UNIT-2 WIND ENERGY

INTRODUCTION - BASIC PRINCIPLES OF WIND ENERGY CONVERSION, THE NATURE

OF WIND

Wind energy, also known as wind power, is a form of renewable energy that converts the
kinetic energy of moving air (wind) into mechanical or electrical energy.

This conversion is typically achieved through wind turbines, which have blades that are
rotated by the wind, turning a generator to produce electricity.

Here's a more detailed explanation:

 Renewable Resource:
Wind energy is considered a renewable resource because it is naturally replenished and will not be
depleted through use.
 Kinetic Energy:
The moving air possesses kinetic energy, which is the energy of motion.
 Wind Turbines:
Wind turbines are the devices used to capture the kinetic energy of the wind. They typically consist of
blades that rotate when exposed to wind, turning a generator to produce electricity.
 Electricity Generation:
The rotating blades of the wind turbine drive a generator, which converts the mechanical energy into
electrical energy.
 Applications:
Wind energy can be used for various purposes, including:
 Generating electricity for homes, businesses, and communities.
 Pumping water for irrigation and other uses.
 Producing hydrogen, which can be used as a fuel source.

Advantages of Wind Energy:

1. Wind Energy Is Renewable & Sustainable

2. It’s Also Environmentally Friendly

3. It Can Reduce Fossil Fuel Consumption

4. Wind Energy is Free

5. It Has A Small Footprint

6. Both Industrial & Domestic Wind Turbines Exist

7. Wind Energy Can Provide Power For Remote Locations

 8. Wind Technology is Becoming Cheaper

9. It Is Also Low Maintenance.

10. It Has Low Running Costs

12. It Can Increase Energy Security

13. The Wind Energy Industry Creates Jobs

Disadvantages of Wind Energy

1.The Wind Fluctuates

2. Installation is Expensive

3. Wind Turbines Pose A Threat to Wildlife

4. Wind Turbines Create Noise Pollution

5. They Also Create Visual Pollution

APPLICATIONS OF WIND ENERGY

1. Electricity generation

2. Agriculture and irrigation

3. Transportation

4. Urban and industrial applications

THE BASIC PRINCIPLE OF WIND ENERGY CONVERSION

involves capturing the kinetic energy of wind and transforming it into mechanical energy, which is
then converted into electricity. A wind turbine, the key component, uses blades to convert wind
energy into rotational motion, which drives a generator to produce electricity.

1. Wind capturing and mechanical energy generation

 Blades: The wind turbine blades are aerodynamically designed to capture the wind's kinetic energy and
convert it into rotational motion.

 Rotor: The blades are attached to a central hub, forming the rotor. When wind pushes the blades, the
rotor rotates.

 Shaft: The rotating rotor turns a low-speed shaft connected to a gearbox.

 2. Speed multiplication and electrical energy generation

 Gearbox: The gearbox increases the rotational speed of the shaft to a much higher speed required for the
generator to efficiently produce electricity.

 High-speed shaft: The gearbox's output shaft (high-speed shaft) is connected to the generator.

 Generator: The generator converts this fast rotational motion (mechanical energy) into electrical energy
(electricity).

3. Power conditioning and grid integration

 Transformer: The generated electricity might need to be stepped up in voltage by a transformer to be

compatible with the transmission grid.

 Transmission: The electricity is then transmitted through power lines to the electrical grid for distribution
and use.

 Control Systems: Wind turbines also incorporate control systems to monitor and optimize performance,
ensuring efficient energy capture and regulating power output based on wind conditions and grid
requirements


4. Types of Wind Turbines:
 HAWT (Horizontal Axis Wind Turbine): The most common type, with blades rotating around a horizontal
axis.
 VAWT (Vertical Axis Wind Turbine): Blades rotate around a vertical axis.

