Geothermal power generation system

Abstract

To provide a heat medium transfer pipe which enables improvement of heat insulation capability of the heat medium transfer pipe for transferring a medium to utilize heat, obtained from a geothermal zone, with the medium on the ground more effectively, 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 take-out pipe 80) transfers a medium (for example, mainly, water and oil etc.) to an underground area and recovers the medium absorbing heat in the underground area. The heat medium transfer pipe includes: pipe joints 51, 55 which connect the multiple heat medium transfer pipes provided; and heat medium thermal insulation pipes 60, 90 which continuously cover the pipe joints and parts of the heat medium transfer pipe to keep heat retained by the medium in the heat medium transfer pipe.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, as well as a geothermal power generation system and buried pipe that use the heat medium transfer pipe to generate electricity. [Background technology]

[0002] Conventional geothermal power generation systems use natural steam extracted from geothermal fields using natural pressure, separating the steam and water before use. As a result, the extracted steam contains large amounts of sulfur and other impurities that are unique to geothermal fields. These impurities turn into scale and adhere to thermal wells, piping, turbine blades, etc. As scale builds up, the amount of power generated decreases over time, making it difficult to use for long periods of time.

[0003] Patent Document 1 proposes a geothermal power generation system in which a closed-loop circulation flow path is formed 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 then returns to be used for heat exchange with geothermal fluid or geothermal heat again, and in which a closed-loop flow path is formed for the cooling fluid that cools the low-boiling-point medium by releasing heat into the ground, 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 the temperature of the cooling fluid is controlled and the cooling fluid is supplied to the condenser so as to optimize the condensation and liquefaction of the low-boiling-point medium in the condenser.

[0004] Patent Document 2 discloses a general pipe threaded joint used in heat transfer pipes that efficiently recover heat transfer media, and describes a pipe threaded joint that is composed of a pin and a box, each of which has a contact surface with 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 being located on the end face of the pin tip, 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 having at least one groove that communicates with the non-contact area and the interior of the threaded joint. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-84857 [Patent Document 2] Special Publication No. 2014-517925 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0006] As mentioned above, in power generation methods that use pumped hot spring water, scale builds up in geothermal and production wells, as well as on piping and turbines, resulting in a decrease in power generation over time. Regular maintenance is also required to remove the scale. From an environmental perspective, pumping hot spring water for use can also have an impact on the discharge rate of hot spring water. After pumping hot spring water for power generation, the water is returned to the earth through a reinjection well, but this water contains chemicals used to remove the scale, which has a significant impact on the environment. Furthermore, as seen in Patent Document 1, the method of generating electricity by utilizing only underground heat is environmentally friendly and effective because there is no need to consider concerns about the amount of hot spring water or chemical substances.

[0007] Furthermore, heat transfer pipes are required to recover heat underground and transport the resulting hot water to the surface, and although the length of the heat transfer pipes depends on the temperature of the geothermal field, they must be 1,000 to 3,000 meters long. These pipes are connected with pipe thread joints and extend deep underground. As shown in Patent Document 2, pipe thread joints are required to have high compression resistance and sealing performance under internal and external pressures, and are firmly joined to the pipes.

[0008] However, pipe thread joints are not designed to improve thermal insulation, and near the surface where temperatures are low, heat transfer occurs between the inside and outside of the pipe, resulting in the loss of heat recovered from underground.In addition, not only pipe thread joints but also transfer pipes that require thermal insulation become more difficult to achieve due to the need to balance strength with the larger diameter, making the thermal insulation structure more difficult to achieve, and the situation is becoming technically challenging. Furthermore, there is a growing demand for technology that improves the ease of installation without impairing the thermal insulation performance of the heat-retaining structure. Therefore, in order to effectively utilize the heat transfer medium obtained from underground, a technology has become necessary that can 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 these 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 insulating 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 field 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 transfer pipe that transports a medium underground and recovers the medium that has absorbed heat underground. A geothermal power generation device in which the following is buried: In the low temperature region of the geothermal zone a plurality of protective tubes are provided around the heat medium transfer tube; In the high temperature region of the geothermal zone Around the heat medium transfer pipe, A receiving pipe with multiple holes on the side and an open bottom It is characterized by being provided with

[0012] With the above features, the sealing layer prevents the intrusion of water with a temperature lower than that of the heat transfer pipe from below, improving the thermal 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 to move through the holes. [Brief explanation 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. [Figure 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. [Figure 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 cross-sectional view of a portion of the medium injection pipe of the present invention according to the first embodiment. [Figure 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 cross-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 longitudinal sectional view of a portion of the heat medium transfer pipe according to the first embodiment of the present invention. [Figure 8] FIG. 8 is a vertical cross-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 the change in state of water according to the first embodiment of the present invention. [Figure 10] FIG. 10 is a graph 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 a 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 a 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 longitudinal sectional view of a heat medium transfer pipe according to a fifth embodiment of the present invention, with a portion thereof omitted. [Figure 16] FIG. 16 is a vertical cross-sectional view of a heat medium transfer 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 transfer pipe according to a fifth embodiment of the present invention during installation. [Figure 18] FIG. 18 is a schematic enlarged view of a pipe thread joint portion of a heat medium transfer pipe according to a fifth embodiment of the present invention. [Figure 19] FIG. 19 is a longitudinal sectional view of a heat medium transfer 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 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 cross-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 INVENTION

