Wind Energy
Alaa Hesham
Energy Geeks
Table of Contents
Abstract ........................................................................................................................................... 4
Introduction ..................................................................................................................................... 4
Components of Wind Turbine ........................................................................................................ 4
Essential elements of wind plant..................................................................................................... 5
Wind Turbine .............................................................................................................................. 5
1)
Rotor ............................................................................................................................. 5
2)
Drive Train ................................................................................................................... 5
3)
Generator ...................................................................................................................... 5
4)
Nacelle and Yaw System .............................................................................................. 6
5)
Tower and Foundation .................................................................................................. 6
6)
Controls ........................................................................................................................ 6
Electricity generation principle ................................................................................................... 7
1.
Capturing Wind Energy ................................................................................................ 7
2.
Mechanical Energy Convertion .................................................................................... 7
3.
Electrical Energy Generating........................................................................................ 7
Betz Theory..................................................................................................................................... 8
Solution of the Problem .................................................................................................................. 9
Applications .................................................................................................................................. 10
Hybrid Energy Systems ............................................................................................................ 10
Wind-Solar Hybrid Systems: ................................................................................................ 10
Wind-Diesel Hybrid Systems ............................................................................................... 10
Electricity Generation ............................................................................................................... 10
Utility-Scale Wind Farms ..................................................................................................... 10
Offshore Wind Farms ........................................................................................................... 10
Water Pumping ......................................................................................................................... 10
Agriculture: ........................................................................................................................... 10
Drinking Water: .................................................................................................................... 10
Distributed or Small-Scale Wind Power ................................................................................... 10
Residential Use ..................................................................................................................... 10
Rural Electrification .............................................................................................................. 10
Wind-Pumped Hydro Storage ................................................................................................... 10
production capacity ....................................................................................................................... 11
Production percentage compered to whole production of the region ........................................... 11
Production Percentage for some countries ................................................................................ 11
Production Percentage for some Regions ................................................................................. 11
“LCOE” of wind power according to period between year of 2000 to 2020. .............................. 12
Onshore Wind: ...................................................................................................................... 12
Offshore Wind ...................................................................................................................... 12
Advantages of Wind Energy ......................................................................................................... 12
Disadvantages of Wind Energy .................................................................................................... 12
Conclusion .................................................................................................................................... 13
Sources .......................................................................................................................................... 13
TABLE OF FIGURES
FIG.1 ........................................................................................... 4
FIG.2 ........................................................................................... 5
FIG.3 ........................................................................................... 7
FIG.4 ........................................................................................... 9
FIG.5 ......................................................................................... 11
FIG.6 ......................................................................................... 12
Abstract
Wind power is a rapidly growing renewable energy source that harnesses the kinetic energy of
wind to generate electricity. This report provides an overview of wind power technology, including
the principles of operation, types of wind turbines, key components, and the advantages and
challenges associated with wind energy.
Introduction
Wind power is one of the most mature and widely deployed renewable energy technologies. It
plays a critical role in reducing greenhouse gas emissions and mitigating climate change by
providing a clean, sustainable alternative to fossil fuels. As of 2023, wind energy accounts for a
significant portion of global electricity generation, with continued growth expected in the coming
decades.
Components of Wind Turbine
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). The principal
subsystems of a typical (land-based) horizontal axis wind turbine includes:
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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.
The main options in wind turbine design and construction
include:
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Fig.1
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).
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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.
Essential elements of wind plant
Wind Turbine
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
Fig.2
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.
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.
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 generators (SQIG). SQIG is a four-pole generator operating in a 60 Hz grid has a
synchronous speed of 1800 rpm, and it operates within a narrow range of speeds slightly higher
than its synchronous speed. 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) which 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.
4) Nacelle and Yaw System
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 that can self-align with the wind, are
often used on downwind wind machines.
5) Tower and Foundation
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. 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 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.
6) 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:
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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.
Wind turbine control involves the following three major aspects and the judicious balancing of
their requirements:
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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.
Maximizing the energy production.
Electricity generation principle
Electricity generation from wind begins with kinetic energy conversion. Wind turbines capture
wind energy, transforming it into mechanical power, then into electricity through a generator. This
process involves several key components and principles of physics and engineering.