5. Nature of Wind:
 Wind is essentially air in motion, driven by pressure differences in the atmosphere.
 The primary driver of these pressure differences is the sun's uneven heating of the Earth's surface.
 Areas with higher temperatures have lower air pressure, while cooler areas have higher pressure. Air
naturally moves from high to low pressure zones, creating wind.
 Factors like the Earth's rotate and local geography also influence wind patterns.
6. Factors Affecting Wind Energy:
 Wind speed: Higher wind speeds result in greater energy capture.
 Turbine design: Aerodynamic efficiency of the blades and overall design play a crucial role.
 Location: Geography, topography, and climate influence wind patterns and availability.
 Turbine height: Taller towers generally experience higher wind speeds.
 Environmental factors: Mountains, bodies of water, and vegetation can affect wind flow.
WIND TURBINE POWER
How Wind Power Is Generated: The terms "wind energy" or "wind power" describe the process by which
the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in
the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding
grain or pumping water) or a generator can convert this mechanical power into electricity to power
homes, businesses, schools, and the like.

The major components of a typical wind energy conversion system include a wind turbine,
a generator, interconnection apparatus, and control system.
The most important part of a wind energy conversion system is the wind turbine
transforming the wind kinetic energy into mechanical or electric energy.
The system basically comprises a blade, a mechanical part and an electric engine coupled
to each other. The kinematical energy of wind is the function of wind speed, the specific
mass of air, the area of air space where the wind is captured and the height at which the
rotor is placed.

The power available in a uniform wind field can as expressed as

Pw=1/2ρAv3

where Pw is the power [W] of the wind with air

density ρ [kg/m3] and wind speed v [m/s] is passing through the swept area A [m2] of a rotor
disk that is perpendicular to the wind flow.
The wind turbine can only capture a fraction of the power available from the wind.
The ratio of captured power to available power is referred to as the power coefficient
Cp=(β,λ)

which is a function of the collective blade pitch angle β and the tip-speed ratio λ.

This is how electricity from wind is produced, step by step:

1. The blades of a wind turbine capture the wind's kinetic energy. When the wind blows, it
makes the blades go round. The stronger the wind blows, the faster the wings rotate.
2. As the blades turn, they transfer power to a drive shaft. The drive shaft is like a long rod
that runs from the blades to the generator in the machine house.
3. The generator then converts that kinetic energy into electrical energy.
4. Next, the electricity then goes down through the tower of the wind turbine before being
sent out to the power grid and ending up in homes, schools, workplaces, factories, etc.
5. As long as the wind is blowing, a wind turbine can produce electricity.
About Power in the Wind

Wind pressures energy under its motion. A portion of the energy can be extracted from the flowing mass of air and
transformed into usable work by any mechanism that can slow it down, such as a sail or propeller. The following three
variables affect a wind energy converter's output:

o The wind speed

o The cross-section of wind swept by the rotor
o The overall conversion efficiency of the rotor, transmission system, and generator.

A well- designed wind turbine machine blades will exact 70% of the power available from wind energy

No device, however, well-designed can extract all of the wind's energy because the wind would have to be brought to
a halt and this would prevent the passage of more air through the rotor. The most possible outcome is for the rotor to
decelerate the whole horizontal column of intercepted air to about one-third of its free velocity. Therefore, the amount
of wind energy that could be converted into mechanical energy by a 100% efficient aerogenerator would be limited to
about 60%. A wind turbine's overall efficiency may drop to 35% or less due to losses in the gearbox, transmission
system, generator, or pump, even though well-designed blades typically take 70% of the theoretical maximum.

We know the wind machine will work on the principle of Converting the Kinetic energy of the wind to mechanical
energy.

(∴Kinetic Energy of the wind=12mV2).....(1)

Mass of the Air, m=(ρAV)......(2)
Where,

o (ρ) = Density of the Air

o A = Traversing area
o V = Velocity of air

Substituting the value of m in equation 1 we have,

KineticEnergy=(12(ρAV)×V2)
=(12(ρAV3)Watts).………….3
We know that Power is equal to energy per unit time

Let D be the diameter of the turbine blades

(∴A=Π4D2 in m2)
% during the year because of pressure and temperature, change and it is neglected. ∴ Available Power of the
We can say that a small change in wind speed will increase the effect on the power in the wind. But it may vary 10-15

wind (Pa=12ρ(Π4D2)V3 Watts)

 WIND ENERGY CONVERSION
A WECS operates on a simple principle: wind rotates turbine blades connected to a generator, which
produces electricity. The basic steps involved are:

1. Wind Capture: Wind blows against the turbine blades, causing them to rotate.

2. Mechanical Energy Conversion: The rotating blades spin a shaft, which is connected to a gearbox. The
gearbox increases the rotational speed to a level suitable for the generator.

