Control device, geothermal heat utilization system, control method, and program

Abstract

This control device is for a geothermal heat utilization system comprising: a heat source well facility provided with a pumping water well, a return water well, a well-side pipe extending from the pumping water well to the return water well, and a heat exchanger provided partway in the well-side pipe; a geothermal heat utilization circuit provided between the heat exchanger and equipment; and an auxiliary heat supply facility provided in the equipment in parallel with the geothermal heat utilization circuit and provided with a heat source machine. The control device includes a return water temperature acquisition unit that acquires a return water temperature of water returned to a return water well of the geothermal heat utilization system, a flow rate control unit that controls a flow rate of a refrigerant flowing from the geothermal heat utilization circuit to the equipment on the basis of the return water temperature, and a heat source machine control unit that controls start and stop of the heat source machine on the basis of the return water temperature.

Description

Control device, geothermal heat utilization system, control method, and program

[0001] This application claims priority to Japanese Patent Application No. 2023-162956 filed on September 26, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, geothermal energy utilization systems that utilize heat stored underground have been proposed.

[0003] As a related technology, for example, Patent Document 1 discloses a geothermal energy utilization system that stores cold or hot heat discharged from an air conditioning system underground.

[0004] Patent No. 7179905

[0005] The geothermal energy utilization system disclosed in Patent Document 1 adjusts the flow rate of water injected from the pumping well to the return well depending on the set temperature of the groundwater returned to the return well. However, for example, when the heat load required by equipment such as an air conditioning system is large, the geothermal energy utilization system disclosed in Patent Document 1 may not be able to adjust the return water temperature. As a result, the return water temperature may affect the underground environment.

[0006] The present disclosure provides a control device, a geothermal heat utilization system, a control method, and a program that have little impact on the underground environment.

[0007] The control device of the present disclosure comprises a heat source well equipment including a pumping well, a return well, a well-side pipe extending from the pumping well to the return well, and a heat exchanger provided midway along the well-side pipe, a geothermal heat utilization system including a geothermal heat utilization circuit provided between the heat exchanger and an equipment, and an auxiliary heat supply equipment provided in the equipment in parallel with the geothermal heat utilization circuit and including a heat source machine, the control device comprises: a return water temperature acquisition unit that acquires the return water temperature to the return well; a flow rate control unit that controls the flow rate of refrigerant flowing from the geothermal heat utilization circuit to the equipment based on the return water temperature; and a heat source machine control unit that controls the start and stop of the heat source machine based on the return water temperature.

[0008] The control device of the present disclosure comprises a geothermal energy utilization system including a heat source well facility having a pumping well, a return well, a well-side pipe extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side pipe; and a geothermal energy utilization circuit installed between the heat exchanger and equipment.The control device comprises: a return water temperature acquisition unit that acquires the return water temperature to the return well; a flow rate control unit that controls the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; and a pumping side water level acquisition unit that acquires the pumping side water level, which is the water level of the pumping well; and a pumping flow rate control unit that controls the pumping flow rate from the pumping well based on the pumping side water level.

[0009] The control device of the present disclosure comprises a geothermal heat utilization system including a heat source well facility having a pumping well, a return well, well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal heat utilization circuit installed between the heat exchanger and equipment; a return water temperature acquisition unit that acquires the return water temperature to the return well; a flow rate control unit that controls the flow rate of refrigerant flowing from the geothermal heat utilization circuit to the equipment based on the return water temperature; and further comprises a return water side water level acquisition unit that acquires the return water side water level, which is the water level of the return well, and a return water flow rate control unit that controls the return water flow rate to the return well based on the return water side water level.

[0010] The geothermal energy utilization system according to the present disclosure comprises the control device, the heat source well facility, and the geothermal energy utilization circuit.

[0011] The control method disclosed herein acquires the return water temperature to the return well of a geothermal energy utilization system comprising a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, a geothermal energy utilization circuit installed between the heat exchanger and an equipment, and an auxiliary heat supply equipment installed in the equipment in parallel with the geothermal energy utilization circuit and equipped with a heat source machine, controls the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature, and controls the start and stop of the heat source machine based on the return water temperature.

[0012] The control method disclosed herein is a geothermal energy utilization system including a heat source well facility having a pumping well, a return well, well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and equipment. The control method obtains the return water temperature to the return well, controls the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature, obtains the pumping-side water level, which is the water level of the pumping well, and controls the pumping flow rate from the pumping well based on the pumping-side water level.

[0013] The control method disclosed herein is a geothermal energy utilization system including a heat source well facility having a pumping well, a return well, well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and an equipment, and includes the steps of: obtaining the return water temperature to the return well; controlling the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; obtaining the return water side water level, which is the water level in the return well; and controlling the return water flow rate to the return well based on the return water side water level.

[0014] The program of the present disclosure causes a computer to acquire the return water temperature to the return well of a geothermal energy utilization system comprising a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, a geothermal energy utilization circuit installed between the heat exchanger and an equipment, and an auxiliary heat supply equipment installed in parallel with the geothermal energy utilization circuit and equipped with a heat source unit, control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature, and control the start and stop of the heat source unit based on the return water temperature.

[0015] The program of the present disclosure causes a computer to acquire the return water temperature to the return well of a geothermal energy utilization system comprising a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and an equipment; control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; acquire the pumping-side water level, which is the water level of the pumping well; and control the pumping flow rate from the pumping well based on the pumping-side water level.

[0016] The program of the present disclosure causes a computer to acquire the return water temperature to the return well of a geothermal energy utilization system comprising a pumping well, a return well, well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and an equipment, control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature, acquire the return water side water level, which is the water level of the return well, and control the return water flow rate to the return well based on the return water side water level.

[0017] The control device, geothermal heat utilization system, control method, and program disclosed herein have little impact on the underground environment.

[0018] FIG. 1 is a system diagram of a geothermal energy utilization system according to an embodiment of the present disclosure. FIG. 2 is a configuration diagram showing an example of an installation state of a water level meter at the natural water level of a geothermal energy utilization system according to an embodiment of the present disclosure. FIG. 3 is a configuration diagram showing an example of an installation state of a water level meter at the time of pumping and returning water of a geothermal energy utilization system according to an embodiment of the present disclosure. FIG. 4 is a detailed system diagram of a flow rate adjustment device according to an embodiment of the present disclosure. FIG. 5 is a block diagram of a control device according to an embodiment of the present disclosure. FIG. 6 is a flowchart of a method for controlling return water temperature according to an embodiment of the present disclosure. FIG. 7 is a flowchart of a method for controlling return water temperature according to an embodiment of the present disclosure. FIG. 8 is a flowchart of a method for controlling a pumping-side water level according to an embodiment of the present disclosure. FIG. 9 is a graph showing an example of a concept of sharing heat load between a heat source well facility and an auxiliary heat supply facility according to an embodiment of the present disclosure. FIG. 10 is an explanatory diagram of the effect of an example of hysteresis provided in the start-up temperature and stop-down temperature of a heat source machine according to an embodiment of the present disclosure. FIG. 11 is an explanatory diagram of the effect of an example of hysteresis provided in the start-up water level and stop-down water level of a heat source machine according to an embodiment of the present disclosure.

[0019] 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.

[0020] <Embodiments> An embodiment of a geothermal heat utilization system according to the present disclosure will be described with reference to Figures 1 to 12. (Configuration of the geothermal heat utilization system) As shown in Figure 1, the geothermal heat utilization system 1 includes a heat source well facility 10, a geothermal heat utilization circuit 20, an auxiliary heat supply facility 30, and a control device 50. The heat source well facility 10, the geothermal heat utilization circuit 20, and equipment AA are connected in series in this order to be able to absorb heat. The auxiliary heat supply facility 30 and equipment AA are connected in parallel to the heat source well facility 10 and the geothermal heat utilization circuit 20 to be able to absorb heat.

[0021] When cooling is being used by device AA (e.g., air conditioning load) (hereinafter referred to as "cooling operation"), the geothermal utilization system 1 uses the cold energy stored as chilled water in the heat source well facility 10 for cooling, and simultaneously stores the waste heat from device AA as hot water in the heat source well facility 10. When heating is being used by device AA (hereinafter referred to as "heating operation"), the geothermal utilization system 1 uses the hot energy stored as hot water in the heat source well facility 10 for heating, and simultaneously stores the waste cold energy from device AA as chilled water in the heat source well facility 10. For example, the geothermal utilization system 1 may be a system that switches between a pumping well and a return well according to the season, thereby using the hot waste heat from cooling in summer (hot water) for heating in winter, and using the waste heat from heating and cooling in winter (chilled water) for cooling in summer.

[0022] (Configuration of heat source well facility) The heat source well facility 10 includes a hot water well 11, a cold water well 12, well-side piping 13, and a heat exchanger 14. The heat source well facility 10 further includes a water thermometer 15 and a water level gauge 16 on each well side of the hot water well 11 and the cold water well 12.

[0023] In order to utilize the stored heat in equipment AA, heat source well facility 10 pumps groundwater from one of hot water well 11 and cold water well 12 to the surface, performs heat exchange on the surface for heat utilization, and injects the water into the other of hot water well 11 and cold water well 12. In other words, the heat storage utilization modes of heat source well facility 10 include a cold heat utilization mode in which groundwater is pumped from cold water well 12 and injected into hot water well 11 during cooling operation, and a hot heat utilization mode in which groundwater is pumped from hot water well 11 and injected into cold water well 12 during heating operation.

