Geothermal utilization system, control device, control method, and recording medium

Abstract

The geothermal utilization system in the present disclosure is provided with a pumping well, an injection well, a pipe extending from the pumping well to the injection well, a pump capable of transporting groundwater from the pumping well to the injection well via 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, and a control device that, in the case where the operating frequency of the inverter control of the pump has become the lowest frequency, adjusts the flow rate of the groundwater injected into the injection well by controlling the control valve in a manner of throttling the flow rate in the pipe.

Description

Technical Field

[0001] This disclosure relates to a geothermal utilization system, control device, control method, and procedure.

[0002] This application claims priority to Japanese Patent Application No. 2021-078700, filed on May 6, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, geothermal utilization systems that utilize groundwater as a heat source or a cold source have been proposed.

[0004] For example, Patent Document 1 proposes a geothermal utilization system comprising a pumping well and an injection well, wherein groundwater is drawn from the pumping well by a pump and exchanged with the load side in a heat exchanger. Such a geothermal utilization system stores heat by injecting groundwater that has passed through the heat exchanger into the injection well.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-173256 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In the geothermal utilization system disclosed in Patent Document 1, in order to keep the water injection temperature of the injection well constant, it is necessary to reduce the water injection flow rate under low load.

[0010] However, in the pump disclosed in Patent Document 1, when inverter control is performed, it is sometimes difficult to control the water injection temperature when the water injection flow rate becomes less than the water injection flow rate at the lowest frequency of inverter control under low load.

[0011] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a geothermal utilization system, control device, control method and program that allows for easy control of the injection water temperature under low load.

[0012] Technical solution

[0013] To address the aforementioned problems, the geothermal utilization system disclosed herein comprises: a pumping well; an injection well; piping extending from the pumping well to the injection well; a pump capable of conveying groundwater from the pumping well to the injection well via the piping; a heat exchanger disposed on the piping; a control valve disposed on the piping capable of adjusting the flow rate of the groundwater within the piping; and a control device that, when the operating frequency of the pump's inverter control has reached its lowest frequency, adjusts the flow rate of the groundwater injected into the injection well by controlling the control valve in a manner that throttles the flow rate within the piping.

[0014] The control device disclosed herein includes: a pump operation control unit that adjusts the operating frequency of an inverter-controlled pump that delivers groundwater from a pumping well to an injection well based on the temperature of the groundwater drawn from the pumping well and injected into the injection well via a heat exchanger; and a control valve opening / closing control unit that, when the operating frequency has reached its lowest frequency, adjusts the opening degree of a control valve provided on a pipe that supplies groundwater to the injection well based on the temperature of the groundwater injected into the injection well.

[0015] In the control method disclosed herein, the operating frequency of the inverter control of the pump that delivers the groundwater from the pumping well to the injection well is adjusted according to the temperature of the groundwater drawn from the pumping well and injected into the injection well via a heat exchanger. When the operating frequency has reached its lowest frequency, the opening degree of the control valve provided on the pipeline that delivers the groundwater to the injection well is adjusted according to the temperature of the groundwater injected into the injection well.

[0016] The program disclosed herein enables a computer to perform the following method: adjusting the operating frequency of an inverter control of a pump that delivers groundwater from a pumping well to an injection well based on the temperature of the groundwater drawn from the pumping well and injected into the injection well via a heat exchanger; and, when the operating frequency has reached its lowest frequency, adjusting the opening degree of a control valve located on a pipe supplying groundwater to the injection well based on the temperature of the groundwater injected into the injection well.

[0017] Invention Effects

[0018] According to the geothermal utilization system, control device, control method and procedure disclosed herein, the injection water temperature is easily controlled at low loads. Attached Figure Description

[0019] Figure 1 This is a diagram showing the schematic configuration of a geothermal utilization system according to an embodiment of the present disclosure.

[0020] Figure 2 This is a diagram showing the schematic configuration of the geothermal utilization system and the load equipment side according to an embodiment of the present disclosure.

[0021] Figure 3 This is a system diagram of a geothermal utilization system according to an embodiment of this disclosure.

[0022] Figure 4 This diagram illustrates the flow of groundwater and media in the geothermal utilization system according to an embodiment of this disclosure, when the system is operating in cooling mode on the load device side.

[0023] Figure 5 This diagram illustrates the flow of groundwater and media in the geothermal utilization system according to an embodiment of this disclosure, when the system is operating in heating mode on the load device side.

[0024] Figure 6 This is a block diagram of a control device according to an embodiment of the present disclosure.

[0025] Figure 7 This diagram illustrates the flow of groundwater and media in the geothermal utilization system according to an embodiment of this disclosure, when the system is operating in cooling tower mode on the load equipment side.

[0026] Figure 8 This diagram illustrates the flow of groundwater and media in the geothermal utilization system according to an embodiment of this disclosure, during chiller operation at the load equipment side.

[0027] Figure 9 This is a flowchart illustrating the sequence of control methods in embodiments of the present disclosure.

[0028] Figure 10 This diagram illustrates an example of the hardware configuration of a computer included in the control device of an embodiment of the present disclosure. Detailed Implementation

[0029] Hereinafter, embodiments of the present disclosure will be described using the accompanying drawings. In all the drawings, the same or equivalent components are labeled with the same reference numerals, and common descriptions are omitted.

[0030] [Implementation Method]

[0031] Reference Figures 1-9 The implementation methods of the geothermal utilization system disclosed herein will be described.