3. Electricity Generation: The high-speed shaft drives an electric generator, which converts the mechanical
energy into electrical energy.

4. Power Conditioning and Transmission: The electricity is then processed by a power converter to convert
direct current (DC) to alternating current (AC) and a step-up transformer to increase the voltage for
efficient transmission to the power grid.

Key components of a WECS

The major components of a WECS can be categorized as mechanical and electrical.

Mechanical components

 Rotor: This is the rotating part of the turbine, consisting of the blades and hub, which captures the wind's
kinetic energy.

 Main Shaft: Connects the rotor to the gearbox and transmits the rotational force.

 Gearbox: Increases the rotational speed from the rotor to the generator.

 Nacelle: The housing that contains the gearbox, generator, controller, and brake, and protects them from
weather conditions.

 Pitch and Yaw Drives: Adjust the angle of the blades and the turbine's orientation to optimize wind
capture and control power output.

Electrical components

 Generator: Converts mechanical energy into electrical energy.

 Power Converter: Transforms direct current (DC) electricity to alternating current (AC) and ensures
compatibility with the grid.

 Step-up Transformer: Increases the voltage of the electricity for efficient transmission.

 Wind Farm Collection Points or Point of Common Coupling: Where the electricity from multiple turbines is
collected before transmission to the grid.
 Basic Components of Wind Energy Conversion System

Aero turbines convert kinetic energy of wind to rotary mechanical energy. A mechanical interface
consisting of a step up gear and a suitable coupling transmits this rotary mechanical energy to an
electric generator, which generates electricity. Aero turbines requires a pitch control and yaw control for
proper operation. Yaw control is fitted to rotate the turbine about vertical (or yaw) axis, so that the blades
always faces the wind.

Gear box: The function of gear box is to step up the speed as per needed by the electric generator.
The low speed shaft is connected to the high speed shaft with gears. It increases the rotational speed
that is required for the generator to generate electricity. The increase in rotational speeds is of the
order 30-60 rpm to 1000-1800 rpm. This part is very costly. Some of the types of gear boxes are
Planetary Gear Boxes, Parallel shaft gear.

Coupling: Connects the turbine shaft to the generator or gearbox.

Brake: This part is meant to stop the running of wind turbines during extreme weather conditions.
The various types of brakes are Mechanical brake (Disc brake, clutch brake), Aerodynamic brake
(Tip brake and spoilers)

Generator: The conversion of rotational energy to electrical energy is carried out by generator. In
general the wind driven electric generator produces 50-cycle AC electricity. The types of generators
are

 – Synchronous generator (Electrically excited, permanent magnet),

 – Asynchronous generator (SQIG -Squirrel cage induction generators, Slip ring)

Transmission: The transmission options include mechanical systems involving fixed ratio gears,
belts and chains singly or in combinations or hydraulic systems involving fluid pumps and motors

Controller: The grid quality electric current is controlled by the controller of the turbine system.
The controller starts up the machine at cut-in wind speed (generally 3 m/s) and shuts off the machine
at cut-out wind speed (generally 25 m/s) as per the design requirement. The controller measures and
controls parameters like Voltage, current, frequency, Temperature inside nacelle, Wind direction,
Wind speed, The direction of yawing, shaft speed, Over-heating of the generator, Hydraulic pressure
level, Correct valve function, Vibration level, Twisting of the power cable, Emergency brake circuit,
Overheating of small electric motors for the yawing, hydraulic pumps, Brake caliper adjustment etc.
The of a control system includes

(a) Sensors - Mechanical, electrical or pneumatic .Actuators-Hydraulic, electric or pneumatic.

