What Is A Horizontal Axis Wind Turbine?

A wind turbine is basically a very large inverse fan, where wind is the input and electricity is the output. Today there are hundreds of different wind turbine deigns, most of them range from around 40 – 80m in height; 50 – 85m in span and 850kW to 4.5MW in power. Most of these wind turbines have 3 blades and possess horizontal axis shafts.

Wind turbines can be broadly classified into two types: Horizontal axis wind turbines Vertical axis wind turbines Figure 4.1: HAWT and VAWT

Source: Harvesting the Wind – The Physics of Wind Turbines

Horizontal Axis Wind Turbine (HAWT)

In case of a horizontal axis wind turbine, the plane of the rotor rotates such that the wind direction is perpendicular to it. This allows the wind to flow around the blades, thus causing them to rotate around the hub. As the blades rotate, this causes a rotation of the shaft which is then coupled with a gearing system to step up the speed of the generator. The generator converts mechanical energy into electricity which is passed on to the grid.

However, they do need uniform wind flow and fail to perform well under turbulent wind conditions.

Vertical Axis Wind Turbine (VAWT)

In case of vertical axis wind turbines the main rotor shaft is vertical with respect to the ground. The major advantage of these turbines is that they work well even in turbulent wind conditions as they do not need to be pointed directly at the wind. Therefore, they are widely adopted in residential areas.

Another major benefit of such installations is that the gearbox is placed near the ground and is thus easily accessible. In case of HAWT the gear box is right behind the hub, which makes maintenance