[0032] (Composition of a geothermal utilization system)

[0033] like Figures 1-3 As shown, the geothermal utilization system 1 mainly includes multiple wells 2, piping 3, heat exchangers 4, and a temperature regulation system 7 (see reference). Figure 3 ) and pump 31.

[0034] (The structure of a well)

[0035] like Figure 1As shown, multiple wells 2 extend from the surface OG into the aquifer LY.

[0036] For example, multiple wells 2 have a first well 2A and a second well 2B.

[0037] Geothermal utilization system 1 draws groundwater from one of the first well 2A and the second well 2B, exchanges heat in heat exchanger 4, and then injects the heat-exchanged groundwater into the other of the first well 2A and the second well 2B. That is to say, geothermal utilization system 1 has two operating modes: drawing groundwater from the first well 2A and injecting it into the second well 2B, and drawing groundwater from the second well 2B and injecting it into the first well 2A.

[0038] In the following description, the side of the first well 2A and the second well 2B that draws groundwater will be referred to as pumping well 21, and the side of the first well 2A and the second well 2B that injects groundwater will be referred to as injection well 22. That is to say, the first well 2A and the second well 2B may function as pumping well 21 and injection well 22, respectively.

[0039] However, for the sake of simplicity, the following explanation will focus on the case where the first well 2A is used as a pumping well 21 and the second well 2B is used as an injection well 22, and heat exchange takes place in the heat exchanger 4.

[0040] Each well 2 has a shell 2a buried in the excavation hole HOL dug from the ground surface OG toward the aquifer LY.

[0041] The shell 2a is a cylindrical shape that extends in the vertical direction.

[0042] Each well 2 has an opening 2c at the top.

[0043] For example, opening 2c can also be an opening at the top of housing 2a.

[0044] The housing 2a has, for example, a filter 2b consisting of multiple slits.

[0045] The well 2 is configured to draw groundwater from the aquifer LY into the interior of the shell 2a via filter 2b, or to return groundwater from the interior of the shell 2a to the aquifer LY.

[0046] For example, such as Figure 3 As shown, a manhole cover 6 can also be provided at the opening in the upper part of the housing 2a to close the opening.

[0047] (Composition of piping and pumps)

[0048] like Figure 1 , Figure 3 As shown, pipe 3 extends into the interior of well 2.

[0049] For example, the pipe 3 can also connect the pumping well 21 and the injection well 22 to various groundwater sources with both ends immersed in the pumping well 21 and the injection well 22.

[0050] For example, one end of the pipe 3 can be located in the pumping well 21, and the other end of the pipe 3 can be located in the injection well 22 so that the groundwater drawn by the pump 31 can flow from the pumping well 21 toward the injection well 22.

[0051] Pump 31 is installed in piping 3.

[0052] Pump 31 pumps water from well 2 to pipe 3.

[0053] For example, when well 2 functions as pumping well 21, pump 31 pumps water from well 2 to pipe 3.

[0054] For example, pump 31 can also draw groundwater from well 2 into pipe 3.

[0055] For example, pump 31 can also be installed at both ends of pipe 3 and immersed in groundwater in each well 2.

[0056] For example, the output of pump 31 can also be changed through inverter control.

[0057] A water injection valve 32 is installed in pipe 3.

[0058] Water injection valves 32 are respectively installed at both ends of pipe 3.

[0059] Water injection valve 32 can also be configured between pump 31 and heat exchanger 4 at both ends of piping 3.

[0060] For example, the water injection valve 32 can also be immersed in the groundwater in each well 2.

[0061] Water injection valve 32 injects groundwater into pipe 3.

[0062] For example, when well 2 functions as a water injection well 22, water injection valve 32 injects groundwater from pipe 3 into well 2 (water injection well 22).

[0063] When the pressure in pipe 3 becomes greater than the set pressure, the water injection valve 32 is opened, injecting the groundwater in pipe 3 into the water injection well 22.

[0064] like Figure 3 As shown, the piping 3 has check valves 35a to 35d between the heat exchanger 4 and the pumping well 21 and the injection well 22.

[0065] Check valves 35a to 35d control the flow of groundwater in piping 3 in such a way that the groundwater flows in the same direction relative to heat exchanger 4 whether groundwater is drawn from pumping well 21 or injection well 22.

[0066] For example, when groundwater is drawn from the first well 2A, the groundwater in pipe 3 flows from the first well 2A through check valve 35a, heat exchanger 4, and check valve 35b into the second well 2B. At this time, the pressure in pipe 3 on the upstream side (second well 2B side) of heat exchanger 4 is greater than the pressure in pipe 3 on the downstream side, so the water will not flow to check valve 35c and check valve 35d.

[0067] Similarly, when water is drawn from the second well 2B, the groundwater in the piping 3 flows from the second well 2B sequentially through check valve 35c, heat exchanger 4, and check valve 35d into the first well 2A. At this time, the pressure in the piping 3 upstream of the heat exchanger 4 (on the first well 2A side) is greater than the pressure in the piping 3 downstream, therefore the water will not flow to check valves 35a and 35b.

[0068] (Composition of a heat exchanger)

[0069] Heat exchanger 4 performs heat exchange between the groundwater in piping 3 and the medium on the side of the load equipment 100.

[0070] For example, heat exchanger 4 performs heat exchange between groundwater drawn from well 2 and flowing into piping 3 and the medium on the side of load equipment 100. After heat exchange, the groundwater flows from heat exchanger 4 into piping 3 and is injected into well 2.

[0071] For example, heat exchanger 4 can also be installed on the ground OG in the middle of piping 3.

