• Present WTG technology suffers from
several limitations in terms of efficiency,
noise generation, and danger to flying
• The purpose of this paper is to provide an
in-depth review of current WTG
technology and to suggest solutions for
• Indian Ministry of Non-
conventional Energy Sources
(MNES) has set a target of
achieving 10% additional grid
energy from renewable sources.
• India has a potential of 49,000
MW of wind power. But only
18,192 MW of energy is being
• For increased production more
installations as well as new
technologies needed to be
• More WTGs need to be installed
nearer to the west coast of India
in view of wind energy potential.
Design Considerations of WTGs (1/3)
• A Wind turbine generator is
a device that converts
kinetic energy of wind to
• The figure shows a
schematic of the current
WTGs with necessary gear
and yawing mechanism.
• There can be a number of
designs based on the
number of blades, type of
axis and power generation
Design considerations of WTGs(2/3)
Where R→ radius of circle swept by tip of rotor blade
u →velocity of wind
The mechanical power and torque produced from wind turbines is
according to the following equations:
variation of and as a function of
Variation of CP and CT as a function of for different types of WTG (Source: Fateev, 1948)
• When wind speed changes , rotational
speed has to achieve best value of
• This means that wind speed U and
must be combined into a single variable.
• This single variable is the ratio of turbine
tip speed R to the wind speed u.
In this way power coefficient and torque
coefficient are inter related.
Design considerations of WTGs(3/3)
Studies on wind turbines
• Albert Betz was a
German physicist. In 1919
he was awarded his PhD
from university of
Gottingen . He published
a law called Betz law in
• Betz law: According to
this law, no wind turbine
can capture more than
59.3% of kinetic energy
Measures to improve performance of WTGs
The factors to be considered to increase
efficiency of WTGs are as follows:
• Blade length Blade number
• Aerodynamic design Rotational speed
• Blade shape Pitch control
• Blade thickness Altitude
• Blade twist Temperature
Recent trends in wind design(1/4)
• Ali M Eltamaly(2009) proposed that by using
gearless WTGs the noise problem caused by high
rotational speed can be reduced and overall
efficiency and reliability can be enhanced .
Because of these gearless WTGs weight
will be reduced and maintenance need can be
eliminated . These WTGs can exploit maximum
power at different wind speeds . In the variable
speed operation ,reduction in mechanical stresses
and increased energy capture will take place.
Recent trends in wind design(2/4)
• Richard(2009) studied the optimization of wind
turbine rotor operating in uniform wind of 10m/s
with respect to power coefficient and noise level
via a genetic algorithm.
He has considered into account the air foil
shape , chord distribution , RPM and pitch for a
74.6 m rotor while judging its performance . In
his observation optimized rotor yields a 7.6%
increase in annual power production.
Recent trends in wind design(3/4)
• Francois Gangnon proposed the concept of concentrating the
wind by funneling through a conduit so that flux of
compressed air is thereby directed to interact with the most
efficient surface of a wind turbine propeller blade.
Such WTG will have advantage with both weakest and
strongest winds . since the WTG is housed within the
apparatus, the resulting noise caused by aerodynamic motions
can be almost reduced.
In addition to this an enclosed WTG protect flying
wildlife from entering into contact with WTG.
Recent trends in wind design(4/4)
• The gear box in large WTGs can be replaced by low
speed permanent magnet synchronous
generator(PMSG),the rotor rotates at the same speed
as rotor of the turbine.
This can be directly connected to the wind
turbine which results in a sample mechanical system.
This results in decrease in the weight of WTG.
• India has a potential of 49,000 MW of wind power. But only 37%
(18,192 MW) of which is currently being harnessed.
• Many wind turbine configurations are possible, but the 3-bladed
HAWTGs are proved to be more efficient than the other
• Care must be taken in choosing a wind turbine generator with
appropriate blade length, shape, thickness, twist, rotational speed,
and pitch control for maximum efficiencies. In addition,
geographical altitude and air temperature of the installation site are
• The current wind turbine generators suffer from few limitations like
lower efficiency at the low and high wind speeds, unacceptable
noise level, posing danger to flying wildlife, etc. These limitations
can be overcome by adopting new design strategies in WTGs. One
such a strategy is to conceal turbine blades as proposed by Francois