important for engineering

1. New &Renewable
Energy
Wind Energy

2. Wind is a form of solar energy. Winds are caused by
the uneven heating of the atmosphere by the sun,
the irregularities of the earth's surface, and rotation
of the earth. Wind flow patterns are modified by
the earth's terrain, bodies of water, and vegetative
cover. This wind flow, or motion energy, when
"harvested" by modern wind turbines, can be used
to generate electricity.
In order to explain how a wind turbine works, each
component of the wind turbine have to be
explained:

3. Inside a Wind Turbine
http://www.ewea.org/wind-energy-basics/how-a-wind-turbine-works/

4. Nacelle: The nacelle is placed on the top of the tower and
contains of the gear box, low- and high-speed shafts
and the generator. Nacelle includes:
• Hub: A simple mechanism that connects the motor
with the blades using a gear to move the motor. The
hub of the rotor is attached to the low speed shaft of
the wind turbine.
• Low-speed shaft: The rotor turns the low-speed shaft,
which is a long pole, at about 20 to 30 rotations per
minute.
• Gearbox: Drives the high-speed shaft of the generator
assembly, converting low-speed rotation from the
input shaft. A planetary gear system is most common.
• Coupling: Attaches the gearbox to the generator.
Flexible couplings may be used to reduce oscillating
loads that could otherwise cause component damage.

5. • High-speed shaft: Drives the generator.
• Generator: The generator transforms the rotational energy into
electrical power.
• Transformer: The transformer converts the electrical power
from low voltage to a higher voltage suitable for grid
connection.
• Wind vane: An instrument that indicates wind direction using a
vane that rotates around a vertical axis.
• Anemometer: Instrument that measures wind speed using cups
that rotate around a mobile shaft at varying speeds.
• Mechanical brake: The mechanical brake is placed on the small
fast shaft between the gearbox and the generator. It is only used
as an emergency brake, in case the blade tip brake should fail.
The brake is also used when the wind turbine is being repaired
to eliminate any risk of the turbine suddenly starting.
• Yaw rotor: The yaw motor turns the nacelle so that the rotor
faces the wind.
• Yaw Bearing: The yaw motor has a small wheel that engages a
huge wheel. The large wheel is called the yaw bearing.

6. • Rotor: Attached to the nacelle and includes:
a) Blades, generally made of glass-reinforced fiber. For larger blades,
lighter and stronger carbon fibers are commonly used. tall-
regulated blades limit lift, or momentum, when wind speeds are
too great to avoid damaging the machine. Variable-pitch blades
rotate to minimize their surface area and thereby regulate
rotational speed. Rotor blades for large wind turbines are always
twisted.
b) Extenders, which attach the blades to the central hub. These steel
components serve as a means to support the rotor blades and
secure them to the hub
c) Pitch drive to control the angle of the blades. This system controls
the pitch of the blades to achieve the optimum angle for the wind
speed and desired rotation speed. At lower wind speeds a
perpendicular pitch increases the energy harnessed by the blades,
and at high wind speeds, a parallel pitch minimizes blade surface
area and slows the rotor. Typically one motor is used to control
each blade. Power is either electric or provided by hydraulics in
the nacelle,

7. Rotor blade materials
• Most modern rotor blades on large wind turbines
are made of glass fiber reinforced plastics, (GRP).
Using carbon fiber or aramid as reinforcing
material is another possibility, but usually such
blades are uneconomic for large turbines.
• Wood, or wood-fiber-epoxy composites have not
yet penetrated the market for rotor blades,
although there is still development going on in
this area. Steel and aluminum alloys have
problems of weight and metal fatigue
respectively. They are currently only used for very
small wind turbines.

8. Wind turbine towers
https://www.youtube.com/watch?v=KiJWvzcjHM8&feature=endscreen
https://www.youtube.com/watch?v=j7k-ayGWfh4
• The tower of the wind
turbine carries the nacelle
and the rotor.
• Towers for large wind
turbines may be either
tubular steel tower, lattice
tower or concrete tower.
Guyed tubular tower is only
used for small wind
turbines
1. Tubular steel tower:
The towers are conical (with their
diameter increasing towards the
base) in order to increase their
strength and to save materials at
the same time.

9. Cont. wind turbines tower types
2. Lattice tower:
Lattice towers are manufactured
using welded steel profiles. The
basic advantage of lattice towers
is cost, since a lattice tower
requires only half as much
material as a freely standing
tubular tower with a similar
stiffness. However, for aesthetic
reasons lattice towers have
almost disappeared in use for
large, modern wind turbines.

