F=1/2?ρ?S·VC
Where ρ——air density, typically 1.25 (kg/m?)
S— —wind wheel facing the Wind zone
V——Incoming wind speed
C——Aerodynamic coefficient
Take the example of a hemisphere when the wind blows towards the concave side of. hemisphere, the c value is 1.33. When the wind blows toward the convex side of the hemisphere, the c value is 0.34. For the cylinder, when the wind blows towards the concave and convex surfaces, the coefficients c are 2.3 and 1.2 respectively. Due to the asymmetry of the blades that make up the wind turbine and the difference in air resistance, the effect of the wind on the wind turbine forms a pair of driving forces around the axis of rotation, and the the whole wind turbine turns.
Why are wind turbines vertical rather than horizontal?
The differences between horizontal axis and vertical axis wind turbines lie in the following aspects:
1. Design method
The blade design of horizontal axis wind turbines, Momentum-foil element theory is commonly used, and the main methods include Glauert method, Wilson method, etc. However, because the blade element theory ignores the flow interference between each blade element, and at the same time ignores the airfoil resistance when designing blades using blade element theory, this simplification inevitably leads to imprecision in the results. This simplification has little impact. on the design of the blade shape, but has a greater impact on the wind energy utilization rate of the wind wheel. At the same time, the interference between the blades of the wind wheel is also very strong, and the entire flow is very complex. It is impossible to obtain accurate results based on blade element theory alone.
The design of the bladeshe vertical axis wind turbines were formerly based on the horizontal axis design method and relied on blade element theory. Since the flow of vertical axis wind turbine is more complex than that of horizontal axis, it is a typical large separation unsteady flow and is not suitable for analysis and design using blade element theory. This is also an important reason for the vertical axis. The wind turbine has not been developed for a long time.
2. Wind power utilization rate
The wind power utilization rate of large horizontal axis wind turbines is mainly calculated by blade designers and is generally above 40%. As mentioned earlier, due to flaws in the design method itself, the accuracy of wind energy usage calculated in this way is highly questionable. Of course, the wind turbines of wind power plants tracewill provide wind power curves based on measured wind speed and power output. However, the wind speed at that time is the wind speed measured by the anemometer on the back of the wind wheel. as the speed and power of the incoming wind. The curve is too high and needs to be corrected. After applying the correction method, the wind energy utilization rate of the horizontal axis will be reduced by 30-50%. Regarding the wind energy utilization rate of small horizontal axis wind turbines, the China Aerodynamic Research and Development Center has conducted relevant wind tunnel experiments, and the measured utilization rate is between 23% and 29%. %.
3. Structural characteristics
During rotation, the blades of the horizontal axis wind turbine are affected by the combined effects of the force of inertia and gravity. The direction of the inertial force changes at. at any time. The managementof gravity remains unchanged, the blades are therefore an alternating load, very detrimental to the fatigue life of the blade. In addition, horizontal axis generators are placed at an altitude of tens of meters, which brings a lot of inconvenience to the installation, maintenance and inspection of generators.
The blades of the vertical axis wind turbine are much better stressed during rotation than those of the horizontal axis. Since the direction of the force of inertia and gravity always remains unchanged, the blades are subjected to a constant load. The fatigue life is longer than that of horizontal axis wind rotors. At the same time, the vertical axis generator can be placed under the wind wheel or on the ground for easy installation and maintenance.
4. Start-up wind speed
There is a consensus that the start-up performance of horizontal axis wind turbines is good. However, depending onion of wind speed of small horizontal axis driven wind turbines. the China Aerodynamic Research and Development Center According to tunnel experiments, the starting wind speed is generally between 4-5m/s, and the maximum reaches 5.9m/s. Such startup performance is obviously unsatisfactory. There is also an industry consensus that the starting performance of vertical axis wind turbines is poor, especially for Darrieus Ф-type wind turbines, which have no self-starting capability, which is also a reason which limits the application of the vertical wind turbine. axis wind turbines. However, for the Darrieus type H wind wheel, the conclusion is the opposite. According to the author's research, as long as the aerodynamic profile and installation angle are correctly selected, fairly good starting performance can be achieved. Judging by the experiences in younnel, the starting wind speed of this Darrieus type H-shaped wind rotor only needs 2m/s. , which is better than the horizontal axis wind turbine mentioned above.
Is it better to use vertical axis or horizontal axis for wind turbines for wind-solar hybrid street lights?
The differences between horizontal axis and vertical axis wind turbines lie in the following aspects:
1. Design method
The design of horizontal axis wind turbine blades, The impulse-sheet element theory is commonly used, and the main methods include Glauert method, Wilson method, etc. However, because the blade element theory ignores the flow interference between each blade element, and at the same time ignores the airfoil resistance when designing blades using blade element theory, this simplification inevitably leads to imprecisionn in the results. This simplification has little impact. on the design of the blade shape, but has a greater impact on the wind energy utilization rate of the wind wheel. At the same time, the interference between the blades of the wind wheel is also very strong, and the entire flow is very complex. It is impossible to obtain accurate results based on blade element theory alone.
The design of vertical-axis wind turbine blades was formerly based on the horizontal-axis design method and relied on blade element theory. Since the flow of vertical axis wind turbine is more complex than that of horizontal axis, it is a typical large separation unsteady flow and is not suitable for analysis and design using blade element theory. This is also an important reason for the vertical axis. The wind turbine has not been developed sincea long time.
