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Conceptualisation
This chapter begins with the definition of important terminology that is necessary to com-
prehend prior to reading the subsequent description of numerous different wind turbines
and their properties. The chapter continues with a systematic evaluation and technical
assessment of several wind turbine candidates and concludes with the selection of the
most suitable type of wind turbine.
4.1 Terminology
The following sections of this project thesis use several terms and expressions that are
mainly utilised within the field of wind turbine technology. With reference to making the
following sections more comprehendible to engineers without a background in wind tur-
bine technology, the present section gives a brief introduction to basic wind turbine theory
and defines significant terminology.
� Wind and wind power
The phenomenon wind is caused by movement of the air between low pressure and high
pressure regions. These regions arise due to uneven heating of the earth’s surface by the
sun. The air above a hot surface rises when it is heated and creates a low pressure zone.
The surrounding cold air flows towards the low pressure region and thus creates wind. For
the same reason wind energy is sometimes called indirect solar energy. Wind varies in
both intensity and direction as a function of time and it is greatly affected by factors such
as ground features and altitude [9, p. 1].
Distinction is generally made between the terms wind turbine and windmill. When the
energy is used directly for e.g. grinding, cutting and pumping, the machine is called a
windmill. When the energy is converted into electrical energy, the machine is called a wind
turbine [10, p. 57]. This project thesis will focus primarily on wind turbines, which harvest
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