Experts make high-strength rods to achieve high-altitude photovoltaic power generation

The article proposes a new type of high-strength (rigidity) compression and bending resistance mechanical structure, which fundamentally changes the stress form of the compression and bending resistance mechanical structure from compression to tension. The current mechanical theory shows that the stress-bearing material will become mechanically unstable after the slenderness ratio reaches a certain value when the stress-bearing structure is subjected to compressive stress. Therefore, after the slenderness ratio of such structure reaches a certain value, in order to ensure the stability of the structure under the same value of compressive stress, the mechanical material consumed increases exponentially with the increase of height or span.　　

The current solar panel power plant has not considered the issue of installing power generation equipment at a height of more than 5,000 meters to save ground land resources due to the cost of mechanical structure. The tower of the wind turbine based on ground support is generally designed to be within 100 meters due to the above reasons, which leads to extremely low exploitation and utilization rate of wind energy. The compression and bending resistant mechanical structure proposed in this paper will make the theoretical independent vertical height of seamless steel pipes made of wire rope steel of any diameter reach more than 5,000 meters. The use of supporting steel for solar panel power plants and wind power stations designed in this way can achieve an installation height of more than 5,000 meters when the amount of steel used is equivalent to that of existing designs. Installing solar panel power plants at this height can double the average power generation efficiency of the ground, occupy almost no land resources, and have almost no effect on the growth of ground plants when the equipment is not installed too densely. The total amount of wind energy that can be exploited in the world can be increased to more than 100 times what humans need, which will fundamentally solve the problems of human power energy shortage and environmental pollution caused by energy utilization.

The following is an illustration of the design and use of this article: (Figure 1) M is a seamless steel pipe of φ60×5mm, made of steel for making steel wire ropes. The maximum tensile strength of steel wire ropes with a tensile strength of 1870MPa is about 190.8 kg/square millimeter. The pipe is now filled with high-pressure fluid (such as light oil) and permanently sealed. At this time, the stress state of the outer wall of the steel pipe is tensile stress along the circumference of the steel pipe and tensile stress along the radial direction of the steel pipe. Mechanical analysis shows that the ability of the steel pipe to withstand the maximum pressure of the internal high-pressure fluid depends on the ability of the steel pipe to withstand the maximum tensile stress in the circumferential direction. At this time, the tensile stress along the radial direction of the steel pipe is about 45% of the circumferential tensile stress.

Take a 1 cm long steel pipe to analyze the stress state of the seamless steel pipe M (Figure 2): Under the action of the high-pressure fluid in the pipe, the outer wall of the steel pipe on both sides of the center O bears the tensile force as the maximum stress surface of the steel pipe. At this time, the sum of the cross-sectional areas of the pipe walls on both sides of the steel pipe is 1 square centimeter; according to the tensile capacity of the wire rope steel of about 190.8 kg/square millimeter, the sum of the maximum circumferential tensile capacity of the pipe walls on both sides of the steel pipe is 19080 kg (that is, the sum of the reaction force FG on the pipe walls on both sides of the steel pipe passing through the diameter of the center O of Figure 2 with a length of 1 cm is 19080 kg); at this time, the cross-sectional area of ​​the fluid in the steel pipe with a length of 1 cm passing through the center O of the pipe is 5 square centimeters; therefore, without considering the safety factor, the maximum pressure bearing capacity of this steel pipe is about 3816 kg/square centimeter (at this time, the sum of the force FY in the pipe passing through the diameter of the center O of Figure 2 with a length of 1 cm is 19080 kg). At this time, the cross-sectional area of ​​the high-pressure fluid in the steel pipe is a circle with a diameter of 5 cm, and its area is 19.625 square centimeters; at this time, due to the action of the high-pressure fluid in the steel pipe, 74,889 kg of reverse tensile stresses F and F1 will be generated at both ends of the steel pipe (Figure 1).　　

When the steel pipe M stands vertically on a stable foundation, the top force F of the high-pressure fluid in the pipe becomes a vertical upward pulling force acting on the center of the steel pipe. According to simple mechanical principles, when the total weight W of the steel pipe M is not greater than the upward pulling force F, the steel pipe M will not produce rigid instability phenomena such as bending (without considering the weight of the high-pressure fluid in the pipe).

