CN113224979B - Geothermal/seawater semiconductor temperature difference power generation system and method - Google Patents

Abstract

The invention provides a geothermal/seawater semiconductor temperature difference power generation system, which comprises: the U-shaped well is arranged in a preset sea area along the vertical direction, the well mouth of the U-shaped well is exposed out of the sea surface, and the lower horizontal section of the U-shaped well is positioned in the geothermal reservoir; the high-level sea reservoir is arranged in an area close to the coast; the first temperature difference power generation pipe is arranged in the horizontal section of the U-shaped well in a penetrating mode and is communicated with the high-level sea reservoir through an HDPE pipe in butt joint with the first temperature difference power generation pipe; the second thermoelectric generation tube is laid on the seabed; the first thermoelectric generation unit is embedded in the pipe wall of the first thermoelectric generation pipe and used for generating power according to the internal and external temperature difference of the first thermoelectric generation pipe. Through directly placing first thermoelectric generation unit in geothermal reservoir, the cold junction is regarded as to the mobile sea water in the thermoelectric generation pipe, not only can effectually carry out thermoelectric generation fast, has greatly improved the generating efficiency.

Description

Geothermal/seawater semiconductor temperature difference power generation system and method

Technical Field

The invention relates to the technical field of sea area geothermal energy utilization, in particular to a geothermal/seawater semiconductor temperature difference power generation method.

Background

Geothermal energy is a renewable clean energy source from the deep part of the earth, is an almost inexhaustible resource, and can be directly used for heat supply or power generation. The energy can be used for generating electricity and basically belongs to medium-high temperature geothermal energy resources. Geothermal heat can be divided into different types according to heat storage media, construction cause, and water heat transfer mode. According to the heat storage medium, the heat storage medium can be divided into a pore type geothermal resource, a fracture type geothermal resource and a karst fracture type geothermal resource; the construction can be divided into a sedimentary basin type geothermal resource and a raised mountain type geothermal resource; the heat transfer modes can be divided into conduction type geothermal resources and convection type geothermal resources. The terrestrial heat is classified according to the temperature and can be divided into high-temperature terrestrial heat resources (the temperature is more than or equal to 150 ℃), medium-temperature terrestrial heat resources (the temperature is less than 150 ℃ and more than or equal to 90 ℃) and low-temperature terrestrial heat resources (the temperature is less than 90 ℃).

In China, high-temperature geothermal resources are mainly distributed in southern Tibet, Western Yunnan, Western Sichuan and Taiwan, and medium-low temperature geothermal resources are distributed all over the country, so that the reserves are huge. There are three major technical challenges that have hindered the development of geothermal power generation, namely geothermal recharge, corrosion and scaling. The geothermal recharging technology is complex in requirement and high in cost. In addition, the problems that ground subsidence is caused by super-mining underground hot water, and harmful elements in warm drainage have bad influence on the environment and the like exist.

Geothermal power generation is a novel power generation technology using underground hot water and steam as power sources, and is mainly divided into four types: dry steam geothermal power generation, flash evaporation geothermal power generation, double-cycle (organic Rankine cycle) geothermal power generation and dry hot rock power generation. At present, medium and low temperature geothermal power plants in China are shut down successively because geothermal power generation is technically feasible but economically infeasible.

The semiconductor thermoelectric power generation is a unique energy conversion mode, has the advantages of no other energy conversion modes, is suitable for recycling low-level energy and is particularly suitable for small temperature difference. The semiconductor thermoelectric power generation is a novel energy-saving and environment-friendly power generation technology, and can convert low-grade heat energy such as geothermal energy, solar energy, industrial and domestic waste heat, automobile exhaust waste heat and the like into electric energy. The research of the semiconductor temperature difference power generation technology originates from the 40 th generation of the 20 th century, and the power generation efficiency is only improved by 1.5-2 percent and is far lower than the power generation modes of hydropower, thermal power, nuclear power, wind power, photoelectricity and the like; with the development of material synthesis technology, thermoelectric materials are also turned to various novel thermoelectric materials from the traditional material selection target, and researchers in various countries continuously search and develop novel thermoelectric materials with higher merit values. The austrian research team in 2013 realizes that the thermoelectric figure of merit of the thermoelectric power generation material is as high as 5 to 6. The leap-type improvement of the thermoelectric figure of merit means that the efficiency of thermoelectric power generation is expected to become a new commercial power generation technology.

Compared with the traditional power generation mode, the thermoelectric power generation has five outstanding advantages: firstly, no mechanical moving part is arranged in the thermoelectric generation technology, so that no vibration and noise exist, and the structure is compact; secondly, the adaptability to heat sources is wide, heat energy can be converted into electric energy under the condition of small temperature difference, and the thermoelectric power generation technology can utilize the heat energy in a wide temperature range (300-1400K) by selecting proper semiconductor materials; thirdly, the volume is small, the weight is light, and the carrying and the transportation are convenient; fourthly, the operation performance is stable, the reliability is high, the maintenance-free operation can be carried out for a long time, and the service life is long; fifthly, the method is safe and pollution-free, and the thermoelectric generation technology can not generate waste in the energy conversion process, thereby achieving zero emission to the environment. Therefore, the advantages of the thermoelectric power generation technology enable the thermoelectric power generation technology to show great potential in low-grade energy utilization, and the technology related to thermoelectric power generation is also greatly emerged.

The Chinese invention patent, application number CN201811641277.7, discloses a system and a method for exploiting sea hydrates by a thermoelectric generation thermal shock method, and the scheme is a technology for exploiting sea hydrates by using geothermal energy. The method is characterized in that seawater is used as a cold end, geothermal heat below a hydrate reservoir is used as a hot end, temperature difference power generation is carried out, and then electricity generated by a temperature difference device is used for heating the hydrate reservoir, so that the purpose of exploiting the sea hydrate is achieved. The invention has undergone the multiple conversion of geothermal energy → thermoelectric generation → electric heating hydrate reservoir, and has the defects of large heat energy loss and low conversion efficiency.

The utility model discloses a chinese utility model patent, application number CN201920065048.9, discloses a film thermoelectric generation coupling selectivity absorption coating structure, and its scheme is the solar thermal energy cogeneration system that utilizes the difference in temperature that solar energy heat collecting tube light facing face and shady face formed to generate electricity. According to the law of conservation of energy, the energy received by the solar heat collecting pipe is certain, and partial heat energy is utilized for carrying out

At present, the reason why the thermoelectric power generation technology has not been widely applied is that: firstly, the efficiency of the thermoelectric power generation technology is too low, and compared with the traditional mode, the thermoelectric power generation technology has no economic advantage; secondly, the manufacturing cost of the temperature difference power generation module is high; thirdly, the design and operation experience of the thermoelectric power generation system is deficient.

Sea geothermal energy is heat energy which is stable and has huge reserves. However, geothermal heat is a large low-value energy source and is not suitable for long-distance transportation. The remote transportation of underground hot water has high construction and pipeline maintenance cost and large heat energy loss, and restricts the utilization of the geothermal energy in the sea area with huge heat storage. Therefore, how to effectively utilize the sea geothermal energy to generate electricity is a problem that needs to be solved urgently. Seawater has large heat capacity and extremely large quantity, and is a large energy reservoir for human beings. The temperature difference formed by the sea area terrestrial heat and the sea water is used for generating electricity, so that the potential development is great.

Disclosure of Invention

In view of the above, the present invention provides a geothermal/seawater semiconductor thermoelectric power generation system and method, which aims to solve the problems of generating power by using sea-area geothermal energy/seawater, improving the efficiency of sea-area geothermal power generation and reducing the construction and maintenance costs when performing thermoelectric power generation by using sea-area geothermal energy.

In one aspect, the present invention provides a geothermal/seawater semiconductor thermoelectric power generation system, comprising:

the U-shaped well is arranged in a preset sea area along the vertical direction, the well mouth of the U-shaped well is exposed out of the sea surface, and the lower horizontal section of the U-shaped well is positioned in the geothermal reservoir; the U-shaped well comprises a first well, a second well and a horizontal well, the lower ends of the first well and the second well are communicated through the horizontal well, and the horizontal well is positioned in the geothermal reservoir;

the high-level sea reservoir is arranged in an area close to the coast, the high-level sea reservoir contains seawater, and the water level height of the high-level sea reservoir is greater than the sea level height;

the first thermoelectric generation tube is arranged in the horizontal section of the U-shaped well in a penetrating mode and is communicated with the high-level sea reservoir through an HDPE tube in butt joint with the first thermoelectric generation tube; the second thermoelectric generation tube is laid on the seabed, and the first thermoelectric generation tube is communicated with the second thermoelectric generation tube through an HDPE (high-density polyethylene) tube;

the first thermoelectric generation unit is embedded in the pipe wall of the first thermoelectric generation pipe and is used for generating power according to the internal and external temperature difference of the first thermoelectric generation pipe;

and the second thermoelectric generation unit is embedded in the pipe wall of the second thermoelectric generation pipe, is positioned on the seabed outside the U-shaped well and is in contact with the seawater.

Further, the geothermal/seawater semiconductor thermoelectric power generation system further comprises:

the power management unit, with first thermoelectric generation unit and second thermoelectric generation unit electricity are connected, the power management unit be used for with the electricity that first thermoelectric generation unit and second thermoelectric generation unit were sent is carried to the user or is incorporated into the electric wire netting.

Further, first thermoelectric generation pipe and second thermoelectric generation pipe include annular structure's interior heat conduction insulating layer and outer heat conduction insulating layer respectively, first thermoelectric generation unit and second thermoelectric generation unit set up respectively between interior heat conduction insulating layer, the outer heat conduction insulating layer.

Further, first thermoelectric generation unit and second thermoelectric generation unit include a plurality of thermoelectric generation modules respectively, and are a plurality of the even range of thermoelectric generation module is in between interior heat conduction insulating layer and the outer heat conduction insulating layer, just thermoelectric generation module sets up two rows side by side.

Further, the thermoelectric generation module comprises a thermoelectric arm layer, an inner copper sheet layer and an outer copper sheet layer, wherein the thermoelectric arm layer is arranged between the inner copper sheet layer and the outer copper sheet layer.

Furthermore, one side of the high-level sea reservoir facing the sea is provided with a one-way gate and a wave guide wall, the one-way gate is used for enabling sea water to enter the reservoir when tide rises, and the wave guide wall is used for guiding sea waves into the reservoir.

Further, the power management unit comprises a control module, and the control module is used for controlling the flow speed of the seawater in the thermoelectric generation tube according to the generated energy of the first thermoelectric generation unit and the internal and external temperature difference of the thermoelectric generation tube.

Compared with the prior art, the invention has the beneficial effects that the U-shaped well is embedded in the sea bottom, the lower part of the U-shaped well is positioned in a geothermal reservoir below the sea bottom, the high-level sea reservoir obtains normal-temperature sea water from the sea, the water level in the high-level sea water reservoir is higher than the sea level, the first thermoelectric generation tube is positioned in the U-shaped well, the second thermoelectric generation tube is laid on the sea bottom, when the normal-temperature sea water in the high-level sea water reservoir is discharged to the sea bottom through the first thermoelectric generation tube and the second thermoelectric generation tube, the temperature of the sea water in the thermoelectric generation tube where the first thermoelectric generation unit is positioned is lower to form a cold end when flowing through the first thermoelectric generation unit, and the temperature of the geothermal reservoir outside the thermoelectric generation tube is higher to form a hot end, so that the temperature difference is formed between the inner side and the outer side of the first thermoelectric generation unit to generate electricity. The system has a simple structure, is convenient to implement, greatly reduces the cost investment, can quickly and effectively perform temperature difference power generation by directly placing the first temperature difference power generation unit in the geothermal reservoir and taking normal-temperature seawater as a cold end, greatly improves the power generation efficiency, does not need to extract geothermal resources, reduces the working procedures and further can improve the working efficiency; the normal-temperature seawater is fully utilized, and no additional water source is needed to be injected, so that the utilization rate of the ocean geothermal resources is improved, the cost is reduced, and the environment is greatly protected.

Further, through setting up the second thermoelectric generation unit that is located low temperature sea water, low temperature sea water in the thermoelectric generation pipe is behind geothermal reservoir and first thermoelectric generation unit, low temperature sea water in the thermoelectric generation pipe is heated up, form high temperature sea water, when high temperature sea water flows through second thermoelectric generation unit, make inside and outside production difference in temperature of second thermoelectric generation unit, and then make second thermoelectric generation unit generate electricity, can utilize the sea water after rising temperature once more effectively through setting up second thermoelectric generation unit, thereby can improve the utilization ratio of the energy effectively, further generate electricity simultaneously through the in-process of first thermoelectric generation unit and second thermoelectric generation unit sea water circulation once more, electric energy production efficiency is greatly improved.

Furthermore, the invention does not need to extract underground hot water, avoids the damage of high-salinity elements and harmful gases in the underground hot water to the human environment, saves a submersible pump for pumping water and power consumption, and reduces the initial investment cost and the operation cost.

Furthermore, the lower connecting section of the U-shaped well is buried in a geothermal reservoir deep underground, heat energy is converted into electric energy in the connecting section, the electric energy is output to the ground, geothermal water pipelines and laying thereof are omitted, corrosion and scaling of the geothermal water pipelines are avoided, and investment of marine organism adhesion resistance and protection cost is greatly reduced.

