JP7529280B2 - Geothermal power generation equipment - Google Patents

Description

The present invention relates to a heat medium transfer pipe that uses a geothermal heat source to recover heat using a medium and has an improved ability to retain heat when transferring the heat medium, and a geothermal power generation system and method that use the heat medium transfer pipe to generate power.

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

Patent Document 1 proposes a binary power generation system in which a closed loop circulation flow path is configured in which a heat source fluid absorbs heat through heat exchange with a geothermal fluid or geothermal heat, releases heat in an evaporator, and is returned to be exchanged with a geothermal fluid or geothermal heat again. The system also proposes a closed loop flow path for a cooling fluid that cools a low boiling point medium, which either releases heat into the ground for cooling, or a geothermal power generation system that includes a refrigerator and heat exchanger that use the heat source fluid after passing through the evaporator as a driving heat source, and controls the temperature of the cooling fluid to supply the cooling fluid to the condenser so that the condensation and liquefaction of the low boiling point medium in the condenser can be optimized.

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

JP 2014-84857 A Special Publication No. 2014-517925

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

A heat transfer pipe is also required to recover heat underground and transport the resulting hot water to the surface. The length of the heat transfer pipe, which depends on the temperature of the geothermal zone, must be between 1,000 and 3,000 m. The heat transfer pipe is connected to the pipes by pipe thread joints, and extends deep underground. As shown in Patent Document 2, pipe thread joints are required to have high compression resistance and sealing performance under internal and external pressure, and are firmly joined to the pipes.

However, pipe thread joints are not designed to improve heat retention, and heat transfer occurs between the inside and outside of the pipe near the ground surface where the temperature is low, resulting in the loss of heat recovered from the ground. In addition, not only pipe thread joints but also transfer pipes that require heat retention are becoming more difficult to insulate as their diameter increases, making it more difficult to balance strength and heat retention. There is also a demand for technology that improves the workability of installation without impairing heat retention performance by providing a heat retention structure.
Therefore, in order to effectively utilize the heat transfer medium obtained from underground, a technology has become necessary to transport the heat transfer medium to a separator or heat exchanger on the ground without losing heat during transport, while also taking into account operational performance.

The present invention has been developed in consideration of these problems, and aims to provide a geothermal power generation device that prevents the intrusion of water with a lower temperature than the heat medium transfer pipe from below and improves the insulation performance of the heat medium transfer pipe, in order to effectively utilize the heat obtained from the geothermal zone by using a medium on the ground.

To achieve the above-mentioned objectives, the present invention adopts the following measures.

A geothermal power generation device in which a heat medium transport pipe is buried to transport a medium underground and recover the medium that has absorbed heat underground,
a first sealing layer that seals with a heat insulating layer provided between the first protective tube and the second protective tube;
a second sealing layer that seals with a heat insulating layer provided between the second protective tube and the third protective tube;
a heat medium transfer pipe provided inside the third protective pipe.

Due to the above characteristics, the sealing layer prevents water with a lower temperature than the heat transfer pipe from entering from below, improving the insulating performance of the heat transfer pipe.

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

Embodiments of geothermal power generation systems 1, 100, 200, 300, and 400 according to the present invention will be described in detail with reference to the drawings. Note that the embodiments and drawings described below are intended to exemplify some of the embodiments of the present invention, and are not intended to be used for the purpose of limiting the present invention to these configurations, and may be modified as appropriate without departing from the gist of the present invention. Corresponding components in each drawing are denoted by the same or similar reference numerals.

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

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

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

Since not all of the hot water L3 supplied to the steam separator F becomes steam V1, a large amount of hot water L4, or drain, is sent from the steam separator F to the hot water service tank 4. In addition, the steam V3 exhausted by the steam turbine T is sent to the condensation unit 17, and the steam V4 sent to the condensation 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, and is temporarily stored in the condensation tank 14 before being sent to the hot water service tank 4 by the condensation pump 5.

