Wind Power - Full Report

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Wind energy
Suez Canal University
Faculty of Engineering
Electrical Engineering Department
Energy Conversion
Wind Power
Dr. Mohamed Nabil
ENG. Hany Salem
Prepared by:
Group 4
Ahmed Nabil Aly
Bassam Abdellah Abd-elgalel
Waleed Hassn Hassan
Abd-elrahman Fathy
El-hussien Reda
Hussien Kishk

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Wind energy
Tableof contents
Introduction............................................................................................................8
History of Wind Energy............................................................................................8
1.1 A Brief History of Windmills.............................................................................8
1.2 Early Wind Generation of Electricity ..............................................................12
1.3 The Re-Emergence of Wind Energy................................................................15
Modern Wind Energy.............................................................................................18
2.1 Modern Wind Turbines .................................................................................18
2.1.1 Modern wind turbine design....................................................................20
2.1.1.1 Rotor.................................................................................................21
2.1.1.2 Drive Train.........................................................................................22
2.1.1.3 Generator..........................................................................................22
2.1.1.4 Gearbox ............................................................................................23
Why Use a Gearbox?..................................................................................24
2.1.1.5 Nacelle and Yaw System ....................................................................25
2.1.1.6 Tower and Foundation (base).............................................................25
2.1.1.7 Controls ............................................................................................26
The Electronic Wind Turbine Controller ......................................................27
Communicating with the Outside World.....................................................27
Internal Communications...........................................................................27
Fail Safe Mechanisms and Redundancy.......................................................28
What is monitored?...................................................................................28
Control Strategies......................................................................................28
2.1.1.8 Balance of Electrical System...............................................................29
2.1.2 Power Output Prediction.........................................................................29
2.1.3 Other Wind Turbine Concepts..................................................................30

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2.2 Future of Wind Turbine.................................................................................33
The power in the wind...........................................................................................34
3.1 Principles of wind energy conversion.............................................................35
3.2 Types and characteristics of rotors ................................................................36
How Does a Wind Turbine Generate Electricity? .....................................................38
4.1 Converting Wind to Mechanical Energy .........................................................38
4.2 Creating Electricity from Wind.......................................................................39
4.3 Distribution of Electricity...............................................................................39
Wind Energy in Egypt.............................................................................................40
5.1 Background...................................................................................................40
5.2 Wind Energy Resource..................................................................................40
5.3 Production capacities ....................................................................................41
5.4 Comparison between wind power in Egypt and the world..............................42
5.5 wind farms in Egypt.......................................................................................42
Wind energy in the world.......................................................................................43
6.1Wind farm .....................................................................................................43
6.1.1 Offshore wind power...............................................................................44
6.1.2 Onshore wind power...............................................................................45
6.2 Wind power capacity and production ............................................................47
Advantages and disadvantages of wind energy.......................................................50
7.1 Advantages of Wind Energy...........................................................................50
7.1.1 Renewable Energy...................................................................................50
7.1.2 Reduces Fossil Fuels Consumption...........................................................50
7.1.3 Less Air and Water Pollution....................................................................50
7.1.4 Initial Cost...............................................................................................51
7.1.5 Create Many Jobs...................................................................................51
7.2 Disadvantages of Wind Energy.......................................................................51
7.2.1 Noise Disturbances..................................................................................52

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7.2.2 Threat to Wildlife ....................................................................................52
7.2.3 Wind Can Never Be Predicted ..................................................................52
7.2.4 Suited To Particular Region......................................................................52
7.2.5 VisualImpact...........................................................................................52
Future of wind power technology...........................................................................53
8.1 Airborne Wind Turbines ................................................................................53
8.1.1 Makani Airborne Wind Turbine................................................................53
8.1.2 Altaeros Airborne Wind Turbine...............................................................54
8.2 Power from Low Speed Winds.......................................................................55
Wind Harvester................................................................................................55
8.3 Bladeless Wind Power...................................................................................55
8.4 Wind Turbine Lenses.....................................................................................56
8.5 Vertical Axis Turbines....................................................................................57
8.6 Quiet Wind Turbines .....................................................................................58
8.7 Wind Power Storage .....................................................................................59
References ............................................................................................................61

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Table of figures
Figure 1.1 Hero.s windmill (from Woodcroft, 1851) ..................................................8
Figure1.2 Seistan windmill (Vowles, 1932)................................................................9
Figure 1.3 Post mill ................................................................................................10
Figure 1.4 European smock mill (Hills, 1994)...........................................................11
Figure 1.5 Smeaton laboratory windmill testing apparatus......................................12
Figure 1.6 American water-pumping windmill design..............................................12
Figure 1.7 Jacobs turbine (Jacobs, 1961).................................................................13
Figure 1.8 Danish Gedser wind turbine...................................................................14
Figure 1.9 Smith–Putnamwind turbine (Eldridge, 1980)..........................................15
Figure 1.10 California wind farm.............................................................................16
Figure2.1-Modern utility-scale wind turbine...........................................................19
Figure 2.2 HAWT rotor configurations ....................................................................20
Figure2.3 Fiberglass-reinforced epoxy blades of Siemens SWT, blades, lift type
blades, drag type blades ........................................................................................21
Figure 2.4 gearbox, generator................................................................................23
Figure 2.5 Gearbox, rotor shaft and brake assembly................................................24
Figure 2.6 Nacelle and Yaw System.........................................................................25
Figure 2.7Tower and foundation ............................................................................26
Figure 2.7 Grid Side Controller ...............................................................................28
Figure 2.8 Typical wind turbine power curve...........................................................29
Figure 2.9 Sandia 17-meter Darrieus VAWT............................................................30
Figure 2.10 Floating wind turbine concept..............................................................31
Figure 2.11 Various concepts for horizontal axis turbines........................................32
Figure 4.1 Wind Turbine Generate Electricity ..........................................................38
Figure 4.2 blades rotate the rotor and convert wind energy to mechanical energy...39
Figure 4.3 Distribution of Electricity........................................................................39
Figure 5.1 Overview map for the Gulf of Suez in Egypt............................................40
Figure 5.2 Zafarana wind farm................................................................................42
Figure 6.1 Wind speed over the world....................................................................43
Figure 6.2 The Gansu Wind Farm in China...............................................................44
Table 5 World's largest onshore wind farms ...........................................................46
Figure 6.3 Global wind power cumulative............................................................48
Figure 6.4 Top windpower electricity producing countries in 2012 ..........................49
Figure 8.1 airborne wind turbine............................................................................53

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Figure 8.2 Altaeros Airborne Wind Turbine.............................................................54
Figure 8.3 Wind Harvester......................................................................................55
Figure 8.4 winds talk..............................................................................................55
Figure 8.5 Wind Turbine Lenses..............................................................................56
Figure 8.6 Windspire..............................................................................................57
Figure 8.7 Eddy Turbine.........................................................................................58
Figure 8.8 Eco Whisper Turbine..............................................................................58
Figure 8.9 ManmadeIsland Wind Battery Concept..................................................59
Table of tables
Table1 Particulars and component masses of the...................................................33
Table 2 Comparison of Rotor Types........................................................................37
Table3 Comparison between wind power in Egypt and the world ...........................42
Table 4 the world's 10 largest offshore wind farms ................................................44
Table 5 World's largest onshore wind farms ...........................................................46
Table6 Top windpower electricity producing countries in 2012...............................48

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Introduction
History of Wind Energy
It is worthwhile to consider some of the history of wind energy. The history serves to
illustrate the issues that wind energy systems still face today, and provides insight into why
turbines look the way they do. In the following summary, emphasis is given to those
concepts which have particular relevance today.
1.1 A Brief History of Windmills
The first known historical reference to a windmill is from Hero of Alexandria, in his work
Pneumatics (Woodcroft, 1851). Hero was believed to have lived either in the 1st century
B.C. or The 1st century A.D. His Pneumatics describes a device which provides air to an
organ by Means of a windmill. An illustration which accompanies Hero’s description is
shown in Figure 1.1. There has been some debate about whether such a windmill actually
existed and whether the Illustration actually accompanied the original documents. See
Shepherd (1990) and Drachman (1961). One of the primary scholars on the subject,
however, H. P.Vowles, (Vowels, 1932) does Consider Hero.s description to be plausible.
One of the arguments against the early Greeks Having been familiar with windmills has to
do with their presumed lack of technological Sophistication. However, both mechanically
driven grinding stones and gearing, which would generally be used with a wind-driven rotor,
were known to exist at the time of Hero. For Example, Reynolds (1983) describes water-
powered grinding wheels at that time. In addition, the analysis of the Antikythera
mechanism (Marchant, 2006) confirms that the early Greeks had a high degree of
sophistication in the fabrication and use of gears.
Apart from Hero.s windmill, the next reference on the subject dates from the 9th century
A.D. (Al Masudi as reported by Vowles, 1932) Windmills were definitely in use in the
Persian region of Seistan (now eastern Iran) at that time. Al Masudi also related a story
indicating that windmills were in use by 644 A.D. The Seistan windmills have continued to
be used up to the present time. These windmills had vertical axis rotors, as illustrated in
Figure 1.2.
Figure 1.1 Hero.s windmill (from Woodcroft, 1851)
Figure1.1 Hero.s windmill (from Woodcroft, 1851)