On the other hand, the invention also provides a geothermal/seawater semiconductor temperature difference power generation method, which is implemented by adopting the geothermal/seawater semiconductor temperature difference power generation system and comprises the following steps:

step a: introducing seawater into a high-level seawater reservoir, wherein the water level of the high-level seawater reservoir and the sea level form a water level difference, so that normal-temperature seawater in the high-level seawater reservoir flows through the thermoelectric generation tube and is discharged into the ocean;

step b: when the normal-temperature seawater flows through a first temperature difference power generation unit in a geothermal reservoir, power generation is carried out after temperature difference is generated between the inner side and the outer side of the first temperature difference power generation unit;

step c: the normal temperature seawater flows through the geothermal reservoir and then is heated into high temperature seawater, and when the high temperature seawater flows through the second temperature difference power generation unit, the temperature difference is generated between the inside and the outside of the second temperature difference power generation unit and then power generation is carried out;

step d: and the power generated by the first temperature difference power generation unit and the second temperature difference power generation unit is transmitted to a power management unit, and the power is transmitted to a user or is merged into a power grid through the power management unit.

It can be understood that the geothermal/seawater semiconductor thermoelectric generation method is implemented by using the geothermal/seawater semiconductor thermoelectric generation system, and the geothermal/seawater semiconductor thermoelectric generation system have the same beneficial effects, and are not described in detail herein.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 is a schematic structural diagram of a geothermal/seawater semiconductor thermoelectric power generation system provided in an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a first vertical segment provided by an embodiment of the present invention;

FIG. 3 is a schematic longitudinal sectional view of a thermoelectric power generation pipeline according to an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a thermoelectric generation pipeline provided by an embodiment of the invention;

FIG. 5 is a schematic connection diagram of a thermoelectric generation module according to an embodiment of the present invention;

FIG. 6 is a schematic view of a connection structure of a thermoelectric leg according to an embodiment of the present invention;

FIG. 7 is a schematic view of a planar arrangement of half pipe walls of thermoelectric arms in a thermoelectric generation unit according to an embodiment of the present invention;

fig. 8 is a schematic plan view of a high-level sea reservoir provided in an embodiment of the present invention;

FIG. 9 is a functional block diagram provided by an embodiment of the present invention;

fig. 10 is a schematic flow chart of a geothermal/seawater semiconductor thermoelectric power generation method according to an embodiment of the present invention.

In the figure: 1-U-shaped well, 2-thermoelectric power generation tube, 3-high sea reservoir, 4-power management unit, 5-first thermoelectric power generation unit, 6-second thermoelectric power generation unit, 7-first well, 8-second well, 9-horizontal communication well, 10-first horizontal section, 11-first vertical section, 12-horizontal connection section, 13-second vertical section, 14-second horizontal section, 15-one-way gate, 16-wave guide wall, 17-water outlet, 18-water outlet, 19-main cable, 20-inner heat conduction insulating layer, 21-outer heat conduction insulating layer, 22-inner copper sheet layer, 23-outer copper sheet layer, 24-thermoelectric arm layer, 25-copper sheet, 26-heat insulation pouring sealant, 27-braided skeleton steel wire, 28-positive cable, 29-negative cable, 30-N type thermoelectric arm, 31-P type thermoelectric arm, 50-temperature difference power generation module, 200-temperature difference power generation pipeline, 202-connecting cable, 201-submarine cable, 281-positive connecting wire and 291-negative connecting wire.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Referring to fig. 1, the present embodiment provides a geothermal/seawater semiconductor thermoelectric power generation system, which includes a U-shaped well 1, a high-level sea reservoir 3, a thermoelectric power generation pipe 2, a first thermoelectric power generation unit 5, and a power management unit 4, wherein the U-shaped well 1 is vertically disposed in a preset sea area, an open end of an upper portion of the U-shaped well 1 is exposed out of a sea surface, and a connection section of a lower portion of the U-shaped well is embedded in the geothermal reservoir; the high-level sea reservoir 3 is arranged in an area close to the coast, the interior of the high-level sea reservoir is used for containing seawater, and the water level height of the high-level sea reservoir 3 is greater than the sea level height; the temperature difference power generation pipe 2 penetrates through the U-shaped well 1, a first end of the temperature difference power generation pipe 2 is communicated with the high-level sea reservoir 3, a second end of the temperature difference power generation pipe 2 is laid on the sea floor, and the temperature difference power generation pipe 2 is used for discharging seawater in the high-level sea reservoir 3 to the sea area; the first thermoelectric generation unit 5 is embedded in the side wall of the thermoelectric generation tube 2, the first thermoelectric generation unit 5 is positioned in the geothermal storage layer, and the first thermoelectric generation unit 5 is used for generating power according to the temperature difference between the inside and the outside of the thermoelectric generation tube 2; and the power management unit 4 is connected with the first temperature difference power generation unit 5, and the power management unit 4 is used for transmitting the power generated by the first temperature difference power generation unit 5 to a user or merging the power into a power grid.

Specifically, the U-shaped well 1 is buried on the seabed, the lower portion of the U-shaped well 1 is located in a geothermal reservoir below the seabed, the high-level sea reservoir 3 obtains normal-temperature sea water from the sea, the height of the water level in the high-level sea reservoir 3 is larger than the height of the sea level, the thermoelectric generation tube 2 penetrates through the U-shaped well 1, the normal-temperature sea water in the high-level sea reservoir 3 is discharged to the seabed through the thermoelectric generation tube 2, the first thermoelectric generation unit 5 and the thermoelectric generation tube 2 are embedded in the side wall of the thermoelectric generation tube 2, the first thermoelectric generation unit 5 is arranged at one section of the thermoelectric generation tube 2 located in the geothermal reservoir, the first thermoelectric generation unit 5 is completely located in the geothermal reservoir, and the first thermoelectric generation unit 5 and the power management unit 4 are electrically connected together. When the seawater in the high-level sea reservoir 3 is discharged to the normal-temperature seawater in the reservoir through the thermoelectric generation tube 2, and flows through the first thermoelectric generation unit 5, the temperature of the seawater in the thermoelectric generation tube 2 where the first thermoelectric generation unit 5 is located is low to form a cold end, and the temperature of the geothermal reservoir outside the thermoelectric generation tube 2 is high to form a hot end, so that the inner side and the outer side of the first thermoelectric generation unit 5 form temperature difference to generate electricity, and the electricity generated by the first thermoelectric generation unit 5 is managed through the power management unit 4.

The system of the embodiment has a simple structure, is convenient to implement, greatly reduces the cost investment, can quickly and effectively perform temperature difference power generation by directly placing the first temperature difference power generation unit in the geothermal reservoir and using normal-temperature seawater as a cold end, greatly improves the power generation efficiency, does not need to extract geothermal resources, reduces the processes, and further can improve the working efficiency; the normal-temperature seawater is fully utilized, and no additional water source is needed to be injected, so that the utilization rate of the ocean geothermal resources is improved, the cost is reduced, and the environment is greatly protected.

Specifically, the present embodiment performs a geothermal exploration evaluation before implementation. Exploration and drilling risks are that the results of the exploration do not demonstrate whether the resource is of exploitation value or may overestimate/underestimate the potential of the resource. In undeveloped areas, uncertainty persists until the well is drilled. The results of the exploration phase have a direct impact on downstream development activities, including the number of wells required, the scale of the power plant, the technology selection and operating costs, etc. During the drilling phase, risks that may be encountered include drill string sticking, drill tool breakage, toxic gas evolution, lost circulation, etc. Well-established drilling plans and enhanced supervision may reduce drilling risks to some extent.

Specifically, the temperature, physical properties and chemical components of the geothermal fluid are determined through geothermal exploration and evaluation, the characteristics of a geothermal fluid dynamic field, the compensation and discharge conditions and the characteristics of a geothermal field are found out, and the geothermal resource storage capacity is estimated. The following parameters should be obtained during the evaluation of geothermal resources: a) geothermal well parameters: geothermal well location, depth, exposure heat storage thickness, production capacity, temperature, pressure, fluid chemistry, etc. b) Thermal storage geometrical parameters: heat storage area, top plate depth, bottom plate depth, heat storage thickness and the like. c) Physical properties of heat storage: heat storage temperature, pressure, density, specific heat, thermal conductivity, compression coefficient and the like of the rock. d) Hot fluid properties: the volume, specific gravity, enthalpy, kinetic viscosity, kinematic viscosity, etc. of the hot fluid. e) Parameters of permeability to heat storage and capacity to store fluid: permeability, permeability coefficient, pressure conductivity coefficient, elastic water release coefficient, porosity, effective porosity, and the like. f) Monitoring data: the production, recharge, temperature, pressure, chemical composition, etc. of the geothermal well varies over time. g) Boundary conditions of heat storage: the location of the boundary, thermodynamic and hydrodynamic characteristics, etc. The temperature difference is used as basic data for designing a seawater/geothermal/seawater semiconductor temperature difference power generation system.

Continuing to refer to fig. 1, specifically, the U-shaped well 1 includes a first well 7, a second well 8 and a horizontal communication well 9, the first well 7 and the second well 8 are both arranged along the vertical direction, the upper ends of the first well 7 and the second well 8 are exposed out of the sea level, the lower ends of the first well and the second well penetrate through the geothermal cover layer of the seabed and are inserted into the geothermal reservoir, the horizontal communication well 9 is arranged in the geothermal reservoir along the horizontal direction, and two end portions of the horizontal communication well 9 are respectively communicated with the lower ends of the first well 7 and the second well 8 to form the U-shaped well 1. The horizontal communication well 9 is a geothermal well, which is provided in a geothermal reservoir, for performing heat exchange.

In particular, conventional geothermal recovery wells are vertical wells and attempts have been made in recent years to recover geothermal heat using horizontal wells with success. The technology of directional wells and horizontal wells is becoming mature day by day, and the obvious economic benefit and the effectiveness for specific oil and gas reservoirs are being more and more widely applied to the development of resources such as petroleum, natural gas, compact sandstone oil and gas, coal bed gas, rock salt and the like.

In order to realize heat exchange in the heat storage layer, the geothermal wells are designed to be directionally and horizontally communicated with the opposite wells, namely the geothermal production wells are a pair of horizontally communicated geothermal wells. The well can be a single-layer horizontal well communication well or a double-layer multi-branch horizontal communication well.

Geothermal drilling and thermoelectric power generation systems in sea areas can be installed and operated on simple offshore drilling platforms such as low-cost pile-inserting offshore platforms. When the geothermal resource accumulation area is overlapped with the oil gas accumulation area, a waste oil production platform can be utilized. Before drilling, well head base plates are firstly installed on the well heads of the first well and the second well. The base plate is used as an auxiliary drilling device for completing the procedures of lifting and drilling, well cementing and well completion, thermoelectric generation/heat exchange tube laying and traction and the like.

The geothermal horizontal communication well group related to the embodiment is formed by communicating a geothermal horizontal well A and a geothermal horizontal well B. Generally designed as two open wells. When the formation conditions are complex, the design can be three open wells. And (5) after the geothermal well enters the thermal reservoir, performing vertical well section cementing. The cement slurry is injected from the drilling tool, flows through the bottom of the well, and returns upwards from the annular space, so that the sealing of the interlayer and the cold water layer is realized. Then, the method enters a first slope increasing section, a slope stabilizing section, a second slope increasing section and a horizontal section. And the track of the well hole is strictly controlled, and accurate target centering is ensured. The construction procedures of the two-branch horizontal well or the three-branch horizontal well are the same. The design of five sections of track, namely 'straight-increasing-stable-increasing-flat' is adopted, so that the complexity of the well track is simplified as much as possible. When the well drilling enters a hot reservoir, casing well cementation is immediately carried out, and cold water and reservoir hot water are prevented from being mixed. In the drilling process of the horizontal well, the thermal storage layer position is predicted and identified in advance according to stratum data, logging while drilling and measurement data, and measurement control of the well track is adjusted in real time. In the horizontal section drilling process of the horizontal well, the basic information before drilling comprises reservoir information (heat storage thickness, sand body communication and the like), adjacent well information (well logging curves, heat storage layer positions, water yield and the like), well body tracks (straight well section length, deflecting section length, horizontal section length and the like).

After the horizontal well A is communicated with the horizontal well B, CO2 well washing operation is firstly carried out to improve the permeability coefficient of the thermal reservoir of the horizontal well section. Then, thermal reservoir cementing is carried out without cement sealing, and the thermal reservoir section is cemented by using a high-strength sieve tube without formation fracturing or perforation completion.

The diameters of the casing and the screen pipe are limited by the maximum curvature radius of the borehole, and the diameter is calculated by using a formula:

in the formula C_mMaximum wellbore curvature in (°)/30m for casing to allow passage; sigma_s-yield strength of the jacket material in MPa; d₀-a casing outer diameter in m; k₁-a safety factor; k₂-thread stress concentration factor.

Specifically, the geothermal/seawater semiconductor thermoelectric generation system further comprises a second thermoelectric generation unit 6, wherein the second thermoelectric generation unit 6 is embedded in the side wall of the second end of the thermoelectric generation tube 2, and the second thermoelectric generation unit 6 is located outside the U-shaped well 1 and is in contact with seawater.

Specifically, the second thermoelectric generation unit 6 is connected to the power management unit 4 through a submarine cable 201 buried in the seabed to transmit electric power to the power management unit 4 for management.

Specifically, the power management unit 4 is electrically connected to a user or a power grid through a main cable 19 for power transmission.

It can be seen that, through setting up the second thermoelectric generation unit that is located low temperature sea water, low temperature sea water in the thermoelectric generation pipe is behind geothermal reservoir and first thermoelectric generation unit, low temperature sea water in the thermoelectric generation pipe is heated up, form high temperature sea water, when high temperature sea water flows through second thermoelectric generation unit, make inside and outside production difference in temperature of second thermoelectric generation unit, and then make second thermoelectric generation unit generate electricity, can utilize the sea water after rising temperature once more effectively through setting up second thermoelectric generation unit, thereby can improve the utilization ratio of the energy effectively, further generate electricity simultaneously through the in-process of first thermoelectric generation unit and second thermoelectric generation unit seawater circulation once more, greatly improved electric energy production efficiency.