Hot water L8 in the hot water service tank 4 is transferred to the heat medium transfer pipe 10 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 earth again at a depth where the geothermal zone U is located and undergoes heat exchange. The heat-exchanged hot water L2 is transferred by the pressurized water supply pump 3 via the heat medium transfer pipe 10 described below.

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

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

The medium injection pipe 50 is made of materials such as steel or stainless steel. In the high temperature region of the geothermal heat zone U, the medium injection pipe 50 has cylindrical fins with circular cross-sections welded to it to increase the outer surface area and facilitate the transfer of heat from the geothermal heat zone U. In the low temperature region close to the ground surface S, the medium injection pipe 50 has an insulating structure (described below) to prevent the loss of heat from the hot water L1 injected under pressure from the hot water service tank 4.

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

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

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

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

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

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

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

Next, referring to FIG. 4, the insulation material 70 provided around the medium injection tube 50 will be described. The insulation material 70 is in close contact with the periphery of the medium injection tube 50, and has an insulation 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 insulation material 70 and the coating layer 46 provide an insulation structure for the outside of the medium injection tube 50.

Next, the heat medium extraction pipe 80 will be described with reference to Figures 7 and 8. The heat medium extraction pipe 80 is installed to recover heat deep underground using hot water, transport it to the ground, generate steam, and use the heat for steam power generation. With reference to Figures 2 to 6, the explanation of the parts of the heat medium extraction pipe 80 that are exactly the same as the medium injection pipe 50 will be omitted, and only the different parts will be explained. The heat medium extraction pipe 80 is located inside the medium injection pipe 50, and is composed of an extraction pipe 81, a pipe thread joint 55, and a heat retention pipe 90.

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

In this way, the connection of the heat medium extraction pipe 80 can be completed with a simple operation, similar to the above-mentioned medium injection pipe 50. Furthermore, not only does the heat retention performance of the heat medium extraction pipe 80 improve with the heat retention pipe 90, but the replacement of the heat retention pipe 90 itself and the installation of the heat medium extraction pipe 80 are easy. Furthermore, in addition to the medium injection pipe 50 also having a good heat retention state due to the heat retention pipe 60 and the thermal insulation structure, the heat medium extraction pipe 80 has an improved heat retention state due to the heat retention pipe 90, the thermal insulation part 85, and the coating layer 86, making it possible to extract hot water L3 from the ground without losing heat.

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

As shown in Figure 11 (C), the measured temperature gradient was 890°C/m between P1 and P2 of the conventional medium injection pipe 101, and 3,980°C/m between P5 and P6 of the medium injection pipe 50 of the present invention, indicating that the medium injection pipe 50 of the present invention has a larger temperature difference than the conventional medium injection pipe 101, and it can be confirmed that the insulation performance is improved by the heat-insulating pipe 60.
Furthermore, the temperature difference between P3 and P4 of the conventional medium injection pipe 101 was 3,420° C./m, while the temperature difference between P7 and P8 of the medium injection pipe 50 of the present invention was 9,790° C./m, indicating that the medium injection pipe 50 of the present invention has a larger temperature difference than the conventional medium injection pipe 101, and it can be confirmed that the insulation performance is improved by the coating layer 46.
As described above, the present invention can include the heat medium transfer pipe 10 with improved thermal insulation performance.

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

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

The extraction pipe 81a has a thread groove on the outer periphery at both ends. The pipe thread joint 55 has a thread groove on the inner periphery so that it fits into the thread groove of the extraction pipe 81a. The extraction pipe 81a can be extended by connecting the extraction pipes 81 together by fitting them with the pipe thread joint 55.

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

The heat-insulating tube 91 has annular protrusions 92a, 92b, which have an inner diameter equal to the outer diameter of the heat-insulating tubes 91a, 91b and are made of the same resin, joined to the center of the heat-insulating tubes 91a, 91b by ultrasonic welding or the like. As a result, the heat-insulating tubes 91a, 91b and the protrusions 92a, 92b are formed as a single unit. Note that the heat-insulating tube 91 may also be formed as a single unit by molding, not limited to welding.

