Ultra-deep well type hydroelectric generation method utilizing cold and hot water density difference of geothermal energy

Abstract

The invention relates to an ultra-deep well type hydroelectric generation method utilizing geothermal energy and cold and hot water density difference, and solves the problem that geothermal energy cannot be generated and utilized by a water turbine since underground hot water is pumped by a water pump for use in traditional geothermal energy utilization. Comprising the following steps of S1, exploration well drilling, S2, well bottom crack manufacturing, S3, center pipe deployment, S4, cold water is injected between the center pipe and a sleeve, after the cold water is heated by a dry hot rock stratum at the bottom of the exploration well, hot water rises from the center pipe, and the water head difference between the interior and the exterior of the center pipe is formed through the specific gravity difference of the hot water and the cold water. Hot water conveyed to the ground by the central pipe impacts the water turbine for power generation. A heat collection point is a dry hot rock stratum, the influence on underground water is reduced, the inertial thinking that height potential energy of water flow needs to be utilized in traditional water turbine power generation is broken through, and a brand-new water flow from bottom to top hydroelectric generation mode is provided.

Description

Technical Field

[0001] The invention belongs to the field of energy, and relates to a method for utilizing deep geothermal energy, and in particular to an ultra-deep well hydroelectric power generation method utilizing the density difference between cold and hot water of geothermal thermal energy. Background Art

[0002] Geothermal energy is a kind of energy from the earth's interior and is a clean renewable energy source. Humans have been using geothermal energy for a long time, such as using hot springs for bathing, medical treatment, using underground hot water for heating, building greenhouses for crops, aquaculture, and drying grains. The most traditional way to use geothermal energy is to explore shallow geothermal energy and exploit the groundwater heated by geothermal energy. Low-temperature thermal energy is widely distributed, and the traditional exploration and exploitation target of geothermal energy is usually high-temperature groundwater, while there is little utilization of geothermal energy in deep underground hot dry rock formations, and there is a lack of effective utilization methods.

[0003] At present, the mainstream power generation methods generally use steam turbines or water turbines. Steam turbines use high temperature to heat water into high-temperature and high-pressure steam, and then use steam to spray the impeller to rotate the steam turbine to generate electricity. Traditional thermal power plants and nuclear power plants all use steam turbines to generate electricity. Water turbines generally build dams at locations with large river drop, and use the potential energy of the water flow to impact the turbine blades to generate electricity.

[0004] The traditional use of geothermal energy requires water pumps to pump underground hot water to the surface for use. The pumping process itself consumes energy. Therefore, the traditional use of geothermal energy for power generation generally uses geothermal energy to heat water and use steam turbines to generate electricity. It is difficult to use water turbines to use geothermal energy for power generation. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that traditional geothermal energy utilization mostly uses water pumps to extract underground hot water for use, and it is impossible to use turbines to generate electricity from geothermal energy. An ultra-deep well hydroelectric power generation method that utilizes the density difference between cold and hot water of geothermal thermal energy is proposed. A single well is used to explore deep underground hot dry rock formations, and the head difference generated by the specific gravity difference of cold and hot water is used as water flow power, thereby driving the turbine to generate electricity.

[0006] The technical solution adopted by the present invention to solve the technical problem is: an ultra-deep well hydroelectric power generation method using the density difference of hot and cold water of geothermal thermal energy, comprising the following steps: S1, geothermal well drilling, according to the geological exploration report, use a drilling rig to drill vertically from the surface to the predetermined depth of the hot dry rock layer to form a vertical well channel. During the drilling process, a stainless steel casing with matching diameter is installed in the interval from the surface to 75% of the depth of the well for wall protection; S2, creating cracks at the bottom of the well. After the geothermal well reaches the predetermined depth, the hot dry rock formation in the bottom area of ​​the well is sealed and split. Controlled blasting or hydraulic fracturing technology is used to artificially create cracks in the hot dry rock formation to expand the heat exchange area and improve the efficiency of heat energy collection. S3, deploying a central pipe. A stainless steel central pipe is deployed in the center of the geothermal well. The bottom of the stainless steel central pipe is higher than the bottom of the geothermal well. The height difference is 3% to 10% of the depth of the geothermal well. The upper end of the central pipe is connected to the turbine. S4, cold water is poured into the space between the central pipe and the casing. After the cold water is heated by the hot dry rock at the bottom of the geothermal well, hot water rises from the central pipe. The difference in specific gravity between hot and cold water forms a water head difference inside and outside the central pipe. The hot water transported to the surface by the central pipe impacts the turbine to generate electricity.