[0072] When the water passing through heat exchanger 4 is warm water, geothermal utilization system 1 stores warm water heat by injecting warm water into well 2.

[0073] When the water passing through heat exchanger 4 is cold water, geothermal utilization system 1 performs cold water heat storage by injecting cold water into well 2.

[0074] Here, "warm water" refers to water with a temperature higher than the initial underground temperature of the groundwater in the aquifer, while "cold water" refers to water with a temperature lower than the initial underground temperature of the groundwater in the aquifer.

[0075] For example, the initial underground temperature of the groundwater in an aquifer is 18°C.

[0076] (Composition of load equipment)

[0077] like Figure 2 As shown, the load device 100 uses the medium that exchanges heat with the groundwater in the heat exchanger 4 and the piping 3.

[0078] The load device 100 is, for example, an air conditioning system equipped with a heat source 110 and an air conditioner 120.

[0079] For example, the heat source unit 110 can also be a heat pump equipped with a condenser, evaporator, compressor, etc.

[0080] Air conditioner 120 regulates the air in a space equipped with air conditioner 120 by exchanging heat with a medium supplied from heat source 110.

[0081] For example, the load device 100, as an air conditioning system, can switch between operating modes of cooling and heating.

[0082] The load device 100 has a piping system 101 between the heat exchanger 4, the heat source unit 110, and the air conditioner 120 for forming the flow of the medium corresponding to each operating mode. The piping system 101 is appropriately equipped with on / off valves (not shown) to circulate the medium between the heat exchanger 4, the heat source unit 110, and the air conditioner 120 according to each operating mode of the air conditioning system.

[0083] In this embodiment, the load device 100 may also include a cooling tower 130 and a second heat exchanger 140.

[0084] Cooling tower 130 cools the cooling water by exposing it to the atmosphere, thereby generating heat of vaporization. Cooling tower 130 circulates the cooling water between itself and the second heat exchanger 140.

[0085] The second heat exchanger 140 performs heat exchange between the medium in the piping system 101 on the air conditioning system side and the cooling water on the cooling tower 130 side.

[0086] The second heat exchanger 140 cools the medium of the piping system 101 on the air conditioning system side by exchanging heat with the cooling water that is cooled in the cooling tower 130.

[0087] The composition and purpose of the load device 100 are not limited to the above and may be modified as appropriate.

[0088] like Figure 4As shown, when cooling operation is performed on the load device 100 side to store warm water in the injection well 22, the second well 2B is used as the pumping well 21, and the first well 2A is used as the injection well 22. Groundwater is drawn from the second well 2B (which serves as the pumping well 21) by a pump 31 and sent to the heat exchanger 4. In the heat exchanger 4, heat exchange occurs between the groundwater in the piping 3 and the medium flowing in the piping system 101 on the load device 100 side. On the load device 100 side, the medium cooled by the heat exchange in the heat exchanger 4 is sent to the heat source unit 110, where heat exchange occurs again. Thus, the air conditioner 120 connected to the heat source unit 110 can cool the room. On the other hand, the medium heated by the heat exchange in the heat source unit 110 is sent back to the heat exchanger 4 for circulation. In the heat exchanger 4, the heated medium exchanges heat with the groundwater flowing in the piping 3, thereby heating the groundwater. The geothermal utilization system 1 injects heated groundwater into the injection well 22 through the piping 3, thereby storing warm water heat.

[0089] like Figure 5 As shown, when heating is performed on the load device 100 side to store cold water heat in the injection well 22, the first well 2A is used as the pumping well 21, and the second well 2B is used as the injection well 22. Groundwater is drawn from the first well 2A (the pumping well 21) and sent to the heat exchanger 4. In the heat exchanger 4, heat exchange occurs between the groundwater in the piping 3 and the medium flowing in the piping system 101 on the load device 100 side. On the load device 100 side, the medium heated by the heat exchange in the heat exchanger 4 is sent to the heat source unit 110, where heat exchange occurs again. Thus, the air conditioner 120 connected to the heat source unit 110 can provide indoor heating. On the other hand, the medium cooled by the heat exchange in the heat source unit 110 is sent back to the heat exchanger 4 for circulation. In the heat exchanger 4, the cooled medium exchanges heat with the groundwater flowing in the piping 3, thereby cooling the groundwater. The geothermal utilization system 1 injects cooled groundwater into the injection well 22 through the piping 3, thereby storing cold water heat.

[0090] (Composition of the temperature regulation system)

[0091] like Figure 3 As shown, the temperature adjustment system 7 includes a pump controller 71, a control valve 72, and a control device 80. The temperature adjustment system 7 adjusts the injection temperature of the injection well 22 by adjusting the flow rate of groundwater injected into the injection well 22.

[0092] Pump controller 71 controls the operation of pump 31.

[0093] For example, the pump controller 71 can also be configured to be associated with the pump 31 of each well 2.

[0094] For example, pump controller 71 has an inverter circuit (not shown) that implements inverter control of pump 31.

[0095] The pump controller 71 adjusts the speed of the pump 31 by changing the operating frequency of the inverter control implemented by the inverter circuit through the control device 80 described later.

[0096] The pump controller 71 changes the operating frequency of the inverter control implemented by the inverter circuit, thereby adjusting the speed of the pump 31, and thus adjusting the flow rate of groundwater injected from the heat exchanger 4 and the piping 3 into the injection well 22.

[0097] Hereinafter, the operating frequency of the inverter control of pump 31 will also be referred to as the "operating frequency of pump 31".