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Wind energy
Windmills made their first recorded appearance in northern Europe (England) in the 12th
Century but probably arrived in the 10th or 11th century (Vowles, 1930). Those windmills
were considerably different in appearance to those of Seistan, and there has been
considerable speculation as to if and how the Seistan mills might have influenced those that
appeared later in Europe. There are no definite answers here, but Vowles 1930 has
suggested that the Vikings, who traveled regularly from northern Europe to the Middle East,
may have brought back the concept on one of their return trips.
Figure1.2 Seistan windmill (Vowles, 1932)
Figure1.2 Seistan windmill (Vowles, 1932)
An interesting footnote to this early evolution concerns the change in the design of the
rotor from the Seistan windmills to those of northern Europe. The Seistan rotors had vertical
axes and were driven by drag forces. As such they were inherently inefficient and
particularly susceptible to damage in high winds. The northern European designs had
horizontal axes and were driven by lift forces. How this transition came about is not well
understood, but it was to be of great significance. It can be surmised, however, that the
evolution of windmill rotor design paralleled the evolution of rigging on ships during the 1st
millennium A.D., which moved progressively from square sails (primarily drag devices) to
other types of rigging which used lift to facilitate tacking upwind. See, for example, Casson
(1991).
The early northern European windmills all had horizontal axes. They were used for nearly
Any mechanical task, including water pumping, grinding grain, sawing wood, and powering
Tools. The early mills were built on posts, so that the entire mill could be turned to face the
wind (or yaw) when its direction changed. These mills normally had four blades. The
number and size of blades presumably was based on ease of construction as well as an
empirically determined efficient solidity (ratio of blade area to swept area).An example of a
post mill can be seen in Figure 1.3.

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The wind continued to be a major source of energy in Europe through the period just prior
to the Industrial Revolution, but began to recede in importance after that time. The reason
that wind energy began to disappear is primarily attributable to its non-dispatchability and
its nontransportability. Coal had many advantages which the wind did not possess. Coal
could be transported to wherever it was needed and used whenever it was desired. When
coal was used to fuel a steam engine, the output of the engine could be adjusted to suit the
load. Water power, which has some similarities to wind energy, was not eclipsed so
dramatically. This is no doubt because water power is, to some extent, transportable (via
canals) and dispatchable (by using ponds as storage).
Figure 1.3 Post mill
Figure 1.3 Post mill
Prior to its demise, the European windmill had reached a high level of design
sophistication.In the later mills (or ‘smock mills’), such as the one shown in Figure 1.4, the
majority of the mill was stationary. Only the top would be moved to face the wind. Yaw
mechanisms included both manually operated arms and separate yaw rotors. Blades had
acquired somewhat of an airfoil shape and included some twist. The power output of some
machines could be adjusted by an automatic control system. This was the forerunner of the
system used by James Watt on steam engines. In the windmill’s case a fly ball governor
would sense when the rotor speed was changing. A linkage to a tentering mechanism

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Wind energy
Figure 1.4 European smock mill (Hills, 1994).
Figure 1.4 European smock mill (Hills, 1994).
Would cause the upper millstone to move closer or farther away from the lower one, letting
In more or less grain to grind. Increasing the gap would result in more grain being ground
and thus a greater load on the rotor, thereby slowing it down and vice versa.
One significant development in the 18th century was the introduction of scientific testing
and evaluation of windmills. The Englishman John Smeaton, using such apparatus as
illustrated in Figure 1.5,
Discovered three basic rules that are still applicable:
. The speed of the blade tips is ideally proportional to the speed of wind.
. The maximum torque is proportional to the speed of wind squared.
. The maximum power is proportional to the speed of wind cubed.
The 18th century European windmills represented the culmination of one approach to
using wind for mechanical power and included a number of features which were later
incorporated into some early electricity-generating wind turbines.
As the European windmills were entering their final years, another variant of windmill
came into widespread use in the United States. This type of windmill, illustrated in Figure

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1.6, was most notably used for pumping water, particularly in the west. They were used on
ranches for cattle and to supply water for the steam railroads. These mills were distinctive
for their multiple blades and are often referred to as ‘fan mills’. One of their most significant
features was a simple but effective regulating system. This allowed the turbines to run
unattended for long periods. Such regulating systems foreshadowed the automatic control
systems which are now an integral part of modern wind turbines.
Figure 1.5 Smeaton laboratory windmill testing apparatus
Figure 1.5 Smeaton laboratory windmill testing apparatus
Figure 1.6 American water-pumping windmill design
Figure 1.6 American water-pumping windmill design (US Department of Agriculture)
1.2 Early Wind Generation of Electricity
The initial use of wind for electricity generation, as opposed to mechanical power, included
the successful commercial development of small wind generators and research and
experiments using large wind turbines.

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Wind energy
When electrical generators appeared towards the end of the 19th century, it was
reasonable that people would try to turn them with a windmill rotor. In the United States, the
most notable early example was built by Charles Brush in Cleveland, Ohio in 1888. The
Brush turbine did not result in any trend, but in the following years, small electrical
generators did become widespread. These small turbines, pioneered most notably by
Marcellus Jacobs and illustrated in Figure 1.7, were, in some ways, the logical successors
to the water-pumping fan mill. They were also significant in that their rotors had three
blades with true airfoil shapes and began to resemble the turbines of today. Another feature
of the Jacobs turbine was that it was typically incorporated into a complete, residential scale
power system, including battery storage. The Jacobs turbine is considered to be a direct
forerunner of such modern small turbines as the Bergey and Southwest Wind power
machines. The expansion of the central electrical grid under the auspices of the Rural
Electrification Administration during the 1930s marked the beginning of the end of the
widespread use of small wind electric generators, at least for the time being.
The first half of the 20th century also saw the construction or conceptualization of a
Number of larger wind turbines which substantially influenced the development of todays
Technology. Probably the most important sequence of turbines was in Denmark. Between
1891 and 1918 Poul La Cour built more than 100 electricity generating turbines in the
20–35kW size range. His design was based on the latest generation of Danish smock mills.
One of the more remarkable features of the turbine was that the electricity that was
generated was used to produce hydrogen, and the hydrogen gas was then used for lighting.
La Court's turbines were followed by a number of turbines made by Lykkegaard Ltd. and F.
L. Smidth & Co prior toWorldWar II. These ranged in size from 30 to 60kW. Just after the
war, Johannes Juul erected the 200kW Gedser turbine, illustrated in Figure 1.8, in
southeastern Denmark.
Figure 1.7 Jacobs turbine (Jacobs, 1961)
Figure 1.7 Jacobs turbine (Jacobs, 1961)

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This three-bladed machine was particularly innovative in that it employed aerodynamic
stall for power control and used an induction generator (squirrel cage type) rather than the
more conventional (at the time) synchronous generator. This type of induction generator is
much simpler to connect to the grid than is a synchronous generator. Stall is also a simple
way to control power. These two concepts formed the core of the strong Danish presence in
wind energy in the 1980s. One of the pioneers in wind energy in the 1950s was Ulrich
Hutter in Germany (Dorner, 2002). His work focused on applying modern aerodynamic
principles to wind turbine design. Many of the concepts he worked with are still in use in
some form today.
In the United States, the most significant early large turbine was the Smith–Putnam
machine, built at Grandpa’s Knob in Vermont in the late 1930s (Putnam, 1948).With a
diameter of 53.3m and a power rating of 1.25MW, this was the largest wind turbine ever
built up until that time and for many years thereafter. This turbine, illustrated in Figure 1.9,
was also significant in that it was the first large turbine with two blades. In this sense it was
a predecessor of the two-bladed turbines built by the US Department of Energy in the late
1970s and early 1980s. The turbine was also notable in that the company that built it, S.
Morgan Smith, had long experience in hydroelectric generation and intended to produce a
commercial line of wind machines. Unfortunately, the Smith–Putnam turbine was too large,
too early, given the level of understanding of wind energy engineering. It suffered a blade
failure in 1945, and the project was abandoned.
Figure 1.8 Danish Gedser wind turbine

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Figure 1.8 Danish Gedser wind turbine
1.3 The Re-Emergence of Wind Energy
The re-emergence of wind energy can be considered to have begun in the late 1960s. The
book Silent Spring (Carson, 1962) made many people aware of the environmental
consequences of industrial development. Limits to Growth (Meadows et al., 1972) followed
in the same vein, arguing that unfettered growth would inevitably lead to either disaster or
change. Among the culprits identified were fossil fuels. The potential dangers of nuclear
energy also became more public at this time. Discussion of these topics formed the
backdrop for an environmental movement which began to advocate cleaner sources of
energy. In the United States, in spite of growing concern for environmental issues, not much
new happened in wind energy development until the Oil Crises of the mid-1970s. Under the
Carter administration, a new effort was begun to develop ‘alternative’ sources of energy,
one of which was wind energy. The US Department of Energy (DOE) sponsored a number
of projects to foster the development of the technology. Most of the resources were
allocated to large machines, with mixed results. These machines ranged from the 100kW
(38mdiameter) NASA MOD-0 to the 3.2MW Boeing MOD-5B with its 98 m diameter.
Much interesting data was generated but none of the large turbines led to commercial
projects. DOE also supported development of some small wind turbines and built a test
facility for small machines at Rock Flats, Colorado. Number of small manufacturers of wind
turbines also began to spring up, but there was not a lot of activity until the late 1970s.
Figure 1.9 Smith–Putnam wind turbine (Eldridge, 1980)
Figure 1.9 Smith–Putnam wind turbine (Eldridge, 1980)