[0014] Embodiments of 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 exemplify some of the embodiments of the present invention and are not intended to limit the present invention to these configurations. Appropriate modifications can be made without departing from the spirit of the present invention. Corresponding components in each drawing are designated 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 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 resulting hot water to the surface through heat medium extraction pipe 80 while pressurizing it. The transported hot water L3 is reduced in pressure by pressure control valve PV1 and boiled, and then transported to steam separator F. Steam and hot water are separated in steam 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, which rotates a generator G to generate electricity, and supplies the electricity to a power receiving facility TF, which then supplies the electricity to electric power companies, etc. via the power transmission network. The steam turbine T may be 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 boiling hot water L3 under reduced pressure, and the hot water and steam are separated in a steam separator F.

[0018] Because 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, or drain, is sent from the steam-water separator F 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 a condenser 6. The sent steam V4 is condensed and returned to water, passes through the condenser 6, and is temporarily stored in a condensate tank 14 before being sent to the hot water service tank 4 by a 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 deep in the geothermal zone U and undergoes 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 portion of the heat medium transfer pipe 10 according to the first embodiment of the present invention. FIG. 3 is a perspective view showing a portion of an exploded medium injection pipe 50 according to the first embodiment of the present invention. FIG. 4 is a longitudinal sectional view of a portion of the medium injection pipe 50 according to the first embodiment of the present invention. FIG. 5 is a perspective view of an insulated pipe 60 according to the first embodiment of the present invention. FIG. 6 is a longitudinal sectional view of a portion of the medium injection pipe 50 according to the first embodiment of the present invention. FIG. 7 is a longitudinal sectional view of a portion of the heat medium transfer pipe 50 according to the first embodiment of the present invention. FIG. 8 is a longitudinal sectional view of a portion of the heat medium extraction pipe 80 according to the first embodiment of the present invention. FIG. 9 is a schematic diagram showing changes in the state of water according to the first embodiment of the present invention. FIG. 10 is a relationship diagram showing the relationship between the depth of the heat medium transfer pipe 10 and the temperature distribution of hot water in the geothermal power generation system 1 according to the first embodiment of the present invention.

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

[0022] The medium injection pipe 50 is made of a material 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 its outer periphery to increase the 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) to prevent the heat from being lost from the hot water L1 injected under pressure from the hot water service tank 4.

[0023] The heat medium transfer pipe 10 has 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 cylindrically formed inside and coaxial with the medium injection pipe 50. The heat medium extraction pipe 80 has a cylindrical shape that allows hot water L3 to pass through the inside of the pipe, and its outside has a vacuum insulation structure or a structure with insulation attached along the vertical direction.

[0024] The heat medium transfer pipe 10 will be further described in 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 extraction 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 insulating material 70, and the medium injection pipe 50 is composed of the injection pipe 40, a pipe thread joint 51, an insulation pipe 60 shown in Figure 5, and the insulating material 70. The medium injection pipe 50 is formed by connecting the injection pipes 40 with the pipe thread joint 51, forming a long tubular shape up to the deepest part U.

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

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

[0027] Next, the insulated pipe 60 shown in Figures 3 to 7 includes an insertion pipe 61, approximately 1200 mm long and formed into a tubular shape from a heat-resistant resin such as polyimide, polyimideamide, nylon 66, PEEK, polyamide, or fluorine. A ring-shaped protrusion 62, made of the same resin and with an inner diameter equal to the outer diameter of the insertion pipe 61, is joined to the center of the insertion pipe 61 by ultrasonic welding or the like. This integrally forms the insertion pipe 61 and the protrusion 62. The insulated pipe 60 may also be integrally formed by molding, rather than by welding. The vertical length of the insulated pipe 60 is formed to overlap not only the gripping portion 47 but also a portion of the covering portion 46, and is designed to take into account the influence of external heat transfer on the pipe thread joint 51 and the injection pipe 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 placement space portion 53. Furthermore, 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 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 onto the pipe thread joint 51 from above to connect them.

[0029] In this way, connecting the medium injection pipe 50 is completed with a simple operation. Furthermore, 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. Furthermore, the protruding portion 62 is formed so that it is held between the injection pipes 40 even when the hot water is pumped by the pressurized water supply pump 3 to prevent the hot water from boiling. Therefore, the heat-insulating pipe 60 will not fall off. Furthermore, 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 below.