[0098] Control valve 72 is located on pipe 3.

[0099] For example, control valve 72 can also be located between each well 2 and heat exchanger 4.

[0100] For example, in this embodiment, the control valve 72 may also be located on the side of the specific heat exchanger 4 near the water injection well 22.

[0101] Control valve 72 can adjust the flow rate of groundwater in piping 3.

[0102] Control valve 72 adjusts the flow rate of groundwater in pipe 3 by opening / closing the flow path in pipe 3.

[0103] The control valve 72 adjusts the flow rate of groundwater in the piping 3 by adjusting its opening degree.

[0104] The control valve 72 adjusts the flow rate of groundwater in the piping 3 under the control of the control device 80.

[0105] When the operating frequency of pump 31 is reduced to the lowest frequency, control valve 72 adjusts the opening degree.

[0106] For example, the minimum frequency can also be determined by the type of pump and varies depending on the pump manufacturer.

[0107] (Composition of the control device)

[0108] The control device 80 adjusts the flow rate of groundwater injected into the injection well 22.

[0109] The control device 80 adjusts the operating frequency of the pump 31 and the opening degree of the control valve 72 in a manner that keeps the injection temperature of the groundwater injected into the injection well 22 constant.

[0110] The control device 80 adjusts the flow rate of groundwater injected into the injection well 22 by adjusting only the operating frequency of the pump 31 in the region where the operating frequency of the pump 31 is above the minimum frequency.

[0111] For example, the control device 80 can also be controllably connected to each pump controller 71.

[0112] For example, the control device 80 can also be controllably connected to each control valve 72.

[0113] For example, when the operating frequency of pump 31 is reduced to the lowest frequency, control device 80 adjusts the flow rate of groundwater injected into injection well 22 by adjusting the opening of control valve 72.

[0114] When the operating frequency of pump 31 is reduced to the lowest frequency, control device 80 reduces the flow rate of groundwater injected into injection well 22 by reducing the opening of control valve 72.

[0115] For example, the control device 80 can also be configured to maintain the operating frequency of the pump 31 at the lowest frequency when the operating frequency of the pump 31 is reduced to the lowest frequency and the flow rate of groundwater injected into the injection well 22 is adjusted by adjusting the opening of the control valve 72.

[0116] Furthermore, when the opening of the control valve 72 is reduced to the preset minimum opening, the control device 80 adjusts the flow rate of groundwater injected from the piping 3 into the injection well 22 by exchanging heat in the heat exchanger 4 with the medium on the side of the load equipment 100 cooled in the cooling tower 130.

[0117] like Figure 6 As shown, the control device 80 includes a pump operation control unit 81, a control valve opening and closing control unit 82, and a load-side flow path control unit 83.

[0118] The pump operation control unit 81 adjusts the speed of the pump 31 by changing the operating frequency of the inverter control implemented by the inverter circuit of the pump controller 71.

[0119] The pump operation control unit 81 adjusts the operating frequency of the pump 31 that draws groundwater from the pumping well 21 according to the temperature of the groundwater injected into the injection well 22.

[0120] The pump operation control unit 81 adjusts the operating frequency of the pump 31 based on a pre-stored mapping diagram, thereby adjusting the flow rate of groundwater injected from the piping 3 into the injection well 22.

[0121] For example, when the pump operation control unit 81 is operating in cooling mode on the load device 100 side and storing warm water in the injection well 22, it controls the operating frequency of the pump 31 based on the difference between the actual injection temperature of the groundwater injected from the piping 3 into the injection well 22 and the set temperature.

[0122] For example, when the pump operation control unit 81 is operating for heating on the load device 100 side and storing cold water in the injection well 22, it controls the operating frequency of the pump 31 based on the difference between the actual injection temperature of the groundwater injected from the piping 3 into the injection well 22 and the set temperature.

[0123] The pump operation control unit 81 controls the pump controller 71 by adjusting the operating frequency (output) of the pump 31 based on a pre-stored mapping diagram and the required injection water temperature.

[0124] The pump operation control unit 81 stores, for example, the lower limit of the operating frequency at which the pump 31 can operate stably as a minimum frequency. The pump operation control unit 81 controls the pump controller 71 by adjusting the operation of the pump 31 in a frequency range above the preset minimum frequency.

[0125] The control valve opening and closing control unit 82 adjusts the flow rate of groundwater in the piping 3 by opening / closing the control valve 72.

[0126] The control valve opening and closing control unit 82 adjusts the flow rate of groundwater in the piping 3 by adjusting the opening degree of the control valve 72.

[0127] When the operating frequency of the pump 31 is reduced to the lowest frequency, the control valve opening and closing control unit 82 adjusts the opening degree of the control valve 72.

[0128] When the operating frequency of the pump 31 has reached its lowest frequency, the control valve opening and 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.

[0129] The load-side flow path control unit 83 controls the flow of the medium in the load device 100 by switching valves and the like in the piping system 101 located on the load device 100 side.

[0130] The load-side flow path control unit 83 controls the flow of the medium in the piping system 101 according to various operating modes such as cooling mode and heating mode.

[0131] If the opening degree of the control valve 72 becomes the preset minimum opening degree and the water injection temperature does not reach the set temperature, the load-side flow path control unit 83 switches the operation mode of the load device 100 to the cooling tower mode described later.

[0132] When the operating frequency of the pump 31 is reduced to the lowest frequency, and the opening degree of the control valve 72 has reached the preset minimum setting degree, the load-side flow path control unit 83 switches the operating mode of the load device 100 to the cooling tower mode.

