Wind for electricity generation
(Please bear in mind that model design varies considerably.)
2/3 blade upwind
Start-up wind speed
Cut-in wind speed
Rated wind speed
Furling wind speed
Permanent Magnet Alternator
Max. Power Output
Table 2 : Small Wind Energy System for Battery Charging Turbine Specifications
Depending on the availability of materials,
blades can be made locally from laminated
wood, steel, aluminium, fibre glass or
combinations of these materials.
Fibre glass blades use a mould, which can be
used to make multiple blades.
Two halves of the fibre-glassed mould is shown
in the photograph.
Once constructed, the rotor blade is subjected to
a process of dynamic and static balancing.
Wind Rotor Blade Construction
Fibre glass wind turbine blade: manufacturing
guide. Version 1.4
Figure 4 : Mr. W.A. Fernando of the Dinusha Marine
Works in Panadura manufacturing blades for small
wind systems. Photo: Practical Action South Asia.
This part of the turbine converts the rotational motion of the
blades and the axle into electrical energy.
The Practical Action Permanent Magnet Generator, (PMG)
produces low voltage, 'three-phase' AC, and then changes it
into 'direct current' (DC) for charging 12 volt batteries.
The permanent magnet generator is also referred to as an
‘alternator’ because it generates alternating current (AC) but
does not generate 'mains voltage' or 'utility power' AC.
Rectifiers are connected to the stator to produce direct
The design of the PMG is suitable for low volume
manufacture in developing countries. More information on
how to make a permanent magnet generator can be found in
the document The Permanent Magnet Generator (PMG): A
manual for manufacturers and developers.
Figure 5 : making a PMG in Sri
Lanka. Photo: Practical Action South
The Permanent Magnet Generator (PMG)
NB: large file 1.33MB