[0030] Next, the heat insulating material 70 provided around the medium injection pipe 50 will be described with reference to Figure 4. The heat insulating material 70 is in close contact with the periphery of the medium injection pipe 50 and has a heat insulating layer 71 made of a material such as glass wool and a protective film portion 72 formed on the outermost periphery from a metal film such as aluminum. The heat insulating material 70 and coating layer 46 provide a heat insulating structure for the outside of the medium injection pipe 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 installed to recover heat deep underground using hot water, transport it to the surface, generate steam, and use the heat for steam power generation. With reference to Figures 2 to 6, explanations of the parts of the heat medium extraction pipe 80 that are exactly the same as those of the medium injection pipe 50 will be omitted, and only differences will be described. 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 an insulation 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 coating layer 86 corresponds to the structure of the coating layer 46, the gripping portion 87 corresponds to the structure of the gripping portion 47, and the protrusion 92 corresponds to the structure of the protrusion 62. The heat medium extraction pipe 80 is provided with an insulating portion 85 extending in the vertical direction, the insulating portion 85 having an air layer or an insulating layer in which a heat insulating material is embedded inside as a space. The heat medium extraction pipe 80 has an insulated 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-insulating performance of the heat medium extraction pipe 80 improve with the heat-insulating pipe 90, but the heat-insulating pipe 90 itself can also be easily replaced and the heat medium extraction pipe 80 can be easily installed. Furthermore, the heat medium extraction pipe 80 is well insulated by the heat-insulating pipe 60 and the heat-insulating structure of the medium injection pipe 50, and the heat-insulating pipe 90, the heat insulation section 85, and the coating layer 86 improve the heat insulation state of the heat medium extraction pipe 80, making it possible to extract hot water L3 from underground without losing heat.

[0034] Next, experimental data demonstrating the heat retention performance of the present invention will be explained. Figure 11(A) is a schematic diagram of a conventional medium injection pipe 101. Figure 11(B) is a schematic diagram of a medium injection pipe 50 of the present invention. Figure 11(B) shows experimental data results 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 Figure 11 to compare the thermal insulation performance of the medium injection pipe 50 of the present invention with that of a conventional medium injection pipe 101, and calculated the temperature gradient. Heaters were inserted into the interiors of both pipes (101, 50), and the exteriors of the pipes were filled with water heated by the heaters and room temperature water. Compared to the medium injection pipe 101, the medium injection pipe 50 additionally includes a heat-insulating pipe 60 and a coating layer 46.

[0035] As shown in Figure 11 (C), the measured temperature gradient was 890°C / m between P1 and P2 of the conventional medium injection pipe 101, and 3980°C / m between P5 and P6 of the medium injection pipe 50 of the present invention, indicating that the medium injection pipe 50 of the present invention has a larger temperature difference than the conventional medium injection pipe 101, and confirming that the insulation performance is improved by the 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 confirming that the insulation performance is improved by the coating layer 46. As described above, the present invention can be provided with a heat medium transfer pipe 10 having improved heat insulating performance.

[0036] Hot water L3 heated in geothermal heat zone U is decompressed and boiled by pressure regulating valve PV1 to generate steam. Here, steam separator F is connected to pressure regulating valve PV1, and the nozzle used to generate steam may be a nozzle capable of generating microbubbles or nanobubbles, which become tiny bubbles through self-priming. This configuration improves steam generation efficiency, ensuring a sufficient amount of steam even when the water transport speed is reduced. This allows the water to spend more time in the heat absorption zone of geothermal heat zone U, 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-described example, and the same description will be omitted. The heat medium extraction pipe 80a is installed to recover heat deep underground using hot water, transport it to the surface, generate steam using the pressure regulating valve PV1 (Figure 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 an insulation pipe 91.

[0038] The extraction pipe 81a has threads on the outer periphery at both ends. The pipe thread joint 55 has threads on the inner periphery so as to fit with the threads 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 a resin such as polyimide, polyimideamide, 66 nylon, 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 portion 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 a good thermal insulation state of the heat medium, 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 and 92b, which have the same inner diameter as the outer diameter of the heat-insulating pipes 91a and 91b and are made of the same resin, joined to the center of the heat-insulating pipes 91a and 91b by ultrasonic welding or the like. As a result, the heat-insulating pipes 91a and 91b and the protrusions 92a and 92b are formed integrally. Note that the heat-insulating pipe 91 may also be formed integrally by molding, not just welding.

[0041] Because the outer diameter of the protruding portions 92a and 92b is larger than the inner diameter of the extraction pipe 81a, the heat-insulating pipe 91 does not fall into the extraction pipe 81a, and the protruding portions 92a and 92b remain in the placement space 53. In addition, because the outer diameter of the insertion portion of the heat-insulating pipe 91 is smaller than the inner diameter of the extraction pipe 81a, the heat-insulating pipe 91 enters the interior of the extraction pipe 81a. With the above structure, the extraction pipe 81a is connected by first screwing in the pipe thread joint 55, then inserting the heat-retaining pipe 91 into the extraction pipe 81a, and then screwing in another extraction pipe 81a from above and connecting it to the pipe thread joint 55.