1. Capturing Wind Energy
The process begins with the wind, which is a form of kinetic energy.
When wind flows across the rotor blades of a turbine, it creates a
pressure difference between the front and back of the blades. This
pressure difference generates lift, causing the blades to rotate. The rotor
blades are designed with an aerodynamic shape to maximize energy
capture from the wind.
2. Mechanical Energy Convertion
The rotating blades are connected to a central hub, which is part of the
rotor assembly. As the blades spin, they turn the rotor, converting the
kinetic energy of the wind into mechanical energy. The rotor is
connected to a shaft, which transfers this rotational energy to the
Fig.3
generator. The rotor turns a low-speed shaft, which rotates at the same
speed as the blades (typically 10–60 RPM). In many turbines, a gearbox is
used to increase the rotational speed from the low-speed shaft to a high-speed shaft (typically
1,000–1,800 RPM), which is suitable for the generator.
3. Electrical Energy Generating
The high-speed shaft is connected to a generator, which converts the mechanical energy into
electrical energy. The generator operates on the principle of electromagnetic induction, discovered
by Michael Faraday. When a conductor moves through a magnetic field, it induces an electric
current in the conductor. In a wind turbine generator, the rotating shaft turns a set of magnets or
electromagnets inside a coil of wire, creating an electric current.
Betz Theory
Betz's Law, also known as the Betz Limit, is a fundamental principle in wind energy that defines
the maximum theoretical efficiency with which a wind turbine can convert the kinetic energy of
wind into mechanical energy. Betz's Law states that no wind turbine can capture more
than 59.3% of the kinetic energy in the wind. This value is known as the Betz Limit or Betz
Coefficient. The limit arises due to the inherent nature of energy extraction from a fluid. When a
wind turbine extracts energy from the wind, it slows down the wind speed, and the remaining
energy must continue downstream to maintain the flow. The turbine is represented by a uniform
‘actuator disc’ which creates a discontinuity of pressure in the stream tube of air flowing through
it. This analysis is not limited to any particular type of wind turbine. This analysis uses the
following assumptions:
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Homogenous, incompressible, steady state fluid flow.
No frictional drag.
An infinite number of blades.
Uniform thrust over the disc or rotor area.
A non–rotating wake.
The static pressure far upstream and far downstream of the rotor is equal to the undisturbed
ambient static pressure.
Wind turbine rotor performance is usually characterized by its power coefficient, CP:
The Turbine Power:
The Wind Power:
The maximum CP is determined by taking the derivative of the power coefficient:
Solution of the Problem
Fig.4
Applications
Hybrid Energy Systems
A hybrid energy system combines multiple types of energy generation and/or storage or uses two
or more kinds of fuel to power a generator. A hybrid energy system is a valuable method in the
transition away from fossil fuel based economies. Particularly in the short term, while new
technologies to better integrate renewable energy sources are still being developed, backing up
renewable generation with conventional thermal electric production can actually help expand the
use of renewable energy sources.
Wind-Solar Hybrid Systems:
Combining solar and wind energy into a hybrid renewable energy system can be done in various
ways to optimize energy production, reliability, and efficiency. Wind and solar energy complement
each other, as wind speeds are often higher at night or during cloudy weather when solar panels
are less effective.
Wind-Diesel Hybrid Systems
In remote or off-grid areas, wind turbines are paired with diesel generators to reduce fuel
consumption and emissions.
Electricity Generation
Utility-Scale Wind Farms
Large-scale wind turbines generate electricity for the grid, powering homes, businesses, and
industries.
Offshore Wind Farms
Located in bodies of water, these farms harness stronger and more consistent winds to produce
large amounts of electricity.
Water Pumping
Agriculture: Wind-powered pumps are used for irrigation and livestock watering.
Drinking Water: Wind energy pumps groundwater for drinking and domestic use in remote areas.
Distributed or Small-Scale Wind Power
Residential Use: Small wind turbines provide electricity for individual homes or farms.
Rural Electrification: Wind energy powers remote or off-grid communities where extending the
grid is impractical or expensive.
