Geothermal power generation system

Abstract

To realize a geothermal power generation system which recovers heat energy from a geothermal field in a more efficient manner to improve power generation efficiency.SOLUTION: A geothermal power generation system, which generates power using thermal energy in a geothermal zone, comprises: at least two wells; a power generation facility that extracts a geothermal fluid generated in the geothermal zone from any one of the at least two wells and generates power using thermal energy contained in the geothermal fluid; and a geothermal heat exchanger that performs heat exchange on the fluid circulating in a flow path configured as a closed loop-type flow path in the geothermal zone. The geothermal heat exchanger is provided at any one point between the at least two wells.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a geothermal power generation system. [Background technology]

[0002] Geothermal power generation, which uses geothermal steam from geothermal zones and hot rocks to generate electricity, uses the Earth's high-temperature magma layers as a heat source and is a means of generating electricity without consuming fuel or emitting greenhouse gases during the power generation process. For this reason, geothermal power generation has attracted attention as a renewable energy source from the perspectives of energy self-sufficiency and global warming countermeasures.

[0003] As a related technology for geothermal power generation, Patent Document 1 discloses a flash type geothermal power generation system that generates power by drilling a production well in a geothermal area and utilizing thermal energy contained in geothermal fluids such as high-temperature and high-pressure hot water and steam obtained from a geothermal reservoir. Patent Document 2 discloses a closed-loop type geothermal power generation system that generates power by recovering underground heat by installing a closed-loop circulation flow path consisting of a double pipe with an inner pipe and an outer pipe underground and circulating fluids such as water from above ground. Patent Document 3 discloses a geothermal power generation system that realizes more efficient geothermal power generation by providing production wells for other geothermal power generation facilities around a closed-loop type geothermal well for heat exchange liquid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-037982 A [Patent Document 2] JP 2014-202149 A [Patent Document 3] JP 2016-164395 A Summary of the Invention [Problem to be solved by the invention]

[0005] For geothermal power generation systems, it is desirable to recover more thermal energy from the geothermal zone to increase the amount of power generated.

[0006] The present invention has been made in consideration of the above problems, and has an object to improve the amount of heat recovered from a geothermal zone and thereby increase the amount of power generation. [Means for solving the problem]

[0007] One aspect of the present invention is a geothermal power generation system that generates electricity using thermal energy in a geothermal zone, comprising at least two or more boreholes, a power generation facility that extracts geothermal fluid generated in the geothermal zone from one of the two or more boreholes and generates electricity using the thermal energy contained in the geothermal fluid, and a geothermal heat exchanger that exchanges heat in the geothermal zone with a fluid circulating in a flow path configured in a closed loop, the geothermal heat exchanger being located somewhere between the two or more boreholes.

[0008] According to one embodiment of the present invention, by installing a geothermal heat exchanger having a closed-loop flow path between two or more boreholes, the amount of heat recovered from the geothermal zone can be improved, thereby increasing the amount of power generation.

[0009] Another aspect of the present invention is a geothermal power generation method that generates electricity by utilizing thermal energy in a geothermal zone, in which geothermal fluid produced in the geothermal zone is extracted from one of at least two or more boreholes and electricity is generated by utilizing the thermal energy contained in the geothermal fluid, a geothermal heat exchanger is provided at a point between the two or more boreholes, which exchanges heat in the geothermal zone with a fluid circulating in a flow path configured in a closed loop, and electricity is generated by utilizing the thermal energy contained in the heated fluid obtained by heat exchange in the geothermal heat exchanger.

[0010] According to another aspect of the present invention, by providing a geothermal heat exchanger having a closed-loop flow path between two or more boreholes, the amount of heat recovered by the geothermal heat exchanger from the geothermal zone can be improved, thereby increasing the amount of power generation. Effect of the Invention

[0011] According to the present invention, the amount of heat recovered from the geothermal zone can be improved, thereby increasing the amount of power generation. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a schematic overall configuration of a geothermal power generation system according to a first embodiment of the present invention. [Diagram 2] 1 is an explanatory diagram showing a schematic configuration of a main part of a geothermal power generation system according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is an explanatory diagram showing an example of the arrangement of temperature sensors provided in a geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention. [Figure 4] 1(A) to 1(D) are explanatory diagrams showing examples of the arrangement of geothermal heat exchangers in a geothermal power generation system according to a first embodiment of the present invention. [Diagram 5] FIG. 4 is an explanatory diagram showing another example of the arrangement of the geothermal heat exchanger in the geothermal power generation system according to the first embodiment of the present invention. [Figure 6] FIG. 2 is a flow diagram showing an example of an operational flow of heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention. [Figure 7] FIG. 4 is a flow diagram showing another example of the operational flow of heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a block diagram showing a functional configuration of a modified example of the geothermal power generation system according to the first embodiment of the present invention. [Figure 9] FIG. 4 is an explanatory diagram showing a schematic configuration of a main part of another modified example of the geothermal power generation system according to the first embodiment of the present invention. [Figure 10] 1(A) and 1(B) are explanatory diagrams showing modified examples of a borehole in which a geothermal heat exchanger is installed in the geothermal power generation system according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a block diagram showing a schematic overall configuration of a geothermal power generation system according to a second embodiment of the present invention. [Figure 12]FIG. 4 is an explanatory diagram showing a schematic configuration of a main part of a geothermal power generation system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A preferred embodiment of the present invention will be described in detail below. Note that the embodiment described below does not unduly limit the content of the present invention described in the claims, and all of the configurations described in the embodiment are not necessarily essential as the solution of the present invention.

[0014] In the following description, terms indicating directions such as "upper", "lower", "left" and "right" are used for convenience of description and do not limit the method or manner of use. Terms such as "first" and "nth" (n is an integer) following "first" in this specification and claims are used as identifying terms to distinguish different elements and do not indicate a specific order or superiority or inferiority.

[0015] [First embodiment] The schematic configuration of a geothermal power generation system according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an explanatory diagram showing a schematic configuration of the entire geothermal power generation system according to the first embodiment of the present invention, and Fig. 2 is a block diagram showing a schematic configuration of a main part of the geothermal power generation system according to the first embodiment of the present invention.