Anemometer: Anemometer is an instrument that measures wind speed. It gives the input to the
controller for power regulation and braking beyond the cut out & survival wind speed. Generally the
anemometer is fixed on top of wind turbine.

Pitch: The electricity production is controlled by pitch under different wind intensities. Blades are
turned or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds
that are too high or too low to produce electricity.

Yaw Control : The function of this is to keep the turbine aligned to the wind. Two types of yaw drive
systems are active yaw or free yaw systems.

Active yaw drive mechanism is with yaw motors and is controlled by automatic yaw control system
with its wind direction sensor mounted on nacelle.

Free yaw systems can self-aligned with the wind and commonly used on downwind wind turbine
systems

Nacelle: The covered part of the wind turbine system over the top of tower is nacelle. It houses
gear box, low speed shaft and high-speed shaft, generator, controller, and brake.

It has an important role in protection of components of wind turbine from the various weather
conditions.

It also helps in reduction of noise produced from the rotation of wind turbine.

Tower: This helps to use the wind energy at sufficient heights above ground. This helps to absorb
and securely discharge static and dynamic stress exerted on the rotor, the power train and the nacelle
into the ground. The major types of towers used in wind turbine are Lattice tower, Tubular tower,
Guyed tower, Hybrid Tower

Site Selection Consideration For WECS(Wind Energy Conversion)

1. High annual average wind speed:
2. Availability of anemometry data:
3. Availability of wind V(t) Curve at the proposed site:
4. Wind structure at the proposed site:
5. Altitude of the proposed site:
6. Terrain and its aerodynamic:
7. Local Ecology
8. Distance to road or railways:
9. Nearness of site to local centre/users:
10. Nature of ground:
11. Favourable land cost:
1. High annual average wind speed:
The speed generated by the wind mill depends on cubic values of velocity of wind, the small increases in
velocity markedly affect the power in the wind.

It is obviously desirable to select a site for WECS with high wind velocity.

2. Availability of anemometry data:

It is another improvement sitting factor. The anemometry data should be available over some time period
at the precise spot where any proposed WECS is to be built and that this should be accomplished before a
sitting decision is made.
3.Availability of wind V(t) Curve at the proposed site:This important curve determines the
maximum energy in the wind and hence is the principal initially controlling factor in predicting
the electrical output and hence revenue return o the WECS machines.
It is desirable to have average wind speed ‘V’ such that V>=12-16 km/hr (3.5 – 4.5 m/sec).
4. Wind structure at the proposed site:
The ideal case for the WECS would be a site such that the V(t) Curve was flat, i.e., a smooth steady wind
that blows all the time; but a typical site is always less than ideal. Wind specially near the ground is
turbulent and gusty, and changes rapidly in direction and in velocity.
5. Altitude of the proposed site:
It affects the air density and thus the power in the wind and hence the useful WECS electric power
output. Also, as is well known, the wind tend to have higher velocities at higher altitudes. One must be
carefully to distinguish altitude from height above ground. They are not the same except for a sea level
WECS site.
6. Terrain and its aerodynamic:
One should know about terrain of the site to be chosen. If the WECS is to be placed near the top but not
on the top of a not too blunt hill facing the prevailing wind, then it may be possible to obtain a ‘speed-
up’ of the wind velocity over what it would otherwise be.
7. Local Ecology
If the surface is base rock it may mean lower hub height hence lower structure cost. If trees or grass or
vegetation are present, all of which tend to destructure the wind, the higher hub heights will be needed
resulting in larges system costs that the bare ground case.
8. Distance to road or railways:
This is another factor the system engineer must consider for heavy machinery, structure, materials,
blades and other apparatus will have to be moved into any choosen WECS site.
9. Nearness of site to local centre/users:
This obvious criterion minimizes transmission line length and hence losses and cost. After applying all
the previous string criteria, hopefully as one narrows the proposed WECS sites to one or two they would
be relatively near to the user of the generated electric energy.
10. Nature of ground:
Ground condition should be such that the foundation for a WECS are secured. Ground surface should be
stable. Erosion problem should not be there, as it could possibly later wash out the foundation of a
WECS, destroying the whole system.
11. Favourable land cost:
Land cost should be favourable as this along with other siting costs, enters into the total WECS system
cost.