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The big opportunities occurred as the result of changes in the utility regulatory structure
And the provision of incentives. The US federal government, through the Public Utility
Regulatory Policy Act of 1978, required utilities (1) to allow wind turbines to connect with
The grid and (2) to pay the ‘avoided cost’ for each kWh the turbines generated and fed into
The grid.
The actual avoided cost was debatable, but in many states utilities would pay enough that
wind generation began to make economic sense. In addition, the federal government and
some states provided investment tax credits to those who installed wind turbines. The state
which provided the best incentives, and which also had regions with good winds, was
California. It was now possible to install a number of small turbines together in a group
(‘wind farm’), connect them to the grid, and make some money.
The California wind rush was on. Over a period of a few years, thousands of wind turbines
Were installed in California, particularly in the Altamont Pass, San Gorgonio Pass, and
Tehachipi. A typical installation is shown in Figure 1.10. The installed capacity reached
Approximately 1500MW. The early years of the California wind rush were fraught with
Difficulties, however. Many of the machines were essentially still prototypes, and not yet up
to the task. An investment tax credit (as opposed to a production tax credit) is arguably not
the best way to encourage the development and deployment of productive machines,
especially when there is no means for certifying that machines will actually perform as the
manufacturer claims.
Figure 1.10 California wind farm

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Wind energy
Figure 1.10 California wind farm (National Renewable Energy Laboratory)
When the federal tax credits were withdrawn by the Reagan administration in the early
1980s, the wind rush collapsed.
Wind turbines installed in California were not limited to those made in the United States.
In fact, it was not long before Danish turbines began to have a major presence in the
California wind farms. The Danish machines also had some teething problems in California,
but in general they were closer to production quality than were their US counterparts. When
all the dust had settled after the wind rush had ended, the majority of US manufacturers
had gone out of business. The Danish manufacturers had restructured or merged, but had
in some way survived.
During the 1990s, a decade which saw the demise (in 1996) of the largest US
manufacturer, Kennetech Wind power, the focal point of wind turbine manufacturing
definitively moved to Europe, particularly Denmark and Germany. Concerns about global
warming and continued
Apprehension about nuclear power resulted in a strong demand for more wind generation
there and in other countries as well. The 21st century has seen some of the major
European suppliers establish manufacturing plants in other countries, such as China, India,
and the United States. In recent times, the size of the largest commercial wind turbines, as
illustrated in Figure 1.18, has increased from approximately 25kW to 6MW, with machines
up to 10MWunder design.
The total installed capacity in the world as of the year 2009 was about 115 000MW, with
the majority of installations in Europe. Offshore wind energy systems were also under active
Development in Europe, with about 2000MW installed as of 2008. Design standards and
Machine certification procedures have been established, so that the reliability and
performance are far superior to those of the 1970s and 1980s. The cost of energy from
wind has dropped to the point that in many sites it is nearly competitive with conventional
sources, even without incentives. In those countries where incentives are in place, the rate
of development is quite strong.

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Modern Wind Energy
The re-emergence of the wind as a significant source of the world's energy must rank as
one of the significant developments of the late 20th century. The advent of the steam
engine, followed by the appearance of other technologies for converting fossil fuels to
useful energy, would seem to have forever relegated to insignificance the role of the wind in
energy generation. In fact, by the mid-1950s that appeared to be what had already
happened. By the late 1960s, however, the first signs of a reversal could be discerned, and
by the early 1990s it was becoming apparent that a fundamental reversal was underway.
That decade saw a strong resurgence in the worldwide wind energy industry, with installed
capacity increasing over five-fold. The 1990s were also marked by a shift to large,
megawatt-sized wind turbines, a reduction and consolidation in wind turbine manufacture,
and the actual development of offshore wind power.
During the start of the 21st century this trend has continued, with European countries (and
manufacturers) leading the increase via government policies focused on developing
domestic sustainable energy supplies and reducing pollutant emissions.
To understand what was happening, it is necessary to consider five main factors. First of all
there was a need. An emerging awareness of the finiteness of the earth's fossil fuel
reserves as well as of the adverse effects of burning those fuels for energy had caused
many people to look for alternatives. Second, there was the potential. Wind exists
everywhere on the earth, and in some places with considerable energy density. Wind had
been widely used in the past, for mechanical power as well as transportation. Certainly, it
was conceivable to use it again. Third, there was the technological capacity. In particular,
there had been developments in other fields, which, when applied to wind turbines, could
revolutionize the way they could be used. These first three factors were necessary to foster
the re-emergence of wind energy, but not sufficient. There needed to be two more factors,
first of all a vision of a new way to use the wind, and second the political will to make it
happen. The vision began well before the 1960s with such individuals as Poul la Cour,
Albert Betz, Palmer Putnam, and Percy Thomas. It was continued by Johannes Juul, E. W.
Golding, Ulrich Hutter, and William Heronemus, but soon spread to others too numerous to
mention. At the beginning of wind’s re-emergence, the cost of energy from wind turbines
was far higher than that from fossil fuels. Government support was required to carry out
research, development, and testing; to provide regulatory reform to allow wind turbines to
interconnect with electrical networks; and to offer incentives to help hasten the deployment
of the new technology. The necessary political will for this support appeared at different
times and to varying degrees, in a number of countries: first in the United States, Denmark,
and Germany, and now in much of the rest of the world.
2.1 Modern Wind Turbines
A wind turbine, is a machine which converts the power in the wind into electricity. This is
in contrast to a ‘windmill’, which is a machine which converts the wind's power into
mechanical power. As electricity generators, wind turbines are connected to some electrical

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Wind energy
network. These networks include battery-charging circuits, residential scale power systems,
isolated or island networks, and large utility grids. In terms of total numbers, the most
frequently found wind turbines are actually quite small – on the order of 10 kW or less. In
terms of total generating capacity, the turbines that make up the majority of the capacity
are, in general, rather large – in the range of 1.5 to 5 MW. These larger turbines are used
primarily in large utility grids, at first mostly in Europe and the United States and more
recently in China and India. A typical modern wind turbine, in a wind farm configuration,
connected to a utility network, is illustrated in Figure 2.1. The turbine shown is a General
Electric 1.5 MW and this manufacturer had delivered over 10 000 units of this model at the
time of writing of this text. To understand how wind turbines are used, it is useful to briefly
consider some of the fundamental facts underlying their operation. In modern wind turbines,
the actual conversion process uses the basic aerodynamic force of lift to produce a net
positive torque on a rotating shaft, resulting first in the production of mechanical power and
then in its transformation to electricity in a generator. Wind turbines, unlike most other
generators, can produce energy only in response to the resource that is immediately
available. It is not possible to store the wind and use it at a later time. The output of a wind
turbine is thus inherently fluctuating and nondispatchable. (The most one can do is to limit
production below what the wind could produce.) Any system to which a wind turbine is
connected must, in some way, take this variability into account. In larger networks, the wind
turbine serves to reduce the total electrical load and thus results in a decrease in either the
number of conventional generators being used or in the fuel use of those that are running.
In smaller networks, there may be energy storage, backup generators, and some
specialized control systems. A further fact is that the wind is not transportable: it can only be
converted where it is blowing. Historically, a product such as ground wheat was made at the
windmill and then transported to its point of use. Today, the possibility of conveying
electrical energy via power lines compensates to some extent for wind's inability to be
transported. In the future, hydrogen-based energy systems may add to this possibility.
Figure2.1-Modern utility-scale wind turbine.
Figure2.1-Modern utility-scale wind turbine.

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Of conveying electrical energy via power lines compensates to some extent for wind's
inability to be transported. In the future, hydrogen-based energy systems may add to this
possibility.
2.1.1 Modern wind turbine design
Today, the most common design of wind turbine, and the type which is the primary focus of
this book, is the horizontal axis wind turbine (HAWT). That is, the axis of rotation is parallel
to the ground. HAWT rotors are usually classified according to the rotor orientation (upwind
or downwind of the tower), hub design (rigid or teetering), rotor control (pitch vs. stall),
number of blades (usually two or three blades), and how they are aligned with the wind
(free yaw or active yaw). Figure 2.2 shows the upwind and downwind configurations.
The principal subsystems of a typical (land-based) horizontal axis wind turbine are shown in
Figure 2.3. These include:
. The rotor, consisting of the blades and the supporting hub.
. The drive train, which includes the rotating parts of the wind turbine (exclusive of the
rotor);
It usually consists of shafts, gearbox, coupling, a mechanical brake, and the generator.
. The nacelle and main frame, including wind turbine housing, bedplate, and the yaw
system.
. The tower and the foundation.
. The machine controls.
. The balance of the electrical system, including cables, switchgear, transformers, and
Possibly electronic power converters.
Figure 2.2 HAWT rotor configurations
Figure 2.2 HAWT rotor configurations