[0016] The geothermal power generation system 100 of this embodiment is a geothermal power generation system that generates power by utilizing thermal energy in the geothermal reservoir GR1 in the geothermal zone, and includes a production well 101, a reinjection well 102, a first geothermal power generation facility 110, a second geothermal power generation facility 120, and a geothermal heat exchanger 130, as shown in FIG. 1. The production well 101 is a borehole that extracts geothermal fluids such as high-temperature and high-pressure hot water and steam that are retained in the geothermal reservoir GR1 in the geothermal zone, as shown in FIG. 2. The reinjection well 102 is a borehole that uses the geothermal fluid extracted from the production well 101 for power generation in the first geothermal power generation facility 110, and then returns the reinjection water, which contains the condensed water of the steam that has completed power generation and other water, underground. In other words, the reinjection well 102 is a borehole that returns the reinjection water discharged after heat exchange of the geothermal fluid in the first geothermal power generation facility 110 into the ground.

[0017] The first geothermal power generation facility 110 is a facility for taking in geothermal water containing high-temperature steam of approximately 100 to 400°C as a geothermal fluid and generating electricity from this geothermal water, and mainly comprises a first flasher 111, a second flasher 112, a turbine 113, a generator 114, a condenser 115, a high-pressure circulating pump 116, etc., as shown in Figure 1.

[0018] The first geothermal power generation facility 110 takes in geothermal water heated by geothermal energy, separates it into steam in a first flasher 111, which is a steam-water separator, and sends the separated steam to a turbine 113. In addition, steam and water are optionally separated in a second flasher 112 to obtain secondary steam, which is also sent to the turbine 113, and electricity is generated by the rotation of the turbine 113 in a generator 114. The steam consumed in the turbine 113 is condensed in a condenser 115, and the condensed geothermal water is cooled and discharged or cooled and used as cooling water for the condenser 115, or is used for injection into the geothermal zone by an injection well 102. The hot water obtained by the steam-water separation in the second flasher 112 is sent to the injection well 102 by a high-pressure circulation pump 116.

[0019] The first geothermal power generation facility 110 is not limited to the above-mentioned configuration, and other components may be replaced with other devices, or may be additionally provided. In this embodiment, the first geothermal power generation facility 110 is illustrated as a double flash system as shown in Fig. 1, but it can also be applied to a single flash system in which hot water separated from steam in the first flasher 111 is directly returned from the return well 102 to the geothermal heat field.

[0020] Furthermore, as described above, the geothermal power generation system 100 applies, as the first geothermal power generation facility 110, a geothermal power generation facility of a flash power generation type that generates power by using high-temperature, high-pressure steam contained in the geothermal fluid extracted from the production well 101. The geothermal power generation system 100 of this embodiment is not limited to a geothermal power generation facility of a flash power generation type as the first geothermal power generation facility 110, and can also be applied to a geothermal power generation facility of a binary type that generates power by using steam obtained by boiling a medium with a boiling point lower than that of water using the geothermal fluid extracted from the production well 101.

[0021] The second geothermal power generation facility 120 is a binary type geothermal power generation facility using a closed-loop type geothermal heat exchanger 130 that exchanges heat in a geothermal zone with a fluid circulating in a closed-loop type flow path. That is, unlike the first geothermal power generation facility 110, the second geothermal power generation facility 120 does not need to discharge a heat exchange fluid that receives heat from underground into a geothermal zone or to take in hot water from the geothermal zone. In addition, the heat exchange liquid used in the geothermal heat exchanger 130 is preferably a low-boiling liquid with a boiling point of 150° C. or less at atmospheric pressure, such as water or water with ammonia dissolved therein, but is not limited thereto.

[0022] The geothermal heat exchanger 130 includes an outer pipe 131 buried in the ground facing the geothermal heat zone, and an inner pipe 132 provided inside the outer pipe 131. As shown in FIG. 2, the geothermal heat exchanger 130 has a double-pipe structure in which the space between the outer pipe 131 and the inner pipe 132 is a descending flow passage 131a for descending the heat exchange fluid, and the inside of the inner pipe 132 is an ascending flow passage 132a for ascending the heat exchange fluid, and has no opening in the geothermal heat zone. The inner pipe 132 is formed with its lowest end open below the outer pipe 131, and at its lowest end, the ascending flow passage 132a in the inner region inside the inner pipe 132 and the descending flow passage 131a in the outer region between the inner pipe 132 and the outer pipe 131 are formed to communicate with each other. Therefore, the heat exchange fluid descending the descending flow passage 131a in the outer region can be moved to the ascending flow passage 132a in the inner region and ascended.

[0023] The geothermal heat exchanger 130 has the double pipe structure described above, thereby forming a closed loop type flow path, in which a fluid serving as a heat exchange medium is pressed into the descending flow path 131a between the outer pipe and the inner pipe, and the fluid is heated in the geothermal heat zone while descending through the descending flow path 131a, and the resulting heated fluid is transported while ascending through the ascending flow path 132a inside the inner pipe 132. In other words, the geothermal heat exchanger 130 has the function of transporting the heat exchange fluid to the geothermal heat zone, and transporting the heat exchange fluid that has been heat exchanged and heated in the geothermal heat zone to the ground as a heated fluid.

[0024] As shown in FIG. 3, the geothermal heat exchanger 130 is provided with a temperature sensor 133 (133) capable of measuring the underground temperature on at least one of the outer surface side of the outer pipe 131 and the outer surface side of the inner pipe 132. in , 133 out ) can be provided. To operate the geothermal heat exchanger 130, a technique for monitoring the recovery of the layer temperature in real time is required, and in a geothermal field, the temperature of the layer becomes as high as 250 to 300°C or more. For this reason, in this embodiment, it is preferable to use a fiber sensor that can withstand high temperatures as the temperature sensor 133 attached to the geothermal heat exchanger 130.

