Wind Turbine Blade Design

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Figure 6.
Schematics of smart structure concepts. 
Figure 7.
Comparison of aerodynamic device concepts in terms of lift control capability [31]. 
Smart actuator materials include conventional actuators, smart material actuators, piezoelectric and 
shape memory alloys. Traditional actuators probably do not meet minimum requirements for such 
concepts. Furthermore, proposed concepts of aerodynamic control surfaces (distributed along the blade 
span) require fast actuation without complex mechanical systems and large energy to weight ratios. 

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Energies 2012, 5 
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Promising solution for this purpose is the use of smart material actuator systems. By definition,
smart materials are materials which possess the capability to sense and actuate in a controlled way
in response to variable ambient stimuli. Generally known types of smart materials are 
ferroelectric materials (piezoelectric, electrostrictive, magnetostrictive), variable rheology materials 
(electrorheological, magnetorheological) and shape memory alloys. Piezoelectric materials and shape 
memory alloys are generally the most famous smart materials used in actuators in various applications. 
The development of their technology has reached a quite high level and commercial solutions are 
available and widely used [31]. 
5.8. Blade Shape Summary 
An efficient rotor blade consists of several aerofoil profiles blended at an angle of twist terminating 
at a circular flange (Figure 8) [4,34]. It may also include tip geometries for reducing losses. To 
facilitate production, several simplifications maybe made: 
 
Reducing the angle of twist. 
 
Linearization of the chord width. 
 
Reducing the number of differing aerofoil profiles. 
All manufacturing simplifications are detrimental to rotor efficiency and should be well justified. 
The introduction of new moulding techniques and materials has allowed the manufacture of 
increasingly complex blade shapes. However, the economics of production coupled with difficulty of 
design analysis still dictate final geometry. Leading wind turbine suppliers now include most 
optimisation features such as angle of twist, variable chord length and multiple aerofoil geometries. 
Figure 8.
A typical modern HAWT blade with multiple aerofoil profiles, twist and linear 
chord length increase. 

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Energies 2012, 5