Construction and Working of Wind turbines.

2. WIND ENERGY(C0NTENTS)
• INTRODUCTION
• ORIGIN OF WINDS
• WIND DATA
• VARIATION OF WIND SPEED WITH HEIGHT
• HORIZONTAL AXIS WIND TURBINE (HAWT)
ROTORS
PITCH SYSTEM CONTROL
NACELLE (IT’S COMPONENTS)
YAW SYSTEM CONTROL
TOWER (ACCESS LADDER)
FOUNDATION (ELECTRIC GRID)
• EFFICIENCY OF TURBINE
• BETZ’S LAW
• TIP SPEED RATIO
• VERTICAL AXIS WIND TURBINE (VAWT)

3. INTRODUCTION
• Winds are horizontal movement of AIR from an area of HIGH
pressure(H) to an area of low pressure(L).
• Wind energy is a kinetic energy associated with movement of large
masses of air.
• It is clean, cheap, and eco-friendly renewable source.
• Wind energy is utilized as mechanical energy with the help of a wind
turbine.
• Moderate to high-speed winds, typically from 5m/s to about 25m/s
are considered favorable for most wind turbines.
• The electric power generation through wind was first proposed in
Denmark in 1890

4. ORIGIN OF WINDS
• The origin of winds may be
traced basically to uneven
heating of the earth’s
surface due to sun.
• This may lead to circulation
of widespread winds on a
global basis, producing
planetary winds or may have
a limited influence in a
smaller area to cause local
winds.

5. GLOBAL (OR
PLANETARY)
WINDS
• Two major forces determine
the speed and direction of
wind on a global basis :
i. Primary force : Due to
differential heating of the
earth at equatorial and
polar regions. (Heat
transfer)
ii. Spinning of earth about its
axis produces a Coriolis
force, which is responsible
for deviation of air
currents. (deflects the
direction of wind)

6. LOCAL WINDS (THAT
BLOW OVER SHORT
DISTANCES)
• Localized uneven heating is
responsible for local winds. Local
winds are produced due to two
mechanisms:
i. Due to differential heating of
land surface and water bodies
due to solar radiation.
ii. Due to differential heating of
slopes on the hillsides and that
of low lands.

7. FACTORS AFFECTING THE DISTRIBUTION OF
WIND ENERGY ON THE SURFACE OF THE
EARTH
• Both global and local factors influence the availability of wind energy at
particular site.
i. On the planetary level, great mountain masses influence the circulation of
air currents.
ii. Surface roughness or friction, due to the resistance that different
elements of the earth surface like hill’s, tall buildings, trees and similar
obstructions impair streamline air flow. Wind velocity in horizontal
direction gets markedly reduced. Frictional effect is less on smooth areas
such as sea shore or large open areas and more in rough urban areas with
tall building and trees.
iii. Wind speed also increases while passing through narrow mountain gaps
where it gets channeled.

8. • Wind speed is measured by an anemometer and wind
direction is measured by a wind vane attached to the
direction indicator.
• A cup anemometer consists of three or four cups
mounted symmetrically about a vertical axis. The
speed of rotation indicates wind speed.
• Wind speed measurement should be made at an
effective height 10m above the ground. (WMO)
• Wind rose Graph : An elegant method of describing
average wind speed duration and direction on a
single graph. Length of the bars represent the
percentage of duration.Wind rose
graph

9. VARIATION OF WIND
SPEED WITH HEIGHT
• Wind shear : Rate of change of
wind speed with height
• At the earth’s surface, wind
speed is always zero. It
increases with height above the
ground. The wind near the
earth’s surface is retarded by
surface roughness.

10. ADVANTAGES OF WIND ENERGY
i. It is a renewable source of energy.
ii. Like all forms of solar energy, wind power systems are non-
polluting, so it has no adverse influence on the environment.
iii. Wind energy systems avoid fuel combustion and transport.
iv. Cost free renewable resources.

