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When we
hear the term wind turbine we all think that it is some device which gives out
useful electricity using wind energy as its input. To have a more elaborated picture of process real
mechanism involved behind in this simple yet very beneficial process, let us
think “How the wind power works?”

 

As we know
that obsolete Dutch windmill design which solely used wind’s force to move the
blades around the center hub, unlike in the modern and advanced turbines are
amended by more and more science and technology is incorporated into the design
of blades, the best example for this is the utilization
of aerodynamic principles for blade design so that to extract wind’s energy
effectively. For rotating the wind turbine rotors two primary forces of
aerodynamics are been considered Lift and drag. Drag acts parallel to the
direction of flow whereas lift acts perpendicular to the direction of wind
flow.

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Most of us
are not aware that the turbine blades are designed using a lot similar concept
of airplane wings, with one side of the blade being flat and another side kind
of curved surface. Lift phenomenon is very complex to understand and explain,
to put it in simple words the using the above figure ( ??),  When wind gliding over the curved surface of
the blade it has to move faster in order
to match with the wind travelling across the flat surface, during this
process  the faster moving blade across
the curved surface end tends to rise in the atmosphere
and creating a low-pressure pocket just above it and this low-pressure pocket
tends to SUCK the blade in a downward direction,
which can be termed as “Lift” effect. On another
hand, the wind gliding across the flat
surface which will be traveling
relatively at a lower speed compared to
the wind traveling on the curved surface,
this creates a higher pressure which in turn pushes the blade in the same direction.

This
combination of suck and push actions of the blades in the same direction will keep the turbine blades and hence rotor hub rotating more efficiently in one direction.

So far we
had taken only aerodynamics into the picture,
but it is not the only factor involved in making wind turbines more effective.
Other factors to be considered are a) Size of the blades b) Tower height

Size of the blades: More energy
can be generated using the longer turbine blades. Which will lead to higher
rotor diameter. In general, with doubling
the rotor diameter produces four times increase in wind power. This can more
clearly understand by having wind power
equation.

P = (1/2) ?Av^3

P-  Wind power

? – Air density

A-    
Area = (?/4)D^2

V = velocity

 

In above equation, P is directly proportional to Area
and hence it is directly proportional to D^2, so by doubling diameter we can
have Power output increase by 4 times. 

But with an increase in Rotor diameter and blade sizes, it makes the installation and
transportation of blades and turbine setup more difficult and hence increase in
overall initial cost which is the drawback of larger blades. Also In areas with
lower wind speed smaller diameter rotor wind turbines could produce more
electricity in comparison with larger wind turbine setups, the reason being: at lower wind speeds, smaller turbines operate
to its maximum capacity and hence increasing overall output efficiency.

Tower
Height:   Height of the tower also plays an important
role in enhancing the generation capacity of the wind turbine unit, at a higher elevation,
the wind speeds are higher due to the uninterrupted
flow of winds, ground friction and
objects at ground level obstruct the wind
flow and hence reduces the wind speed. It is estimated by scientists that 12%
increase in wind speed with doubling the lower
elevation.

 

 

 

Components
of the wind turbine and its working:

 

 

 

 

Rotor blades: Blades are attached to the rotor hub,
as explained above with the unique blade surface design the wind turns the
blades and are main source and input to the rotor hub.  Blades are the one which converts wind energy
into mechanical energy with help of rotor hub and main shaft.

 

Rotor Hub: 
Rotor
hub is connected to the Main shaft and acts as input to the shaft. It spins
around capturing part of the kinetic energy from wind and turns the main shaft.

Main Shaft:  Shaft is connected to the rotor hub on one end
and gearbox on another end, which is
further connected to the Generator

Generator:  Generator converts from mechanical energy into
electrical energy using the properties of electromagnetic induction.

Nacelle:  Casing that holds gearbox, generator, ECU, yaw
controller & brakes.

