Embedded pipe

Abstract

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

Description

Technical Field

[0001] The present invention relates to a heat medium transfer pipe with enhanced heat insulation ability when recovering heat by a medium using a geothermal zone as a heat source and transferring the heat medium, and a geothermal power generation device and a buried pipe that generate electricity using the heat medium transfer pipe.

Background Art

[0002] Conventionally, in a geothermal power generation system, natural steam existing in a geothermal zone is taken out using natural pressure, and after gas-liquid separation, it is used. Therefore, the taken-out steam contains a large amount of sulfur and other impurities peculiar to the geothermal zone. These impurities form scale and adhere to heat wells, pipes, or turbine blades. When scale adheres, the power generation amount decreases over time, making long-term use difficult.

[0003] In Patent Document 1, in a binary power generation system, a closed-loop circulation flow path is configured in which a heat source fluid absorbs heat by heat exchange with geothermal fluid or geothermal heat, dissipates heat in an evaporator, and then refluxes for heat exchange with geothermal fluid or geothermal heat again. For the cooling fluid that cools the low-boiling medium, a closed-loop flow path for heat dissipation cooling to the ground is also configured, or a refrigerator and a heat exchanger are provided with the heat source fluid after passing through the evaporator as a driving heat source, and the temperature of the cooling fluid is controlled to optimize the condensation and liquefaction of the low-boiling medium in the condenser, and a closed-loop flow path for supplying the cooling fluid to the condenser is configured. A geothermal power generation system has been proposed.

[0004] Patent Document 2 discloses a general pipe screw joint used for a heat medium transfer pipe that efficiently recovers a heat medium, and is composed of a pin and a box each having a contact surface with a threaded portion and a non-threaded metal contact portion. The non-threaded metal contact portion has a seal surface and a shoulder surface. The shoulder surface of the pin is located at the end surface of the pin tip. There is a non-contact area where the pin and the box do not contact each other between the seal surface and the shoulder surface, and at least one shoulder surface of the pin and the box has at least one groove communicating with the non-contact area and the inside of the screw joint. A pipe screw joint is described.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0006] As described above, in the power generation method of pumping up and using hot spring water, scale adheres to the geothermal well, production well, and further equipment such as piping facilities and turbines, and over time, the power generation amount decreases. In addition, regular maintenance for removing scale is required. Also, from an environmental perspective, since hot spring water is pumped up and used, it is considered that it may affect the discharge amount of hot spring water. Further, the water after pumping up hot spring water and using it for power generation is returned to the ground from the reinjection well, but it contains chemical substances for removing scale and the impact on the environment is not negligible. Also, as seen in Patent Document 1, the method of generating electricity using only the underground heat is effective because there is no need to consider concerns about the amount of hot water in hot spring water and chemical substances, etc., which is beneficial for the environment.

[0007] In addition, in order to recover heat underground and transfer the obtained hot water to the ground, a heat medium transfer pipe is required. The heat medium transfer pipe depends on the temperature of the geothermal zone and requires a length of 1000 m to 3000 m. The heat medium transfer pipe is connected by pipe screw joints, and the heat medium transfer pipe extends deep underground. As seen in Patent Document 2, the pipe screw joints are strongly required to have pressure resistance and sealing performance under internal and external pressures and are firmly joined to the pipe.

[0008] However, the pipe threaded joint does not have a structure for enhancing the heat insulation performance. Near the ground surface where the temperature is low, heat transfer occurs between the inside and outside of the pipe, and there is a problem that the heat recovered from the ground is taken away. In addition, not only the pipe threaded joint, but also the transfer pipe that requires heat insulation becomes more difficult to have a heat insulation structure in terms of strength as the diameter increases, and the situation has become technically difficult. In addition, there has also been a demand for a technique to improve the workability of installation without deteriorating the heat insulation performance by providing a heat insulation structure. Therefore, in order to effectively utilize the heat medium obtained from the ground, a technique is required to transfer the heat medium to the separator or heat exchanger on the ground without the heat of the heat medium being taken away during the transfer of the heat medium while considering the work performance.

[0009] The present invention has been made in view of such problems, and in order to effectively utilize the heat obtained from the geothermal zone on the ground by a medium while improving workability, it prevents the intrusion of water at a lower temperature than the heat medium transfer pipe from below, improves the heat insulation performance of the heat medium transfer pipe, and provides a geothermal power generation device that effectively recovers heat in the region where heat is recovered.

Means for Solving the Problems

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

[0011] A heat medium transfer pipe that conveys a medium underground and recovers the medium that has absorbed heat underground A geothermal power generation device in which In the low-temperature region of the geothermal zone A plurality of protective pipes are provided around the heat medium transfer pipe, In the high-temperature region of the geothermal zone Around the heat medium transfer pipe, A receiving pipe provided with a plurality of holes on the side surface and open at the bottom It is characterized by being provided.

[0012] With the above characteristics, the sealing layer prevents the intrusion of water at a lower temperature than the heat medium transfer pipe from below and improves the heat insulation performance of the heat medium transfer pipe. Also, when the geothermal zone is covered with a fluid medium such as hot water, the medium such as hot water can move through the holes.

Brief Description of the Drawings

[0013]

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Embodiments for Carrying Out the Invention

[0014] Embodiments of the geothermal power generation systems 1, 100, 200, 300, 400 according to the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments and drawings described below are examples of a part of the embodiments of the present invention, and are not used for the purpose of limiting to these configurations, and can be appropriately changed without departing from the gist of the present invention. Corresponding components in each figure are denoted by the same or similar reference numerals.

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

[0016] The geothermal power generation system 1 mainly includes 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 gas-liquid separator F, a steam turbine T, a generator G, and a power receiving facility TF. The geothermal power generation system 1 exchanges heat with water as a medium supplied from the pressurized water supply pump 3 to the deepest part of the ground through the medium injection pipe 50, and transfers the heated water to the ground through the heat medium extraction pipe 80 while pressurizing it. The transferred hot water L3 is depressurized and boiled by a pressure regulating valve PV1 and transferred to the gas-liquid separator F. The gas-liquid separator F separates steam and hot water, and the generated steam V1 is supplied to the steam turbine T.

[0017] The geothermal power generation system 1 supplies the generated steam V1 to the steam turbine T, rotates the generator G to generate electricity, supplies electricity to the power receiving facility TF, and supplies electricity to an electric power company or the like via the power transmission network. The steam turbine T may be not only of a turbine type but also of a screw type or the like, as long as it can generate electricity by steam. The steam V1 supplied to the steam turbine T is depressurized and boiled from the hot water L3 and separated into hot water and steam by the gas-liquid separator F.

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

[0019] The hot water L8 in the hot water service tank 4 is transferred as hot water L1 to the heat medium transfer pipe 10 by the pressurized water supply pump 3. The hot water L1 transferred by the pressurized water supply pump 3 is heat-exchanged again by absorbing heat from the ground heat in the deep part with the geothermal zone U. The heat-exchanged hot water L2 is transferred by the pressurized water supply pump 3 through the heat medium transfer pipe 10 described later.

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

[0021] As shown in FIG. 10, the heat medium transfer pipe 10 is buried from the ground surface S to the geothermal zone U serving as a heat source in the deep part of the ground. A cylindrical medium injection pipe 50 is buried outside the heat medium transfer pipe 10, and the area around the medium injection pipe 50 from the ground surface S to before reaching the geothermal zone U, that is, the area with a temperature lower than the temperature required for power generation, is solidified with geothermal cement or the like and is made so as to have no risk of collapse. The heat medium transfer pipe 10 absorbs heat from the fluid or rock mass in the geothermal zone U located at the deepest part of the medium injection pipe 50 of the heat medium transfer pipe 10. The length of the heat medium transfer pipe 10 changes in total length depending on the temperature of the geothermal zone U and extends to the geothermal zone U where the flowing heat medium can be heated up to around 200°C.

[0022] The medium injection pipe 50 is made of materials such as steel or stainless steel. In the region U of the high-temperature geothermal zone, in order to increase the outer peripheral surface area of the medium injection pipe 50 and facilitate the transfer of the heat of the geothermal zone U, cylindrical fins with a circular cross-section are welded to it. In the region with a low temperature near the ground surface S, the medium injection pipe 50 has a heat insulation structure described later so that the heat of the hot water L1 pressurized and injected from the hot water service tank 4 is not taken away.