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

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

[0044] In this embodiment, water is used as the medium for heat exchange in the geothermal zone U, but other possible mediums 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 an inert gas is used as the medium, even if the heat medium transfer pipe 10 is damaged and leaks to the outside, water or an 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 that adjusts 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 this adjusts the steam pressure flowing from the steam-water separator F to the turbine T, and can also be used 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 Figure 1. The hot water service tank 4 is a cylindrical pressure vessel. The main pipes connected to the hot water service tank 4 include a pipe that takes in condensate L6 sent from the condensing unit 17, a pipe that takes in deaerated water L7 supplied from the water supply unit, a pump pipe that is connected to the pressurized feed water pump 3 and sends hot water L8 from the hot water service tank 4, a drain injection pipe that takes in drain L4 sent from the steam-water separator F, and a steam discharge pipe that discharges steam V2 generated by pool boiling in the hot water service tank 4.

[0047] (Water supply unit) The water supply unit 18 produces soft water from raw water 16, such as river water or tap water, using an industrial soft water production device 9. The produced 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 deacidifier.

[0048] During the initial operation of the geothermal power generation system 1, 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. By removing oxygen, rust can be prevented and scale formation can be suppressed inside the heat medium transfer pipe 10. In particular, since the heat medium transfer pipe 10 has a long overall length, suppressing scale formation on the inner wall throughout the entire length of the transfer pipe can reduce pressure loss, leading to energy savings in the plant.

[0049] Typical examples of deoxidizers include hydrazine, tannin, and products derived from plants. There are also deoxidizers that use inert gases, which are less likely to cause chemical reactions. Examples of inert gases include less harmful nitrogen and argon. In particular, as in the present invention, where the pressure of the heat exchange medium must be controlled at high temperatures, deoxidizers and deoxidizers that do not cause changes in the physical properties of the working fluid are preferred. Nitrogen and other substances can be easily dissolved in water using a microbubble generator, and then the dissolved water can be injected, making it easier for the nitrogen to be replaced with oxygen.

[0050] During normal operation, the temperature of the deaerated water L7 is low, so the water supply unit 18 replenishes the shortage of water via the condensing unit 18, rather than directly putting it into the hot water service tank 4. The condensing 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 the 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 then passed through the condenser 6 and stored in the condensate tank 14. 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, cooling tower CTs can be cooled using air-cooling, water-cooling using river water or seawater, or geothermal heat replacement, which involves heat exchange underground.

[0052] (A method of generating electricity using the above system) The power generation method will be explained with reference to Figures 1, 9, and 10. To obtain steam at a temperature of around 200°C above ground, the hole drilled by boring reaches a depth of 700m to 2000m-3000m underground. It is thought that the deeper the hole, the higher the temperature that can be obtained, but this depth is determined by balancing with drilling costs. A temperature of 200°C to 300°C is optimal for geothermal heat U, and the following values will change accordingly 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 underground, and a medium injection pipe 50 is connected to the outer side of the heat medium transfer pipe 10, which is in contact with the ground, and extends deep underground. A heat medium extraction pipe 80 is connected to the inner side of the medium injection pipe 50, and extends to the bottom of the medium injection pipe 50. These heat medium transfer pipes 10 are used as heat exchangers that absorb heat obtained from the geothermal heat field U. This pressurized water power generation plant A evaporates hot water and generates power through a steam turbine T. The power generation method using the pressurized water power generation plant 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 booster water 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 field U deep underground. The hot water transported to the geothermal heat field U at 210°C absorbs heat from the geothermal heat field U through the medium injection pipe 50, which has a high effective thermal conductivity, and finally becomes hot water (L2) at 200°C. 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 at 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 using the pressure control valve PV1, reducing the pressure to approximately 0.6 MPa and boiling it, separating the steam generated at a rate of 6 t / h with a flash rate of approximately 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 remaining hot water (L4), approximately 89% of which does not become steam, to the hot water service tank 4 at a flow rate of 49 t / h at a pressure of 0.6 MPa while maintaining a temperature of around 160°C.

[0057] Furthermore, 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 as hot water (L10) at 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. Furthermore, 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 around 130°C in the hot water service tank 4 is again pressurized to 6 MPa by the pressure 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 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 area 22, bounded by the dashed-dotted line, uses piping with excellent insulation properties, employing a material with an effective thermal conductivity of 0.1 W / m K or less for the medium injection pipe 50. The lower absorption area 26, bounded by the dashed-dotted line, uses piping with excellent heat absorption properties, employing a material with an effective thermal conductivity of 50 W / m K or more for the medium injection pipe 50.

[0059] Additionally, the heat transfer 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 this insulating effect, the hot water (L2) that has absorbed 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 state of water. Figure 9 shows the temperature and pressure as water changes from solid to liquid to gas. The solid line from the triple point to the critical point represents the evaporation curve 27. The boiling point at atmospheric pressure is 100°C, which corresponds to 0.101 MPa. Point C on the line is the boundary line where water changes from a gaseous state, or vapor, when the temperature is 200°C and the pressure is less than 1.554 MPa.

[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 water supply pump 3 is set in consideration of pressure loss.