[0133] In the cooling tower mode, groundwater that has exchanged heat with the cooling water of the cooling tower 130 in the heat exchanger 4 is injected into the injection well 22.

[0134] Furthermore, the load-side flow path control unit 83 can also switch the operating mode of the load device 100 to the refrigeration mode described later.

[0135] like Figure 7 As shown, a cooling tower can also be used to cool groundwater for cold water heat storage.

[0136] In the cooling tower mode, the load device 100 sends cooling water, cooled by the heat of vaporization during contact with the atmosphere in the cooling tower 130, to the second heat exchanger 140. In the second heat exchanger 140, heat exchange occurs between the cooling water and the medium in the piping system 101. That is, in the second heat exchanger 140, the medium in the piping system 101 is cooled by the cooling water cooled in the cooling tower 130. The cooled medium is then sent to the heat exchanger 4 to exchange heat with the groundwater in the piping 3. As a result, the groundwater in the piping 3 is cooled and injected into the injection well 22, thereby performing cold water heat storage.

[0137] In addition, such as Figure 8 As shown, a chiller mode can also be used to cool groundwater for cold water heat storage.

[0138] In chiller mode, the load device 100 uses a cooling tower 130 and a heat source unit 110 as a chiller. In this case, a pump 31, acting as a first well 2A (pumping well 21), draws groundwater and sends it to a heat exchanger 4. The heat exchanger 4 facilitates heat exchange between the groundwater in the piping 3 and the medium flowing in the piping system 101 on the load device 100 side, thereby cooling the groundwater. On the load device 100 side, the medium heated by heat exchange in the heat exchanger 4 is sent to the heat source unit 110. The heat source unit 110, connected to the cooling tower 130 via a second heat exchanger 140, cools the heated medium through heat exchange. The medium cooled by heat exchange in the heat source unit 110 is then sent back to the heat exchanger 4 for circulation. In the heat exchanger 4, the cooled medium exchanges heat with the groundwater flowing in the piping 3, thereby cooling the groundwater. The geothermal utilization system 1 injects the cooled groundwater into the injection well 22 through the piping 3, thereby storing cold water heat.

[0139] The operation of the control device 80 in this embodiment will be explained.

[0140] The operation of the control device 80 is equivalent to the implementation of the control method.

[0141] Control device 80 implementation Figure 9 The steps shown.

[0142] First, when the load device 100 is operating in either cooling or heating mode, the pump operation control unit 81 adjusts the inverter control operating frequency of the pump 31, which supplies groundwater from the pumping well 21 to the injection well 22, based on the set temperature of the groundwater injected into the injection well 22 via the heat exchanger 4 (ST01: Step to adjust the pump operating frequency). This adjusts the water flow rate from the pumping well 21 to the injection well 22 based on the pump 31.

[0143] After ST01 is implemented, the pump operation control unit 81 determines whether the operating frequency of the inverter control of the pump 31 has decreased to the minimum frequency (ST02: step of determining whether the pump operating frequency has decreased to the minimum frequency).

[0144] If the result of the determination in ST02 is that the operating frequency of the inverter control of pump 31 has not been reduced to the minimum frequency, then return to ST01, and the pump operation control unit 81 continues to adjust the water injection flow rate from pumping well 21 to injection well 22 based on pump 31.

[0145] If the determination in ST02 indicates that the operating frequency of the inverter control of pump 31 has been reduced to the minimum frequency, the control valve opening / closing control unit 82 adjusts the opening of control valve 72 towards the closing direction based on the set temperature of the groundwater injected into injection well 22 (ST03: Step for adjusting the opening of control valve). The control valve opening / closing control unit 82 adjusts the water injection flow rate into injection well 22 by adjusting the opening of control valve 72. At this time, the operating frequency of the inverter control of pump 31 remains at the minimum frequency. That is, when the operating frequency of the inverter control of pump 31 is at the minimum frequency, by closing control valve 72, control device 80 further reduces the flow rate of groundwater injected into injection well 22.

[0146] After ST03 is implemented, the control valve opening and closing control unit 82 determines whether the opening degree of the control valve 72 is the preset minimum opening degree (ST04: the step of determining whether the opening degree of the control valve is the minimum opening degree).

[0147] If the result of ST04 is that the opening degree of control valve 72 is not the minimum set opening degree, then return to ST03, and the control valve opening and closing control unit 82 continues to process.

[0148] If the result of ST04 indicates that the opening degree of control valve 72 is the minimum set opening degree, then the load-side flow path control unit 83 switches the operation mode of the load device 100 side to the cooling tower mode (ST05: the step of switching the operation mode of the load device side to the cooling tower mode). In the cooling tower mode, the geothermal utilization system 1 injects groundwater that has undergone heat exchange with the cooling water of the cooling tower 130 in the heat exchanger 4 into the injection well 22. As a result, the groundwater in the piping 3 is cooled and injected into the injection well 22, thereby implementing cold water heat storage.

[0149] For example, if the ambient temperature is too high to implement chilled water heat storage based on the cooling tower mode, the control device 80 can switch to the chiller mode to implement chilled water heat storage based on the chiller mode.