[0025] A temperature sensor 133 is attached to the outer circumferential surface of an outer tube 131 of the geothermal heat exchanger 130. outBy installing the temperature sensor 133 permanently, it becomes possible to measure the temperature change during and after the circulation of the heat exchange fluid in real time. in When monitoring the formation temperature by installing a temperature sensor 133 on the outer periphery of the inner pipe 132, it is preferable to construct the outer pipe 131 from a material with high thermal conductivity such as copper, since this makes it possible to monitor the formation temperature even if it is not on the back side of the outer pipe 131. Details of the operation control of the geothermal heat exchanger 130 based on the measurement results of the temperature sensor 133 of the geothermal heat exchanger 130 will be described later.

[0026] In this embodiment, a double-pipe structure is used as the closed-loop geothermal heat exchanger 130, but other configurations may be used as long as the heat exchange fluid is circulated in a closed-loop flow path formed underground and heat can be exchanged in the geothermal heat zone. For example, a closed-loop geothermal heat exchanger may be a system in which a mesh-like loop is excavated connecting the ground and the ground about several thousand meters underground, and water is circulated in the loop to extract underground heat through the water.

[0027] As shown in Figures 1 and 2, the second geothermal power generation facility 120 includes an evaporator 121, a tank 122, a turbine 123, a generator 124, a condenser 125, a high-pressure circulation pump 126, and the like. In the second geothermal power generation facility 120 having these devices, a heat exchange medium circulating in a geothermal heat exchanger 130 is heated by geothermal heat to generate a heat exchange medium, which is then heated and evaporated by heat exchange in the evaporator 121, which functions as a steam generator. The heat exchange medium heated and evaporated by heat exchange in the evaporator 121 is then sent to a turbine 123, and electricity is generated by the generator 124 as the turbine 123 rotates.

[0028] The steam consumed by the turbine 123 is condensed in the condenser 125, and the condensed heat exchange medium is used as cooling drainage or cooled to be used as the cooling water of the condenser 125. In addition, it is returned to the evaporator 121 and used to generate high-temperature and high-pressure steam by depressurized boiling in the evaporator 121. The heat exchange medium after being used for heat exchange in the evaporator 121 is once stored in the tank 122 and then sent to the geothermal heat exchanger 130 by the high-pressure circulation pump 126. Note that the second geothermal power generation facility 120 is not limited to the above-described configuration, and other constituent devices may be replaced with other devices or additionally provided.

[0029] In the geothermal power generation system 100 of the present embodiment, the geothermal heat exchanger 130 is provided at any point between the production well 101 and the reinjection well 102. Specifically, as shown in FIG. 4(A), the geothermal heat exchanger 130 is provided on the straight line L1 connecting the production well 101 and the reinjection well 102. The installation location of the geothermal heat exchanger 130 is not limited to the installation on the straight line L1 connecting the production well 101 and the reinjection well 102, and as shown in FIG. 4(B), it may be provided in the vicinity of the straight line L1 connecting the production well 101 and the reinjection well 102. For example, when the distance between the production well 101 and the reinjection well 102 is D (= the length of the straight line L1) and the shortest distance between the straight line L1 and the geothermal heat exchanger 130 (the length of the perpendicular line dropped from the geothermal heat exchanger 130 to the straight line L1) is d, it is preferable that d < D. Note that d may be the length of the perpendicular line dropped from the center of the geothermal heat exchanger 130 to the straight line L1.

[0030] In addition, the number of the geothermal heat exchangers 130 installed on the straight line L1 connecting the production well 101 and the reinjection well 102 is not limited to one, and may be two or more. For example, as shown in FIG. 4(C), two geothermal heat exchangers 130 may be provided on the straight line L1 connecting the production well 101 and the reinjection well 102. The geothermal heat exchangers 130 may be provided in two in the vicinity of the straight line L1 connecting the production well 101 and the reinjection well 102 as shown in FIG. 4(D).

[0031] Here, the two geothermal heat exchangers 130 are arranged symmetrically with respect to the straight line L1 (line symmetry). When providing two geothermal heat exchangers 130 in this manner, the arrangement may be as described above, for example, with one geothermal heat exchanger 130 provided within a radius r1 from the center of the production well 101, and the other geothermal heat exchanger 130 provided within a radius r2 from the center of the reinjection well 102 (see FIG. 4(D)). Note that the geothermal heat exchangers 130 must be arranged in an area inside two perpendicular lines drawn through the centers of the production well 101 and the reinjection well 102 with respect to the straight line L1.

[0032] Next, referring to FIG. 5, an example of the arrangement of the geothermal exchanger 130 in a place where a plurality of production wells 101a-101d and a plurality of reinjection wells 102a-102d exist in one area will be described. The production wells 101a-101d and the reinjection wells 102a-102d are paired. Between each pair, geothermal exchangers 130a-130e are arranged. Between the production well 101a and the reinjection well 102a, the geothermal exchanger 130a is arranged. In addition, between the production well 101b and the reinjection well 102b, two geothermal exchangers 130b and 130c are arranged. Similarly, between the production well 101c and the reinjection well 102c, the geothermal exchanger 130d is arranged, and between the production well 101d and the reinjection well 102d, the geothermal exchanger 130e is arranged.

[0033] Here, the geothermal exchanger 130d is a geothermal exchanger disposed between the production well 101c and the reinjection well 102c, but can also be seen as disposed between the production well 101d and the reinjection well 102d. In this way, for example, one geothermal exchanger 130d may be shared by a plurality of production wells 101c, 101d and the reinjection wells 102c, 102d. The number of shared geothermal exchangers is not limited to one, and may be multiple. That is, for example, two geothermal exchangers 130d, 130e may be shared by a plurality of production wells 101c, 101d and the reinjection wells 102c, 102d. Also, FIG. 5 shows an example in which the production wells 101a-101d and the reinjection wells 102a-102d are paired with each other. However, for example, there are cases where one reinjection well is provided for multiple production wells, so this is not limited to embodiments in which production wells and reinjection wells are necessarily paired, and can also be applied to embodiments in which the number of production wells and reinjection wells differ.