[0023] The heat medium transfer pipe 10 is provided with a cylindrical heat medium extraction pipe 80 inside the medium injection pipe 50 for transferring the water heated in the geothermal zone U. The heat medium extraction pipe 80 is formed in a cylindrical shape coaxially inside the medium injection pipe 50. The heat medium extraction pipe 80 has a cylindrical shape through which the hot water L3 can pass inside the pipe, and its outer side has a vacuum heat insulation structure or a structure with a heat insulating material attached along the vertical direction.

[0024] The heat medium transfer pipe 10 will be described in more detail with reference to FIGS. 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 FIGS. 2 to 7. FIG. 2 is a perspective view of the medium injection pipe 50 excluding the heat insulating material 70. The medium injection pipe 50 is composed of an injection pipe 40, a pipe screw joint 51, a heat preservation pipe 60 shown in FIG. 5, and a heat insulating material 70. The medium injection pipe 50 connects the injection pipe 40 with the pipe screw joint 51 to form a long tubular shape up to the deepest part U.

[0025] As shown in FIGS. 2 to 7, the injection pipe 40 forms a coating layer 46 that covers the periphery with a heat-resistant resin such as polyethylene, polypropylene, 6 nylon, 66 nylon, foamed urethane, or fluorine on the outermost surface except for the gripping portion 47. As shown in FIGS. 4 and 6, the injection tube 40 is provided with male screw portions 42 having screw grooves formed on the outer surfaces of both ends that are slightly tapered. In the drawings of FIGS. 4, 6, and 7, the female screw portion 52 and the male screw portion 42 are shown hatched. The gripping portion 47 is provided in a bare metal state for chucking the medium injection tube 50 and holding the tube screw joint 51 while controlling the torque during screwing or holding the medium injection tube 50 itself, and is a portion that does not constitute the coating layer 46. This is because providing the coating layer 46 may inhibit the gripping force.

[0026] Next, as shown in FIGS. 3, 4, 6, and 7, the tube screw joint 51 is provided with a female screw portion 52 having a screw groove formed inside so as to fit with the male screw portion 42. The tube screw joint 51 has a space in the center of its interior where no male screw portion 42 is formed, and a placement space portion 53 is provided as a space into which a protruding portion 62 described later is fitted.

[0027] Next, as shown in FIGS. 3 to 7, the heat insulation tube 60 has an insertion tube 61 formed of a heat-resistant resin such as polyimide, polyimide amide, 66 nylon, peak, polyamide, or fluorine, which is formed in a tubular shape with a total length of about 1200 mm. Further, in the center of the insertion tube 61, an annular protruding portion 62 having the same inner diameter as the outer diameter of the insertion tube 61 and formed of the same resin is joined by ultrasonic welding or the like. Thereby, the insertion tube 61 and the protruding portion 62 are integrally formed. Note that the heat insulation tube 60 may be integrally formed by molding, not limited to welding. The longitudinal length of the heat insulation tube 60 is formed so as to cover not only the gripping portion 47 but also a part of the covering portion 46, and is designed in consideration of the influence of heat transfer received by the tube screw joint 51 and the injection tube 40 from the outside.

[0028] Since the outer diameter of the protruding portion 62 is larger than the inner diameter of the injection tube 40, the heat insulation tube 60 does not fall inside the injection tube 40, and the protruding portion 62 stays in the placement space portion 53. Also, 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 inside the injection tube 40. Due to the above structure, for the connection of the medium injection pipe 50, after screwing in the pipe screw joint 51, the insertion pipe 61 of the heat preservation pipe 60 is inserted into the injection pipe 40, and then the other injection pipe 40 is screwed onto the pipe screw joint 51 from above for connection.

[0029] In this way, the connection of the medium injection pipe 50 is completed with simple operations. Also, the heat preservation pipe 60 not only improves the heat preservation performance of the medium injection pipe 50, but also makes it easy to replace the heat preservation pipe 60 itself and install the medium injection pipe 50. Further, the protruding part 62 is formed so that pressure is applied by the pressurized water pump 3 to prevent the hot water from boiling, and the protruding part 62 is held between the injection pipes 40 even when the hot water is pumped. Therefore, the heat preservation pipe 60 does not fall off. Since both ends of the heat preservation pipe 60 are held between the injection pipes 40, it does not fall off in the vertical direction. Similarly, the heat preservation pipe 60 does not fall off in the vertical direction for the heat medium extraction pipe 80 described later.

[0030] Next, referring to FIG. 4, the heat insulating material 70 provided around the medium injection pipe 50 will be described. The heat insulating material 70 is in close contact with the periphery of the medium injection pipe 50, and is provided with a heat insulating layer 71 formed of a material such as glass wool and a protective film portion 72 formed of a metal film such as aluminum on the outermost periphery. The medium injection pipe 50 has a heat insulation structure by the heat insulating material 70 and the coating layer 46 on the outer side of the pipe.

[0031] Next, referring to FIGS. 7 and 8, the heat medium extraction pipe 80 will be described. The heat medium extraction pipe 80 is provided for recovering the heat deep in the ground with hot water, transporting it to the ground, generating steam, and using the heat for steam power generation. For the heat medium extraction pipe 80, the description of the parts with exactly the same structure as the medium injection pipe 50 with reference to FIGS. 2 to 6 will be omitted, and the different parts 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 screw joint 55, and a heat preservation pipe 90.

[0032] The extraction pipe 81 corresponds to the structure of the injection pipe 40, the pipe screw joint 55 corresponds to the structure of the pipe screw joint 51, the placement space part 57 corresponds to the structure of the placement space part 53, the male screw part 82 corresponds to the structure of the male screw part 42, the female screw part 56 corresponds to the structure of the female screw part 52, the heat insulation pipe 90 corresponds to the structure of the heat insulation pipe 60, the coating layer 86 corresponds to the structure of the coating layer 46, the gripping part 87 corresponds to the structure of the gripping part 47, and the protruding part 92 corresponds to the structure of the protruding part 62. The heat medium extraction pipe 80 is provided with a heat insulation part 85 forming a heat insulation layer in which an air layer or a heat insulating material serving as a space is embedded along the longitudinal direction. The heat medium extraction pipe 80 has a heat insulation structure by the heat insulation pipe 60, preventing heat transfer.

[0033] In this way, the connection of the heat medium extraction pipe 80 is completed by a simple operation similar to the above-described medium injection pipe 50. Further, not only does the heat insulation performance of the heat medium extraction pipe 80 improve due to the heat insulation pipe 90, but also the operation of replacing the heat insulation pipe 90 itself and installing the heat medium extraction pipe 80 is easy. In addition to the fact that the heat medium extraction pipe 80 and the medium injection pipe 50 are also in a good heat insulation state due to the heat insulation pipe 60 and the heat insulation structure, the heat insulation state improves due to the heat insulation pipe 90, the heat insulation part 85, and the coating layer 86, and it is possible to extract the hot water L3 from the ground without being deprived of heat.

[0034] Next, the data will be described in an experiment showing the heat insulation performance of the present invention. FIG. 11(A) is a diagram schematically showing a conventional medium injection pipe 101. FIG. 11(B) is a diagram schematically showing the medium injection pipe 50 of the present invention. FIG. 11(B) shows the results of experimental data on the heat insulation performance of the conventional medium injection pipe 101 and the medium injection pipe 50 of the present invention. As shown in FIG. 11, the applicant measured the temperatures at each point (P1 to P8) as in a schematic diagram in order to compare the heat insulation performance between the medium injection pipe 50 of the present invention and the conventional medium injection pipe 101, and obtained a temperature gradient. A heater was inserted inside both pipes (101, 50), and the water heated by the heater and the outside of the pipe were filled with normal temperature water. Compared with the medium injection pipe 101, the medium injection pipe 50 is provided with the addition of the heat insulation pipe 60 and the coating layer 46.

[0035] As shown in Fig. 11(C), the measured temperature gradient is 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. This shows that there is a larger temperature difference in the medium injection pipe 50 of the present invention than in the conventional medium injection pipe 101, and it can be confirmed that the heat insulation performance is improved by the heat insulation pipe 60. Also, the temperature gradient between P3 and P4 of the conventional medium injection pipe 101 is 3420 °C / m, and the temperature gradient between P7 and P8 of the medium injection pipe 50 of the present invention is 9790 °C / m. This shows that there is a larger temperature difference in the medium injection pipe 50 of the present invention than in the conventional medium injection pipe 101, and it can be confirmed that the heat insulation performance is improved by the coating layer 46. As described above, the present invention can be provided with the heat medium transfer pipe 10 having improved heat insulation performance.