[0024] In the cold energy utilization mode, groundwater is pumped from the aquifer LY via the cold water well 12, so the cold water well 12 functions as a pumping well. On the other hand, in the cold energy utilization mode, the pumped groundwater is returned to the aquifer LY via the hot water well 11, so the hot water well 11 functions as a return well.

[0025] In the heat utilization mode, groundwater is pumped up from the aquifer LY via the hot water well 11, so the hot water well 11 functions as a pumping well. On the other hand, in the heat utilization mode, the pumped groundwater is returned to the aquifer LY via the cold water well 12, so the cold water well 12 functions as a return well.

[0026] (Configuration of Hot Water Well and Cold Water Well) The hot water well 11 and the cold water well 12 each extend from the ground into the aquifer LY. The hot water well 11 and the cold water well 12 each include a casing with a screen, and are configured to allow groundwater from the aquifer LY to be taken into the hot water well 11 and the cold water well 12, and groundwater to be returned from the hot water well 11 and the cold water well 12 to the aquifer LY. During steady-state operation of the geothermal energy utilization system 1, hot water is stored in the aquifer LY around the hot water well 11, and cold water is stored in the aquifer LY around the cold water well 12. The hot water well 11 and the cold water well 12 are located at a distance sufficient from each other to prevent the stored hot water and cold water from mixing.

[0027] (Configuration of well-side piping) The well-side piping 13 extends from the hot water well 11 to the cold water well 12. The well-side piping 13 connects the hot water well 11 and the cold water well 12. As shown in Figure 1 , a first end 131, which is one end of the well-side piping 13, extends into the hot water well 11 and is immersed in the groundwater inside the hot water well 11. A second end 132, which is the other end of the well-side piping 13, extends into the cold water well 12 and is immersed in the groundwater inside the cold water well 12.

[0028] Each of the first end 131 and the second end 132 is provided with a submersible pump PP, a water injection valve VA, a check valve VB, etc., and is configured to pump water from within each well into the well-side piping 13, and to inject water into each well from the well-side piping 13. The submersible pump PP can change its output by inverter control in response to commands from the control device 50.

[0029] (Configuration of Heat Exchanger) The heat exchanger 14 is provided midway along the well-side piping 13. The heat exchanger 14 exchanges heat between the water in the well-side piping 13 and the heat medium on the geothermal heat utilization circuit 20 side.

[0030] During cooling operation (cold energy utilization mode), the heat exchanger 14 exchanges heat between cold water, which is groundwater pumped up from the cold water well 12 and flowing in the well-side piping 13, and the heat medium on the geothermal energy utilization circuit 20 side. The cold energy obtained by the heat medium on the geothermal energy utilization circuit 20 side is utilized by equipment AA via the geothermal energy utilization circuit 20. On the other hand, the hot water, which is groundwater after heat exchange, flows from the heat exchanger 14 through the well-side piping 13 and is injected into the hot water well 11. This injection causes hot water heat storage in the hot water well 11.

[0031] During heating operation (in the case of the hot water utilization mode), the heat exchanger 14 exchanges heat between hot water, which is groundwater pumped up from the hot water well 11 and flowing in the well-side piping 13, and the heat medium on the geothermal heat utilization circuit 20 side. The hot heat obtained by the heat medium on the geothermal heat utilization circuit 20 side is used by equipment AA via the geothermal heat utilization circuit 20. On the other hand, the cold water, which is groundwater after the heat exchange, flows from the heat exchanger 14 through the well-side piping 13 and is injected into the cold water well 12. This injection causes cold water heat storage in the cold water well 12.

[0032] Here, "cold water" refers to water with a temperature lower than the initial underground temperature of the groundwater in the aquifer LY. On the other hand, "hot water" refers to water with a temperature higher than the initial underground temperature. For example, the initial underground temperature of the groundwater in the aquifer LY is 18°C.

[0033] (Configuration of the water thermometer) The water thermometer 15 on the cold water well 12 side is provided midway in the well-side piping 13 that runs from the cold water well 12 to the heat exchanger 14. For example, the water thermometer 15 on the cold water well 12 side may be provided at a position on the ground surface directly above the cold water well 12. The water thermometer 15 on the cold water well 12 side measures the temperature of the water flowing in the well-side piping 13 on the cold water well 12 side, and outputs the measurement result to the control device 50.

[0034] The water thermometer 15 on the hot water well 11 side is provided midway in the well-side piping 13 leading from the heat exchanger 14 to the hot water well 11. For example, the water thermometer 15 on the hot water well 11 side may be provided at a position on the ground surface directly above the hot water well 11. The water thermometer 15 on the hot water well 11 side measures the temperature of the water flowing in the well-side piping 13 on the hot water well 11 side and outputs the measurement result to the control device 50.

[0035] During cooling operation (in cold energy utilization mode), the water thermometer 15 on the cold water well 12 side functions as a water thermometer that measures the temperature of water pumped from the pumping well. At that time, the water thermometer 15 on the cold water well 12 side outputs the measurement result as the pumping water temperature to the control device 50. On the other hand, during this cooling operation, the water thermometer 15 on the hot water well 11 side functions as a water thermometer that measures the temperature of water returned to the return well. At that time, the water thermometer 15 on the hot water well 11 side outputs the measurement result as the return water temperature to the control device 50.

[0036] During heating operation (heat utilization mode), the water thermometer 15 on the hot water well 11 side functions as a water thermometer that measures the temperature of water pumped from the pumping well. At that time, the water thermometer 15 on the hot water well 11 side outputs the measurement result as the pumping water temperature to the control device 50. On the other hand, during this heating operation, the water thermometer 15 on the cold water well 12 side functions as a water thermometer that measures the temperature of water returned to the return well. At that time, the water thermometer 15 on the cold water well 12 side outputs the measurement result as the return water temperature to the control device 50.

[0037] (Configuration of water level gauge)

[0038] The water level meter 16 on the cold water well 12 side is provided inside the cold water well 12. The water level meter 16 on the cold water well 12 side measures the water level inside the cold water well 12 and outputs the measurement result to the control device 50.

[0039] The water level meter 16 on the hot water well 11 side is provided inside the hot water well 11. The water level meter 16 on the hot water well 11 side measures the water level inside the hot water well 11 and outputs the measurement result to the control device 50.

[0040] During cooling operation (cold energy utilization mode), the water level gauge 16 on the cold water well 12 side functions as a water level gauge that measures the pumping side water level, which is the water level of the pumping well. At that time, the water level gauge 16 on the cold water well 12 side outputs the measurement result to the control device 50 as the pumping side water level. On the other hand, during this cooling operation, the water level gauge 16 on the hot water well 11 side functions as a water level gauge that measures the return side water level, which is the water level of the return well. At that time, the water level gauge 16 on the hot water well 11 side outputs the measurement result to the control device 50 as the return side water level.

[0041] During heating operation (heat utilization mode), the water level gauge 16 on the hot water well 11 side functions as a water level gauge that measures the pumping side water level, which is the water level of the pumping well. At that time, the water level gauge 16 on the hot water well 11 side outputs the measurement result to the control device 50 as the pumping side water level. On the other hand, during this heating operation, the water level gauge 16 on the cold water well 12 side functions as a water level gauge that measures the return side water level, which is the water level of the return well. At that time, the water level gauge 16 on the cold water well 12 side outputs the measurement result to the control device 50 as the return side water level.

[0042] For example, each water level meter 16 measures the water level as the distance from the water surface to the position where the water level meter 16 is set. For example, each water level meter 16 may be installed to measure the water level shown in Fig. 2 when the water level is natural. For example, each water level meter 16 may be installed to measure the water level shown in Fig. 3 when pumping and returning water.

[0043] (Configuration of Geothermal Heat Utilization Circuit) The geothermal heat utilization circuit 20 is provided between the heat exchanger 14 and the device AA. The geothermal heat utilization circuit 20 mediates and controls the heat exchange that takes place between the heat exchanger 14 and the device AA in response to commands from the control device 50. For example, the geothermal heat utilization circuit 20 may include a heat pump 21, a flow rate control device 22, and a main pipe 23.

[0044] (Configuration of Heat Pump) The heat pump 21 includes a condenser, an evaporator, a compressor, etc. For example, the heat pump 21 is a turbo heat pump. The heat pump 21 is provided between the heat exchanger 14 and the flow rate control device 22. The heat pump 21 cools or heats the heat medium that has exchanged heat with the water in the well-side piping 13 in the heat exchanger 14. As a result, the heat pump 21 supplies the cold or hot stored heat obtained from the water in the well-side piping 13 to the device AA, while recovering the exhaust hot or cold heat discharged from the device AA and storing it in the water in the well-side piping 13 via the heat exchanger 14.

[0045] During cooling operation (cold energy utilization mode), the heat pump 21 provides the equipment AA with the stored cold heat obtained from the well-side piping 13 via the heat exchanger 14 and the heat medium flowing between the heat pump 21 and the heat exchanger 14 and the heat medium flowing between the heat pump 21 and the equipment AA. On the other hand, the heat pump 21 stores the exhaust hot heat discharged from the equipment AA in the water in the well-side piping 13 via the heat medium flowing between the heat pump 21 and the equipment AA and the heat exchanger 14, and also via the heat exchanger 14.