The weight of a φ60×5mm steel pipe is approximately 6.8 kg/m. When the length of the steel pipe is 11013 meters, the weight W of the steel pipe is approximately equivalent to the vertical upward pulling force F. Therefore, without considering the weight of the high-pressure fluid in the pipe and the influence of external forces, the maximum vertical height H of the steel pipe M when the lower foundation is stable is above 11013 meters. At this time, the steel pipe M will not bend or have unstable rigidity.　　

This steel pipe is fixed vertically on the ground (Figure 1). When the steel pipe is bent by external force, the center point A1 of the top of the steel pipe deviates from the center point A of the bottom of the steel pipe accordingly, and the vertical height of the steel pipe decreases. At this time, when the sum of the top load and its own weight W of the steel pipe is less than the top tension F, the steel pipe itself will generate a component force vertically pointing to the center line of the steel pipe (when upright). Before the external force on the steel pipe reaches the material's breaking stress (the maximum pressure on the pressure-bearing surface is greater than 0), the greater the bending deformation, the greater its value. The result of this component force is that the greater the bending deformation of the steel pipe, the greater the anti-bending moment it generates, and the stronger the anti-deformation (anti-deformation) ability. This ability is the inherent characteristic of the steel pipe of this design. After the height of the steel pipe reaches a certain value, it has almost nothing to do with the stiffness of the steel pipe material itself.　　When this steel pipe is placed horizontally on a large-span support, due to the action of the tension at both ends, within the allowable load range, it also has the characteristic that the greater the bending deformation of the steel pipe, the stronger its own anti-deformation ability. In the horizontal placement state, when the weight of the steel pipe itself is not considered, the bearing capacity of the steel pipe has almost nothing to do with the distance (span) of the supports at both ends.　　

Further analysis shows that the stiffness of the rod in this design is related to the unit volume weight and the tensile strength per unit area of ​​the material used. That is, the smaller the specific gravity of the material and the higher the tensile strength, the greater the usable stiffness of the rod, and the greater the independent vertical height H will be under the premise of stable lower foundation. It has almost nothing to do with the slenderness ratio of the rod and the compressive strength of the material used for the rod. This is fundamentally different from the current commonly used design of increasing the cross-sectional area and external dimensions of the material and the compressive strength of the material itself to enhance the strength and stiffness of the compression and bending members.

When the outer wall thickness of the rod reaches more than 1/3 of the diameter, as the pressure bearing capacity of the steel pipe increases, the influence of the weight of the high-pressure fluid in the pipe on the stiffness and upright bearing capacity of the rod can be almost ignored.　　

This design allows solar panel power generation equipment to be installed at an altitude of more than 5,000 meters. The advantage is that the light intensity at high altitude is higher than that on the ground (on average more than 1.6 times), and the power generation efficiency of solar panel power generation equipment at high altitude is higher. Therefore, the average power generation efficiency of solar panel power generation equipment installed at high altitude can be 1 times higher than that on the ground. In the case where the equipment is not installed too densely, the low light position on the ground moves at the same time as the movement of the sun, so it will hardly have any effect on the growth of plants on the ground. At this time, the solar panel power generation equipment hardly occupies the ground land resources, and the installation of solar panel power generation equipment is almost no longer restricted by the region.　　

The total weight of the nacelle and impeller of the currently designed 1500KW wind turbine is 91 tons. When the tower height is 62 meters, the design weight of the tower is 91 tons, when the tower height is 90 meters, the design weight of the tower is 174 tons, and when the tower height is 100 meters, the design weight of the tower is 264 tons. The minimum limit steel consumption of the generator tower at the corresponding heights using this design is 0.5 tons (62 meters), 0.75 tons (90 meters), and 0.83 tons (100 meters). They are 1/180 (62 meters), 1/240 (90 meters), and 1/320 (100 meters) of the current design steel consumption, respectively. Taking into account a certain safety factor in actual use, the steel consumption of the generator tower using this design at a height of 100 meters is approximately 1/160 to 1/90 of the existing design. The wind turbine tower adopting this design has a relatively small windward area and its weight is reduced to less than 1/90 of the existing design. The lower foundation can be arranged at the corner of a regular triangle (or other regular polygon) with a larger side length. The influence of the moment generated by the windward surface of the wind turbine tower on the lower foundation when the wind turbine tower is running can be almost ignored during design. At this time, when designing the wind turbine tower foundation, it is almost only necessary to consider that the foundation's compressive strength reaches the total weight of the wind turbine plus a normal safety factor. Therefore, the amount of materials used in making the underground foundation of the wind turbine can be greatly reduced. Therefore, the cost of the wind turbine tower can be greatly reduced while the cost of installing the wind turbine can be greatly reduced.　　

