MAKERERE

UNIVERSITY
COLLEGE OF NATURAL SCIENCES

SCHOOL OF PHYSICAL SCIENCES

DEPARTMENT OF CHEMISTRY

BACHELOR OF SCIENCE IN INDUSTRIAL

CHEMISTRY

COURSE UNIT : ENERGY TECHNOLOGY

GROUP 4
1. LUKYAMUZI RAPHAEL -23/U/10795/PS
2. KYOMUGISHA CHRISTINE - 23/U/0672
3. KATUNGI IAN - 23/U/09341/PS
4. LATIM KIZITO - 23/U/0682
5. KOBUSINGYE VANESSA - 23/U/10211/PS
6. KUTEESA GODSWILL -23/U/10378/PS
7. KIGGWE MARK JOEL -23/U/25733/EXT
WIND ENERGY
Wind is a renewable energy resource generated by harnessing the power of the wind. It is converted
into electricity using wind turbines. Wind energy is eco-friendly and sustainable and helps reduce
greenhouse gas emissions.Wind possesses energy by virtue of its motion. Any device capable of
slowing down the mass of moving air, like a sail or propeller, can extract part of the energy and
convert it into useful work. Wind is caused by the uneven heating of the sun in the atmosphere.
Wind results from moving air due to atmospheric pressure gradients. Wind flows from regions of
higher pressure to those of lower. The greater the atmospheric pressure gradient, the greater the
speed.

HOW WIND TURBINES WORK

• The blowing wind turns the blades in a way that the blade has a lot of air-foil cross sections
on it. These make the blade turn by causing a lift force like in an airplane caused by the
pressure difference. The blade experiences relative speed(Vrelative =Vwind -Vblade). So the
blade is tilted to align with the relative wind speed. This is called the pitch control
mechanism. The purpose of pitch control is to maintain the optimum blade angle to achieve
certain rotor speeds or power output.

• Although the outer edges of the rotor blades move very fast, the central axle (drive
shaft) turns quite slowly. The gearbox converts the low-speed rotation of the drive shaft
(perhaps, 16 revolutions per minute, rpm) into high-speed (perhaps, 1600 rpm) rotation fast
enough to drive the generator efficiently. The brake arrests wind rotation in case there are
excessive wind conditions.

• The generator, immediately behind the gearbox, takes kinetic energy from the spinning drive
shaft by turning the magnet relative to the coils in the generator and this movement induces
current through electromagnetic induction creating an electric potential difference thereby
turning the mechanical energy into electrical energy. The nacelle houses the generator,
gearbox, the brake and other key components.
• The electricity is transferred to the step-up transformer at the bottom of the tower through
a cable. It converts the electricity to about 50 times higher voltage so it can be transmitted
efficiently to the power grid (or to nearby buildings or communities).
 THE WIND TURBINE ALIGNMENT
 The tower is the physical structure that holds the wind turbine. It supports the rotor, nacelle,
blades, and other wind turbine equipment. It also helps to elevate the blades to capture
more wind since the wind speed increases with altitude. The wind turbine should face the
wind normally for maximum power extraction.
 Anemometers (automatic speed measuring devices) and wind vanes on the back of the
nacelle provide measurements of the wind speed and direction. Using these measurements,
the entire top part of the turbine (the rotors and nacelle) can be rotated by a yaw motor,
mounted between the nacelle and the tower, so it faces directly into the oncoming wind and
captures the maximum amount of energy. Yaw refers to the rotation of the entire wind
turbine in the horizontal axis. Yaw control ensures that the turbine is constantly facing into
the wind to maximize the effective rotor area and, as a result, power.

TYPES OF WIND TURBINES

They are mainly grouped according to axis of rotation;

• Horizontal axis wind turbine (HAWT)

• Vertical axis wind turbine (VAWT)

HORIZONTAL AXIS WIND TURBINE (HAWT)

 Horizontal axis wind turbines (HAWT) resemble windmills with propeller-like blades (Like in
airplanes) that spin on a horizontal axis.

 The blades, main rotor shaft, and electrical generator are at the top of a tower and must
face the wind.

 Small turbines use a wind vane to align with the wind, while large turbines use a wind sensor
and servomotor. Large turbines also have a gearbox to increase rotor speed for the
generator.

