A system for geothermal energy development and utilization using natural media

Abstract

The present invention discloses a system for geothermal energy development and utilization using natural media, which includes a geothermal well drilled in a formation. A heat cycle unit and an electric energy unit are formed on the geothermal well, wherein: the heat cycle unit, the inlet and outlet ends of the heat cycle unit form a circulation line with the geothermal well, and at least one heat exchange line is further provided on the heat cycle unit, and this heat exchange line is connected to the end-use building. The heat cycle unit includes a turbine for driving, and the turbine is connected to the annulus of the geothermal well through a pipeline; the electric energy unit includes a generator installed on the output part of the turbine. The present invention uses supercritical carbon dioxide as a circulating working medium, extracts the formation heat in the downhole heat exchanger, the gasified carbon dioxide drives the steam turbine to generate electricity, and extracts the waste heat of the carbon dioxide after power generation through a condenser for heating utilization. This system can fully extract the heat in the formation, realizes combined heat and power supply, and plays the role of environmental protection and energy conservation.

Description

Technical Field

[0001] The present invention belongs to the technical field of geothermal power generation / heating and energy storage, and particularly relates to a system for developing and utilizing geothermal energy by using natural media. Background Art

[0002] As a renewable clean energy, the development and utilization of domestic geothermal energy are restricted by technical bottlenecks such as uneven resource distribution (less high-temperature and more medium-low temperature) and reinjection. As a result, the current direct utilization accounts for a relatively large proportion, and it only plays an important role in winter clean heating and alleviating air pollution in northern China. However, according to research, the development of medium-deep hydrothermal geothermal systems has caused a rapid decline in groundwater levels in many places in China, which is particularly significant in North China. Continuing like this will inevitably lead to geological disasters such as the formation of subsidence funnels and surface differential subsidence. At present, the development and utilization of medium-deep geothermal energy have begun to develop from the traditional direct exploitation of groundwater to the direction of "extracting heat without extracting water". One implementation form of "extracting heat without extracting water" is downhole circulating heat exchange. This method extracts heat from the formation without developing groundwater resources and makes up for some disadvantages and deficiencies of the hydrothermal geothermal system through downhole heat exchange.

[0003] At present, the heat exchange medium of the downhole heat exchange technology is mainly water. This heat exchange method has limited heat exchange capacity and requires a large amount of power consumption for the heat exchange cycle. Summary of the Invention

[0004] The purpose of the present invention is to provide a system for developing and utilizing geothermal energy by using natural media, using carbon dioxide as the circulating medium, to solve the problems in the above background art that the heat exchange medium of the downhole heat exchange technology is mainly water and requires a large amount of power consumption. At the same time, it causes corresponding pressure field changes, temperature field changes, and chemical field changes in the heat reservoir and the supercritical fluid in the heat reservoir, and induces seepage in the heat reservoir to achieve heat convection exchange in addition to heat conduction in the heat reservoir.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A system for developing and utilizing geothermal energy by using natural media, including a geothermal well drilled in the formation, on which a heat circulation unit and an electric energy unit are formed, wherein:

[0006] The heat circulation unit, the inlet and outlet ends of which form a circulation line with the geothermal well, and there is at least one heat exchange line on the heat circulation unit, which is connected to the end-use building. The heat circulation unit includes a turbine for converting the energy contained in the fluid medium into mechanical work, and the turbine is connected to the annulus of the geothermal well through a pipeline;

[0007] The electric energy unit includes a generator installed on the output part of the turbine.

[0008] As a preferred technical solution in the present invention, a downhole heat exchanger is provided inside the geothermal well.

[0009] As a preferred technical solution in the present invention, the heat cycle unit includes a compression pump installed at the gas outlet end of the turbine. A condenser is installed at the output port of the compression pump. The output end of the condenser is connected to a compressor. The output end of the compressor is installed with a coiled tubing, and the coiled tubing returns to the geothermal well. The output end of the condenser is connected to an electric compression heat pump through a pipeline. A circulation pump one is also installed between the intake end of the condenser and the electric compression heat pump. The output end of the electric compression heat pump is installed with a circulation pump two.

[0010] As a preferred technical solution in the present invention, the circulation line includes a primary circulation line formed by the geothermal well, the turbine, the compression pump, the condenser, and the compressor, and a secondary circulation line formed by the condenser, the electric compression heat pump, and the circulation pump one.