[0034] In particular, in the geothermal power generation system 100 of this embodiment, the geothermal heat exchanger 130 is applied when installed at any point between the production well 101 and the reinjection well 102 of an existing first geothermal power generation facility 110 (hereinafter also referred to as the existing geothermal power generation facility 110). In the existing geothermal power generation facility 110, a geological survey of the strata at the installation site is conducted in advance when the geothermal power generation facility is constructed, and the geothermal reservoir GR1 in the geothermal zone is monitored even during operation of the geothermal power generation facility, and thus, strata data around the existing geothermal power generation facility 110 is accumulated. For this reason, in this embodiment, the geothermal heat exchanger 130 is installed at any point between the production well 101 and the reinjection well 102 based on the accumulated analysis results of the strata data around the existing geothermal power generation facility 110.

[0035] Next, the operation flow of the heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention will be described with reference to the drawings. Fig. 6 is a flow diagram showing an example of the operation flow of the heat exchange in the geothermal heat exchanger of the geothermal power generation system according to the first embodiment of the present invention.

[0036] When the geothermal heat exchanger 130 to which the closed loop method is applied is operated, the temperature of the formation near the borehole in which the geothermal heat exchanger 130 is installed drops due to fluid circulation from above ground, and if the formation temperature falls below a predetermined threshold, it may not be possible to sufficiently recover thermal energy. For this reason, as described above, in this embodiment, the geothermal heat exchanger 130 is provided with a temperature sensor 133 (133) capable of measuring the underground temperature on at least one of the outer surface side of the outer pipe 131 or the outer surface side of the inner pipe 132. out , 133 in ) is provided, and the underground temperature is detected by the temperature measured by the temperature sensor 133 (step S1).

[0037] In this embodiment, the temperature of the underground layer near the borehole where the geothermal exchanger 130 is installed is monitored, but the temperature measurement is not limited to underground monitoring. That is, the temperature on the ground may be measured as the layer temperature near the borehole where the geothermal exchanger 130 is installed, and the layer temperature may be monitored based on the measured temperature.

[0038] When the temperature sensor 133 detects that the outlet temperature of the circulating fluid has fallen below a threshold value (e.g., below 200°C) that is the minimum value required for heat recovery in the geothermal exchanger 130 (step S2), heat exchange by the geothermal exchanger 130 is stopped (step S3). To stop heat exchange by the geothermal exchanger 130, for example, the operation of the high-pressure circulation pump 126 is turned off to stop the heat exchange operation by the geothermal exchanger 130. In this way, when the supply of fluid from the tank 122 is stopped and the circulation of the fluid is stopped, the temperature of the formation near the borehole of the geothermal exchanger 130 is reheated by a heat source such as a magma chamber deep in the formation and is restored.

[0039] Thereafter, when the temperature sensor 133 detects that the underground temperature has reached or exceeded a threshold value (e.g., 300°C or higher) that is the minimum value required for the geothermal heat exchanger 130 to resume heat recovery (step S4), the geothermal heat exchanger 130 resumes heat exchange (step S5). To resume heat exchange in the geothermal heat exchanger 130, for example, the high-pressure circulation pump 126 is turned on to resume the heat exchange operation in the geothermal heat exchanger 130. Then, by resetting and repeating steps S1 to S5, the temperature sensor 133 monitors the layer temperature in the vicinity of the well in which the geothermal heat exchanger 130 is installed in real time, and switching control is performed to resume or stop the heat exchange operation in the geothermal heat exchanger 130. When a plurality of geothermal heat exchangers 130 are installed, the heat exchange operation is similarly switched on and off.

[0040] As a countermeasure against the drop in the geothermal layer temperature, as described above, other measures are possible than stopping the circulation of the fluid by the high-pressure circulation pump 126, stopping the heat exchange by the geothermal heat exchanger 130, and waiting for the geothermal layer temperature to recover. For example, as shown in FIG. 7, when the temperature sensor 133 detects that the underground temperature has fallen below a threshold value that is the minimum value required for the geothermal heat exchanger 130 to recover heat (step S10), the temperature sensor 133 may prompt the recovery of the geothermal layer temperature by, for example, injecting hot water (a fluid having a predetermined temperature or higher), such as wastewater from a flash-type geothermal power generation system, into the descending flow passage 131a of the geothermal heat exchanger 130 and circulating it (step S11). In this way, when the temperature measured by the temperature sensor 30 recovers to a desired threshold value or higher (step S12) by injecting and circulating the hot water, the injection of the hot water is stopped and the heat exchange is resumed (step S13).

[0041] As described above, in this embodiment, when controlling the operation of heat exchange by the closed-loop type geothermal heat exchanger 130, the temperature of the formation near the borehole of the geothermal heat exchanger 130 is monitored by the temperature sensor 133 to control the on / off of heat exchange by the geothermal heat exchanger 130. However, if there is only one geothermal heat exchanger 130 installed between the production well 101 and the reinjection well 102, there will be periods when heat recovery is suspended.

[0042] Therefore, in the geothermal power generation system 100 of this embodiment, multiple geothermal heat exchangers 130 may be provided between the production well 101 and the reinjection well 102, and the formation temperature near the well of each heat exchanger 130 may be monitored by a temperature sensor 133, and the heat exchange may be controlled on and off for each geothermal heat exchanger 130.

[0043] Next, a case where the geothermal power generation system 100 of this embodiment has a plurality of geothermal heat exchangers 130 will be described with reference to the drawings. FIG. 8 is a block diagram showing a schematic configuration of a modified example of the geothermal power generation system according to the first embodiment of the present invention. Note that FIG. 8 focuses only on the sensors and control units provided in each heat exchanger in the geothermal power generation system, and describes in detail the functions of each sensor unit in each heat exchanger and the control unit of the geothermal power generation system. FIG. 8 also describes a case where there are three geothermal heat exchangers.

[0044] In the geothermal power generation system 100 of this embodiment, a control unit 140, which serves as a system management computer, is connected to each of the heat exchangers 130a, 130b, and 130c via a network 150. Note that FIG. 8 shows, as an example of the geothermal power generation system 100, a distributed control system (hereinafter also referred to as "DCS") in which the control devices of the devices constituting the system are connected via a network to communicate with and manage each other. In this embodiment, the geothermal power generation system 100 is not limited to a DCS, and other control systems such as a Programmable Logic Controller (PLC) may also be used.

