Windmills have been assisting mankind to convert the energy contained in wind to
many other useful forms for the last two thousand years.
Today's wind turbines are capable of converting a great amount of energy in
the wind into electricity.
This is due to the blades which are developed using state-of-the-art
aerodynamic analysis and the other performance-enhancing equipment.
In this video we will explore these different set of technology in a simple
yet scientific way.
First, let's get into its basic working
If the blowing wind can turn the wing, we will receive electricity from the
generator that is attached to it.
However, how does the blowing wind turn the wing ?
Let's have a close look at the blade.
The Blade has a lot of airfoil cross-sections consisting of different
sizes and shapes from the root to tip.
The simple airfoil technology makes the wind turbine blade turn.
That means that a lift force is produced when a fluid moves
over an airfoil.
This way the wind turbine achieves the basic rotation
we are accustomed to seeing.
Just as in a moving train
you experience things relatively, the moving wind turbine blade also
experiences the wind relatively.
For the moving blade the relative wind velocity is
as shown.
Therefore the wind turbine blade is positioned in a tilted manner
in order to align with the relative wind speed.
As the blade velocity increases to the tip the relative wind speed becomes more
inclined towards the tip.
This means that a continuous twist is given to the blade from the root to tip.
However this rotation cannot be directly coupled to a generator.
Because the wind turbine blades typically turn at a very low rate of rpm
due to the issues of the noise and mechanical strength.
Considering this low-speed rotation we cannot produce
any meaningful electricity frequency from a generator.
So before connecting to the generator the speed is increased in a gearbox.
The gearbox uses a planetary gear set arrangement
to achieve the high speed ratio.
A break also sits in the nacelle.
The function of the brake is to arrest wind blade rotation
during excessively windy conditions
Consequently the electricity that is
passed through the cables towards the base
where a step-up transformer is situated.
The wind turbine should face the wind
normally for maximum power extraction.
But the wind direction can change at any time.
A velocity sensor
on the top of the nacelle measures the wind speed and direction.
The deviation in the wind's direction
is sent to an electronic controller which in turn sends an appropriate signal to the
yawing mechanism to correct the error.
You can see how the yaw motors turn the nacelle.
Thus the wind turbine will
always be aligned with the wind direction:
According to the wind speed the relative velocity anggle
of the wind also changes.
A blade tilting mechanism tilts the blades
and guarantees a proper alignment of the blade with the relative velocity.
Thus the blades are always at the optimum angle of attack
with the relative wind flow.
Efficiency of the wind turbine is the really interesting topic.
To gain a good insight into wind turbine efficiency assume that you are measuring
wind speed at upstream and downstream over wind turbine.
You can note that the wind speed
at the downstream is much smaller than the upstream.
This is because the blades absorb
some kinetic energy from the wind.
The same amount of energy
is converted as mechanical power of the wind turbine.
It is interesting to note that
a wind turbine absorbs 100 percent of the available kinetic energy
only if the downstream wind speech becomes zero.
However zero wind speed at downstream is a physically impossible condition.
This cartoon animation clearly depicts this fact.
Zero downstream speed simply means
the whole flow is stock.
This physical reality of the flow demands a certain amount of exit wind speed.
That means that there is a theoretically maximum efficiency
a wind turbine can achieve.
This limit is known as Betz's limit.
Essentially it means that no wind turbine in the world can
ever cross the efficiency limit of 59.3 percent.
We hope you have now developed a good inside of the operation a wind turbines.
Thank You !