Efficiency has nothing to do with wind speed, and high efficiency can be achieved at low wind speeds. (The efficiency of mechanical parts is not taken into account)
According to energy conservation, the power of the wind turbine is related to the wind speed
According to aerodynamics and Bates limit theory, the wind energy utilization rate of the wind turbine The limit is 59%
Each wind turbine has an energy utilization rate fixed maximum wind turbine. This efficiency is related to the tip speed ratio of the wind turbine (the ratio between the tip speed of the blade and the current wind speed).
For example, an optimal tip speed ratio (i.e. the peak speed ratio when the highest wind energy utilization rate is achieved) is 9. The wind turbine has a rotor diameter of 100 m and a speed d 12 tower wind turbine. It then has the highest yield at 3.14*100*12/60/9=7m/. s
Why are wind turbines vertical and not horizontal?
Give you a rough calculation method: fan power = 1/2*Cp^P*S*v^3. Among them, Cp is the utilization rate of wind energy. the current fan is 0.35 ~ Between 0.4, then the fan power = 0.5*0.4*1.3*20*12*12*12=898.56W. The fan power is always lost. If your energy production efficiency is 80%, then it is 898.56. *80%. First of all, it should be noted that once the wind turbine exceeds the rated wind speed (usually 7-8 meters per second), certain measures will be taken to stabilize the generator power. So this does not mean that the higher the wind speed, the higher the generator power.
The differences between horizontal axis and vertical axis wind turbines lie in the following aspects:
1. Design method
The design ofblades of horizontal axis wind turbines, The momentum-sheet element theory is commonly used and the main methods include the 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 inaccuracy 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 axis wind turbine bladesvertical 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 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 will trace curves ofwind power based on the measured wind speed and power output. However, the wind speed at this time is the wind speed measured by the anemometer on the back of the wind wheel. It is lower than the incoming wind speed, and the wind power curve is 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 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 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. Cependant, depending on the wind speed of small driven horizontal axis 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. According to experiencesIn tunnel, the starting wind speed of this Darrieus type H-shaped wind turbine only needs 2 m/s. , which is better than the horizontal axis wind turbine mentioned above.