Embedded pipe

Abstract

To provide a heat medium transfer pipe which enables improvement of the ability for keeping the heat medium transfer pipe for transferring a medium warm to utilize heat obtained from a geothermal field with the medium on the ground in a more effective manner, and to provide a geothermal power generation system and a geothermal power generation method which use the heat medium transfer pipe.SOLUTION: A heat medium transfer pipe 10 (a medium injection pipe 50 and a heat medium takeout pipe 80) transports a medium (for example, mainly water, oil etc.) into the ground and recovers the medium which absorbs heat in the ground. The heat medium transfer pipe includes: pipe joints 51, 55 which connect the heat medium transfer pipes provided as multiple units; and heat medium heat retention pipes 60, 90 which are located in the heat medium transfer pipe and continuously cover the pipe joints and part of the heat medium transfer pipe to retain heat in the medium.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a heat medium transfer pipe that recovers heat using a medium from a geothermal heat source and has an improved ability to retain heat when transferring the heat medium, and a geothermal power generation device and buried pipe that generate electricity using the heat medium transfer pipe. [Background technology]

[0002] Conventionally, geothermal power generation systems have used a method in which natural steam that exists in geothermal heat zones is extracted using natural pressure, and the steam is then separated into water and steam for use, so the extracted steam contains a large amount of sulfur and other impurities that are unique to geothermal heat zones. These impurities turn into scale and adhere to thermal wells, piping, turbine blades, etc. When scale builds up, the amount of electricity generated decreases over time, making long-term use difficult.

[0003] Patent Document 1 proposes a geothermal power generation system in which a closed loop circulation flow path is configured in a binary power generation system in which a heat source fluid absorbs heat through heat exchange with geothermal fluid or geothermal heat, releases heat in an evaporator, and returns to be exchanged with geothermal fluid or geothermal heat again, and also in which a closed loop flow path is configured for a cooling fluid that cools a low boiling point medium by releasing heat into the ground for cooling, or which is equipped with a refrigerator and heat exchanger that uses the heat source fluid after passing through the evaporator as a driving heat source, and in which a closed loop flow path is configured in which the temperature of the cooling fluid is controlled and the cooling fluid is supplied to the condenser so that condensation and liquefaction of the low boiling point medium in the condenser can be optimized.

[0004] Patent Document 2 discloses a general pipe threaded joint used in a heat transfer medium transfer pipe that efficiently recovers a heat transfer medium, and describes a pipe threaded joint which is composed of a pin and a box, each of which has a contact surface having a threaded portion and an unthreaded metal contact portion, the unthreaded metal contact portion having a seal surface and a shoulder surface, the shoulder surface of the pin is located at the end face of the tip of the pin, there is a non-contact area between the seal surface and the shoulder surface where the pin and box do not come into contact with each other, and the shoulder surface of at least one of the pin and box has at least one groove which leads to the non-contact area and the interior of the threaded joint. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-84857 A [Patent Document 2] Special Publication No. 2014-517925 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] As mentioned above, in the power generation method that uses pumped hot spring water, the amount of power generation decreases over time due to the buildup of scale on the geothermal well, production well, piping equipment, turbines, and other equipment. In addition, regular maintenance is required to remove the scale. From an environmental perspective, the hot spring water is pumped up for use, which may affect the discharge rate of the hot spring water. In addition, after the hot spring water is pumped up and used for power generation, it is returned to the earth through the reinjection well, but this contains chemicals used to remove the scale, which has a significant impact on the environment. In addition, the method of generating electricity using only underground heat, as described in Patent Document 1, is effective because it is environmentally friendly and there is no need to consider concerns about the amount of hot spring water or chemicals.

[0007] Furthermore, a heat medium transfer pipe is required to recover heat underground and transfer the resulting hot water to the surface, and the length of the heat medium transfer pipe is required to be 1000 to 3000 m depending on the temperature of the geothermal field, and the heat medium transfer pipe is connected to the pipes by a pipe thread joint and extends deep underground. As shown in Patent Document 2, the pipe thread joint is required to have high compression resistance and sealing performance under internal and external pressure, and is firmly connected to the pipe.

[0008] However, pipe thread joints are not designed to improve heat retention, and there is a problem that heat transfer occurs inside and outside the pipe near the surface where the temperature is low, and the heat collected from the ground is lost. In addition, not only pipe thread joints but also transfer pipes that require heat retention become more difficult to maintain as their diameter increases, making it technically difficult to achieve a balance between strength and heat retention. There is also a demand for technology that improves the ease of installation without impairing the thermal insulation performance of a thermal insulation structure. Therefore, in order to effectively utilize the heat transfer medium obtained from underground, a technology has become necessary to transport the heat transfer medium to a separator or heat exchanger on the ground without losing heat during transport, while also taking into account operational performance.

[0009] The present invention has been made in consideration of the above problems, and aims to provide a geothermal power generation system that prevents the intrusion of water with a lower temperature than the heat medium transfer pipe from below, improves the insulation performance of the heat medium transfer pipe, and effectively recovers heat in the heat recovery area, in order to effectively utilize the heat obtained from the geothermal zone by using a medium on the ground while improving operability. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention employs the following means.

[0011] A heat medium transport pipe that transports a medium underground and recovers the medium that has absorbed heat underground. A geothermal power generation device in which In the low temperature regions of the geothermal zone A plurality of protective tubes are provided around the heat medium transfer tube, In the high temperature regions of the geothermal zone Around the heat medium transfer pipe, A receiving tube with multiple holes on the side and an open bottom The present invention is characterized in that it is provided.

[0012] With the above features, the sealing layer prevents water with a lower temperature than the heat transfer pipe from entering from below, improving the insulation performance of the heat transfer pipe. Also, when the geothermal zone is covered with a fluid medium such as hot water, the sealing layer allows the medium such as hot water to move through the holes. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a geothermal power generation system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing a part of the heat medium transfer pipe according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a perspective view showing a part of an exploded medium injection pipe according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a longitudinal sectional view of a portion of the medium injection pipe of the present invention according to the first embodiment. [Diagram 5] FIG. 5 is a perspective view of a portion of the heat-insulating pipe of the present invention according to the first embodiment. [Figure 6] FIG. 6 is a longitudinal sectional view of a portion of the medium injection pipe of the present invention according to the first embodiment. [Figure 7] FIG. 7 is a vertical cross-sectional view of a portion of the heat medium transport pipe according to the first embodiment of the present invention. [Figure 8] FIG. 8 is a vertical sectional view of a portion of the heat medium extraction pipe according to the first embodiment of the present invention. [Figure 9] FIG. 9 is a schematic diagram showing changes in the state of water according to the first embodiment of the present invention. [Figure 10] FIG. 10 is a relationship diagram showing the relationship between the depth of the heat medium transfer pipe and the temperature distribution of the hot water in the geothermal power generation system according to the first embodiment of the present invention. [Figure 11] FIG. 11 is an explanatory diagram relating to experimental data showing the heat retention performance of the present invention according to the first embodiment. [Figure 12] FIG. 12 is a schematic diagram showing the configuration of a geothermal power generation system according to the second embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram showing the configuration of a geothermal power generation system according to the third embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram showing the configuration of a geothermal power generation system according to the fourth embodiment of the present invention. [Figure 15]FIG. 15 is a vertical cross-sectional view of a heat medium transport pipe according to a fifth embodiment of the present invention, with a part thereof omitted. [Figure 16] FIG. 16 is a vertical cross-sectional view of a heat medium transport pipe according to a fifth embodiment of the present invention during installation. [Figure 17] FIG. 17 is a vertical cross-sectional view of a heat medium transport pipe according to a fifth embodiment of the present invention during installation. [Figure 18] FIG. 18 is a schematic view showing an enlarged view of a pipe thread joint of a heat medium transport pipe according to a fifth embodiment of the present invention. [Figure 19] FIG. 19 is a vertical cross-sectional view of a heat medium transport pipe according to a modified example of the fifth embodiment of the present invention, with a part thereof omitted. [Figure 20] FIG. 20 is a relationship diagram showing the relationship between the depth of the heat medium transfer pipe and the temperature distribution of the hot water in the geothermal power generation system according to the fifth embodiment of the present invention. [Figure 21] FIG. 21 is a schematic diagram showing the configuration of a geothermal power generation system according to the sixth embodiment of the present invention. [Figure 22] FIG. 22 is a schematic diagram showing the configuration of a heat medium transfer pipe according to the sixth embodiment of the present invention. [Figure 23] FIG. 23 is a vertical sectional view showing a modified example of the heat medium extraction pipe according to the first embodiment. [Figure 24] FIG. 24 is a schematic diagram showing a modified example of the receiving pipe according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The geothermal power generation systems 1, 100, 200, 300, and 400 according to the present invention will be described in detail with reference to the drawings. Note that the embodiments and drawings described below are intended to exemplify some of the embodiments of the present invention, and are not intended to limit the present invention to these configurations. The present invention may be modified as appropriate without departing from the scope of the present invention. In each drawing, corresponding components are denoted by the same or similar reference numerals.

[0015] (First embodiment) A geothermal power generation system 1 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the configuration of a geothermal power generation system 1 according to the first embodiment of the present invention.

[0016] The geothermal power generation system 1 is mainly composed of a pressurized water supply pump 3, a heat medium transfer pipe 10, a hot water service tank 4, a condensate unit 17, a water supply unit 18, a steam-water separator F, a steam turbine T, a generator G, and a power receiving facility TF. Geothermal power generation system 1 performs heat exchange on water as a medium supplied from pressurized water supply pump 3 to the deepest part of the ground through medium injection pipe 50, and transports the hot water to the ground through heat medium extraction pipe 80 while pressurizing it. The transported hot water L3 is reduced in pressure by pressure regulating valve PV1 and boiled, and then transported to steam-water separator F. Steam and hot water are separated in steam-water separator F, and the generated steam V1 is supplied to steam turbine T.