[0045] The control unit 140 incorporates a computer and a microprocessor in a control device called a controller, and is configured to perform process control using the functions of these devices. As shown in FIG. 8, the control unit 140 has a receiving unit 141, a determining unit 142, and a transmitting unit 143.

[0046] The receiving unit 141 has a function of controlling reception of detection data from the sensors 133a, 133b, 133c, 134a, 134b, 134c, 135a, 135b, and 135c of the heat exchangers 130a, 130b, and 130c.

[0047] The determination unit 142 has a function of performing determination operations required when executing various operations of the geothermal power generation system 100. For example, the determination unit 142 has a function of determining whether various data is transmitted to and received from the heat exchangers 130a, 130b, and 130c. In this embodiment, the determination unit 142 has a function of determining whether detection data from the sensors 133a, 133b, 133c, 134a, 134b, 134c, 135a, 135b, and 135c of the heat exchangers 130a, 130b, and 130c reaches a predetermined threshold value, and a function of controlling various operations of the heat exchangers 130a, 130b, and 130c based on the detection data.

[0048] The transmission unit 143 has a function of controlling the transmission of various data to the heat exchangers 130a, 130b, and 130c. The transmission unit 143 has a function of transmitting various operation control commands to the heat exchangers 130a, 130b, and 130c based on the determination result by the determination unit 142.

[0049] Each of the heat exchangers 130a, 130b, and 130c includes a temperature sensor 133a, 133b, and 133c, an acoustic sensor 134a, 134b, and 134c, and a strain sensor 135a, 135b, and 135c. As described above, the temperature sensors 133a, 133b, and 133c have a function of measuring the temperature of the formation near the wells of each of the heat exchangers 130a, 130b, and 130c. The acoustic sensors 134a, 134b, and 134c have a function of measuring and monitoring the behavior of the formation near the wells of each of the heat exchangers 130a, 130b, and 130c, such as friction, collision, and stress waves generated by turbulence and cavitation of geothermal liquid, as well as measuring micro-vibrations. The strain sensors 135a, 135b, 135c function to measure dynamic and quasi-static surface strain changes and strains in the formation adjacent to the wells of the geothermal exchangers 130a, 130b, 130c.

[0050] As each component of the geothermal power generation system 100 has the functional configuration described above, it is able to receive detection data from temperature sensors 133a, 133b, 133c, acoustic sensors 134a, 134b, 134c, and strain sensors 135a, 135b, 135c received from each heat exchanger 130a, 130b, 130c, and to perform various operational controls, including heat exchange, of each heat exchanger 130a, 130b, 130c, based on the detection data.

[0051] In this embodiment, the temperature of the formation near the wells of each heat exchanger 130a, 130b, 130c is monitored by temperature sensors 133a, 133b, 133c, and the heat exchange operation is switched for each of the geothermal heat exchangers 130a, 130b, 130c, so that power can be generated by heat exchange in the geothermal heat exchangers 130a, 130b, 130c in a closed loop system. Therefore, even if the detection data of one of the geothermal heat exchangers 130a falls below a threshold and the heat exchange operation is stopped, if the detection data of the other geothermal heat exchangers 130b, 130c are higher than the threshold, the heat exchange operation is maintained, thereby enabling continuous heat recovery and power generation in the geothermal power generation system 100 as a whole.

[0052] In addition, in this embodiment, by reflecting the data actually acquired from the temperature sensor 133 in the temperature simulation model in the vicinity of the well, it becomes possible to perform a more accurate simulation. Therefore, the behavior of the strata in the vicinity of the well of each heat exchanger 130 can be predicted, and the operation of each heat exchanger 130 can be optimized. For example, by simulating future production and power generation amounts by simulating while monitoring the temperature data acquired by the temperature sensor 133 in real time, it becomes possible to optimize the switching on and off of the circulation of the heat exchange fluid in the multiple geothermal heat exchangers 130 and the production method throughout the field to which the geothermal power generation system 100 is applied.

[0053] Furthermore, in this embodiment, in addition to data acquired on the surface, data is acquired underground and used to evaluate each heat exchanger 130a, 130b, 130c, thereby improving the accuracy of the behavior evaluation of both the geothermal reservoir and the closed-loop well, thereby improving the operational efficiency. In the past, in geothermal development, there were few sensors suitable for high temperatures that could withstand geothermal temperatures, so continuous underground monitoring was not usually performed, but the fiber sensors that make up the temperature sensors 133a, 133b, 133c can be applied to high temperatures.

[0054] Furthermore, the acoustic sensors 134a, 134b, 134c and the strain sensors 135a, 135b, 135c are used to monitor underground conditions as sensors that detect supplementary information such as micro-vibration data of geothermal fluids and strain data of strata in addition to the data detected by the temperature sensors 133a, 133b, 133c. In this way, by applying the temperature sensors 133a, 133b, 133c, the acoustic sensors 134a, 134b, 134c, and the strain sensors 135a, 135b, 135c alone or in combination, it becomes possible to easily grasp underground conditions that cannot be directly seen with the naked eye.

[0055] In this embodiment, high-temperature, high-pressure hot water or steam is used as the heat exchange medium, which is a fluid circulating in the closed-loop flow path of the geothermal heat exchanger 130, but the heat exchange efficiency may be improved by using carbon dioxide gas (CO2 gas), which has excellent fluidity and heat transfer properties and a high thermal conductivity, as the circulating fluid. When CO2 gas is used as the circulating fluid of the geothermal heat exchanger 130, it is basically in a gas phase or supercritical state in the loop of the geothermal heat exchanger 130 due to its characteristics.

[0056] When the circulating fluid used in the geothermal heat exchanger 130 is liquid, its heat must be exchanged with another substance such as a low boiling point fluid to evaporate it before it is sent to the turbine. However, when CO2 gas is used as the circulating fluid in the geothermal heat exchanger 130, it is basically in a gas phase or supercritical state in the loop of the geothermal heat exchanger 130. Therefore, the circulating fluid that serves as the heat exchange medium in the geothermal heat exchanger 130 can be sent directly to the turbine 123 as shown in Figure 9, eliminating the need to pass it through the evaporator 121, and improving energy efficiency is expected.