11. DISADVANTAGES OF WIND ENERGY
• Wind energy available is fluctuating
in nature and it varies from zero to
storm force.(unreliable)
• Wind energy systems are noisy in
operation; a large unit can be heard
many kilometers away.
• Birds and bats have been killed by
flying into the rotors.
• Good wind sites are often located in
remote locations, far from cities
where the electricity is needed.
• Installation & Maintenance cost of
wind turbine is high.

12. TYPES OF WIND TURBINES

13. HORIZONTAL AXIS WIND
TURBINE (HAWT COMPONENTS)
ROTOR
 BLADES
 HUB (BLADE PITCH CONTROL )
NACELLE
 LOW SPEED SHAFT
 GEAR BOX
 BRAKE
 HIGH SPEED SHAFT
 GENERATOR
 CONTROLLER
 ANEMOMETER & WIND VANE
YAW SYSTEM (WIND ORIENTATION CONTROL)
TOWER (ACCESS LADDER )
FOUNDATION (CONNECTION TO THE ELECTRIC GRID)

14. ROTOR (BLADES & HUB ) BLADE
• Turbine blades are made of high-
density wood or glass fiber and
epoxy composites.
• The blades of the wind turbine are
designed to be aerodynamic so
that they are able to utilize wind
energy more easily.
• They have an airfoil type of cross
section.
• The blades are slightly twisted
from the outer tip to the root.
• The diameter of a typical, MW
range, modern rotor may be of
the order of 100m.

15. TYPES OF ROTORS
• Wind turbines have been built
with up to six propellers type
blades but two and three-
bladed propellers are most
common.
• A single blade rotor, with a
balancing counterweight is
economical, has simple controls
but it is noisier and produces
unbalanced forces. it is used for
low power applications.

16. TWO AND THREE-
BLADED ROTOR
• The two-blade rotor is also simpler to
erect, since it can be assembled on
the ground and lifted to the shaft
without complicated operation during
the lift.
• Compared to the two-blade design,
the three-blade machine has
smoother power output and balanced
spinning force.
• Adding a third blade increases the
power output by about 5% only, while
the weight and cost of a rotor
increases by 50%.
• Large HAWTs have been
manufactured with two and three

17. SAIL TYPE, DUTCH
TYPE, MULTI BLADE
ROTOR
• Sail wing type : it is of recent origin. The blade
surface is made from cloth, nylon, or plastics
arranged as mast and pole or sail wings.
• Dutch type : it is one of the oldest designs.
The blade surface are made from an array of
wooden slats (sticks).
• Multi blade type : made from sheet metal or
aluminum. They have good power coefficient,
high starting torque and add advantage of
simplicity and low cost.
• Both Dutch and Multi blade type are low-
speed rotors and most suited for water-lifting
applications, which require a high starting
torque. They can capture power even very
slow winds.
SailWingTy
pe
Dutch type
Multi Bladed
type

19. HUB
• The central solid portion of
the rotor wheel is known as
hub. All blades are attached
to the hub. The mechanism
for pitch angle control is
also provided inside the
hub.
• Pitch angle control system is
used to maximize the wind
turbine efficiency by
positioning the blades at the
best possible angle.
• The pitch motor is often
found near the hub of the
rotor.

20. NACELLE
• The term nacelle is derived from
the name for housing (casing)
containing the engines of an
wind turbine (Aerogenerator).
• The rotor is attached to the
nacelle, and mounted at top of a
tower. It contains rotor brakes,
gearbox, generator, low and
high speed shafts, electrical
switchgear and control.

21. • LOW SPEED SHAFT :
The low speed shaft is
turned by the motion of a wind
turbines blades as they rotate. The low
speed shaft transfers kinetic energy to
the gearbox.
• GEARBOX :
The gearbox steps up
the shaft rpm to suit the generator. It
is a heavy and expensive piece of
equipment that connects the low
speed shaft to the high speed shaft.
• HIGH SPEED SHAFT :
The high speed shaft
connects the gearbox to the generator
and its sole purpose is to drive the
generator so that it can produce
electricity.