[0017] The geothermal power generation system 1 supplies the generated steam V1 to a steam turbine T to rotate a generator G to generate electricity, which is then supplied to a power receiving facility TF and then to electric power companies, etc. via the power transmission grid. The steam turbine T may be of not only a turbine type but also a screw type, etc., as long as it is capable of generating electricity using steam. The steam V1 supplied to the steam turbine T is generated by reducing the pressure of hot water L3 and boiling it, and the hot water and steam are separated in a steam separator F.

[0018] Since not all of the hot water L3 supplied to the steam-water separator F is converted into steam V1, a large amount of hot water L4, so-called drain, is sent from the steam turbine T to the hot water service tank 4. In addition, the steam V3 exhausted by the steam turbine T is sent to a condensing unit 17, and the steam V4 sent to the condensing unit 17 is sent to a cooling tower 15 connected to the condenser 6. The sent steam V4 is condensed and returned to water, passes through the condenser 6, and is temporarily stored in the condensate tank 14 before being sent to the hot water service tank 4 by the condensate pump 5.

[0019] Hot water L8 in the hot water service tank 4 is transferred as hot water L1 by the pressurized water supply pump 3 to the heat medium transfer pipe 10. The hot water L1 transferred by the pressurized water supply pump 3 absorbs heat from the geothermal heat again at a depth where the geothermal heat field U is located, and is subjected to heat exchange. The heat-exchanged hot water L2 is transferred by the pressurized water supply pump 3 through the heat medium transfer pipe 10, which will be described later.

[0020] (heat medium transfer pipe) Next, the heat medium transfer pipe 10 will be described with reference to Figs. 2 to 10. Fig. 2 is a perspective view showing a part of the heat medium transfer pipe 10 of the present invention according to the first embodiment. Fig. 3 is a perspective view showing a part of the medium injection pipe 50 of the present invention according to the first embodiment, which is disassembled. Fig. 4 is a longitudinal sectional view of a part of the medium injection pipe 50 of the present invention according to the first embodiment. Fig. 5 is a perspective view of the heat-insulating pipe 60 of the present invention according to the first embodiment. Fig. 6 is a longitudinal sectional view of a part of the medium injection pipe 50 of the present invention according to the first embodiment. Fig. 7 is a longitudinal sectional view of a part of the heat medium transfer pipe 50 of the present invention according to the first embodiment. Fig. 8 is a longitudinal sectional view of a part of the heat medium extraction pipe 80 of the present invention according to the first embodiment. Fig. 9 is a schematic diagram of the state change of water of the present invention according to the first embodiment. Fig. 10 is a relationship diagram showing the relationship between the depth of the heat medium transfer pipe 10 of the geothermal power generation system 1 of the present invention according to the first embodiment and the temperature distribution of hot water.

[0021] As shown in FIG. 10, a heat medium transfer pipe 10 is buried from the surface S to a geothermal heat zone U, which is a heat source located deep underground. A cylindrical medium injection pipe 50 is buried on the outside of the heat medium transfer pipe 10, and the area around the medium injection pipe 50 from the surface S to the area just before the geothermal heat zone U, that is, the area where the temperature is lower than the temperature required for power generation, is solidified with geothermal cement or the like to prevent the risk of collapse. The heat medium transfer pipe 10 absorbs heat from the fluid or rock in the geothermal heat zone U located at the deepest part of the medium injection pipe 50 of the heat medium transfer pipe 10. The length of the heat medium transfer pipe 10 changes depending on the temperature of the geothermal heat zone U, and it extends to the geothermal heat zone U where the flowing heat medium can be heated to around 200°C.

[0022] The medium injection pipe 50 is made of materials such as steel or stainless steel. In the high-temperature region of the geothermal heat zone U, the medium injection pipe 50 has cylindrical fins with circular cross sections welded to it in order to increase the outer periphery surface area and facilitate the transfer of heat from the geothermal heat zone U. In the low-temperature region close to the ground surface S, the medium injection pipe 50 has an insulating structure (described later) so that the heat of the hot water L1 injected under pressure from the hot water service tank 4 is not lost.

[0023] The heat medium transfer pipe 10 is provided with a cylindrical heat medium extraction pipe 80 inside the medium injection pipe 50, which transfers water heated in the geothermal heat U. The heat medium extraction pipe 80 is formed cylindrically inside and coaxial with the medium injection pipe 50. The heat medium extraction pipe 80 has a cylindrical shape on the inside of the pipe through which hot water L3 can pass, and its outside has a vacuum insulation structure or a structure with insulation material attached along the vertical direction.

[0024] The heat medium transfer pipe 10 will be described in further detail with reference to Figures 2 to 11. The heat medium transfer pipe 10 is composed of a medium injection pipe 50 and a heat medium discharge pipe 80. First, the medium injection pipe 50 will be described with reference to Figures 2 to 7. Figure 2 is a perspective view of the medium injection pipe 50 excluding the insulation material 70, and the medium injection pipe 50 is composed of the injection pipe 40, a pipe thread joint 51, a heat-insulating pipe 60 shown in Figure 5, and the insulation material 70. The medium injection pipe 50 is connected to the injection pipe 40 by the pipe thread joint 51, and forms a long tubular shape up to the deepest part U.

[0025] As shown in Figures 2 to 7, the outermost surface of injection tube 40, excluding gripping portion 47, is covered with a heat-resistant resin such as polyethylene, polypropylene, nylon 6, nylon 66, urethane foam, or fluorine to form a coating layer 46. As shown in Figures 4 and 6, injection tube 40 has male threads 42 with thread grooves formed on the slightly tapered outer surfaces of both ends. Note that female threads 52 and male threads 42 are indicated by diagonal lines in Figures 4, 6, and 7. Gripping portion 47 is provided in an exposed metal state in order to chuck medium injection tube 50 and hold medium injection tube 50 itself when screwing in pipe thread joint 51 while controlling the torque, and is not a part that constitutes coating layer 46. This is because providing coating layer 46 may hinder the gripping force.

[0026] 3, 4, 6, and 7, a pipe thread joint 51 has a female thread portion 52 with a thread groove formed on the inside so as to fit with the male thread portion 42. The pipe thread joint 51 has a mounting space portion 53 in the center of the inside, which is a space where the male thread portion 42 is not formed, and into which a protrusion 62, which will be described later, fits.

[0027] Next, the heat-insulating tube 60 shown in Fig. 3 to Fig. 7 includes an insertion tube 61 formed in a tubular shape with a total length of about 1200 mm and made of a heat-resistant resin such as polyimide, polyimideamide, 66 nylon, PEEK, polyamide, or fluorine. In addition, an annular protrusion 62, which has an inner diameter equal to the outer diameter of the insertion tube 61 and is made of the same resin, is joined to the center of the insertion tube 61 by ultrasonic welding or the like. As a result, the insertion tube 61 and the protrusion 62 are integrally formed. The heat-insulating tube 60 may be integrally formed by molding, not limited to welding. The vertical length of the heat-insulating tube 60 is formed so as to cover not only the gripping portion 47 but also a part of the covering portion 46, and is designed in consideration of the influence of heat transfer from the outside on the pipe thread joint 51 and the injection tube 40.

[0028] Since the outer diameter of the protruding portion 62 is larger than the inner diameter of the injection tube 40, the heat-retaining tube 60 does not fall into the inside of the injection tube 40, and the protruding portion 62 remains in the mounting space portion 53. In addition, since the outer diameter of the insertion tube 61 is smaller than the inner diameter of the injection tube 40, the insertion tube 61 enters the inside of the injection tube 40. Due to the above structure, the medium injection pipe 50 is connected by first screwing in the pipe thread joint 51, then inserting the insertion pipe 61 of the heat-insulating pipe 60 into the inside of the injection pipe 40, and then screwing the other injection pipe 40 into the pipe thread joint 51 from above to connect it.

[0029] In this way, the connection of the medium injection pipe 50 is completed by a simple operation. In addition, the heat-insulating pipe 60 not only improves the heat-insulating performance of the medium injection pipe 50, but also makes it easy to replace the heat-insulating pipe 60 itself and install the medium injection pipe 50. The protruding part 62 is formed so that the protruding part 62 is held between the injection pipes 40 even when the hot water is pumped by applying pressure by the pressurized water supply pump 3 so that the hot water does not boil. Therefore, the heat-insulating pipe 60 does not fall off. Incidentally, since both ends of the heat-insulating pipe 60 are held between the injection pipes 40, it will not fall off in the vertical direction. Similarly, the heat-insulating pipe 60 will not fall off in the vertical direction with respect to the heat medium extraction pipe 80 described later.

[0030] Next, the heat insulating material 70 provided around the medium injection tube 50 will be described with reference to Fig. 4. The heat insulating material 70 is in close contact with the periphery of the medium injection tube 50, and has a heat insulating layer 71 formed of a material such as glass wool, and a protective film portion 72 formed of a metal film such as aluminum on the outermost periphery. The heat insulating material 70 and the coating layer 46 provide a heat insulating structure for the outside of the medium injection tube 50.

[0031] Next, the heat medium extraction pipe 80 will be described with reference to Figures 7 and 8. The heat medium extraction pipe 80 is provided to recover heat deep underground using hot water, transport it to the ground, generate steam, and use the heat for steam power generation. With reference to Figures 2 to 6, the heat medium extraction pipe 80 will be described with reference to Figures 2 to 6, omitting explanations of parts that have exactly the same structure as the medium injection pipe 50, and will only describe the differences. The heat medium extraction pipe 80 is located inside the medium injection pipe 50, and is composed of an extraction pipe 81, a pipe thread joint 55, and a heat-insulating pipe 90.