[0046] During heating operation (heat utilization mode), the heat pump 21 provides the stored heat obtained from the well-side piping 13 to the equipment AA via the heat exchanger 14 and the heat medium flowing between the heat pump 21 and the heat exchanger 14 and the heat medium flowing between the heat pump 21 and the equipment AA. On the other hand, the heat pump 21 stores the exhaust cold heat discharged from the equipment AA in the water in the well-side piping 13 via the heat medium flowing between the heat pump 21 and the equipment AA and the heat exchanger 14, and also via the heat exchanger 14.

[0047] (Configuration of Flow Rate Control Device) The flow rate control device 22 adjusts the flow rate FL of the heat medium flowing from the geothermal utilization circuit 20 to the device AA. As shown in Fig. 4, for example, the flow rate control device 22 may include a bypass valve 223 to adjust the flow rate FL by self-bypassing. Furthermore, the flow rate control device 22 may include a pump 221 and an electric valve 222 in the path connecting the heat pump 21 and the main pipe 23 to adjust the flow rate FL.

[0048] (Configuration of Main Pipe) The main pipe 23 extends from the flow rate control device 22 to the device AA. The main pipe 23 connects the flow rate control device 22 and the device AA so that the heat medium can circulate between the flow rate control device 22 and the device AA.

[0049] (Configuration of the auxiliary heat supply equipment) The auxiliary heat supply equipment 30 assists in at least one of the hot heat supply and cold heat supply performed by the heat source well equipment 10 to the equipment AA. When the equipment AA is using cooling, the auxiliary heat supply equipment 30 supplies cold heat to the equipment AA and recovers waste hot heat from the equipment AA. When the equipment AA is using heating, the auxiliary heat supply equipment 30 supplies hot heat to the equipment AA and recovers waste cold heat from the equipment AA.

[0050] The auxiliary heat supply equipment 30 includes a plurality of heat source units 31 and auxiliary piping 32. Each heat source unit 31 supplements at least one of the cold heat and hot heat supplied to equipment AA. For example, the plurality of heat source units 31 include a turbo chiller, an air-cooled heat pump, an absorption chiller / heater, etc. The auxiliary piping 32 extends from the plurality of heat source units 31 to the equipment AA. The auxiliary piping 32 connects the plurality of heat source units 31 and the equipment AA so that a heat medium can circulate between the plurality of heat source units 31 and the equipment AA.

[0051] For example, the auxiliary heat supply equipment 30 may be provided with an auxiliary flow control device 33 in the auxiliary piping 32. In this case, the auxiliary flow control device 33 has a bypass valve, a pump, and an electric valve similar to those of the flow control device 22, and adjusts the flow rate of the refrigerant flowing between the auxiliary heat supply equipment 30 and equipment AA in response to a command from the control device 50.

[0052] 5, the control device 50 functionally includes a return water temperature acquisition unit 511 and a flow rate control unit 512. For example, the control device 50 may further functionally include a heat source machine control unit 513, a pumped water side water level acquisition unit 514, a pumped water flow rate control unit 515, a return water side water level acquisition unit 516, and a return water flow rate control unit 517.

[0053] The control device 50 includes, as its hardware configuration, a CPU 51, a memory 52, a communication interface 53, and a recording medium 54.

[0054] The CPU 51 is a processor that performs various functions by operating in accordance with a pre-prepared program. The functions of the CPU 51 will be described later.

[0055] The memory 52 has a storage area necessary for the operation of the CPU 51 .

[0056] The communication interface 53 is a connection interface for connecting to other devices via a communication line or the like, and is configured to be able to send commands and responses to other devices and receive commands and responses from other devices.

[0057] The recording medium 54 is a local recording medium provided within the housing of the control device 50, and is a large-capacity storage device such as an HDD or SSD.

[0058] Next, the functions of the CPU 51 of the control device 50 will be described. The CPU 51 operates according to a pre-prepared program, thereby fulfilling the functions of the return water temperature acquisition unit 511 and the flow rate control unit 512, as described above. Furthermore, the CPU 51 may operate according to a pre-prepared program, thereby fulfilling the functions of the heat source machine control unit 513, the pumped water side water level acquisition unit 514, the pumped water flow rate control unit 515, the return water side water level acquisition unit 516, and the return water flow rate control unit 517, as described above.

[0059] The return water temperature acquisition unit 511 acquires the measurement result of the water thermometer 15 on the cold water well 12 side or the water thermometer 15 on the hot water well 11 side as the return water temperature to the return well. The pumping side water level acquisition unit 514 acquires the measurement result of the water level gauge 16 on the hot water well 11 side or the water level gauge 16 on the cold water well 12 side as the pumping side water level. The return water side water level acquisition unit 516 acquires the measurement result of the water level gauge 16 on the cold water well 12 side or the water level gauge 16 on the hot water well 11 side as the return water side water level.

[0060] The flow rate control unit 512 controls the flow rate FL by controlling the flow rate control device 22 based on the acquired return water temperature. For example, the flow rate control unit 512 controls the flow rate FL by controlling the flow rate control device 22 based on the acquired pumped water level. For example, the flow rate control unit 512 controls the flow rate FL by controlling the flow rate control device 22 based on the acquired return water level.

[0061] For example, the flow rate control unit 512 may adjust the flow rate of refrigerant flowing between the auxiliary heat supply equipment 30 and equipment AA by controlling the auxiliary flow rate control device 33 based on the acquired return water temperature. For example, the flow rate control unit 512 may adjust the flow rate of refrigerant flowing between the auxiliary heat supply equipment 30 and equipment AA by controlling the auxiliary flow rate control device 33 based on the acquired pumped water side water level. For example, the flow rate control unit 512 may adjust the flow rate of refrigerant flowing between the auxiliary heat supply equipment 30 and equipment AA by controlling the auxiliary flow rate control device 33 based on the acquired return water side water level.

[0062] The heat source machine control unit 513 may control the start and stop of each heat source machine 31 based on the acquired return water temperature. For example, the heat source machine control unit 513 may control the start and stop of each heat source machine 31 based on the acquired pumped water side water level. For example, the heat source machine control unit 513 may control the start and stop of each heat source machine 31 based on the acquired return water side water level. For example, the heat source machine control unit 513 may perform step-up / step-down control of multiple heat source machines 31.

[0063] The pumping flow rate control unit 515 controls the pumping flow rate from the pumping well based on the acquired pumping-side water level. The return flow rate control unit 517 controls the return flow rate to the return well based on the acquired return-side water level.

[0064] (Operation of the Control Device) An example of the operation of the control device 50 of this embodiment will be described. The operation of the control device 50 corresponds to an embodiment of a control method. The control device 50 performs each step shown in Figs. 6 to 9 .

[0065] (Operation of Return Water Temperature Control) First, the operation of the return water temperature control will be described. When the geothermal utilization system 1 is started, as shown in Fig. 6, the control device 50 determines whether the device AA is in cooling operation (ST00).

[0066] (Return water temperature control during cooling operation) If it is determined in ST00 that the system is in cooling operation (ST00: Yes), the return water temperature acquisition unit 511 acquires the measurement result of the water thermometer 15 on the hot water well 11 side as the return water temperature, and determines whether the acquired return water temperature is higher than a first startup temperature (e.g., 24°C) at which the heat source unit 31 should be started (ST01). For example, the first startup temperature is a preset value.

[0067] In ST01, if it is determined that the acquired return water temperature is higher than the first startup temperature (ST01: Yes), the heat source machine control unit 513 determines whether there is a heat source machine 31 (another heat source machine) among the multiple heat source machines 31 that can be started (ST02).

[0068] If it is determined in ST02 that there is a heat source unit 31 that can be activated (ST02: Yes), the heat source unit control unit 513 activates the heat source unit 31 that can be activated (ST03), and the control device 50 returns to executing ST01. For example, in ST03, the heat source unit control unit 513 first activates one of the heat source units 31 that can be activated (this setting can be changed). If there are multiple heat source units 31 that can be activated, the heat source unit control unit 513 can perform step-up / step-down control by repeating ST01 to ST03. In this case, the heat source unit control unit 513 may perform step-up / step-down control by monitoring the amount of heat or flow rate supplied to device AA. On the other hand, the flow rate control unit 512 controls the flow rate FL so that the return water temperature of the heat source well facility 10 is within a predetermined tolerance (below a predetermined upper limit), as described below, thereby suppressing the load on the heat source well facility 10.

[0069] If it is determined in ST02 that there is no heat source unit 31 that can be started (ST02: No), the control device 50 determines whether or not protection of the aquifer LY should be prioritized over ensuring the air conditioning capacity of the device AA (ST04). For example, the control device 50 may determine whether or not protection of the aquifer LY should be prioritized over ensuring the air conditioning capacity of the device AA in accordance with guidelines input by a user or the like.

[0070] If it is determined in ST04 that protection of the aquifer LY should be prioritized (ST04: Yes), the flow rate control unit 512 controls the flow rate FL (ST05), and the control device 50 returns to performing ST01. For example, in ST05, the flow rate control unit 512 may perform control to open the bypass valve 223 to reduce the flow rate FL. This control makes it possible to reduce the load on the self-bypass and control the return water temperature. Furthermore, in ST05, the flow rate control unit 512 may control the auxiliary flow control device 33 to increase the flow rate of the heat medium (cooling medium) flowing between the auxiliary heat supply equipment 30 and the equipment AA.

[0071] If it is determined in ST04 that the air conditioning capacity of device AA should be ensured (ST04: No), the control device 50 stops the heat supply from the geothermal utilization system 1 to device AA (ST06). After that, the user etc. considers using another system that can replace the geothermal utilization system 1 and ensure the air conditioning capacity of device AA.

