Difference between Horizontal Axis and Vertical Axis Wind Turbines


A Wind Turbine is a device which uses kinetic energy of blowing wind to generate electrical energy. A wind turbine consists of two or three rotor blades which are mounted on a rotor. When the blowing wind exerts a lift and drag force on these blades, the rotor starts rotating. A main shaft is attached to the rotor which is connected to an electric generator on the other end. The generator produces electricity when driven by the wind turbine.

Depending on the axis of rotation, the wind turbines are classified into two types −

  • Horizontal Axis Wind Turbine
  • Vertical Axis Wind Turbine


Let's start with some basics of these two types of turbines so that it becomes easy to understand the differences between them.

What is a Horizontal Axis Wind Turbine (HAWT)?

The type of wind turbine in which the axis of its rotation is parallel to the flow of air stream is known as horizontal axis wind turbine or HAWT. The horizontal axis wind turbine is the most successful type of wind turbine and it is most widely used world-wide. The horizontal axis turbine is mainly used for generation of electricity for commercial purposes in different parts of the world.

The horizontal axis wind turbines have comparatively low cut in wind speed and have a high power coefficient. Although, the design of HAWT is relatively more complicated and costly because it requires a gearbox and an electric generator placed at the top of the tower.

The major components that a horizontal axis wind turbine consists are: turbine blades, hub, gearbox, generator, tower, nacelle, yaw control (to orient the turbine in the direction of wind).

What is a Vertical Axis Wind Turbine (VAWT)?

The type of wind turbine in which the axis of rotation of the turbine and the flow of air stream are perpendicular to each other is known as vertical axis wind turbine or VAWT. The vertical axis wind turbine is also known as cross-wind axis turbine.

The one of the major advantage of the vertical axis wind turbines is that they can receive wind from any direction. Therefore, these turbines do not require the yawing control mechanism to orient them in the direction of wind.

The design of a vertical axis wind turbine is comparatively less complicated and less expensive because in case of these turbines, the gearbox and generator are installed at the bottom of the tower. Consequently, the installation of the vertical axis wind turbine is simple as compared to horizontal axis wind turbine.

Although, the vertical axis wind turbines are generally not self-starting, therefore, a starting mechanism is used to start them from stationary position. Another major disadvantage of the vertical axis turbines is that they have a low power coefficient. The main components of a typical vertical axis wind turbine are: tower (acts as a rotor shaft as well), rotor blades, support structure.

Difference between Horizontal Axis and Vertical Axis Wind Turbines

Both horizontal axis and vertical axis wind turbines use the kinetic energy of wind to drive an electric generator, however there are several differences between them that are highlighted in the following table −

Basis of Difference Horizontal Axis Wind Turbine Vertical Axis Wind Turbine
Definition A horizontal axis wind turbine is the one whose axis of rotation is horizontal. A wind turbine is called a vertical axis wind turbine if its axis of rotation is vertical.
Abbreviated name HAWT is the abbreviation used for horizontal axis wind turbine. VAWT is the abbreviation used to denote the vertical axis wind turbine.
Axis of rotation with respect to wind stream For the horizontal axis wind turbine, the axis of rotation of turbine is parallel to the wind stream. For the vertical axis wind turbine, the axis of rotation of the turbine is perpendicular to the wind stream.
Location of electric generator In the horizontal axis wind turbine, the electric generator is installed at the top of the tower. In the vertical axis wind turbine, the generator is installed on the ground.
Location of gearbox In HAWT, the gearbox is installed at the top of the turbine tower. In VAWT, the gearbox is installed at the bottom of the turbine.
Need of yaw mechanism In the horizontal axis wind turbine, the yaw mechanism is required to orient the turbine in the direction of wind. The vertical axis wind turbine does not require yaw mechanism because it receives wind from all directions.
Self-starting Horizontal axis wind turbine is self-starting. Vertical axis wind turbine is not self-starting, hence a starting mechanism is required to start it from stationary position.
Design and installation The design and installation of a horizontal axis wind turbine is complex. The design and installation of a vertical axis wind turbine is comparatively simple.
Operation space of blades Horizontal axis wind turbine requires large space for blade’s operation. Vertical axis wind turbine requires small space for blade’s operation.
Dependency on wind direction The operation of horizontal axis wind turbine is dependent on wind direction. The operation of vertical axis wind turbine is independent of the wind direction because it receives wind from all directions.
Height from ground The height of the horizontal axis wind turbine from ground is large. The vertical axis wind turbine is installed at comparatively smaller distance from the ground.
Need of nacelle In case of horizontal axis wind turbines, a heavy nacelle is installed at the top of the tower. There is no need of nacelle in case of vertical axis wind turbines.
Power coefficient Horizontal axis wind turbine has a high power coefficient. Vertical axis wind turbine has a low power coefficient.
Tip speed ratio (TSR) Horizontal axis wind turbine has high tip speed ratio. Vertical axis wind turbine has considerably low tip speed ratio.
Noise produced The operation of horizontal axis wind turbine is noisy. Vertical axis wind turbines produce comparatively less noise.
Efficiency The ideal efficiency of horizontal axis wind turbine is around 50% to 60 %. The ideal efficiency of vertical axis wind turbine is usually more than 70%.
Hindrance for birds Horizontal axis wind turbines cause high obstruction for birds. Vertical axis wind turbines cause less hindrance for birds.
Cost Horizontal axis wind turbines are more expensive due their complex design and installation. Vertical axis wind turbines are less expensive because their design and installation is quite simple.

Conclusion

The most significant difference that you should note here is that a Horizontal Axis Wind Turbine has its axis of rotation parallel to the wind stream, whereas a Vertical Axis Wind Turbine has its axis of rotation perpendicular to the wind stream. Both these types of turbines use the kinetic energy of blowing wind to drive an electric generator to produce electricity.

Updated on: 22-Sep-2022

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