[0032] The extraction pipe 81 corresponds to the structure of the injection pipe 40, the pipe thread joint 55 corresponds to the structure of the pipe thread joint 51, the mounting space 57 corresponds to the structure of the mounting space 53, the male thread portion 82 corresponds to the structure of the male thread portion 42, the female thread portion 56 corresponds to the structure of the female thread portion 52, the heat-insulating pipe 90 corresponds to the structure of the heat-insulating pipe 60, the covering layer 86 corresponds to the structure of the covering layer 46, the gripping portion 87 corresponds to the structure of the gripping portion 47, and the protruding portion 92 corresponds to the structure of the protruding portion 62. The heat medium extraction pipe 80 is provided with an insulating portion 85 along the vertical direction, the insulating portion 85 having an air layer or an insulating layer in which a heat insulating material is buried, which serves as a space inside. The heat medium extraction pipe 80 has an insulating structure due to the heat-insulating pipe 60, which prevents heat transfer.

[0033] In this way, the connection of the heat medium extraction pipe 80 can be completed by a simple operation, similar to the above-mentioned medium injection pipe 50. Furthermore, not only does the heat retention performance of the heat medium extraction pipe 80 improve with the heat-insulating pipe 90, but the heat-insulating pipe 90 itself can be easily replaced and the heat medium extraction pipe 80 can be easily installed. Furthermore, in addition to the medium injection pipe 50 also having a good heat retention state due to the heat-insulating pipe 60 and the heat-insulating structure, the heat medium extraction pipe 80 has an improved heat retention state due to the heat-insulating pipe 90, the heat insulating section 85, and the coating layer 86, making it possible to extract hot water L3 from underground without losing heat.

[0034] Next, data will be explained using experiments showing the heat retention performance of the present invention. Fig. 11(A) is a schematic diagram of a conventional medium injection pipe 101. Fig. 11(B) is a schematic diagram of a medium injection pipe 50 of the present invention. Fig. 11(B) shows the results of experimental data showing the heat retention performance of the conventional medium injection pipe 101 and the medium injection pipe 50 of the present invention. The applicant measured the temperature at each point (P1 to P8) as shown in the schematic diagram in Fig. 11 to compare the thermal insulation performance of the medium injection pipe 50 of the present invention with that of the conventional medium injection pipe 101, and calculated the temperature gradient. A heater was inserted inside both pipes (101, 50), and the water heated by the heater and the outside of the pipes were filled with water at room temperature. Compared to the medium injection pipe 101, the medium injection pipe 50 is additionally equipped with a heat-insulating pipe 60 and a coating layer 46.

[0035] As shown in FIG. 11(C), the measured temperature gradient was 890° C. / m between P1 and P2 of conventional medium injection pipe 101, and 3,980° C. / m between P5 and P6 of medium injection pipe 50 of the present invention. This indicates that medium injection pipe 50 of the present invention has a larger temperature difference than conventional medium injection pipe 101, and it can be confirmed that the insulation performance is improved by heat-insulating pipe 60. Furthermore, the temperature difference between P3 and P4 of the conventional medium injection pipe 101 was 3420°C / m, while the temperature difference between P7 and P8 of the medium injection pipe 50 of the present invention was 9790°C / m, indicating that the medium injection pipe 50 of the present invention has a larger temperature difference than the conventional medium injection pipe 101, and it can be confirmed that the insulation performance is improved by the coating layer 46. As described above, the present invention can include the heat medium transfer pipe 10 with improved thermal insulation performance.

[0036] Hot water L3 heated in geothermal heat zone U is reduced in pressure and boiled in pressure regulating valve PV1 to generate steam. Here, steam separator F is connected to pressure regulating valve PV1, and a nozzle capable of generating microbubbles or nanobubbles that become tiny bubbles by self-priming may be used for generating steam. This configuration can improve the efficiency of steam generation, so a sufficient amount of steam can be secured even if the speed at which the water is transported is reduced, and the time that the water spends in the heat absorption area of ​​geothermal heat zone U can be increased, giving the water time to absorb heat and producing high-temperature hot water.

[0037] Another example of the heat medium extraction pipe 80, which is another modified example with improved heat insulation performance, will be described with reference to Fig. 23. Fig. 23 is a vertical cross-sectional view showing a modified example of the heat medium extraction pipe 80a according to the first embodiment. Note that the same reference numerals are used to designate the same parts as in the above-mentioned example, and the above-mentioned description will be omitted. The heat medium extraction pipe 80a is provided to recover heat deep underground using hot water, transport it to the surface, generate steam at the pressure regulating valve PV1 (Fig. 1), and use the heat for steam power generation. The heat medium extraction pipe 80a is located inside the medium injection pipe 50, and is composed of an extraction pipe 81a, a pipe thread joint 55, and a heat retention pipe 91.

[0038] The extraction pipe 81a has a screw groove on the outer periphery at both ends. The pipe thread joint 55 has a screw groove on the inner periphery so as to fit with the screw groove of the extraction pipe 81a. The extraction pipe 81a can be extended by connecting the extraction pipes 81 to each other by fitting them with the pipe thread joint 55.

[0039] 23, the heat-insulating pipe 91 made of resin such as polyimide, polyimideamide, nylon 66, PEEK, polyamide, or fluorine is divided near the center of the pipe joint 55 and the middle of the extraction pipe 81a, and covers the entire length of the extraction pipe 81a. In this way, by covering not only a part of the heat medium extraction pipe 80a but the entire length of the extraction pipe 81a with the heat-insulating pipe 91, it is possible to transport the heat medium to the ground at low cost while maintaining the heat of the heat medium in a good state without providing an insulating structure such as an air layer or insulating material in the extraction pipe 81a.

[0040] The heat-insulating pipe 91 has annular protrusions 92a, 92b, which have an inner diameter equal to the outer diameter of the heat-insulating pipes 91a, 91b and are made of the same resin, joined to the center of the heat-insulating pipes 91a, 91b by ultrasonic welding or the like. As a result, the heat-insulating pipes 91a, 91b and the protrusions 92a, 92b are formed integrally. Note that the heat-insulating pipe 91 may be formed integrally by molding, not limited to welding.

[0041] Since the outer diameter of the protruding parts 92a, 92b is larger than the inner diameter of the extraction pipe 81a, the heat-insulating pipe 91 does not fall into the inside of the extraction pipe 81a, and the protruding parts 92a, 92b remain in the mounting space part 53. In addition, since the outer diameter of the inserted part of the heat-insulating pipe 91 is smaller than the inner diameter of the extraction pipe 81a, the heat-insulating pipe 91 enters the inside of the extraction pipe 81a. With the above structure, the extraction pipe 81a is connected by first screwing in the pipe thread joint 55, inserting the heat-retaining pipe 91 into the inside of the extraction pipe 81a, and then screwing the other extraction pipe 81a into the pipe thread joint 55 from above.

[0042] In this way, the work of connecting the heat medium extraction pipe 80a can be completed by a simple operation. In addition, the protrusions 92a, 92b are formed so that they are held between the extraction pipe 81a even when the hot water is pumped, while the pressurized water supply pump 3 applies pressure to prevent the hot water from boiling. Therefore, the heat retention pipe 91 will not fall off. As described above, since both ends of the heat retaining tube 91 are held between the outlet tubes 81a, the heat retaining tube 91 will not fall off in the vertical direction.

[0043] 23, the pipe thread joint 55 is provided with a heat insulating structure to prevent heat transfer by providing a pipe thread joint covering part 93 made of a tubular resin such as polyolefin resin or polypropylene resin that can be contracted when heat is applied, or a tape of polyolefin resin or polypropylene resin, after the extraction pipe 81a is connected by the pipe thread joint 51. With the above structure, the heat medium extraction pipe 80a blocks heat transfer at the pipe thread joint 55 by the pipe thread joint covering part 93.

[0044] In this embodiment, water is used as the medium for heat exchange in the geothermal zone U, but other possible media include oil, gas (inert gas (nitrogen, carbon dioxide, etc.)), or a medium with a lower boiling point than water used in binary power generation (such as a mixture of water and ammonia). Furthermore, when water or inert gas is used as the medium, even if the heat medium transfer pipe 10 is damaged and leaks to the outside, water or inert gas will not harm the environment and can be handled safely in terms of work.

[0045] (Steam water separator) The steam-water separator F shown in Fig. 1 is a cylindrical pressure vessel, and a nozzle provided inside the steam-water separator F sprays hot water L3 from the tip, separating steam V1 and hot water L4 inside the vessel. A pressure regulating valve PV1 for adjusting the pressure (amount of steam generated) is provided either inside or outside the steam-water separator F. A pressure regulating valve PV2 is provided in the passage leading to the hot water service tank 4 that recovers the drain L4, and can be used to adjust the steam pressure flowing from the steam-water separator F to the turbine T and to control the amount of steam flowing from the steam-water separator F to the turbine T.

[0046] (Hot water service tank) Next, the hot water service tank 4 will be described with reference to Fig. 1. The hot water service tank 4 is a cylindrical pressure vessel. The main piping connected to the hot water service tank 4 includes a piping for taking in condensate L6 sent from the condensing unit 17, a piping for taking in deaerated water L7 supplied from the water supply unit, a pump piping connected to the pressurized feed water pump 3 for sending hot water L8 from the hot water service tank 4, a drain injection pipe for taking in drain L4 sent from the steam separator F, and a steam discharge pipe for discharging steam V2 generated by pool boiling in the hot water service tank 4.

[0047] (Water supply unit) The water supply unit 18 generates soft water from raw water 16, such as river water or tap water, using an industrial soft water generator 9. The generated soft water is then stored in the make-up water tank 8. Dissolved oxygen is removed from the stored soft water using a deacidification device or a deacidification agent.