2. Wind power utilization rate
The wind power utilization rate of large horizontal axis wind turbines is mainly calculated by blade designers and is generally above 40%. As mentioned earlier, Due to the flaws in the design method itself, the accuracy of wind energy usage thus calculated is very questionable. Of course, wind turbines at wind power plants will plot wind power curves based on measured wind speed and power output. However, the wind speed at that time is the wind speed measured by the anemometer on the back of the wind wheel. as the speed and power of the incoming wind. The curve is too high and needs to be corrected. After applying the correction method, the wind energy utilization rate of the horizontal axis will be reduced by 30-50%. Concerning the rate of use of wind energysmall horizontal axis wind turbines, the China Aerodynamic Research and Development Center has conducted relevant wind tunnel experiments, and the measured utilization rate is between 23% and 29%.
3. Structural characteristics
During rotation, the blades of the horizontal axis wind turbine are affected by the combined effects of the force of inertia and gravity. The direction of the inertial force changes at. at any time. The direction of gravity remains unchanged, the blade is therefore subjected to an alternating load, which is very detrimental to the fatigue life of the blade. In addition, horizontal axis generators are placed at an altitude of tens of meters, which brings a lot of inconvenience to the installation, maintenance and inspection of generators.
The blades of the vertical axis wind turbine are much better stressed during rotation than those of the horizontal axis. Since the direction of the inertial force andgravity always remains unchanged, the blades are subjected to a constant load. The fatigue life is longer than that of horizontal axis wind rotors. At the same time, the vertical axis generator can be placed under the wind wheel or on the ground for easy installation and maintenance.
4. Start-up wind speed
There is a consensus that the start-up performance of horizontal axis wind turbines is good. However, depending on the wind speed of small horizontal axis wind turbines driven. the China Aerodynamic Research and Development Center According to tunnel experiments, the starting wind speed is generally between 4-5m/s, and the maximum reaches 5.9m/s. Such startup performance is obviously unsatisfactory. There is also an industry consensus that the starting performance of vertical axis wind turbines is poor, especiallyr for Darrieus type Ф wind turbines, which have no automatic start capability, which is also a reason that limits the application of the vertical wind turbine. axis wind turbines. However, for the Darrieus type H wind wheel, the conclusion is the opposite. According to the author's research, as long as the aerodynamic profile and installation angle are correctly selected, fairly good starting performance can be achieved. Judging from tunnel experiments, the starting wind speed of this Darrieus type H-shaped wind rotor only needs 2m/s. , which is better than the horizontal axis wind turbine mentioned above.
How to make a vertical axis wind turbine
The wind-solar hybrid street light is a public lighting system that uses wind energy to produce electricity. It combines wind turbines with street lights and generates. electricity thanks to the wind turbine. Electric energy foode public lighting, allowing sustainable use of energy. When choosing the axial direction of a wind turbine, the vertical axis and horizontal axis have their own advantages and applicable scenarios.
First of all, vertical axis wind turbines have the following advantages:
1. Strong adaptability: Vertical axis wind turbines can operate in various wind directions and are not affected by wind.Directional restrictions. This means it can work in complex urban environments, such as high-rise buildings, trees and other places that affect wind direction.
2. Simple structure: The structure of the vertical axis wind turbine is relatively simple. Due to the symmetry of its design, it does not need to follow the direction of the wind, so it can reduce complexity and breakdowns. rate of mechanical components.
3. Good silence: the blades of worm-axis wind turbinestical produce relatively little noise when rotating, which can reduce interference with the environment.
However, horizontal axis wind turbines also have their unique advantages:
1. High efficiency: The blades of horizontal axis wind turbines can be adjusted according to the wind direction to achieve the best wind energy utilization efficiency. This gives horizontal axis wind turbines an advantage in terms of wind energy conversion efficiency.
2. High stability: The structure of the horizontal axis wind turbine is relatively stable and can better withstand the impact and changes in wind force. This makes horizontal axis wind turbines more reliable in adverse weather conditions.
3. Easy Maintenance: The mechanical components of horizontal axis wind turbines are relatively easy to maintain and replace because they are usually located on the ground and do not require pclimbing ace for maintenance.
In summary, both vertical axis and horizontal axis wind turbines have their own advantages in different scenarios. For wind-solar hybrid street lighting systems, if the environment around the street lights is complex and the wind direction is variable, vertical axis wind turbines are more suitable if the wind direction at the location is street lights are relatively stable and wind power is high; efficiency of use is required, horizontal axis wind turbines are more suitable. Therefore, when selecting the axial direction of a wind turbine, overall considerations should be taken into account based on specific application scenarios and needs.
1. Wind turbine production requires a set of gears between the blade shaft and the generator shaft to change the rotation speed. Because the general fan shaft is relativement small and the rotation speed is slow.
2. It is necessary to install a large gear plate, and then connect a small gear plate to the generator rotor shaft. Rotational speed is directly proportional to the gear size ratio. This part is the power unit. Wind turbines use kinetic energy to convert it into electrical energy. ?
3. Generator part. Finished products are available for purchase in this section. The principle of a generator is exactly opposite to that of an electric motor. One is to convert electrical energy into energy and the other is to convert electrical energy into electrical energy.
4. Simply purchase a DC generator and install the blades. Solar generators are not easy to make yourself. You can purchase solar batteries and assemble them to complete the vertical axis wind turbine.