 To avoid turbulence, turbines are positioned upwind of the tower, and the blades are made
stiff to prevent them from hitting the tower in high winds.

Three mechanical controls of HWAT

1. Pitch Control: Tilting of rotor blade angles from 0 -30° to absorb more energy from the wind. The
pitch angle is the angle between the direction of wind and the direction perpendicular to the planes
of blades.

2. Teethering Control: The up and down movement (swinging motion like see-saw) of nacelle in the
vertical direction. Higher wind speed, the nacelle is inclined.

3. Yaw Control: The horizontal movement of nacelle to face the wind. It’s orientation or steering
control for the axis of wind turbine in the direction of wind.
Design considerations in HAWT
1. The height of the wind energy converter (WEC) should be more than 30m altitude. There only
the wind velocity is higher

2. Few Narrow long blades to withstand the extreme winds.

3. The structural dynamics to be studied completely to avoid fatigue failures of rotors.

Advantages of HAWT
 The tall tower base allows access to stronger wind.

 High efficiency.

Disadvantages
 Massive tower construction is required to support the heavy blades, gearbox, and generator.

 HAWTs require an additional yaw control mechanism to turn the blades toward the wind

 Gearbox, rotor shaft and brake assembly are hard being lifted into position.

 HAWTs generally require a braking device

VERTICAL AXIS WIND TURBINE (VAWT)

Vertical axis wind turbines, as shortened to VAWTs, have the main rotor shaft arranged vertically
thus is set transverse to the wind while the main components are located at the base of the
turbine

CATEGORIES
• The egg-beater, Darrieus style model
 It has blades that are attached to the top and the bottom of a vertical rotor. Although they
have been around for centuries, very few exist today because they do not perform as well as
horizontal-axis turbines.

• Savonius Turbines:
 These turbines have scooped-shaped blades and can also accept wind from any direction.

 They are generally less efficient than Darrieus turbines but have the advantage of simplicity
and reliability.

Advantages
 No yaw mechanisms is needed

 It makes maintenance easier.

 VAWTs have lower wind startup speeds than the typical HAWTs.

 VAWTs may be built at locations where taller structures are prohibited.

 Velocity of the wind can be increased.

Disadvantages
 Low efficiency

 Less energy output

WIND ENERGY STORAGE
• Energy is primarily stored in the form of electricity. When the wind turns the blades of a
wind turbine, it generates electricity through a generator. This electricity is then transmitted
to the grid or used locally.

• To store excess wind energy for later use when the wind isn't blowing, various energy
storage technologies can be employed. One common method is using batteries, where the
electricity generated from wind is used to charge batteries. When there is a demand for
electricity and the wind isn't blowing, the stored energy from these batteries can be
discharged and used.

• Another method of storing wind energy is through pumped hydro storage. Excess electricity
generated from wind can be used to pump water from a lower reservoir to an upper
reservoir. When electricity is needed, the stored water is released from the upper reservoir
to the lower reservoir, passing through turbines to generate electricity.

• In recent years, there has been ongoing research into more advanced energy storage
technologies, such as compressed air energy storage and advanced battery systems, to
efficiently store wind energy and make it available for use when required

FACTORS AFFECTING WIND ENERGY

Several factors can affect wind energy production:

• Wind Speed; Higher wind speeds result in more energy generation. Wind turbines start
producing electricity at a certain minimum wind speed, called the cut-in speed, and reach
their maximum efficiency at a rated wind speed. If the wind speed is too low or too high,
energy production can be limited.

• Wind Turbine Efficiency; Different turbine designs have varying efficiencies. Modern turbines
are more efficient than older models, capturing more energy from the wind.

• Turbine Height; Taller turbines can access higher and more consistent wind speeds. As you
go higher in the atmosphere, wind speeds tend to increase, providing more energy for the
turbines.

• Wind Direction; Wind directionality is essential. Turbines need to be positioned to face the
prevailing winds to capture the maximum energy.
• Air Density; Air density, which is affected by factors like altitude, temperature, and humidity,
affects the power output. Higher altitudes generally have lower air density, leading to
slightly lower energy production.