[0036] The hot water L3 heated in the geothermal zone U is depressurized and boiled by the pressure regulating valve PV1 to generate steam. Here, the gas-liquid separator F is connected to the pressure regulating valve PV1, and the nozzle for generating steam may use a nozzle capable of generating microbubbles and nanobubbles that become minute bubbles by self-aspiration. With this configuration, the steam generation efficiency can be improved, so even if the speed of transferring water is reduced, a sufficient amount of steam can be ensured. Therefore, the residence time of water in the heat absorption region of the geothermal zone U can be increased, and the time for water to absorb heat can be taken to obtain high-temperature hot water.

[0037] As another modification for improving the heat insulation performance, another embodiment of the heat medium extraction pipe 80 will be described with reference to Fig. 23. Fig. 23 is a longitudinal sectional view showing a modification of the heat medium extraction pipe 80a according to the first embodiment. The same reference numerals are given to the same parts as those in the above-described embodiment, and the above-described description will be omitted. The heat medium extraction pipe 80a is provided for recovering the heat deep in the ground with hot water, transporting it to the ground, generating steam with the pressure regulating valve PV1 (Fig. 1), and using 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 screw joint 55, and a heat insulation pipe 91.

[0038] The extraction pipe 81a has screw grooves provided on the outer circumference at both ends. Also, the pipe screw joint 55 has screw grooves provided on the inner circumference so as to fit with the screw grooves of the extraction pipe 81a. The extraction pipe 81a can be extended by fitting and connecting the extraction pipes 81a to each other with the pipe screw joint 55.

[0039] Also, as shown in Fig. 23, the heat insulation pipe 91 formed of a resin such as polyimide, polyimide amide, 66 nylon, peak, polyamide or fluorine is divided at the center of the pipe joint 55 and near the middle of the extraction pipe 81a, covering the entire length of the extraction pipe 81a. In this way, the heat medium extraction pipe 80a can transfer the heat medium to the ground while keeping the heat insulation state of the heat medium good at low cost without providing a heat insulation structure such as an air layer or a heat insulating material in the extraction pipe 81a by covering not only a part but also the entire length of the extraction pipe 81a with the heat insulation pipe 91.

[0040] The heat insulation pipe 91 has annular protrusions 92a, 92b formed of the same resin with the same inner diameter as the outer diameters of the heat insulation pipes 91a, 91b joined by ultrasonic welding or the like at the center of the heat insulation pipes 91a, 91b. Thereby, the heat insulation pipes 91a, 91b and the protrusions 92a, 92b are integrally formed. Note that the heat insulation pipe 91 may be integrally formed by molding, not limited to welding.

[0041] Since the outer diameters of the protrusions 92a, 92b are larger than the inner diameter of the extraction pipe 81a, the heat insulation pipe 91 does not fall inside the extraction pipe 81a and the protrusions 92a, 92b stay in the placement space portion 53. Also, since the outer diameter of the portion where the heat insulation pipe 91 is inserted is smaller than the inner diameter of the extraction pipe 81a, the heat insulation pipe 91 enters inside the extraction pipe 81a. With the above structure, for the connection of the extraction pipe 81a, after screwing the pipe screw joint 55, the heat insulation pipe 91 is inserted inside the extraction pipe 81a, and another extraction pipe 81a is screwed and connected to the pipe screw joint 55 from above.

[0042] In this way, the operation of connecting the heat medium extraction pipe 80a is completed with a simple operation. Also, although the pressurized water supply pump 3 applies pressure so that the hot water does not boil, the protruding portions 92a and 92b are formed so as to be held between the extraction pipes 81a even when the hot water is pumped. Therefore, the heat preservation pipe 91 will not fall off. As described above, since both ends of the heat preservation pipe 91 are held between the extraction pipes 81a, it will not fall off in the vertical direction.

[0043] Also, as shown in FIG. 23, for the portion of the pipe screw joint 55, after connecting the extraction pipe 81a with the pipe screw joint 51, a heat-shrinkable tube-shaped resin such as a polyolefin resin or a polypropylene resin, or a pipe screw joint coating portion 93 coated with a tape such as a polyolefin resin or a polypropylene resin is provided to provide a heat insulation structure for preventing heat transfer. With the above structure, the heat medium extraction pipe 80a blocks the heat transfer at the portion of the pipe screw joint 55 by the pipe screw joint coating portion 93.

[0044] In this embodiment, water is used as the medium for heat exchange in the geothermal zone U. However, as the medium, oil, gas (inert gas (nitrogen, carbon dioxide, etc.)) or a medium with a lower boiling point than the water used in binary power generation (a mixture of water and ammonia, etc.) can be considered. Also, when water or an inert gas is used as the medium, even if there is damage to the heat medium transfer pipe 10 and it flows out externally, water or an inert gas will not harm the environment and can be safely handled on the work surface.

[0045] (Gas-liquid separator) The moisture separator F shown in Fig. 1 is a cylindrical pressure vessel. The nozzle provided inside the moisture separator F ejects hot water L3 from its tip, separating steam V1 and hot water L4 inside the vessel. Also, a pressure regulating valve PV1 for adjusting the pressure (steam generation amount) is provided either inside or outside the moisture separator F. Further, a pressure regulating valve PV2 is provided in the passage leading to the hot water service tank 4 for collecting drain L4. It can adjust the steam pressure from the moisture separator F to the turbine T and can also be utilized to control the amount of steam flowing from the moisture separator F to the turbine T.

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

[0047] (Water supply unit) The water supply unit 18 generates soft water from raw water 16 such as river water or tap water using an industrial soft water generation device 9. Then, the generated soft water is stored in the makeup water tank 8. The stored soft water removes dissolved oxygen by using a deoxidation device or a deoxidant.

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

[0049] In addition, typical examples of deoxidizers include various substances such as hydrazine, tannin, or products derived from plants. There are also deoxidation devices that utilize inert gases, and inert gases that are less likely to cause chemical reactions are employed. Examples of inert gases include nitrogen and argon, which are less harmful. Particularly as in the present invention, since it is necessary to control the pressure of the medium for heat exchange at high temperatures, deoxidizers and deoxidation devices that do not cause changes in the physical properties of the working fluid are preferred. Nitrogen and the like are easily dissolved in water using a microbubble generator, and then, by injecting the dissolved water, substitution with oxygen becomes likely to occur.

[0050] During normal operation, since the temperature of the deaerated water L7 is low, the water supply unit 18 does not directly supply the insufficient water to the hot water service tank 4 with a high temperature, but replenishes the water via the condensate unit 18. Also, when cooling the condensate unit 18, it is possible to use the raw water 16 for cooling.

[0051] (Condensate unit) Next, the condensate unit 17 will be described. The condensate unit 17 has a function of condensing the steam V3 exhausted from the turbine T and returning it to 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 by the cooling tower CT, condensed, and returned to hot water L10, and is stored in the condensate tank 14 via the condenser 6. The stored hot water L6 is sent to the hot water service tank 4 by the condensate pump 5 and stored in the hot water service tank 4. Note that the cooling method by the cooling tower CT includes an air-cooled type, a water-cooled type using river water or seawater, or a ground heat exchange type that performs heat exchange underground.

[0052] (Power generation method using the above system) Referring to FIGS. 1, 9, and 10 to explain the power generation method, the depth of the hole drilled by boring to obtain steam at around 200°C on the ground reaches a depth of about 700 m to 2000 m to 3000 m underground. It is considered that the higher the depth, the higher the temperature can be obtained. However, it is determined in consideration of the excavation cost. The geothermal zone U is most suitable with a temperature of 200°C to 300°C, and the following values also change appropriately depending on the temperature obtained from near the deepest part of the geothermal zone U.