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Wind energy
The main options in wind turbine design and construction include:
. Number of blades (commonly two or three);
. Rotor orientation: downwind or upwind of tower;
. Blade material, construction method, and profile;
. Hub design: rigid, teetering, or hinged;
. Power control via aerodynamic control (stall control) or variable-pitch blades (pitch
control);
. Fixed or variable rotor speed;
. Orientation by self-aligning action (free yaw), or direct control (active yaw);
. Synchronous or induction generator (squirrel cage or doubly fed);
. Gearbox or direct drive generator.
2.1.1.1 Rotor
The rotor consists of the hub and blades of the wind turbine. These are often considered
to be the turbine’s most important components from both a performance and overall cost
Standpoint. Most turbines today have upwind rotors with three blades. There are some
downwind rotors and a few designs with two blades. Single-blade turbines have been built
in the past, but are no longer in production. Some intermediate-sized turbines used fixed-
blade pitch and stall control. Most manufacturers use pitch control, and the general trend is
the increased use of pitch control, especially in larger machines. The blades on the majority
of turbines are made from composites, primarily fiberglass or carbon fiber reinforced
plastics (GRP or CFRP), but sometimes wood/epoxy laminates are used.
Figure 2.3 Fiberglass-reinforced epoxy blades of Siemens SWT, blades, lift type blades, drag type blades
Figure 2.3 Fiberglass-reinforced epoxy blades of Siemens SWT, blades, lift type blades, drag type blades

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Wind energy
The blades of the wind turbines are designed in two different ways:
Drag type:
The wind literally pushes the blades out of the way.
Slower rotational speeds and high torque capabilities. Useful for providing mechanical work
(water pumping) figure 2.3.
Lift type:
Most modern HAWT use this design.
Both sides of the blade has air blown across it resulting in the air taking longer to travel
across the edges.
In this way lower air pressure is created on the leading edge of the blade, and higher air
pressure created on the tail edge. Because of this pressure difference the blade is pushed
and pulled around, creating a higher rotational speed that is needed for generating
electricity figure 2.3.
2.1.1.2 Drive Train
The drive train consists of the other rotating parts of the wind turbine downstream of the
rotor. These typically include a low-speed shaft (on the rotor side), a gearbox, and a high-
speed shaft (on the generator side). Other drive train components include the support
bearings, one or more couplings, a brake, and the rotating parts of the generator (discussed
separately in the next section). The purpose of the gearbox is to speed up the rate of
rotation of the rotor from a low value (tens of rpm) to a rate suitable for driving a standard
generator (hundreds or thousands of rpm). Two types of gearboxes are used in wind
turbines: parallel shaft and planetary. For larger machines (over approximately 500 kW), the
weight and size advantages of planetary gearboxes become more pronounced. Some wind
turbine designs use multiple generators, and so are coupled to a gearbox with more than
one output shaft. Others use specially designed, low-speed generators requiring no
gearbox.
While the design of wind turbine drive train components usually follows conventional
Mechanical engineering machine design practice, the unique loading of wind turbine drive
Trains requires special consideration. Fluctuating winds and the dynamics of large rotating
Rotors impose significant varying loads on drive train components.
2.1.1.3 Generator
Nearly all wind turbines use either induction or synchronous generators. These
Designs entail a constant or nearly constant rotational speed when the generator is directly
Connected to a utility network. If the generator is used with power electronic converters, the
Turbine will be able to operate at variable speed.
Many wind turbines installed in grid connected applications use squirrel cage induction

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Wind energy
Generators (SQIG). A SQIG operates within a narrow range of speeds slightly higher than
its synchronous speed (a four-pole generator operating in a 60 Hz grid has a synchronous
speed of 1800 rpm). The main advantages of this type of induction generator are that it is
rugged, inexpensive, and easy to connect to an electrical network. An increasingly popular
option today is the doubly fed induction generator (DFIG). The DFIG is often used in
variable-speed applications.
An increasingly popular option for utility-scale electrical power generation is the variable
speed wind turbine. There are a number of benefits that such a configuration offers,
including the reduction of wear and tear on the wind turbine and potential operation of the
wind turbine at maximum efficiency over a wide range of wind speeds, yielding increased
energy capture. Although there are a large number of potential hardware options for
variable-speed operation of wind turbines, power electronic components are used in most
variable-speed machines currently being designed. When used with suitable power
electronic converters, either synchronous or induction generators of either type can run at
variable speed.
2.1.1.4Gearbox
Gearbox are elements used in transferring torque from one shaft to another. Gears are
described in somewhat more detail in this section than are other elements because they are
widely used in wind turbines. The conditions under which they operate differ in significant
ways from many other applications, and it has been necessary to investigate in some detail
these conditions and the gears’ response so that they perform as desired.
Figure 2.4 gearbox, generator
Figure 2.4 gearbox, generator
There are numerous applications for gears in wind turbines. The most prominent of these is
Probably the drive train gearbox. Other examples include yaw drives, pitch linkages, and
Erection winches. Common types of gears include spur gears, helical gears, worm gears,
and internal gears. All gears have teeth. Spur gears have teeth whose axes are parallel to
the rotational axis of the gear. The teeth in helical gears are inclined at an angle relative to
the gear’s rotational axis. Worm gears have helical teeth, which facilitate transfer of torque
between shafts at right angles to each other. An internal gear is one which has teeth on the
inside of an annulus. Some common types of gears are illustrated in Figure 2.4.
Gears may be made from a wide variety of materials, but the most common material in wind
Turbine gears is steel. High strength and surface hardness in steel gear teeth is often
obtained by carburizing or other forms of heat treating.

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Wind energy
Gears may be grouped together in gear trains. Typical gear trains used in wind turbine
Applications.
Figure 2.5 Gearbox, rotor shaft and brake assembly
Figure 2.5 Gearbox, rotor shaft and brake assembly
Why Use a Gearbox?
The power from the rotation of the wind turbine rotor is transferred to the generator through
the power train, i.e. through the main shaft, the gearbox and the high speed shaft, as we
saw on the page with the Components of a Wind Turbine.
But why use a gearbox? Couldn't we just drive the generator directly with the power from
the main shaft?
If we used an ordinary generator, directly connected to a 50 Hz AC (alternating current)
three phase grid with two, four, or six poles, we would have to have an extremely high
speed turbine with between 1000 and 3000 revolutions per minute (rpm), With a 43 metres
rotor diameter that would imply a tip speed of the rotor of far more than twice the speed of
sound, so we might as well forget it.
Another possibility is to build a slow-moving AC generator with many poles. But if you
wanted to connect the generator directly to the grid, you would end up with a 200 pole
generator (i.e. 300 magnets) to arrive at a reasonable rotational speed of 30 rpm.
Another problem is, that the mass of the rotor of the generator has to be roughly
proportional to the amount of torque (moment, or turning force) it has to handle. So a
directly driven generator will be very heavy (and expensive) in any case.

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Wind energy
2.1.1.5 Nacelle and Yaw System
The nacelle houses a generator and gearbox.
This category includes the wind turbine housing, the machine bedplate or main frame, and
the Yaw orientation system. The main frame provides for the mounting and proper
alignment of the drive train components. The nacelle cover protects the contents from the
weather. A yaw orientation system is required to keep the rotor shaft properly aligned with
the wind. Its primary component is a large bearing that connects the main frame to the
tower. An active yaw drive, always used with upwind wind turbines and sometimes with
downwind turbines, contains one or more yaw motors, each of which drives a pinion gear
against a bull gear attached to the yaw bearing. This mechanism is controlled by an
automatic yaw control system with its wind direction sensor usually mounted on the nacelle
of the wind turbine. Sometimes yaw brakes are used with this type of design to hold the
nacelle in position, when not yawing. Free yaw systems (meaning that they can self-align
with the wind) are often used on downwind wind machines.
Figure 2.6 Nacelle and Yaw System
Figure 2.6 Nacelle and Yaw System
2.1.1.6 Tower and Foundation (base)
This category includes the tower itself and the supporting foundation. The principal types
of tower design currently in use are the free-standing type using steel tubes, lattice (or
truss) towers, and concrete towers. For smaller turbines, guyed towers are also used.

26
Wind energy
Tower height is typically 1 to 1.5 times the rotor diameter, but in any case is normally at
least 20 m. Tower selection is greatly influenced by the characteristics of the site. The
stiffness of the tower is a major factor in wind turbine system dynamics because of the
possibility of coupled vibrations between the rotor and tower. For turbines with downwind
rotors, the effect of tower shadow (the wake created by air flow around a tower) on turbine
dynamics, power fluctuations, and noise generation must be considered. For example,
because of the tower shadow, downwind turbines are typically noisier than their upwind
counterparts.
Figure 2.7Tower and foundation
Figure 2.7Tower and foundation
2.1.1.7 Controls
The control system for a wind turbine is important with respect to both machine operation
and power production. A wind turbine control system includes the following components:
. Sensors – speed, position, flow, temperature, current, voltage, etc.
. Controllers – mechanical mechanisms, electrical circuits;
. Power amplifiers – switches, electrical amplifiers, hydraulic pumps, and valves;
. Actuators – motors, pistons, magnets, and solenoids;
. Intelligence – computers, microprocessors.
The design of control systems for wind turbine application follows traditional control
Engineering practices.
.Wind turbine control involves the following three major aspects and the
Judicious balancing of their requirements:
. Setting upper bounds on and limiting the torque and power experienced by the drive train.
. Maximizing the fatigue life of the rotor drive train and other structural components in the
Presence of changes in the wind direction, speed (including gusts), and turbulence, as well
as start–stop cycles of the wind turbine.