10. Cont. wind turbines tower types
3. Guyed pole tower:
Many small wind turbines are
built with narrow pole towers
supported by guy wires. The
advantage is weight savings,
and thus costs savings. The
disadvantage is difficult access
around the tower, which make
it less suitable in farm areas.
Finally, this type of tower is
more prone to vandalism, thus
compromising overall safety.

11. Cont. wind turbines tower types
4. Hybrid tower
solutions:
Some towers are made in
different combinations of the
techniques mentioned above.
One example is the three-
legged Bonus 95 kW tower,
which may be said to be a
hybrid between a lattice tower
and a guyed tower.

12. Advantage with concrete as material
of construction for wind energy tower
• Concrete as a material of construction can play an important role in realising
the potential of wind energy.
• The trend towards increasing generating capacity of wind mills makes
concrete a competitive material. Concrete as material of construction is
durable.
• This property of concrete plays an important role if the wind towers are
located in remote areas or in areas with aggressive environment like that of a
marine environment. The concrete tower will ensure reliability and require
less maintenance. In fact, durability of concrete against marine conditions
makes off-shore wind farms a reality. Because concrete permits a variety of
mix designs, it can be made suitable for a wide range of site conditions for
both foundation and pylon2. Through the use of admixture and special
reinforcements, not just the strength of concrete can be improved but also its
resistance to corrosion. Concrete can be tailor-made to meet specific
requirements. Depending upon the site conditions both in-situ and pre-cast
construction methods are suitable for wind tower construction.
• Reinforced concrete spread footing is commonly used because it is simple
and economic solution for the tower. This is useful for site conditions with
good soil bearing capacity.

13. Footing Design Foundation
Tower:
The spread footing design
aims at meeting stability and
strength requirement against
shear and flexural loads. Tie
down rock anchors or micro-
piles may be applied to
reduce the size of the spread
footing. The design basis
requires details of soil
bearing capacity, safety
factor to be assumed and
strength of concrete.

14. How the components work together
• The rotor blades capture wind energy and convert it to
rotational energy of shaft which transfers the rotational energy
into the gearbox in the nacelle. The gearbox increases the
speed of the shaft between the rotor hub and the generator.
The generator uses rotational energy of shaft to generate
electricity using electromagnetism.
• Electronic control unit monitors system, shuts down turbines in
case of malfunction and controls yaw mechanism. The yaw
controller moves the rotor to align with the direction of the
wind. The brakes stop the rotation of the shaft in case of power
overload or system failure.
• The tower supports the rotor and nacelle and lifts the entire
setup to higher elevation where the blades can safely clear the
ground.
• Electrical equipment carries electricity from generator down
through the tower and controls many safety elements of the
turbine.

15. Aspects when installing a wind turbine
A wind power project can basically be divided into three phases:
• Planning
• Installation
• Operation of the wind turbines
In each phase, four important points have to be kept in mind:
• Technical aspects
• Permits and legal
aspects
• Environmental aspects
• Cost aspects
http://www.ewea.org/wind-energy-basics/how-a-wind-turbine-works/
https://sites.google.com/site/e4poor/renewables/wind

16. 1. Technical aspects
The most important technical parameters
regarding the energy output from a wind
turbine are:
• Wind speed: Stronger winds produce more energy. Wind turbines generate
energy within the wind range 4 m/s – 30 m/s. If the wind reaches a speed over 30 m/s
(which rarely happens), the turbine is stopped in order to avoid potential damages.
• Blade radius: The larger the radius on the blade, the more energy can be
produced. Doubling the radius may increase the energy output by four times.
• Air density: air density is a function of altitude, temperature and
pressure. Density change by higher altitude. Heavier air exerts more lift on a
rotor. The dense heavy air near sea drives rotors relatively more effectively.

17. Other parameters that directly have an impact
on the technical aspects when planning and
installing a wind turbine.
• Wind conditions: for local wind condition
Physical obstacles, such as rows of trees, buildings, and other wind turbines,
have a direct effect on the behaviour of the wind and its wind profile.
• Placement in the terrain:
 should be place high above the ground because the wind speed is higher here.
However, it shouldn’t be placed too high, as the density will decrease.
 the wind turbine will have a greater capacity if it is placed near to the coast.
 in a wind farm, it’s necessary to find the optimal arrangement of the turbines
 Some researchers agreed that the distance between the turbines should be
at least six times the diameter of the turbine, and the angle between the
turbines should be around 25 degrees.