[0072] If it is determined in ST01 that the acquired return water temperature is not higher than the first start-up temperature (ST01: No), the return water temperature acquisition unit 511 determines whether the acquired return water temperature is lower than a first stop temperature (e.g., 20°C) at which the heat source unit 31 should be stopped (ST07). For example, the first stop temperature is a preset value. Here, when the geothermal utilization system 1 performs cooling operation on the device AA, the first stop temperature is set lower than the first start-up temperature to provide hysteresis between the start-up condition and the stop condition of the heat source unit 31.

[0073] In ST07, if it is not determined that the acquired return water temperature is lower than the first stop temperature (ST07: No), the control device 50 returns to performing ST01.

[0074] In ST07, if it is determined that the acquired return water temperature is lower than the first stop temperature (ST07: Yes), the heat source machine control unit 513 determines whether there is any heat source machine 31 that is running among the multiple heat source machines 31 (heat source machines other than the heat source machines included in the heat source well equipment 10) (ST08).

[0075] If it is determined in ST08 that there is a heat source unit 31 that is currently running (ST08: Yes), the heat source unit control unit 513 stops the heat source unit 31 that is currently running (ST09), and the control device 50 returns to executing ST01.

[0076] In ST08, if it is determined that there is no heat source unit 31 that is currently running (ST08: No), the control device 50 returns to performing ST01.

[0077] If it is not determined in ST00 that the device is in cooling operation (ST00: No), the control device 50 determines whether the device AA is in heating operation (ST10).

[0078] If it is not determined in ST10 that heating operation is in progress (ST10: No), the control device 50 performs other control such as causing the heat source well equipment 10 to perform cold heat storage operation or hot heat storage operation for the heat source well equipment 10 (ST11).

[0079] (Return water temperature control during heating operation) If it is determined in ST10 that the system is in heating operation (ST10: Yes), as shown in Fig. 7 , the return water temperature acquisition unit 511 acquires the measurement result of the water thermometer 15 on the cold water well 12 side as the return water temperature, and determines whether the acquired return water temperature is lower than a second startup temperature (e.g., 8°C) at which the heat source unit 31 should be started (ST21). For example, the second startup temperature is a preset value.

[0080] In ST21, if it is determined that the acquired return water temperature is lower than the second startup temperature (ST21: Yes), the heat source machine control unit 513 determines whether there is a heat source machine 31 (another heat source machine) among the multiple heat source machines 31 that can be started (ST22).

[0081] If it is determined in ST22 that there is a heat source unit 31 that can be activated (ST22: Yes), the heat source unit control unit 513 activates the heat source unit 31 that can be activated (ST23), and the control device 50 returns to executing ST21. For example, in ST23, the heat source unit control unit 513 first activates one of the heat source units 31 that can be activated (this setting can be changed). If there are multiple heat source units 31 that can be activated, the heat source unit control unit 513 can perform step-up / step-down control by repeating ST21 to ST23. In this case, the heat source unit control unit 513 may perform step-up / step-down control by monitoring the amount of heat or flow rate supplied to device AA. On the other hand, the flow rate control unit 512 controls the flow rate FL so that the return water temperature of the heat source well facility 10 is within a predetermined tolerance (above a predetermined lower limit), as described below, thereby suppressing the load on the heat source well facility 10.

[0082] If it is determined in ST22 that there is no heat source unit 31 that can be started (ST22: No), the control device 50 determines whether or not protection of the aquifer LY should be prioritized over ensuring the air conditioning capacity of the device AA (ST24). For example, the control device 50 may determine whether or not protection of the aquifer LY should be prioritized over ensuring the air conditioning capacity of the device AA in accordance with guidelines input by a user or the like.

[0083] If it is determined in ST24 that protection of the aquifer LY should be prioritized (ST24: Yes), the flow rate control unit 512 controls the flow rate FL (ST25), and the control device 50 returns to performing ST21. For example, in ST25, the flow rate control unit 512 may perform control to open the bypass valve 223 to reduce the flow rate FL. This control makes it possible to reduce the load on the self-bypass and control the return water temperature. Furthermore, in ST25, the flow rate control unit 512 may control the auxiliary flow rate control device 33 to increase the flow rate of the heat medium (hot heat medium) flowing between the auxiliary heat supply equipment 30 and the equipment AA.

[0084] If it is determined in ST24 that the air conditioning capacity of device AA should be ensured (ST24: No), the control device 50 stops the heat supply from the geothermal utilization system 1 to device AA (ST26). After that, the user etc. considers using another system that can replace the geothermal utilization system 1 and ensure the air conditioning capacity of device AA.

[0085] If it is determined in ST21 that the acquired return water temperature is not lower than the second start-up temperature (ST21: No), the return water temperature acquisition unit 511 determines whether the acquired return water temperature is higher than a second stop temperature (e.g., 12°C) at which the heat source unit 31 should be stopped (ST27). For example, the second stop temperature is a preset value. Here, when the geothermal utilization system 1 performs heating operation on the device AA, the second stop temperature is set higher than the second start-up temperature to provide hysteresis between the start-up condition and the stop condition of the heat source unit 31.

[0086] In ST27, if it is not determined that the acquired return water temperature is higher than the second stop temperature (ST27: No), the control device 50 returns to performing ST21.

[0087] If it is determined in ST27 that the acquired return water temperature is higher than the second stop temperature (ST27: Yes), the heat source machine control unit 513 determines whether there is any heat source machine 31 that is running among the multiple heat source machines 31 (heat source machines other than the heat source machines included in the heat source well equipment 10) (ST28).

[0088] If it is determined in ST28 that there is a heat source unit 31 that is currently running (ST28: Yes), the heat source unit control unit 513 stops the heat source unit 31 that is currently running (ST29), and the control device 50 returns to performing ST21.

[0089] If it is determined in ST28 that there is no heat source unit 31 that is currently running (ST28: No), the control device 50 returns to performing ST21.

[0090] (Operation of Water Level Control of Pumping Well) The operation of water level control of the pumping well will be described.

[0091] When the geothermal energy utilization system 1 is started, as shown in FIG. 8 , the pumping-side water level acquisition unit 514 acquires the measurement result of the pumping well-side water level meter 16 as the pumping-side water level and determines whether the acquired pumping-side water level is higher than a first limit water level (e.g., 3 m) (ST41). For example, the first limit water level is a preset value. Here, the set first limit water level is the water level below which the flow rate of pumped water should be restricted and the heat source unit 31 should be started. Note that in this water level control during cooling operation, the pumping well is the cold water well 12, and the return well is the hot water well 11. On the other hand, in this water level control during heating operation, the pumping well is the hot water well 11, and the return well is the cold water well 12.

[0092] In ST41, if it is determined that the acquired pumping side water level is not higher than the first limit water level (determined to be below the first limit water level) (ST41: No), the heat source machine control unit 513 determines whether there is a heat source machine 31 (another heat source machine) among the multiple heat source machines 31 that can be started (ST42).

[0093] If it is determined in ST42 that there is a heat source machine 31 that can be started (ST42: Yes), the heat source machine control unit 513 starts the heat source machine 31 that can be started (ST43), and the control device 50 returns to executing ST41. For example, in ST43, the heat source machine control unit 513 first starts one heat source machine 31 that can be started (this setting can be changed). If there are multiple heat source machines 31 that can be started, the heat source machine control unit 513 can perform step-up / step-down control by repeating ST41 to ST43. In this case, the heat source machine control unit 513 may perform step-up / step-down control by checking the amount of heat or flow rate supplied to device AA.

[0094] Additionally, in ST43, the pumping flow rate control unit 515 may control the pumping flow rate from the pumping well by limiting the capacity of the submersible pump on the pumping well side or by stopping the operation of the submersible pump PP on the pumping well side. On the other hand, the flow rate control unit 512 may control the flow rate adjustment device 22 to reduce the flow rate FL so that the return water temperature of the heat source well equipment 10 is within the allowable value, thereby suppressing the load on the heat source well equipment 10. Furthermore, the flow rate control unit 512 may control the auxiliary flow rate adjustment device 33 to increase the flow rate of the heat medium flowing between the auxiliary heat supply equipment 30 and equipment AA.

[0095] If it is determined in ST41 that the acquired pumping-side water level is higher than the first limit water level (ST41: Yes), it is determined whether the acquired pumping-side water level is lower than a first release water level (e.g., 10 m) (ST44). For example, the first release water level is a preset value. Here, the set first release water level is the water level at which the pumping flow rate restriction should be released and the heat source unit 31 should be stopped when the water level reaches this water level or higher. Furthermore, to provide hysteresis between the start and stop conditions of the heat source unit 31, the first release water level is set higher than the first limit water level.

[0096] In ST44, if it is determined that the acquired pumping-side water level is lower than the first release water level (ST44: Yes), the control device 50 determines that the pumping restriction should not be released and returns to executing ST41.

[0097] In ST44, if the acquired pumping side water level is not determined to be lower than the first release water level (determined to be higher than the first release water level) (ST44: No), the heat source machine control unit 513 determines whether there is a heat source machine 31 that is running among the multiple heat source machines 31 (heat source machines other than the heat source machines included in the heat source well equipment 10), as there is a possibility that the pumping restriction can be lifted (ST45).