[0150] (Function and Effect)

[0151] According to this embodiment, the geothermal utilization system 1 draws groundwater from the pumping well 21 via the pump 31 and delivers it to the heat exchanger 4 through the piping 3. In the heat exchanger 4, heat exchange occurs between the groundwater and the medium on the load device 100 side, thereby utilizing geothermal energy. The groundwater passing through the heat exchanger 4 is then injected into the injection well 22 through the piping 3. The pump 31 adjusts the flow rate of the groundwater transported through the piping 3 via inverter control. When the operating frequency of the inverter control of the pump 31 reaches a preset minimum frequency, the geothermal utilization system 1 throttles the flow rate in the piping 3 via the control valve 72, thereby injecting groundwater into the injection well 22 at a flow rate lower than the minimum frequency of the pump 31. Therefore, the geothermal utilization system 1 can easily control the injection water temperature under low load conditions.

[0152] Furthermore, according to one example of this embodiment, the control valve 72 is located on the side of the specific heat exchanger 4 near the injection well 22.

[0153] Therefore, the geothermal utilization system 1 can control the water injection flow rate near the injection well 22. Consequently, the geothermal utilization system 1 can easily control the water injection temperature of the injection well 22.

[0154] Furthermore, according to one example of this embodiment, when the flow rate of groundwater in the piping 3 is adjusted by throttling the control valve 72, the control device 80 keeps the operating frequency of the inverter control of the pump 31 at the lowest frequency.

[0155] Thus, while the flow rate of groundwater is adjusted by throttling the control valve 72, the operating frequency of the inverter control of the pump 31 is kept at the lowest frequency, thereby enabling the geothermal utilization system 1 to efficiently adjust the flow rate achieved by the control valve 72.

[0156] Furthermore, according to an example of this embodiment, when the opening degree of the control valve 72 has reached the minimum set opening degree, the control device 80 causes the medium cooled by the cooling water of the cooling tower 130 to exchange heat with the groundwater in the piping 3 in the heat exchanger 4, and injects the cooled groundwater into the injection well 22.

[0157] When the opening degree of control valve 72 has reached the minimum set opening degree, the flow rate of groundwater injected into injection well 22 cannot be further reduced. In this case, by using cooling tower 130, geothermal utilization system 1 can further adjust the temperature of groundwater injected into injection well 22. As a result, geothermal utilization system 1 can control the injection water temperature under low load over a wider range.

[0158] Furthermore, according to one example of this embodiment, the control device 80 includes a pump operation control unit 81 and a control valve opening and closing control unit 82.

[0159] According to the control device 80, the pump operation control unit 81 adjusts the operating frequency of the inverter control of the pump 31 based on 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 control device 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 has reached the preset minimum frequency, the control valve opening and closing control unit 82 throttles the flow rate in the piping 3 by adjusting the opening degree of the control valve 72, thereby injecting groundwater into the injection well 22 at a flow rate lower than that at the minimum frequency of the pump 31. Therefore, the control device 80 can easily control the injection water temperature under low load.

[0160] [Variation Example]

[0161] It should be noted that in the above embodiments, programs for implementing various functions of the control device 80 are recorded on a computer-readable recording medium. The program recorded on this medium is then read into a computer system such as a microcomputer and executed, thereby performing various processes. Here, the various processing procedures of the computer system's CPU (Central Processing Unit) are stored in the form of a program on the computer-readable recording medium. The computer reads and executes this program, thereby performing the aforementioned various processes. Furthermore, a computer-readable recording medium refers to a magnetic disk, optical disk, CD-ROM (Compact Disc Read-Only Memory), DVD-ROM (Digital Video Disc Read Only Memory), semiconductor memory, etc. Alternatively, the computer program can be transmitted to a computer via a communication line, and the receiving computer executes the program.

[0162] In the above embodiments, an example of the hardware configuration of the computer 190 that executes programs for implementing various functions of the control device 80 will be described.

[0163] like Figure 10 As shown, the computer 190 of 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 a communication Interface (hereinafter referred to as "communication I / F") 199.

[0164] For example, processor 195 can also be a CPU.

[0165] For example, memory 196 may also be a medium such as Random Access Memory (hereinafter referred to as "RAM") that temporarily stores data used in a program executed by control device 80.

[0166] For example, the storage / reproduction device 197 may also be a device for storing data, etc., to external media such as CD-ROM, DVD, flash memory, etc., or for reproducing data, etc., from external media.

[0167] For example, IO I / F198 can also be an interface for inputting / outputting information between the control device 80 and other devices.

[0168] For example, the communication I / F199 can also be an interface for communication between the control device 80 and other devices via the Internet, dedicated communication lines, or other communication lines.

[0169] [Other Implementation Methods]

[0170] The embodiments of this disclosure have been described above, but these embodiments are shown as examples and are not intended to limit the scope of this disclosure. This embodiment can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of this disclosure. This embodiment and its variations are included within the scope and spirit of this disclosure, as well as within the scope of this disclosure and its equivalents.

[0171] [Postscript]

[0172] For example, the geothermal utilization system 1, control device 80, control method and program described in the implementation method are as follows.

[0173] (1) The geothermal utilization system 1 of the first scheme includes: a pumping well 21; an injection well 22; a piping 3 extending from the pumping well 21 to the injection well 22; a pump 31 capable of conveying groundwater from the pumping well 21 to the injection well 22 via the piping 3; a heat exchanger 4 disposed on the piping 3; a control valve 72 disposed on the piping 3 capable of adjusting the flow rate of the groundwater in the piping 3; and a control device 80, which, when the operating frequency of the inverter control of the pump 31 has reached the lowest frequency, adjusts the flow rate of the groundwater injected into the injection well 22 by controlling the control valve 72 in a manner that throttles the flow rate in the piping 3.

