Development and analysis of vertical-axis wind turbines - Wind Power Generation and Wind Turbine Design - page 288

Figure 8: Three blade variable pitch VAWT developed by Kirke [ 25 ] clearly
showing the counterweights incorporated in the blade pitch mechanism
(photograph

− copyright Brian Kirke).

2.2.5 Other designs and innovations
The fi eld of wind energy systems has attracted many inventors and researchers
over the years and in the fi eld of VAWT innovation there has been a veritable
plethora of designs put forward and, in many cases, demonstrated. However, there
is little evidence in the academic literature that any of the relatively exotic designs
will eventually be developed to the point of being competitive for electricity
generation when compared with large, three-bladed HAWTs.
A class of VAWTs that have been investigated by a number of inventors include
drag-based machines, or panemones [1]. One interesting device utilises a mechani-
cally pitched blade which pitches through 180° during the course of one revolution
of the rotor. The earliest technical paper related to this type of machine is thought
by the author to be the description of the “Kirsten-Boeing Propellor” by Sachse
[28], which was developed as a propeller for airships. Others have used the same
principle to devise a wind turbine, rather than a propeller, and this is illustrated in
Fig. 9 where it can be seen that the leading edge of a blade becomes the trailing
edge on successive revolutions of the rotor. It can also be seen that such a device
is strictly not a drag machine as lift may play a signifi cant part in the development
of the torque over a substantial fraction of the blade travel around the rotor.