[0098] If it is determined in ST45 that there is a heat source unit 31 that is running (ST45: Yes), the heat source unit control unit 513 stops the running heat source unit 31 (ST46), and the control device 50 returns to executing ST41. At this time, the pumping flow rate control unit 515 may increase the pumping flow rate from the pumping well by removing the limit on the capacity of the submersible pump PP on the pumping well side or by starting the operation of the submersible pump PP on the pumping well side. On the other hand, the flow rate control unit 512 may control the flow rate control device 22 to increase the flow rate FL and the auxiliary flow rate control device 33 to decrease the flow rate of the heat medium flowing between the auxiliary heat supply equipment 30 and the equipment AA.

[0099] In ST45, if it is determined that there is no heat source unit 31 that is currently running (ST45: No), the control device 50 returns to performing ST41.

[0100] If it is determined in ST42 that there is no heat source unit 31 that can be activated (ST42: No), the control device 50 stops the heat supply from the geothermal utilization system 1 to the device AA (ST47). After that, the user etc. considers maintenance of each device on the pumping well side, such as removing clogs from the screen of the pumping well.

[0101] (Operation of Water Level Control of Return Well) The operation of water level control of the return well will be described.

[0102] When the geothermal energy utilization system 1 is started, as shown in FIG. 9 , the return water level acquisition unit 516 acquires the measurement result of the return water well water level meter 16 as the return water level and determines whether the acquired return water level is lower than a second limit water level (e.g., 25 m) (ST61). For example, the second limit water level is a preset value. Here, the set second limit water level is the water level at which the return water flow rate should be restricted and the heat source unit 31 should be started if the water level exceeds this water level. Note that in this water level control during cooling operation, the return water well is the hot water well 11, and the pumping well is the cold water well 12. On the other hand, in this water level control during heating operation, the return water well is the cold water well 12, and the pumping well is the hot water well 11.

[0103] In ST61, if it is determined that the acquired return water level is not lower than the second limit water level (determined to be above the second limit water level) (ST61: No), the heat source machine control unit 513 determines whether there is a heat source machine 31 (another heat source machine) among the multiple heat source machines 31 that can be started (ST62).

[0104] If it is determined in ST62 that there is a heat source unit 31 that can be started (ST62: Yes), the heat source unit control unit 513 starts the heat source unit 31 that can be started (ST63), and the control device 50 returns to executing ST61. For example, in ST63, the heat source unit control unit 513 first starts one of the heat source units 31 that can be started (this setting can be changed). If there are multiple heat source units 31 that can be started, the heat source unit control unit 513 can perform step-up / step-down control by repeating ST61 to ST63. In this case, the heat source unit control unit 513 may perform step-up / step-down control by checking the amount of heat or flow rate supplied to device AA.

[0105] Additionally, in ST63, the return water flow rate control unit 517 may control the return water flow rate to the return well by limiting the capacity of the submersible pump PP on the pumping well side or by stopping the operation of the submersible pump PP on the pumping well side. On the other hand, the flow rate control unit 512 may control the flow rate adjustment device 22 to reduce the flow rate FL so that the return water temperature of the heat source well facility 10 is within the allowable value, thereby suppressing the load on the heat source well facility 10. Furthermore, the flow rate control unit 512 may control the auxiliary flow rate adjustment device 33 to increase the flow rate of the heat medium flowing between the auxiliary heat supply facility 30 and the equipment AA.

[0106] If it is determined in ST61 that the acquired return water level is lower than the second limit water level (ST61: Yes), it is determined whether the acquired return water level is higher than a second release water level (e.g., 21 m) (ST64). For example, the second release water level is a preset value. Here, the set second release water level is the water level below which the return water flow restriction should be released and the heat source unit 31 should be stopped. Furthermore, to provide hysteresis between the start and stop conditions of the heat source unit 31, the second release water level is set lower than the second limit water level.

[0107] In ST64, if it is determined that the acquired return water level is higher than the second release water level (ST64: Yes), the control device 50 determines that the return water restriction should not be released yet and returns to executing ST61.

[0108] In ST64, if the acquired return water level is not determined to be higher than the second release water level (determined to be lower than the second release water level) (ST64: No), the heat source machine control unit 513 determines whether there is a heat source machine 31 that is running among the multiple heat source machines 31 (heat source machines other than the heat source machines included in the heat source well equipment 10), as there is a possibility that the return water restriction can be lifted (ST65).

[0109] If it is determined in ST65 that there is a heat source unit 31 that is running (ST65: Yes), the heat source unit control unit 513 stops the running heat source unit 31 (ST66), and the control device 50 returns to executing ST61. At this time, the return water flow rate control unit 517 may increase the return water flow rate to the return well by removing the limit on the capacity of the submersible pump PP on the pumping well side or by starting the operation of the submersible pump PP on the pumping well side. On the other hand, the flow rate control unit 512 may control the flow rate control device 22 to increase the flow rate FL and the auxiliary flow rate control device 33 to decrease the flow rate of the heat medium flowing between the auxiliary heat supply equipment 30 and the equipment AA.

[0110] In ST65, if it is determined that there is no heat source unit 31 that is currently running (ST65: No), the control device 50 returns to performing ST61.

[0111] If it is determined in ST62 that there is no heat source unit 31 that can be activated (ST62: No), the control device 50 stops the heat supply from the geothermal utilization system 1 to the device AA (ST67). After that, the user etc. considers maintenance of each device on the return well side, such as removing clogs from the return well screen.

[0112] (Actions and Effects) According to this embodiment, the control device 50 controls the flow rate FL based on the return water temperature. As a result, when the load heat quantity required by the device AA is large, the control device 50 can limit the heat exhaust from the device AA to the heat source well facility 10. Therefore, regardless of the load heat quantity required by the device AA, the control device 50 can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well. Therefore, the control device 50 is less likely to affect the underground environment.

[0113] As a comparative example, the geothermal energy utilization system disclosed in Patent Document 1 controls the return water temperature by controlling the flow rate from the pumping well to the return water well. In this comparative geothermal energy utilization system, when the amount of waste heat from the equipment to the aquifer is the same, the temperature difference between the pumped water temperature and the inlet water temperature is determined by the pumped water temperature and the set return water temperature, so only the flow rate is variable. Therefore, in the comparative geothermal energy utilization system, the pumped water volume is limited by the well's performance. Therefore, when the equipment requires a large heat load, the return water temperature will naturally exceed the upper (lower) limit even if the pumped water volume is maximized. Furthermore, in the comparative geothermal energy utilization system, the heat stored in the previous season is consumed at the end of summer or winter, causing the groundwater temperature to approach the initial groundwater temperature, reducing the available temperature difference. Therefore, when the equipment is under heavy load, the return water temperature is likely to exceed the upper (lower) limit. On the other hand, in a geothermal energy utilization system, it is desirable for the return water temperature to be a temperature that does not alter the water quality of the aquifer. For example, it is desirable for the return water temperature to be a temperature that does not alter the microbial community structure, etc. However, in the geothermal energy utilization system of the comparative example, the return water temperature may exceed the upper limit (lower limit), which is likely to alter the water quality of the aquifer. In contrast, the control device 50 controls the flow rate FL based on the return water temperature as described above, so that the groundwater temperature can be adjusted to a temperature that does not affect the underground environment and returned to the return well, regardless of the heat load required by device AA. Therefore, the control device 50 is unlikely to alter the water quality of the aquifer.

[0114] According to this embodiment, the control device 50 controls the start and stop of the heat source device 31 based on the return water temperature, and can therefore start and stop the heat source device 31 according to the heat load required by device AA. As a result, when the heat load required by device AA is large, the control device 50 can share the heat load required by device AA between the heat source well facility 10 and the auxiliary heat supply facility 30. Therefore, regardless of the heat load required by device AA, the control device 50 can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well. Therefore, the control device 50 is less likely to affect the underground environment.

[0115] For example, the control device 50 can control the start and stop of the heat source unit 31 based on the return water temperature, thereby allocating the heat load required by equipment AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30, as shown in FIG. 10 . As a result, the control device 50 operates the heat source well equipment 10 with high efficiency, and when the return water temperature exceeds the upper limit even with the pumping rate at its maximum, it can start a heat source unit 31 separate from the heat source well equipment 10 and allocate the load to control (limit) the amount of heat discharged to the aquifer LY. Therefore, by controlling the start and stop of the heat source unit 31 based on the return water temperature as described above, the control device 50 can adjust the groundwater temperature to a temperature that is less likely to affect the underground environment and return it to the return well, regardless of the heat load required by equipment AA. Therefore, the control device 50 is less likely to cause changes to the water quality of the aquifer.

[0116] According to this embodiment, when the geothermal energy utilization system 1 performs cooling operation on the equipment AA, the first stop temperature at which the heat source unit 31 should be stopped is lower than the first start-up temperature at which the heat source unit 31 should be started, so the control device 50 can impart hysteresis to the start-up conditions and stop conditions of the heat source unit 31. For example, as shown in FIG. 11 , the control device 50 can impart hysteresis to the start-up conditions and stop conditions of the heat source unit 31. This allows the control device 50 to suppress, for example, oscillating operation between starting and stopping the heat source unit 31. Therefore, the control device 50 can stabilize the operation of the heat source unit 31.

[0117] According to this embodiment, when the geothermal energy utilization system 1 performs heating operation on the device AA, the second stop temperature at which the heat source device 31 should be stopped is higher than the second start-up temperature at which the heat source device 31 should be started, so the control device 50 can impart hysteresis to the start-up and stop conditions of the heat source device 31. This allows the control device 50 to suppress, for example, the oscillating operation of starting and stopping the heat source device 31. Therefore, the control device 50 can stabilize the operation of the heat source device 31.