[0057] The shape of the well in which the geothermal exchanger 130 is provided is not limited to a straight line extending in the vertical direction. For example, as shown in FIG. 10(A), the shape of the well 103' of the geothermal exchanger 130' may be an L-shaped horizontal well. As shown in FIG. 10(B), the shape of the well 103'' of the geothermal exchanger 130'' may be an inclined well that is vertical from the ground to partway and then becomes oblique from partway. In this way, by applying the method to a horizontal well or an inclined well, the surface area of ​​the loop in contact with the high-temperature stratum can be increased, and more thermal energy can be recovered.

[0058] Next, the operation and effects of the geothermal power generation system according to this embodiment will be described.

[0059] The present inventors have conducted extensive research to solve the problem of recovering thermal energy from geothermal fields more efficiently and increasing power generation efficiency, and have discovered the following phenomenon: In other words, the present inventors have discovered that in a geothermal power generation system that generates power by utilizing thermal energy contained in geothermal fluid collected from a production well and retained in a geothermal reservoir, hot water returned underground from a reinjection well is heated by an underground heat source such as a magma chamber as it moves, and therefore, by providing a closed-loop type geothermal heat exchanger between the reinjection well and the production well, the geothermal heat exchanger can continuously recover heat.

[0060] That is, by installing a closed-loop geothermal heat exchanger between the production well and the reinjection well of a flash or binary geothermal power generation facility that extracts geothermal fluid trapped in a geothermal reservoir from a production well and generates electricity using the high-temperature, high-pressure steam contained in the geothermal fluid, the strata near the well of the geothermal heat exchanger are continuously heated by the heat flow accompanying the movement of hot water returned from the reinjection well. Therefore, since the well of the closed-loop geothermal heat exchanger is located at the destination of the fluid injected from the reinjection well, which absorbs heat and moves, heat convection is promoted in the vicinity of the well to which the closed-loop method is applied as the fluid injected from the reinjection well moves while being heated, and heat can be continuously recovered. As a result, an increase in the amount of power generation can be expected as the amount of heat recovered by the closed-loop geothermal heat exchanger is improved.

[0061] In addition, in this embodiment, by utilizing existing geothermal power generation equipment, it is possible to improve the heat recovery amount of the closed-loop geothermal exchanger and thereby increase the amount of power generation, making it possible to increase the amount of power generation of the closed-loop geothermal exchanger at relatively low cost.

[0062] Furthermore, in this embodiment, a temperature sensor capable of measuring underground temperature is provided in the geothermal heat exchanger, so that temperature changes in the strata near the well of the geothermal heat exchanger can be monitored. Therefore, the on / off control of the heat exchange operation of the geothermal heat exchanger can be easily performed based on the detection result of the temperature sensor. In particular, by providing multiple geothermal heat exchangers between two wells and controlling the operation of each separately, it becomes possible to continuously exchange heat by the geothermal heat exchangers in a closed loop system throughout the entire geothermal power generation system, and generate power accordingly.

[0063] [Second embodiment] The schematic configuration of a geothermal power generation system according to another embodiment of the present invention will be described with reference to the drawings. Fig. 11 is an explanatory diagram showing the schematic configuration of the entire geothermal power generation system according to a second embodiment of the present invention, and Fig. 12 is a block diagram showing the schematic configuration of the lower part of the geothermal power generation system according to the second embodiment of the present invention.

[0064] The geothermal power generation system 200 of this embodiment is a geothermal power generation system applied to an EGS (Enhanced Geothermal System) type geothermal power generation facility that generates power by utilizing thermal energy contained in a hot dry rock mass HR1 in a geothermal zone, a high-temperature layer, etc. In other words, the geothermal power generation system 200 is a system configured by combining a geothermal power generation facility using a closed-loop type geothermal heat exchanger 230 with an EGS type geothermal power generation facility.

[0065] As shown in Fig. 11, the geothermal power generation system 200 includes a production well 201, an injection well 202, a first geothermal power generation facility 210, a second geothermal power generation facility 220, and a geothermal heat exchanger 230. As shown in Fig. 12, the injection well 202 is a borehole for injecting a fluid into a hot dry rock mass HR1 or a high-temperature stratum located underground in a geothermal zone. The production well 201 is a borehole for extracting geothermal fluid generated by heating the fluid injected from the injection well 202 with thermal energy in the hot dry rock mass HR1 or the high-temperature stratum.

[0066] The first geothermal power generation facility 210 is a facility that generates power by utilizing thermal energy contained in geothermal fluid generated by heating fluid injected from an injection well 202 with thermal energy in a hot dry rock mass HR1 extracted from a production well 201 or in a high-temperature stratum. As shown in Fig. 11, the first geothermal power generation facility 210 mainly includes a first flasher 211, a second flasher 212, a turbine 213, a generator 214, a condenser 215, a high-pressure circulation pump 216, and the like. In the first geothermal power generation facility 210, a geothermal reservoir is artificially created or expanded in the hot dry rock mass HR1 or the like by hydraulic fracturing, and heat is recovered from the artificial reservoir. For this reason, a fluid such as water is injected into an artificial reservoir through an injection well 202, the fluid heated in the artificial reservoir is recovered from a production well 201 as geothermal fluid, and the thermal energy contained in the artificial geothermal fluid is used to generate electricity. After that, the used geothermal fluid is injected underground through the injection well 202, and the heat from the bedrock is extracted through the circulation of water.

[0067] The first geothermal power generation facility 210 takes in geothermal water heated by artificial means, separates the water and steam in a first flasher 211, which is a steam-water separator, and sends the separated steam to a turbine 213. In addition, the water and steam are optionally separated in a second flasher 212 to obtain secondary steam, which is similarly sent to the turbine 213, and electricity is generated in a generator 214 by the rotation of the turbine 213. The steam consumed in the turbine 213 is condensed in a condenser 215, and the condensed artificial geothermal water is cooled and discharged or cooled and used as cooling water for the condenser 215, or is used for injection into a geothermal zone by an injection well 202. The hot water obtained by separating the water and steam in the second flasher 212 is sent to the injection well 202 by a high-pressure circulation pump 216.