27
Wind energy
. Maximizing the energy production.
The Electronic Wind Turbine Controller
The wind turbine controller consists of a number of computers which continuously monitor
the condition of the wind turbine and collect statistics on its operation. As the name implies,
the controller also controls a large number of switches, hydraulic pumps, valves, and
motors within the wind turbine.
As wind turbine sizes increase to megawatt machines, it becomes even more important that
they have a high availability rate, i.e. that they function reliably all the time.
Communicating with the Outside World
The controller communicates with the owner or operator of the wind turbine via a
communications link, e.g. sending alarms or requests for service over the telephone or a
radio link. It is also possible to call the wind turbine to collect statistics, and check its
present status. In wind parks one of the turbines will usually be equipped with a PC from
which it is possible to control and collect data from the rest of the wind turbines in the park.
This PC can be called over a telephone line or a radio link.
Internal Communications
There is usually a controller both at the bottom of the tower and in the nacelle. On recent
wind turbine models, the communication between the controllers is usually done using fibre
optics. The image to the right shows a fiber optics communications unit. On some recent
models, there is a third controller placed in the hub of the rotor. That unit usually
communicates with the nacelle unit using serial communications through a cable connected
with slip rings and brushes on the main shaft.

28
Wind energy
Fail Safe Mechanisms and Redundancy
Computers and sensors are usually duplicated (redundant) in all safety or operation
sensitive areas of newer, large machines. The controller continuously compares the
readings from measurements throughout the wind turbine to ensure that both the sensors
and the computers themselves are OK. The picture at the top of the page shows the
controller of a megawatt machine, and has two central computers. (We removed the cover
on one of the two computers to show the electronics).
What is monitored?
It is possible to monitor or set somewhere between 100 and 500 parameter values in a
modern wind turbine. The controller may e.g. check the rotational speed of the rotor, the
generator, its voltage and current. In addition, lightning strikes and their charge may be
registered. Furthermore measurements may be made of outside air temperature,
temperature in the electronic cabinets, oil temperature in the gearbox, the temperature of
the generator windings, the temperature in the gearbox bearings, hydraulic pressure, the
pitch angle of each rotor blade (for pitch controlled or active stall controlled machines), the
yaw angle (by counting the number of teeth on yaw wheel), the number of power cable
twists, wind direction, wind speed from the anemometer, the size and frequency of
vibrations in the nacelle and the rotor blades, the thickness of the brake linings, whether the
tower door is open or closed (alarm system).
Control Strategies
Many of the business secrets of the wind turbine manufacturers are to be found in the way
the controller interacts with the wind turbine components. Improved control strategies are
responsible for an important part of the increase in wind turbine productivity in recent years.
An interesting strategy pursued by some manufacturers is to adapt the operational strategy
to the local wind climate. In this way it may e.g. be possible to minimize uneconomic tear
and wear on the machine during (rare) periods of rough weather.
Figure 2.7 Grid Side Controller
Figure 2.7 Grid Side Controller

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Wind energy
2.1.1.8 Balance of Electrical System
In addition to the generator, the wind turbine system utilizes a number of other electrical
Components. Some examples are cables, switchgear, transformers, power electronic
converters, power factor correction capacitors, yaw and pitch motors.
2.1.2 Power Output Prediction
The power output of a wind turbine varies with wind speed and every wind turbine has a
Characteristic power performance curve. With such a curve it is possible to predict the
energy production of a wind turbine without considering the technical details of its various
components. The power curve gives the electrical power output as a function of the hub
height wind speed. Figure 2.8 presents an example of a power curve for a hypothetical wind
turbine.
The performance of a given wind turbine generator can be related to three key points on
the velocity scale:
. Cut-in speed: the minimum wind speed at which the machine will deliver useful power.
. Rated wind speed: the wind speed at which the rated power (generally the maximum
power output of the electrical generator) is reached.
. Cut-out speed: the maximum wind speed at which the turbine is allowed to deliver power
(Usually limited by engineering design and safety constraints).
Figure 2.8 Typical wind turbine power curve
Figure 2.8 Typical wind turbine power curve
Power curves for existing machines can normally be obtained from the manufacturer. The
Curves are derived from field tests, using standardized testing methods. It is also possible
to estimate the approximate shape of the power curve for a given machine. Such a process
involves determination of the power characteristics of the wind turbine rotor and electrical
generator, gearbox gear ratios, and component efficiencies.

30
Wind energy
2.1.3 Other Wind Turbine Concepts
The wind turbine overview provided above assumed a topology of a basic type, namely
one that employs a horizontal axis rotor, driven by lift forces. It is worth noting that a vast
number of other topologies have been proposed, and in some cases built. None of these
has met with the same degree of success as those with a horizontal-axis, lift-driven rotor. A
few words are in order, however, to summarize briefly some of these other concepts. The
closest runner up to the HAWT is the Darrieus vertical axis wind turbine (VAWT). This
concept was studied extensively in both the United States and Canada in the 1970s and
1980s. An example of a VAWT wind turbine (Sandia 17m design (SNL, 2009)) based on
this concept is show in Figure 2.9.
Figure 2.9 Sandia 17-meter Darrieus VAWT
Figure 2.9 Sandia 17-meter Darrieus VAWT (Sandia National Laboratory, 2009)
Despite some appealing features, Darrieus wind turbines had some major reliability
Problems and were never able to match corresponding HAWTs in cost of energy. However,
It is possible that the concept could emerge again for some applications. For a summary of
past work on this turbine design and other VAWT wind turbine designs the reader is
referred to Paraschivoiu (2002), Price (2006), and the summary of VAWT work carried out
by Sandia National Laboratories (SNL) in the US (2009).
Another concept that appears periodically is the concentrator or diffuser augmented wind
turbine. In both types of design, the idea is to channel the wind to increase the productivity
of the rotor. The problem is that the cost of building an effective concentrator or diffuser,
which can also withstand occasional extreme winds, has always been more than the device
was worth.
Finally, a number of rotors using drag instead of lift have been proposed. One concept, the
Savonius rotor, has been used for some small water-pumping applications. There are two
Fundamental problems with such rotors:
(1) They are inherently inefficient.
(2) It is difficult to protect them from extreme winds. It is doubtful whether such rotors will
ever achieve widespread use in wind turbines.

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Wind energy
Figure 2.10 Floating wind turbine concept
S
Figure 2.10 Floatingwindturbine concepts(a), (b) and (c) floating wind turbines, (d) Deepwind concept, (e)
and (f) floating axis wind turbines.
The reader interested in some of the variety of wind turbine concepts may wish to consult
Nelson (1996). This book provides a description of a number of innovative wind systems.
Reviews of various types of wind machines are given in Eldridge (1980) and Le Gourieres
(1982). some of the more innovative designs are documented in work supported by the US
Department of Energy (1979, 1980). A few of the many interesting wind turbine concepts
are illustrated in Figures 2.10 and 2.11.

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Wind energy
Figure 2.11 Various concepts for horizontal axis turbines
Figure 2.11 various concepts for horizontal axis turbines

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Wind energy
Table1 Particulars and component masses of the
Table 1 Particulars and component masses of the VAWT (5 MW) and FAWT (3 MW)
2.2 Future of Wind Turbine
Over 20,000 mw of wind turbines were installed in 2007 bringing worldwide capacity to
94,112 mw, up 27% from 2006. Cheap, Low efficient wind turbines are available in the
market for home use. Five nations – Germany (22,300 mw), the US (16,800 mw), Spain
(15,100 mw) India (8000 mw) and China (6,100 mw) account for 80% of the world’s
installed wind energy capacity. Wind energy continues to be the fastest growing renewable
energy source with worldwide wind power installed capacity reaching 94,112 MW in the
year 2007. In terms of economic value, the global wind market in 2007 was worth about $36
billion, according to Global Wind Energy Council (GWEC). In capacity addition, the US was
in the lead in 2007, followed by China and Spain.

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Wind energy
The power in the wind
The wind systems that exist over the earth’s surface are a result of variations in air
pressure. These are in turn due to the variations in solar heating. Warm air rises and cooler
air rushes in to take its place. Wind is merely the movement of air from one place to
another. There are global wind patterns related to large scale solar heating of different
regions of the earth’s surface and seasonal variations in solar incidence. There are also
localised wind patterns due the effects of temperature differences between land and seas,
or mountains and valleys. Wind speed generally increases with height above ground. This
is because the roughness of ground features such as vegetation and houses cause the
wind to be slowed. Windspeed data can be obtained from wind maps or from the
meteorology office. Unfortunately the general availability and reliability of windspeed data is
extremely poor in many regions of the world. However, significant areas of the world have
mean annual windspeeds of above 4-5 m/s (metres per second) which makes small-scale
wind powered electricity generation an attractive option. It is important to obtain accurate
windspeed data for the site in mind before any decision can be made as to its suitability.
Methods for assessing the mean windspeed are found in the relevant texts.
The power in the wind is proportional to:
• The area of windmill being swept by the wind
• The cube of the wind speed
• The air density - which varies with altitude the formula used for calculating the power in
the wind is shown below:
Power = density of air x swept area x velocity cubed
2 P = ½.ρ.A.V3
Where, P is power in watts (W) ρ is the air density in kilograms per cubic meter (kg/m3) A is
the swept rotor area in square metres (m2) V is the windspeed in metres per second (m/s)
The fact that the power is proportional to the cube of the windspeed is very significant. This
can be demonstrated by pointing out that if the wind speed doubles then the power in the
wind increases by a factor of eight. It is therefore worthwhile finding a site which has a
relatively high mean windspeed. Wind into watts although the power equation above gives
us the power in the wind, the actual power that we can extract from the wind is significantly
less than this figure suggests. The actual power will depend on several factors, such as the
type of machine and rotor used, the sophistication of blade design, friction losses, and the
losses in the pump or other equipment connected to the wind machine. There are also
physical limits to the amount of power that can be extracted realistically from the wind. It
can been shown theoretically that any windmill can only possibly extract a maximum of
59.3% of the power from the wind (this is known as the Betz limit). In reality, this figure is
usually around 45% (maximum) for a large electricity producing turbine and around 30% to