[0048] The deaerated water L7 from which oxygen has been removed is sent via the hot spring service tank 4 when the water is replaced with operating water after washing the heat medium transfer pipe 10 during the initial operation of the geothermal power generation system 1. By removing oxygen, rust prevention and scale generation in the heat medium transfer pipe 10 can be prevented. In particular, since the heat medium transfer pipe 10 has a long overall length, if scale generation on the inner wall is suppressed throughout the entire length of the transfer pipe, pressure loss can be reduced, leading to energy savings in the facility's electricity.

[0049] Representative examples of deoxidizers include hydrazine, tannin, and products derived from plants. There are also deoxidizers that use inert gases, and inert gases that are less likely to cause chemical reactions are used. Examples of inert gases that are less harmful include nitrogen and argon. In particular, as in the present invention, it is necessary to control the pressure of the heat exchange medium at high temperatures, so deoxidizers and deoxidizers that do not cause changes in the physical properties of the working fluid are preferable. Nitrogen and other substances can be made to dissolve easily in water using a microbubble generator, and then the dissolved water can be injected to facilitate replacement with oxygen.

[0050] During normal operation, the deaerated water L7 in the water supply unit 18 is low in temperature, so the deaerated water L7 is not directly fed to the hot water service tank 4, but is replenished via the condensation unit 18 to make up for any shortage of water. The condensation unit 18 can also be cooled using the raw water 16.

[0051] (Condensing unit) Next, the condensing unit 17 will be described. The condensing unit 17 has a function of condensing the steam V3 exhausted from the turbine T back into water, and is mainly composed of a condenser 6, a condensate tank 14, and a cooling tower CT. The steam V3 received by the condenser 6 is cooled in the cooling tower CT, condensed, and returned to hot water L10, which is stored in the condenser tank 14 via the condenser 6. The stored hot water L6 is sent to the hot water service tank 4 by the condensate pump 5, and stored in the hot water service tank 4. In addition, the cooling methods used by cooling tower CT include air cooling, water cooling using river water or seawater, and geothermal heat replacement, which exchanges heat underground.

[0052] (Method of generating electricity using the above system) The power generation method will be explained with reference to Figures 1, 9 and 10. The depth of the hole drilled by boring to obtain steam with a temperature of about 200°C on the ground reaches a depth of about 2000m to 3000m underground from 700m. It is considered that the deeper the depth, the higher the temperature that can be obtained, but it is determined based on the balance with the cost of drilling. A temperature of 200°C to 300°C is optimal for geothermal heat U, and the following values ​​will change appropriately depending on the temperature obtained near the deepest part of geothermal heat U.

[0053] First, the power generation method of the geothermal power generation system 1 will be described. A heat medium transfer pipe 10 is buried in the ground, and a medium injection pipe 50 is connected to the outer side of the heat medium transfer pipe 10 that contacts the ground and reaches deep into the ground. A heat medium extraction pipe 80 is connected to the inner side of the medium injection pipe 50 and reaches the bottom of the medium injection pipe 50. These heat medium transfer pipes 10 are used as a heat exchanger that absorbs heat obtained from a geothermal heat field U. This pressurized water power generation device A evaporates hot water and generates power through a steam turbine T. A power generation method using the pressurized water power generation device A will be described in detail below.

[0054] For example, hot water (L1) in the hot water service tank 4 is pressurized to 5 MPa by the pressurized water supply pump 3 and sent to the medium injection pipe 50 of the heat medium transfer pipe 10 at a flow rate of 55 t / h, and transported to a geothermal heat U deep underground. The hot water transported to the geothermal heat U at 210°C absorbs heat from the geothermal heat U through the medium injection pipe 50, which has high effective thermal conductivity, and finally becomes hot water (L2) at 200°C. Then, the hot water (L3) extracted from the heat medium extraction pipe 80 has an outlet temperature of 200°C and is transported to the steam-water separator F under a pressure of 2.0 MPa.

[0055] The steam separator F releases the pressure of the hot water (L3) at a temperature of 200°C by the pressure control valve PV1, reduces the pressure to about 0.6 MPa, and boils it, separating the steam generated at a rate of 6 t / h with a flash rate of about 11%. The steam separator F sends the generated steam (V1) to the steam turbine T. The generated steam (V1) is combined with steam (V2) generated in the hot water service tank 4 inside the steam separator F. The combined steam (V1+V2) drives the generator G by rotating the steam turbine T, generating electricity. The amount of electricity generated by this steam (V1+V2) is approximately 112 kWh, assuming an efficiency of 80%.

[0056] In addition, the steam separator F, which is connected to the hot water service tank 4 by piping, sends the approximately 89% of the hot water (L4) that does not become steam to the hot water service tank 4 at a flow rate of 49 t / h under a pressure of 0.6 MPa while maintaining the temperature at around 160°C.

[0057] In addition, steam (V3) exhausted from the steam turbine T is sent to a condenser 6. The steam (V4) sent to the condenser 6 is sent to an air-cooled or water-cooled cooling tower CT, where it is condensed and returned to hot water (L10) of 100°C and a pressure of 0.101 MPa. The returned hot water (L10) is stored in a condensate tank 14 at a flow rate of 6 t / h. In addition, the hot water (L6) in the condensate tank 14 is sent to the hot water service tank 4 by a condensate pump 5. Then, the hot water (L1) at about 130°C in the hot water service tank 4 is pressurized to 6 MPa again by the pressurized water supply pump 3 and sent to the medium injection pipe 50 of the heat medium transfer pipe 10 at a flow rate of 55 t / h, and is transported to the geothermal zone U deep underground.

[0058] 10 is a diagram showing the relationship between the depth of the heat medium transfer pipe 10 and the temperature distribution of the hot water in the pressurized water power generation plant 1. The dashed line shows the underground temperature distribution 21, and the solid line shows the temperature distribution of the hot water L1, L2, and L3 in the medium injection pipe 50 and the heat medium extraction pipe 80. The upper insulation region 22, defined by the dashed-dotted line, uses piping with excellent insulation properties, with medium injection pipe 50 made of a material with an effective thermal conductivity of 0.1 W / m K or less. The lower absorption region 26, defined by the dashed-dotted line, uses piping with excellent heat absorption properties, with medium injection pipe 50 made of a material with an effective thermal conductivity of 50 W / m K or more.

[0059] Furthermore, the heat medium extraction pipe 80 uses piping with excellent insulation properties, employing a material with an effective thermal conductivity of 0.1 W / m K or less, regardless of whether it is the heat insulating region 22 or the heat absorbing region 26. Due to the insulation properties, the hot water (L2) that has absorbed the heat from the deepest geothermal heat U can be transported to the pressure regulating valve PV1 without being affected by temperature changes along the way in the medium injection pipe 50.

[0060] Figure 9 is a schematic diagram of the changes in the state of water. Figure 9 shows the temperature and pressure when water changes from solid to liquid to gas. The solid line from the triple point to the critical point shows the evaporation curve 27. The boiling point at atmospheric pressure is 100°C and indicates 0.101MPa. Point C on the line is the boundary line where water changes from a gaseous state, i.e., steam, when the temperature is 200°C and the pressure is less than 1.554MPa.

[0061] Point D on the line is the boundary line where water changes from a gaseous state, or steam, when the temperature is 210°C and the pressure is less than 1.907 MPa. Moreover, the pressurized region 23 indicated by diagonal lines indicates a pressure region where the hot water L3 does not become steam, and the pressure value of the pressurized feed water pump 3 is set taking into consideration the pressure loss.

[0062] In temperature distribution 21, the temperature increases toward the depths of geothermal zone U, reaching 220°C. Because the medium injection pipe 50 and the heat medium extraction pipe 80 are made of a material with an effective thermal conductivity of 50 W / m K, the hot water (L1) introduced into the medium injection pipe 50 rises in temperature distribution 22 along the underground temperature distribution 21.

[0063] Here, even if the effective thermal conductivity of the heat medium extraction pipe 80 is set to a small value of 0.1 W / m K, when the pressure of the hot water L3 at the outlet of the heat medium extraction pipe 80 is lower than point C, the temperature distribution is lower than the evaporation curve 27, so steam is generated and the temperature drops to approach the boiling point.

[0064] When the water changes to steam inside the heat medium extraction pipe 80, it becomes a so-called gas-liquid two-phase flow, and the heat transfer coefficient is several tens of times higher than in the case of a single-phase flow of hot water, so heat is easily absorbed by the low-temperature downward flow L1 flowing through the heat medium extraction pipe 80 or the medium injection pipe 50. In order to prevent this heat loss and transport the hot water while maintaining its stored energy, it is necessary to make it difficult for the hot water to cool. And, the hot water above the boiling point heated in the geothermal heat zone U is transported to the steam separator F without cooling, thereby reducing heat loss. To reduce heat loss, it is necessary to maintain a pressure higher than the evaporation curve 27 in Figure 13, as mentioned above.

[0065] In particular, a temperature difference occurs in the heat medium transfer pipe 10, which serves as a heat exchanger, and buoyancy occurs due to the difference in water density. The pressure of the pressurized feed water pump 3 is insufficient to transfer the required flow rate through natural circulation by buoyancy alone, so pressure losses in the medium injection pipe 50 and the heat medium extraction pipe 80 must be taken into consideration.

[0066] It is also important that the pressure is kept high by the booster feed water pump 3 in order to maintain a pressure higher than the evaporation curve 27, and that the heat medium is not boiled in the heat medium transfer pipe 10. The advantage of the present invention is that it allows for the effective use of underground heat by transferring hot water L3, which retains the heat absorbed in the geothermal heat field U, to the pressure regulating valve PV1 in a so-called single-phase state.

[0067] For the above reasons, in the present invention, as shown by the shaded area in Figure 10, the insulating regions of the medium injection pipe 50 and the heat medium extraction pipe 80 are formed from a material with an effective thermal conductivity of 0.1 W / m·K or less. The best material has an insulating performance of 0.05 W / m·K to 0.001 W / m·K. Maintaining insulating performance has the advantage of preventing a drop in temperature at the outlet, which results in no need to set the pressure of the pressurized feed water pump 3 high. In Figure 14, the dashed line shows the underground temperature distribution 21 including the geothermal zone U, and the solid line shows the hot water temperature distribution 25.

