 using only the small-diameter flow control valve 77A of the small-diameter water injection pipe 75A. This allows the geothermal energy utilization system 1 to more precisely adjust the flow rate of groundwater in the small-flow rate range.

[0054] According to one example of the present embodiment, the control device 80 includes a pump operation control unit 81 and a valve aperture control unit 82. As a result, by operating the pump 72 using the pump operation control unit 81, the control device 80 can pump groundwater from a lift pipe 71 provided in one of the pair of wells 2. The groundwater pumped from the lift pipe 71 passes through the heat exchanger 4 and is injected into the other well 2 through multiple water injection pipes 75. By adjusting the apertures of the flow rate adjustment valves 77 provided in each of the multiple water injection pipes 75 using the valve aperture control unit 82, the control device 80 can easily adjust the flow rate of groundwater injected into the other well 2.

[0055] <Modifications> In the above-described embodiment, a program for realizing the various functions of the control device 80 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system such as a microcomputer and executed to perform various processes. Here, the various processes of the CPU of the computer system are stored in the form of a program on a computer-readable recording medium, and the computer reads and executes the program to perform the various processes. Examples of computer-readable recording media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program.

[0056] In the above-described embodiment, an example of the hardware configuration of the computer 190 that executes the programs for realizing the various functions of the control device 80 will be described.

[0057] As shown in FIG. 5 , the computer 190 provided in the control device 80 includes a processor 195, a memory 196, a storage / playback device 197, an input output interface (hereinafter referred to as “IO I / F”) 198, and a communication interface (hereinafter referred to as “communication I / F”) 199.

[0058] For example, the processor 195 may be a CPU. For example, the memory 196 may be a medium such as random access memory (hereinafter referred to as "RAM") that temporarily stores data and the like used by programs executed by the control device 80. For example, the storage / playback device 197 may be a device for storing data and the like in external media such as CD-ROMs, DVDs, and flash memories, or for playing back data and the like from external media. For example, the IO I / F 198 may be an interface for inputting and outputting information and the like between the control device 80 and other devices. For example, the communication I / F 199 may be an interface for communicating between the control device 80 and other devices via a communication line such as the Internet or a dedicated communication line.

[0059] <Other Embodiments> Although the embodiments of the present disclosure have been described above, these embodiments are provided by way of example only and are not intended to limit the scope of the present disclosure. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the present disclosure. These embodiments and their modifications are considered to be within the scope and spirit of the present disclosure, as well as within the scope of the present disclosure and its equivalents.

[0060] <Additional Notes> The geothermal energy utilization system 1, the control device 80, the control method, and the program described in the embodiment can be understood, for example, as follows.

[0061] (1) The geothermal energy utilization system 1 relating to the first aspect comprises a well 2, a pipe 3 having an end extending to the well 2, and a heat exchanger 4 provided on the pipe 3, and the pipe 3 has at its end a pumping pipe 71 connected to a pump 72 capable of pumping groundwater in the well 2, and a plurality of water injection pipes 75 each equipped with a flow control valve 77.

[0062] This geothermal energy utilization system 1 can send groundwater pumped up from a well 2 by a pump 72 to a heat exchanger 4 through a lift pipe 71 and piping 3. On the other hand, when the geothermal energy utilization system 1 injects the groundwater that has passed through the heat exchanger 4 into the well 2 through piping 3 and a water injection pipe 75, it can adjust the flow rate of the groundwater injected into the well 2 by adjusting the aperture of a flow rate adjustment valve 77 provided on the water injection pipe 75. In this case, a plurality of water injection pipes 75 are provided. Each of the plurality of water injection pipes 75 is provided with a flow rate adjustment valve 77. Therefore, by adjusting the aperture of the flow rate adjustment valve 77 in each of the plurality of water injection pipes 75, the geothermal energy utilization system 1 can more precisely adjust the flow rate of the groundwater injected into the well 2. For example, the geothermal energy utilization system 1 can adjust the flow rate of groundwater injected into the well 2 by opening the flow rate adjustment valves 77 of some of the multiple water injection pipes 75 and closing the flow rate adjustment valves 77 of the other water injection pipes 75. Therefore, the geothermal energy utilization system 1 can easily adjust the flow rate.

[0063] (2) The geothermal energy utilization system 1 according to the second aspect is the geothermal energy utilization system 1 of (1), which may include a pair of wells 2, and the piping 3 may include the pumping pipe 71 and a plurality of water injection pipes 75 at the ends 3a, 3b extending to each of the wells 2.

[0064] As a result, multiple water injection pipes 75 are provided at each end 3a, 3b of the piping 3 extending to each well 2, making it easier for the geothermal energy utilization system 1 to adjust the flow rate of groundwater injected into each well 2.