[0053] First, to explain the power generation method of the geothermal power generation system 1, a heat medium transfer pipe 10 is buried underground. The heat medium transfer pipe 10 is connected to a medium injection pipe 50 on the outside in contact with the ground and reaches deep underground. Further, a heat medium extraction pipe 80 is connected inside the medium injection pipe 50 and reaches the bottom of the medium injection pipe 50. These heat medium transfer pipes 10 are used as a heat exchange part for absorbing heat obtained from the geothermal zone U. This pressurized water power generation device A evaporates hot water and generates electricity via a steam turbine T. The power generation method by the pressurized water power generation device A will be described in detail below.

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

[0055] The gas-liquid separator F releases the pressure of the hot water (L3) at a temperature of 200°C by a pressure control valve PV1, depressurizes and boils it to about 0.6 MPa, and separates steam with a steam generation amount of 6 t / h at a flash rate of about 11%. The gas-liquid separator F sends the generated steam (V1) to the steam turbine T. The generated steam (V1) merges with the steam (V2) generated in the hot water service tank 4 in the steam-water separator F. The combined steam (V1+V2) drives the generator G to generate electricity by rotating the steam turbine T. When the efficiency is 80%, the generated power by this steam (V1+V2) can obtain an output of approximately 112 kWh.

[0056] Also, the steam-water separator F connected to the hot water service tank 4 by piping sends the remaining approximately 89% of the hot water (L4) that has not become steam back to the hot water service tank 4 at a flow rate of 49 t / h with a pressure of 0.6 MPa while maintaining a temperature of around 160°C.

[0057] Also, the steam (V3) exhausted from the steam turbine T is sent to the condenser 6. The steam (V4) sent to the condenser 6 is sent to an air-cooled or water-cooled cooling tower CT, and is condensed by the cooling tower CT and returned to hot water (L10) at 100°C with a pressure of 0.101 MPa. The returned hot water (L10) is stored in the condensate tank 14 at a flow rate of 6 t / h. Also, the hot water (L6) in the condensate tank 14 is sent to the hot water service tank 4 by the condensate pump 5. Then, the hot water (L1) at around 130°C in the hot water service tank 4 is pressurized again to 6 MPa by the pressurized feed 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 is transferred to the geothermal zone U deep underground.

[0058] Figure 10 is a diagram showing the relationship between the depth of the heat medium transfer pipe 10 of the pressurized water power generation device 1 and the temperature distribution of the hot water. The dashed line indicates the temperature distribution 21 in the ground, and the solid line indicates the temperature distribution of the hot water L1, L2, and L3 in the medium injection pipe 50 and the heat medium extraction pipe 80. With the dashed-dotted line as the boundary, the upper adiabatic region 22 uses a pipe with excellent heat insulation effect by adopting a material with an effective thermal conductivity of 0.1 W / m·K or less for the medium injection pipe 50. Also, with the dashed-dotted line as the boundary, the lower absorption region 26 uses a pipe with excellent heat absorption by adopting a material with an effective thermal conductivity of 50 W / m·K or more for the medium injection pipe 50.

[0059] In addition, the heat medium extraction pipe 80 uses a pipe with excellent heat insulation effect that employs a material with an effective thermal conductivity of 0.1 W / m·K or less regardless of the heat insulation region 22 and the heat absorption region 26. Due to the heat insulation effect, it is not affected by the temperature change in the middle of the medium injection pipe 50, and the hot water (L2) that has absorbed the heat of the deepest geothermal zone U can be transferred to the pressure regulating valve PV1.

[0060] Figure 9 is a schematic diagram of the state change of water. In Figure 9, the temperature and pressure when water changes between solid, liquid, and gas are shown. The solid line from the triple point to the critical point indicates the evaporation curve 27. The boiling point at atmospheric pressure is 100 °C, which indicates 0.101 MPa. At point C on the line, when the temperature is 200 °C, if the pressure is less than 1.554 MPa, it is the boundary line where the state of water changes to gas, that is, steam.

[0061] At point D on the line, when the temperature is 210 °C, if the pressure is less than 1.907 MPa, it becomes the boundary line where the state of water changes to gas, that is, steam. In addition, the pressurized region 23 indicated by the diagonal lines represents the region where the hot water L3 does not become steam, and the pressurized water supply pump 3 sets the pressure value considering the pressure loss.

[0062] The temperature distribution 21 increases as it approaches the deep part of the geothermal zone U and reaches 220 °C. Since the effective thermal conductivities of the medium injection pipe 50 and the heat medium extraction pipe 80 employ a material with a thermal conductivity of 50 W / m·K, the temperature distribution 22 of the warm water (L1) guided to the medium injection pipe 50 increases along the underground temperature distribution 21.

[0063] Here, even if the effective thermal conductivity of the heat medium extraction pipe 80 is set as low as 0.1 W / m·K, if 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 decreases to approach the boiling point.

[0064] When the water changes to steam in the heat medium extraction pipe 80, it becomes a so-called gas-liquid two-phase flow, and the heat transfer coefficient becomes several tens of times that in the case of the single-phase flow of hot water. Therefore, heat is easily taken away from the low-temperature downflow L1 flowing through the heat medium extraction pipe 80 or the medium injection pipe 50. In order to prevent such heat loss and transfer the energy while storing it, it is necessary to make the hot water difficult to cool down. Then, the hot water above the boiling point heated in the geothermal zone U is transported to the steam-water separator F without cooling, thereby reducing heat loss. In order to reduce heat loss, it is necessary to maintain a pressure higher than the evaporation curve 27 of FIG. 13 as described above.

[0065] In particular, a temperature difference occurs in the heat medium transfer pipe 10 serving as a heat exchanger, and accordingly, a buoyancy force caused by the density difference of water is generated. The pressurized water supply pump 3 does not have enough pressure to transfer the required flow rate only by natural circulation by the buoyancy force alone, and the pressure losses of the medium injection pipe 50 and the heat medium extraction pipe 80 must be considered.

[0066] Also, it is important for the pressurized water supply pump 3 to maintain the pressure at a high level by the pressurized water supply pump 3 in order to maintain a pressure higher than the evaporation curve 27 and keep the heat medium from boiling in the heat medium transfer pipe 10. Transferring the hot water L3 that has retained the amount of heat absorbed in the geothermal zone U, that is, in the so-called single-phase flow state, to the pressure regulating valve PV1 is an advantage of the present invention that enables effective use of underground heat.

[0067] From the above, in the present invention, as shown in the shading of FIG. 10, the heat insulation regions of the medium injection pipe 50 and the heat medium extraction pipe 80 are formed of a material having an effective thermal conductivity of 0.1 W / m·K or less. Most preferably, it has a heat insulation performance of 0.05 W / m·K to 0.001 W / m·K. By maintaining the heat insulation performance, it is possible to prevent the temperature drop at the outlet, and as a result, it is not necessary to set the pressure of the pressurized water supply pump 3 high. In FIG. 14, the broken line shows the temperature distribution 21 in the ground including the geothermal zone U, and the solid line shows the temperature distribution 25 of the hot water.

[0068] Further, the outlet pressure of the hot water L3 is desirably in a pressure range 23 that is at least greater than the evaporation curve 27 in FIG. 9 by the pressurizing feed water pump 3 in consideration of the pressure losses of the medium injection pipe 50 and the heat medium extraction pipe 80, and is set to a pressure that does not generate steam so that the hot water with a temperature above the boiling point can be transferred as it is.

[0069] Furthermore, in the region with a high temperature distribution in the ground, that is, the heat absorption region necessary for power generation, the medium injection pipe 50 is formed of a material with a high effective thermal conductivity of 50 W / m·K. Although the higher the effective thermal conductivity, the better, considering the pressure and corrosion in the ground, it is desirable to form it of a metal material, and the effective thermal conductivity may be 20 W / m·K or more.

[0070] (Second Embodiment) The geothermal power generation system 200 according to the second embodiment will be described with reference to FIG. 12. FIG. 12 is a schematic diagram showing the configuration of the geothermal power generation system 200 of the present invention according to the second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and the above-described description will be omitted. The binary power generation device B will be described with reference to FIG. 12. The binary power generation device B mainly includes a heat exchange unit 150 connected to the pressurized water power generation device 1b, a steam turbine T2, a generator G2, a power receiving facility TF2, a cooler 154, and a circulation pump 155.

