CE QUE VOUS VOULIEZ SAVOIR SUR
Combien de pales pour une
In simple terms, a wind turbine
rotor with few blades produces less torque but spins faster than a rotor
with many blades. So the power output is similar in both cases.
In theory, turbines extract
the most energy from wind (estimated to be 59 per cent of the wind's total
energy) when the wind speed ahead of the turbine is exactly three times
the wind speed in its wake. Because each blade on a turbine rotor extracts
energy and slows the wind by a certain amount per revolution, the multi-bladed
rotor must rotate more slowly than one with fewer blades to maintain an
optimum wind-speed ratio.
If a rotor has a very high
number of blades, aerodynamic interference between them will reduce power.
However, it will produce very good torque at low wind speeds, hence the
use of the many-bladed design for powering water pumps in rural areas.
But for generating electricity,
high speed and low torque are favoured: generators typically require high
rotation speed, and low torque means that shafts and gearboxes can be of
lighter construction. So a small number of blades is preferable. But because
single-blade and two-blade rotors suffer harmonic problems dangerous
vibrations at certain resonant speeds and are displeasing to the
eye, three-bladed rotors are the ideal choice. They are well-balanced,
aesthetically pleasing and offer a high enough speed of rotation. Further
blades add to manufacturing costs and, if designed to maintain a high rotation
speed, would have to be very slender and, as a consequence, structurally
=> Les rotors à
pales sont le choix idéal. Ils
sont bien équilibrés, esthétiquement satisfaisants
et permettent une assez haute de vitesse de rotation.