[0065] (3) The geothermal energy utilization system 1 according to the third aspect is the geothermal energy utilization system 1 of (1) or (2), and the flow control valve 77 may be capable of maintaining the pressure in the piping 3 in a pressurized state.

[0066] As a result, when the operation of the geothermal energy utilization system 1 is stopped, the geothermal energy utilization system 1 can stop operation while maintaining a pressurized state of the groundwater in the pipe 3 by fully closing the flow control valve 77 and then stopping the operation of the pump 72. In this way, by keeping the groundwater in the pipe 3 under pressurized state (positive pressure), the geothermal energy utilization system 1 can prevent foreign matter and oxygen from entering the pipe 3 from the outside and prevent corrosion of the pipe 3, etc.

[0067] (4) The geothermal energy utilization system 1 relating to the fourth aspect may be any one of the geothermal energy utilization systems 1 (1) to (3) and may further include a valve opening control unit 82 that adjusts the opening of the flow control valve 77 according to the water injection flow rate into the well 2.

[0068] As a result, the geothermal energy utilization system 1 can easily adjust the temperature of the water to be injected by adjusting the opening of the flow control valve 77 using the valve opening control unit 82 in accordance with the flow rate of water to be injected into the well 2.

[0069] (5) The geothermal energy utilization system 1 relating to the fifth aspect is any one of the geothermal energy utilization systems 1 (1) to (4), and the valve opening control unit 82 may open only the flow control valves 77 provided on some of the multiple water injection pipes 75 when the flow rate of the groundwater injected into the well 2 is smaller than the flow rate setting reference value.

[0070] Thus, by providing a plurality of water injection pipes 75, it is possible to reduce the pipe diameter of each water injection pipe 75 and the diameter of the flow rate adjustment valve 77 provided on each water injection pipe 75. Therefore, when the flow rate of groundwater injected into the well 2 is small, the geothermal energy utilization system 1 can more precisely adjust the flow rate of groundwater in the low flow rate range by opening the flow rate adjustment valves 77 of only some of the plurality of water injection pipes 75.

[0071] (6) The geothermal energy utilization system 1 according to the sixth aspect is any one of the geothermal energy utilization systems 1 of (1) to (5), and the multiple water injection pipes 75 may have different pipe diameters.

[0072] As a result, for example, when the flow rate of groundwater injected into the well 2 is small, the geothermal energy utilization system 1 can adjust the flow rate of the groundwater injected into the well 2 using only the flow rate adjustment valve 77 of the small-diameter water injection pipe 75. This allows the geothermal energy utilization system 1 to more precisely adjust the flow rate of groundwater in the small flow rate region.

[0073] (7) The control device 80 according to the seventh aspect includes a pump operation control unit 81 that operates a pump 72 provided on a water pumping pipe 71 provided on one of a pair of wells 2 to pump groundwater from the water pumping pipe 71, and a valve opening control unit 82 that adjusts the opening of flow control valves 77 provided on each of a plurality of water injection pipes 75 provided on the other well 2 so that the groundwater pumped from the water pumping pipe 71 passes through a heat exchanger 4 and is injected into the other well 2 at a predetermined flow rate through a plurality of water injection pipes 75 provided on the other well 2.

[0074] As a result, by operating the pump 72 with the pump operation control unit 81, the control device 80 can pump up groundwater from the lifting pipe 71 installed in one of the pair of wells 2. The groundwater pumped up from the lifting pipe 71 passes through the heat exchanger 4 and is injected into the other well 2 through multiple water injection pipes 75. By adjusting the aperture of the flow rate adjustment valves 77 installed in each of the multiple water injection pipes 75 with the valve aperture control unit 82, the control device 80 can easily adjust the flow rate of groundwater injected into the other well 2.

[0075] (8) The control method according to the eighth aspect operates a pump 72 provided on a water pumping pipe 71 provided on one of a pair of wells 2 to pump groundwater from the water pumping pipe 71, and adjusts the opening of flow control valves 77 provided on each of a plurality of water injection pipes 75 provided on the other well 2 so that the groundwater pumped from the water pumping pipe 71 passes through a heat exchanger 4 and is injected into the other well 2 at a predetermined flow rate through a plurality of water injection pipes 75 provided on the other well 2.

[0076] As a result, the control method can operate the pump 72 to pump up groundwater from the lift pipe 71 installed in one of the pair of wells 2. The groundwater pumped up from the lift pipe 71 passes through the heat exchanger 4 and is injected into the other well 2 from multiple water injection pipes 75. By adjusting the opening of the flow rate adjustment valves 77 installed in each of the multiple water injection pipes 75, the control method can easily adjust the flow rate of groundwater injected into the other well 2.