Particularly, this embodiment need not to extract secret hot water, has avoided the harm of high salinity element, harmful gas in the secret hot water to human environment, has saved the immersible pump and the power consumption that draw water, has reduced initial stage input cost and running cost.

Specifically, this embodiment is through burying the lower part linkage segment of U type well in the geothermal reservoir of underground depths, in the linkage segment with heat energy conversion electric energy, export the electric energy to ground, saved geothermal water pipeline and lay, avoided the corruption and the scale deposit of hot water pipeline, also significantly reduced anti marine organism and adhered to and the input of protection cost.

Particularly, thermoelectric generation pipe 2 includes HDPE pipe and thermoelectric generation pipeline 200, and the outside of 9 inside and U type wells 1 of horizontal intercommunication well sets up a thermoelectric generation pipeline 200 respectively, and first thermoelectric generation unit 5 and second thermoelectric generation unit 6 set up respectively in two thermoelectric generation pipelines 200, and thermoelectric generation pipeline 200 is used for making the sea water pass through in order to carry out thermoelectric generation.

Specifically, the HDPE pipe is used for communicateing two thermoelectric generation pipelines 200 as an organic whole, and the thermoelectric generation pipeline 200 that is located horizontal intercommunication well 9 is linked together through HDPE pipe and high-order sea reservoir 3 to make the sea water in the high-order sea reservoir 3 get into two thermoelectric generation pipelines 200 by the HDPE pipe in proper order.

Specifically, the HDPE pipe includes a first horizontal section 10, a first vertical section 11, and a second vertical section 13, and the thermoelectric generation pipe 200 includes a horizontal connection section 12 and a second horizontal section 14. The first vertical section 11 is arranged in the first well 7, the horizontal connecting section 12 is arranged in the horizontal communicating well 9, the second vertical section 13 is arranged in the second well 8, two ends of the horizontal connecting section 12 are respectively communicated with the lower ends of the first vertical section 11 and the second vertical section 13, and the horizontal connecting section 12 is positioned in the geothermal reservoir; the first horizontal section 10 is used for communicating the high-level sea reservoir 3 with the first vertical section 11, so that normal-temperature sea water in the high-level sea reservoir 3 enters the first vertical section 11.

Specifically, one end of the first horizontal segment 10 is communicated with the bottom surface of the high-level sea water reservoir 3, and a water outlet is arranged on the bottom surface of the high-level sea water reservoir 3, so that the seawater flows into the first horizontal segment 10; the end of the second horizontal segment 14 extending into the sea is provided with a water outlet to discharge the seawater in the thermoelectric generation pipeline 200 into the sea.

Referring to fig. 2, a cable is arranged in a side wall of the first vertical section 11, the cable includes a positive cable 28 and a negative cable 29, the first thermoelectric generation unit 5 is embedded in a side wall of the horizontal connection section 12, and after the normal temperature seawater flows through the horizontal connection section 12 and generates electricity through the first thermoelectric generation unit 5, the generated electricity is transmitted to the power management unit 4 through the cable, that is, the first thermoelectric generation unit 5 and the power management unit 4 are electrically connected together through the positive cable 28 and the negative cable 29. A connection cable 202 is provided in the first well 7 so that the positive cable 28 and the negative cable 29 are electrically connected to the power management unit 4 therethrough.

Specifically, the second horizontal section 14 is located outside the second well 8, one end of the second horizontal section is communicated with the upper end of the second vertical section 13, the second horizontal section 14 is arranged on the sea floor, the second thermoelectric generation unit 6 is embedded in the side wall of the second horizontal section 14, seawater flowing through the horizontal connection section 12 is subjected to heat exchange through the geothermal reservoir, flows through the second vertical section 13 and the second horizontal section 14 and is discharged, and when the seawater subjected to heat exchange flows through the second horizontal section 14, the second thermoelectric generation unit 6 generates power according to the internal and external temperature difference of the second horizontal section 14 and transmits the generated power to the power management unit 4.

Specifically, a first temperature difference power generation unit 5 is embedded in the side wall of the horizontal connection section 12, the horizontal connection section 12 is arranged in the horizontal communication well 9, the horizontal connection section 12 is located in the geothermal reservoir, and the horizontal connection section 12 is used for enabling low-temperature seawater in the high-level seawater reservoir 3 to flow through so that the first temperature difference power generation unit 5 generates power through the internal and external temperature difference of the horizontal connection section 12; a lead is arranged in the side wall of the first vertical section 11 and is used for being electrically connected with the power management unit 4; first vertical section 11 sets up in first well 7 along vertical direction, second vertical section 13 sets up in second well 8 along vertical direction, horizontal connection section 12 sets up in horizontal intercommunication well 9 along horizontal direction, the both ends of horizontal connection section 12 are connected with the lower extreme of first vertical section 11 and second vertical section 13 respectively, the one end of first horizontal segment 10 is connected with high-order sea reservoir 3, the other end is connected with the upper end of first vertical section 11, in order to carry the sea water in the high-order sea reservoir 3 to horizontal connection section 12, the one end of second horizontal segment 14 is connected with the upper end of second vertical section 13, second horizontal segment 14 sets up on the seabed.

As shown in fig. 3 and 4, specifically, the thermoelectric generation pipeline 200 includes an inner heat conduction insulating layer 20 and an outer heat conduction insulating layer 21 of an annular structure, the inner heat conduction insulating layer 20 is disposed through the outer heat conduction insulating layer 21, and the inner heat conduction insulating layer and the outer heat conduction insulating layer are coaxially disposed, the first thermoelectric generation unit 5 and the second thermoelectric generation unit 6 are respectively disposed between the inner heat conduction insulating layer 20 and the outer heat conduction insulating layer 21, and the first thermoelectric generation unit 5 and the second thermoelectric generation unit 6 are respectively disposed in an annular arrangement with the inner heat conduction insulating layer 20 and the outer heat conduction insulating layer 21. The inner and outer heat conductive insulating layers 20 and 21 are integrally manufactured with the first and second thermoelectric generation units 5 and 6 so that the thermoelectric generation pipeline 200 forms a complete tubular structure.

Specifically, the outer heat conducting insulation layer 21 is internally provided with a braided framework steel wire 27 so as to improve the structural strength and tensile property of the pipeline. The thermoelectric generation pipeline 200 is internally provided with a positive cable 28 and a negative cable 29.

As shown in fig. 5, specifically, the first thermoelectric generation unit 5 and the second thermoelectric generation unit 6 respectively include a plurality of thermoelectric generation modules 50, the plurality of thermoelectric generation modules 50 are uniformly arranged between the inner heat-conducting insulation layer 20 and the outer heat-conducting insulation layer 21, and the thermoelectric generation modules 50 are arranged in two rows side by side. The positive pole of the thermoelectric generation module 50 is connected with the positive cable 28 through the positive pole connecting line 281, the negative pole is connected with the negative cable 29 through the negative pole connecting line 291, and the thermoelectric generation modules 50 are connected in series.

As shown in fig. 3, 4, 6 and 7, in particular, the thermoelectric generation module 50 includes a thermoelectric arm layer 24, an inner copper sheet layer 22 and an outer copper sheet layer 23, the thermoelectric arm layer 24 is disposed between the inner copper sheet layer 22 and the outer copper sheet layer 23, and the inner copper sheet layer 22 and the outer copper sheet layer 23 respectively include a plurality of copper sheets 25.

Specifically, the thermoelectric arm layer 24 includes a plurality of P-type thermoelectric arms 31 and N-type thermoelectric arms 30, the inner copper sheet layer 22 and the outer copper sheet layer 23 respectively include a plurality of copper sheets 25, the plurality of P-type thermoelectric arms 31 and N-type thermoelectric arms 30 are alternately arranged, the upper end of each two adjacent P-type thermoelectric arms 31 and N-type thermoelectric arms 30 is simultaneously connected with one copper sheet 25, the lower end of each two adjacent P-type thermoelectric arms 31 and N-type thermoelectric arms 30 is respectively connected with two copper sheets 25, the plurality of P-type thermoelectric arms 31 and N-type thermoelectric arms 30 are connected in series through the copper sheets 25 arranged at the upper end and the lower end of each P-type thermoelectric arm 31 and N-type thermoelectric arms 30 are respectively connected with the negative cable 29 and the positive cable 28 for power transmission.

Specifically, when the P-type thermoelectric arms 31 and the N-type thermoelectric arms 30 are installed, the P-type thermoelectric arms 31 and the N-type thermoelectric arms 30 are respectively arranged at equal intervals and equal intervals, the heat insulating potting adhesive 26 is filled between every two adjacent P-type thermoelectric arms 31 and N-type thermoelectric arms 30, and the heat insulating potting adhesive 26 is filled between every two similar adjacent copper sheets 25 to ensure the performance of the P-type thermoelectric arms 31 and N-type thermoelectric arms 30, so that the P-type thermoelectric arms 31 and N-type thermoelectric arms 30 can work normally.

Particularly, the thermoelectric generation tube, the cable and the thermoelectric generation unit are integrally manufactured, a semiconductor thermoelectric generation/seawater conveying/heat exchange/cable four-in-one pipe structure can be formed, and the structure of the system is greatly simplified.

Specifically, heat is typically transferred by three transport mechanisms, thermal conduction, thermal convection, and thermal radiation. Thermal conduction is a heat transfer phenomenon caused by molecular thermal motion due to a temperature gradient; the thermal convection is a heat transfer process caused by relative displacement between parts of fluid due to macroscopic motion of the fluid and is divided into forced convection caused by pressure gradient and natural convection caused by density gradient; thermal radiation is a heat transfer mode resulting from the quadratic gradient of temperature by dissipating heat energy outward in the form of electromagnetic radiation.

Specifically, in order to increase the electrical reliability of the four-bit integrated tube and reduce the volume of the thermoelectric generation device, the thermoelectric couple integrated system is adopted in the embodiment. Namely, the thermoelectric generation pieces are integrated together to form the tubular thermoelectric generation device. And the underground construction difficulty is reduced. The four-in-one pipe is not only a temperature difference power generation device, but also a seawater flowing pipeline, and has the functions of a heat exchanger and a cable. Its versatility determines the multilayer structure of the tube. The four-bit integrated tube needs to have the following performance indexes: the sealing gasket has excellent sealing performance; the bearing can bear the adaptive pressure and axial tensile load; thirdly, the requirements of seawater corrosion resistance and scaling resistance can be met; fourthly, the temperature use environment requirement must be met; stable performance in service life, aging resistance, easy bending and convenient assembly and connection.

The HDPE pipe has the main function of conveying cooling seawater, the cable is further arranged in the HDPE pipe, the electric energy conveying function is achieved, the outer diameter of the HDPE pipe is the same as that of the thermoelectric generation/seawater conveying/heat exchange/cable four-in-one pipe, the inner diameter of the HDPE pipe is larger than that of the four-in-one pipe, and the HDPE pipe and the four-in-one pipe are connected through reducing.

The semiconductor thermoelectric power generation/seawater transportation/heat exchange/cable four-position integrated pipe has the characteristics of necessary tensile strength, compressive strength, shear strength, heat conduction (or heat insulation), electric conduction (or insulation) and the like, and can bear larger hydrostatic pressure in the deep part of the geothermal well.

Most of the commercially purchased thermoelectric power generation devices are square or round modules, and when the thermoelectric power generation device is used, one surface of the thermoelectric module is fixed on a heat source, and the other surface of the thermoelectric module is attached with a cold source, so that heat transmitted by a thermoelectric couple is dissipated. The edges of the thermoelectric devices are connected by screws, and the module is clamped and fixed between the heat source and the cold end. In fact, the contact interface between the thermoelectric device and the cold and hot ends is uneven, and a heat conducting interface material needs to be additionally added to enable the thermoelectric device and the cold and hot ends to be tightly attached so as to improve the heat transfer of the thermoelectric device. Secondly, the thermoelectric module is fastened between the cold end and the hot end by screws, and the phenomena of crushing the power generation module, bending the heat transfer sheet and the like often occur in the screw locking process, so that the reliability of the thermoelectric power generation assembly is poor. In addition, because some thermoelectric materials have large expansion coefficients, when a ceramic plate is used as the cover plate, the cover plate is easy to burst due to expansion, which causes the open circuit fault of the thermocouple, so the embodiment selects the heat-conducting insulating rubber with elasticity and toughness as the material of the pipe wall.

The thermocouple in this example was a bismuth telluride-based commercial thermoelectric material. 120 pairs of bismuth telluride-based P-type and N-type semiconductor thermocouples are serially connected through copper sheets to be packaged into a thermoelectric power generation unit, and heat insulation pouring sealant is filled in gaps around the thermocouples for sealing. A plurality of semiconductor temperature difference power generation units are connected in parallel through cables to form a temperature difference power generation array and then are embedded into a rubber pipe wall with certain elasticity.

As the semiconductor thermoelectric generation unit, the thermoelectric effect formed by the cold/hot ends of the thermoelectric couple is utilized, and the power generation performance of the semiconductor thermoelectric generation unit is only related to the heat transferred by the thermoelectric couple and is not related to the heat exchange quantity of a gap outside the thermoelectric couple, so that the heat transfer of the thermoelectric couple is increased as much as possible, and the conduction of other ineffective heat is avoided. The smaller the flow resistance of the seawater in the semiconductor thermoelectric generation/seawater conveying/heat exchange/cable four-in-one pipe is, the better the seawater flow resistance is, and the smooth rubber pipe with small hydraulic friction coefficient is selected as the inner layer.

