Advantages and disadvantages of vertical axis wind turbines, differences between vertical axis wind turbines and horizontal axis wind turbines

Advantages and disadvantages of vertical axis wind turbines
Advantages of vertical axis wind turbines
1. The overall performance indicators are high. In terms of construction, a double pivot design with straight blades and triangles is used, and the main force point is concentrated on the hub, solving the problems of blade detachment, fracture, and flying out. The blades of the vertical axis wind turbine form a circle with the same angle difference, which can reduce the pressure on the central support; In addition, a series of auxiliary equipment such as gearboxes, gearboxes, and transmission devices can be placed on work platforms relatively close to the ground, reducing the weight of the fan itself and to some extent reducing the construction and maintenance costs of the fan. Vertical axis fans can also be used for building integration, which is beneficial for urban construction.
2. Reduce noise pollution. Adopting the principles of horizontal plane rotation and blade application in aircraft wing design, the noise is reduced to a level that cannot be measured in natural environments.
3. No need to install auxiliary systems. Compared with horizontal axis wind turbines, vertical axis wind turbines have blade rotation planes parallel to the ground, which allows wind energy to be obtained from various directions without the need to add yaw devices to adjust the direction of receiving wind energy like horizontal axis wind turbines. The overall structure is simpler, which reduces the vibration generated by wind turbine operation to a certain extent and improves its reliability.
4. Strong wind resistance. The principle of horizontal rotation and triangular double pivot design allows it to withstand less wind pressure and can withstand typhoons up to 45 meters per second.
5. The blade structure is simple. Due to the enhanced ability of vertical axis wind turbine blades to capture wind energy, when the blades rotate under wind force, they are only subjected to the pressure of the wind turbine and the tension of the rotating centrifugal force on the blades. Therefore, the requirements for blade materials are reduced, and the selected materials are more universal, reducing the cost of purchasing blades.
6. The speed range has increased. Compared to horizontal axis wind turbines, vertical axis wind turbines can achieve a much higher maximum speed and have better operational stability under strong wind speeds. They can withstand high-intensity wind speeds of up to 60m/s. As long as the control strategy and material selection of the wind turbine are appropriate, the utilization of wind energy by vertical axis wind turbines is much greater than that of horizontal axis wind turbines.
Disadvantages of vertical axis wind turbines:
Firstly, the starting performance indicators of vertical axis fans are worse than those of horizontal axis fans. Secondly, during one rotation of the blades, negative torque is generated at some positions, resulting in low output efficiency of the fan; The third common issue for all wind turbines is the problem of anti vibration, especially for large wind turbines; Fourthly, due to the fact that wind is an uncertain real-time variable, the stability of the output power of wind power generation is not as good as that of traditional thermal power generation, resulting in large fluctuations and difficulty in grid connection.
The difference between vertical axis wind turbines and horizontal axis wind turbines
Difference 1: Leaves
The blade design of horizontal axis wind turbines generally adopts the momentum blade element theory, and the interference between the blades of the wind turbine is also very strong. The entire flow is very complex, and it is impossible to obtain accurate results solely based on blade element theory.
The blade design of vertical axis wind turbines used to be based on the horizontal axis design method, relying on blade element theory. Due to the fact that the flow of a vertical axis wind turbine is more complex than that of a horizontal axis, it is a typical large separation unsteady flow and is not suitable for analysis and design using blade element theory.
Difference 2: Structure
The blades of a horizontal axis wind turbine are subjected to a combined effect of inertial force and gravity during one rotation. The direction of inertial force changes at any time, while the direction of gravity remains unchanged. As a result, the blades are subjected to an alternating load, which is very detrimental to their fatigue strength. In addition, horizontal axis generators are placed at heights of tens of meters, which brings a lot of inconvenience to the installation, maintenance, and repair of the generators.
The blades of a vertical axis wind turbine experience much better force during rotation than those of a horizontal axis wind turbine. Due to the constant direction of inertia and gravity, they are subjected to a constant load, resulting in a longer fatigue life than a horizontal axis wind turbine. Meanwhile, the vertical axis generator can be placed under the wind turbine or on the ground for easy installation and maintenance.
Difference 3: Starting wind speed
It is a consensus that the starting performance of horizontal axis wind turbines is good, but according to wind tunnel experiments conducted by the China Aerodynamics Research and Development Center on small horizontal axis wind turbines, the starting wind speed is generally between 4-5m/s, with the maximum reaching 5.9m/s. Such starting performance is clearly unsatisfactory. It is also a consensus in the industry that the starting performance of vertical axis wind turbines is poor, especially for Darrieus type Ø - shaped wind turbines, which have no self starting ability at all. This is also a reason that limits the application of vertical axis wind turbines. However, there is an opposite conclusion from Youchanghu regarding the Darrieus style H-shaped wind turbine. According to the author's research, as long as the airfoil and installation angle are selected appropriately, quite good starting performance can be achieved. Through wind tunnel experiments of double turbine vertical axis wind turbines, vertical axis wind turbines, and squirrel cage vertical axis wind turbines, the starting wind speed of this Darrieus type H-shaped wind turbine only needs 2m/s, which is better than the horizontal axis wind turbines mentioned above.
Which type of vertical axis wind turbine is good?
It can be divided into four types: cantilever, load balancing, integrated wind turbine and generator, and separated. After comparison, it is found that:
(1) The load balanced vertical axis wind turbine adopts a symmetrical layout in structural design, especially in the main components, which greatly improves the operational performance, service life, and assembly process performance of the vertical axis wind turbine structurally. The overall structural dimensions of this product are small, with good assembly processability, convenient transportation and installation, and good maintenance performance. Compared with traditional vertical axis wind turbines, it has significant technical and cost advantages.
(2) The separated wind turbine ensures the operating efficiency of the new load balanced vertical axis wind turbine from the principle and structure, greatly improves the operating life, and has the advantages of good maintenance performance, easy installation, and low overall manufacturing cost. Therefore, separated wind turbines have great practical value and also have promotional value for vertical axis wind turbines of the same type but different power.