[0062] In temperature distribution 21, the temperature increases as the temperature approaches the depth 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 has a temperature distribution 22 that rises 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 transfer 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 transfer medium extraction pipe 80 or the medium injection pipe 50. 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 down. The hot water heated above the boiling point in the geothermal 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 within the heat medium transfer pipe 10, which serves as a heat exchanger, and this generates buoyancy 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 water pump 3 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 underground heat can be effectively utilized by transferring hot water L3, which retains the heat absorbed in the geothermal heat field U, to the pressure control valve PV1 in a so-called single-phase flow state.

[0067] For these reasons, in this invention, 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, as shown by the shaded area in Figure 10. A material with an insulating performance of 0.05 W / m·K to 0.001 W / m·K is ideal. Maintaining insulating performance prevents a drop in temperature at the outlet, which has the advantage of eliminating the need to set the pressure of the booster feed pump 3 high. In Figure 14, the dashed line indicates the underground temperature distribution 21, including the geothermal zone U, and the solid line indicates the hot water temperature distribution 25.

[0068] Furthermore, taking into consideration the pressure loss in the medium injection pipe 50 and the heat medium extraction pipe 80, the outlet pressure of the hot water L3 is desirably set to a pressure range 23 that is at least greater than the evaporation curve 27 in Figure 9 by the pressurized water supply pump 3, and is set to a pressure that does not generate steam so that the hot water can be transported as is, even though its temperature is above the boiling point.

[0069] Furthermore, in the region of high underground temperature distribution, i.e., the heat absorption region 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. While a particularly high effective thermal conductivity is preferable, considering the pressure and corrosion underground, it is preferable to use a metallic material, and an effective thermal conductivity of 20 W / m K or higher 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 explained 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 in 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 the turbine T is returned to hot water in a condenser 6 and stored in the storage tank 11. The hot water L4 stored in the storage unit 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 facility TF supplies electricity to electric power companies, etc. via the power grid. The working medium M used here is a non-flammable, non-toxic inert gas such as HFC-245fa or R245fa, or a medium with a low boiling point (a mixture of water and ammonia, hydrocarbon (pentane)), etc.

[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 into a liquid or the like and sent again to the heat exchanger 152 by a circulation pump 155.

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

[0075] By using these working fluids (M1 to M3), it is possible to generate electricity even with hot water at 70 to 95 degrees Celsius, as long as the flow rate is 9 to 24 t / h. In this system, the medium exchanges 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 uses 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, and electricity may be generated by the binary power generation device B. In this case, 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 the 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 description will be omitted. The binary power generation system C will be explained with reference to Figure 13. The binary power generation system 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 system 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 in 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. The working fluids M (M1 to M23) used here include non-flammable, non-toxic inert gases such as HFC-245fa and R245fa, and low-boiling-point media (such as mixtures of water and ammonia, or hydrocarbons (pentane)). In this embodiment, the working fluids (M1 to M3) used in the binary power generation system C are two types of working fluids with different boiling point ranges: one with a high-temperature boiling point range and the other with a boiling point lower than the working fluids (M1 to M3). This enables multi-stage heat utilization, resulting in efficient power generation.

[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 gas state into 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 electricity is generated 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 into a liquid or the like and sent again to the second heat exchanger 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 plant 1c and exchanging heat, the raw water 16 is heated and the cooling water 157c, 158c is cooled, thereby achieving 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 condensing unit 17.

[0083] The method for cooling the working medium or medium such as water connected to the heat exchanger or condenser described above does not need to be limited to these, and various methods are possible, such as a cooling method using a heat exchange method that utilizes a Peltier element.

[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 those 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. Because the geothermal power generation system 100 does not have a steam-water separator F, geothermal heat is absorbed by the hot water and used directly, reducing losses 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, which then generates electricity using the generator G2. The power receiving facility TF supplies electricity to power companies, etc. via the power grid. Here, the working fluids M1, M2, and M3 used are non-flammable, non-toxic inert gases such as HFC-245fa and R245fa, or low-boiling-point media (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 into a liquid or the like and sent again to the heat exchanger 152 by a circulation pump 155.

[0088] By using these working media (M1 to M3), the geothermal power generation system 100 can generate power even with hot water at 70 to 95°C, as long as the flow rate is 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 in the heat exchanger 152, and is needed, along with the pressurized water supply pump 3, as an element for maintaining a constant pressure in the entire system of the pressurized water heat exchanger 1a. In particular, if the pressurized water supply pump 3 is stopped for maintenance or the like, the pressurized water heat exchanger 1a will experience an increase or decrease in water volume of approximately 2 tons of the total system capacity. Therefore, in order to maintain a constant water level and smoothly resume operation, the pressure in the service tank 4 can be controlled to maintain a constant water level.