Due to the function of the heat exchanger, the rubber four-position integrated pipe has certain heat conductivity. The thermoelectric power generation/heat exchange tube is characterized in that cooling seawater flows longitudinally along the heat exchange tube, the temperature longitudinal change is large, and the length is far greater than the section size. The semiconductor thermoelectric generation characteristic determines that a plurality of thermoelectric generation units form a semiconductor thermoelectric generation array (pipe) to carry out large-scale power generation. The wall of the thermoelectric generation pipeline has moderate heat conductivity coefficient so as to ensure that all the thermocouples have equal or similar temperature difference, namely the heat conductivity of the outer wall of the thermoelectric generation pipeline is not larger and better. If the heat conductivity coefficient is too large, the seawater in the first section of pipe is heated quickly, the first section of semiconductor temperature difference power generation array (pipe) realizes maximum temperature difference power generation, the temperature difference gradually decreases towards the tail end until the temperature difference is zero, the temperature difference power generation unit at the tail end loses the power generation function, and the total power generation efficiency is very low. Ideally, heat is transferred only through the thermocouple, and the outer gap of the thermocouple is thermally insulated. Therefore, the total heat conductivity coefficient of the pipe wall of the thermoelectric generation array needs to be solved according to the Ansys Fluent fluid simulation, so that the total heat conductivity coefficient of the pipe wall of the thermoelectric generation array is close to the solved optimal heat conductivity coefficient. The integral temperature field of the temperature difference power generation system is optimized, and the supplement heat outside the pipe is approximately equal to the absorption heat inside the pipe. The ratio of the power of the load to the heat absorbed by all thermocouples per unit time is the conversion efficiency of the thermoelectric generator.

A heat exchange calculation model and numerical simulation display of an infinite-length-line horizontal circular tube in a seepage reservoir show that the higher the seepage speed of a heat reservoir is, the higher the heat exchange efficiency is. In addition, the influence of geothermal water seepage on the heat exchange performance of the thermoelectric power generation pipeline is gradually reflected after a long time, the heat exchange pipe is hardly influenced by the seepage within a certain time, and the influence of the seepage is gradually shown later. This is because the rate of hot water seepage from the reservoir is generally slow, taking time to remove heat from areas that have a significant effect on the heat exchange tubes, with less seepage taking longer.

The semiconductor thermoelectric generation array (tube) or the cable has insulation property according with the geothermal power generation temperature and pressure condition at the deep part of the earth crust. Meanwhile, the pipe has higher tensile strength, pressure resistance, compression resistance and shear strength.

The four-in-one rubber pipe mainly comprises an inner rubber layer, a thermoelectric generation device layer and an outer rubber layer from inside to outside, wherein a braided framework steel wire is embedded in the outer rubber layer.

An inner glue layer: the fluorine rubber 246 is used as a matrix, and silicon nitride is compounded and filled. The fluororubber 246/silicon nitride composite material is prepared by taking 2-micron, 7-micron and 30-micron silicon nitride particles as heat-conducting fillers and fluororubber 246 as an organic matrix through the processes of mixing, vacuum treatment, curing and the like. Silicon nitride particles of 2 μm, 7 μm and 30 μm in a mass ratio of 1: 3: 6 filling fluororubber 246, the filling amount is 92.5%, the thermal conductivity of the fluororubber 246 composite material is 2.82W/(m.K), the breakdown strength is 15.19kV/mm, and the plasticity is 0.26.

And the thermoelectric power generation device layer is of an interactive structure consisting of a bismuth telluride thermoelectric block, heat insulation potting adhesive, a copper sheet and a welding layer. A plurality of semiconductor thermoelectric generation units are connected in parallel to form a thermoelectric generation device layer.

Copper sheet (flow deflector): the copper sheet is adopted because the copper sheet has high thermal conductivity and low Seebeck coefficient and Peltier coefficient, the joint of the copper sheet and the end part of P, N is convenient for realizing the addition of a large amount of heat, the temperature difference of the joint is small, the heat flow density of the thermoelectric power generation sheet is improved, and the P, N semiconductor cold and hot end can form the maximum temperature gradient.

The output voltage of the semiconductor temperature difference power generation module gradually rises along with the increase of the temperature difference, and the increasing speed of the output voltage gradually becomes smaller and finally tends to be constant along with the continuous increase of the temperature difference. The output power is gradually increased in a parabolic form along with the increase of the side length of the cross section of the thermoelectric element, and the thermoelectric generation conversion efficiency is almost unchanged along with the increase of the cross section of the thermoelectric element. The output power is gradually reduced along with the increase of the arm length, the thermoelectric power generation conversion efficiency is slowly increased, in order to ensure the balance of the output power and the conversion efficiency, the arm length can not be too large or too small, and the shape and the size of the thermoelectric material and the thermoelectric material are selected according to an orthogonal test.

A thermocouple: bismuth telluride (Bi2Te3) based material. Bi2Te3 in nature often contains isomorphism impurities, is mainly produced in gold-containing quartz vein and tellurium-containing ore deposits with low sulfur content, is mostly high-medium temperature hot liquid ore deposits, and is also produced in basic and super-basic rock copper nickel sulfide ore deposits. However, Bi2Te3 used for thermoelectric power generation is an artificial crystal by precisely controlling the relative contents of Bi, Te, Sb and other elements. When Bi, Te, Sb are present in excess in Bi2Te3, it will naturally become a P-type or N-type thermoelectric semiconductor material. And filling and reinforcing gaps among the bismuth telluride blocks of the thermoelectric generation device layer to improve the compressive strength of the thermoelectric generation device layer. In this example, bulk bismuth telluride-based thermoelectric material was purchased, and the length × width × height was 4 × 4 × 2.5mm, the thermoelectromotive force was 230 μ V/K, the thermal conductivity was 16 × 103W/m.k, the shear strength was about 5MPa, the optimum value was 3, the melting point temperature was 585 ℃, and the density was 7.8587g/cm 3.

Welding layers: the material is Sn-Sb alloy, the yield strength of the Sn-Sb alloy is 26MPa, the strength limit is 41MPa, and the elongation is 38%.

The pouring sealant comprises the following components in formula: 107 silicone rubber, nanoscale calcium carbonate, precipitated calcium carbonate, 201 silicone oil, methyltributanone oxime silane, 550 coupling agent, 550 organotin, 100:11:11:16:7:1: 0.5. Firstly, stirring 107 silicon rubber, nano calcium carbonate, light calcium carbonate and 201 silicon oil into a mucilage, and grinding and dispersing the mucilage into uniform mucilage by using a three-roller grinding machine; and (3) carrying out vacuum heating (95 ℃) treatment for 20min, adding methyl tributyl ketoxime silane, 550 coupling agent and organic tin, stirring and reacting for 15min to obtain the heat-insulating sealant with good fluidity. And encapsulating the sealant between the gaps of the thermocouples and curing. The main parameters are density 1.05, viscosity 0.8 x 105 mPa.s, using temperature-50-250 ℃, surface resistivity not less than 1.5 x 1013 omega, volume resistivity not less than 1.7 x 1015 omega and thermal conductivity 0.083W/m.K. The service life of the encapsulating material obtained by an accelerated aging test and an Arrhenius method extrapolation calculation is 25 years.

③ outer adhesive layer: the heat exchange tube is composed of a tube body reinforcing protective layer and a heat exchange layer for heat storage, the main components of the tube body reinforcing protective layer and the heat exchange layer are the same as those of an inner adhesive layer, but a reinforced woven skeleton steel wire structure layer is added in the middle of the tube body reinforcing protective layer, so that the tensile strength, the pressure bearing capacity and the impact resistance of the tube body are enhanced, and the longitudinal heat conductivity of the tube body is improved. The reinforcing layer is braided with over-moulded steel wires at an angle of 54 deg. 44'. The high molecular adhesive layer formed by the metal wire coated with the heat-resistant high-strength adhesive is fused with the composite pipe wall of the fluororubber 246 to form an integral structure, and no gap interface is formed between the composite pipe wall and the reinforcing layer.

Specifically, as shown in fig. 1 and 8, the side of the high-level sea reservoir 3 facing the sea is provided with a one-way gate 15 and a wave guide wall 16, the one-way gate 15 is used for allowing sea water to enter the reservoir when the tide rises, and the wave guide wall 16 is used for introducing sea waves into the reservoir.

Specifically, the bottom surface of the high-level sea water reservoir 3 is provided with a water outlet 17 for communicating with a first end of the thermoelectric generation tube 2, and a water outlet 18 is provided at a second end of the thermoelectric generation tube 2 to discharge the sea water in the high-level sea water reservoir 3 into the sea.

Specifically, when the high-level sea reservoir is constructed, the high-level sea reservoir is preferably suitable for a bay coast, a coast with alternate promontory and bay and zigzag coast line, and a steep water depth of the coast at the promontory corner, wherein wave energy is radiated; the water in the bay is shallow and moderate, and the waves are dispersed in the bay. And the construction length of the reservoir dam is reduced as much as possible. And according to the quantity of the geothermal well groups and the total flow of the seawater of each inverted siphon well. The xingli reservoir capacity of the high-level sea reservoir is determined according to the historical sea hydrological statistical data and the total quantity of the cooling seawater demand.

Before the sea reservoir is selected, ocean hydrological investigation and measurement should be carried out, relevant information such as ocean current, sea level, wind speed and direction, waves, tidal current and the like of a sea water/geothermal thermoelectric power generation sea area is found out, and dam elevation is designed to at least meet 2 conditions: firstly, the height reached by storm surge is more than 50 years, and secondly, the flow of cooling seawater with the capacity of more than 30 days (twice heavy tide) is used for making the pool at the safe water level.

The storage capacity calculation can be carried out by adopting a proper method and a proper tool according to the topographic cross sectional map of the site selection area or the topographic map of the sea area. When designing the reservoir, the size of the reservoir capacity at a certain water level needs to be calculated, and a relation curve between the water level and the reservoir capacity or a relation curve between the water level and the area is drawn. The calculation of the library capacity is generally performed by a contour method. The storage capacity is a volume of water that can be stored in the reservoir. When calculating, the area enclosed by each contour line and the axis of the dam is firstly obtained, then the average value of two adjacent areas is multiplied by the height difference, the volume between the two contour lines is obtained, and the sum of the volumes is the storage capacity of the reservoir.

At least 1 one-way gate is built on one side of the reservoir dam facing the sea, only seawater is allowed to enter the reservoir when the tide rises, and the gate is automatically closed when the seawater flows out of the reservoir, so that tidal energy and wave energy are converted into potential energy of the seawater in the high-level reservoir. The water level of the reservoir can be more than or equal to the maximum tide level by the secondary heavy tide every month. In addition, a drainage channel needs to be reserved in the reservoir, and the phenomenon that the normal water storage level exceeds the highest allowable water level due to factors such as storm surge is prevented.

According to the coastal terrain conditions, wave energy is concentrated and is vertical to the normal wave direction at selected sites through a digital model, at least two wave guiding walls are built to form a wave-crossing contraction wave channel which is arranged in a fan shape, and wave energy is captured by the gradually contracted wave guiding walls and is amplified in the gradually contracted wave guiding walls until the wave energy crosses the tops of the wave guiding walls and enters a high-level sea reservoir. The overtopping process of the slope dike is extremely complex, and the influence factors are many. In order to reasonably determine the reservoir capacity and the corresponding reservoir water level, the overtopping amount is calculated by means of physical model tests and numerical simulation according to the characteristic water level elevation of the reservoir before the overtopping type shrinkage wave (slope) road is built, and the reservoir capacity and the corresponding reservoir water level are reasonably determined. The wave-crossing quantity influence factors comprise wave elements and an embankment body structure, and the wave elements comprise wave height, period and other factors; the embankment body structure comprises an embankment top height, a slope shoulder width, a slope shoulder height, a slope ratio, a protective surface smoothness and the like.

The purpose of building a high-level reservoir is to provide enough seawater potential energy for cooling seawater pipes and change the seawater potential energy into the flow velocity of seawater in the pipelines. The water flow in the inverted siphon is pressure flow, and the flow rate is calculated according to the following formula:

i.e. ω ═ Q²/2gzμ

Wherein, the flow rate of the Q-inverted siphon pipe is m 3/s; water passing cross-sectional area, m, of omega-inverted siphon²(ii) a z-water head difference m upstream and downstream of the inverted siphon; mu-flow coefficient.

Particularly, ocean energy and geothermal energy are low-grade and huge total energy, and are combined to become comprehensively utilized electric energy, so huge economic benefits and social benefits can be generated. To the not enough of current geothermal power generation, thermoelectric generation technique, this embodiment provides above-mentioned thermoelectric generation system, can solve the not enough of prior art effectively.

The geothermal/seawater semiconductor temperature difference power generation system of the embodiment has at least the following advantages:

this embodiment need not to extract secret hot water, has avoided the harm of high salinity element, harmful gas in the secret hot water to human environment, has saved the immersible pump and the power consumption that draw water, has reduced initial stage input cost.

In order to simplify the structure of the power generation system, the thermoelectric power generation device, the heat exchanger, the cooling device and the cable are combined into a whole to form the thermoelectric power generation/heat exchange tube. In order to overcome the problem that the thermoelectric generation/heat exchange tube bears larger pressure underground, the thermoelectric generation/heat exchange tube structure and the material of the embodiment can bear the temperature and pressure environment of 270 ℃ and 53 MPa.