[0077] (9) The program relating to the ninth aspect causes the computer 190 to execute a method of operating a pump 72 provided on a water pumping pipe 71 provided on one of a pair of wells 2 to pump groundwater from the water pumping pipe 71, and adjusting the opening degree of a flow control valve 77 provided on each of a plurality of water injection pipes 75 provided on the other well 2 so that the groundwater pumped from the water pumping pipe 71 passes through a heat exchanger 4 and is injected into the other well 2 at a predetermined flow rate through a plurality of water injection pipes 75 provided on the other well 2.

[0078] As a result, the computer 190 can operate the pump 72 to pump up groundwater from the lift pipe 71 installed in one of the pair of wells 2. The groundwater pumped up from the lift pipe 71 passes through the heat exchanger 4 and is injected into the other well 2 through multiple water injection pipes 75. By adjusting the opening of the flow rate adjustment valves 77 installed in each of the multiple water injection pipes 75, it becomes easier to adjust the flow rate of groundwater injected into the other well 2.

[0079] DESCRIPTION OF SYMBOLS 1...Geothermal heat utilization system 2...Well 2A...First well 2B...Second well 2a...Casing 2b...Strainer 2c...Opening 3...Pipe 3a...End 3b...End 4...Heat exchanger 7...Flow rate adjustment system 21...Pumping well 22...Water injection well 35a-35d...Check valve 71...Pumping pipe 72...Pump 73...Check valve 74...Pump controller 75...Water injection pipe 75A...Small diameter water injection pipe 75B...Large diameter water injection pipe 77...Flow rate adjustment valve 77A...Small diameter flow rate adjustment valve 77B...Large diameter flow rate adjustment valve 80...Control device 81...Pump operation control unit 82...Valve opening control unit 100...Load equipment 190...Computer 195...Processor 196...Memory 197...Storage / playback device 198...IO I / F 199...Communication I / F HOL...Borehole LY...Aquifer OG...Ground ST01...Step of operating the pump ST02...Step of adjusting the operating frequency of the pump ST03...Step of determining whether the operating frequency of the pump has dropped to the minimum frequency ST04...Step of adjusting the opening of the large diameter flow control valve ST05...Step of determining whether the opening of the large diameter flow control valve is fully closed ST06...Step of adjusting the opening of the small diameter flow control valve

Claims

1. A geothermal energy utilization system comprising: a well; a pipe having an end extending into said well; and a heat exchanger provided on said pipe, wherein said pipe has at its end a water pumping pipe connected to a pump capable of pumping groundwater from said well; and a plurality of water injection pipes each equipped with a flow control valve.

2. A geothermal energy utilization system as described in claim 1, comprising a pair of wells, and wherein the piping comprises, at the end extending to each of the wells, a water pumping pipe and a plurality of water injection pipes.

3. A geothermal energy utilization system as described in claim 1 or 2, wherein the flow control valve is capable of maintaining the pressure in the piping at a pressurized state.

4. A geothermal energy utilization system as described in any one of claims 1 to 3, further comprising a valve opening control unit that adjusts the opening of the flow control valve according to the water injection flow rate into the well.

5. A geothermal energy utilization system as described in claim 4, wherein the valve opening control unit opens only the flow control valves provided on some of the multiple injection pipes when the flow rate of the groundwater injected into the well is smaller than the flow rate setting reference value.

6. A geothermal energy utilization system as described in any one of claims 1 to 5, wherein the plurality of water injection pipes have different pipe diameters.

7. A control device comprising: a pump operation control unit that operates a pump installed on a lifting pipe installed in one of a pair of wells so as to pump up groundwater from the lifting pipe installed in the one of the wells; and a valve opening control unit that adjusts the opening of flow control valves installed on each of multiple water injection pipes installed in the other well so that the groundwater pumped from the lifting pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through multiple water injection pipes installed in the other well.

8. A control method comprising operating a pump attached to a riser pipe attached to one of a pair of wells to draw up groundwater from the riser pipe, and adjusting the opening of flow control valves attached to each of a plurality of water injection pipes attached to the other well so that the groundwater drawn from the riser pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through a plurality of water injection pipes attached to the other well.

9. A program for causing a computer to execute a method of operating a pump attached to a riser pipe attached to one of a pair of wells to draw up groundwater from the riser pipe, and adjusting the opening of flow control valves attached to each of a plurality of water injection pipes attached to the other well so that the groundwater drawn from the riser pipe passes through a heat exchanger and is injected into the other well at a predetermined flow rate through a plurality of water injection pipes attached to the other well.