• Other several factors include; temperature ,terrain and obstructions such as buildings ,trees

BENEFITS
• Wind energy offers several job creation and economic advantages and job Creation, it
creates a significant number of jobs in various fields such as manufacturing, installation,
operation, and maintenance of wind turbines.

• Clean Energy Production: Wind power generates electricity without burning fossil fuels,
which means it doesn’t release harmful greenhouse gases such as carbon dioxide (CO2) into
the atmosphere. This reduces the overall carbon footprint of the energy sector, reducing air
pollution.

• Conservation of Water Resources: Unlike many other forms of power generation, wind
turbines do not require water for cooling. This conservation of water resources is crucial in
regions facing water scarcity and droughts.

• Mitigation of Climate Change: Wind energy plays a significant role in mitigating climate
change by decreasing the demand for electricity generated from fossil fuels. This shift helps
in achieving global climate goals by reducing the overall concentration of greenhouse gases
in the atmosphere.

PROBLEMS FACED IN WIND ENERGY

• Rising Cost of Materials for Manufacturing and Replacement

• Managing Common Wind Turbine Maintenance Problems; Turbine maintenance is a top

priority for wind farm managers while contributing significantly to operating expenses. A few
of the top wind turbine maintenance problems are turbine blade maintenance, Yaw brake
replacement, Cleaning and removing yaw brake dust, Resurfacing brake disks

• Intermittent Energy Source; Wind energy is an intermittent energy source, meaning that it
is not always available when needed.

• Land Use; Wind turbines require large areas of land to be installed, which can have
environmental and social impacts.

THE FUTURE OF WIND ENERGY

 The world is entering a post carbon age and one of the most visible signs of that is
the wind turbine.
 Unlimited amounts of clean energy can replace fossil fuels for good. Ocean wind has
so much potential for the electricity system in the future.
 Engineers are racing to design taller turbines, bigger wind farms and structures that
capture the wind over deeper oceans because if they could harness even a fraction
of the oceans wind, they could supply all the world with electricity.
 There exists a limit on how much energy can be harnessed from the wind know as
the Betz limit (53.9%). Engineers are working tirelessly to get as close to this limit as
they can and the best way they currently known is the use of airfoils.
  Some wind turbines can now capture almost 50% of the winds power and are still
improving.
 One of the current inventions are the off shore wind farms which are going from
strength to strength as the costs plummet.

CASE STUDY: EAST ANGLIA ONE

This is one of the largest offshore wind farms in UK located in the north sea.

Foundations called jackets were used to hold turbines above the water and securely fixed in place by
long piles driven deep into the sea bed.

Jackets were changed from being four legged to three legged.

OFF SHORE SUBSTATION

• This was placed in the middle of the wind turbines and its role is to increase the voltage as
high voltage transmission reduces energy loss and allows more efficient transmission over
long distances.

• Long cables along the sea bed were used for this transmission to an on shore sub station
from which it was connected to the national grid.

• The blades were lengthened from 63 to 75m and are able to twist at an angle .

• 11th July 2020, the final turbine was connected to the UK national grid generating 714 million
watts of electricity powering over 600,000 homes.

• The project was finished on schedule and under budget proof that off shore wind can
generate electricity at a competitive price.

Off shore wind farms were however limited to the coastal line with shallow waters.

This led to the invention of floating wind turbines which can be placed any where in the oceans and
seas.

The latest prototype of a wind turbine has blades which are 107m long and every sweep of its giant
rotor can power a house hold for two days .

• By 2040, experts believe that off shore wind farms have a potential to meet the worlds
electricity demands 11 times over.
GLOBAL TRENDS IN WIND ENERGY PRODUCTION
 REFERENCES
• Ackermann, T. and Soder, L. (2002) An overview of wind energy-status 2002. Renewable and
Sustainable Energy Reviews, 6, 67–127.
• Berger, J. J. (1997) Charging Ahead: The Business of Renewable Energy and What it Means
for America. University of California Press, Berkeley.
• https://m.youtube.com/watch?
v=f0p0Fria5TY&t=2647s&pp=ygUcZG9jdW1lbnRhcnkgcmVuZXdhYmxlIGVuZXJneQ%3D%3D