[0068] The first geothermal power generation facility 210 is not limited to the above-mentioned configuration, and other components may be replaced with other devices, or may be additionally provided. In this embodiment, the first geothermal power generation facility 210 is illustrated as a double flash system as shown in Fig. 1, but the facility can also be applied to a single flash system in which hot water separated from steam by the first flasher 211 is directly injected from the injection well 202 into the geothermal zone.

[0069] Furthermore, as described above, the geothermal power generation system 200 applies, as the first geothermal power generation facility 210, a geothermal power generation facility of a flash power generation type that generates power by using high-temperature, high-pressure steam contained in the artificial geothermal fluid collected from the production well 201. The geothermal power generation system 200 of this embodiment is not limited to a geothermal power generation facility of a flash power generation type as the first geothermal power generation facility 210, and can also be applied to a geothermal power generation facility of a binary type that generates power by using steam obtained by boiling a medium having a boiling point lower than that of water using the artificial geothermal fluid collected from the production well 201.

[0070] The second geothermal power generation facility 220 is a binary type geothermal power generation facility using a closed-loop type geothermal heat exchanger 230 that exchanges heat in a geothermal zone with a fluid circulating in a closed-loop type flow path. That is, unlike the first geothermal power generation facility 210, the second geothermal power generation facility 220 does not need to discharge a heat exchange fluid that receives heat from the earth into a geothermal zone or to take in hot water from the geothermal zone. In addition, the heat exchange fluid used in the geothermal heat exchanger 230 is preferably a low-boiling point liquid with a boiling point of 150° C. or less at atmospheric pressure, such as water or water with ammonia dissolved therein, but is not limited thereto.

[0071] The geothermal heat exchanger 230 includes an outer pipe 231 buried in the ground facing the geothermal heat field, and an inner pipe 232 provided inside the outer pipe 231. The geothermal heat exchanger 230 of this embodiment is the same as the geothermal heat exchanger 130 of the first embodiment in terms of configuration and operation, so detailed description thereof will be omitted. In this embodiment, a double-pipe structure is applied as the closed-loop geothermal heat exchanger 230, but other configurations may be used as long as the heat exchange fluid is circulated in a closed-loop flow path formed underground and heat exchange is possible in the geothermal heat field. For example, the closed-loop geothermal heat exchanger may be a type in which a mesh-like loop connecting the ground and the underground about several thousand meters is excavated, and water is circulated in the loop to extract underground heat through the water.

[0072] 11 and 12, the second geothermal power generation facility 220 includes an evaporator 221, a tank 222, a turbine 223, a generator 224, a condenser 225, and a high-pressure circulation pump 226. Note that the second geothermal power generation facility 220 of this embodiment is identical in configuration and operation to the second geothermal power generation facility 120 of the first embodiment, and therefore detailed description thereof will be omitted.

[0073] In the geothermal power generation system 200 of this embodiment, the geothermal heat exchanger 230 is provided at a point between the production well 201 and the injection well 202. That is, in the EGS type geothermal power generation facility 210, a fluid such as water is injected from the injection well 202 into an artificial reservoir, and the geothermal fluid heated in the artificial reservoir is recovered from the production well 201, thereby recovering thermal energy. In the artificial reservoir, the injected fluid gradually moves through the stratum, so that a borehole for the closed-loop type geothermal heat exchanger 230 is provided at the destination of the heated geothermal fluid.

[0074] As described above, in the geothermal power generation system 200 of this embodiment, the geothermal exchanger 230 is applied when installed at any point between the production well 201 and the injection well 202 of the existing first geothermal power generation facility 210 (hereinafter also referred to as the existing geothermal power generation facility 210). In the existing geothermal power generation facility 210, a geological survey of the strata at the installation site is conducted in advance when the geothermal power generation facility is constructed, and the geothermal reservoir GR1 in the geothermal zone is monitored even during operation of the geothermal power generation facility, and thus, strata data around the existing EGS type geothermal power generation facility 210 is accumulated. For this reason, in this embodiment, the geothermal exchanger 230 is installed at any point between the production well 201 and the injection well, based on the analysis results of the strata data around the existing geothermal power generation facility 210.

[0075] Next, the operation and effects of the geothermal power generation system according to this embodiment will be described.

[0076] The present inventors have conducted extensive research to solve the problem of recovering thermal energy from geothermal fields more efficiently and increasing power generation efficiency, and have discovered the following phenomenon: In other words, the present inventors have discovered that in EGS-type geothermal power generation facilities, since fluid injected underground from an injection well moves while being heated by an underground heat source such as a magma chamber, by providing a closed-loop geothermal heat exchanger between the injection well and the production well, the geothermal heat exchanger can continuously recover heat.

[0077] That is, by installing a closed-loop geothermal heat exchanger between the production well and the injection well of an EGS-type geothermal power generation facility, which extracts geothermal fluid generated in an artificially created geothermal reservoir in a hot rock mass in a geothermal field from a production well and generates electricity using the high-temperature, high-pressure steam contained in the geothermal fluid, the strata near the well of the geothermal heat exchanger are continuously heated by the heat flow accompanying the movement of hot water returned from the injection well. Therefore, since the well of the closed-loop geothermal heat exchanger is located at the destination of the fluid injected from the injection well, absorbing heat and moving, heat convection is promoted in the vicinity of the well to which the closed-loop method is applied as the fluid injected from the injection well moves while being heated, and heat can be continuously recovered. As a result, an increase in power generation can be expected as the heat recovery amount of the closed-loop geothermal heat exchanger is improved.

[0078] In addition, in this embodiment, by utilizing existing EGS type geothermal power generation equipment, it is possible to improve the heat recovery amount of the closed-loop type geothermal heat exchanger and increase the amount of power generation accordingly. Therefore, it is possible to increase the amount of power generation of the closed-loop type geothermal heat exchanger at a relatively low cost.