The seawater/geothermal thermoelectric power generation system of the embodiment utilizes the geothermal energy resources of the sea area, supplements normal-temperature seawater for the high-level reservoir by using tidal energy and wave energy, and uses seawater to cool the thermoelectric power generation device, thereby realizing the continuous and stable power generation of the semiconductor thermoelectric power generation system.

The geothermal thermoelectric power generation is carried out through the in-situ heat exchange of the horizontal communication well, so that the energy consumption of a water pump for pumping geothermal water is saved, and the whole recharge system consisting of the geothermal recharge well, the water quality purification device, the exhaust equipment, the pressure pump and the communication device is also saved. The geothermal utilization process is simplified, and the high cost investment of pumping water, water quality treatment, geothermal recharge and the like is reduced. According to the measurement and comparison, the construction cost of the geothermal energy power station is reduced by more than 73% compared with that of the traditional geothermal energy power station.

The embodiment mainly converts the heat energy into the electric energy in the horizontal communication well deep underground, outputs the electric energy to the ground, saves geothermal water pipelines and laying thereof, and avoids corrosion and scaling of the hot water pipelines. The investment of marine organism adhesion resistance and protection cost is greatly reduced.

The power generation technology combining ocean tidal energy, wave energy and sea area geothermal energy comprehensively utilizes various energies or resources, and realizes the power generation technology without energy consumption and unattended operation.

This embodiment normal position heat transfer utilizes geothermal energy, has broken through the traditional utilization mode that must take out hot water utilization geothermal energy under the ground, provides a new thinking for geothermal energy utilization mode.

In the horizontal communication well of the underground heat reservoir, the thermoelectric generation/heat exchange tube is arranged perpendicular to the seepage direction of underground water, so that heat exchange is forced outside the thermoelectric generation/heat exchange tube through seepage and convection. The seawater flowing in the pipe absorbs heat. The heat exchange efficiency is improved by a forced convection heat transfer mode.

By means of inverted siphoning formed by the high-level sea reservoir and the horizontal communication well, stable and continuous circulation of cooling seawater of the horizontal well temperature difference power generation system is achieved, and stable temperature difference is formed between the cooling seawater and a thermal reservoir. In addition, under normal operating conditions, a stable thermal cycle can be achieved: after the seawater in the pipeline exchanges heat through the horizontal well heat reservoir, the temperature of the seawater rises, the seawater in the second well forms an obvious temperature (density) gradient, and even if the seawater does not flow forcibly through inverted siphon, buoyancy-driven free convection can occur due to density change.

The temperature difference power generation pipeline is additionally arranged on the seabed of the temperature discharge seawater flowing out of the second well base plate, so that the heat energy can be utilized in a gradient manner. The embodiment has high geothermal energy utilization rate and low temperature of warm discharge seawater, and the influence of discharge on the marine environment is small.

The embodiment does not extract underground hot water, has no problem of water environmental pollution, and protects underground water resources. The geological disasters such as ground subsidence and collapse, ground cracks, underground water level falling funnels and the like caused by high-strength exploitation of geothermal water are avoided.

A tubular thermoelectric power generation device is adopted, flowing seawater is arranged in a pipe, seepage hot water of a heat reservoir layer is arranged outside the pipe, and forced heat exchange is carried out inside and outside the pipe. The underground heat storage system is beneficial to in-situ heat exchange/thermoelectric power generation in the underground heat storage layer, and improves the heat exchange efficiency.

According to the embodiment, the water level of the high-level sea reservoir is improved by utilizing low-grade energy such as tides and waves, so that the equipment investment such as an initial water pump is reduced, and the power cost of daily operation of a power station is saved.

The embodiment does not need extra power and energy to provide power for the power generation equipment, completely depends on natural phenomena and in-situ natural resources to generate power, and has low power generation operation cost.

The semiconductor thermoelectric generation/seawater transportation/heat exchange/cable four-in-one pipe design of the embodiment greatly reduces the volume of the thermoelectric generation system and increases the reliability of the thermoelectric generation system. The installation and the maintenance are more convenient.

The traditional geothermal well needs to be provided with a pump chamber sleeve, otherwise, a large-displacement submersible pump cannot be driven into the geothermal well to pump water, and therefore a large-diameter well with higher cost needs to be drilled. Also, as the ground water level decreases year by year, the depth of the pump chamber pipe becomes greater. The maintenance cost of the vertical shaft in the embodiment is far lower than that of a pumping geothermal well.

In the past, geothermal power generation is to convert heat energy into mechanical energy and then convert the mechanical energy into electric energy. The total conversion efficiency is not high after 2 times of energy conversion from heat energy to electric energy. The embodiment cascade utilizes heat energy to carry out thermoelectric generation, thereby improving the heat energy utilization rate.

Most of the traditional thermoelectric power generation device structures are formed by welding thermocouple arms on a copper-clad ceramic plate, the ceramic plate fixes thermocouples, and four corners of the ceramic plate are fixed by screws. However, under the huge hydrostatic pressure of a deep well, ceramic plates with higher hardness are prone to crush thermocouples with lower hardness or to have broken corners. In the embodiment, the thermocouple is welded on the copper sheet and is embedded into the elastic composite rubber pipe wall, so that the failure rate of the thermoelectric power generation device is reduced. In addition, the thermocouple is under the static pressure, so that the copper sheet is in closer contact with the thermocouple, and the interface resistance and the thermal resistance are reduced. The heat flux density across the thermocouple is increased.

Referring to fig. 9, in another preferred implementation manner based on the foregoing embodiment, unlike the foregoing embodiment, the power management unit includes a control module, and the control module is configured to control a flow rate of seawater in the thermoelectric generation tube according to the generated power of the first thermoelectric generation unit and the temperature difference between the inside and the outside of the thermoelectric generation tube.

Particularly, the pipeline inside wall that first thermoelectric generation unit located is provided with first temperature sensor, promptly, first temperature sensor sets up on the inside wall of thermoelectric generation pipe, is provided with second temperature sensor on the pipeline outside wall that first thermoelectric generation unit located, promptly, second temperature sensor sets up on the lateral wall of thermoelectric generation pipe. The first temperature sensor is used for acquiring the seawater temperature T1 inside a pipeline where the first thermoelectric power generation unit is located in real time, the second temperature sensor is used for acquiring the temperature T2 of a geothermal reservoir outside the pipeline where the first thermoelectric power generation unit is located in real time, the control module is electrically connected with the first temperature sensor and the second temperature sensor, and the control module is used for acquiring T1 and T2 and calculating the temperature difference T0 between T1 and T2.

Specifically, a water outlet on the bottom surface of the high-level sea reservoir is provided with a flow-adjustable water pump, a flowmeter is arranged in the first horizontal section, the flow rate L0 of the seawater in the thermoelectric generation tube is detected through the flowmeter, and the flow rate of the seawater in the thermoelectric generation tube is adjusted through the adjustable water pump.

Specifically, the power management unit further comprises a thermoelectric generation control module and a transformer substation, wherein the thermoelectric generation control module is used for adjusting and controlling the water pump and is also used for managing and controlling the thermoelectric generation process.

Specifically, the substation is used for acquiring the power generation amount P0 of the first thermoelectric power generation unit with the preset time length S0 and sending the acquired data to the control module.

Specifically, the control module is used for adjusting the flow speed L0 of the seawater in the thermoelectric generation pipe according to the power generation amount P0 of the first thermoelectric generation unit.

Specifically, a first preset power generation amount P1, a second preset power generation amount P2, a third preset power generation amount P3 and a fourth preset power generation amount P4 are preset in the control module, and P1 is more than P2 and more than P3 and more than P4; a first preset seawater flow rate L1, a second preset seawater flow rate L2, a third preset seawater flow rate L3 and a fourth preset seawater flow rate L4 are preset in the control module, and L1 is more than L2 and more than L3 and more than L4.

Specifically, the control module is further configured to, after acquiring the power generation amount P0 of the first thermoelectric generation unit, set the flow rate of the seawater in the thermoelectric generation tube according to the relationship between P0 and each preset power generation amount:

when P0 is not more than P1, the flow speed of the seawater in the thermoelectric generation tube is set to be L1;

when P1 is more than P0 and less than or equal to P2, setting the flow speed of the seawater in the thermoelectric generation tube to be L2;

when P2 is more than P0 and less than or equal to P3, setting the flow speed of the seawater in the thermoelectric generation tube to be L3;

when P3 is more than P0 and less than or equal to P4, the flow speed of the seawater in the thermoelectric generation tube is set to be L4.

Specifically, the flow velocity of the seawater in the thermoelectric generation tube is set according to the generated energy of the first thermoelectric generation unit, so that the flow velocity of the seawater in the tube can be controlled timely according to the generated energy, the flow velocity of the seawater can be increased when the generated energy is increased, the heat exchange efficiency in the tube can be increased, and the generated energy can be further increased.

Specifically, a first preset temperature difference T1, a second preset temperature difference T2, a third preset temperature difference T3 and a fourth preset temperature difference T4 are preset in the control module, and T1 is more than T2 and less than T3 and less than T4; the control module is also preset with a first preset flow rate correction coefficient a1, a second preset flow rate correction coefficient a2, a third preset flow rate correction coefficient a3 and a fourth preset flow rate correction coefficient a4, wherein a1 < a2 < a3 < a 4.

Specifically, the control module is further configured to, after the flow rate of the seawater in the thermoelectric generation tube is set to the ith preset seawater flow rate Li, i is 1, 2, 3, 4, obtain the internal and external temperature difference T0 of the thermoelectric generation tube in real time, and select a flow rate correction coefficient to correct the set ith preset seawater flow rate Li according to the relationship between the internal and external temperature difference T0 of the thermoelectric generation tube and each preset temperature difference:

when T0 is not more than T1, a first preset flow rate correction coefficient a1 is selected to correct the ith preset seawater flow rate Li, and the corrected seawater flow rate in the thermoelectric generation tube is Li a 1;

when T1 is larger than T0 and is not larger than T2, a second preset flow rate correction coefficient a2 is selected to correct the ith preset seawater flow rate Li, and the corrected seawater flow rate in the thermoelectric generation tube is Li a 2;

when T2 is larger than T0 and is not larger than T3, a third preset flow rate correction coefficient a3 is selected to correct the ith preset seawater flow rate Li, and the corrected seawater flow rate in the thermoelectric generation tube is Li a 3;

and when T3 is more than T0 and less than or equal to T4, selecting a fourth preset flow rate correction coefficient a4 to correct the ith preset seawater flow rate Li, wherein the corrected seawater flow rate in the thermoelectric generation tube is Li a 4.

Particularly, the correction coefficient is selected according to the internal and external temperature differences of the thermoelectric generation tube to correct the flow velocity of the seawater, the change of the flow velocity of the seawater can be adjusted according to the temperature difference condition in real time, the internal and external temperature differences of the thermoelectric generation tube can be kept at the optimal temperature difference value all the time, the generated energy of the first thermoelectric generation unit can be effectively improved, the first thermoelectric generation unit is enabled to be in the optimal working state all the time to carry out thermoelectric generation, and the generation efficiency of the first thermoelectric generation unit is further improved.

Specifically, the flow velocity of the seawater in the thermoelectric power generation tube is set and corrected at the next time based on the power generation amount of the first thermoelectric power generation unit at the previous time and the difference between the internal temperature and the external temperature of the thermoelectric power generation tube.

In another preferred embodiment based on the above embodiment, the present embodiment provides a geothermal/seawater semiconductor thermoelectric power generation method, and the method of the present embodiment uses the geothermal/seawater semiconductor thermoelectric power generation system in the above embodiment to perform real-time power generation.

Referring to fig. 10, the geothermal/seawater semiconductor thermoelectric power generation method according to the present embodiment includes the following steps:

step a: introducing seawater into a high-level seawater reservoir, and enabling normal-temperature seawater in the high-level seawater reservoir to flow into the ocean after flowing through a thermoelectric generation tube according to the height difference between a first end and a second end of the thermoelectric generation tube;

step b: when normal-temperature seawater flows through a first temperature difference power generation unit in a geothermal reservoir, power generation is carried out after temperature difference is generated between the inner side and the outer side of the first temperature difference power generation unit;

step c: the normal-temperature seawater flows through the geothermal reservoir and then is heated into high-temperature seawater, the second end of the temperature difference power generation pipe is provided with a second temperature difference power generation unit, and when the high-temperature seawater flows through the second temperature difference power generation unit, the inside and the outside of the second temperature difference power generation unit generate temperature difference and then power generation is carried out;

step d: and the power generated by the first temperature difference power generation unit and the second temperature difference power generation unit is transmitted to a power management unit, and is transmitted to a user or is merged into a power grid through the power management unit.

Specifically, the sea geothermal energy is a resource with extremely low utilization rate and huge reserves at the present stage, and the embodiment utilizes the part of the resource which has no other purposes for carrying out thermoelectric power generation and has little influence on the marine environment. Meanwhile, the geothermal temperature difference power generation of the embodiment depends on natural energy to enable seawater to flow for automatic heat exchange, no additional water pump power is needed, and the operation cost is low. The sea geothermal thermoelectric power generation has the characteristics of no mechanical motion, no noise, no maintenance, no pollution, high reliability and long service life. Accords with the national environmental protection standard and policy, does not generate secondary pollution, and belongs to the field of resource comprehensive utilization encouraged by the nation.

Furthermore, the power generation equipment is simple, the construction is easy, easily-damaged and easily-consumed materials and other energy sources are basically not used, the power generation equipment is easy to realize under the condition of the prior art, the heat energy is directly converted into the electric energy, the complex process that the heat energy is firstly converted into mechanical energy and then converted into the electric energy is avoided, and the heat energy utilization rate is high.