[0068] In addition, taking into account the pressure losses in the medium injection pipe 50 and the heat medium extraction pipe 80, the outlet pressure of the hot water L3 is desirably in a pressure range 23 that is at least greater than the evaporation curve 27 in FIG. 9 by the pressurized feed water pump 3, and is set at a pressure that does not generate steam so that the hot water can be transported as it is, even if its temperature is above the boiling point.

[0069] Furthermore, in areas of high underground temperature distribution, i.e., the heat absorption areas required for power generation, the medium injection pipe 50 is made of a material with a high effective thermal conductivity of 50 W / m K. Any effective thermal conductivity can be used, but considering pressure and corrosion underground, it is preferable to use a metallic material, and an effective thermal conductivity of 20 W / m K or more is sufficient.

[0070] Second embodiment A geothermal power generation system 200 according to a second embodiment will be described with reference to Fig. 12. Fig. 12 is a schematic diagram showing the configuration of a geothermal power generation system 200 according to the second embodiment of the present invention. Note that the same reference numerals are used to designate the same parts as in the first embodiment, and the above-mentioned description will be omitted. The binary power generation system B will be described with reference to Figure 12. The binary power generation system B is mainly composed of a heat exchange section 150 connected to the pressurized water power generation system 1b, a steam turbine T2, a generator G2, a power receiving equipment TF2, a cooler 154 and a circulation pump 155.

[0071] In the present invention, hot water L3 obtained from a heat medium transfer pipe 10 provided in the pressurized water power generation plant 1b is separated into steam by a steam separator F, and drain L4 that does not become steam is temporarily stored in a storage tank 11. In addition, steam V3 obtained from a turbine T is returned to hot water by a condenser 6 and stored in the storage tank 11. The hot water L4 stored in the storage section 11 is supplied to a heat exchanger 151 of the binary power generation plant B.

[0072] The working medium M1 heated in the heat exchange section 150 evaporates and rotates the steam turbine T2, which in turn causes the generator G2 to generate electricity. The power receiving equipment TF supplies electricity and supplies it to electric power companies, etc. via the power grid. Here, the working medium M is a non-flammable, non-toxic inert gas such as HFC-245fa or R245fa, or a medium with a low boiling point (such as a mixture of water and ammonia, or a hydrocarbon (pentane)).

[0073] An expansion turbine or the like is used for the steam turbine T2. The working medium M2 that has passed through the steam turbine T2 is cooled by cooling water 157a, 158b of a cooler 156. In addition, the working medium M3 is condensed from a gas state to a liquid or the like and sent again to the heat exchanger 152 by a circulation pump 155.

[0074] By piping the cooling water 157b, 158b to the raw water 16 provided in the water supply unit 18 of the pressurized water power generation plant 1b and exchanging heat, the raw water 16 is heated and the cooling water 157b, 158b is cooled, thereby providing an effective exchange of heat throughout the geothermal power generation system 200. By heating the raw water 16, it becomes possible to directly input it into the hot water service tank 4 without passing through the condensation unit 17.

[0075] By using such working media (M1 to M3), power generation is possible with hot water of 70 to 95 degrees Celsius, if there is a flow rate of 9 to 24 t / h. In this system, the media exchange heat within a closed system.

[0076] The working media (M1 to M3) that can be used are determined by the temperature at which they are exchanged, so there are cases where temperature restrictions are set by the binary power generation system B. To accommodate such cases, the pressurized water power generation system 1b is provided with a temperature adjustment system 161 that utilizes the air cooling tower CT of the condensing unit 17. In particular, when the temperature of the drain L4 that did not become steam is high, it is possible to lower the temperature to a range that matches the set temperature of the binary power generation system B.

[0077] Furthermore, the hot water L3 sent from the heat medium transfer pipe 10 may be directly supplied to the heat exchanger 151 to generate electricity in the binary power generation device B, and when the temperature of the geothermal well at the deepest part U is low, it is possible to efficiently use geothermal heat to generate electricity.

[0078] Third embodiment A geothermal power generation system 300 according to a third embodiment will be described with reference to Fig. 13. Fig. 13 is a schematic diagram showing the configuration of a geothermal power generation system 300 according to the third embodiment of the present invention. Note that the same reference numerals are used to designate the same parts as those in the first and second embodiments, and the above-mentioned descriptions will be omitted. The binary power generation plant C will be described with reference to Figure 13. The binary power generation plant C is composed of a first heat exchange unit 150c, a second heat exchange unit 156c, a steam turbine T2, a steam turbine T3, which are connected to the pressurized water power generation plant 1b, a generator G2, a generator G3, a power receiving equipment TF2, a cooler 164c, a first circulation pump 155c, and a second circulation pump 165c.

[0079] In the present invention, hot water L3 obtained from a heat medium transfer pipe 10 provided in a pressurized water power generation plant 1c is separated into steam by a steam separator F, and drain L4 that does not become steam is passed through a first heat exchanger 151c. The working medium M1 heated in the first heat exchange section 150c evaporates to rotate the steam turbine T2, and generates electricity using the generator G2.

[0080] The power receiving facility TF2 supplies electricity to electric power companies and the like via a power grid. Here, the working medium M (M1 to M23) is a non-flammable and non-toxic inert gas such as HFC-245fa or R245fa, or a medium with a low boiling point (a mixture of water and ammonia, a hydrocarbon (pentane)). In this embodiment, the working medium (M1 to M3) used in the binary power generation device C is a working medium with a high boiling point range and a working medium (M21 to M23) with a boiling point lower than that of the working medium (M1 to M3), so that heat can be utilized in multiple stages, and efficient power generation can be achieved.

[0081] The steam turbines T2 and T3 are expansion turbines or the like. The working medium M2 that has passed through the steam turbine T2 is cooled by heat exchange in the second heat exchanger 153c of the second heat exchange section 154c. In addition, the working medium M3 is condensed from a gaseous state to a liquid or the like and sent again to the heat exchanger 152c by the circulation pump 155c. Further, heat exchange is performed by the second heat exchanger 153c of the second heat exchange section 154c, and the working medium M21 heated in the second heat exchange section 164c evaporates to rotate the steam turbine T3, and generates electricity by the generator G3.

[0082] The working medium M21 that has passed through the steam turbine T3 is cooled by cooling water 157c, 158c of the cooler 164c. In addition, the working medium M23 is condensed from a gaseous state to a liquid or the like and sent again to the second heat exchange section 154c by the circulation pump 165c. By piping the cooling water 157c, 158c to the raw water 16 provided in the water supply unit 18 of the pressurized water power generation system 1c and exchanging heat, the raw water 16 is heated and the cooling water 157c, 158c is cooled, thereby providing an effective exchange of heat throughout the geothermal power generation system 300. By heating the raw water 16, it becomes possible to directly input it into the hot water service tank 4 without passing through the condensation unit 17.

[0083] In addition, the method of cooling the working medium or medium such as water connected to the above-mentioned heat exchanger or condenser does not need to be limited to these, and various methods such as a cooling method using a heat exchange method using a Peltier element are possible.

[0084] (Fourth embodiment) A geothermal power generation system 100 according to a fourth embodiment will be described with reference to Fig. 14. Fig. 14 is a schematic diagram showing the configuration of a geothermal power generation system 100 according to the fourth embodiment of the present invention. Note that the same reference numerals are used to designate the same parts as in the first to third embodiments, and the above-mentioned description will be omitted. The binary power generation system B will be explained with reference to Figure 14. The binary power generation system B is mainly composed of a heat exchange section 150 connected to the pressurized water heat exchange system 1a, a steam turbine T2, a generator G2, a power receiving equipment TF2, a cooler 154 and a circulation pump 155.

[0085] In the geothermal power generation system 100, pressurized hot water L3 from the medium transfer pipe 10 provided in the pressurized water heat exchanger 1a is passed through the heat exchanger 151 as hot water without being converted into steam. Since the geothermal power generation system 100 does not have a steam-water separator F, the geothermal heat is absorbed by the hot water and used directly, reducing loss and enabling the geothermal heat to be recovered and used for power generation.

[0086] The working medium M1 heated in the heat exchange section 150 evaporates to rotate the steam turbine T2, and generates electricity using the generator G2. The power receiving equipment TF supplies electricity and supplies it to power companies, etc. via the power grid. Here, the working media M1, M2, and M3 are non-flammable, non-toxic inert gases such as HFC-245fa and R245fa, or media with low boiling points (such as a mixture of water and ammonia, or hydrocarbons (pentane)).

[0087] An expansion turbine or the like is used as the steam turbine T2. The working medium M2 that has passed through the steam turbine T2 is cooled by cooling water 157a, 158a of a cooler 156. In addition, the working medium M3 is condensed from a gas state to a liquid or the like and sent again to the heat exchanger 152 by a circulation pump 155.

[0088] By using such working media (M1 to M3), the geothermal power generation system 100 can generate power with hot water of 70° C. to 95° C. at a flow rate of 9 to 24 t / h. In this system, the working media exchange heat within a closed system.

[0089] Furthermore, the service tank 4 provided in the pressurized water heat exchanger 1a stores hot water cooled by the heat exchanger 152, and is necessary as an element for maintaining the pressure of the entire system of the pressurized water heat exchanger 1a constant, along with the pressurized water supply pump 3. In particular, when the pressurized water supply pump 3 is stopped for maintenance or the like, the pressurized water heat exchanger 1a experiences an increase or decrease in the water volume of approximately 2 tons of the entire system capacity, so in order to keep the water level constant and resume operation smoothly, the pressure in the service tank 4 can be controlled to keep the water level constant.