Wind-Pumped Hydro Storage
Wind energy is used to pump water into elevated reservoirs, which can later be released to generate
hydroelectric power during periods of high demand.
production capacity
Fig.5
Production percentage compered to whole production of the region
Globally, wind energy accounts for 7-8% of electricity production, with significant growth
potential, especially in offshore wind and developing regions. Wind energy contributes the highest
percentage in Denmark (55%) and Iowa (62%).
Production Percentage for some countries
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1.
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Denmark: ~55%
Germany: ~27%
Spain: ~24%
United Kingdom: ~25%
United States: ~10%
China: ~9%
India: ~5%
Brazil: ~11%
Production Percentage for some Regions
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1. European Union: ~17%
2. Asia: ~5%
3. North America: ~8%
4. Latin America: ~6%
5. Africa: ~1%
In Africa Wind energy is growing in countries like South Africa, Morocco, and Kenya, but
adoption is still in early stages.
“LCOE” of wind power according to period between year of 2000 to 2020.
The Levelized Cost of Energy (LCOE) for wind power has decreased significantly between 2000
and 2020 due to technological advancements, economies of scale, and increased efficiency in
manufacturing and installation.
Onshore Wind:
 Saw a 50–60% reduction in LCOE between 2000 and 2020.
 Improvements in turbine design, taller towers, longer blades, and better materials drove cost
reductions.
 Economies of scale and increased competition in the wind energy sector also contributed.
Offshore Wind
 Experienced a 40–50% reduction in LCOE between 2000 and 2020.
 Larger turbines, floating platforms, and improved installation techniques reduced costs.
 Offshore wind remains more expensive than onshore due to higher installation and
maintenance costs.
Fig.6
Advantages of Wind Energy
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Sustainable and Clean: Produces no greenhouse gases or pollutants during operation.
Cost-Effective: Once established, operational costs are relatively low.
Land Efficiency: Wind farms can coexist with agricultural uses.
Disadvantages of Wind Energy
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Intermittency: Wind isn’t constant; thus, energy generation can be unpredictable.
Noise and Aesthetic Concerns: Turbine noise and visual impact are common criticisms.
Wildlife Impact: Birds and bats can be affected by turbine blades.
Conclusion
Wind energy has emerged as a cornerstone of the global transition to renewable energy, offering
a sustainable, cost-effective, and environmentally friendly solution to meet growing energy
demands. Over the past two decades, significant advancements in technology, coupled with
supportive policies and economies of scale, have dramatically reduced the Levelized Cost of
Energy (LCOE) for both onshore and offshore wind power. Onshore wind, in particular, has
become one of the most affordable sources of electricity, competitive with traditional fossil fuels
in many regions. Offshore wind, while initially more expensive, has also seen substantial cost
reductions and is increasingly playing a critical role in the energy mix, especially in regions with
high wind potential. The versatility of wind energy is evident in its wide range of applications,
from utility-scale electricity generation to small-scale distributed systems, water pumping, and
even hydrogen production. Countries like Denmark, Germany, and the United States have
demonstrated the potential of wind energy to contribute significantly to national energy portfolios,
with some regions generating over 50% of their electricity from wind. Looking ahead, the
continued growth of wind energy will depend on sustained investment in technology,
infrastructure, and grid integration. Offshore wind, in particular, holds immense potential for
further expansion, especially as floating turbine technology matures. Additionally, the integration
of wind energy with other renewable sources and energy storage systems will enhance its
reliability and scalability. In conclusion, wind energy is not only a key driver of the global shift
toward a low-carbon future but also a testament to the power of innovation and collaboration in
addressing the world's energy challenges. As we move forward, harnessing the full potential of
wind energy will be essential for achieving climate goals, ensuring energy security, and fostering
sustainable economic growth.
Sources
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https://retgen.com/en/electricity-generation-with-wind-energy/
https://www.energyencyclopedia.com/en/renewable-energy/wind-energy/wind-turbine-andits-working-principle
https://www.unescap.org/sites/default/files/35.%20FS-Hybrid-energy-system.pdf
Wind Energy Explained, Theory, design, and application. second edition