[0118] According to this embodiment, the heat source unit control unit 513 performs step-up / down control to start up the heat source units 31 in a number corresponding to the heat load shared by the auxiliary heat supply equipment out of the heat load required by the equipment AA. Therefore, the control device 50 can efficiently use the multiple heat source units 31.

[0119] According to this embodiment, the pumping flow rate control unit 515 controls the pumping flow rate based on the pumping-side water level. This allows the control device 50 to limit fluctuations in the water level of the pumping well, such as a drop in the water level of the pumping well due to clogging of the pumping well screen. Therefore, the control device 50 can prevent breakdowns of the submersible pump PP of the pumping well due to dry running and progression of clogging of the pumping well. Therefore, the control device 50 enables long-term operation of the geothermal energy utilization system 1.

[0120] According to this embodiment, the heat source unit control unit 513 controls the start and stop of the heat source unit 31 based on the pumping-side water level. As a result, the control device 50 can supplement the heat load required by the device AA based on the pumping-side water level. Therefore, even if the heat source well equipment 10 alone cannot bear the heat load required by the device AA in order to maintain the pumping-side water level, the control device 50 can share the heat load required by the device AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, the control device 50 can control the geothermal utilization system 1 so as to supply the heat load required by the device AA.

[0121] For example, in the geothermal energy utilization system disclosed in Patent Document 1, pumping water at a rate exceeding the capacity of the heat source well can result in a significant drop in the water level on the pumping side, leading to dry running of the submersible pump PP and increased clogging due to increased flow velocity through the pumping screen. For example, a pumping limit is set during pumping tests when the heat source well is constructed. However, aging deterioration, such as clogging of the screen, can lead to significant fluctuations in the water level even at the same pumping rate. Therefore, limiting the pumping rate based on the water level and utilizing a separate heat source is desirable. On the other hand, for example, if a high-efficiency heat source well facility 10 is operated, and the drop in the water level on the pumping side exceeds a set value, the control device 50 can control the pumping flow rate and activate a heat source unit 31 separate from the heat source well facility 10 to allocate load. Therefore, the control device 50 can limit the pumping rate and utilize a separate heat source based on the pumping water level.

[0122] According to this embodiment, the first release water level, at which the pumped water flow rate restriction should be lifted and the heat source unit 31 should be stopped, is higher than the first limit water level, at which the pumped water flow rate should be restricted and the heat source unit 31 should be started. Therefore, the control device 50 can impart hysteresis to the start-up conditions and stop conditions of the heat source unit 31. For example, as shown in FIG. 12 , the control device 50 can impart hysteresis to the start-up conditions and stop conditions of the heat source unit 31. This allows the control device 50 to suppress, for example, oscillating operation between starting and stopping the heat source unit 31. Therefore, the control device 50 can stabilize the operation of the heat source unit 31.

[0123] According to this embodiment, the pumping flow rate control unit 515 controls the return water flow rate based on the return water level. This allows the control device 50 to limit fluctuations in the water level of the return well, such as a rise in the water level of the return well due to clogging of the return well screen. This allows the control device 50 to suppress, for example, the progression of clogging of the return well. Therefore, the control device 50 enables long-term operation of the geothermal energy utilization system 1.

[0124] According to this embodiment, the heat source machine control unit 513 controls the start and stop of the heat source machine 31 based on the return water level. As a result, the control device 50 can supplement the heat load required by the device AA based on the return water level. Therefore, even if the heat source well equipment 10 alone cannot bear the heat load required by the device AA in order to maintain the return water level, the control device 50 can share the heat load required by the device AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, the control device 50 can control the geothermal utilization system 1 so as to supply the heat load required by the device AA.

[0125] For example, in the geothermal energy utilization system disclosed in Patent Document 1, if water is injected at a rate exceeding the heat source well's capacity, the water level in the return well may rise significantly, leading to increased flow velocity through the return well's screen, which may cause clogging. For example, a return water volume limit is established during construction of the heat source well through a return water test. However, aging deterioration, such as clogging of the screen, can cause significant water level fluctuations even with the same return water volume. Therefore, limiting the return water volume based on the water level and utilizing a separate heat source are desirable. On the other hand, for example, if a high-efficiency heat source well facility 10 is operated, and the water level rise in the return well exceeds a set value, the control device 50 can control the return water flow rate and activate a heat source unit 31 separate from the heat source well facility 10 to allocate load. Therefore, the control device 50 can limit the return water volume and utilize a separate heat source based on the return water level.

[0126] According to this embodiment, the second release water level, at which the restriction on the return water flow rate should be released and the heat source unit 31 should be stopped, is lower than the second restriction water level, at which the return water flow rate should be restricted and the heat source unit 31 should be started, so the control device 50 can impart hysteresis to the start-up conditions and stop conditions of the heat source unit 31. This allows the control device 50 to suppress, for example, the oscillating operation of starting and stopping the heat source unit 31. Therefore, the control device 50 can stabilize the operation of the heat source unit 31.

[0127] According to this embodiment, the control device 50 uses both the heat source well facility 10 and the auxiliary heat supply facility 30. Therefore, while the heat source well facility 10 is a facility that treats the aquifer LY as a natural heat storage tank and utilizes nature, there is a possibility of unforeseen circumstances occurring, according to the control device 50, the auxiliary heat supply facility 30 serves as a backup for the heat source well facility 10.

[0128] According to the control device 50 of this embodiment, automatic control of return water temperature management is easy, which makes management easier for users and allows the construction of a general-purpose system that makes it easy to utilize geothermal energy.

[0129] <Modifications> In the example of the embodiment described above, the control device 50 controls both the flow rate FL based on the return water temperature and the start and stop of the heat source unit 31, but any control may be performed as long as the return water temperature can be controlled. As a modification, if the control device 50 can control the return water temperature, it may control at least one of the flow rate FL based on the return water temperature and the start and stop of the heat source unit 31. In this case, the geothermal utilization system 1 may include at least one of the configurations of the flow rate adjustment device 22 and the auxiliary heat supply equipment 30.

[0130] In the example of the above-described embodiment, the auxiliary heat supply equipment 30 includes a plurality of heat source units 31, but may include any device that can assist at least one of the hot heat supply and cold heat supply performed by the heat source well equipment 10 to the equipment AA. As a variation, the auxiliary heat supply equipment 30 may include a single heat source unit 31 instead of the plurality of heat source units 31. As another variation, the auxiliary heat supply equipment 30 may include a cooling tower instead of or in addition to the plurality of heat source units 31.

[0131] In the example of the above-described embodiment, the auxiliary heat supply equipment 30 includes a plurality of heat source units 31, but may include any device that can assist at least one of the hot heat supply and cold heat supply performed by the heat source well equipment 10 to the equipment AA. As a variation, the auxiliary heat supply equipment 30 may include a single heat source unit 31 instead of the plurality of heat source units 31. As another variation, the auxiliary heat supply equipment 30 may include a cooling tower instead of or in addition to the plurality of heat source units 31.

[0132] In the example of the embodiment described above, the geothermal heat utilization circuit 20 includes the heat pump 21, but may be configured in any way as long as it can mediate and control the heat exchange that occurs between the heat exchanger 14 and the equipment AA. As a modified example, the geothermal heat utilization circuit 20 may include a flow rate adjustment device 22 and a main pipe 23, and may not include the heat pump 21. In this case, the flow rate adjustment device 22 may adjust the flow rate of the heat medium that flows directly from the equipment AA side of the heat exchanger 14 to the equipment AA.

[0133] In the example of the above-described embodiment, the upper limit (lower limit) of the return water temperature is set in advance, but any setting may be used as long as the return water temperature can be controlled to a value that does not have a significant impact on the underground environment. As a modified example, since the upper limit (lower limit) of the return water temperature depends on the initial groundwater temperature of the area where the geothermal energy utilization system 1 is installed, the upper limit (lower limit) of the return water temperature in the control device 50 is not particularly limited and may be updated to a value that can be set as appropriate.

[0134] In the example of the embodiment described above, the flow rate control unit 512 controls the bypass valve 223, but any control may be performed as long as it can control the flow rate FL. As a modified example, in addition to or instead of controlling the bypass valve 223, the flow rate control unit 512 may control the flow rate FL by controlling the inverter of the pump 221 or controlling the aperture of the motor-operated valve 222. Furthermore, similar to the control over the flow rate control device 22, the flow rate control unit 512 may adjust the flow rate of the medium flowing from the auxiliary heat supply equipment 30 to the device AA by controlling the aperture of the bypass valve of the auxiliary flow rate control device 33, controlling the inverter of the pump of the auxiliary flow rate control device 33, or controlling the aperture of the motor-operated valve of the auxiliary flow rate control device 33.

[0135] In each of the above-described embodiments, a program for realizing the various functions of the control device 50 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to perform various processes. Here, the various processes of the CPU 51 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. The computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to a computer via a communication line or the like, and the computer that receives the program may execute the program.

[0136] <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.

[0137] <Additional Notes> The control device 50, the geothermal utilization system 1, the control method, and the program described in the above-described embodiment can be understood, for example, as follows.