Considering the safety of use, the rod designed according to 50% of the tensile strength of the steel wire rope can stand upright at a height of 5,500 meters without considering the weight of the high-pressure fluid in the pipe and the influence of external forces and the stability of the lower foundation. This rod can withstand a weight load of 30.6 tons at a height of 1,000 meters; with a total weight of 91 tons for a 1500KW wind turbine, about 3 steel pipes as shown in the example in the article are needed to install it at an altitude of 1,000 meters. At this time, the steel consumption of the generator tower is 20.4 tons, which is less than 1/4 of the steel consumption of the tower when the same wind turbine is installed at a height of 62 meters.　　

When a 1500KW wind turbine with a total weight of 91 tons is installed at a height of 5,000 meters, the design will use 5 5,000-meter seamless steel pipes of φ60×5mm made of steel for making steel wire ropes, consuming about 170 tons of steel. At this time, the steel consumption of the generator tower is still lower than the current steel consumption of the tower of the same type of wind turbine at a height of 90 meters (174 tons).　　

According to the wind resource information currently available, when the wind speed reaches 5 meters per second at an altitude of about 80 meters above the ground, the wind speed will rise to 7 meters per second at an altitude of 800 meters, and the wind energy is 2.7 times that of the 80-meter height. At the same time, the energy density of wind energy will be greater at the same location as the altitude increases. The technology in this article can almost make full use of all the valuable wind energy below 5,000 meters on the earth, and the total amount of wind energy that can be developed and utilized in the world can be expanded to more than 100 times the current scientific and technological level; therefore, the wind energy resources that can be developed and utilized on the earth will be far greater than the current total energy demand of mankind. If this technology is realized, it will be possible to completely solve the energy crisis of mankind.　Since the density of high-altitude wind energy is relatively large and more stable, the average unit time power generation of wind turbines installed at high altitude will be more and the annual power generation time will be longer. The investment of high-altitude generators installed according to this design is equivalent to that of similar units at present, so the cost of high-altitude wind energy power generation will be lower than the power generation cost of wind turbines with towers below 100 meters currently used.　　

Someone has designed a solar energy collection tower with a height of 1,000 meters. The main structure of the design is a chimney with a height of 1,000 meters and a diameter of 130 meters. The lower part is covered with a greenhouse canopy with a diameter of 7,000 meters. Under the premise of sufficient sunlight, when the air temperature at the top of the solar energy collection tower is 20°C, the air in the ground greenhouse canopy can reach 70°C (the air volume increase is 17%). At this time, the hot air will rise along the solar energy collection tower at a speed of about 55 kilometers per hour, and the 32 rotating turbines installed in the tower will produce a maximum of 200,000 kilowatts of electricity. Although in this working state, the efficiency of the solar energy tower in converting electricity is only less than one-tenth of that of solar panels (that is, the thermal efficiency is less than 1.4%). However, the advantage of the solar energy tower is that it is easier to maintain and has a lower cost. In fact, the difficulty of this design is that the cost of making a solar energy tower of 1,000 meters or higher is too high. According to a 2005 industry report, the construction of a solar energy tower with a 200,000-kilowatt electricity production capacity requires $1 billion, which means a cost of 20 cents per kilowatt-hour.