[0079] Furthermore, in this embodiment, a temperature sensor capable of measuring the underground temperature may be provided in the geothermal heat exchanger, so that temperature changes in the strata near the well of the geothermal heat exchanger can be monitored. In this case, the on / off control of the heat exchange operation of the geothermal heat exchanger can be easily performed based on the detection result of the temperature sensor. In particular, by providing multiple geothermal heat exchangers between two wells and controlling the operation of each separately, it becomes possible to continuously exchange heat by the geothermal heat exchangers in a closed loop system throughout the entire geothermal power generation system, and generate power accordingly.

[0080] Although each embodiment of the present invention has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0081] For example, a term described at least once in the specification or drawings together with a different term having a broader or similar meaning may be replaced with the different term anywhere in the specification or drawings. In addition, the configuration and operation of the geothermal power generation system are not limited to those described in the respective embodiments of the present invention, and various modifications are possible. [Explanation of symbols]

[0082] 100, 200 Geothermal power generation system 110, 210 Power generating equipment (first power generating equipment) 111, 211 First Flasher 112, 212 2nd Flasher 113, 213 Turbine 114, 214 Generator 115, 215 Condenser 116, 216 High pressure circulation pump 120, 220 Power generation facility (second power generation facility) 121, 221 Evaporator 122,222 Tank 123, 223 Turbine 124, 224 Generator 125, 225 Condenser 126, 226 High pressure circulation pump 130, 230 geothermal exchanger 131, 231 outer tube 131a Downstream 132, 232 inner tube 132a Ascending channel 133, 133a, 133b, 133c, 133 in , 133 out Temperature Sensor 134a, 134b, 134c Acoustic sensors 135a, 135b, 135c Strain sensors 140 Control section 141 Receiving unit 142 Judgment section 143 Transmitter GR1 Geothermal Reservoir HR1 High temperature rock body

Claims

1. A geothermal power generation system that generates electricity by utilizing thermal energy in a geothermal zone, At least two wells; a power generation facility that extracts geothermal fluid generated in the geothermal zone from any one of the two or more wells and generates power by utilizing the thermal energy contained in the geothermal fluid; A geothermal heat exchanger that exchanges heat with a fluid circulating in a closed loop-type flow path in the geothermal zone; Equipped with A geothermal power generation system, wherein the geothermal heat exchanger is provided at a point somewhere between the two or more wells.

2. 2. The geothermal power generation system of claim 1, wherein the geothermal heat exchanger has a closed-loop flow path with a double-pipe structure consisting of an outer pipe buried in the ground toward the geothermal zone and an inner pipe installed inside the outer pipe, and wherein a fluid is pressurized between the outer pipe and the inner pipe, and the heated fluid obtained by heating the fluid in the geothermal zone is transported while rising up the inner pipe.

3. 3. The geothermal power generation system according to claim 2, wherein the geothermal heat exchanger is provided with a temperature sensor capable of measuring the underground temperature on at least one of the outer surface side of the outer pipe and the outer surface side of the inner pipe.

4. The geothermal power generation system of claim 3, wherein the geothermal heat exchanger is controlled to stop heat exchange operation when the temperature measured by the temperature sensor is below a predetermined threshold, and to resume heat exchange operation when the temperature measured by the temperature sensor recovers to above another predetermined threshold.

5. The geothermal power generation system of claim 4, wherein the geothermal heat exchangers are provided at any point between the two or more boreholes, and each of the multiple geothermal heat exchangers has its heat exchange operation switched on and off based on the measured temperature of the temperature sensor.

6. The geothermal power generation system of claim 3, wherein the geothermal heat exchanger further comprises at least one of an acoustic sensor or a strain sensor, and the heat exchange operation of the geothermal heat exchanger is controlled based on detection data from any of the temperature sensor, the acoustic sensor, and the strain sensor.

7. The geothermal power generation system according to claim 3 , wherein the geothermal heat exchanger circulates the fluid having a predetermined temperature or higher through the flow path when the temperature measured by the temperature sensor is equal to or lower than a predetermined threshold value.

8. The geothermal power generation system according to claim 1 , wherein the geothermal heat exchanger uses carbon dioxide gas as the fluid circulated within the flow path.

9. The geothermal power generation system according to claim 1 , wherein the well in which the geothermal heat exchanger is installed includes either a deviated well or a horizontal well.

10. The power generation facility includes: a first geothermal power generation facility that generates power by utilizing the thermal energy contained in the geothermal fluid extracted from any of the two or more wells; The geothermal power generation system according to claim 2 , further comprising: a second geothermal power generation facility that generates power by utilizing the thermal energy contained in the heating fluid transferred from the geothermal heat exchanger.

11. The two or more wells include a production well that extracts the geothermal fluid from a geothermal reservoir formed underground in the geothermal zone, and a reinjection well that returns reinjection water discharged after the geothermal fluid exchanges heat in the power generation facility to the ground, 11. A geothermal power generation system according to any one of claims 1 to 10, wherein the power generation facility generates power by utilizing the thermal energy contained in the geothermal fluid collected from the production well and retained in the geothermal reservoir.

12. The two or more wells include an injection well for injecting a fluid into a hot rock mass or a high-temperature stratum in the ground of the geothermal zone, and a production well for extracting the geothermal fluid produced by heating the fluid with the thermal energy in the hot rock mass or the high-temperature stratum, A geothermal power generation system as described in any one of claims 2 to 10, wherein the power generation equipment generates power by utilizing the thermal energy contained in the geothermal fluid produced by heating the fluid with the thermal energy in the hot rock mass or high-temperature stratum extracted from the production well.

13. A geothermal power generation method for generating electricity by utilizing thermal energy in a geothermal zone, comprising: A geothermal power generation method in which geothermal fluid generated in the geothermal zone is extracted from one of at least two or more boreholes and power is generated using the thermal energy contained in the geothermal fluid, the method comprising: providing a geothermal heat exchanger at a point between the two or more boreholes in a power generation facility, which exchanges heat in the geothermal zone with fluid circulating in a flow path configured in a closed loop type, and generating power using the thermal energy contained in the heated fluid obtained by heat exchange in the geothermal heat exchanger.

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