[0090] Fifth embodiment The heat medium transfer pipe 500 according to the fifth embodiment and the construction method of the heat medium transfer pipe 500 will be described with reference to Figs. 15 to 20. Fig. 15 is a longitudinal sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, with a portion omitted. Fig. 16 is a longitudinal sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, during construction. Fig. 17 is a longitudinal sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, during construction. Fig. 18 is a schematic view showing an enlarged view of a pipe thread joint 51 of the heat medium transfer pipe 500 according to the fifth embodiment. Fig. 19 is a longitudinal sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, with a portion omitted. Fig. 20 is a relationship diagram showing the relationship between the depth of the heat medium transfer pipe 500 of the geothermal power generation system according to the fifth embodiment and the temperature distribution of hot water. The same reference numerals are attached to the same parts as those in the first to fourth embodiments, and the above description will be omitted.

[0091] 15 shows an example of a heat medium transfer pipe 500 that extends from the surface S to a geothermal zone U to a depth of 3000 m at its deepest point. The heat medium transfer pipe 500 has the above-mentioned heat medium extraction pipe 80 at its center, and is also provided with the above-mentioned medium injection pipe 50, first protective pipe 31, second protective pipe 32, and third protective pipe 33 on its outer periphery. The first protective pipe 31 to third protective pipe are annular pipes that extend toward the geothermal zone U.

[0092] 20 is a diagram showing the relationship between the depth of the heat medium transfer pipe 500 and the temperature distribution of hot water when the heat medium transfer pipe 500 is applied to the pressurized water power generation plants 1, 1a, 1b, 1c (FIGS. 1 and 12 to 14) used in the first to fourth embodiments as shown in FIG. 20. The dashed line indicates the underground temperature distribution 21, and the solid line indicates the temperature distribution of the hot water L1, L2, L3 in the medium injection pipe 50 and the heat medium extraction pipe 80.

[0093] The upper insulation region 22, defined by the dashed-dotted line, uses piping with excellent insulation properties, with medium injection pipe 50 made of a material with an effective thermal conductivity of 0.1 W / m K or less. The lower absorption region 26, defined by the dashed-dotted line, uses piping with excellent heat absorption properties, with medium injection pipe 50 made of a material with an effective thermal conductivity of 50 W / m K or more.

[0094] Furthermore, the heat medium extraction pipe 80 uses piping with excellent thermal insulation properties, employing a material with an effective thermal conductivity of 0.1 W / m K or less, regardless of whether it is the heat insulating region 22 or the heat absorbing region 26. Due to the thermal insulation properties, the hot water (L2) that has absorbed the heat from the deepest geothermal heat field U can be transported, for example, to the pressure regulating valve PV1 in Figure 1, without being affected by temperature changes along the way in the medium injection pipe 50.

[0095] The first protective pipe 31 to the third protective pipe 33 are located in the insulating region 22 and each has an insulating structure. The side walls are hardened with geothermal cement or the like while the excavator is used to excavate deep into the ground, and the first protective pipe 31 to the third protective pipe 33 prevent the side walls from collapsing during excavation. 15 and 18, the first protective pipe 31 is provided with a convection shield plate 73 (convection shielding means) below the pipe thread joint 51 that connects the injection pipes 40 of the medium injection pipes 50, which shields convection up to the upper part of the disk-shaped hot water 74 and prevents a sudden blowout during construction, etc. The inner diameter of the convection shield plate 73 is smaller than the outer diameter of the pipe thread joint 51, and is structured so that it cannot be pulled out upward by the water pressure of groundwater, etc.

[0096] The convection shielding disk 73 prevents hot water that has entered the gap between the medium injection pipe 50 and the first protective pipe 31 from below from mixing with the low-temperature groundwater above due to convection and becoming low-temperature water, thereby further improving the heat retention performance of the medium injection pipe 50. Therefore, the heat medium transfer pipe 500 can further improve its heat retention performance by receiving the convection shielding disks 73 at multiple points in the vertical direction. The convection shielding disk 73 is not limited to being made of materials such as metal, resin, or rubber, and may be made of cloth or the like laid around the medium injection pipe 50.

[0097] Next, the heat medium transfer pipe 500 has a thermal insulation structure installed by a construction method described later between the first protective pipe 31 and the second protective pipe 32 and between the second protective pipe 32 and the third protective pipe 33. The heat medium transfer pipe 500 uses lightweight aggregate such as expanded polystyrene or concrete with a large amount of air bubbles mixed in or generated therein, so-called foamed concrete 36, 37, between the first protective pipe 31 and the second protective pipe 32 and between the second protective pipe 32 and the third protective pipe 33, to provide a thermal insulation structure with cushioning properties, thermal insulation properties, and non-water absorbency. Between the first protective pipe 31 and the second protective pipe 32 and between the second protective pipe 32 and the third protective pipe 33, closed sections 34, 35 that are closed with concrete material are provided below.

[0098] The blocking portions 34, 35 prevent the intrusion of water having a lower temperature than the medium injection pipe 50 from below, improving the heat insulating performance of the heat medium transfer pipe 500. The top of the heat medium transfer pipe 500 is also blocked with concrete or steel material (not shown) to prevent water from infiltrating from above.

[0099] Next, a method for installing the heat medium transport pipe 500 of the present invention will be described with reference to Figs. First, an excavation machine is used to excavate the largest diameter pipe up to the 700 m point. During excavation, the side walls are hardened with geothermal cement or the like to prevent collapse, and when the 700 m point is reached, a blockage section 35 is formed by filling the section from 10 m to 100 m deep with concrete material as shown in Figure 16, and the above-mentioned third protective pipe 33 is buried.

[0100] Next, as shown in Figures 15 and 17, the diameter of the excavator is reduced and excavation is performed to a size sufficient to bury the second protective pipe 32, and excavation is continued up to the 1500 m point. When the 700 m point is reached, as shown in Figure 17, a blockage section 34 is formed with concrete material in the entire lower diameter section from 10 m to 100 m deep, and the above-mentioned second protective pipe 32 is buried. Next, as shown in Figure 15, the diameter of the excavator is further reduced and excavation is performed to a size sufficient to bury the first protective pipe 31. The excavation is continued to a position approximately 1,700 m into the insulation area 22, and the above-mentioned first protective pipe 31 is buried.

[0101] Finally, as shown in Figure 15, the diameter of the boring machine is further reduced and the excavation is continued to a size large enough to bury the medium injection pipe 50. The excavation is continued to a position approximately 3000 m to the geothermal zone U of the desired temperature 210 in the heat endothermic region 26, and the above-mentioned medium injection pipe 50 and heat medium extraction pipe 80 are buried.

[0102] Here, the heat absorption region 26 does not necessarily have a sufficient amount of hot water, and the bedrock zone 38 or fractured zone 43 may also be present. After the excavation reaches the deepest part U, as shown in FIG. 15, if the heat absorption region 26 is the bedrock zone 38, water is filled between the bedrock zone 38 and the medium injection pipe 50 as a transfer promoting medium 39 in order to improve the thermal conduction between the medium injection pipe 50 and the geothermal zone U. The water may be injected later, but a method may also be used in which the water used during hydraulic fracturing or mud excavation is left as it is and used.

[0103] In addition, in the case where the heat absorption region 26 is the fractured zone 43 as shown in FIG. 19, since there is a gap between the fractured zones and no hot water, the heat medium transfer pipe 500 may have a metal cup-shaped receiver pipe 75 inserted between the medium injection pipe 50 and the fractured zone 43 to receive water as the transfer promotion medium 39. In order to improve the thermal conduction between the medium injection pipe 50 and the geothermal zone U, water is filled between the receiver pipe 75 and the medium injection pipe 50 as the transfer promotion medium 39. In addition, the transfer promotion medium 39 may be not only water but also a liquid resin containing a metal that easily transfers heat as a medium.

[0104] As described above, the present invention makes it possible to efficiently absorb heat from the geothermal zone U in the heat absorption area 26 by interposing an intermediary material between the heat medium transfer pipe 500 and the geothermal zone U, even if the geothermal zone U is a bedrock zone 38 or a crushed zone 43 which has poor heat transfer properties.

[0105] Receiver pipe 75 shown in Fig. 24 is a schematic diagram showing a part of the lower portion of receiver pipe 75 shown in Fig. 19. Receiver pipe 75 is provided with medium movement hole 76 which is a through hole penetrating the side surface. Receiver pipe 75 is provided with a hole so that a medium such as hot water can move through medium movement hole 76 when geothermal zone U is covered with a fluid medium such as hot water.

[0106] The receiving pipe 75 protects the medium injection pipe 50 from being crushed by rocks or the like due to the collapse of rocks or the like, and also prevents rocks or the like from entering the area where the side wall of the medium injection pipe 50 comes into contact with the medium such as hot water. The medium movement holes 76 may be holes formed in a mesh pattern using metal or the like. In this way, when the geothermal zone U is hot water, the receiving pipe 75 is preferably structured to prevent rocks, sand, etc. from contacting the medium injection pipe 50, and it is possible to ensure an area where fluids such as hot water come into contact with the medium injection pipe 50.

[0107] Sixth embodiment The configuration of a geothermal power generation system 400 according to the sixth embodiment of the present invention will be described with reference to Fig. 21 and Fig. 22. Fig. 21 is a schematic diagram showing the configuration of a geothermal power generation system 400 according to the sixth embodiment of the present invention. Fig. 22 is a schematic diagram showing the configuration of a heat medium transfer pipe 410f according to the sixth embodiment of the present invention.