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

In this way, the work of connecting the heat medium extraction pipe 80a can be completed with a simple operation. The protruding parts 92a, 92b are pressurized by the pressurized water supply pump 3 to prevent the hot water from boiling, but the protruding parts 92a, 92b are formed so as to be held between the extraction pipe 81a even when the hot water is pumped. Therefore, the heat retention pipe 91 will not fall off.
As described above, since both ends of the heat retaining tube 91 are held between the outlet tubes 81a, the heat retaining tube 91 will not fall off in the vertical direction.

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

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

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

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

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

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

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

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

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

(Method of generating electricity using the above system)
1, 9 and 10, the power generation method will be described. The depth of the hole drilled by boring to obtain steam with a temperature of about 200°C on the ground reaches a depth of about 2000m to 3000m underground. It is considered that the deeper the depth, the higher the temperature that can be obtained, but it is determined by taking into account the cost of excavation. The geothermal zone U is best at a temperature of 200°C to 300°C, and the following values will change appropriately depending on the temperature obtained near the deepest part of the geothermal zone U.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

In view of the above, in the present invention, as shown by the shaded area in Figure 10, the insulating areas of the medium injection pipe 50 and the heat medium extraction pipe 80 are formed from a material with an effective thermal conductivity of 0.1 W/m·K or less. The best material has an insulating performance of 0.05 W/m·K to 0.001 W/m·K. Maintaining insulating performance has the advantage of preventing a drop in temperature at the outlet, which means that the pressure of the pressurized water pump 3 does not need to be set high. In Figure 14, the dashed line shows the underground temperature distribution 21 including the geothermal zone U, and the solid line shows the hot water temperature distribution 25.

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

Furthermore, in areas of high underground temperature distribution, i.e., the heat absorption areas required for power generation, the medium injection pipe 50 is made of a material with a high effective thermal conductivity of 50 W/m·K. The higher the effective thermal conductivity, the better, but considering pressure and corrosion underground, it is preferable to form it from a metallic material, and the effective thermal conductivity should be 20 W/m·K or higher.

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

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

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

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

The cooling water 157b, 158b is 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, whereby the raw water 16 is heated and the cooling water 157b, 158b is cooled, thereby providing an effective exchange of heat throughout the entire geothermal power generation system 200. By heating the raw water 16, it becomes possible to directly input it into the hot water service tank 4 without passing through the condensation unit 17.

By using these working media (M1 to M3), even hot water at 70°C to 95°C can generate electricity if there is a flow rate of 9t/h to 24t/h. In this system, the media exchange heat within a closed system.

The working medium (M1 to M3) that can be used is determined by the heat exchange temperature, so there may be cases where the temperature is restricted by the binary power generation device B. To accommodate such cases, the pressurized water power generation device 1b is provided with a temperature adjustment system 161 that utilizes the air cooling tower CT of the condensation unit 17. In particular, when the temperature of the drain L4 that did not become steam is high, it is possible to lower the temperature to a range that matches the set temperature of the binary power generation device B.

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

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

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

The power receiving equipment TF2 supplies electricity to electric power companies and the like via the power grid. Here, the working medium M (M1 to M23) is a non-flammable and non-toxic inert gas such as HFC-245fa or R245fa, or a medium with a low boiling point (a mixture of water and ammonia, or a hydrocarbon (pentane)). In this embodiment, the working medium (M1 to M3) used in the binary power generation device C is a working medium with a high boiling point range and a working medium (M21 to M23) with a boiling point lower than that of the working medium (M1 to M3). By using working mediums with two different boiling point ranges, namely, a working medium with a high boiling point range and a working medium (M21 to M23) with a boiling point lower than that of the working medium (M1 to M3), it becomes possible to utilize heat in multiple stages, and efficient power generation is possible.