CLASSIFICATION OF WIND TURBINES

1.HAWT (Horizontal Axis Wind Turbine)

i)Single blade d

ii)Double bladed

iii)Triple bladed

iv)Multi bladed

2. VAWT (Vertical Axis Wind Turbine

I) Savonious

ii) Darrieus

iii) H-Rotor

iv) Gyro mill

v) Magnus

vi) vortex

HORIZONTAL AXIS WIND TURBINE (HAWT)

What is Horizontal Axis Wind Turbine?

At present, the most commonly used wind turbine is HAWT or Horizontal Axis Wind
Turbine. These turbines use airfoils (aerodynamic blades) which are connected to a rotor by
positioning in upwind or downwind.

These are available either in two-bladed or three-bladed and operate at high speed.

Current horizontal axis wind turbines utilize the aerodynamic lift force to rotate every rotor
blade similar to an airplane flies.

The pressure difference which is formed between the top & bottom faces of the blade
generates a force in the top direction of the blade.

Horizontal Axis Wind Turbine Construction and Working

The construction of a horizontal axis wind turbine can be done with different components.
So the horizontal axis wind turbine components mainly include foundation,
nacelle, generator, tower, and rotor blades.
Horizontal axis wind turbines include the rotor shaft & electric generator which are
arranged at the top of the tower.
Small wind turbines use a simple wind vane, whereas larger wind turbines use wind sensors
that are connected through an auxiliary motor.
Most wind turbines contain a gearbox, which is used to change the blade rotation from slow
to fast, so used to operate an electric generator.
Foundation

For any wind turbine, the foundation gives support to the tower because the wind
turbine includes different parts which weight in tonnes.

Tower:A tower is used to give support to the rotor hub and nacelle on the top of the window
turbine. The materials used to make this are concrete, tubular steel, or steel lattice.

While designing this turbine, the height of the tower is very important because wind speed
enhances with height. So taller towers allow these turbines to capture a huge amount of
energy & produce more electricity.

Wind Turbine Blades

These blades are mainly used to remove the kinetic energy (KE) of wind & change it to
mechanical energy.

These types of blades are designed with wood-epoxy or fiberglass-reinforced polyester.

These turbines include a minimum of one and maximum multiple blades depending on the
design.
Most of the horizontal axis wind turbines include three blades that are connected to the rotor
hub. In earlier days, multiple blades based turbines are used as a single blade, two-blade
and three blades for grinding & pumping water, etc.

Nacelle

The nacelle includes different components which are used to operate the wind turbine
efficiently like the gearbox, brakes, controller, low & high-speed shafts & generator.

It is arranged at the top of a tower & a wind vane is arranged on the nacelle.

Hub

A rotor hub is used to connect a shaft and rotor blade of the wind turbine. The hub includes
blade bearings, bolts, internals & a pitch system.

These are designed with cast iron, welded sheet steel & forged steel. These are available
in two types like Hinge-less hub & Teetering hub.

Gear Box

In wind turbines, a gearbox is used to change high toque power with low-speed which is
received from a rotor blade to low torque power with high speed.

This power is used for the generator. The gearbox is connected in between the generator
and main shaft for enhancing rotational speeds from 30 – 60 rpm to 1000 – 1800 rpm.

Gearboxes are made with different materials like superior quality alloys, aluminum cast iron,
stainless steel, etc. In wind turbines, there are three types of gearboxes are used like
Planetary, Helical, and Worm.

Generator

The rotating mechanical energy of the gearbox is given to the generator through the shaft. It
works on ‘Faraday’s law of ELECTROMAGNETIC INDUCTION principle. So it changes the
energy from mechanical to electrical.

Horizontal Axis Wind Turbine Working

 Once the wind blows, a wind turbine changes the kinetic energy from the motion of the wind
into mechanical through the revolution of the rotor.

After that, this converted energy can be transmitted through the shaft & the gear train
toward the generator. Further, this generator converts the energy from mechanical to
electrical to generate electricity.