The above embodiments will be described in detail by taking a research on a geothermal field seawater/thermoelectric power generation test in the east and east China sea area of Shandong province as an example.

Geothermal exploration evaluation

Through the geological exploration of the geothermal field, the geothermal field in the eastern campsite is positioned in the eastern northwest depression geohot area with the area of about 550km²Belongs to sedimentary basin type hydrothermal geothermal resources, the ground temperature gradient is 4.5-7.2 ℃/hm, and the ground heat flow value is 79mW/m². The main heat storage layers are heat storage of a Minghua suppression group, heat storage of a Liangpottery group and heat storage of a Dongying group. The chemical type of the heat water storage is mainly Cl-Na type water. The total mineralization degree of geothermal water is higher, and the collection pottery group is 8000 ~ 20000mg/L, and the group of Dongying is 18000 ~ 23000 mg/L. The chemical type of the Hanwu-ao pottery karst fissure heat water storage is also Cl-Na type, and the mineralization degree is 3000-10000 mg/L. The degree of mineralization of hot water in the ground increases with depth. The heat conduction coefficient of each reservoir rock is 3-3.6W/(m.K), and the heat capacity is 730-990J/(kg.K); the water has a thermal conductivity of 1 to 1.15W/(m.K) and a heat capacity of about 4200J/(kg.K).

The geothermal field has good hot water supplement, diameter and row conditions, and the heat reservoir is strong water-rich-extremely strong water-rich, belonging to a certain supplement geothermal field. According to geological survey regulations of geothermal resources, the annual exploitation of geothermal fields in eastern China sea areas can utilize 1.12 multiplied by 10 heat energy according to the grade of geothermal field survey research degree¹⁵J/a, equivalent to 1632 ten thousand tons of standard coal.

(II) geothermal well construction and cementing

The research of the seawater/temperature difference power generation test takes the heat storage of the Minghua ballast as a target layer, and the seepage direction of underground water of the target layer is from west to east. In order to optimize the heat exchange efficiency of the semiconductor temperature difference power generation system, the temperature difference power generation/heat exchange tube is designed to be perpendicular to the water seepage direction of an underground reservoir, namely the connecting line of two wells A and B is perpendicular to the underground water seepage direction. Thus, the two geothermal wells are arranged in the north-south direction. The two wells have the same structure and are both two open wells. The drilling uses a fixed offshore simple drilling platform, and the seabed well mouths of the geothermal wells are respectively provided with an underwater basal disc.

The depth of a geothermal south (A) well in a research area is 7m, the depth of a heat storage top plate of a Minghua ballast group is 727m (from the seabed), the thickness of the heat storage layer is 522m, and a thermoelectric power generation/heat exchange tube is designed to be positioned at 1/3 parts of the middle-upper part of the heat storage (namely the thermoelectric power generation/heat exchange tube penetrates through the heat storage for 174 m), namely a horizontal well is positioned at about 901m on the seabed. According to the drilling exploration result, the temperature of geothermal water at the depth of 900m of a geothermal well (A well and B well) is about 92.5 ℃, the permeability coefficient is about 9.2m/d, the mineralization degree of the hot water is about 4900mg/L, and the formation pressure coefficient is 0.95.

Firstly, opening: the well diameter is 444.5mm, and a phi 339.7mm surface casing is put into the well, and the depth is not less than 300 m. Opening two: and (3) setting a technical casing with the diameter of 311.2mm and the diameter of 244.5mm, connecting a drilling tool with a left-hand thread joint, feeding the drilling tool into the technical casing, overlapping the drilling tool with a surface casing by not less than 30m, and cementing. After entering a heat reservoir and being tested and evaluated, the window is opened for continuous increasing the deflection, a target point is designed every 50m, the deflecting section is 208m long, and the maximum deflecting rate is 6.73 degrees/30 m. The construction of the horizontal section of the two horizontal sections (727-901 m) adopts a mode of mainly composite drilling and secondarily sliding drilling, and adopts a resin rotational flow roller centralizer to ensure that the track of a well is as smooth as possible so as to reduce friction torque. In order to ensure the underground safety, short tripping is carried out for 1 time every 50m or 12h of drilling, each short tripping is carried out to form a straight well section, and the detritus bed of the slope-increasing section is fully damaged. And then, adding an undersized centralizer behind the power drill to reduce the increasing rate of the sliding drilling, reduce the sliding drilling times and improve the mechanical drilling speed. Meanwhile, the underground safety is ensured. And (4) reaming is required after 1 drilling is finished until the well hole is smooth, and drilling is continued without the phenomenon of resistance.

And (4) after the well A and the well B enter the thermal reservoir, performing vertical well section well cementation. The cement slurry is injected from the drilling tool, flows through the bottom of the well and returns upwards from the annular space, and the sealing of the interlayer is realized. Then, the method enters a first slope increasing section, a slope stabilizing section, a second slope increasing section and a horizontal section. And the track of the well hole is strictly controlled, and accurate target centering is ensured. The design of five sections of track, namely 'straight-increasing-stable-increasing-flat' is adopted, so that the complexity of the well track is simplified as much as possible. In the drilling process of the horizontal well, the thermal storage layer position is predicted and identified in advance according to stratum data, logging while drilling and measurement data, and measurement control of the well track is adjusted in real time. In the horizontal section drilling process of the horizontal well, the basic information before drilling comprises reservoir information (heat storage thickness, sand body communication and the like), adjacent well information (well logging curves, heat storage layer positions, water yield and the like), well body tracks (straight well section length, deflecting section length, horizontal section length and the like).

When the two wells are communicated, the SWG and the RMRS are matched to complete the track control of the well hole. The distance between two wells and the current position of the drill bit are accurately calculated through acquisition software. And in the communication process, a probe is put into another well, a strong magnetic short joint is connected to the drill bit, and the probe receives a strong magnetic signal to judge the position of a communication target point of the butt-joint well.

Two wells are designed with the horizontal distance of 1232m, wherein the well A is a directional horizontal well in the direction of 0 degree, the well B is a directional horizontal well in the direction of 180 degrees, and the two wells are in butt joint communication at the middle section. And installing a back-reaming device at the drill pipe head at the outlet end of the guide hole for reaming until the pore passage is enlarged to be capable of laying a corresponding pipeline or directly reaming and pulling a pipe for laying traction, and finishing the laying of the seawater pipe/thermoelectric generation pipe. Wherein, the length for installing the thermoelectric generation tube is 1232 meters +174 meters × 2-1580 meters.

After the well A and the well B are communicated, CO is firstly carried out₂And (4) performing well flushing operation to improve the permeability coefficient of the thermal reservoir of the horizontal well section. And then performing thermal reservoir well cementation, wherein the horizontal well section is cemented by adopting a high-strength sieve tube.

The casing windowing point should be selected as far as possible in a well section with good well cementation quality and uniformly distributed cement sheath, and a well section without cement channeling and cement outside the casing is avoided. Meanwhile, the sleeve at the windowing sidetracking part is required to be complete without deformation, perforation and fracture. The whole well adopts a flexible anti-blocking inverted drilling tool combination, and the weight drill pipe and the drill collar do not enter the open hole.

The bending stress of the casing in the bent borehole can affect the tensile strength and the internal pressure resistance of the casing, and the strength of the casing string is checked and calculated to determine the maximum borehole curvature allowed to be lowered by the casing string. And (4) referring to relevant manuals and material specifications, taking a casing material with the yield strength of 655MPa, the outer diameter of the casing of 0.2445m, the safety factor of 1.5 and the thread stress concentration coefficient of 2.3, and calculating the maximum borehole curvature allowed to pass through by the casing and the screen pipe to be 12.96 degrees/30 m. The maximum build-up rate calculated by checking is 6.73 degrees/30 m < the allowable maximum build-up rate is 12.96 degrees/30 m, and the method meets the related technical requirements.

(III) construction of high-level sea reservoir

The experiment researches that the sea area is normal day tide, and K ═ H_K1+H_O1)/H_M2At 24.0, tidal current motion is dominated by the reciprocating flow. The average temperature of the air is 11.7 ℃ for many years, the maximum temperature is 39.6 ℃, and the minimum temperature is-18.0 ℃. The average temperature of the moon is-3.5 to 25.9 ℃. The extreme high water level of the wave is 2.99m after 50 years (the recurrence period is the extreme high water level of 50 years).

Tidal level eigenvalues (calculated from the local theoretical lowest tidal level): average sea surface 0.73m, maximum tide level 1.93m, minimum tide level-0.76 m, average high tide level 1.02m, average low tide level 0.41m, average tidal range 0.61m, minimum tidal range 0.10m, maximum tidal range 1.66m, rising tide for 12 hours 6 minutes, and falling tide for 12 hours 42 minutes. The tidal level curve is more regular; every 10 days, the tide is twice or three times or even four times, the low-level curve is irregular, and the tide difference is very small. The bit curve has complex changes in the period of point division and regression transition. High tides sometimes appear double peaks, low tides sometimes go out of valleys or are dragged out of the flat, and the sea area has weaker overall astronomical tide properties.

The normal wave direction is the S direction, the frequency is 12.0%, the minor wave direction is the E direction, the frequency is 7.74%, the strong wave direction is the NE direction and the NNE direction, and the frequencies greater than 1.2m are 2.57% and 2.46% respectively. Measured H_1/10The wave height is 4.4m, corresponding to cycle 7.9s, and the wave direction is NE. The impact pressure of the waves on the vertical coast is about 0.02-0.04 MPa.

Determining parameters of the high-level sea reservoir according to the marine hydrological meteorological data and the design conditions: the normal water storage level is 1.95m, the maximum allowable water level is 2.5m, and the overflow dam height is 2.5 m. The experimental research area belongs to the landform of the coast of the muddy plain and is lack of water suitable for building high-level waterThe bedrock coast between the promontory bays of the reservoir. The experimental research reservoir replaces a high-level sea reservoir by utilizing a closed sea area surrounded by the existing breakwater, the second jetty and the coast, and the capacity of the Xingli reservoir is about 97 ten thousand meters³.2 one-way seawater gates of 2 x 2.6m are built on the east side of the two jetty dikes, only seawater is allowed to enter, and the gates are automatically closed when the seawater flows back. And a wave channel contracting from south to north is built on the two jetties, the wave channel is 21m long and 50m wide, and is contracted to 5m with a slope of 14 degrees. The wave energy is captured by the gradually contracted wave guiding wall and amplified in the gradually contracted wave guiding wall until the wave energy passes through the top of the wave guiding wall and enters a high-level sea reservoir. The constricting channel may be at H_1/10The wave height is 1.5m, and the higher the sea water is, the higher the sea water is, and the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher the sea water is, the higher.

The HDPE pipe is led out from a filtering water taking well in the reservoir, water is taken by gravity flow, and the water taking head adopts submerged side water inlet. The water intaking head adopts the multi-point mushroom hair style water inlet, arranges 3 circular water inlets on the single pipeline altogether, and every intake head diameter is 0.5m, and the water intaking head links to each other with the female pipe of below water intaking through the pipeline of diameter 1.0 m.

Checking the flow rate: under the condition that the normal water storage level is 1.95m, the average sea level is 0.73m, the water head difference of the inverted siphon system is 1.22m, and the flow velocity of seawater in the inverted siphon seawater pipe is calculated by waterpower and is 1.8m/s, so that the requirements of a semiconductor temperature difference power generation system can be met.

Flow checking: the purpose of building a high-level reservoir is to provide enough seawater potential energy for a cooling seawater pipe, so that the cooling seawater has certain flow velocity in a pipeline. The water flow in the inverted siphon is pressure flow. The minimum inner diameter of a semiconductor thermoelectric generation/seawater transportation/heat exchange/cable four-in-one pipe is designed to be 100mm, and when the flow coefficient mu is 0.82, the flow of cooling seawater in the pipe is 28.27m³/h。

Through checking, the water level and the storage capacity of the high-level sea reservoir can meet the flow speed and the flow rate of cold seawater required by normal power generation of the semiconductor thermoelectric power generation/seawater transportation/heat exchange/cable four-in-one pipe.

(IV) semiconductor thermoelectric generation/seawater transportation/heat exchange/cable four-position integrated pipe

The commonly used thermoelectric generator at present has two structural forms of a flat plate type and a barrel type. The flat plate is formed by tightly pressing a thermoelectric element on a flat plate on the rectangular side through which a heat source passes, and heat flows pass through a channel when the generator runs and are transferred to the generator through a wall surface. The flat plate type structure is convenient to install, the thermocouples can be made into a component type structure, the large-scale production is convenient, the cost is low, but the hot end heat flows of the thermocouples of the structure are possibly different, so that the temperatures of hot joints of the thermocouples are possibly different, and the heat utilization rate is low. The drum type is a structure in which thermoelectric elements are arranged in a line-type radial manner by taking a heat source as a center, and the thermocouples are arranged on the surface of the drum, so that heat can be effectively applied to the thermocouples, the conversion efficiency is high, and the high shock vibration resistance is realized. However, in recent years, due to the maturity of automated welding and packaging technologies, the manufacturing process of the cylindrical galvanic couple arrangement is more efficient, and the cost is sharply reduced.

In the structure of the generator, the thermoelectric monomers mostly adopt the form of an assembly, namely, a plurality of thermoelectric monomer pairs are compactly arranged into an array, thermoelectric elements are electrically insulated, electrodes are welded on the thermoelectric monomers according to a certain process and mode to form a whole, and the thermoelectric monomer pair is called as a thermoelectric generation assembly. After the thermoelectric power generation assembly is adopted, the generator is compact in structure and easy to assemble, the mass specific power and the thermoelectric conversion efficiency of the generator are improved, and the shock vibration resistance of the single body is enhanced.