To make a solar tower using the technology of this article, you only need to make a flexible material with low specific gravity and high tensile strength into a circular chimney structure with inner and outer walls connected and interconnected and double-layer outer walls. When in use, the interlayer between the inner and outer walls of the solar tower is filled with air with the assistance of several independent steel pipes designed in this article with a height of more than 1,000 meters. The solar tower can reach a design height of 1,000 meters or higher. According to the weather forecast, when the external environment is bad, the air in the interlayer of the solar tower can be discharged to ensure the safety of the solar tower. It is also feasible to directly hang the materials of the solar tower on several independent steel pipes with a height of more than 1,000 meters to make a solar tower. If 13,607 seamless steel pipes of φ30×2mm ordinary 16Mn steel designed in this article are connected to each other and directly made into a solar tower with a height of 1,000 meters and a diameter of 130 meters, the construction of the solar tower only costs about 50 million US dollars.　　

If 13,607 seamless steel pipes of φ30×2mm and steel wire rope steel designed in this paper are connected to each other to directly make a solar tower with a height of 5,500 meters and a diameter of 130 meters, about 203,500 tons of steel pipes will be used. The maximum cost of making a solar tower is 3.05 billion yuan, or about 480 million US dollars, based on 15,000 yuan per ton of seamless steel pipes. The cost of a greenhouse canopy with a diameter of 7 kilometers is about 3.43 billion yuan, based on 80 yuan per square meter. Calculated based on the air temperature dropping by 6.5℃ for every 1 kilometer rise, the temperature at 5,500 meters is minus 15℃, and the temperature difference between the upper and lower parts of the solar tower is 85℃. It is 1.7 times the original design, and the height of the solar tower is 5.5 times the original design. Considering that the air density at 5,500 meters is about half of that on the ground, the actual pressure difference at the turbine outlet reaches 7 times the original design. At this time, the wind speed at the turbine inlet will reach 105 kilometers per hour, and the full-load power generation capacity of the system will reach 1.4 million kilowatts, which is 7 times the original design.　　The power generation equipment is calculated at RMB 1,500 per kilowatt. The total equipment investment is RMB 6,140 per kilowatt, which is equivalent to the equipment investment of a thermal power plant, and is far lower than the national standard of RMB 20,000 per kilowatt for photovoltaic power generation equipment that also uses solar power generation.　　

Since there is a 35℃ temperature difference between the ground and 5,500 meters above the ground, a pressure difference of 350 kg/m2 will be generated before and after the turbine in the solar tower when the greenhouse awning is not used for heating. The working capacity of each cubic meter of air is 350 kg·m. Calculated based on the air flow rate of 2 m/s in the tower, the system can generate 9,300,000 kg·m/s of power generation capacity, about 90,000 kilowatts. The investment per kilowatt of equipment is RMB 34,000. Calculated based on the annual power generation of 7,200 degrees per kilowatt of equipment and the service life of the system is 20 years, the power generation cost is about RMB 0.24 per degree. Considering the influence of high-altitude wind and the density of steel pipes used to make solar towers, the power generation cost can be reduced to one with a spacing of 300 mm, and the power generation cost is about RMB 0.03 per degree.　　

When the 5,500-meter solar tower system uses a greenhouse canopy for heating, the system's full-load power generation time is calculated as 3,000 hours per year. When the greenhouse canopy is not working, the power generation time is calculated as 4,200 hours per year. The annual power generation per kilowatt of equipment is 3,270 degrees, and the power generation cost is about RMB 0.094 per degree.　　

Another option that can be considered is to install the low-temperature heat source of the heat engine at an altitude of 5,500 meters and use the 35°C temperature difference between it and the ground to generate electricity.　　

Considering that the foundation of a 5,500-meter solar tower is difficult to manufacture with existing technology, even if the solar tower is stabilized by a cable-stayed method, it will be difficult to stabilize due to the strong wind at high altitudes. Therefore, the use of solar towers for power generation should start with a solar tower with a height of 1,000 meters.　　