[0108] As shown in FIG. 21, the geothermal power generation system 400 is mainly composed of a pressurized water supply pump 3, a plurality of heat medium transfer pipes 410(a-f), a hot water service tank 4, a condensate unit 17, a water supply unit 18, a steam-water separator F, a steam turbine T, a generator G, and a power receiving facility TF. In the geothermal power generation system 400, water as a medium is supplied from the pressurized water supply pump 3 through a medium injection pipe 50 at the deepest part of the ground, and the resulting hot water is pressurized and transported to the ground through a heat medium extraction pipe 80. The transported hot water L3 is reduced in pressure by a pressure regulating valve PV1 and boiled, and then transported to a steam-water separator F.

[0109] Steam and hot water are separated in a steam-water separator F, and the generated steam V1 is supplied to a steam turbine T. In the geothermal power generation system 400, the generated steam V1 is supplied to the steam turbine T to rotate a generator G to generate electricity, which is then supplied to a power receiving facility TF and then to a power company or the like via a power transmission network. The steam turbine T may be of not only a turbine type but also a screw type or the like, and may be any type capable of generating electricity using steam.

[0110] Since not all of the hot water L3 supplied to the steam-water separator F is converted into steam V1, a large amount of hot water L4, so-called drain, is sent from the steam turbine T to the hot water service tank 4. In addition, the steam V3 exhausted by the steam turbine T is sent to a condensing unit 17, and the steam V4 sent to the condensing unit 17 is sent to a cooling tower 15 connected to the condenser 6. The sent steam V4 is condensed and returned to water, passes through the condenser 6, and is temporarily stored in the condensate tank 14 before being sent to the hot water service tank 4 by the condensate pump 5.

[0111] Hot water L8 in the hot water service tank 4 is transferred as hot water L1 by the pressurized water supply pump 3 to the heat medium transfer pipe 410. The hot water L1 transferred by the pressurized water supply pump 3 absorbs heat from the geothermal heat again at a depth where the geothermal zone U is located, and is subjected to heat exchange. The heat-exchanged hot water L2 is transferred by the pressurized water supply pump 3 through the heat medium transfer pipe 410, which will be described later. Incidentally, in the present invention, a plurality of heat medium transfer pipes (410a to 410f) can also be applied to power generation facilities such as binary power generation facilities from A to B in the second to fifth embodiments described above.

[0112] As shown in Fig. 21, the heat medium transfer pipe 410 includes a plurality of heat medium transfer pipes (410a to 410f) installed from the surface S to the geothermal zone U. With reference to Fig. 22, the heat medium transfer pipe 410f will be described as a representative example of the heat medium transfer pipes 410 (410a to 410f). In the geothermal power generation system 400, the medium injection pipe 50 absorbs the geothermal heat from the geothermal heat zone U, exchanges heat with hot water (L2) as a heat medium, and transports the hot water (L3) to the ground. However, if the temperature of the transfer promotion medium 39 drops due to reasons such as the heat from the geothermal heat zone U near the medium injection pipe 50 not being restored, the flow path switching valve 413 and flow path switching valve 414 provided on the ground side of the heat medium transfer pipe 410f are switched to circulate water as a heat medium within the heat medium transfer pipe 410f leading to the geothermal heat zone U.

[0113] When circulating the hot water L3 in the heat medium transfer pipe 410f, a pressure pump 411 is provided to circulate the hot water L3 under pressure to prevent boiling. In addition, the geothermal power generation system 400 circulates the hot water L3 through the paths of the multiple heat medium transfer pipes 410 by the pressurized water supply pump 3 under pressure to prevent boiling even during normal power generation, but when one pressurized water supply pump 3 is not enough, the pressure pump 411 is used. The pressure pump 411 plays a role in regulating the pressure so that the pressure in the heat medium transfer pipe 410f is constant.

[0114] By applying pressure inside the heat medium transfer pipe 410f to prevent boiling and circulating the hot water through the heat medium transfer pipe 410f as a single-phase flow, it is possible to effectively absorb heat from the geothermal heat field U compared to the case where the hot water is circulated through the heat medium transfer pipe 410f as a two-phase gas-liquid flow.

[0115] The heat medium transfer pipe 410f is equipped with a circulation sensor unit 412 having a temperature sensor and a pressure sensor that measure the temperature and pressure of the hot water L3 in the middle of the circulation path. Even when power generation is not performed due to periodic maintenance or an unexpected drop in temperature of the geothermal heat zone U caused by a natural disaster or the like, the heat medium transfer pipe 410f can circulate water including the geothermal heat zone U by the pressure regulating valve PV1 so that the temperature of the hot water is uniform, and the temperature of the circulated hot water can be made uniform. Therefore, by measuring the circulation sensor unit 412 installed on the ground, even if the temperature in the geothermal heat zone U is unknown, the temperature state of the geothermal heat zone U can be estimated and used as an index for planning the amount of power generation.

[0116] (Technical features considered from the above embodiment) Below, examples of the technical features of this embodiment are shown in parentheses, but these are not particularly limiting and are merely examples, and the effects that can be expected from these features will also be described. <First characteristic point> A heat medium transfer pipe (e.g., mainly a heat medium transfer pipe 10 (medium injection pipe 50, heat medium extraction pipe 80) 410-500) that transports a medium (e.g., mainly water, oil, etc.) underground and recovers the medium that absorbs heat underground, the heat medium transfer pipe being characterized in that it includes a pipe joint (e.g., mainly a pipe thread joint 51-55) that connects a plurality of the heat medium transfer pipes, and a heat medium insulation pipe (e.g., mainly an insulation pipe 60-90) that continuously covers the pipe joint and a part of the heat medium transfer pipe inside the heat medium transfer pipe and keeps the heat held by the medium warm.

[0117] With the above features, the present invention not only improves the insulation performance of the heat medium transport pipe by the insulation pipe, but also makes it easier to replace the heat medium insulation pipe itself and to install the heat medium transport pipe.

[0118] <Second characteristic point> The heat medium insulation pipe is characterized by comprising an insertion pipe (e.g., mainly insertion pipes 61 and 91) to be inserted inside the heat medium transfer pipe, and a protrusion (e.g., mainly protrusions 62 and 92) having a diameter larger than the inner diameter of the heat medium transfer pipe and held inside the pipe joint. Due to the above-mentioned features, the present invention makes it easy to replace the heat medium insulation pipe itself and to install the heat medium transfer pipe.

[0119] <Third characteristic point> The heat medium transfer pipe is provided near a screw portion that screws together with the pipe joint when the heat medium transfer pipe is connected with the pipe joint, and includes a gripping portion (e.g., mainly gripping portions 47 and 87) that grips the heat medium transfer pipe, and a coating layer (e.g., mainly coating layers 46 and 86) that is coated with a heat insulating material and is provided to avoid the gripping portion, and the heat medium insulation pipe includes the insertion pipe that extends to at least the gripping portion. With the above features, the present invention improves the insulation performance of the heat medium transfer pipe by the heat medium insulation pipe of the connecting pipe without impairing the performance of the connecting work of the heat medium transfer pipe. In addition, the heat medium transfer pipe can extract the medium from the ground without losing heat.

[0120] <Fourth characteristic point> The heat medium transfer pipe includes a medium injection pipe (e.g., mainly a medium injection pipe 50) that transfers the medium into the ground, and a medium extraction pipe (e.g., mainly a heat medium extraction pipe 80) that extracts the medium that has absorbed heat from the ground to the surface, and is characterized in that the medium injection pipe and the medium extraction pipe are provided with the heat medium insulation pipes.

[0121] With the above features, the present invention improves the insulation performance of the medium injection pipe and the heat medium transport pipe by the heat medium insulation pipe. The heat medium transport pipe can extract the medium from the ground through the medium extraction pipe without losing heat.

[0122] <Fifth characteristic point> The system is characterized by comprising a generator (e.g., mainly generator G or binary generator B) that generates electricity by utilizing the heat of the medium extracted to the ground, a concrete insulation layer (e.g., mainly geothermal cement) that insulates the side walls of the hole excavated during excavation using cement in an insulation area for keeping the heat of the medium warm during transportation other than the absorption area where the medium absorbs the heat at the temperature required for electricity generation, a second coating layer (e.g., mainly insulation 70) that is coated with an insulating material around the medium injection pipe and pipe joints, and a pressure pump (e.g., mainly pressurized water pump 5) that maintains a pressure equal to or higher than the saturated vapor pressure of the medium at the desired temperature and transports the medium without changing its phase state.

[0123] Due to the above-mentioned features, the heat medium transfer pipe can extract the medium from the ground through the medium extraction pipe without losing heat, so that it is possible to generate power by utilizing geothermal heat itself.

[0124] <Sixth characteristic point> The heat medium transfer pipes are connected to each other by the pipe joints, and then the heat medium transfer pipes are provided with a pipe joint covering part (for example, mainly a pipe thread joint covering part 93) that covers the entire pipe joint from the outside. Due to the above-mentioned features, the heat medium transfer pipe is capable of blocking heat transfer at the pipe joint by the pipe joint covering portion.

[0125] <Seventh characteristic point> The heat medium transfer pipe (e.g., mainly heat medium transfer pipe 10 (medium injection pipe 50, heat medium extraction pipe 80)·410·500) transports a medium underground and recovers the medium that has absorbed heat underground, and is characterized in that convection blocking sections (e.g., mainly convection shielding disks 73) are provided at multiple positions in the vertical direction to block the upward and downward convection of groundwater that infiltrates between the heat medium transfer pipe and a tubular protective pipe (e.g., a third protective pipe 33) provided on the outer periphery of the heat medium transfer pipe.

[0126] With the above features, the convection breaker prevents hot water that has entered the gap between the heat medium transfer pipe and the protective pipe from below from mixing with the cooler water above through convection and becoming cooler water, thereby further improving the thermal insulation performance of the heat medium transfer pipe.