[0138] (1) The control device 50 of the first aspect comprises a heat source well equipment 10 including a pumping well (cold water well 12 or hot water well 11), a return well (hot water well 11 or cold water well 12), well-side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well-side piping 13, and a geothermal heat utilization system 1 including a geothermal heat utilization circuit 20 provided between the heat exchanger 14 and equipment AA. The control device 50 comprises: a return water temperature acquisition unit 511 that acquires the return water temperature to the return well (hot water well 11 or cold water well 12); and a flow rate control unit 512 that controls the flow rate FL of the refrigerant flowing from the geothermal heat utilization circuit 20 to equipment AA based on the return water temperature.

[0139] According to this embodiment, the control device 50 controls the flow rate FL based on the return water temperature. This allows the control device 50 to limit the heat discharged from the device AA to the heat source well facility 10 when the load heat quantity required by the device AA is large. Therefore, regardless of the load heat quantity required by the device AA, the control device 50 can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the control device 50 is less likely to affect the underground environment.

[0140] (2) The control device 50 relating to the second aspect is the control device 50 of (1) which further includes an auxiliary heat supply equipment 30 provided in the equipment AA in parallel with the geothermal heat utilization circuit 20 and equipped with a heat source machine 31, and further includes a heat source machine control unit 513 which controls the start and stop of the heat source machine 31 based on the return water temperature.

[0141] According to this aspect, the control device 50 can start and stop the heat source unit 31 according to the heat load required by the equipment AA. As a result, when the heat load required by the equipment AA is large, the control device 50 can allocate the heat load required by the equipment AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, regardless of the heat load required by the equipment AA, the control device 50 can adjust the temperature of the groundwater to a temperature that does not have an impact on the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the control device 50 does not have an impact on the underground environment.

[0142] (3) The control device 50 according to the third aspect is the control device 50 of (2) in which, when the geothermal energy utilization system 1 performs air conditioning operation on the equipment AA, the first stop temperature at which the equipment should be stopped is lower than the first start temperature at which the equipment should be started.

[0143] According to this aspect, the control device 50 can provide hysteresis to the start-up conditions and stop-up conditions of the heat source device 31. This allows the control device 50 to suppress, for example, the oscillating operation of starting and stopping the heat source device 31. Therefore, the control device 50 can stabilize the operation of the heat source device 31.

[0144] (4) The control device 50 according to the fourth aspect is a control device 50 of (2) or (3) in which, when the geothermal energy utilization system performs heating operation on the equipment AA, the second stop temperature at which the shutdown should be performed is higher than the second start temperature at which the startup should be performed.

[0145] According to this aspect, hysteresis can be applied to the start and stop conditions of the device AA. This allows the control device 50 to suppress, for example, the oscillation between starting and stopping the device AA. Therefore, the control device 50 can stabilize the operation of the heat source device 31.

[0146] (5) The control device 50 relating to the fifth aspect is any one of the control devices 50 of (2) to (4) in which the heat source machine 31 has a plurality of heat source machines 31 and the heat source machine control unit 513 controls the increase / decrease in the number of stages of the plurality of heat source machines 31.

[0147] According to this aspect, the control device 50 can start up the heat source devices 31 in a number corresponding to the heat load amount shared by the auxiliary heat supply equipment 30 out of the heat load amount required by the equipment AA. Therefore, the control device 50 can efficiently use the multiple heat source devices 31.

[0148] (6) The control device 50 according to the sixth aspect is the control device 50 of (1), further including a pumping-side water level acquisition unit 514 that acquires the pumping-side water level, which is the water level of the pumping well (cold water well 12 or hot water well 11), and a pumping flow rate control unit 515 that controls the pumping flow rate from the pumping well (cold water well 12 or hot water well 11) based on the pumping-side water level.

[0149] According to this embodiment, the control device 50 controls the pumping flow rate based on the pumping-side water level. This allows the control device 50 to limit fluctuations in the water level of the pumping well (cold water well 12 or hot water well 11), such as a drop in the water level of the pumping well (cold water well 12 or hot water well 11) due to clogging of the screen of the pumping well (cold water well 12 or hot water well 11). Therefore, the control device 50 can prevent, for example, failures due to dry running of the submersible pump PP of the pumping well (cold water well 12 or hot water well 11) and progression of clogging of the pumping well (cold water well 12 or hot water well 11). Therefore, the control device 50 enables long-term operation of the geothermal energy utilization system 1.

[0150] (7) The control device 50 relating to the seventh aspect is the control device 50 of (6) in which the geothermal energy utilization system further includes an auxiliary heat supply facility 30 that is provided in the equipment in parallel with the geothermal energy utilization circuit 20 and includes a heat source unit 31, and further includes a heat source unit control unit 513 that controls the start and stop of the heat source unit 31 based on the pumping side water level.

[0151] According to this aspect, the control device 50 can supplement the heat load required by the device AA based on the pumping-side water level. Therefore, even if the heat source well facility 10 alone cannot bear the heat load required by the device AA in order to maintain the pumping-side water level, the control device 50 can share the heat load required by the device AA between the heat source well facility 10 and the auxiliary heat supply facility 30. Therefore, the control device 50 can control the geothermal utilization system 1 so as to supply the heat load required by the device AA.

[0152] (8) The control device 50 according to the eighth aspect is the control device 50 of (1), further including a return water side water level acquisition unit 516 that acquires the return water side water level, which is the water level of the return water well (hot water well 11 or cold water well 12), and a return water flow rate control unit 517 that controls the return water flow rate to the return water well (hot water well 11 or cold water well 12) based on the return water side water level.

[0153] According to this aspect, the pumping flow rate control unit 515 controls the return water flow rate based on the return water side water level. This allows the control device 50 to limit fluctuations in the water level of the return water well (hot water well 11 or cold water well 12), such as a rise in the water level of the return water well (hot water well 11 or cold water well 12) due to clogging of the screen of the return water well (hot water well 11 or cold water well 12). This allows the control device 50 to suppress the progression of clogging of the return water well (hot water well 11 or cold water well 12). Therefore, the control device 50 enables long-term operation of the geothermal energy utilization system 1.

[0154] (9) The control device 50 relating to the ninth aspect is the control device 50 of (8), in which the geothermal energy utilization system 1 further includes an auxiliary heat supply equipment 30 provided in the equipment AA in parallel with the geothermal energy utilization circuit 20 and equipped with a heat source machine 31, and further includes a heat source machine control unit 513 that controls the start and stop of the heat source machine 31 based on the return water side water level.

[0155] According to this aspect, the control device 50 can supplement the heat load required by the device AA based on the return water level. As a result, even if the heat source well facility 10 alone cannot bear the heat load required by the device AA in order to maintain the return water level, the control device 50 can share the heat load required by the device AA between the heat source well facility 10 and the auxiliary heat supply facility 30. Therefore, the control device 50 can control the geothermal energy utilization system 1 so as to supply the heat load required by the device AA.

[0156] (10) The control device 50 relating to the tenth aspect comprises a heat source well equipment 10 including a pumping well (cold water well 12 or hot water well 11), a return water well (hot water well 11 or cold water well 12), well side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return water well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well side piping 13, a geothermal heat utilization system 1 including a geothermal heat utilization circuit 20 provided between the heat exchanger 14 and equipment AA, and an auxiliary heat supply equipment 30 provided in the equipment in parallel with the geothermal heat utilization circuit 20 and equipped with a heat source unit 31; and a return water temperature acquisition unit 511 that acquires the return water temperature to the return water well (hot water well 11 or cold water well 12), and a heat source unit control unit 513 that controls the start and stop of the heat source unit 31 based on the return water temperature.

[0157] According to this aspect, the control device 50 can start and stop the heat source unit 31 according to the heat load required by the equipment AA. As a result, when the heat load required by the equipment AA is large, the control device 50 can allocate the heat load required by the equipment AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, regardless of the heat load required by the equipment AA, the control device 50 can adjust the temperature of the groundwater to a temperature that does not have an impact on the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the control device 50 does not have an impact on the underground environment.

[0158] (11) The geothermal energy utilization system 1 according to the eleventh aspect includes the control device 50 of any one of (1) to (10), the heat source well facility 10, and the geothermal energy utilization circuit 20.

[0159] According to this embodiment, the geothermal energy utilization system 1 controls the flow rate FL based on the return water temperature. This allows the geothermal energy utilization system 1 to limit the heat discharged from the equipment AA to the heat source well facility 10 when the load heat quantity required by the equipment AA is large. Therefore, regardless of the load heat quantity required by the equipment AA, the geothermal energy utilization system 1 can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the geothermal energy utilization system 1 is less likely to affect the underground environment.

[0160] (12) The control method according to the twelfth aspect acquires the return water temperature to the return water well (hot water well 11 or cold water well 12) of a geothermal energy utilization system 1 that includes a heat source well equipment 10 that includes a pumping well (cold water well 12 or hot water well 11), a return water well (hot water well 11 or cold water well 12), well side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return water well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well side piping 13, and a geothermal energy utilization circuit 20 that is provided between the heat exchanger 14 and equipment AA, and controls the flow rate FL of the refrigerant flowing from the geothermal energy utilization circuit 20 to equipment AA based on the return water temperature.

[0161] According to this aspect, the control method controls the flow rate FL based on the return water temperature. This allows the control method to limit the heat discharge from the equipment AA to the heat source well facility 10 when the load heat quantity required by the equipment AA is large. Therefore, regardless of the load heat quantity required by the equipment AA, the control method can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the control method is less likely to affect the underground environment.