[0007] In this scheme, the cold water on the surface is injected by gravity flow, without the need for power. After the cold water is heated at the bottom of the well, the density of the hot water decreases and it rises from the central tube. The difference in specific gravity between the cold water and the hot water is used to generate a sufficient head difference, so that the water flow in the central tube has a sufficient flow rate to drive the turbine blades to generate electricity. Compared with traditional geothermal power generation, this application uses hot dry rock formations as the hot spot to reduce the impact on groundwater, uses underground thermal energy as energy, and uses the density difference between cold and hot water to generate a head difference as the power to drive the turbine to generate electricity. The use of clean and renewable geothermal energy breaks the inertial thinking that traditional turbine power generation requires the use of the high potential energy of the water flow, and provides a new way of hydroelectric power generation from the bottom up. In addition, this application not only utilizes the thermal energy of deep geothermal energy, but also utilizes the kinetic energy of geothermal energy, making better and more comprehensive use of geothermal energy.

[0008] Preferably, in S1, the depth of the geothermal well is 3000-10000 meters.

[0009] Preferably, in S2, the bottom hole area is the area below the bottom end of the stainless steel casing.

[0010] Preferably, in S3, the outer wall of the stainless steel central tube has an insulation layer. The insulation layer is arranged on the outer wall of the stainless steel central tube, and the inner wall of the stainless steel central tube is a stainless steel tube wall with a low resistance coefficient, which reduces flow resistance and head loss.

[0011] Preferably, the thermal insulation layer is an aerogel thermal insulation layer.

[0012] Preferably, in S3, the water outlet of the turbine is connected to a thermal device.

[0013] Preferably, in S4, the hot water transported to the surface by the central pipe first enters the turbine for kinetic energy utilization, and then enters the heat-using device for thermal energy utilization.

[0014] The hot spot of the mining in the present invention is a dry hot rock layer, which reduces the impact on groundwater, uses underground thermal energy as energy, and uses the density difference between cold and hot water to generate a head difference as the power to drive the turbine to generate electricity. The utilization of clean and renewable geothermal energy breaks the inertial thinking that traditional turbine power generation requires the use of the high potential energy of water flow, and provides a new way of hydroelectric power generation from bottom to top. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] Figure 1 It is a structural schematic diagram of the present invention.

[0017] In the figure: 1. geothermal well, 2. stainless steel casing, 3. central pipe, 4. aerogel insulation layer, 5. cold water injection channel, 6. hot water rising channel, 7. dry hot rock formation, 8. cracks, 9. turbine. DETAILED DESCRIPTION

[0018] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0019] Embodiment: A method for generating ultra-deep well hydroelectric power by utilizing the density difference between hot and cold water of geothermal energy, such as Figure 1 The method comprises the following steps: S1, drilling of geothermal well 1, using a drilling rig to drill vertically downward from the surface to a predetermined depth of hot dry rock layer 7 to form a vertical well channel, the depth of the geothermal well is 3000-10000 meters; during the drilling process, a stainless steel casing 2 with matching diameter is installed in the interval from the surface to 75% of the depth of the well for wall protection; S2, creating cracks at the bottom of the well. After the geothermal well reaches the predetermined depth, the dry hot rock layer in the bottom area of ​​the well is sealed and split. The bottom area of ​​the well is the area below the bottom end of the stainless steel casing. Using controlled blasting or hydraulic fracturing technology, artificial cracks 8 are created in the dry hot rock layer to expand the heat exchange area and improve the efficiency of heat energy collection. S3, deploying a central pipe 3, deploying a stainless steel central pipe 3 in the center of the geothermal well, the outer wall of the stainless steel central pipe 3 has an aerogel insulation layer 4; the bottom end of the stainless steel central pipe 3 is higher than the bottom end of the geothermal well 1, and the height difference is 3% to 10% of the depth of the geothermal well, the upper end of the central pipe is connected to a turbine 9, and the water outlet of the turbine is connected to a heat device; S4, cold water is injected from the cold water injection channel 5 between the central pipe and the casing. After the cold water is heated by the hot dry rock layer 7 at the bottom of the geothermal well, hot water rises from the hot water rising channel 6 in the central pipe. The head difference inside and outside the central pipe is formed by the difference in specific gravity between hot water and cold water. The hot water transported to the surface by the central pipe first enters the turbine for kinetic energy utilization, and then enters the heat-using device for thermal energy utilization.

[0020] Taking the stainless steel casing 2 with a diameter of 1 meter and a central pipe with a diameter of 0.4 meters as an example, the surface cold water injection temperature is 20°C and the central pipe output hot water is 100°C.