In order to increase the reliability of the thermoelectric power generation/heat exchange tube and reduce the volume of the thermoelectric power generation device, the invention adopts the integrated thermoelectric thermocouple. Namely, the thermoelectric generation blocks are integrated together to form a tubular thermoelectric generation device, namely, a semiconductor thermoelectric generation/seawater transportation/heat exchange/cable four-position integrated pipe.

The four-in-one pipe is not only a temperature difference power generation device, but also a seawater flowing pipeline, and has the functions of a heat exchanger and a cable. Its versatility determines the multilayer structure of the tube. The four-bit integrated tube needs to have the following performance indexes: the sealing gasket has excellent sealing performance; the bearing can bear the adaptive pressure and axial tensile load; thirdly, the requirements of seawater corrosion resistance and scaling resistance can be met; fourthly, the temperature use environment requirement must be met; stable performance in service life, aging resistance, easy bending and convenient assembly and connection. The HDPE pipe only has the function of conveying cooling seawater, the wall thickness of the HDPE pipe is far smaller than that of a temperature difference power generation/seawater conveying/heat exchange/cable four-in-one pipe, the inner diameter of the HDPE pipe is the same, the outer diameter of the HDPE pipe is different, the outer diameter of the HDPE pipe is far smaller than that of the four-in-one pipe, and the HDPE pipe and the four-in-one pipe are connected through reducing.

The semiconductor thermoelectric generation/seawater transportation/heat exchange/cable four-position integrated pipe has the necessary mechanical strength, heat conduction (or heat insulation) and electric conduction (or insulation), and components of the pipe can bear larger pressure. For example, the pressure born by the water-cooled generator is 20-36 MPa under the water depth of 2000-3500 m. Therefore, the pressure resistance of the four-bit integrated tube and the thermocouple thereof designed by the invention is more than or equal to 53 MPa.

The thermoelectric couple of the invention adopts bismuth telluride-based commercial thermoelectric materials. 120 pairs of bismuth telluride-based P-type and N-type thermocouples are serially connected through copper sheets to form a thermoelectric power generation unit, and heat insulation pouring sealant is filled in gaps around the thermocouples for sealing. Each temperature difference power generation unit is 12cm multiplied by 12cm, 26332 power generation units are installed in the horizontal communication well section, and 8770 power generation units are installed in the seabed section. The theoretical indexes of a single thermoelectric generation unit are as follows: the maximum open-circuit voltage is 15V, the matched load resistance is 1.15 omega, the matched load output voltage is 8.3V, the maximum output current is 4.8A, the maximum output power is 39.8W, and the maximum heat flux density is about 66W/cm²。

As the semiconductor thermoelectric generation unit, the thermoelectric effect formed by the cold/hot ends of the thermoelectric couple is utilized, and the power generation performance is only related to the heat conducted by the thermoelectric couple and is not related to the heat exchange quantity outside the thermoelectric couple, so the heat conduction of the thermoelectric couple is increased as much as possible, and the ineffective heat conduction is avoided.

A heat exchange calculation model and numerical simulation display of an infinite-length-line horizontal circular tube in a seepage reservoir show that the higher the seepage speed of a heat reservoir is, the higher the heat exchange efficiency is. In addition, the influence of geothermal water seepage on the heat exchange performance of the thermoelectric generation tube is gradually reflected after a long time, the heat exchange tube is hardly influenced by the seepage within a certain time, and the influence of the seepage is gradually shown later. This is because the rate of hot water seepage from the reservoir is generally slow, taking time to remove heat from areas that have a significant effect on the heat exchange tubes, with less seepage taking longer.

Since the semiconductor thermoelectric generation array (pipe) is also a cable, the semiconductor thermoelectric generation array should have insulation properties in accordance with the geothermal power generation temperature and pressure conditions at the deep part of the earth crust. Meanwhile, the pipe has higher tensile strength, pressure resistance, compression resistance and shear strength.

The four-in-one rubber pipe mainly comprises an inner rubber layer, a thermoelectric generation device layer and an outer rubber layer from inside to outside, wherein a braided framework steel wire is embedded in the outer rubber layer.

An inner glue layer: the wall thickness is 3.6mm, the fluororubber 246 is used as a matrix, and silicon nitride is compounded and filled. The fluororubber 246/silicon nitride composite material is prepared by taking 2-micron, 7-micron and 30-micron silicon nitride particles as heat-conducting fillers and fluororubber 246 as an organic matrix through the processes of mixing, vacuum treatment, curing and the like. Characterization tests are carried out on the cured and formed fluororubber 246 composite material, and silicon nitride particles with the mass ratio of 2 microns, 7 microns and 30 microns are prepared according to the following steps: 3: 6 filling the fluororubber 246, when the filling amount is 92.5%, the thermal conductivity of the fluororubber 246 composite material is 2.82W/(m.K), the breakdown strength is 15.19kV/mm, and the plasticity is 0.26.

And the thermoelectric power generation device layer is a semiconductor thermoelectric power generation unit consisting of thermoelectric blocks (thermocouples), heat insulation potting adhesive, copper sheets and a welding layer. A plurality of semiconductor thermoelectric generation units are connected in parallel to form a thermoelectric generation device layer.

Copper sheet (flow deflector): the thickness is 0.5mm, the copper sheet is adopted because the copper sheet has high thermal conductivity and low Seebeck coefficient and Peltier coefficient, the joint of the copper sheet (flow deflector) and the end part of P, N is convenient for realizing the addition of a large amount of heat, the temperature difference of the joint can be small, and the P, N semiconductor cold and hot end can form the maximum temperature gradient by improving the heat flow density of the thermocouple. The yield strength of the copper sheet is 70MPa, the strength limit is 250MPa, and the elongation is 69%.

A thermocouple: using bismuth telluride (Bi)₂Te₃) A base material. Bi in nature₂Te₃They often contain isomorphism impurities, which are mainly produced in gold-containing quartz vein and tellurium-containing deposits with low sulfur content, and mostly high-medium temperature hot liquid deposits, and also in basic and super-basic rock copper nickel sulfide deposits. But useBi for generating electricity by temperature difference₂Te₃Is an artificial crystal by accurately controlling the relative contents of Bi, Te, Sb and other elements. Gaps among the bismuth telluride blocks on the thermoelectric generation device layer are filled and reinforced so as to improve the compressive strength of the thermoelectric generation device layer. The shear strength of the bismuth telluride based thermocouple was about 5 MPa.

The output voltage of the semiconductor temperature difference power generation module gradually rises along with the increase of the temperature difference, and the increasing speed of the output voltage gradually becomes smaller and finally tends to be constant along with the continuous increase of the temperature difference. The output power is gradually increased in a parabolic form along with the increase of the side length of the cross section of the thermoelectric element, and the thermoelectric generation conversion efficiency is almost unchanged along with the increase of the cross section of the thermoelectric element. The output power is gradually reduced along with the increase of the arm length, the thermoelectric generation conversion efficiency is slowly increased, the arm length can not be too large or too small for ensuring the balance of the output power and the conversion efficiency, and the arm length is selected to be 2.5mm according to an orthogonal test. The bismuth telluride-based P, N-type thermoelectric material is purchased as a commercial module, and has the size of 4 multiplied by 2.5mm, the thermoelectromotive force of 230 mu V/K, the thermal conductivity of 16 multiplied by 103W/m.K, the side length of the cross section of the P, N-type thermoelectric element is 4mm, and the arm length is 2.5 mm. The shear strength of the bismuth telluride-based thermoelectric material is about 5 MPa. Optimum figure of merit 3X 10^-3The melting point temperature is 585 ℃, and the density is 7.8587g/cm³。

Welding layers: the thickness of the welding layer tetrad is 0.1mm, the welding layer is made of Sn-Sb alloy, the yield strength of the Sn-Sb alloy is 26MPa, the strength limit is 41MPa, and the elongation is 38%.

The pouring sealant comprises the following components in formula: 107 silicone rubber, nanoscale calcium carbonate, precipitated calcium carbonate, 201 silicone oil, methyltributanone oxime silane, 550 coupling agent, 550 organotin, 100:11:11:16:7:1: 0.5. Firstly, stirring 107 silicon rubber, nano calcium carbonate, light calcium carbonate and 201 silicon oil into a mucilage, and grinding and dispersing the mucilage into uniform mucilage by using a three-roller grinding machine; and (3) carrying out vacuum heating (95 ℃) treatment for 20min, adding methyl tributyl ketoxime silane, 550 coupling agent and organic tin, stirring and reacting for 15min to obtain the heat-insulating sealant with good fluidity. And encapsulating the sealant between the gaps of the thermocouples and curing. The main parameters are as follows: the density is 1.05, the viscosity is 0.8 multiplied by 105 mPa.s, the using temperature is-50 to 250 ℃, and the surface resistivity is more than or equal to1.5×10¹³Omega, volume resistivity is more than or equal to 1.7 multiplied by 10¹⁵Omega, thermal conductivity 0.083W/m.K. The service life of the encapsulating material obtained by an accelerated aging test and an Arrhenius method extrapolation calculation is 25 years. The total thickness of the thermoelectric power generation device layer is equal to the thickness of the copper plate, the welding layer, the thermoelectric couple length, the welding layer and the copper plate is equal to 0.5+0.1+2.5+0.1+0.5, and is equal to 3.7 mm.

③ outer adhesive layer: the thickness is 4.7mm, and the heat exchange layer is the pipe body reinforcing protective layer and with the heat reservoir, and the principal ingredients is with interior glue film, but increased reinforced metal structure layer in its centre, its purpose is tensile strength, bearing capacity, the shock resistance of reinforcing pipe body, improves the vertical heat conductivity of pipe body. The reinforcing layer is braided with over-moulded steel wires at an angle of 54 deg. 44'. The high molecular adhesive layer formed by coating the metal wire with a heat-resistant high-strength adhesive (a commercial product ZS-1071 high-temperature-resistant adhesive) is fused with the composite pipe wall of the fluororubber 246 to form an integral structure, and the composite pipe wall and the reinforcing layer have no gap interface.

The four-position integrated pipe for thermoelectric generation/seawater transportation/heat exchange/cable has the main technical indexes that: the inner diameter is 100mm, the wall thickness of the header pipe is 12mm, and the outer diameter is 124 mm; the total thermal conductivity is 2.71W/(m.K); the breakdown strength is 15.10 kV/mm; the roughness coefficients of the inner wall and the outer wall of the pipe are less than or equal to 0.01; the working pressure is 10 to 53 MPa; elongation in static pressure test: the permanent elongation is less than or equal to 0.7 percent, and the temporary elongation is less than or equal to 2.5 percent; minimum bend radius 3 m; the maximum flow velocity of seawater in the pipe is 5 m/s; allowing the ambient temperature to be 10-180 ℃; conveying seawater at the temperature of 10-22 ℃; the design life is 25 years.

The smaller the flow resistance of the seawater in the semiconductor thermoelectric generation/seawater conveying/heat exchange/cable four-in-one pipe is, the better the seawater flow resistance is, so that the smooth rubber pipe with small hydraulic friction coefficient is selected as the inner layer. Due to the function of the heat exchanger, the rubber four-position integrated pipe has to have certain heat conductivity. The thermoelectric power generation/heat exchange tube is characterized in that cooling seawater flows longitudinally along the heat exchange tube, the temperature longitudinal change is large, and the length is far greater than the section size. The semiconductor thermoelectric generation characteristic determines that a large number of thermoelectric generation units form a semiconductor thermoelectric generation array (pipe) to carry out large-scale power generation. In the heat conduction process under ideal conditions, underground hot water conducts heat to the outer wall of the four-in-one seawater pipe, and the outer wall conducts heat to the thermoelectric generator through the outer pipe wallThe copper sheet and the copper sheet of the electric device layer conduct heat to the thermoelectric couple and the inner copper sheet, the inner copper sheet conducts heat to the inner wall of the thermoelectric generation device layer, and the inner copper sheet conducts heat to the outer adhesive layer and flowing seawater. Finally, the heat can be transferred to the seawater by the conduction and convection heat exchange of the four-in-one seawater pipe and the underground hot water seepage field. Therefore, the total heat transfer coefficient of the four-in-one seawater pipe system is limited by the heat conductivity coefficient of each layer of the pipe wall, the interface thermal resistance, the pipe wall fouling thermal resistance, the pipe external wall seepage conduction thermal resistance and the like. Fluid simulation according to Ansys Fluent showed: the hot end temperature is 92.5 ℃, the cold end temperature is 11.7 ℃, the total heat conductivity coefficient of the pipe wall of the thermoelectric power generation array is 2.68-2.74, and when the flow rate of the inverted siphon seawater is 1.8m/s, the heat absorbed by the seawater in the pipe is about 9 multiplied by 10⁶KJ/h, the power generation power of the horizontally communicated well section temperature difference power generation array pipe is maximum, and the minimum temperature difference of the tail end power generation module is more than or equal to 20 ℃.

Pipe-through laying traction of (V) four-position integrated pipe

The semiconductor temperature difference power generation system has two sections of pipelines with the temperature difference power generation function. The first section is a horizontal well section of a thermal reservoir between the A well and the B well, and is a main temperature difference power generation section; the second section is a tail end section exposed behind the B well head base plate and aims to utilize waste heat to carry out thermoelectric power generation. The rest section adopts HDPE pipe as cooling seawater pipe. The HDPE pipe has the same outer diameter as the thermoelectric generation/seawater transportation/heat exchange/cable four-in-one pipe. The elastic deformation of the HDPE pipe and the composite material power generation pipe adopted by the invention is far better than that of a drill string consisting of a drill rod and a drilling tool, so that the drilling tool is easier to pass through and lay and drag the four-in-one pipe than under the condition of pipe threading and drag.