[0162] (13) The control method of the thirteenth aspect acquires the return water temperature to the return water well (hot water well 11 or cold water well 12) of a geothermal energy utilization system 1, the geothermal energy utilization system 1 comprising a pumping well (cold water well 12 or hot water well 11), a return water well (hot water well 11 or cold water well 12), well-side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return water well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well-side piping 13, a geothermal energy utilization circuit 20 provided between the heat exchanger 14 and equipment AA, and an auxiliary heat supply equipment 30 provided in the equipment AA in parallel with the geothermal energy utilization circuit 20 and provided with a heat source unit 31, and controls the start and stop of the heat source unit 31 based on the return water temperature.

[0163] According to this aspect, the control method can start and stop the heat source unit 31 according to the heat load required by the equipment AA. As a result, when the heat load required by the equipment AA is large, the control method can share the heat load required by the equipment AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, regardless of the heat load required by the equipment AA, the control method can adjust the temperature of the groundwater to a temperature that does not have a significant impact on the underground environment and return the groundwater to the return well (hot water well 11 or cold water well 12). Therefore, the control method does not have a significant impact on the underground environment.

[0164] (14) The program relating to the fourteenth aspect causes a computer to acquire the return water temperature to the return water well (hot water well 11 or cold water well 12) of a geothermal energy utilization system 1 comprising a heat source well equipment 10 including a pumping well (cold water well 12 or hot water well 11), a return water well (hot water well 11 or cold water well 12), well side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return water well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well side piping 13, and a geothermal energy utilization circuit 20 provided between the heat exchanger 14 and equipment AA, and to control the flow rate FL of the refrigerant flowing from the geothermal energy utilization circuit 20 to equipment AA based on the return water temperature.

[0165] According to this embodiment, the program controls the flow rate FL based on the return water temperature. This allows the program to limit the heat discharge from the equipment AA to the heat source well facility 10 when the load heat quantity required by the equipment AA is large. Therefore, regardless of the load heat quantity required by the equipment AA, the program can adjust the temperature of the groundwater to a temperature that is less likely to affect the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the program is less likely to affect the underground environment.

[0166] (15) The program relating to the fifteenth aspect causes a computer to acquire the return water temperature to the return water well (hot water well 11 or cold water well 12) of a geothermal energy utilization system 1 comprising a pumping well (cold water well 12 or hot water well 11), a return water well (hot water well 11 or cold water well 12), well-side piping 13 extending from the pumping well (cold water well 12 or hot water well 11) to the return water well (hot water well 11 or cold water well 12), and a heat exchanger 14 provided midway along the well-side piping 13, a geothermal energy utilization circuit 20 provided between the heat exchanger 14 and equipment AA, and an auxiliary heat supply equipment 30 provided in the equipment AA in parallel with the geothermal energy utilization circuit 20 and provided with a heat source unit 31, and to control the start and stop of the heat source unit based on the return water temperature.

[0167] According to this aspect, the program can start and stop the heat source unit 31 according to the heat load required by the equipment AA. As a result, when the heat load required by the equipment AA is large, the program can share the heat load required by the equipment AA between the heat source well equipment 10 and the auxiliary heat supply equipment 30. Therefore, regardless of the heat load required by the equipment AA, the program can adjust the temperature of the groundwater to a temperature that has little impact on the underground environment and return it to the return well (hot water well 11 or cold water well 12). Therefore, the program has little impact on the underground environment.

[0168] The control device, geothermal heat utilization system, control method, and program disclosed herein have little impact on the underground environment.

[0169] 1 Geothermal heat utilization system 10 Heat source well equipment 11 Hot water well (return well or pumping well) 12 Cold water well (pumping well or return well) 13 Well side piping 14 Heat exchanger 15 Water thermometer 16 Water level gauge 20 Geothermal heat utilization circuit 21 Heat pump 22 Flow rate adjustment device 23 Main piping 30 Auxiliary heat supply equipment 31 Heat source machine 32 Auxiliary piping 33 Auxiliary flow rate adjustment device 50 Control device 51 CPU 52 Memory 53 Communication interface 54 Recording medium 131 First end 132 Second end 221 Pump 222 Motor-operated valve 223 Bypass valve 511 Return water temperature acquisition unit 512 Flow rate control unit 513 Heat source machine control unit 514 Pumping side water level acquisition unit 515 Pumping flow rate control unit 516 Return water side water level acquisition unit 517 Return water flow rate control unit AA Equipment FL Flow rate LY Aquifer PP Submersible pump VA Water injection valve VB Check valve

Claims

1. A control device comprising: a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping; a geothermal heat utilization circuit installed between the heat exchanger and an equipment; and an auxiliary heat supply equipment installed in the equipment in parallel with the geothermal heat utilization circuit and equipped with a heat source unit, the control device comprising: a return water temperature acquisition unit that acquires a return water temperature to the return water well of a geothermal heat utilization system; a flow rate control unit that controls the flow rate of refrigerant flowing from the geothermal heat utilization circuit to the equipment based on the return water temperature; and a heat source unit control unit that controls the start and stop of the heat source unit based on the return water temperature.

2. The control device according to claim 1, wherein when the geothermal energy utilization system performs cooling operation on the equipment, a first stop temperature at which the equipment should be stopped is lower than a first start-up temperature at which the equipment should be started.

3. The control device according to claim 1, wherein when the geothermal energy utilization system performs heating operation on the equipment, a second stop temperature at which the shutdown should be performed is higher than a second start-up temperature at which the startup should be performed.

4. The control device according to claim 1, wherein the heat source unit includes a plurality of heat source units, and the heat source unit control section controls the increase and decrease in stages of the plurality of heat source units.

5. A control device comprising: a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger provided midway along the well-side piping; and a geothermal heat utilization circuit provided between the heat exchanger and an equipment; a return water temperature acquisition unit that acquires the return water temperature to the return well; a flow rate control unit that controls the flow rate of refrigerant flowing from the geothermal heat utilization circuit to the equipment based on the return water temperature; a pumping side water level acquisition unit that acquires the pumping side water level, which is the water level of the pumping well; and a pumping flow rate control unit that controls the pumping flow rate from the pumping well based on the pumping side water level.

6. The control device according to claim 5, wherein the geothermal energy utilization system further comprises an auxiliary heat supply facility provided in the equipment in parallel with the geothermal energy utilization circuit and equipped with a heat source unit, and further comprises a heat source unit control unit that controls the start and stop of the heat source unit based on the pumping side water level.

7. A control device for a geothermal energy utilization system comprising: a heat source well equipment comprising a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger provided midway along the well-side piping; and a geothermal energy utilization circuit provided between the heat exchanger and an equipment; a return water temperature acquisition unit for acquiring a return water temperature to the return well; and a flow rate control unit for controlling the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; a return water side water level acquisition unit for acquiring the return water side water level, which is the water level of the return well; and a return water flow rate control unit for controlling the return water flow rate to the return well based on the return water side water level.

8. The control device according to claim 7, wherein the geothermal energy utilization system further comprises an auxiliary heat supply equipment provided in the equipment in parallel with the geothermal energy utilization circuit and equipped with a heat source unit, and further comprises a heat source unit control unit that controls the start and stop of the heat source unit based on the return water level.

9. A geothermal energy utilization system comprising: a control device according to any one of claims 1 to 8; the heat source well facility; and the geothermal energy utilization circuit.

10. A control method for a geothermal energy utilization system comprising a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, a geothermal energy utilization circuit installed between the heat exchanger and an equipment, and an auxiliary heat supply equipment installed in the equipment in parallel with the geothermal energy utilization circuit and equipped with a heat source unit, the control method comprising: acquiring the return water temperature to the return well; controlling the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; and controlling the start and stop of the heat source unit based on the return water temperature.

11. A control method for a geothermal energy utilization system comprising a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and equipment, the control method comprising: acquiring a return water temperature to the return well; controlling the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; acquiring a pumping side water level, which is the water level of the pumping well; and controlling the pumping flow rate from the pumping well based on the pumping side water level.

12. A control method for a geothermal energy utilization system comprising a heat source well equipment including a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and equipment, the control method comprising: acquiring a return water temperature to the return well; controlling the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; acquiring a return water side water level, which is the water level of the return well; and controlling the return water flow rate to the return well based on the return water side water level.

13. A program that causes a computer to execute the following: acquire the return water temperature to the return well of a geothermal energy utilization system comprising a heat source well equipment comprising a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, a geothermal energy utilization circuit installed between the heat exchanger and an equipment, and an auxiliary heat supply equipment installed in the equipment in parallel with the geothermal energy utilization circuit and comprising a heat source unit; control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; and control the start and stop of the heat source unit based on the return water temperature.

14. A program that causes a computer to execute the following steps: acquire the return water temperature to the return well of a geothermal energy utilization system comprising a heat source well equipment comprising a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and equipment; control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; acquire the pumping side water level, which is the water level of the pumping well; and control the pumping flow rate from the pumping well based on the pumping side water level.

15. A program that causes a computer to execute the following steps: acquire the return water temperature to the return well of a geothermal energy utilization system comprising a heat source well equipment comprising a pumping well, a return well, a well-side piping extending from the pumping well to the return well, and a heat exchanger installed midway along the well-side piping, and a geothermal energy utilization circuit installed between the heat exchanger and equipment; control the flow rate of refrigerant flowing from the geothermal energy utilization circuit to the equipment based on the return water temperature; acquire the return water side water level, which is the water level of the return well; and control the return water flow rate to the return well based on the return water side water level.

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