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

[0072] The working medium M1 heated in this heat exchange unit 150 evaporates and rotates the steam turbine T2, and the generator G2 generates electricity by this rotation. The power receiving equipment TF supplies electricity and supplies electricity to a power company or the like via a power transmission network. Here, as the working medium M, non-flammable and non-toxic inert gases such as HFC-245fa and R245fa, and media with low boiling points (such as a mixture of water and ammonia, hydrocarbons (pentane), etc.) are used.

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

[0074] The cooling water 157b and 158b are piped to the raw water 16 provided in the water supply unit 18 of the pressurized water power generation device 1b and heat exchange is performed. As a result, the raw water 16 is heated and the cooling water 157b and 158b are cooled, so that effective heat replacement is performed throughout the geothermal power generation system 200. The raw water 16 can be directly introduced into the hot water service tank 4 without passing through the condensate unit 17 after being heated.

[0075] By using such a working medium (M1 to M3), power generation is possible as long as the flow rate is 9 t / h to 24 t / h even for hot water at 70°C to 95°C. In this system, it is a system that performs heat exchange in a closed system of the medium.

[0076] Since the working medium (M1 to M3) can be determined according to the heat exchange temperature, there may be cases where the temperature is limited by the binary power generation device B. Even in such cases, the pressurized water power generation device 1b is provided with a temperature adjustment system 161 that uses the air-cooled tower CT of the condensate unit 17 so as to be able to cope. In particular, when the temperature of the drain L4 that has not become steam is high, it is possible to lower the temperature to a region that matches the set temperature of the binary power generation device B.

[0077] It is also possible to have a structure in which the hot water L3 sent from the heat medium transfer pipe 10 is directly supplied to the heat exchanger 151 and electricity is generated by the binary power generation device B. When the temperature of the geothermal well at the deepest part U is low, it is possible to efficiently utilize the underground heat for power generation.

[0078] (Third Embodiment) The 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 the geothermal power generation system 300 of the present invention according to the third embodiment. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and the above-described description will be omitted. Referring to FIG. 13 to describe the binary power generation device C, the binary power generation device C includes a first heat exchange part 150c connected to the pressurized water power generation device 1b, a second heat exchange part 156c, a steam turbine T2, a steam turbine T3, a generator G2, a generator G3, a power receiving facility TF2, a cooler 164c, a first circulation pump 155c, and a second circulation pump 165c.

[0079] In the present invention, the steam is separated from the hot water L3 obtained from the heat medium transfer pipe 10 provided in the pressurized water power generation device 1c by the gas-liquid separator F, and the drain L4 that has not become steam is passed through the first heat exchanger 151c. The working medium M1 heated at this first heat exchange part 150c evaporates and rotates the steam turbine T2, and power generation is performed by the generator G2.

[0080] The power receiving facility TF2 supplies electricity and supplies electricity to an electric power company or the like via the power transmission network. Here, as the working medium M (M1 to M23), inert gases such as HFC-245fa and R245fa that are not flammable or toxic, and media with low boiling points (such as a mixture of water and ammonia, hydrocarbons (pentane)) are used. Further, in this embodiment, by using two types of working media having boiling point regions, namely, a working medium having a high-temperature boiling point region and a working medium having a lower boiling point than the working medium (M1 to M3) (M21 to M23) for the binary power generation device C, heat utilization in multiple stages becomes possible, and power generation can be performed efficiently.

[0081] Steam turbines T2 and T3 use expansion turbines and the like. The working medium M2 that has passed through the steam turbine T2 is heat-exchanged and cooled by the second heat exchanger 153c of the second heat exchange section 154c. Further, the working medium M3 is condensed from a gas to a liquid or the like and sent again to the heat exchanger 152c by the circulation pump 155c. Also, 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 power generation is performed by the generator G3.

[0082] The working medium M21 that has passed through the steam turbine T3 is cooled by the cooling water 157c and 158c of the cooler 164c. Further, the working medium M23 is condensed from a gas to a liquid or the like and sent again to the second heat exchange section 154c by the circulation pump 165c. The cooling water 157c and 158c are piped to the raw water 16 provided in the water supply unit 18 of the pressurized water power generation device 1c and heat-exchanged, so that the raw water 16 is warmed and the cooling water 157c and 158c are cooled, and effective heat replacement is performed throughout the geothermal power generation system 300. The raw water 16 can be directly introduced into the hot water service tank 4 without passing through the condensate unit 17 when it is warmed.

[0083] Note that the method of cooling media such as the working medium or water connected to the heat exchanger and the condenser described above is not necessarily limited to these, and various methods such as a method of cooling by a heat exchange method using a Peltier element can be considered.

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

[0085] The geothermal power generation system 100 passes the pressurized hot water L3 from the medium transfer pipe 10 provided in the pressurized water heat exchanger 1a through the heat exchanger 151 as hot water without turning it into steam. Since the geothermal power generation system 100 does not have a gas-liquid separator F in this way, it can reduce losses by directly absorbing underground heat with hot water and recovering the underground heat for power generation.

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

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

[0088] The geothermal power generation system 100 can generate power if it has a flow rate of 9 t / h to 24 t / h even with hot water at 70°C to 95°C by using such working media (M1 to M3). In this system, it is a system in which the working media perform heat exchange in a closed system.

[0089] In addition, the service tank 4 provided in the pressurized water heat exchanger 1a stores the hot water cooled by the heat exchanger 152, and is required to be arranged together with the pressurized water supply pump 3 as an element for keeping the pressure of the entire system of the pressurized water heat exchanger 1a constant. In particular, when the pressurized water supply pump 3 stops due to maintenance or the like, in the pressurized water heat exchanger 1a, the level of water in the system will increase and decrease by about 2 tons. Therefore, in order to keep the water level constant and restart the operation smoothly, the pressure of the service tank 4 can be controlled to keep the water level constant.

[0090] (Fifth Embodiment) The heat medium transfer pipe 500 according to the fifth embodiment and the construction method of the heat medium transfer pipe 500 will be described with reference to FIGS. 15 to 20. FIG. 15 is a longitudinal sectional view omitting a part of the heat medium transfer pipe 500 of the present invention according to the fifth embodiment. FIG. 16 is a longitudinal sectional view during the construction of the heat medium transfer pipe 500 of the present invention according to the fifth embodiment. FIG. 17 is a longitudinal sectional view during the construction of the heat medium transfer pipe 500 of the present invention according to the fifth embodiment. FIG. 18 is a schematic enlarged view of a portion of the pipe screw joint 51 of the heat medium transfer pipe 500 of the present invention according to the fifth embodiment. FIG. 19 is a longitudinal sectional view omitting a part of the modified heat medium transfer pipe 500 of the present invention according to the fifth embodiment. FIG. 20 is a relational diagram showing the relationship between the depth of the heat medium transfer pipe 500 of the geothermal power generation system of the present invention according to the fifth embodiment and the temperature distribution of the hot water. The same parts as those in the first to fourth embodiments are denoted by the same reference numerals, and the above description will be omitted.

[0091] The heat medium transfer pipe 500 shown in FIG. 15 shows an example in which it extends from the ground surface S to the deepest depth of 3000 m up to the geothermal zone U. The heat medium transfer pipe 500 is provided with the above-described heat medium extraction pipe 80 at the center, and the above-described medium injection pipe 50, the first protection pipe 31, the second protection pipe 32, and the third protection pipe 33 are provided on its outer periphery. The first to third protection pipes are pipes in an annular shape extending toward the geothermal zone U.

[0092] As shown in FIG. 20, it is a relational diagram of the depth of the heat medium transfer pipe 500 applied to the pressurized water power generation devices 1, 1a, 1b, 1c (FIGS. 1 and 12 to 14) used in the first to fourth embodiments and the temperature distribution of the hot water. The broken line indicates the temperature distribution 21 in the ground, and the solid line indicates the temperature distribution of the hot water L1, L2, L3 in the medium injection pipe 50 and the heat medium extraction pipe 80.

[0093] With the dashed-dotted line as the boundary, in the upper heat insulation region 22, pipes with excellent heat insulation effects using materials with an effective thermal conductivity of 0.1 W / m·K or less for the medium injection pipe 50 are used. Also, with the dashed-dotted line as the boundary, in the lower absorption region 26, pipes with excellent heat absorption using materials with an effective thermal conductivity of 50 W / m·K or more for the medium injection pipe 50 are used.