Yaw controllers
are used to aligning the rotor hub in the
direction wind and brakes are used to restrict the blades to rotate beyond its
capacity. Many transmission and distribution components are used in between wind
turbine tower and electricity utilization point say home or office to deliver
the generated electricity in usable form

 

 

Classification of Wind turbines.

Based on the axis of rotation

VAWT – 
 Vertical axis wind turbines have
their axis of blades rotation vertical as indicated by its name and are very
rare to see in usage compared to its counterparts (HAWT). The rotor hub is long tube standing vertically
with upper and lower hub as in figure(??) .
The worlds tallest VAWT is built in Cap-Chat, Quebec.

 

 

 

Further VAWT are
classified in to

a)   
Drag based (figure (??) ),

b)   
Lift based. (left side image in figure (??) ),

HAWT –  Horizontal axis wind turbine have their axis
of rotation in the horizontal direction and
are very commonly seen wind turbines in most of the windy places.

 

 

Blade/ Bladeless: Turbines can also be classified as a blade and bladeless considering the recent
trends of the wind turbines which will be
discussed in detail in next section “Recent
trends in Wind turbines”.

 

Recent Trends in Wind Turbines:

 

Vortex bladeless

(http://www.vortexbladeless.com)

Advantages of Vortex blades:

–       
Less
maintenance

–       
Moving
generator from top to bottom, which will reduce installation and maintenance
cost

–       
Usage
of fiber-glass material for tower further
helps in a weight reduction of set up and
eases the installation process.

–       
No lubrication needed. Less Noisy. Eco-friendly.

–       
Huge reduction of carbon footprint.

–       
No gears or bearings. Vortex leads to a drastic reduction in material, manufacturing,
and maintenance.

–       
Vortex says its bladeless turbines will generate electricity
for 40 percent less than the cost of power from conventional wind turbines. ?

Drawback: Few wind turbine experts predict that: Startup Vortex Bladeless makes a
turbine that looks intriguing, but it may not solve wind power’s challenges.

 

 

–       

–       
 

 

 

Saphon wind turbines:

Saphon wind
turbines (bladeless horizontal axis wind turbines), No humming sound and a drastic
reduction in harm caused to bats and birds in comparison to conventional
blade wind turbines.

Saphon energy is
Tunisian green energy startup, these
bladeless wind turbines are designed with the concept of design of the sails of a ship which promises the
conversion of kinetic energy into electrical energy with having twice the
efficiency and half the cost of the conventional wind turbines.

Saphonian
turbines incorporate “Zero blade
technology” which is patented system for harvesting wind energy. It involves
channeling the wind back and forth till the wind energy is converted into
mechanical energy using pistons. Further conversion from mechanical to
electrical energy takes place using hydraulic motor and a generator

 

 

Wind Tamer: (ducted wind turbine)

 

 

 

 

 

It is handy and mobile to shift to
desired locations in case existing location had inadequate wind speed and wind source.

 

 

 

Its unique design
creates two vacuums as shown in above figure, one behind the blade and another
behind the duct, these two vacuums create a push and pull combination effect of
air behind the duct and this setup helps wind tamer to produce the twice as
much energy as compared to its counterparts, further which leads to exceeding the BELT limit efficiency (59.3%)

Which
is a very surprising factor, but this
factor is not completely proved yet as many arguments and discussion are still
active on this topic. A few claim that
efficiency of wind tamer is miscalculated

Wind tamer is proved to be efficient
even at the lower heights and slower wind speeds as seen in the above figures
(??).

 Ducted design make the complete set up free
from harm to birds unlike conventional blade wind turbines, the further ducted design makes set up noise free and vibration free.  

These turbines can be installed at
agricultural, residential and commercial places due to its noise free and no
harm to birds like features.

Wind tamer is proved to have faster
returns of investment compared to conventional turbines.

 

Recent trends in blade manufacturing:

–       
Many approaches are made and for manufacturing
the Wind turbine blade mold by additive manufacturing techniques such as 3-D printing rather than conventional
manufacturing which will increase efficiency in manufacturing operations,
faster design iteration cycles which will give freedom to innovate and design
without penalties.

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