[0090] (Fifth embodiment) A heat medium transfer pipe 500 and an installation method for the heat medium transfer pipe 500 according to the fifth embodiment will be described with reference to FIGS. 15 to 20. FIG. 15 is a longitudinal cross-sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, with a portion omitted. FIG. 16 is a longitudinal cross-sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, during installation. FIG. 17 is a longitudinal cross-sectional view of the heat medium transfer pipe 500 according to the fifth embodiment, during installation. FIG. 18 is a schematic diagram enlarging a portion of a pipe thread joint 51 of the heat medium transfer pipe 500 according to the fifth embodiment. FIG. 19 is a longitudinal cross-sectional view of a modified 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 and the temperature distribution of hot water in the geothermal power generation system according to the fifth embodiment. Note that the same reference numerals are used for the same parts as those in the first to fourth embodiments, and the above-mentioned 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 3,000 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 surrounded by the above-mentioned medium injection pipe 50, first protective pipe 31, second protective pipe 32, and third protective pipe 33. 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, and 1c (FIGS. 1 and 12 to 14) used in the first to fourth embodiments. The dashed line indicates the underground temperature distribution 21, and the solid lines indicate the temperature distributions of the hot water L1, L2, and L3 in the medium injection pipe 50 and the heat medium extraction pipe 80.

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

[0094] Furthermore, the heat transfer medium extraction pipe 80 uses piping with excellent thermal insulation, made of 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 this insulating effect, the hot water (L2) that has absorbed heat from the deepest geothermal heat 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 to third protective pipes 31 to 33 are located in the insulating region 22 and each have an insulating structure. The side walls are hardened with geothermal cement or the like while the excavator is used to dig deep into the ground, and the first to third protective pipes 31 to 33 prevent the side walls from collapsing during excavation. 15 and 18, the first protective pipe 31 is provided with a convection shielding 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 top of the disk-shaped hot water 74 and prevents blowout during construction, etc. The inner diameter of the convection shielding plate 73 is smaller than the outer diameter of the pipe thread joint 51, and is designed to prevent it from falling out upward due to 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 lower-temperature groundwater above due to convection and becoming lower-temperature water, thereby further improving the heat retention performance of the medium injection pipe 50. Therefore, by supporting the convection shielding disks 73 at multiple locations in the vertical direction, the heat medium transfer pipe 500 can further improve its heat retention performance. Note that the convection shielding disk 73 is not limited to being made of a material such as metal, resin, or rubber, and may be made of a cloth or the like that is laid around the medium injection pipe 50.

[0097] Next, the heat medium transfer pipe 500 has a thermal insulation structure constructed by a construction method described below 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, 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 absorption. 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 closed with concrete material are provided below.

[0098] The blocking portions 34 and 35 prevent water with a lower temperature than the medium injection pipe 50 from entering from below, thereby 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 entering from above.

[0099] Next, a method for installing the heat medium transfer pipe 500 of the present invention will be described with reference to FIGS. First, an excavation machine is used to excavate the largest diameter hole 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 as shown in Figure 16, and the third protective pipe 33 described above is buried.

[0100] 15 and 17, the diameter of the excavator is reduced and excavation is continued to a depth large enough to bury the second protective pipe 32 up to the 1500 m point. When the 700 m point is reached, a blocking section 34 is formed with concrete material across the entire lower diameter from 10 m to 100 m deep as shown in FIG. 17, 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 carried out to a depth large enough to bury the first protective pipe 31, and the excavation is continued to a position approximately 1700 m into the insulation area 22, where the above-mentioned first protective pipe 31 is buried.

[0101] Finally, as shown in Figure 15, the diameter of the excavator is further reduced and the excavation is performed to a size that allows the medium injection pipe 50 to be buried.The excavation is continued to a position approximately 3,000 m to the geothermal zone U of the desired temperature 210 in the heat absorption zone 26, and the above-mentioned medium injection pipe 50 and heat medium extraction pipe 80 are buried.

[0102] Here, the endothermic 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 drilling reaches the deepest point U, if the endothermic region 26 is the bedrock zone 38, as shown in FIG. 15 , water is filled between the bedrock zone 38 and the medium injection pipe 50 as a transfer promoting medium 39 to improve thermal conduction between the medium injection pipe 50 and the geothermal zone U. Water may be injected later, or the water used during hydraulic fracturing or mud drilling may be left as is and used.

[0103] 19, when the heat absorption region 26 is the fractured zone 43, a metal cup-shaped receiver pipe 75 may be inserted between the medium injection pipe 50 and the fractured zone 43 to receive water as the transfer promoting medium 39 because there are gaps between the fractured zones and no hot water. Then, to improve the heat 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 promoting medium 39. The transfer promoting medium 39 may not only be water, but also a liquid resin containing a metal that facilitates heat transfer.

[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 fractured zone 43 where heat transfer is poor.