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

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

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

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

The geothermal power generation system 100 passes pressurized hot water L3 from the medium transfer pipe 10 installed in the pressurized water heat exchanger 1a through the heat exchanger 151 as hot water without steaming it. Since the geothermal power generation system 100 does not have a steam-water separator F, it is possible to reduce losses by absorbing geothermal heat with hot water and using it directly, and to recover geothermal heat and use it for power generation.

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

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

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

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

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

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

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

The upper insulation area 22, with the dashed and dotted line as the boundary, uses piping with excellent insulation properties, with the medium injection pipe 50 made of a material with an effective thermal conductivity of 0.1 W/m·K or less. The lower absorption area 26, with the dashed and dotted line as the boundary, uses piping with excellent heat absorption properties, with the medium injection pipe 50 made of a material with an effective thermal conductivity of 50 W/m·K or more.

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

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

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

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

The blocking sections 34 and 35 prevent water with a lower temperature than the medium injection pipe 50 from entering from below, improving the insulation performance of the heat medium transfer pipe 500. The top of the heat medium transfer pipe 500 is also blocked with concrete or steel material (not shown) to prevent water from entering from above.

Next, a method of installing the heat medium transport pipe 500 of the present invention will be described with reference to Figs.
First, an excavation machine is used to excavate the deepest part of the ground to a depth of 700 m. During excavation, the side walls are hardened with geothermal cement or the like to prevent collapse. When the excavation reaches the 700 m depth, a blockage section 35 is formed by filling the section from 10 m to 100 m deep with concrete material as shown in FIG. 16, and the above-mentioned third protective pipe 33 is buried.

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

Finally, as shown in Figure 15, the diameter of the excavator is further reduced, and excavation is performed to a size large enough to bury the medium injection pipe 50. The excavation is continued to a position approximately 3000 m from the geothermal zone U of the desired temperature 210 of the heat absorption area 26, and the above-mentioned medium injection pipe 50 and heat medium extraction pipe 80 are buried.

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

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

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

The receiving pipe 75 shown in FIG. 24 is a schematic diagram showing a portion of the lower part of the receiving pipe 75 shown in FIG. 19. The receiving pipe 75 has a medium movement hole 76 that is a through hole that penetrates the side surface. The receiving pipe 75 has a hole so that a medium such as hot water can move through the medium movement hole 76 when the geothermal zone U is covered with a fluid medium such as hot water.

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

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

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

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

Since not all of the hot water L3 supplied to the steam separator F becomes steam V1, a large amount of hot water L4, or drain, is sent from the steam separator F to the hot water service tank 4. In addition, the steam V3 exhausted by the steam turbine T is sent to the condensation unit 17, and the steam V4 sent to the condensation 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, and is temporarily stored in the condensation tank 14 before being sent to the hot water service tank 4 by the condensation pump 5.

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

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

When circulating hot water L3 in the heat medium transfer pipe 410f, a pressure pump 411 is provided to circulate the water under pressure to prevent boiling. The geothermal power generation system 400 also uses the pressurized water supply pump 3 to circulate the water through the multiple heat medium transfer pipes 410 under pressure to prevent boiling even during normal power generation, but when one pressurized water supply pump 3 is not enough, the pressure pump 411 is used. The pressure pump 411 adjusts the pressure so that the pressure in the heat medium transfer pipe 410f is constant.

By applying pressure inside the heat medium transfer pipe 410f to prevent boiling and circulating the hot water through the heat medium transfer pipe 410f as a single-phase flow, it is possible to absorb heat from the geothermal heat U more effectively than when circulating the hot water through the heat medium transfer pipe 410f as a two-phase gas-liquid flow.

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

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

Thanks to the above features, the present invention not only improves the insulation performance of the heat medium transfer pipe by using the insulation pipe, but also makes it easier to replace the heat medium insulation pipe itself and install the heat medium transfer pipe.