[0174] The geothermal utilization system 1 draws groundwater from the pump 31 through the pumping well 21 and delivers it to the heat exchanger 4 via piping 3. In the heat exchanger 4, heat exchange occurs between the groundwater and the medium on the load device 100 side, thereby utilizing geothermal energy. The groundwater passing through the heat exchanger 4 is then injected into the injection well 22 via piping 3. The pump 31 uses inverter control to adjust the flow rate of the groundwater transported via piping 3. When the inverter control operating frequency of the pump 31 reaches a preset minimum frequency, the geothermal utilization system 1 throttles the flow rate within piping 3 via control valve 72, thereby injecting groundwater into the injection well 22 at a flow rate lower than the minimum frequency of the pump 31. Therefore, the geothermal utilization system 1 can easily control the injection water temperature under low load conditions.

[0175] (2) Alternatively, the geothermal utilization system 1 of the second scheme is the geothermal utilization system 1 of (1), wherein the control valve 72 is located on the side of the water injection well 22 closer to the heat exchanger 4.

[0176] Therefore, the geothermal utilization system 1 can control the water injection flow rate near the injection well 22. Consequently, the geothermal utilization system 1 can easily control the water injection temperature of the injection well 22.

[0177] (3) Alternatively, the geothermal utilization system 1 of the third scheme is the geothermal utilization system 1 of (1) or (2), wherein the control device 80 adjusts the flow rate of the groundwater in the piping 3 by throttling the control valve 72, and keeps the operating frequency at the lowest frequency.

[0178] Thus, while the flow rate of groundwater is adjusted by throttling the control valve 72, the operating frequency of the inverter control of the pump 31 is kept at the lowest frequency, thereby enabling the geothermal utilization system 1 to efficiently adjust the flow rate achieved by the control valve 72.

[0179] (4) Alternatively, the geothermal utilization system 1 of the fourth scheme is any one of (1) to (3) geothermal utilization system 1, wherein the geothermal utilization system 1 has a cooling tower 130 on the load device 100 side, the load device 100 uses a medium that exchanges heat with the groundwater in the pipe 3 in the heat exchanger 4, and when the opening of the control valve 72 has become the minimum set opening, the control device 80 injects the groundwater that has exchanged heat with the medium cooled by the cooling tower 130 in the heat exchanger 4 into the injection well 22.

[0180] When the opening degree of control valve 72 has reached the minimum set opening degree, the flow rate of groundwater injected into injection well 22 cannot be further reduced. In this case, by using cooling tower 130, geothermal utilization system 1 can further adjust the temperature of groundwater injected into injection well 22. As a result, geothermal utilization system 1 can control the injection water temperature under low load over a wider range.

[0181] (5) Alternatively, the control device 80 of the fifth scheme may include: a pump operation control unit 81, which adjusts the operating frequency of the pump 31 that delivers the groundwater from the pumping well 21 to the injection well 22 based on the temperature of the groundwater drawn from the pumping well 21 and injected into the injection well 22 through the heat exchanger 4; and a control valve opening and closing control unit 82, which, when the operating frequency has become the lowest frequency, adjusts the opening degree of the control valve 72 provided on the pipe 3 that delivers the groundwater to the injection well 22 based on the temperature of the groundwater injected into the injection well 22.

[0182] According to the control device 80, the pump operation control unit 81 adjusts the operating frequency of the inverter control of the pump 31 based on 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 control device 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 has reached the preset minimum frequency, the control valve opening and closing control unit 82 throttles the flow rate in the piping 3 by adjusting the opening degree of the control valve 72, thereby injecting groundwater into the injection well 22 at a flow rate lower than that at the minimum frequency of the pump 31. Therefore, the control device 80 can easily control the injection water temperature under low load.

[0183] (6) Alternatively, in the control method of the sixth scheme, the operating frequency of the inverter control of the pump 31 that delivers the groundwater from the pumping well 21 to the injection well 22 is adjusted according to the temperature of the groundwater drawn from the pumping well 21 and injected into the injection well 22 through the heat exchanger 4. When the operating frequency has become the lowest frequency, the opening degree of the control valve 72 provided on the pipe 3 that delivers the groundwater to the injection well 22 is adjusted according to the temperature of the groundwater injected into the injection well 22.

[0184] This control method adjusts the operating frequency of the inverter control of pump 31 based on the temperature of the groundwater injected into injection well 22. Therefore, by adjusting the groundwater flow rate, the temperature of the groundwater injected into injection well 22 can be adjusted. When the operating frequency of the inverter control of pump 31 has reached a preset minimum frequency, the flow rate in piping 3 is throttled by adjusting the opening of control valve 72. This control method allows groundwater to be injected into injection well 22 at a flow rate lower than that at pump 31's minimum frequency. Therefore, the control method easily controls the injection water temperature under low load conditions.

[0185] (7) Alternatively, the seventh scheme's program causes the computer 190 to perform the following method: adjust the operating frequency of the inverter control of the pump 31 that delivers the groundwater from the pumping well 21 to the injection well 22 according to the temperature of the groundwater drawn from the pumping well 21 and injected into the injection well 22 through the heat exchanger 4; and when the operating frequency has become the lowest frequency, adjust the opening degree of the control valve 72 provided on the pipe 3 that delivers the groundwater to the injection well 22 according to the temperature of the groundwater injected into the injection well 22.

[0186] According to the program, computer 190 adjusts the operating frequency of the inverter control of pump 31 based on the temperature of the groundwater injected into injection well 22. Thus, by adjusting the groundwater flow rate, the temperature of the groundwater injected into injection well 22 can be adjusted. When the operating frequency of the inverter control of pump 31 has reached a preset minimum frequency, the flow rate in piping 3 is throttled by adjusting the opening of control valve 72, allowing computer 190 to inject groundwater into injection well 22 at a flow rate lower than the minimum frequency of pump 31. Therefore, the program easily controls the injection temperature under low load conditions.