If 54,428 seamless steel pipes of φ30×1mm and made of 16Mn steel designed in this article are connected to each other to directly make a solar tower with a height of 1000 meters and a diameter of 520 meters, about 74,000 tons of steel pipes will be used. Based on the price of 8,500 yuan per ton of seamless steel pipes made of 16Mn steel, the maximum cost of making a solar tower is 630 million yuan; without using greenhouse shed heating, the temperature difference of 6.5℃ between 1000 meters above the ground is directly used to generate electricity. A pressure difference of 14 kg/m2 will be generated before and after the turbine in the solar tower, and the work capacity of each cubic meter of air is 11.5 kg·m. A wind speed of about 4.2 m/s will be generated in front of the turbine in the solar tower, and the air flow rate behind the turbine in the solar tower is 2 m/s. After the air passes through the turbine, 1 kilowatt-hour of electricity is produced for every 32,000 cubic meters of air, and the amount of air passing through the turbine per second is 425,000 cubic meters. The turbine is arranged at the air inlet about 50 meters high under the solar tower. Considering the positive impact of the high-altitude wind force on the top of the solar tower, the average power generation capacity of the system is greater than 45,000 kilowatts. The equipment investment is 15,500 yuan/kilowatt. Based on the annual power generation of 7,920 degrees per kilowatt equipment (11 months of annual power generation), the power generation cost is about 0.1 yuan/degree. By reducing the density of the steel pipe used to make the solar tower to 300 mm per tube and sealing it with ordinary lightweight sealing and insulation materials, the cost of the solar tower can be reduced to less than 100 million yuan. The equipment investment is 3,720 yuan/kilowatt. The power generation cost is about 0.024 yuan/degree. This solution has a simple structure and is relatively feasible with the current technical level. This system will not have much impact on the ground temperature when providing 1.5 kilowatts of electricity supply capacity for each person in China. This system will also be a huge air-conditioning and environmental protection system. If the height of the solar tower reaches 2,000 meters, the system's power generation capacity will reach more than 180,000 kilowatts, and the system's power supply capacity will be increased by 4 times. If 13607 seamless steel pipes of φ30×2mm and 16Mn steel designed in this paper are connected to form a solar tower with a height of 1000 meters and a diameter of 130 meters, about 37,000 tons of steel pipes will be used. The investment of solar power generation equipment with greenhouse awning heating and a production capacity of 200,000 kilowatts is 19,725 yuan/kilowatt. The service life is calculated as 20 years, without considering the power generation capacity of the system at night, and the annual power generation time is calculated as 3,000 hours, and the power generation cost is about 0.33 yuan/kWh.　　

The technology in this article can reduce the cost of the greenhouse canopy frame to less than 30% of the existing design, so the cost of the greenhouse canopy can be reduced to less than RMB 40/square meter. The wall thickness of the solar tower steel pipe is reduced to 1mm, the steel pipe density is reduced to 300 mm per pipe, and the system investment is RMB 8150/kilowatt. The annual production of 3000 hours of power generation costs about RMB 0.014/degree, and the original design of the greenhouse canopy with a diameter of 7000 meters is based on the system's large heat storage capacity and greater production capacity at night. The reduction in high air temperature at night has a considerable stabilizing effect on the production capacity of the greenhouse canopy power generation system with heat storage capacity. Therefore, the power generation cost of the greenhouse canopy system may be reduced to less than RMB 0.1/degree. In China, using 1/3 of the desert area can achieve a power supply capacity of 3 kilowatts per person. It is a good project that not only manages and utilizes the desert but also solves the energy problem.

The power generation system without greenhouse canopy has the advantage of not occupying land. However, the design of greenhouse canopy itself has greater utilization value and greater power production capacity per unit area of ​​land. The design of greenhouse canopy is more suitable for construction in desert areas with large temperature difference between day and night to stabilize the power generation capacity of the system. In addition, the greenhouse canopy built in large areas in desert areas is also a good way to control desert.　　

If the above solar energy collection tower power generation project is analyzed accurately, it can be considered that it will replace almost all other energy utilization methods because the design of this article is more practical, lower cost, safer, more durable and environmentally friendly.　　