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Wind energy
40% for a wind pump,. So, modifying the formula for ‘Power in the wind’ we can say that the
power which is produced by the wind machine can be given by:
PM = ½.Cp.ρ.A.V3
where, PM is power (in watts) available from the machine Cp is the coefficient of
performance of the wind machine It is also worth bearing in mind that a wind machine will
only operate at its maximum efficiency for a fraction of the time it is running, due to
variations in wind speed.
A rough estimate of the output from a wind machine can be obtained using the
following equation:
PA = 0.2 A V 3
Where, PA is the average power output in watts over the year V is the mean annual
windspeed in m/s
3.1 Principles of wind energy conversion
There are two primary physical principles by which energy can be extracted from the wind;
these are through the creation of either lift or drag force (or through a combination of the
two). The difference between drag and lift is illustrated by the difference between using a
spinnaker sail, which fills like a parachute and pulls a sailing boat with the wind, and a
Bermuda rig, the familiar triangular sail which deflects with wind and allows a sailing boat to
travel across the wind or slightly into the wind. Drag forces provide the most obvious means
of propulsion, these being the forces felt by a person (or object) exposed to the wind. Lift
forces are the most efficient means of propulsion but being more subtle than drag forces
are not so well understood.
The basic features that characterize lift and drag are:
• Drag is in the direction of air flow
• Lift is perpendicular to the direction of air flow
• Generation of lift always causes a certain amount of drag to be developed
• With a good aero foil, the lift produced can be more than thirty times greater than the drag
• Lift devices are generally more efficient than drag devices

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Wind energy
3.2 Types and characteristics of rotors
There are two main families of wind machines: vertical axis machines and horizontal axis
machines. These can in turn use either lift or drag forces to harness the wind. The
horizontal axis lift device is the type most commonly used. In fact other than a few
experimental machines virtually all windmills come under this category. There are several
technical parameters that are used to characterize windmill rotors. The tip speed ratio is
defined as the ratio of the speed of the extremities of a windmill rotor to the speed of the
free wind. Drag devices always have tip-speed ratios less than one and hence turn slowly,
whereas lift devices can have high tip-speed ratios (up to 13:1) and hence turn quickly
relative to the wind. The proportion of the power in the wind that the rotor can extract is
termed the coefficient of performance (or power coefficient or efficiency; symbol Cp) and its
variation as a function of tip-speed ratio is commonly used to characterize different types of
rotor. As mentioned earlier there is an upper limit of Cp = 59.3%, although in practice real
wind rotors have maximum Cp values in the range of 25%-45%. Solidity is usually defined
as the percentage of the area of the rotor, which contains material rather than air. Low-
solidity machines run at higher speed and tend to be used for electricity generation. High-
solidity machines carry a lot of material and have coarse blade angles. They generate much
higher starting torque (torque is the twisting or rotary force produced by the rotor) than low-
solidity machines but are inherently less efficient than low-solidity machines. The wind
pump is generally of this type. High solidity machines will have a low tip-speed ratio and
vice versa.
There are various important wind speeds to consider:
• Start-up wind speed - the wind speed that will turn an unloaded rotor
• Cut-in wind speed – the wind speed at which the rotor can be loaded
• Rated wind speed – the windspeed at which the machine is designed to run (this is at
optimum tip-speed ratio
• Furling wind speed – the windspeed at which the machine will be turned out of the wind to
prevent damage
• Maximum design wind speed – the windspeed above which damage could occur to the
machine
The choice of rotor is dictated largely by the characteristic of the load and hence of the end
use. Some common rotor types and their characteristics are shown in Table 2 below.

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Wind energy
Table 2: Comparison of Rotor Types
Table 2: Comparison of Rotor Types

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Wind energy
How Does a Wind Turbine Generate Electricity?
Wind power converts the kinetic energy in wind to generate electricity or mechanical power.
This is done by using a large wind turbine usually consisting of propellers; the turbine can
be connected to a generator to generate electricity, or the wind used as mechanical power
to perform tasks such as pumping water or grinding grain. As the wind passes the turbines
it moves the blades, which spins the shaft. There are currently two different kinds of wind
turbines in use, the Horizontal Axis Wind Turbines (HAWT) or the Vertical Axis Wind
Turbines (VAWT). HAWT are the most common wind turbines, displaying the propeller or
‘fan-style’ blades, and VAWT are usually in an ‘egg-beater’ style.
Figure 4.1 Wind Turbine Generate Electricity
Figure 4.1 Wind Turbine Generate Electricity
4.1 Converting Wind to Mechanical Energy
Wind is converted by the blades of wind turbines. The blades of the wind turbines are
designed in two different ways, the drag type and lift type.
• Drag type: this blade design uses the force of the wind to push the blades around. These
blades have a higher torque than lift designs but with a slower rotating speed. The drag
type blades were the first designs used to harness wind energy for activities such as
grinding and sawing. As the rotating speed of the blades are much slower than lift type this
design is usually never used for generating large scale energy.
• Lift type: most modern HAWT use this design. Both sides of the blade has air blown
across it resulting in the air taking longer to travel across the edges. In this way lower air

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Wind energy
Figure 4.2 blades rotate the rotor and convert wind energy to mechanical energy
Figure 4.2 blades rotate the rotor and convert wind energy to mechanical energy
Pressure is created on the leading edge of the blade, and higher air pressure created on
the tail edge. Because of this pressure difference the blade is pushed and pulled around,
creating a higher rotational speed that is needed for generating electricity.
4.2 Creating Electricity from Wind
To create electricity from wind the shaft of the turbine must be connected to a generator.
The generator uses the turning motion of the shaft to rotate a rotor which has oppositely
charge magnets and is surrounded by copper wire loops. Electromagnetic induction is
created by the rotor spinning around the inside of the core, generating electricity.
4.3 Distribution of Electricity
The electricity generated by harnessing the wind’s mechanical energy must go through a
transformer in order increase its voltage and make it successfully transfer across long
distances. Power stations and fuse boxes receive the current and then transform it to a
lower voltage that can be safely used by business and homes.
Figure 4.3 Distribution of Electricity
Figure 4.3 Distribution of Electricity

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Wind energy
Wind Energy in Egypt
5.1 Background
In Early 1980`s , the Egyptian Ministry of Electricity & Energy has formulated its national
strategy in the field of New and Renewable Sources of Energy (NRSE) as an integral part of
its global energy strategy. The strategy targeted to supply 5 % of the country’s total primary
needs, from NRSE by the year 2005. The Priority has been given to Wind, Solar and
Biomass.
Wind Energy utilization was promoted to occupy the top of NRSE priorities. This fact was a
result of the national wind resource assessment programme based upon 65 measuring
stations, which proved the abundant wind Energy potential at the western coast of the Gulf
of Suez that reaches 20000 MW. Moreover the North coast of Egypt, South Sinai enjoys
appropriate resources, East Oweinat and Gelf Ridge enjoy a high potential that can reach
80000 MW. The Red Sea Coast at Zafarana was selected for establishment of large scale
Wind farms.
The ambitious Egyptian programme was set up and includes the establishment of a large
scale wind farm in Zafarana of a capacity of 600 MW by year 2005, to be built in successive
phases with each phase having 60 MW capacity. New and Renewable Energy Authority
(NREA) planed that 300 MW shall be financed by the state budget, while the private sector,
local and foreign investors, are encouraged to finance the other 300 MW based on Build ,
Own, Operate and Transfer (BOOT) system.
5.2 Wind Energy Resource
Coastal zones in Egypt enjoy high wind Energy potential. The Red Sea coast particularly at
the Gulf of Suez is one of the highest windy areas of the world.
Figure 5.1 Overview map for the Gulf of Suez in Egypt

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Wind energy
Figure 5.1 Overview map for the Gulf of Suez in Egypt
The coast between Abu-Darag and Hurghada has the most favorable wind condition in
Egypt with average wind speeds between 7-12 mands. The land is desert area, and
although part of this area is being developed to be a touristic resort, large areas of land are
available for wind projects at almost negligible coast.
An overall summary of the wind climates measured at four main stations is given in Table 3.
The station are listed from north to south; Abu Darag, Zafarana and Gulf of El-Zayt are
situated along the Gulf of Suez, Hurghada in the northernmost part of the Red Sea.
5.3 Production capacities
 End 1997: 6 MW
 End 1998: 6 MW (- %)
 End 1999: 36 MW (+500 %)
 End 2000: 69 MW (+91.7 %)
 End 2001: 69 MW (- %)
 End 2002: 69 MW (- %)
 End 2003: 180 MW (+160.9 %)
 End 2004: 145 MW (-19.4 %)
 End 2005: 145 MW (- %)
 End 2006: 230 MW (+58.7 %)
 End 2007: 310 MW (+34.8 %)
 End 2008: 390 MW (+25.9 %)
 End 2009: 430 MW (+10.3 %)
 End 2010: 550 MW (+28 %)
 End 2011: 550 MW (- %)
 End 2012: 550 MW (- %)
 End 2013: 550 MW (- %)