18. • Orography:
 It is an advantage to have a tall tower in areas with high terrain
roughness.
 The soil must be studied for each wind turbine to ensure that the
subsoil can handle the loads of the foundations. Flat gravity
foundations are used.
 Climatic conditions as seasonal heavy rains and storms must be
taken into consideration.
• Grids and space available:
 there has to be grids available and an infrastructure that enables
easy access to the wind turbine (like for example roads). The grids
can either be on-shore or off-shore, or a combination of both.
 Information also has to be gathered regarding to how far away the
next feeding point is, and what the voltage level is for a connection
to the grid.
 Very large projects often require their own transformer station so
the wind farm can feed into high-voltage grids.

19. 2. Permits and legal aspects
When planning and installing a wind turbine,
some of the legal aspects that directly affect
the consideration of starting the project are:
• Local and regional laws and regulation
• The procedure for setting up a wind turbine
To read more about policy,
http://www.ivt.ntnu.no/offshore2/?page_id=2
74

20. 3. Environmental aspects
Wind based energy, like all other energy industries, will have an impact on
the environment.
• One of the main advantages with wind energy is that it doesn’t consume
any fuel to produce electricity.
• Also, there is no emission directly related to the electricity production, as
wind turbines don’t produce carbon dioxide, sulfur dioxide, particulates or
other type of air pollution directly, as a fossil fuel power plant does.
• Another environmental advantage is that a wind turbine easy to remove or
relocated.
• Whatever impacts wind turbines may have, it is possible to minimize them
through proper design and planning. In contrast, the impacts of thermal or
nuclear energy production are long termed, slow to appear and hard to
minimize their impacts.

21. Environmental impacts concern :
• Impacts on people
• Impacts on wildlife
• Other impacts related to wind energy
• Environmental impacts from offshore wind
industry.

22. Impacts on people
• Noise: There are two different sounds emitted from wind turbines;
mechanical noise from internal equipment, such as the gearbox or yaw drive,
and aerodynamic noise caused by the blades passing through the air. The level
of noise that a wind turbine produces is not constant, but varies according to
the current output, i.e. the wind speed. Generally, the noise increases by
around one dB(A) for each meter per second of wind speed. For wind farm at
350m, the indicative noise level 35-45dB (A).
When designing a wind turbine there are several ways to minimize mechanical
noise:
• Special finish of gear teeth
• Using low-speed cooling fans
• Placing components in the nacelle rather then at ground level
• Baffle (a device that reduces the strength of airborne sound) and acoustic
isolation to the nacelle
• Vibration isolators
• Design the turbine to prevent noise from being transmitted into the overall
structure

23. Cont. Impacts on people
• Shadow flicker :Shadow flicker is defined as alternating
changes in light intensity caused by the moving blade casting
shadows on the ground and stationary objects. It occurs when the
blades of a turbine pass in front of the sun to create a recurring
shadow. It is sometimes believed that shadow flicker can cause
epileptic seizures, but this is not true(needs 5-30 flickers/s) .
• Aesthetics and visual disturbance: Wind turbines are
visible from far away and change the sight of the landscape.
Whether one gets visually disturbed by it, varies from person to
person. In many research studies it appears that the public prefer
uniform plants and fewer, but larger, wind turbines than many small
wind turbines. The placement of the turbines is important, and
should be placed in a non disturbing way and be of the same size.

24. Impacts on wildlife
Birds: Wind turbines can affect birds in many different ways.
• Collision with the blades or towers.
• The wind turbine and maintenance may affect the birds breeding by disturbing
their habitat.
• Disturbance on their migration paths.
• Reduction or loss of available habitat.
There are several ways to minimize the impact on birds:
• Avoid sensitive areas.
• A study before, during and after construction to monitor the impact on the
birds.
• Increase the visibility of the rotor blades.
• Installing the transmission cables under ground, or making over ground cables
more visible.
• Stop or reduce the rotor speed at peaks in migration or weather with limited
sight.
• Also there are studies who suggest that the white color on wind turbines
attracts insects, which again attract birds and bats. There is a suggestion to
paint all wind turbines purple, since it is less interesting for insects.

25. Cont. Impacts on wildlife
• Bats:The issue is that the bats’ lungs blow up from the rapid pressure
drop that occurs as air flows over the turbine blades. Most of the bats that
die close to a wind farm do so because of rapidly expanding air in the
lungs caused by the sudden drop in pressure.
– One way for them to avoid wind turbines could be to place microwave
transmitter on the towers, since bats tend to avoid radar transmitters.

