# Small wind turbines are classified according to design methods and structures

The efficiency of a small wind turbine is very high, but it is not composed of a generator, but a small system with a certain technological content; wind turbine + controller + energy storage device. A wind turbine is composed of a generator, a rotating body, a tail, and a blade. Each part is very important, and the function of each part is: the blade is used to receive the wind and the wind energy is converted into electrical energy through the generator: the tail keeps the blades always facing the incoming wind The direction to obtain the maximum wind energy: the rotating body can make the generator rotate flexibly to realize the function of adjusting the direction of the tail: the rotor of the small generator usually uses permanent magnets, and the rotation of the rotor causes the stator winding to cut the magnetic lines of force to generate electricity.
Small wind turbines can be divided into vertical axis wind turbines (VAWT) and horizontal axis wind turbines (HAWT) according to their design and structure. The axis of rotation of horizontal-axis wind turbines is parallel to the wind direction. Most horizontal-axis wind turbines have blades that change with the wind direction, so they must constantly adjust their positions, so they are more susceptible to the influence of terrain and ground objects. The rotation axis of the vertical axis wind turbine is perpendicular to the wind direction. Its advantage is that the design is relatively simple, and the direction does not need to be adjusted with the change of the wind direction. It can be divided into an egg-shaped rotor (Darrieus) and a barrel-shaped rotor (Savonius).
①Horizontal axis wind turbine
A wind turbine whose installation position of the wind wheel axis and the horizontal plane is not greater than 15° is called a horizontal axis wind turbine. The wind wheel of a horizontal axis wind turbine rotates around a horizontal axis. The blades are arranged radially, perpendicular to the axis of rotation, and at an angle to the plane of rotation of the wind wheel (called the installation angle). Horizontal axis wind turbine blades are shown in Figure 1.

Horizontal-axis wind turbines can be lift devices (ie, lift-driven wind wheels) or drag devices (ie, resistance-driven wind wheels). Most horizontal-axis wind turbines have anti-wind devices. For small wind turbines, generally Tail rudder. There are three types of horizontal-axis wind turbines: traditional windmills, low-speed wind turbines and high-speed wind turbines.

Vertical axis wind turbine
The wind wheel of the vertical axis wind turbine does not adjust its direction with the change of the wind direction. The wind wheel of the vertical axis wind turbine rotates around a vertical axis, and the wind wheel axis is perpendicular to the wind direction. Its advantage is that it can accept wind from any direction, so when the wind direction changes, there is no need to face the wind. Since no steering device is needed, its structural design is simplified. Another advantage of the vertical axis wind turbine is that the gearbox and generator can be installed on the ground for easy maintenance.
The common structures of vertical-axis wind turbines include “S” type wind wheels, Darrieus type wind wheels and rotary wing wind wheels.

The comparison between vertical axis wind turbine and horizontal axis wind turbine is shown in Table 1.