[0187] Industrial availability

[0188] According to this disclosure, a geothermal utilization system, control device, control method, and program that can easily control the injection water temperature under low load can be provided.

[0189] Explanation of reference numerals in the attached figures

[0190] 1: Geothermal Utilization System

[0191] 2: Well

[0192] 2A: Well No. 1

[0193] 2B: Second Well

[0194] 2a: Shell

[0195] 2b: Filter

[0196] 2c: Opening

[0197] 3: Piping

[0198] 4: Heat exchanger

[0199] 6: Manhole cover

[0200] 7: Temperature Control System

[0201] 21: Pumping well

[0202] 22: Water injection well

[0203] 31: Pump

[0204] 32: Water injection valve

[0205] 35a~35d: Check valve

[0206] 71: Pump Controller

[0207] 72: Control valve

[0208] 80: Control device

[0209] 81: Pump Action Control Unit

[0210] 82: Control valve opening and closing control unit

[0211] 83: Load-side flow path control unit

[0212] 100: Load device

[0213] 101: Piping System

[0214] 110: Heat source machine

[0215] 120: Air conditioner

[0216] 130: Cooling Tower

[0217] 140: Second heat exchanger

[0218] 190: Computer

[0219] 195: Processor

[0220] 196: Memory

[0221] 197: Storage / Reproduction Device

[0222] 198: IO I / F

[0223] 199: Communication I / F

[0224] HOL: Excavation Hole

[0225] LY: Aquifer

[0226] OG: Ground

[0227] ST01: Steps for adjusting the pump's operating frequency

[0228] ST02: Steps to determine if the pump's operating frequency has decreased to the minimum frequency

[0229] ST03: Steps for adjusting the opening of the control valve

[0230] ST04: Steps to determine whether the control valve opening is the minimum set opening.

[0231] ST05: Steps to switch the operating mode of the load device to cooling tower mode.

Claims

1. A geothermal utilization system, comprising: Pumping well; Water injection well; Piping extending from the pumping well to the injection well; The pump can transport groundwater from the pumping well to the injection well via the piping. A heat exchanger is provided on the piping; A control valve, located in the piping, is used to adjust the flow rate of the groundwater within the piping. The control device, when the operating frequency of the inverter control of the pump has reached its lowest frequency, adjusts the flow rate of the groundwater injected into the injection well by controlling the control valve in a manner that throttles the flow rate in the piping. as well as A cooling tower is installed on the side of the load equipment, which uses the groundwater in the heat exchanger to exchange heat with the groundwater in the piping. When the opening of the control valve has reached the minimum set opening, the control device injects the groundwater, which has exchanged heat with the medium cooled by the cooling tower in the heat exchanger, into the injection well.

2. The geothermal utilization system according to claim 1, wherein, The control device includes a pump operation control unit, which adjusts the operating frequency of the inverter control based on the temperature of the groundwater drawn from the pumping well and injected into the injection well through the heat exchanger.

3. The geothermal utilization system according to claim 2, wherein, The control device also includes a control valve opening and closing control unit, which adjusts the opening degree of the control valve according to the temperature when the operating frequency has become the lowest frequency.

4. The geothermal utilization system according to any one of claims 1 to 3, wherein, The control valve is located closer to the injection well than the heat exchanger.

5. The geothermal utilization system according to any one of claims 1 to 3, wherein, The control device maintains the operating frequency at the lowest possible frequency while adjusting the flow rate of the groundwater in the piping by throttling the control valve.

6. A control device comprising: The pump operation control unit, via piping extending from the pumping well to the injection well and equipped with a heat exchanger for heat exchange between groundwater and the medium used by the load equipment, adjusts the operating frequency of the inverter control of the pump that delivers groundwater from the pumping well to the injection well; and The control valve opening and closing control unit adjusts the opening degree of the control valve installed on the pipeline that supplies groundwater to the injection well when the operating frequency has reached its lowest frequency. When the opening degree has reached the minimum set opening degree, the groundwater that has exchanged heat with the medium cooled by the cooling tower on the load equipment side in the heat exchanger is injected into the injection well.

7. A control method, wherein, The operating frequency of the inverter control of the pump that delivers groundwater from the pumping well to the injection well is adjusted via piping that extends from the pumping well to the injection well and is equipped with a heat exchanger for heat exchange between groundwater and the medium used by the load equipment. When the operating frequency has reached its lowest possible value, adjust the opening of the control valve on the pipe that supplies groundwater to the injection well. When the opening degree has reached the minimum set opening degree, the groundwater that has exchanged heat with the medium cooled by the cooling tower on the load equipment side in the heat exchanger is injected into the injection well.

8. A recording medium having a program recorded thereon for causing a computer to perform the following methods: The operating frequency of the inverter control of the pump that delivers groundwater from the pumping well to the injection well is adjusted via piping that extends from the pumping well to the injection well and is equipped with a heat exchanger for heat exchange between groundwater and the medium used by the load equipment. When the operating frequency has reached its lowest possible value, adjust the opening of the control valve on the pipe that supplies groundwater to the injection well. When the opening degree has reached the minimum set opening degree, the groundwater that has exchanged heat with the medium cooled by the cooling tower on the load equipment side in the heat exchanger is injected into the injection well.

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