<Second characteristic point>
The heat medium insulation pipe is characterized by comprising an insertion pipe (e.g., mainly insertion pipes 61 and 91) that is inserted into the heat medium transfer pipe, and a protrusion (e.g., mainly protrusions 62 and 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-mentioned features, the present invention makes it easy to replace the heat medium insulation pipe itself and to install the heat medium transfer pipe.

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

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

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

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

Due to the above characteristics, the heat medium transfer pipe can extract the medium from the ground through the medium extraction pipe without losing heat, making it possible to generate electricity using the geothermal heat itself.

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

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

The above features of the convection breaker prevent hot water entering the gap between the heat transfer pipe and the protective pipe from below from mixing with the cooler water above through convection and becoming cooler water, thereby further improving the thermal insulation performance of the heat transfer pipe.

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

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

Due to the above characteristics, the sealing layer prevents water with a lower temperature than the heat transfer pipe from entering from below, improving the insulating performance of the heat transfer pipe.

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

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

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

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

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

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

Thanks to the above features, the present invention prevents the intrusion of water with a lower temperature than the hot water flowing through the heat transfer pipe from below, improving the insulation performance of the heat transfer pipe.

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

Thanks to the above features, the present invention makes it possible to efficiently absorb heat from a geothermal zone by placing an intermediary material between the heat medium transfer pipe and the geothermal zone, even if the geothermal zone is a bedrock zone or a fractured zone where heat transfer is poor.

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

Thanks to the above features, the present invention makes it possible to efficiently absorb heat from a geothermal zone by placing an intermediary material between the heat medium transfer pipe and the geothermal zone, even if the geothermal zone is a bedrock zone or a fractured zone where heat transfer is poor.

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

The present invention is not limited to the above-described embodiment, and it goes without saying that it can be implemented in various forms as long as it falls within the technical scope of the present invention.

As shown in the above embodiment, it can be used not only in geothermal areas where hot springs gush out, but also in volcanic areas and underwater volcanic areas.

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 to f), 500... Heat medium transfer pipe,
27: evaporation curve, 31: first protective tube, 32: second protective tube, 40: injection tube,
42, 82... male thread portion, 33... third protective tube, 34, 35... foamed concrete,
36-37...foamed concrete, 38...rock zone, 39...transmission promotion medium, 43...fracture zone,
50...medium injection pipe, 51/55...pipe thread joint, 52/56...female thread portion,
53, 57... Placement space part, 46, 86... Covering layer, 47, 87... Gripping part,
60/90...heat-insulating pipe, 61/91...insertion pipe, 62/92...projection portion, 73...convection shield plate,
75: receiving tube, 76: medium movement hole, 80/80a: heat medium extraction tube, 81: extraction tube,
85...insulation portion, 93...pipe thread joint covering portion, 150...heat exchange portion, 151...heat exchanger,
155...circulation pump, 414...flow path switching valve, 411...pressure pump,
412...circulation sensor unit, T, T2, T3...steam turbine, G...generator,
B: binary power generation device, CT: cooling tower, F: steam separator, TF: power receiving equipment,
S...surface, U...geothermal zone.

Claims (1)

A geothermal power generation device including a heat medium transport pipe that transports a medium underground and recovers the medium that has absorbed heat underground,
A convection cut-off section is provided in an insulating region in a geothermal region having a low temperature, and a plurality of tubular protective tubes are provided around the heat medium transport pipe in the insulating region ;
a convection blocking portion provided at a plurality of positions in the vertical direction between the heat medium transfer pipe and the protective pipe closest to the heat medium transfer pipe, and blocking convection in the vertical direction;
A geothermal power generation device characterized in that the protective pipe closest to the heat medium transfer pipe is arranged deeper underground than the other protective pipes, and convection of hot water from underground is inhibited between the convection breakers arranged above and below.

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