22. BRAKE :
• Brakes are used to stop the
rotor when power generation is
not desired. Turbine do not
operate at wind speed above
about 25m/s because they
might be damaged by high
winds.
• Generally drum brake or disk
brake is used to stop turbine in
emergency situation and at
maintenance situations.

23. GENERATOR
• Wind power generator converts
wind energy (Mechanical energy) to
electrical energy.
• The generator is attached at one
end to the wind turbine, which
provides the mechanical energy
and at other end is connected to
the electrical grid.
• The generator need to have a
cooling system to make sure there
is no over heating.

24. YAW-CONTROL MECHANISM
• The mechanism to adjust the
nacelle around the vertical
axis to keep it facing the wind
is provided at the base of the
nacelle. The yaw-control
system continuously orients
the rotor in the direction of
wind.
• The yaw motor will be found
inside the tower underneath
the nacelle and will turn the
nacelle and the rotor to face
the current wind direction. (* Yaw means twist about vertical axis )

25. CONTROL SYSTEM (CONTROLLER)
• The control system continuously
adjusts the pitch to obtain
optimal performance.
• The controller starts up the
machine at wind speed of about 5
m/s and shuts off the machine at
about 25 m/s.
• The control system is also the
mechanism that will calculate the
most efficient pitch and yaw for
the turbine dependent on wind
speed and direction.
• Control system gets wind data
(speed & direction ) from velocity

26. TOWER
• The tower supports the nacelle and
rotor. Its height approximately two to
three times the blade length. But,
practically maximum height is
estimated to be roughly 60 m.
• It is designed to withstand the wind
load during gusts (strong rush of
wind).
• At the bottom level of the tower there
will be step-up transformers for the
connection to the Electrical Grid.
• Inside of the tower there is a ladder to
access to top of the tower for
maintenance and setup processes and
will also contain high voltage cables
for transporting the electricity
produced by the generator at the top
of the turbine to its base.

27. TYPES OF TOWERS
1. The reinforced concrete
tower,
2. The pole tower,
3. The built up shell-tube
tower, and
4. The truss tower.
Pole tower Truss tower

28. FOUNDATION
• Wind turbines, by their
nature, are very tall
slender structures.
• It must be designed
mainly to transfer the
vertical load (dead
weight) & horizontal
dynamic load (wind
load) to the ground.
• The turbines are
sufficiently restrained
against moment loads
to operate efficiently.

29. WIND TURBINE EFFICIENCY
• 𝜂 𝑜 =
𝑢𝑠𝑒𝑓𝑢𝑙 𝑜𝑢𝑡𝑝𝑢𝑡 𝑝𝑜𝑤𝑒𝑟
𝑤𝑖𝑛𝑑 𝑝𝑜𝑤𝑒𝑟 𝑖𝑛𝑝𝑢𝑡
𝜂 𝐴 × 𝜂 𝐺 × 𝜂 𝐶 × 𝜂𝐺𝑒𝑛
Where ;
𝜂 𝐴 = 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑎𝑒𝑟𝑜𝑡𝑢𝑟𝑏𝑖𝑛e
𝜂 𝐺 = 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑔𝑒𝑎𝑟𝑖𝑛𝑔
𝜂 𝐶 = 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑚𝑒𝑐ℎ𝑎𝑛𝑖𝑐𝑎𝑙𝑐𝑜𝑢𝑝𝑙𝑖𝑛𝑔
𝜂𝐺𝑒𝑛 = 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑜𝑓 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑜𝑟

30. BETZ’S LAW
• This law states that no wind turbine can
capture more than
16
27
or 59.3% of kinetic
energy of the wind.
• It gives the value of Theoretical maximum
efficiency that a wind turbine can achieve.

31. TIP SPEED RATIO (TSR)
• TSR is the ratio between the tangential speed of the
tips of the turbine blades and the speed of the wind.
(Tip Speed Ratio) 𝜆 =
𝑇𝑖𝑝 𝑠𝑝𝑒𝑒𝑑 𝑜𝑓 𝑏𝑙𝑎𝑑𝑒
𝑤𝑖𝑛𝑑 𝑠𝑝𝑒𝑒𝑑
• The tip-speed ratio is related to efficiency, with the
optimum varying with blade design. Higher tip speeds
result in higher noise levels and require stronger blades
due to large centrifugal forces.