[0011] As a preferred technical solution in the present invention, the heat exchange line is composed of the condenser, the electric compression heat pump, and the circulation pump two.

[0012] As a preferred technical solution in the present invention, a cavity groove is formed on the surface of the electric compression heat pump. A protective net is arranged inside the cavity groove. Mounting posts are fixed at the inner wall of the cavity groove. The mounting posts penetrate through the protective net, and a limiting component for limiting the protective net is further arranged on the surface of the mounting posts.

[0013] As a preferred technical solution in the present invention, a placement hole is formed at the top of the mounting post. The limiting component is placed inside the placement hole. The limiting component includes a drum spring. An arc-shaped structure bulging towards the outside is formed on the surface of the drum spring. A side groove is formed on the surface of the mounting post. A limiting bolt is screwed into the interior of the mounting post, and the limiting bolt penetrates through the drum spring.

[0014] As a preferred technical solution in the present invention, clamping grooves are formed on the surface of the protective net. Protective ribs are installed between every two symmetric clamping grooves, and a plurality of protective ribs are distributed in a staggered manner.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The present invention uses supercritical carbon dioxide as a circulating working fluid to extract formation heat in a downhole heat exchanger. The gasified carbon dioxide drives a steam turbine to generate electricity, and the waste heat of the carbon dioxide after power generation is extracted through a condenser for heating use. The present invention uses supercritical carbon dioxide as a circulating working fluid to extract formation heat in a downhole heat exchanger. The gasified carbon dioxide drives a steam turbine to generate electricity, and the waste heat of the carbon dioxide after power generation is extracted through a condenser for heating use. At the same time, corresponding pressure field changes, temperature field changes, and chemical field changes occur in the heat reservoir and the supercritical fluid in the heat reservoir, causing seepage in the heat reservoir and realizing heat convection exchange in addition to heat conduction in the heat reservoir. This system can fully extract the heat in the formation, realizes combined heat and power supply, and plays a role in environmental protection and energy conservation.

[0017] This system can fully extract the heat in the formation, realizes combined heat and power supply, and plays a role in environmental protection and energy conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a system diagram of the present invention;

[0019] Figure 2 is a schematic structural diagram of the electric compression heat pump of the present invention;

[0020] Figure 3 is a cross-sectional view of the installation location of the protective net and the electric compression heat pump of the present invention;

[0021] Figure 4 is a cross-sectional installation view of the drum spring of the present invention;

[0022] Figure 5 is a composition diagram of the protective net of the present invention.

[0023] In the figure: 1, geothermal well; 2, downhole heat exchanger; 3, turbine; 4, generator; 5, compression pump; 6, condenser; 7, compressor; 8, electric compression heat pump; 82, protective net; 821, card slot; 822, protective rib; 83, installation column; 831, placement hole; 832, side groove; 84, drum spring; 85, limit bolt; 9, circulation pump one; 10, circulation pump two. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to Figures 1 to 5, the present invention provides a technical solution: a system for geothermal energy development and utilization using natural media, including a geothermal well 1 drilled in formation A. The geothermal well 1 is a closed completion well and does not exchange substances with formation A. A heat cycle unit and an electric energy unit are formed on the geothermal well 1. Due to different geological conditions, the involved temperature and energy are different, and at the same time, the ground equipment will be adjusted. When the formation temperature is greater than 150°C, power generation + heating may be beneficial; when it is lower than 150°C, it may only be used for heating. The core of the present invention is to improve the downhole heat exchange efficiency through this system, reduce power consumption, improve the system COP, and have a wider application scenario, and the natural media is pollution-free. The system consists of a composite continuous pipe cable located in the wellbore and a heat exchange and storage system located on the ground. The experimental system is only used to verify and test the heat exchange CO of the composite continuous pipe 2 phase change ability and parameters for extracting geothermal energy, where:

[0026] The heat cycle unit, the inlet and outlet ends of the heat cycle unit form a circulation line with the geothermal well 1, and there is at least one heat exchange line on the heat cycle unit, and the heat exchange line is connected to the end-use building C. The heat cycle unit includes a turbine 3 for converting the energy contained in the fluid medium into mechanical work, and the turbine 3 is connected to the annulus of the geothermal well 1 through a pipeline;