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Wind energy
5.4 Comparison between wind power in Egypt and the world
Table3 Comparison between wind power in Egypt and the world
COUNTRY CAPACITY(MW) Production(GWh) %OF THE WORLD
EGYPT 550 0.14
CHINA 114,763 153,400 31.1
UNITED STATES 65,879 181,719 17.8
WORLD'S TOTAL 369,600 100
Table3 Comparison between wind power in Egypt and the world
5.5 wind farms in Egypt
 Zafarana 1 (30,000 kW, 50 turbines)
Figure 5.2 Zafarana wind farm
Figure 5.2 Zafarana wind farm

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Wind energy
Wind energy in the world
Figure 6.1 Wind speed over the world
Figure 6.1 Wind speed over the world
6.1Wind farm
A wind farm or wind park is a group of wind turbines in the same location used to produce
energy. A large wind farm may consist of several hundred individual wind turbines and
cover an extended area of hundreds of square miles, but the land between the turbines
may be used for agricultural or other purposes. A wind farm can also be located offshore.
Many of the largest operational onshore wind farms are located in China and the United
States. For example, the largest wind farm in the world, Gansu Wind Farm in China has a
capacity of over 6,000 MW of power in 2012 with a goal of 20,000 MW by 2020.
The Alta Wind Energy Center in California, United States is the largest onshore wind farm
outside of China, with a capacity of 1,020 MW. As of April 2013, the 630 MW London Array
in the UK is the largest offshore wind farm in the world, followed by the 504 MW Greater
Gabbard wind farm in the UK.
There are many large wind farms under construction and these include Sinus Holding Wind
Farm (700 MW), Lincs Wind Farm (270 MW), Lower Snake River Wind Project (343 MW),
Macarthur Wind Farm (420 MW).

44
Wind energy
Figure 6.2 The Gansu Wind Farm in China
Figure 6.2 The Gansu Wind Farm in China is the largest wind farm in the world, with a target capacity of 20,000 MW by
2020.
6.1.1 Offshore wind power
Offshore wind power refers to the construction of wind farms in large bodies of water to
generate electricity. These installations can utilize the more frequent and powerful winds
that are available in these locations and have less aesthetic impact on the landscape than
land based projects. However, the construction and the maintenance costs are
considerably higher.
Siemens and Vestas are the leading turbine suppliers for offshore wind power. DONG
Energy, Vattenfall and E.ON are the leading offshore operators. As of October 2010, 3.16
GW of offshore wind power capacity was operational, mainly in Northern Europe. According
to BTM Consult, more than 16 GW of additional capacity will be installed before the end of
2014 and the UK and Germany will become the two leading markets. Offshore wind power
capacity is expected to reach a total of 75 GW worldwide by 2020, with significant
contributions from China and the US.
At the end of 2012, 1,662 turbines at 55 offshore wind farms in 10 European countries are
generating 18 TWh, which can power almost five million households. As of August 2013
the London Array in the United Kingdom is the largest offshore wind farm in the world at
630 MW. This is followed by the Greater Gabbard Wind Farm (504 MW), also in the UK.
The 576 MW Gwynt y Môr wind farm is currently in its final commissioning phase expected
to end in 2015. -
Table 4 the world's 10 largest offshore wind farms
Wind farm
Capacity
(MW)
Country Turbines & model Commissioned
Anholt 400 Denmark
111 × Siemens
2013

45
Wind energy
Wind farm
Capacity
(MW)
Country Turbines & model Commissioned
3.6-120
BARD Offshore 1 400 Germany 80 × BARD 5.0 2013
Greater Gabbard wind farm 504 United Kingdom 140 × Siemens SWT-3.6 2012
Horns Rev II 209 Denmark 91 × Siemens 2.3–93 2009
Lincs 270 United Kingdom 75 × 3.6MW 2013
London Array 630 United Kingdom 175 × Siemens SWT-3.6 2013
Sheringham Shoal 315 United Kingdom
88 × Siemens
3.6-107
2012
Thanet 300 United Kingdom 100 × Vestas V90-3MW 2010
Thorntonbank 325 Belgium
6 × 5MW REpower
and 48 × 6.15MW REpower
2013
Walney 367 United Kingdom 102 × Siemens SWT-3.6 2012
Table 4 the world's 10 largestoffshore wind farms
6.1.2 Onshore wind power
Onshore turbine installations in hilly or mountainous regions tend to be on ridgelines
generally three kilometres or more inland from the nearest shoreline. This is done to exploit
the topographic acceleration as the wind accelerates over a ridge. The additional wind
speeds gained in this way can increase energy produced because more wind goes through
the turbines. The exact position of each turbine matters, because a difference of 30m could
potentially double output. This careful placement is referred to as 'micro-siting'.

46
Wind energy
Table 5 World's largest onshore wind farms
Wind farm
Current
capacity
(MW)
Country
Gansu Wind Farm 6,000 China
Alta (Oak Creek-Mojave) 1,320 United States
Jaisalmer Wind Park 1,064 India
Buffalo Gap Wind Farm 523.3 United States
Capricorn Ridge Wind Farm 662.5 United States
Dabancheng Wind Farm 500 China
Fântânele-Cogealac Wind Farm 600 Romania
Fowler Ridge Wind Farm 599.8 United States
Horse Hollow Wind Energy Center 735.5 United States
Meadow Lake Wind Farm 500 United States
Panther Creek Wind Farm 458 United States
Roscoe Wind Farm 781.5 United States
Shepherds Flat Wind Farm 845 United States
Sweetwater Wind Farm 585.3 United States
Table 5 World's largest onshore wind farms

47
Wind energy
6.2 Wind power capacity and production
Worldwide there are now over two hundred thousand wind turbines operating, with a total
nameplate capacity of 282,482 MW as of end 2012. The European Union alone passed
some 100,000 MW nameplate capacity in September 2012, while the United States
surpassed 50,000 MW in August 2012 and China's grid connected capacity passed 50,000
MW the same month.
World wind generation capacity more than quadrupled between 2000 and 2006, doubling
about every three years. The United States pioneered wind farms and led the world in
installed capacity in the 1980s and into the 1990s. In 1997 German installed capacity
surpassed the U.S. and led until once again overtaken by the U.S. in 2008. China has been
rapidly expanding its wind installations in the late 2000s and passed the U.S. in 2010 to
become the world leader.
Wind power capacity has expanded rapidly to 336 GW in June 2014, and wind energy
production was around 4% of total worldwide electricity usage, and growing rapidly. The
actual amount of electricity that wind is able to generate is calculated by multiplying the
nameplate capacity by the capacity factor, which varies according to equipment and
location. Estimates of the capacity factors for wind installations are in the range of 35% to
44%.
As of 2011, 83 countries around the world were using wind power on a commercial
basis.[15] Several countries have already achieved relatively high levels of penetration,
such as 39% of stationary (grid) electricity production in Denmark (2014), 19% in Portugal
(2011), 16% in Spain (2011).,16% in Ireland (2012) and 8% in Germany (2011).
In Australia, the state of South Australia generates around half of the nation's wind power
capacity. By the end of 2011 wind power in South Australia, championed by Premier (and
Climate Change Minister) Mike Rann, reached 26% of the State's electricity generation,
edging out coal for the first time. At this stage South Australia, with only 7.2% of Australia's
population, had 54% of Australia's installed capacity.
Europe accounted for 48% of the world total wind power generation capacity in 2009. In
2010, Spain became Europe's leading producer of wind energy, achieving 42,976 GWh.
Germany held the top spot in Europe in terms of installed capacity, with a total of 27,215
MW as of 31 December 2010.

48
Wind energy
Figure 6.3 Global wind power cumulative
Table6 Top windpower electricity producing countries in 2012
Country
Wind power
Production
% of World Total
United States 140.9 26.4
China 118.1 22.1
Spain 49.1 9.2
Germany 46.0 8.6
India 30.0 5.6
United Kingdom 19.6 3.7
France 14.9 2.8
Italy 13.4 2.5

49
Wind energy
Table7 Top windpower electricity producing countries in 2012
Figure 6.4 Top windpower electricity producing countries in 2012
Figure 6.4 Top windpower electricity producing countries in 2012
Canada 11.8 2.2
Denmark 10.3 1.9
(rest of world) 80.2 15.0
World Total 534.3 TWh 100%

50
Wind energy
Advantages and disadvantages of wind energy
7.1 Advantages of Wind Energy
 Wind energy is friendly to the surrounding environment, as no fossil fuels are burnt to
generate electricity from wind energy.
 Wind turbines take up less space than the average power station. Windmills only
have to occupy a few square meters for the base, this allows the land around the
turbine to be used for many purposes, for example agriculture.
 Newer technologies are making the extraction of wind energy much more efficient.
The wind is free, and we are able to cash in on this free source of energy.
 Wind turbines are a great resource to generate energy in remote locations, such as
mountain communities and remote countryside. Wind turbines can be a range of
different sizes in order to support varying population levels.
 Another advantage of wind energy is that when combined with solar electricity, this
energy source is great for developed and developing countries to provide a steady,
reliable supply of electricity.
7.1.1 Renewable Energy
Wind energy in itself is a source of renewable energy which means it can be produced
again and again since it is available in plenty. It is cleanest form of renewable energy and is
currently used many leading developed and developing nations to fulfill their demand for
electricity.
7.1.2 Reduces Fossil Fuels Consumption
Dependence on the fossil fuels could be reduced too much extent if it is adopted on the
much wider scale by all the countries across the globe. It could be answer to the ever
increasing demand for petroleum and gas products. Apart from this, it can also help to curb
harmful gas emissions which are the major source of global warming.
7.1.3 Less Air and Water Pollution
Wind energy doesn’t pollute at all. It is that form of energy that will exist till the time sun
exists. It does not destroy the environment or release toxic gases. Wind turbines are mostly
found in coastal areas, open plain and gaps in mountains where the wind is reliable, strong
and steady. An ideal location would have a near constant flow of non-turbulent wind
throughout the year, with a minimum likelihood of sudden powerful bursts of wind.