After the geothermal horizontal communication well completes casing cementing, a casing dredger is required to be used for conducting the well dredging and the pulling back for no less than 3 times, whether the casing pipe is deformed or not is checked, whether sundries fall off from the casing pipe or not is checked, and the like. Ensuring the well bore to be unobstructed. After the test and acceptance are qualified, the process of pipe penetrating, laying and traction of the thermoelectric generation pipe can be carried out.

The maximum traction force of the thermoelectric generation tube is first calculated. If the pipelaying tractive effort is less than the generator pipe allowed tractive effort, pipelaying traction may be initiated. If the pipelaying tractive effort is greater than the generator pipe allowed tractive effort, the generator pipe protective casing needs to be added before pipelaying traction can be implemented. During the process of pipe penetrating, laying and traction, water must be filled in the sleeve to increase the lubrication degree of the pipe wall and the sleeve and also cool the friction heat generated by the pulling pipe.

The thermoelectric power generation tube has better toughness and tensile strength, so that the power generation tube is wound on a tube wire coil to complete tube threading traction for facilitating tube threading laying traction. And (3) putting a guide drill bit into one geothermal well (such as the well B), after the drill bit passes through the vertical section, the horizontal section and the vertical section and is exposed out of another geothermal well (such as the well A), dismounting the guide drill bit, replacing a pipeline pull-back clamp, firmly clamping the HDPE pipe for pulling back, and completing pipe penetrating and laying traction when the HDPE pipe is pulled back to the first geothermal well head (such as the well B). And then, laying a four-bit integrated pipe of the pipeline at the landing section and the submarine semiconductor thermoelectric generation pipe at the tail end section, and laying related cables and facilities.

The axial tension of the power generation pipe when the power generation pipe goes out of the wellhead is large, and if a common carrier roller pulley is used as a supporting point, the allowable lateral pressure of a sheath of the power generation pipe can be exceeded. The arc-shaped sliding plate at the well head is required to be made of a steel plate.

When the power generation tube enters the sleeve section and the tail disc of the power generation tube for 3 circles, the traction speed is not more than 2m/min, and the normal advance through the sleeve is not more than 6 m/min.

And (3) login section: the device is characterized in that an HDPE pipe is adopted from a high reservoir inverted siphon water intake to an A well seabed base plate section. The inverted siphon suction port is a submerged water taking well without a bottom valve filter screen. The entry section of the intertidal zone pipeline is in a wave breaking zone, the hydrodynamic force environment is complex, and the possibility of mechanical damage to the pipeline caused by offshore activities is reduced in order to reduce the adverse effect of the complex hydrodynamic force of the offshore area on the submarine stability of the pipeline; the HDPE pipe is buried no less than 1.5 meters below the sea floor. The method is characterized in that pre-trenching and backfilling modes are adopted for pipe burying protection, and floating and dragging methods are adopted for landing during pipeline laying. During pipe dragging and laying, the pipeline is laid along a pipe ditch which is excavated in advance. And (5) artificially backfilling the buried pipe in the intertidal zone submarine pipeline.

And the thermoelectric power generation pipe at the tail end section is accessed from the underwater basal disc of the B well. And laying according to the designed length. In order to exchange heat between the warm seawater in the pipeline and the normal-temperature seawater and form stable temperature difference secondary power generation, the section of temperature difference power generation pipe is overhead by a cement base, and the distance between the temperature difference power generation pipe and the seabed is more than or equal to 0.5 m. And buoys and safety warning areas are arranged around the power generation pipe, so that the safety of the temperature difference power generation pipe is prevented from being damaged by ship anchorage, fisherman operation and the like.

The HDPE pipe and the thermoelectric generation pipe are connected in an electric hot melting connection mode.

After the seawater in the pipeline returns to the seabed from the well B, the cold seawater is changed into warm seawater, the thermoelectric generation pipe laid from the well head B is also a warm seawater discharge pipe, the outside of the pipe is a cold end, and the inside of the pipe is a hot end. The thermoelectric generation of the section is opposite to the thermoelectric generation anode and cathode of the horizontal well, and the temperature difference is smaller than that of the horizontal well. The utilization rate of heat energy is improved by gradient utilization of waste heat of terrestrial heat. The temperature difference power generation/seawater pipe at the section needs to adopt the measures for resisting the adhesion of marine organisms.

Because the interface of the seawater pipe and the thermoelectric generation/heat exchange pipe needs to be sealed, the insulativity and the sealability of the thermoelectric generation/heat exchange pipe need to be checked after the laying is finished.

According to the measurement and calculation, in a seawater/geothermy/seawater semiconductor temperature difference power generation system of a geothermy field in eastern east China sea area, when the average working condition of the hot end temperature is 92.5 ℃ and the cold end seawater is 16.5 ℃, the cold/hot end temperature difference is 76 ℃, and the maximum power generation power of a pair of geothermy horizontal communication wells is as follows: 2296W of electricity can be generated every hour; when the temperature of the hot end is 98 ℃ and the temperature of the cold end seawater is 15 ℃, the temperature difference is 83 ℃, and the maximum thermoelectric power generation power of a pair of geothermal horizontal communication wells of the seawater/geothermal thermoelectric power generation system is as follows: 2623W of electricity was generated per hour.

The maximum power point output by the thermoelectric generation sheet system can change due to the influence of temperature/temperature difference, so that the maximum power point is tracked by the thermoelectric generation controller, the maximum output power of the thermoelectric generation sheet set is tracked, and stable voltage can be output. The semiconductor thermoelectric generation maximum power point tracking is a dynamic self-optimization process, the output voltage and current of the semiconductor thermoelectric generation are detected to obtain the output power under the current condition, then the output power is compared with the power value at the last moment, and if the power value at the current moment is larger than the power value at the last moment, the operation in the current direction is continued; otherwise, the operation is performed in the opposite direction. Then the detection and comparison are carried out, and the operation is carried out continuously, so that the temperature difference module can always work at the maximum power point. And delivered to the end user via the delivery network.

It can be understood that the above embodiments have at least the following advantages: tidal energy and wave energy are used for supplementing a water source for the high-level sea reservoir, the inverted siphon and the heat convection jointly drive the flow of seawater in the pipe, and continuous temperature difference is formed between the seawater and geothermal water outside the pipe. When the seawater returns to the seabed from the well B, the thermoelectric generation/heat exchange tube is converted into an internal-heat and external-cold thermoelectric generation device. The geothermal energy, tidal range energy and wave energy are comprehensively utilized for generating electricity.

Compared with other geothermal power generation methods, the method has the advantages of minimum total investment scale, safety, environmental protection and short investment recovery period of a power station under the condition of the same power generation scale.

The invention can effectively solve three technical problems of recharge, corrosion and scaling of the geothermal field. CaCO due to high mineral content in geothermal water₃And the temperature and the pressure can be greatly changed in the utilization process of geothermal water, the solubility of various mineral substances can be changed along with the change of the temperature and the pressure, and the mineral substances are separated out from the water to generate precipitation and scaling. The underground thermoelectric power generation tube is used for heat exchange, and geothermal water is not needed to be refilled into the well. The underground thermoelectric power generation tube is made of an anti-corrosion composite material, and conducts geothermal energy in situ, so that the problems of scaling and corrosivity of geothermal pipelines and equipment are solved. Due to in-situ heat exchange, the temperature and pressure conditions of the geothermal water are not changed, and the outside of the thermoelectric generation tube cannot be scaled.

After the sleeve and the sieve tube are fixed in the geothermal well, no complex pipeline system is provided except for the seawater tube for cooling; the device does not need to convey hot water remotely, does not have a water pump and does not need to add various medicaments.

In the operation period, the invention has no extra power or energy consumption except for regular maintenance, does not need manual care, can realize unmanned and automatic power generation, and has extremely low daily maintenance cost.

The abandonment of offshore oil and gas facilities is governed by national laws and international treaties, and faces high treatment cost and more challenging environmental protection problems. The invention can implement seawater/geothermal power generation by transforming the waste oil well in the sea area and the matched waste oil extraction platform, thereby greatly reducing the power generation cost and solving the difficult problem of marine environment protection.

The sea area geothermal gradient is larger than that of the land, the thickness of a sea area geothermal reservoir is large, the hot water temperature is high, and the large-scale implementation of seawater/geothermal semiconductor thermoelectric power generation is facilitated.

According to various methods such as experimental research, numerical simulation and the like, the semiconductor temperature difference power generation system and the semiconductor temperature difference power generation method can continuously and stably develop geothermal resources in a large scale.

The thermoelectric generation/heat exchange tube selectively exchanges heat with a thermal reservoir through a thermoelectric couple, the thermoelectric couple is filled with heat insulation glue, and the unused heat energy is still remained in the thermal reservoir.

The total heat conductivity coefficient of the thermoelectric power generation/heat exchange tube is determined according to the comprehensive characteristics of the temperature of the heat storage water, the seepage coefficient, the thermoelectric power generation device, the heat exchange quantity of the cold end and the like. The temperature difference between the cold end and the hot end of the thermoelectric couple can be ensured no matter at the front section or the tail section, and is larger than the minimum temperature difference (not less than 20 ℃) required by thermoelectric generation, namely, all the installed thermoelectric couples can generate electricity.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A geothermal/seawater semiconductor thermoelectric power generation system, comprising:

the U-shaped well is arranged in a preset sea area along the vertical direction, the well mouth of the U-shaped well is exposed out of the sea surface, and the lower horizontal section of the U-shaped well is positioned in the geothermal reservoir; the U-shaped well comprises a first well, a second well and a horizontal well, the lower ends of the first well and the second well are communicated through the horizontal well, and the horizontal well is positioned in the geothermal reservoir;

the high-level sea reservoir is arranged in an area close to the coast, the high-level sea reservoir contains seawater, and the water level height of the high-level sea reservoir is greater than the sea level height;

the first thermoelectric generation tube is arranged in the horizontal section of the U-shaped well in a penetrating mode and is communicated with the high-level sea reservoir through an HDPE tube in butt joint with the first thermoelectric generation tube; the second thermoelectric generation tube is laid on the seabed, and the first thermoelectric generation tube is communicated with the second thermoelectric generation tube through an HDPE (high-density polyethylene) tube;

the first thermoelectric generation unit is embedded in the pipe wall of the first thermoelectric generation pipe and is used for generating power according to the internal and external temperature difference of the first thermoelectric generation pipe;

and the second thermoelectric generation unit is embedded in the pipe wall of the second thermoelectric generation pipe, is positioned on the seabed outside the U-shaped well and is in contact with the seawater.

2. The geothermal/seawater semiconductor thermoelectric generation system of claim 1, further comprising:

the power management unit, with first thermoelectric generation unit and second thermoelectric generation unit electricity are connected, the power management unit be used for with the electricity that first thermoelectric generation unit and second thermoelectric generation unit were sent is carried to the user or is incorporated into the electric wire netting.

3. The geothermal/seawater semiconductor thermoelectric generation system of claim 2,

first thermoelectric generation pipe and second thermoelectric generation pipe include annular structure's interior heat conduction insulating layer and outer heat conduction insulating layer respectively, first thermoelectric generation unit and second thermoelectric generation unit set up respectively between interior heat conduction insulating layer, the outer heat conduction insulating layer.

4. The geothermal/seawater semiconductor thermoelectric generation system of claim 3,

first thermoelectric generation unit and second thermoelectric generation unit include a plurality of thermoelectric generation modules respectively, and are a plurality of the even range of thermoelectric generation module is in between interior heat conduction insulating layer and the outer heat conduction insulating layer, just thermoelectric generation module sets up two rows side by side.

5. The geothermal/seawater semiconductor thermoelectric generation system of claim 4,

the thermoelectric power generation module comprises a thermoelectric arm layer, an inner copper sheet layer and an outer copper sheet layer, wherein the thermoelectric arm layer is arranged between the inner copper sheet layer and the outer copper sheet layer.

6. The geothermal/seawater semiconductor thermoelectric generation system of claim 5,

one side of the high-level sea reservoir facing the sea is provided with a one-way gate and a wave guide wall, the one-way gate is used for enabling sea water to enter the reservoir when tide rises, and the wave guide wall is used for guiding sea waves into the reservoir.

7. The geothermal/seawater semiconductor temperature difference power generation system according to any one of claims 2 to 6, wherein the power management unit comprises a control module for controlling the flow rate of the seawater in the thermoelectric generation tube according to the power generation amount of the first temperature difference power generation unit and the temperature difference between the inside and the outside of the thermoelectric generation tube.

8. A geothermal/seawater semiconductor thermoelectric power generation method, which employs the geothermal/seawater semiconductor thermoelectric power generation system according to any one of claims 1 to 7, comprising the steps of:

step a: introducing seawater into a high-level seawater reservoir, wherein the water level of the high-level seawater reservoir and the sea level form a water level difference, so that normal-temperature seawater in the high-level seawater reservoir flows through the thermoelectric generation tube and is discharged into the ocean;

step b: when the normal-temperature seawater flows through a first temperature difference power generation unit in a geothermal reservoir, power generation is carried out after temperature difference is generated between the inner side and the outer side of the first temperature difference power generation unit;

step c: the normal temperature seawater flows through the geothermal reservoir and then is heated into high temperature seawater, and when the high temperature seawater flows through the second temperature difference power generation unit, the temperature difference is generated between the inside and the outside of the second temperature difference power generation unit and then power generation is carried out;

step d: and the power generated by the first temperature difference power generation unit and the second temperature difference power generation unit is transmitted to a power management unit, and the power is transmitted to a user or is merged into a power grid through the power management unit.

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