[0027] The electric energy unit includes a generator 4 installed on the output part of the turbine 3 and driven by rotation. Carbon dioxide gas after being released from the annulus of the geothermal well 1 and having a stable pressure change is sent to the turbine 3, and the turbine 3 drives the generator 4 to generate electricity. The electricity can be transmitted to the external power grid B through a line to supply power to the end-use building C. Carbon dioxide suboxide returns to the heat energy cycle as a natural medium. Especially in the air-conditioning field, it is necessary to protect the human living environment. However, the research and development of equipment and system integration required for the control of its Brayton Cycle process are still extremely challenging. The present invention proposes such a system idea, hoping to help all professionals work together to quickly enable carbon dioxide to be widely used as a natural medium in the heat energy cycle and make due contributions to achieving "carbon peak and carbon neutrality" and coping with global climate change.

[0028] In this embodiment, a downhole heat exchanger 2 is arranged inside the geothermal well 1. The downhole heat exchanger 2 is centered in the geothermal well 1. Supercritical carbon dioxide enters the geothermal well 1 through the downhole heat exchanger 2 and exchanges heat with formation A through the well wall of the geothermal well 1. Using coiled tubing manufacturing technology, a downhole exchanger that is resistant to high temperature, high pressure, and corrosion is developed through transformation, and it meets the use requirements of cluster wells and horizontal wells. This downhole heat exchanger 2 can not only meet the subcritical and transcritical cycles of carbon dioxide, but also be integrated with equipment such as optical fibers, thermal insulation materials, sensors, and throttles. Supercritical CO2 has both the general characteristics of supercritical fluids and its unique features: its density is close to that of liquids, more than two orders of magnitude greater than that of gases; it has high heat transfer efficiency and strong work capacity; its viscosity is close to that of gases, two orders of magnitude smaller than that of liquids; it has strong fluidity, is easy to diffuse, and the system circulation loss is small; its critical temperature and pressure are relatively low, and it is easy to reach the supercritical state, which is convenient for engineering applications; compared with commonly used inert gas supercritical fluids, it has a larger density and better compressibility, and the system equipment structure is compact and small in volume; its corrosiveness is less than that of water vapor; as a natural medium, it is non-toxic, non-flammable, stable, does not damage the ozone layer, and is cheap and easily available. The high-temperature CO 2 After the gas is cooled, it enters the compressor, and then is cooled by the ambient temperature and enters the expander for refrigeration; when compression is not required, a bypass is led out in front of the compressor and directly to the front of the expander, and is refrigerated by the expander; the refrigerated LCO 2 enters the storage tank; finally, after the LCO 2 is pressurized by the pump and pumped into the well.

[0029] In this embodiment, the heat cycle unit includes a compression pump 5 installed at the gas outlet end of the turbine 3. A condenser 6 is installed at the output port of the compression pump 5, and a compressor 7 is installed at the output end of the condenser 6. The compression pump 5 pumps carbon dioxide gas into the condenser 6 to cool it to slightly higher than 31.1 °C. The condensed carbon dioxide is discharged from the outlet of the condenser 6, reaches the supercritical state through the compressor 7, and enters the downhole heat exchanger 2 to continue the heat exchange cycle. A coiled tubing is installed at the output end of the compressor 7, and this coiled tubing returns to the geothermal well 1. The output end of the condenser 6 is connected to an electric compression heat pump 8 through a pipeline. A circulation pump 1 9 is also installed between the intake end of the condenser 6 and the electric compression heat pump 8. The condenser 6 is connected to the primary cycle of the electric compression heat pump 8. The fluid is driven by the circulation pump 1 9 to absorb heat from the condenser 6, and the temperature of the secondary cycle water is raised to the heat utilization temperature by the heat pump 8 and sent to the terminal energy-consuming building C by the circulation pump 2 10. A circulation pump 2 10 is installed at the output end of the electric compression heat pump 8.

[0030] In this embodiment, the circulation line includes a primary circulation line formed by a geothermal well 1, a turbine 3, a compression pump 5, a condenser 6, and a compressor 7, and a secondary circulation line formed by a condenser 6, an electric compression heat pump 8, and a first circulation pump 9. Among them, the heat exchange line is composed of a condenser 6, an electric compression heat pump 8, and a second circulation pump 10. The application of this principle and the circulation system is not limited to other application scenarios. For example, it can be used for energy storage in photovoltaic, solar thermal, and wind energy. Achieving peak shaving and valley filling and multi-energy complementarity through energy storage may be a very potential application scenario; another example is the development of dry hot rock geothermal energy, which is also an application scenario with great promise in the future; furthermore, carbon dioxide itself is a refrigerant, and the system can be appropriately adjusted to refrigerate simultaneously or separately on the basis of heating.