51
Wind energy
7.1.4 Initial Cost
The cost of producing wind energy has come down steadily over the last few years. The
main cost is the installation of wind turbines. Moreover the land used to install wind turbines
can also be used for agriculture purpose. Also, when combine with solar power, it provides
cheap, reliable, steady and great source of energy for the four developed and developing
countries.
7.1.5 Create Many Jobs
Wind energy on the other hand has created many jobs for the local people. From
installation of wind turbines to maintenance of the area where turbines are located, it has
created wide range of opportunities for the people. Since most of the wind turbines are
based in coastal and hilly areas, people living there are often seen in maintenance of wind
turbines.
Despite these advantages there few disadvantages too which makes wind turbines not
suitable for some locations.
7.2 Disadvantages of Wind Energy
Wind turbines provide clean an effective way of producing power for home or business.
Wind turbines are built in the form of vertical axis and horizontal axis. The more common
type of wind turbines built across the world is the horizontal wind turbine. Wind turbines
have its own impact on wildlife and surrounding environment which contribute towards
disadvantages of wind turbines.
Here’s are some of the major disadvantages of wind turbines.
 The main disadvantage regarding wind power is down to the winds unreliability
factor. In many areas, the winds strength is too low to support a wind turbine or wind
farm, and this is where the use of solar power or geothermal power could be great
alternatives.
 Wind turbines generally produce allot less electricity than the average fossil fuelled
power station, requiring multiple wind turbines to be built in order to make an impact.
 Wind turbine construction can be very expensive and costly to surrounding wildlife
during the build process.
 The noise pollution from commercial wind turbines is sometimes similar to a small jet
engine. This is fine if you live miles away, where you will hardly notice the noise, but

52
Wind energy
what if you live within a few hundred meters of a turbine? This is a major
disadvantage.
 Protests and/or petitions usually confront any proposed wind farm development.
People feel the countryside should be left intact for everyone to enjoy its beauty.
7.2.1 Noise Disturbances
Though wind energy is non-polluting, the turbines may create a lot of noise. This alone is
the reason that wind farms are not built near residential areas. People who live near-by
often complaint of huge noise that comes from wind turbines.
7.2.2 Threat to Wildlife
Due to large scale construction of wind turbines on remote location, it could be a threat to
wild life nearby. Few studies have been done by wind turbines to determine the effect of
wind turbines on birds and animals and the evidence is clear that animals see wind turbines
as a threat to their life. Also, wind turbines require them to be dig deep into the earth which
could have negative effect on the underground habitats.
7.2.3 Wind Can Never Be Predicted
The main disadvantage of wind energy is that wind can never be predicted. In areas where
large amount of wind is needed or winds strength is too low to support wind turbine, there
solar or geothermal energy could prove to be great alternatives. That is one of the reasons
that most of the companies determine wind turbine layout, power curve, thrust curve, long
term wind speed before deploying wind turbines.
7.2.4 Suited To Particular Region
Wind turbines are suited to the coastal regions which receive wind throughout the year to
generate power. So, countries that do not have any coastal or hilly areas may not be able to
take any advantage of wind power. The location of a wind power system is crucial, and one
should determine the best possible location for wind turbine in order to capture as much
wind as possible.
7.2.5 Visual Impact
Though many people believe that wind turbines actually look nice but majority of them
disagree. People consider wind turbines to have an undesirable experience. Petitions
usually comes in court before any proposed wind farm development but few people think
otherwise and feel they should be kept intact for everyone to enjoy its beauty.

53
Wind energy
Although these disadvantages make it look that wind energy may not suitable for every
country but its advantages make it a great source of energy.
Future of wind power technology
8.1 Airborne Wind Turbines
Figure 8.1 airborne wind turbine
Figure 8.1 airborne wind turbine
8.1.1 Makani Airborne Wind Turbine
The Makani Airborne Wind Turbine (AWT) can access stronger and more consistent wind
at altitudes near 1,000 feet, which means that 85% of the US could have viable wind
resources using the device (compared to just 15% using current turbine technology). The
Makani turbine could also be deployed in deep offshore waters, which could lead to access
to a renewable energy resource four times greater than the entire country's electrical
generation capacity.

54
Wind energy
Figure 8.2 Altaeros Airborne Wind Turbine
Figure 8.2 Altaeros Airborne Wind Turbine
8.1.2 Altaeros Airborne Wind Turbine
The Altaeros device uses a helium-filled, inflatable shell to enable it to ascend to high
altitudes, which give it access to stronger and more consistent winds than tower-mounted
turbines, and the generated power is sent to the ground via tethers. The company says
their product could reduce energy costs by up to 65% by harnessing those high altitude
winds, and due to the unique design, installation time can be reduced from weeks to just
days.

55
Wind energy
8.2 Power from Low Speed Winds
Figure 8.3 Wind Harvester
Figure 8.3 Wind Harvester
Wind Harvester
The new Wind Harvester is based on a reciprocating motion that uses horizontal aero foils
similar to those used on aero planes. It is virtually noise-free and can generate electricity at
a low speed, which may result in less opposition to new installations. It will also be
operational at higher wind speeds than current wind turbines.
8.3 Bladeless Wind Power
Figure 8.4 winds talk
Figure 8.4 winds talk

56
Wind energy
Windstalk: Within each hollow pole is a stack of piezoelectric ceramic discs. Between the
ceramic disks are electrodes. Every other electrode is connected to each other by a cable
that reaches from top to bottom of each pole. One cable connects the even electrodes, and
another cable connects the odd ones. When the wind sways the poles, the stack of
piezoelectric disks is forced into compression, thus generating a current through the
electrodes.
8.4 Wind Turbine Lenses
Figure 8.5 Wind Turbine Lenses
Figure 8.5 Wind Turbine Lenses
Wind Lens: Japanese researchers say that they've discovered a simple way to make wind
turbines up to three times as efficient. By placing a 'wind lens' around the turbine blades,
they claim that wind power could become cheaper than nuclear.

57
Wind energy
8.5 Vertical Axis Turbines
Figure 8.6 Windspire
Figure 8.6 Windspire
Windspire: The standard Windspire is 30-feet tall and 4-feet wide, designed to come in under
the typical 35-foot height restrictions of local municipalities. Due to the vertical axis design,
sound levels were tested at 6 decibels above ambient, rendering it virtually inaudible and
the 1.2kW Windspire installed at the [Beekman 1802] farm will produce approximately 2000
kilowatt hours per year in 11 mph average wind.

58
Wind energy
Figure 8.7 Eddy Turbine
Figure 8.7 Eddy Turbine
Eddy Turbine: The eddy turbine is sleek in design, and is safe in wind speeds up to 120
mph. Its cut-in wind speed is 3.5 meters per second, and cut-out speed is 30 meters per
second. This particular turbine can generate 600 watts, and is intended to be combined with
a solar array as a little boost of energy from the breeze.
8.6 Quiet Wind Turbines
Figure 8.8 Eco Whisper Turbine
Figure 8.8 Eco Whisper Turbine

59
Wind energy
Eco Whisper Turbine:
Want wind power, but think that those tri-bladed behemoths are just too loud? Well then,
Australia Renewable Energy Solutions has just the thing for you: The Eco Whisper wind
turbine. This sharp-looking little contraption may only have a 20 kW generating capacity, but
the company claims that the turbine is "virtually silent". It's also, allegedly, more efficient.
8.7 Wind Power Storage
Figure 8.9 Manmade Island Wind Battery Concept
Figure 8.9 Manmade Island Wind Battery Concept
Manmade Island Wind Battery Concept:
The Green Power Island makes use of pumped hydro, a storage strategy that's already in
wide use. Conventional pumped hydro systems use vertically separated reservoirs to utilize
the power of water and gravity; during times of low demand (off peak), water is pumped

60
Wind energy
using excess energy from the lower to the upper reservoir. As demand increases, the water
is allowed to flow downhill into the lower reservoir, generating electricity in the process.
)‫هللا‬ ‫حبمد‬ ‫(مت‬

61
Wind energy
References
1. "Windenergysystems"electroniceditionbyGaryl. JohnsonManhattan,KS.(Book)
2. "WINDENERGY EXPLAINEDTheory,DesignandApplication"SecondEditionbyJ.F.Manwell andJ. G.
McGowan. (Book)
3. Wikipediathe Free Encyclopedia (Website).
4. "WindEnergyin Egypt"AshourAbdel SalamMoussa,NEW & RenewableEnergyAuthority(NREA),
Cairo– Egypt 2005. (Article)
5. Wind energy data for Egypt - General data (Article)
6. How Does a Wind Turbine Generate Electricity (Article)
7. How Does a Wind Turbine Work (Article)
8. The Inside of a Wind Turbine Department of Energy (Article)
9. Advantages and Disadvantages of Wind Energy Clean Energy Ideas (Article)
10. OtherwebsitesandArticles.

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