26. Other impacts related to wind energy
• Land use in operation: A wind farm requires about 0.1 km²
land per MW, so there would be a need of an area of approximately
20 km² for a 200 MW wind farm. A wind turbine in itself doesn’t
take up much area, and it is possible to share space with other
interests, such as the farming or cattle.
• Disruption of radar and television: The society is highly
dependent on devices like power and communication networks,
electrified railways and computer networks. There is a possibility
that the reception of radio waves can be disrupted by a wind
turbine. However, it was more a problem for the first generation of
wind turbines, since they are now made of synthetic materials
which have a minimal impact on the radio waves. Another problem
is for the radar software which is built to show moving objects. A
wind project close to an airport or area of interest to the military
can cause problems.

27. Different types of wind turbines
Wind turbines can be separated into two
categories:
horizontal axis wind turbine andvertical axis
wind turbine.
Also the location of the turbine divides the type
of a wind turbine further, separating
between inshore wind turbine (wind turbine
placed on land) and offshore wind turbine(wind
turbine placed offshore).

28. Horizontal axis wind turbine (HAWT)
Horizontal axis wind turbines (HAWT) are commonly used and have a greater
efficiency than thevertical axis wind turbine (VAWT). All of the existing
horizontal axis wind turbines are shaped according to the same concept
having the nacelle on the top of the tower and pointing into the wind.
Different types of HAWT:
1. Wind mills
2. American style wind mills
3. Conventional , modern wind turbines: They usually have three blades,
because it provides the best balance of high rotation speed and load
balancing, but sometimes they only have two blades and sometimes just
even one. They have high tip speed ratios, high efficiency and low torque
ripple, which subtracts the minimum torque from the maximum during one
revolution. As the number of blades decreases, the vibration modes
increase in peak intensity, which can cause loud noise and wear and tear of
the machine.

29. • American style wind
mills
• Conventional, modern
wind turbines

30. Cont. HAWT types:
4. Unconventional, modern wind
turbines.:
• Duct rotor:
The ducted rotor is a turbine inside
a duct.
• Counter rotating wind turbine:
The two turbines can either
be on the same side of the
tower or on the opposite side

31. Advantages and Disadvantages of
HAWT:
• Advantages
1. Blades are to the side of the turbine’s center of gravity, helping stability.
2. Allowing the angle of attack to be remotely adjusted gives greater control, so
the turbine collects the maximum amount of wind energy.
3. The ability to pitch the rotor blades in a storm so that damage is minimized.
4. Tall tower allows access to stronger wind in sites with wind shear and
placement on uneven land or in offshore locations.
5. Most of them are self-starting.
6. Can be cheaper because of higher production volume.
• Disadvantages:
1. Has difficulties operating near the ground and with turbulent winds because
the yaw and blade bearing need smoother, more laminar wind flows.
2. The tall towers and long blades are difficult to transport and need a special
installation procedure.
3. When placed offshore, they can cause navigation problem.

32. vertical axis wind turbine (VAWT)
• The main difference between the vertical axis wind
turbine and the horizontal axis wind turbine is that
the rotor rotates vertically around its axis instead of
horizontally. The vertical axis wind turbine is not as
efficient as the horizontal axis wind turbine, but it
offers benefits in low wind situations where the
traditional horizontal axis wind turbine has
difficulties operating. It also tend to be safer and
easier to build, and it can be mounted close to the
ground and handle turbulence much better than
the horizontal one. As the VAWT can generally offer
30 % efficiency in the best case, it is mostly used for
private use.

33. Among the VAWT we have two main
types:
1. Darrieus (which uses lift forces generated by aerofoils: force
generated perpendicular to the direction of travel)
2. Savonius (which uses drag forces:force generated parallel and in
opposition to the direction of travel)
• Darrieus is not self-starting, so a small powered motor is required to
start the rotation. Then, when it has enough speed, the wind passing
across the airfoils starts to generate torque and the rotor is driven
around by the wind. The turbine is powered by the lift forces that are
created by a set of airfoils.
• Savonius wind turbines can and are used in electricity generation with
the benefit that they continue to generate electricity in the strongest
winds without being damaged.. They are very quiet compared to other
wind turbines and are useful for small scale domestic electricity
generation, especially in locations with strong turbulent winds.
Usually, the Savonius turbines are used whenever cost or reliability is
more important than efficiency.