[0105] 24 is a schematic diagram showing a portion of the lower part of the receiving pipe 75 shown in FIG. 19. The receiving pipe 75 has a medium movement hole 76, which is a through-hole that penetrates the side surface. The receiving pipe 75 has a hole so that the medium, such as hot water, can move through the medium movement hole 76 when the 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 transfer holes 76 may be holes formed in a mesh pattern using metal or the like. In this way, when the geothermal zone U contains hot water, it is preferable that the receiving pipe 75 has a structure that prevents rocks, sand, etc. from coming into contact with the medium injection pipe 50, making it 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 a sixth embodiment of the present invention will be described with reference to Figures 21 and 22. Figure 21 is a schematic diagram showing the configuration of a geothermal power generation system 400 according to the sixth embodiment of the present invention. Figure 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 Figure 21, the geothermal power generation system 400 is mainly composed of a pressurized water supply pump 3, multiple heat medium transfer pipes 410 (a to f), a hot water service tank 4, a condensing unit 17, a water supply unit 18, a steam 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 the medium injection pipe 50 at the deepest part of the ground, and the resulting hot water is heat exchanged and transported to the surface through the heat medium extraction pipe 80 while being pressurized. The transported hot water L3 is reduced in pressure by the pressure regulating valve PV1 and boiled, and then transported to the steam separator F.

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

[0110] Because 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, or drain, is sent from the steam-water separator F 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 a condenser 6. The sent steam V4 is condensed and returned to water, passes through the condenser 6, and is temporarily stored in a condensate tank 14 before being sent to the hot water service tank 4 by a 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 deep in the geothermal zone U and undergoes 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. In addition, in the present invention, a plurality of heat medium transfer pipes (410a to 410f) can also be applied to the power generation facilities such as binary power generation facilities A to B in the second to fifth embodiments described above.

[0112] As shown in Figure 21, the heat medium transfer pipe 410 is configured by installing a plurality of heat medium transfer pipes (410a to 410f) from the surface S to the geothermal zone U. With reference to Figure 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 promoting medium 39 drops due to reasons such as the heat from the geothermal heat zone U not being recovered near the medium injection pipe 50, 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 inside the heat medium transfer pipe 410f, a pressure pump 411 is provided to circulate the hot water L3 under pressure to prevent boiling. Furthermore, the geothermal power generation system 400 circulates the hot water L3 through the multiple heat medium transfer pipes 410 using the pressurized feed water pump 3 to apply pressure to prevent boiling even during normal power generation, but when one pressurized feed water pump 3 is not enough, the pressure pump 411 is used. The pressure pump 411 plays a role in regulating the pressure inside the heat medium transfer pipe 410f to maintain a constant pressure.

[0114] By applying pressure inside the heat transfer medium transfer pipe 410f to prevent boiling and circulating the hot water through the heat transfer medium transfer pipe 410f as a single-phase flow, it is possible to more effectively absorb heat from the geothermal heat zone U than when circulating the hot water through the heat transfer 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 equipped with a temperature sensor and a pressure sensor along the circulation path that measure the temperature and pressure of the hot water L3. Even when power generation is not being performed due to periodic maintenance or an unexpected drop in the temperature of the geothermal zone U caused by a natural disaster, etc., the heat medium transfer pipe 410f can circulate water, including the geothermal zone U, using the pressure control valve PV1 to make the temperature of the circulated hot water uniform, and therefore, by measuring with the circulation sensor unit 412 installed on the ground, it is possible to estimate the temperature state of the geothermal zone U even if the temperature in the geothermal zone U is unknown, and use this as an indicator 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 feature> A heat medium transfer pipe (e.g., mainly 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, is characterized in that the heat medium transfer pipe includes pipe joints (e.g., mainly pipe thread joints 51-55) that connect a plurality of the heat medium transfer pipes, and a heat medium insulation pipe (e.g., mainly insulation pipes 60-90) that continuously covers the pipe joints and a portion of the heat medium transfer pipe inside the heat medium transfer pipe and keeps the heat contained in the medium.

[0117] With the above features, the present invention not only improves the thermal insulation performance of the heat medium transfer pipe by the thermal insulation pipe, but also facilitates the replacement of the heat medium thermal insulation pipe itself and the installation of the heat medium transfer pipe.

[0118] <Second feature> The heat transfer medium insulation pipe is characterized by comprising an insertion pipe (e.g., mainly insertion pipes 61 and 91) to be inserted into the heat transfer medium transfer pipe, and a protrusion (e.g., mainly protrusions 62 and 92) having a diameter larger than the inner diameter of the heat transfer 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 threaded portion that threadably engages with the pipe joint when the heat medium transfer pipe is connected by 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 at least to the gripping portion. With the above features, the present invention improves the heat retention performance of the heat medium transfer pipe by using the heat medium insulation pipe of the connecting pipe without impairing the performance of the heat medium transfer pipe connection work. In addition, the heat medium transfer pipe can extract the medium from the ground without losing heat.

[0120] <Fourth feature> The heat medium transfer pipe comprises a medium injection pipe (e.g., mainly a medium injection pipe 50) that transfers the medium underground, and a medium extraction pipe (e.g., mainly a heat medium extraction pipe 80) that extracts the medium that has absorbed heat underground to the surface, and is characterized in that the medium injection pipe and the medium extraction pipe are equipped with the heat medium insulation pipe.