This technology can greatly reduce the construction cost of chimneys when used in thermal power plants. Three or more independent steel pipes with a height of more than 1,000 meters designed in this article and simple lightweight sealing materials with high tensile strength and temperature resistance of more than 170°C can be used to make chimneys with a height of more than 1,000 meters. The use of chimneys with a height of more than 1,000 meters in thermal power plants can reduce pollution to the surrounding environment on the one hand, and reduce or eliminate the dependence of thermal power plants on induced draft fans on the other hand, which will save a huge amount of operating power energy and even provide external power supply. The use of 1,000-meter-high chimneys in thermal power plants can generate electricity with a thermal energy power generation efficiency of about 1.4%.　　

The use of this technology in various cranes, large-span bridges, large-span house frames, trusses, various towers, high-altitude buildings, etc. will greatly reduce costs. When used in aircraft and load-carrying vehicles, it can reduce manufacturing costs and weight, and reduce their energy consumption; when used in vehicles, it can also improve the overall rigidity of the vehicle and greatly improve safety performance. When making the skeleton of a submarine, it will greatly reduce manufacturing costs, reduce weight, and expand the use space.　　

When this technology is used on wind turbine blades, the design length of the blades can be greatly increased. On the one hand, it can increase the height at which wind energy can be utilized without increasing the height of the wind turbine tower (it is possible to make the blade length reach more than 100 meters), and reduce its weight and production cost.　　

In short, this technology will be used in almost all pressure-bearing and bending-resistant structures and reduce costs, making many currently unimaginable large-scale mechanical structure designs possible. The realization of this technology will definitely have a significant positive impact on environmental protection, energy security, mechanical materials, traffic safety and other fields, or it will be a profound industrial revolution. It is a leap forward in the theory of material mechanics and structural mechanics.　　

In order to illustrate the problem, this design is based on the demonstration of filling the steel pipe with high-pressure fluid. Considering the safety and durability in actual use, if the pipe is filled with high-pressure solid, its safety and reliability will be more guaranteed. At present, I personally think that a more feasible design is to fill the pipe with small-diameter balls and lubricants that are resistant to high pressure; during operation, the pressure is transmitted to various parts of the inner wall of the steel pipe by the balls, and the lubricating oil is not subjected to force and only plays a lubricating role. In this way, the actual stress condition of the steel pipe is closer to the condition where the pipe is filled with high-pressure fluid, and at the same time, the stability of the use of this design can be basically guaranteed. If the technology of making the balls hollow and filled with high-pressure gas is feasible and adopted in this technology, the effect will be better. To find the best solution for making a high-rigidity structure with reliable safety performance based on the theoretical basis of this design, it must be obtained after a lot of practice in the future, so it will not be discussed too much here.　　

When the pressure design inside the pipe is not too high, a more feasible method is to fill the semi-enclosed steel pipe with expansion cement. When the cement solidifies, the steel pipe is fully enclosed to make a rod with reliable safety performance that meets the mechanical requirements of this design.　　Even if the existing cylindrical tower of a wind turbine is only filled with sand or water and then sealed, when the tower is bent under force, the internal volume of the steel pipe is reduced due to deformation, which will inevitably generate pressure on the external pipe wall, causing tension at the upper and lower ends of the cylindrical tower of the wind turbine. Since the sand or water in the pipe is basically incompressible, a very small volume reduction will rapidly increase the pressure in the pipe and rapidly increase the anti-deformation ability of the steel pipe. In addition, the greater the bending deformation of the steel pipe in a larger range, the stronger its anti-deformation ability is, thereby greatly increasing the elasticity and stiffness of the tower within the elastic range. Therefore, it is entirely possible to reduce the steel consumption of the wind turbine tower to less than 1/10 of the current existing design with this simple change; or conservatively speaking, using 20% ​​of the steel of the current 100-meter-high wind turbine tower design can install the generator set at an altitude of more than 500 meters.　　

Adding a sealed inner liner inside the tube and filling the inner liner with high-pressure fluid is also an implementation method of this design. Since this structure is basically not damaged by external forces, the method of replenishing the pressure in the tube at any time according to the current technical level with the help of good monitoring and control means is also relatively safe to use.　　

Assuming that a plastic mineral water bottle with little rigidity increases its rigidity to the point where it can hardly be bent or deformed without other tools or manpower when the bottle is filled with water and sealed, this can illustrate many mechanical problems of this design.