[0021] Method for generating electricity by utilizing the density difference between cold and hot water in deep geothermal wells: The density of water changes with temperature. The density of water at 100℃ and 20℃ is 0.958 g / cm³ and 0.998 g / cm³ respectively. The difference in water head inside and outside the stainless steel center tube is mainly determined by pressure. Under the same atmospheric pressure, the pressure of the two waters will be different due to the difference in density. However, in practical applications, we are more concerned about the difference in water head between the two waters under different conditions, rather than the absolute water head value. If you need to calculate the specific water head difference, you also need to consider other factors, such as pipe friction, flow rate, etc.

[0022] In this example, the water columns inside and outside the stainless steel center tube produce the same pressure at the same depth at point A at the bottom of the stainless steel center tube, so: ΔP 100 =0.958×9.8×h 100 ΔP 20 =0.998×9.8×h 20 Where ΔP 100 is the pressure of 100℃ water in the central tube at point A, h 100 is the height of 100℃ water in the central tube, ΔP 20 is the pressure of 20℃ water in the center tube at point A, h 20 is the height of 20℃ water outside the central tube. Since the pressure at point A is equal, we have: 0.958×9.8×h 100 =0.998×9.8×h 20 Solving the above equation yields: h 100 = (0.998 / 0.958) × h 20 ≈1.043×h 20 This means that at the same pressure, the liquid level difference of 100℃ water is about 1.043 times that of 20℃ water. If the liquid level of 20℃ water is known, the liquid level of 100℃ water can be calculated by the above ratio, and the head difference of hot and cold water inside and outside the central tube can be calculated accordingly.

[0023] From the above, we can know that for every 1,000 meters of deep geothermal well depth, there will be a 43-meter head difference. Assuming that the depth of the stainless steel central pipe is 4,000 meters, the flow resistance of water in the pipe is related to the pipe material, pipe diameter, pipe linearity, and water flow velocity. The pipe material and pipe diameter are known, and the pipe is a straight pipe in this example. The greater the water flow velocity, the greater the flow resistance. When the flow resistance and the head difference reach a balance, the water flow velocity in the pipe reaches the maximum. The head difference of hot and cold water is close to 172 meters. The maximum flow rate of the 400mm stainless steel central pipe can reach 1.72 cubic meters per second. The generator can generate 34,400 degrees of electricity in a day and night.

Claims

1. An ultra-deep well hydroelectric power generation method using the density difference between hot and cold water of geothermal thermal energy, characterized in that: The following steps are involved: S1, geothermal well drilling, according to the geological exploration report, use a drilling rig to drill vertically from the surface to the predetermined depth of the hot dry rock layer to form a vertical well channel. During the drilling process, a stainless steel casing with matching diameter is installed in the interval from the surface to 75% of the depth of the well for wall protection; S2, creating cracks at the bottom of the well. After the geothermal well reaches the predetermined depth, the hot dry rock formation in the bottom area of ​​the well is sealed and split. Controlled blasting or hydraulic fracturing technology is used to artificially create cracks in the hot dry rock formation to expand the heat exchange area and improve the efficiency of heat energy collection. S3, deploying a central pipe. A stainless steel central pipe is deployed in the center of the geothermal well. The bottom of the stainless steel central pipe is higher than the bottom of the geothermal well. The height difference is 3% to 10% of the depth of the geothermal well. The upper end of the central pipe is connected to the turbine. S4, cold water is poured into the space between the central pipe and the casing. After the cold water is heated by the hot dry rock at the bottom of the geothermal well, hot water rises from the central pipe. The difference in specific gravity between hot and cold water forms a water head difference inside and outside the central pipe. The hot water transported to the surface by the central pipe impacts the turbine to generate electricity.

2. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 1, characterized in that: In S1, the depth of the geothermal well is 3000-10000 meters.

3. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 1, characterized in that: In S2, the bottom hole area is the area below the bottom end of the stainless steel casing.

4. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 1, characterized in that: In S3, the outer wall of the stainless steel central tube has an insulation layer.

5. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 4, characterized in that: The thermal insulation layer is an aerogel thermal insulation layer.

6. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 1, characterized in that: In S3, the water outlet of the turbine is connected to a heat device.

7. The method for generating ultra-deep well hydroelectric power by utilizing the density difference between cold and hot water of geothermal thermal energy according to claim 6, characterized in that: In S4, the hot water transported to the surface by the central pipe first enters the turbine for kinetic energy utilization, and then enters the heat-using device for thermal energy utilization.

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