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

[0122] <Fifth feature> 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, an insulation area other than the absorption area where the medium absorbs the heat at the temperature required for power generation, for keeping the heat of the medium warm during transportation, a concrete insulation layer (e.g., mainly geothermal cement) that insulates the side walls of the excavated hole during excavation using cement that hardens the side walls, a second covering layer (e.g., mainly insulation 70) that is covered with an insulating material around the medium injection pipe and pipe joint, 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, making it possible to generate power by utilizing geothermal heat itself.

[0124] <Sixth feature> The heat medium transfer pipes are connected to each other by the pipe joints, and then the pipe joint covering part (for example, mainly the pipe thread joint covering part 93) is provided to cover the entire pipe joint from the outside. With the above-mentioned features, the heat medium transfer pipe can block heat transfer at the pipe joint by the pipe joint covering portion.

[0125] <Seventh feature> The heat medium transfer pipe (e.g., mainly the 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 plates 73) are provided at multiple locations in the vertical direction to block the vertical convection of groundwater that infiltrates between the heat medium transfer pipe and a tubular protective pipe (e.g., a third protective pipe 33) provided around the heat medium transfer pipe.

[0126] With the above features, the convection blocking section 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 feature> The convection shielding member is located below the pipe joint that connects the heat medium transfer pipe, and is annular in shape, with an inner diameter that is larger than the outer circumference of the medium transfer pipe and smaller than the outer diameter of the pipe joint. Due to the above-mentioned features, the present invention has a structure that does not allow the pipe to slip upward due to the water pressure of groundwater, etc., and also improves workability during installation.

[0128] <Ninth characteristic point> A heat medium transfer 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, a heat insulating layer (e.g., mainly foam concrete 36, 37) provided between the protective pipe and the other protective pipes, and a sealing layer (e.g., mainly blocking portions 34, 35) below the heat 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 feature> The heat insulating layer is characterized by being formed from a lightweight base material or concrete containing many air bubbles. With the above features, the present invention not only prevents water from entering, but also improves heat insulating performance by allowing the material to contain a large amount of air and the like.

[0131] <11th characteristic point> 9. The heat medium transfer pipe according to claim 8, wherein the sealing layer is made of concrete. With the above-mentioned features, the present invention can prevent water from entering 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> This geothermal power generation system comprises 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 comprises 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 system drives the switching valve and the pressure adjustment device to circulate the medium within the heat medium transfer pipes until the temperature of the medium recovers.

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

[0134] <13th characteristic point> A temperature measuring device (for example, mainly a circulation sensor unit 412 (temperature sensor)) for measuring the temperature of the medium is provided in the path for circulating 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 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 construction method for 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 has absorbed heat underground, includes a first sealing step of pouring cement (e.g., mainly cement, geothermal cement) into an excavated hole to form a first sealing layer (e.g., mainly a blocking portion 35) that seals the excavated 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 has stabilized, excavating a hole with a diameter smaller than that of the hole in the first sealing layer together with the first sealing layer, pouring cement into the excavated hole, and forming 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 in 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 third protective pipe embedding step.

[0136] With the above features, the present invention prevents the intrusion of water having a temperature lower than that of the hot water flowing into the heat medium transfer pipe from below, thereby improving the heat insulating 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. The method is characterized in that an insertion hole, which is a hole formed in a bedrock (e.g., mainly bedrock zone 38) present in a geothermal zone and has a larger diameter than the heat medium transfer pipes, is provided, a transfer promoting medium (e.g., mainly transfer promoting medium 39) and the heat medium transfer pipes are inserted into the insertion hole, and the heat from the geothermal zone is transferred to the heat medium transfer pipes via the transfer promoting medium.

[0138] With the above 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 feature> 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 is characterized by providing an insertion hole, which is a hole formed in a fractured zone (e.g., mainly fractured zone 43) present in the geothermal zone and has a larger diameter than the heat medium transfer pipes, and a medium container (receiving pipe 75) that is inserted into the insertion hole and contains a transfer promoting medium (e.g., mainly transfer promoting medium 39, water, oil, etc.), and inserting the medium container to transfer heat from the geothermal zone to the heat medium transfer pipes via the transfer promoting medium contained in the medium container.

[0140] With the above 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 has a plurality of through holes (e.g., mainly medium transfer holes 76), which 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-described 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...Grip portion, 60·90...heat insulation pipe, 61·91...insertion pipe, 62·92...protrusion, 73...convection shielding 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 section, T·T2·T3...Steam turbine, G...Generator, B...Binary power generation device, CT...Cooling tower, F...Steam separator, TF...Power receiving equipment, S...surface, U...geothermal zone.

Claims

[Claim 1] A geothermal power generation system equipped with an underground pipe used to utilize heat recovered on the ground, the system comprising: a heat medium transfer pipe that transports a medium underground and recovers the medium that has absorbed heat underground; a perforated pipe having holes on a side surface around the heat medium transfer pipe in a heat recovery area; an upper pipe that forms a plurality of thermal insulation structures in the area to be insulated; The geothermal power generation system is characterized in that the lower end of the upper pipe is sealed with concrete or cement to form a thermally insulated structure.

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