Types of wind turbine:

Basically there are two main types of wind turbine: the horizontal­ axis (HAWT) and the vertical axis (VAWT).

Vertical axis

The early windmills were vertical-axis machines, but they were later found to be inefficient. The technological advancement of the odd-shaped, vertical-axis machine came about in the 1930s, when a Frenchman named G.J.M. Darrieus invented a wind turbine built on an “egg-beater” design (picture below). In the early 1970s, his idea was refined by re­searchers who called their device a vertical-axis wind turbine (VAWT). Unlike turbines with big propellers that turn on a horizontal axis, its blades spin in a vertical-axis - the main advantage is that it accepts winds from all directions.

Above – The Darrieus vertical-axis rotor.

Above - The Savonius wind turbine which is a vertical-axis turbine.

Propeller-style turbines have to be pointed into the wind and therefore need equipment to sense wind direc­tion and to turn the propellers to face the right way. However, the egg-beater style turbine has its generator and control devices on the ground which make them easy to reach.

The main disadvantages of the VAWT turbines are that they are not self-starting and they do not generate electricity at a constant rate. Also, for the same area of land, less electricity is generated by a VAWT than a HAWT.

Above - The large vertical-axis wind turbine, originally installed on Rottnest Island off the coast of Western Australia.
Source: Western Power’s World of Energy.

Horizontal Axis

Above - A horizontal-axis modern wind turbine - utilising a propeller blade.

These machines are commonly known as propeller-type turbines. The rotors (or blades) are usual­ly made of wood composite or fibreglass. Nearly all of the current wind turbines (and windmills) are the horizontal-axis type. However, there are a number of constraints to their design. Studies and experience have shown that issues such as telecommunication interference, noise, shadow flicker and bird impacts all need to be considered in the location of these wind turbines.

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