29-04-2014, 04:26 PM
DESIGN AND FABRICATION OF VERTICAL AXIS WIND TURBINE
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VERTICAL AXIS WIND TURBINE
Vertical-axis wind turbines (VAWTs) are a type of wind turbine where
the main rotor shaft is set vertically. Among the advantages of this
arrangement are that generators and gearboxes can be placed close to the
ground, and that VAWTs do not need to be pointed into the wind. Major
drawbacks for the early designs (Savonius, Darrieus, giromill and
cycloturbine) included the pulsatory torque that can be produced during
each revolution and the huge bending moments on the blades. Later designs
solved the torque issue by using the helical twist of the blades almost
similar to Gorlov's water turbines.
A VAWT tipped sideways, with the axis perpendicular to the
wind streamlines, functions similarly. A more general term that includes
this option is "transverse axis wind turbine". For example, the original
Darrieus patent , includes both options.
Drag-type VAWTs, such as the Savonius rotor, typically operate
at lower tipspeed ratios than lift-based VAWTs such as Darrieus rotors and
cycloturbines.
GIROMILL WIND TURBINE
A subtype of Darrieus turbine with straight, as opposed to curved, blades. The
cycloturbine variety has variable pitch to reduce the torque pulsation and is
self-starting.The advantages of variable pitch are: high starting torque; a
wide, relatively flat torque curve; a lower blade speed ratio; a higher
coefficient of performance; more efficient operation in turbulent winds; and a
lower blade speed ratio which lowers blade bending stresses. Straight, V, or
curved blades may be used.
SAVONIUS WIND TURBINE
Savonius turbines are one of the simplest turbines. Aerodynamically, they
are drag-type devices, consisting of two or three scoops. Looking down on
the rotor from above, a two-scoop machine would look like an "S" shape in
cross section. Because of the curvature, the scoops experience less drag
when moving against the wind than when moving with the wind. The
differential drag causes the Savonius turbine to spin. Because they are drag-
type devices, Savonius turbines extract much less of the wind's power than
other similarly-sized lift-type turbines. Much of the swept area of a Savonius
rotor may be near the ground, if it has a small mount without an extended
post, making the overall energy extraction less effective due to the lower
wind speeds found at lower heights.
SHAFT DESIGNING
While designing the shaft of blades it should be properly fitted to
the blade. The shaft should be as possible as less in thickness &
light in weight for the six blade, the shaft used is very thin in size
are all properly fitted. So no problem of slipping & fraction is
created, it is made up of hollow Aluminum which is having very
light weight. Length of shaft & diameter are 18 inches & 2.54cm
respectively. And at the top and bottom ends mild steel of length
1inch each are respectively are fixed to give strength to the hollow
shaft.
CONCLUSION
• Our work and the results obtained so far are very encouraging and
reinforce the conviction that vertical axis wind energy conversion
systems are practical and potentially very contributive to the
production of clean renewable electricity from the wind even under
less than ideal sitting conditions. It is hoped that they may be
constructed used high‐strength, low‐ weight materials for
deployment in more developed nations and settings or with very
low tech local materials and local skills in less developed countries.
The Savonius wind turbine designed is ideal to be located on top of
a bridge or bridges to generate electricity, powered by wind. The
elevated altitude gives it an advantage for more wind opportunity.
With the idea on top of a bridge, it will power up street lights and
or commercial use. In most cities, bridges are a faster route for
everyday commute and in need of constant lighting makes this an
efficient way to produce natural energy