[0094] In addition, the heat medium extraction pipe 80 uses pipes with excellent heat insulation effects using materials with an effective thermal conductivity of 0.1 W / m·K or less regardless of the heat insulation region 22 and the heat absorption region 26. Due to the heat insulation effect, it is not affected by the temperature change in the middle of the medium injection pipe 50, and the hot water (L2) that has absorbed the heat of the deepest geothermal zone U can be transferred to, for example, the pressure regulating valve PV1 in FIG. 1.

[0095] The first protective pipe 31 to the third protective pipe 33 are located in the heat insulation region 22 and each is provided with a heat insulation structure. While the side wall is solidified with geothermal cement or the like, it is dug deeper into the ground by an excavator, and the first protective pipe 31 to the third protective pipe 33 prevent the collapse of the side wall during excavation. As shown in FIGS. 15 and 18, the first protective pipe 31 shields the convection from above the disk-shaped hot water 74 below the pipe screw joint 51 that connects the injection pipes 40 of the medium injection pipe 50, and is provided with a convection shielding disk 73 (convection shielding means) that prevents blowout during construction or the like. The convection shielding plate 73 has an inner diameter smaller than the outer diameter of the pipe screw joint 51 and is structured so as not to escape upward due to the water pressure of groundwater or the like.

[0096] The convection shielding disk 73 prevents hot water that has entered from below the gap between the medium injection pipe 50 and the first protective pipe 31 from mixing with the cooler groundwater above through convection and turning into cooler water, thereby further enhancing the heat insulation performance of the medium injection pipe 50. Therefore, the heat medium transfer pipe 500 can further enhance its heat insulation performance by receiving the convection shielding disk 73 at multiple locations in the vertical direction. Note that the convection shielding disk 73 is not limited to materials such as metal, resin, or rubber, and may have a structure in which a cloth or the like is spread around the medium injection pipe 50.

[0097] Next, the heat medium transfer pipe 500 is provided with a heat insulation structure constructed by the construction method described later between the first protective pipe 31 and the second protective pipe 32 and between the second protective pipe 32 and the third protective pipe 33. The heat medium transfer pipe 500 uses lightweight aggregates such as expanded polystyrene or concrete with a large amount of air bubbles mixed 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 form a heat insulation structure with cushioning, heat insulation, and non-water-absorbing properties. 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, there are provided blocking portions 34, 35 blocked by a concrete material at the bottom.

[0098] The blocking portions 34, 35 prevent the intrusion of water with a lower temperature than the medium injection pipe 50 from below, and improve the heat insulation performance of the heat medium transfer pipe 500. Note that the upper part of the heat medium transfer pipe 500 is also blocked by concrete or steel materials (not shown) to prevent the intrusion of water from above.

[0099] Next, with reference to FIGS. 15 to 17, the construction method of the heat medium transfer pipe 500 of the present invention will be described. First, use an excavating machine to excavate to the 700 m point with the largest diameter. During excavation, advance while solidifying the side wall with geothermal cement or the like so that collapse does not occur. When reaching the 700 m point, as shown in FIG. 16, form a blocking portion 35 filled with a concrete material in the section from a depth of 10 m to 100 m, and bury the above-described third protective pipe 33.

[0100] Next, as shown in FIGS. 15 and 17, the diameter of the excavator is reduced, and excavation is carried out to a size such that the second protective pipe 32 can be buried, and excavation is advanced to the 1500 m point. When the 700 m point is reached, as shown in FIG. 17, a closing portion 34 is formed of a concrete material in the section from a depth of 10 m to 100 m with the full diameter at the lower side, and the above-described second protective pipe 32 is buried. Next, as shown in FIG. 15, the diameter of the excavator is further reduced, and excavation is carried out to a size such that the first protective pipe 31 can be buried, and excavation is advanced to a position around 1700 m in the heat insulation region 22, and the above-described first protective pipe 31 is buried.

[0101] Finally, as shown in FIG. 15, the diameter of the excavator is further reduced, and excavation is carried out to a size such that the medium injection pipe 50 can be buried, and excavation is advanced to a position around about 3000 m up to the geothermal zone U at a desired temperature of 210 in the heat absorption region 26, and the above-described medium injection pipe 50 and the heat medium extraction pipe 80 are buried.

[0102] Here, in the heat absorption region 26, hot water does not necessarily exist sufficiently, and a rock mass zone 38 or a fractured zone 43 is also conceivable. After the excavation reaches the deepest part U, as shown in FIG. 15, when the heat absorption region 26 is the rock mass zone 38, in order to improve the heat conduction between the medium injection pipe 50 and the geothermal zone U, water is filled as a heat transfer promoting medium 39 between the rock mass zone 38 and the medium injection pipe 50. Water may be injected later, or a method may be used in which the water used at the time of hydraulic fracturing or muddy water excavation is left as it is and used.

[0103] In addition, as shown in FIG. 19, when the heat absorption region 26 is the fractured zone 43, in the case of the heat medium transfer pipe 500, since there are voids between the fractured zones and there is no hot water, a metal cup-shaped receiving pipe 75 for receiving water as the heat transfer promoting medium 39 may be inserted between the medium injection pipe 50 and the fractured zone 43. Then, in order to improve the heat conduction between the receiving pipe 75 and the medium injection pipe 50, water is filled as the heat transfer promoting medium 39 between the receiving pipe 75 and the medium injection pipe 50. Note that the heat transfer promoting medium 39 may be not only water but also a liquid resin containing a metal that easily transfers heat as a medium.

[0104] As described above, in the present invention, even if the geothermal zone U in the heat absorption region 26 is a rock formation zone 38 or a fracture zone 43 with poor heat transfer, an intervening substance is interposed between the heat medium transfer pipe 500 and the geothermal zone U, and it is possible to efficiently absorb the heat of the geothermal zone U.

[0105] In addition, the receiving pipe 75 shown in FIG. 24 is a schematic view showing a part below the receiving pipe 75 shown in FIG. 19. The receiving pipe 75 is provided with a medium moving hole 76 which is a through hole penetrating the side surface. The receiving pipe 75 is provided with a hole so that a medium such as hot water can move through the medium moving 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 the collapse of rock or the like, and prevents rock or the like from entering the region where the side wall of the medium injection pipe 50 contacts the medium such as hot water. Note that the medium moving hole 76 may be a hole formed in a net shape using metal or the like. In this way, it is preferable for the receiving pipe 75 to adopt a structure that does not allow rock, sand, or the like to contact the medium injection pipe 50 when the geothermal zone U is hot water, and it is possible to secure a region where a fluid such as hot water contacts the medium injection pipe 50.

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

[0108] As shown in FIG. 21, the geothermal power generation system 400 mainly includes a pressurized water supply pump 3, a plurality of heat medium transfer pipes 410 (a to f), a hot water service tank 4, a condensate unit 17, a water supply unit 18, a gas-liquid separator F, a steam turbine T, a generator G, and a power receiving facility TF. The geothermal power generation system 400 exchanges heat with water as the medium supplied by the pressurized water supply pump 3 through the medium injection pipe 50 at the deepest part of the ground, and transfers the heated water to the ground through the heat medium extraction pipe 80 while pressurizing it. The transferred hot water L3 is depressurized and boiled by the pressure regulating valve PV1 and transferred to the steam-water separator F.

[0109] In the steam-water separator F, steam and hot water are separated, and the generated steam V1 is supplied to the steam turbine T. The geothermal power generation system 400 supplies the generated steam V1 to the steam turbine T, rotates the generator G to generate electricity, supplies electricity to the power receiving facility TF, and supplies electricity to power companies and the like through the power transmission network. The steam turbine T may be not only of the turbine type but also of the screw type or the like, as long as it can generate electricity by steam.

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

[0111] The hot water L8 in the hot water service tank 4 is transferred to the heat medium transfer pipe 410 as hot water L1 by the pressurized water supply pump 3. The hot water L1 transferred by the pressurized water supply pump 3 absorbs heat from the geothermal heat again in the deep part with 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 described later. In addition, the present invention can also be applied to power generation facilities such as the A-to-B binary of Examples 2 to 5 described above with a plurality of heat medium transfer pipes (410a to 410f).