35. Advantages and Disadvantages of
VAWT:
• Advantages
1. The generator, gearbox and other components may be placed on the ground,
so the tower doesn’t need to support it, and it is more accessible for
maintenance.
2. Relatively cost of production, installation and transport compared to
horizontal axis turbines.
3. The turbine doesn’t need to be pointed into the wind to be effective. This is
an advantage on sites where the wind direction is highly variable.
4. Hilltops, ridgelines and passes can have higher and more powerful winds
near the ground than higher up because due to the speed up effect of winds
moving up a slope. In these places, vertical axis turbines are suitable.
5. The blades spin at slower speeds than the horizontal turbines, decreasing the
risk of injuring birds.
6. It is significantly quieter than the horizontal axis wind turbine. As a result,
vertical axis wind turbines work well on rooftops, making them particularly
useful in residential and urban environments. They may also be built in
locations where taller structures are prohibited by law.
7. They are particularly suitable for areas with extreme weather conditions, like
in the mountains where they can supply electricity to mountain huts.

36. Cont. Advantages and Disadvantages
of VAWT:
• Disadvantages:
1. They are less efficient than horizontal axis wind
turbines. Most of them are only half as efficient as
the horizontal ones because of the additional drag
that they have as their blades rotate into the wind.
2. Air flow near the ground and other objects can
create turbulent flow, which can introduce issues of
vibration. This can include noise and bearing wear
which may increase the maintenance or shorten
the service life.
3. The machine may need guy wires to hold it up. Guy
wires are impractical in heavily farmed areas.

37. 4. Cost aspects
Even though it has its free energy source (wind), the wind power is characterized by high
investing costs and low operating cost.
Approximately 75 % of the total cost of energy for a wind turbine is related to upfront
costs such as the cost of the turbine, foundation, electrical equipment and grid-
connection. The highest amount of investing costs regarding the installation of a
wind turbine lies in the turbine, but the grid and infrastructure system does also play
a big role, which varies depending on the geographical conditions. For instance,
installing an off-shore wind turbine is a lot more costly than installing an on-shore
wind turbine. One of the biggest factors is the often non-existing grid system that has
to be built from the wind turbine to the on-shore grid system.
The price of a tower for a wind turbine is generally around 20 per cent of the total price
of the turbine. It is therefore quite important for the final cost to build towers as
optimally as possible. The material being used is also important. Lattice towers are
the cheapest to manufacture, since they typically require about half the amount of
steel used for a tubular steel tower.
Until now, and like all other new renewable energy sources, the long-run marginal cost
of wind power exceeds the market price. Normally there will only be made an
investment if the long-run marginal cost equates the market price. In other words,
we cannot expect a boom in new investments in wind energy as long as this is the
fact. However, in many countries, subsidies and support from the government have
made it easier to raise the project of planning and installing a wind turbine.

38. Wind energy is the kinetic energy of air in motion(wind). Total wind energy flowing
through an imaginary area A during the time t is:
where ρ is the air density;
v is the wind speed;
Avt is the volume of air passing through area A (which is considered perpendicular to
the direction of the wind); mass m= Avt (volume) * ρ(density)
Avtρ is therefore the mass m passing per unit time.
Note that ½ ρv2 is the kinetic energy of the moving air per unit volume.
Power is energy per unit time, so the wind power incident on A (e.g. equal to the rotor
area of a wind turbine) is:
When area of rotor is equal to : Π r2
Wind power in an open air stream is thus proportional to the third power of the wind
speed; the available power increases eightfold when the wind speed doubles. Wind
turbines for grid electricity therefore need to be especially efficient at greater wind
speeds.
http://www.ewea.org/wind-energy-basics/how-a-wind-turbine-works/

39. Power Calculation
• Wind kinetic energy:
• Wind power:
• Electrical power:
– Cb  .35 (<.593 “Betz limit”)
• Max value of
– Ng  .75 generator efficiency
– Nt  .95 transmission efficiency
2
2
1
vmE airk 
32
2
1
vrP airwind 
windtgbgenerated PNNCP 
      323
1
2
4
1
1
2
1
2
1
2
1 v
v
v
v
v
v
airdt
dE
vrP  

40. If you have a small wind turbine with a blade diameter of 1 m
and an operating efficiency of 20% at a wind speed of 6 m/sec
(about 13.4 mph). Then, to calculate how much power the turbine
can generate at this wind speed:
Rotor swept area: Area = Π × (Diameter/2)2 = 3.14 × (1/2)2 =
0.785 m2
Available power in the wind: Pwind= Air Density × Area × v3/2 =
1.2 × 0.785 × 63/2 = 101.7 watt
Then the power that can be extracted from the wind assuming
20% turbine efficiency is:
Pturbine=0.20 × 101.7 = 20.3 watts
If this ran continuously for a year (about 8,750 hours) then it
would produce: 20.3 watts × 8750 hours = 177625 watt-hours, or
about 177 kWh in a year.
(Note: we used the density of air at sea level, which is about
1.2 kg/m3)