33. VERTICAL AXIS WIND TURBINE
(VAWT) :
The main attractions of a VAWT are :
• It can accept wind from any direction,
eliminating the need of yaw control,
• The gearbox, generator, etc., are located at
the ground , thus eliminating the heavy
nacelle at the top of the tower, thus
simplifying the design and installation of
the whole structure, including the tower,
• The inspection and maintenance also gets
easier, and
• It also reduces the overall cost

34. TOWER (OR ROTOR SHAFT)
• The tower is a hollow vertical rotor shaft, which
rotates freely about the vertical axis between
the top and bottom bearings.
• It is installed above a super structure.
• The upper part of the tower is supported by guy
ropes.
• The height of the tower of a large turbine is
around 100m.

35. BLADES
• It has two or three thin, curved blades shaped like an egg
beater in a profile, (Troposkien profile) with blades curved in a
form that minimizes the bending stress caused by centrifugal
forces.
• The blades have an airfoil cross section with constant chord
length.
• The pitch of the blades cannot be changed.
• The diameter of the rotor is slightly less than the tower height.

36. SUPPORT STRUCTURE
• The support structure is provided at
the ground to support the weight of
the rotor.
• Gearbox, generator, brakes, electrical
switchgear and controls are housed
within this structure.

37. TYPES OF ROTORS
1. Cup type rotor
2. Savonius or S-rotor
3. Darrieus rotor
4. Musgrove rotor
5. Evans rotor

38. CUP TYPE ROTOR
• The simplest being a three-or four-cup structure attached
symmetrically to a vertical shaft.
• The drag force on the concave surface of the cup facing the wind is
more than that on the convex surface. As a result, structure starts
rotating. Some lift force also helps rotation.
• However, it cannot carry a load and therefore cannot used as power
source.
• The main characteristic of this rotor is that its rotational frequency is
linearly related to wind speed. i.e., it is used for measuring the wind
speed and the apparatus is known as CUP ANEMOMETER.

39. SAVONIUS OR S-ROTOR
• It consists of two half cylinders attached to a
vertical axis and facing in opposite directions to
form a two-vane rotor.
• It has high starting torque, low speed and low
efficiency.
• It can extract power even from very slow wind,
making it working most of the time. These are
used for low-power applications.
• A high starting torque particularly makes it
suitable for pumping applications.

40. DARRIEUS ROTOR (HIGH SPEED, HIGH EFFICIENCY)
• It is used for large-scale power generation. Its power
coefficient is considerably better than that of an S-
rotor.
• Drawback : it is usually not self-starting. Movement
may be initiated by using electrical generator as
motor (or S-rotor).
• As the pitch of the blade cannot change, the rotor
frequency and, thus the output power cannot be
controlled. Hence, at high wind speed it becomes
difficult to control the output.
• For better performance and safety of the blades,
gearbox and generator, it is desirable to limit the
output to a level much below its maximum possible
value.

41. MUSGROVE ROTOR
• He suggested the use of H-shaped rotor
where blades with a fixed pitch are attached
vertically to a horizontal cross arm.
• Power control is achieved by controlled
folding of the blades.
• Inclining the blades to the vertical provides
an effective means of altering the blade
angle of attack and hence controlling the
power output.

42. EVANS ROTOR (GYRO MILL)
• It is an improvement over H-shaped rotor.
• Here, the rotor geometry remains fixed
(blades remains straight) , but the blades are
hinged on a vertical axis and the blade pitch
is varied cyclically (as the blade rotates
about the vertical axis) to regulate the power
output.
• But the need to vary the pitch cyclically
through every rotor revolution introduces
considerable mechanical complexity.

43. ANIMATIONS OF HAWT (PITCH & YAW
MECHANISM)