[0112] As shown in FIG. 21, a plurality of heat medium transfer pipes (410a to 410f) of the heat medium transfer pipe 410 are installed from the ground surface S to the geothermal zone U. Referring to FIG. 22, the heat medium transfer pipe 410f will be described as a representative example of the heat medium transfer pipes 410 (410a to 410f). The geothermal power generation system 400 absorbs the underground heat of the geothermal zone U through the medium injection pipe 50, exchanges heat with hot water (L2) as the heat medium, and transfers the hot water (L3) to the ground. However, when the temperature of the heat transfer promoting medium 39 decreases due to reasons such as the heat in the geothermal zone U near the medium injection pipe 50 not recovering, the flow path switching valves 413 and 414 provided on the ground side of the heat medium transfer pipe 410f are switched, and the water as the heat medium circulates in the heat medium transfer pipe 410f reaching the geothermal zone U.

[0113] When circulating the hot water L3 in the heat medium transfer pipe 410f, a pressure pump 411 is provided to apply pressure so as not to boil and circulate. Further, the geothermal power generation system 400 circulates the paths of the plurality of heat medium transfer pipes 410 by applying pressure by the pressurized water supply pump 3 so as not to boil even during normal power generation. When one pressurized water supply pump 3 is not sufficient, the pressure pump 411 is used. The pressure pump 411 serves to adjust the pressure so that the pressure in the heat medium transfer pipe 410f becomes constant.

[0114] By applying pressure in the heat medium transfer pipe 410f so as not to boil and circulating the hot water through the heat medium transfer pipe 410f in a single-phase flow, it is possible to effectively absorb heat from the geothermal zone U as compared with the case of circulating the hot water through the heat medium transfer pipe 410f in a gas-liquid two-phase flow.

[0115] The heat medium transfer pipe 410f is provided with a circulation sensor unit 412 that is provided with a temperature sensor and a pressure sensor for measuring the temperature and pressure of the hot water L3 in the middle of the circulation path. Even when power generation is not performed due to regular maintenance or an unexpected temperature drop in the geothermal zone U due to natural disasters or the like, the pressure regulating valve PV1 circulates water including the geothermal zone U so that the temperature of the hot water becomes uniform, and the temperature of the circulated hot water can be made uniform. Therefore, by measuring the circulation sensor unit 412 provided on the ground, even if the temperature in the geothermal zone U is unknown, it is possible to estimate the temperature state of the geothermal zone U and use it as an index for planning the power generation amount.

[0116] (Technical features considered from the above embodiment) An example of the technical feature points of the present embodiment is shown in parentheses below, but it is not particularly limited and is only an example, and the effects considered from these features are also described. <First feature point> A heat medium transfer pipe (for example, mainly the heat medium transfer pipes 10 (medium injection pipe 50, heat medium extraction pipe 80) 410·500) that conveys a medium (for example, mainly water, oil, etc.) into the ground and recovers the medium that absorbs heat in the ground, wherein the heat medium transfer pipe includes a pipe joint (for example, mainly the pipe screw joints 51·55) that connects a plurality of the provided heat medium transfer pipes, and a heat medium heat preservation pipe (for example, mainly the heat preservation pipes 60·90) that continuously covers the inside of the heat medium transfer pipe and a part of the heat medium transfer pipe to keep the heat held by the medium warm.

[0117] Due to the above features, the present invention not only improves the heat preservation performance of the heat medium transfer pipe by the heat preservation pipe, but also facilitates the replacement of the heat medium heat preservation pipe itself and the installation work of the heat medium transfer pipe.

[0118] <Second feature point> The heat medium heat preservation pipe is characterized by including an insertion pipe (for example, mainly the insertion pipes 61·91) that is inserted into the inside of the heat medium transfer pipe, and a protruding portion (for example, mainly the protruding portions 62·92) that has a diameter larger than the inner diameter of the heat medium transfer pipe and is held inside the pipe joint. Due to the above features, the present invention facilitates the replacement of the heat medium heat preservation pipe itself and the installation work of the heat medium transfer pipe.

[0119] <The third feature point> The heat medium transfer pipe is provided near a screwing portion that screws and connects with the pipe joint when the heat medium transfer pipe is connected by the pipe joint. The heat medium transfer pipe includes a gripping portion (for example, mainly gripping portions 47 and 87) for gripping the heat medium transfer pipe, and a coating layer (for example, mainly coating layers 46 and 86) coated with a heat insulating material provided avoiding the gripping portion. The heat medium heat preservation pipe is characterized by including the insertion pipe that extends at least to the portion of the gripping portion. Due to the above features, the present invention improves the heat preservation performance of the heat medium transfer pipe by the heat medium heat preservation pipe of the connecting pipe without impairing the performance of the connection work of the heat medium transfer pipe. Also, the heat medium transfer pipe can take out the medium from the ground without being deprived of heat.

[0120] <The fourth feature point> The heat medium transfer pipe includes a medium injection pipe (for example, mainly medium injection pipe 50) for transferring the medium into the ground, and a medium extraction pipe (for example, mainly heat medium extraction pipe 80) for taking out the medium that has absorbed heat from the ground to the ground. The heat medium heat preservation pipe is provided on the medium injection pipe and the medium extraction pipe.

[0121] Due to the above features, the present invention improves the heat preservation performance of the medium injection pipe and the heat medium transfer pipe by the heat medium heat preservation pipe. The heat medium transfer pipe can take out the medium from the ground by the medium extraction pipe without being deprived of heat.

[0122] <The fifth feature point> A generator that generates electricity using the heat of the medium taken out on the ground (for example, mainly generator G or binary generator B), and an insulation region that is outside the absorption region where the medium absorbs heat at the temperature required for power generation and that insulates the heat of the medium during transfer. A concrete insulation layer (for example, mainly geothermal cement) that is insulated by cement for solidifying the side wall of the hole drilled during excavation, a second coating layer (for example, mainly insulation material 70) that coats the periphery of the medium injection pipe and the pipe joint with an insulation material, and a pressure pump (for example, mainly a pressurized water supply pump 5) that maintains a pressure equal to or higher than the saturated vapor pressure of the medium at the desired temperature and transfers the medium without changing its phase state. It is characterized by including these components.

[0123] Due to the above characteristics, the heat medium transfer pipe can take out the medium from the ground by the medium extraction pipe without losing heat, so it is possible to generate electricity using the geothermal heat itself.

[0124] <The sixth feature point> After connecting the heat medium transfer pipes to each other with the pipe joint, it is characterized by including a pipe joint coating part (for example, mainly a pipe thread joint coating part 93) that coats the whole of the pipe joint from the outside so as to cover it. Due to the above characteristics, the heat medium transfer pipe can block the heat transfer at the part of the pipe joint by the pipe joint coating part.

[0125] <The seventh feature point> A heat medium transfer pipe (for example, mainly heat medium transfer pipe 10 (medium injection pipe 50, heat medium extraction pipe 80) · 410 · 500) that conveys the medium into the ground and recovers the medium that has absorbed heat in the ground. It is characterized in that convection blocking parts (for example, mainly convection shielding disks 73) that block the convection of groundwater that intrudes between the heat medium transfer pipe and a tubular protective pipe (for example, the third protective pipe 33) provided on the outer periphery of the heat medium transfer pipe are provided at a plurality of locations in the vertical direction.

[0126] Due to the above characteristics, the convection blocking part prevents the hot water that has entered from below into the gap between the heat medium transfer pipe and the protection pipe from mixing with the colder water above by convection and turning into colder water, thereby further enhancing the heat preservation performance of the heat medium transfer pipe.

[0127] <The eighth feature point> It is characterized in that it is provided with the annular convection shielding member which is located below the pipe joint connecting the heat medium transfer pipes, has an inner diameter larger than the outer circumference of the medium transfer pipe, and is smaller than the outer diameter of the pipe joint. Due to the above characteristics, the present invention has a structure that cannot escape upward due to the water pressure of groundwater, etc., and the workability during installation is improved.

[0128] <The ninth feature point> A heat medium transfer pipe that conveys a medium underground and recovers the medium that has absorbed heat underground, It is characterized in that it includes a plurality of protection pipes (for example, mainly the first protection pipe 31, the second protection pipe 32, and the third protection pipe 33) provided on the outer circumference of the heat medium transfer pipe, a heat insulation layer (for example, mainly foamed concrete 36, 37) provided between the protection pipe and other protection pipes, and a sealing layer (for example, mainly the closing parts 34, 35) that prevents the intrusion of groundwater from below below the heat insulation layer.