[0127] <8th characteristic point> The convection shielding member is located below a pipe joint that connects the heat medium transfer pipes, and is annular in shape and has an inner diameter that is larger than the outer circumference of the medium transfer pipes and smaller than the outer diameter of the pipe joint. Due to the above-mentioned features, the present invention provides a structure that will not fall out upward due to the water pressure of groundwater, etc., and also improves workability during installation.

[0128] <Ninth characteristic point> A heat medium transport pipe that transports a medium underground and recovers the medium that has absorbed heat underground, The heat transfer pipe is characterized by comprising a plurality of protective pipes (e.g., mainly a first protective pipe 31, a second protective pipe 32, and a third protective pipe 33) provided around the outer periphery of the heat transfer pipe, an insulating layer (e.g., mainly foamed concrete 36, 37) provided between the protective pipes and the other protective pipes, and a sealing layer (e.g., mainly blocking portions 34, 35) below the insulating layer to prevent groundwater from entering from below.

[0129] Due to the above-mentioned features, the sealing layer prevents the intrusion of water having a lower temperature than the heat medium transfer pipe from below, thereby improving the heat insulating performance of the heat medium transfer pipe.

[0130] <10th characteristic point> The heat insulating layer is characterized in that it is formed from a light base material or concrete containing a large amount of air bubbles. With the above features, the present invention not only prevents water from entering, but also improves the heat insulating performance by allowing the material to contain a large amount of air, etc.

[0131] <11th characteristic point> 9. The heat medium transport pipe according to claim 8, wherein the sealing layer is made of concrete. With the above-mentioned features, the present invention can prevent the infiltration of water by the sealing layer, and prevents a temperature drop in the heat medium transfer pipe due to the infiltration of groundwater.

[0132] <12th characteristic point> The geothermal power generation system includes a plurality of heat medium transfer pipes (e.g., mainly heat medium transfer pipes 10 (medium injection pipe 50, heat medium extraction pipe 80), 410, 500) that transport a medium (e.g., mainly water, oil, etc.) underground and recover the medium that has absorbed heat underground, and generates power using the heat of the recovered medium. In order to circulate the medium within the heat medium transfer pipes, the system includes a switching valve (e.g., mainly a flow path switching valve 414) that switches the flow path of the medium, and a pressure adjustment device (e.g., mainly a pressure pump 411) that circulates the medium while maintaining the pressure at a predetermined pressure without changing the state of the medium, and when the temperature of the medium drops, the switching valve and the pressure adjustment device are driven to circulate the medium within the heat medium transfer pipes until the temperature of the medium is restored.

[0133] Due to the above features, the present invention applies pressure inside the heat transfer pipe to prevent boiling, and circulates hot water inside the heat transfer pipe as a single-phase flow, making it possible to absorb heat from the geothermal heat source U more efficiently than when circulating hot water as a two-phase gas-liquid flow.

[0134] <The 13th characteristic point> The circulation path of the medium is provided with a temperature measuring device (for example, mainly a circulation sensor unit 412 (temperature sensor)) for measuring the temperature of the medium. Due to the above features, even if the temperature of the geothermal zone is unknown, the present invention makes it possible to circulate the hot water, including the geothermal zone, so that the temperature of the hot water is uniform, and to measure the temperature of the circulated hot water using a temperature measuring device, which can be used as an indicator of whether the temperature of the geothermal zone has recovered.

[0135] <14th characteristic point> A method for constructing a heat medium transport pipe (e.g., mainly a heat medium transport pipe 10 (medium injection pipe 50, heat medium extraction pipe 80), 410, 500) that transports a medium (e.g., mainly water, oil, etc.) underground and recovers the medium that has absorbed heat underground, the method includes a first sealing step of pouring cement (e.g., mainly cement, geothermal cement) into a drilled hole to form a first sealing layer (e.g., mainly a blocking portion 35) that seals the drilled hole, a first protective pipe embedding step of embedding a first protective pipe (e.g., mainly a first protective pipe 31) in the hole formed by the first sealing step, and after the first sealing layer is stabilized, a hole with a diameter smaller than that of the hole in the first sealing layer is excavated together with the first sealing layer, and cement is poured into the excavated hole to form a second sealing layer (e.g., mainly a blocking portion 34) that seals the excavated hole. a second sealing step of forming a hole in the second sealing layer, a second protective pipe embedding step of embedding a second protective pipe (e.g., mainly the second protective pipe 32) in the hole formed by the second sealing step, a third protective pipe embedding step of excavating the second sealing layer together with the second sealing layer with a diameter smaller than the hole of the second sealing layer after the second sealing layer has stabilized, and embedding a third protective pipe (e.g., mainly the third protective pipe 33) in the excavated hole, and a heat transfer pipe embedding step of pouring foam concrete (e.g., mainly foam concrete 36, 37) between the first protective pipe and the second protective pipe, and between the second protective pipe and the third protective pipe, after the insulation layer forming step and the third protective pipe embedding step, excavating with a diameter smaller than the hole of the third protective pipe, and embedding the heat transfer pipe in the excavated hole.

[0136] With the above-mentioned features, the present invention prevents the intrusion of water having a lower temperature than the hot water flowing through the heat medium transfer pipe from below, thereby improving the thermal insulation performance of the heat medium transfer pipe.

[0137] <15th characteristic point> This geothermal power generation method includes a plurality of heat medium transfer pipes (e.g., mainly heat medium transfer pipes 10 (medium injection pipe 50, heat medium extraction pipe 80), 410, 500) that transport a medium (e.g., mainly water, oil, etc.) underground and recover the medium that has absorbed heat underground, and generates power using the heat of the recovered medium, characterized in that an insertion hole is formed in a rock mass (e.g., mainly bedrock zone 38) present in a geothermal zone, the insertion hole being a hole with a larger diameter than the heat medium transfer pipes, a transfer promotion medium (e.g., mainly transfer promotion medium 39) and the heat medium transfer pipes are inserted into the insertion hole, and heat from the geothermal zone is transferred to the heat medium transfer pipes via the transfer promotion medium.

[0138] Due to the above-mentioned features, the present invention makes it possible to efficiently absorb heat from a geothermal zone by interposing an intermediary material between the heat medium transfer pipe and the geothermal zone, even if the geothermal zone is a bedrock zone or a fractured zone where heat transfer is poor.

[0139] <16th characteristic point> This geothermal power generation method includes a plurality of heat medium transfer pipes that transport a medium (e.g., mainly water, oil, etc.) underground and recover the medium that has absorbed heat underground, and generates power using the heat of the recovered medium, the method comprising the steps of: providing an insertion hole, which is a hole formed in a fractured zone (e.g., mainly fractured zone 43) present in a geothermal zone and has a diameter larger than that of the heat medium transfer pipes; and providing a medium container (receiving pipe 75) that is inserted into the insertion hole and contains a transfer promotion medium (e.g., mainly transfer promotion medium 39, water, oil, etc.), inserting the medium container, and transferring heat from the geothermal zone to the heat medium transfer pipes via the transfer promotion medium contained in the medium container.

[0140] Due to the above-mentioned features, the present invention makes it possible to efficiently absorb heat from a geothermal zone by interposing an intermediary material between the heat medium transfer pipe and the geothermal zone, even if the geothermal zone is a bedrock zone or a fractured zone where heat transfer is poor.

[0141] Another technical feature is that the medium container is provided with a plurality of through holes (e.g., mainly medium transfer holes 76). This makes it possible to protect the heat medium transfer pipe in the event of a geothermal zone collapse, etc., and to maintain the state of heat transfer of the medium, such as the geothermal zone fluid, to the heat medium transfer pipe.

[0142] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as it falls within the technical scope of the present invention. [Industrial Applicability]

[0143] As shown in the above-mentioned embodiment, the present invention can be used not only in geothermal areas where hot springs gush out, but also in volcanic areas and underwater volcanic areas. [Explanation of symbols]

[0144] 1·200·300·400…Geothermal power generation system, 1a, 1b, 1c...pressurized water power generation device, 3...pressurized water supply pump, 4...hot water service tank, 5... Condensate pump, 6... Condenser, 10·410(a~f)·500... Heat medium transfer pipe, 27... evaporation curve, 31... first protective tube, 32... second protective tube, 40... injection tube, 42·82... Male thread portion, 33... Third protective tube, 34·35... Foam concrete, 36-37... Foam concrete, 38... Rock zone, 39... Transmission promoting medium, 43... Fracture zone, 50...medium injection pipe, 51·55...pipe thread joint, 52·56...female thread portion, 53·57... placement space portion, 46·86... covering layer, 47·87... gripping portion, 60·90…heat-insulating pipe, 61·91…insertion pipe, 62·92…projection portion, 73…convection shield plate, 75... receiving pipe, 76... medium transfer hole, 80·80a... heat medium extraction pipe, 81... extraction pipe, 85...insulation part, 93...pipe thread joint coating part, 150...heat exchange part, 151...heat exchanger, 155...circulation pump, 414...flow path switching valve, 411...pressure pump, 412...Circulation sensor unit, T·T2·T3...Steam turbine, G...Generator, B: Binary power generation equipment, CT: Cooling tower, F: Steam-water separator, TF: Power receiving equipment, S...surface, U...geotropic zone.

Claims

1. A buried pipe for transporting a medium underground and recovering the medium that has absorbed heat underground, the buried pipe being used to utilize the recovered heat above ground, A buried pipe characterized by having a hole on the side to ensure a certain distance so as not to hinder the convection of underground fluid around the heat medium transfer pipe.

2. A buried pipe for transporting a medium underground and recovering the medium that has absorbed heat underground, the buried pipe being used to utilize the recovered heat above ground, A pipe for transferring heat to the heat medium transfer pipe, the pipe being disposed around the heat medium transfer pipe in a high temperature geothermal zone; A transfer promoting medium is provided between the heat medium transport pipe and the pipe, The buried pipe is characterized in that the transmission promoting medium is water or groundwater used during groundwater pressure fracturing or mud excavation.

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