Maximum energy production value. The utility factor of a wind power plant is the maximum value of electricity production. Wind power plants are electrical equipment that uses wind turbines to convert wind energy into mechanical work. The mechanical work causes the rotor to rotate and ultimately produces alternating current. Wind turbines consist of wind turbines, generators, deflectors, towers, speed-limiting safety mechanisms and energy storage devices.
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 momentum-sheet element theory is commonly used, and the main methods include Glauert method, Wilson method, etc. However, as blade element theory ignores the flow interference between eache blade element, and at the same time ignores the airfoil strength 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 vertical-axis wind turbine blades was formerly based on the horizontal-axis design method and relied on blade element theory. Since the flow of the vertical axis wind turbine is more complex than that of the horizontal axis, it is a typical unsteady flow atlarge separation 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, 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 highevated and must 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 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 tens of meters above sea level, which brings a lot of inconvenience for 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, vertical axis generators can be placed at the bottom of the wind turbine or on the ground, it is easy to install and maintain.
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. One summerThe 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 from tunnel experiments, the starting wind speed of this Darrieus type H-shaped wind rotor only needs 2 m/s. , which is better than the horizontal axis wind turbine mentioned above.