[0129] Due to the above characteristics, the sealing layer prevents the intrusion of water that is colder than the heat medium transfer pipe from below, and improves the heat insulation performance of the heat medium transfer pipe.

[0130] <The tenth feature point> It is characterized in that the heat insulation layer is formed of a light base material or concrete containing a large amount of bubbles. Due to the above characteristics, the present invention not only prevents the intrusion of water, but also improves the heat insulation performance by making it contain a large amount of air, etc.

[0131] <The eleventh feature point> The heat medium transfer pipe according to claim 8, wherein the sealing layer is formed of concrete. Due to the above characteristics, the present invention can prevent water from infiltrating through the sealing layer, and prevent the temperature of the heat medium transfer pipe from decreasing due to the infiltration of groundwater.

[0132] <The 12th feature point> A geothermal power generation system that transports a medium (e.g., mainly water, oil, etc.) underground, recovers the medium that has absorbed heat underground, and generates electricity using the heat of the recovered medium. The system includes a plurality of heat medium transfer pipes (e.g., mainly heat medium transfer pipes 10 (medium injection pipe 50, heat medium extraction pipe 80), 410, 500) for circulating the medium within the heat medium transfer pipes. To circulate the medium within the heat medium transfer pipes, the system is provided with a switching valve (e.g., mainly flow path switching valve 414) for switching the flow path of the medium, and a pressure adjustment device (e.g., mainly a pressure pump 411) for circulating the medium while maintaining the pressure at a predetermined pressure without changing the state of the medium. When the temperature of the medium decreases, the switching valve and the pressure adjustment device are driven to circulate the medium within the heat medium transfer pipes until the temperature of the medium recovers.

[0133] Due to the above characteristics, the present invention can apply pressure within the heat medium transfer pipe to prevent boiling, and by circulating hot water as a single-phase flow within the heat medium transfer pipe, it is possible to absorb heat from the geothermal zone more efficiently compared to the case of circulating as a gas-liquid two-phase flow.

[0134] <The 13th feature point> The path for circulating the medium is provided with a temperature measuring device (e.g., mainly a circulation sensor unit 412 (temperature sensor)) for measuring the temperature of the medium. Due to the above characteristics, even when the temperature of the geothermal zone is unknown, the present invention can circulate including the geothermal zone so that the temperature of the hot water becomes uniform, and measure the temperature of the circulated hot water with a temperature measuring device. Therefore, it can be used as an indicator for whether the temperature of the geothermal zone has recovered.

[0135] <The 14th feature point> A construction method of a heat medium transfer pipe (e.g., mainly heat medium transfer pipes 10 (medium injection pipe 50, heat medium extraction pipe 80), 410, 500) that conveys a medium (e.g., mainly water, oil, etc.) underground and recovers the medium that has absorbed heat underground. The method includes: a first sealing step of pouring cement (e.g., mainly cement, geothermal cement) into the excavated hole to form a first sealing layer (e.g., mainly a closing part 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) into the hole formed by the first sealing step; after the first sealing layer is stabilized, excavating together with the first sealing layer with a diameter smaller than the hole of the first sealing layer, pouring cement into the excavated hole to form a second sealing layer (e.g., mainly a closing part 34) that seals the excavated hole, which is a second sealing step; a second protective pipe embedding step of embedding a second protective pipe (e.g., mainly a second protective pipe 32) into the hole formed by the second sealing step; after the second sealing layer is stabilized, excavating together with the second sealing layer with a diameter smaller than the hole of the second sealing layer, and embedding a third protective pipe (e.g., mainly a third protective pipe 33) into the excavated hole, which is a third protective pipe embedding step; a heat insulation layer forming step of pouring foamed concrete (e.g., mainly foamed concrete 36, 37) between the first protective pipe and the second protective pipe, and between the second protective pipe and the third protective pipe; and after the third protective pipe embedding step, excavating with a diameter smaller than the hole of the third protective pipe, and embedding the heat medium transfer pipe into the excavated hole, which is a heat medium transfer pipe embedding step. It is characterized by comprising the above steps.

[0136] Due to the above features, the present invention prevents the intrusion of water with a temperature lower than the hot water flowing through the heat medium transfer pipe from below, and improves the heat insulation performance of the heat medium transfer pipe.

[0137] <The 15th feature point> A geothermal power generation method that conveys a medium (e.g., mainly water, oil, etc.) underground, recovers the medium that has absorbed heat underground, and generates electricity using the heat of the recovered medium. A hole (insertion hole) formed with a diameter larger than that of the heat medium transfer pipe is provided in the rock formation (e.g., mainly rock formation zone 38) existing in the geothermal zone. A heat transfer promotion medium (e.g., mainly heat transfer promotion medium 39) and the heat medium transfer pipe are inserted into the insertion hole, and the heat of the geothermal zone is transmitted to the heat medium transfer pipe through the heat transfer promotion medium.

[0138] Due to the above characteristics, the present invention can efficiently absorb the heat of the geothermal zone by interposing an intermediate substance between the heat medium transfer pipe and the geothermal zone even if the geothermal zone is a rock formation zone or a fractured zone with poor heat transfer.

[0139] <The 16th feature point> A geothermal power generation method that conveys a medium (e.g., mainly water, oil, etc.) underground, recovers the medium that has absorbed heat underground, and generates electricity using the heat of the recovered medium. An insertion hole, which is a hole formed with a diameter larger than that of the heat medium transfer pipe, and a medium container (receiving pipe 75) that is inserted into the insertion hole and houses a heat transfer promotion medium (e.g., mainly heat transfer promotion medium 39, water, oil, etc.) are provided in the fractured zone (e.g., mainly fractured zone 43) existing in the geothermal zone. The medium container is inserted, and the heat of the geothermal zone is transmitted to the heat medium transfer pipe through the heat transfer promotion medium housed in the medium container.

[0140] Due to the above characteristics, the present invention can efficiently absorb the heat of the geothermal zone by interposing an intermediate substance between the heat medium transfer pipe and the geothermal zone even if the geothermal zone is a rock formation zone or a fractured zone with poor heat transfer.

[0141] Other technical features are characterized in that a plurality of through holes (for example, mainly medium movement holes 76) are provided in the medium container. Thereby, it is possible to protect the heat medium transfer pipe due to the collapse of the geothermal zone or the like and maintain the state of heat transfer of the medium such as the fluid in the geothermal zone to the heat medium transfer pipe.

[0142] The present invention is not limited to the above-described embodiments at all, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

Industrial Applicability

[0143] As shown in the above-described embodiments, it can be used not only in geothermal zones where hot springs gush out, but also in volcanic zones and volcanic zones in the sea.

Explanation of Signs

[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 pipe, 32…Second protective pipe, 40…Injection pipe, 42·82…Male screw part, 33…Third protective pipe, 34·35…Foamed concrete, 36·37…Foamed concrete, 38…Rock mass zone, 39…Transfer promotion medium, 43…Fractured zone, 50…Medium injection pipe, 51·55…Pipe screw joint, 52·56…Female screw part, 53·57…Placement space part, 46·86…Coating layer, 47·87…Gripping part, 60·90…Heat insulation pipe, 61·91…Insertion pipe, 62·92…Protrusion part, 73…Convection shielding disk, 75…Receiving pipe, 76…Medium movement hole, 80·80a…Heat medium extraction pipe, 81…Extraction pipe, 85…Heat insulation part, 93…Pipe screw joint coating part, 150…Heat exchange part, 151…Heat exchanger, 155…Circulation pump, 414…Flow path switching valve, 411…Pressure feed pump, 412...Circulation sensor section, T·T2·T3...Steam turbine, G...Generator, B...Binary power generation device, CT...Cooling tower, F...Gas-liquid separator, TF...Power receiving equipment, S...Ground surface, U...Geothermal zone.

Claims

[Claim 1] A buried pipe used to utilize the recovered heat on the ground, the buried pipe transporting a medium underground and recovering the medium that has absorbed heat underground; a perforated pipe having holes on a side surface around the heat medium transfer pipe in a region where heat is recovered; A plurality of protective tubes are provided around the heat medium transport pipe in the region to be insulated, A buried pipe characterized in that a heat insulating layer is provided between the protective pipe and another protective pipe, and a lower end of the heat insulating layer is sealed with concrete or cement to form a heat insulating structure.

Images