[0031] In this embodiment, a cavity groove is provided on the surface of the electric compression heat pump 8. A protective net 82 is arranged inside the cavity groove. Mounting posts 83 are fixed on the inner wall of the cavity groove. The mounting posts 83 penetrate through the protective net 82. A limiting component for limiting the position of the protective net 82 is also provided on the surface of the mounting posts 83. A placement hole 831 is provided at the top of the mounting posts 83. The limiting component is placed inside the placement hole 831. The limiting component includes a drum spring 84. An arc-shaped structure bulging towards the outside is formed on the surface of the drum spring 84, which is used to limit the position of the protective net 82 to avoid loosening in the later stage. During the separation of the protective net 82 in the later stage, only the protective net 82 needs to be pulled outwards to achieve rapid separation and the purpose of later maintenance. A side groove 832 larger than the protruding part of the drum spring 84 is provided on the surface of the mounting posts 83. A limiting bolt 85 is also screwed into the inside of the mounting posts 83. During installation, first place the drum spring 84 inside the placement hole 831, and then pass the limiting bolt 85 through the drum spring 84 and thread it with the inside of the placement hole 831 to complete the installation and limitation of the drum spring 84. The limiting bolt 85 penetrates through the drum spring 84. Card slots 821 are provided on the surface of the protective net 82. Protective ribs 822 are installed between every two symmetrical card slots 821. The multiple protective ribs 822 are distributed in a staggered manner to achieve the protective function.

[0032] Although the embodiments of the present invention have been shown and described (see the above detailed description), for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for geothermal energy development and utilization using natural media, characterized in that: It includes a geothermal well (1) drilled in the formation, and a heat cycle unit and an electric energy unit are formed on the geothermal well (1). Among them: the heat cycle unit, the inlet and outlet ends of the heat cycle unit form a circulation line with the geothermal well (1), and there is at least one heat exchange line on the heat cycle unit, and this heat exchange line is connected to the end user building. The heat cycle unit includes a turbine (3) for converting the energy contained in the fluid medium into mechanical work, and the turbine (3) is connected to the annulus of the geothermal well (1) through a pipeline; the electric energy unit includes a generator (4) installed on the output part of the turbine (3); the heat cycle unit includes a compression pump (5) installed on the gas outlet end of the turbine (3), a condenser (6) is installed on the output port of the compression pump (5), a compressor (7) is installed on the output end of the condenser (6), and a coiled tubing is installed on the output end of the compressor (7), and this coiled tubing returns to the geothermal well (1); the output end of the condenser (6) is connected with an electric compression heat pump (8) through a pipeline, and a circulation pump one (9) is also installed between the intake end of the condenser (6) and the electric compression heat pump (8), and a circulation pump two (10) is installed on the output end of the electric compression heat pump (8); the circulation line includes a primary circulation line formed by the geothermal well (1), the turbine (3), the compression pump (5), the condenser (6), and the compressor (7), and a secondary circulation line formed by the condenser (6), the electric compression heat pump (8), and the circulation pump one (9); the heat exchange line is composed of the condenser (6), the electric compression heat pump (8), and the circulation pump two (10); a cavity groove is opened on the surface of the electric compression heat pump (8), a protective net (82) is arranged inside the cavity groove, a mounting post (83) is fixed at the inner wall of the cavity groove, the mounting post (83) is connected through the protective net (82), and a limiting component for limiting the protective net (82) is also arranged on the surface of the mounting post (83); a placement hole (831) is opened at the top of the mounting post (83), the limiting component is placed inside the placement hole (831), and this limiting component includes a drum spring (84), the surface of the drum spring (84) forms an arc-shaped structure bulging towards the outside, a side groove (832) is opened on the surface of the mounting post (83), and a limiting bolt (85) is screwed into the mounting post (83), and the limiting bolt (85) is connected through the drum spring (84); clamping grooves (821) are opened on the surface of the protective net (82), and protective ribs (822) are installed between every two symmetrical clamping grooves (821), and a plurality of protective ribs (822) are distributed in a staggered manner.

2. A system for geothermal energy development and utilization using natural media according to claim 1, characterized in that: A downhole heat exchanger (2) is arranged inside the geothermal well (1).

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