The wind flows on both faces of the airfoil-shaped blade although flows faster on the upper
face of the airfoil to create a low-pressure region on the airfoil.

The pressure difference between both the top & bottom surfaces results within the
aerodynamic lift.

As the blades of a wind turbine are constrained to move in a plane with the hub as the
center, the lift force causes rotation about the hub. In addition to the lift force, a drag force
perpendicular to the lift force prevents rotor rotation.

The horizontal axis wind turbine design mainly includes a high lift to drag ratio, especially for
the blades.

So this ratio can change through the blade’s length to optimize the output energy for the
wind turbine at different speeds of wind. The generator & rotor shaft are arranged within the
box at the top of the array.

Advantages and Disadvantages

The advantages of a horizontal axis wind turbine include the following.

 It includes high output power as compared to the vertical wind turbine.
 A tall tower gets stronger winds once the wind shear alters.
 High efficiency.
 It is not expensive as compared to vertical type turbine.
 It has high reliability.
 It has a high rate of capacity.
 Its rotational speed is high.
 It is more consistent.
 These turbines are self-starting.
 In this turbine, the vanes are located one face of the turbine center of gravity, which
improves stability.
 It can bend the blades so that the turbine blades have the best attack angle.
 The blade can also tilt the rotor during a storm to reduce damage

The disadvantages of horizontal axis wind turbine include the following.

 These are available in large size.
 Weight is high.
 We cannot move easily.
 Installation is difficult.
 High noise.
 To design this wind turbine, large machinery is needed.
 Its maintenance is difficult as compared to other wind turbines.

Applications
The applications of horizontal axis wind turbines include the following.
 These are the most frequently used wind turbines for commercial and industrial purposes
due to their large power output and high efficiency.
 These are mostly used in wind farms
 Horizontal axis wind turbines achieve better power output & higher energy efficiency, so
used in large-scale wind power plants & also for electricity generation.
 In industrial plants, large-scale wind farms, or national projects, these wind turbines are
most frequently seen. So they are the perfect solution for the production of mass
electricity.
Vertical Axis Wind Turbine or VAWT
The Vertical Axis Wind Turbine is a type of wind turbine and it is most frequently used for
residential purposes to provide a renewable energy source to the home. This turbine
includes the rotor shaft and two or three blades where the rotor shaft moves vertically. So,
this turbine movement is related to the spinning of coins on the edge. In this turbine, the
generator is placed at the bottom of the tower whereas the blades are covered around the
shaft.
The vertical axis wind turbine working principle is that, the rotors in the turbine
revolve around a vertical shaft by using vertically oriented blades. So they generate
electricity by using wind power. The wind operates the rotor which is connected to the
generator, so the generator converts the energy from mechanical to electrical. Vertical
axis wind turbine components are blade, shaft, bearing, frame & blade support.
Vertical Axis Wind Turbine Block Diagram
The block diagram of a vertical axis wind turbine is shown below. The output energy
generated from this can be used by any type of load. Here, the automatic lighting system is
used as a load. This block diagram includes a Vertical Axis Wind Turbine (VAWT), gearbox,
generator, battery, LDR circuit and LED.

Vertical Axis Wind Turbine Block Diagram

Vertical Axis Wind Turbine

The type of Vertical Axis Wind Turbine used in this system is savories VAWT.
Gear Box A gearbox in a wind turbine is mainly used to enhance the rotating speed
from a low sped shaft to a high-speed shaft connecting through an electrical
generator.

Gears within the gearbox of a wind turbine are subjected to severe cyclic loading because
of uneven wind loads that are stochastic within the environment.

Generator The generator in the wind turbine converts the energy from mechanical to
electrical. These generators are a bit strange as compared to generators used in electrical
grids.

Rechargeable Battery

The output electric energy generated by the generator will be stored in the rechargeable
battery of the wind turbine.

LDR Circuit

The LDR circuit is used to turn ON/OFF the light.

Vertical Axis Wind Turbine Working

This turbine works once the wind turns the turbine. Here, the savory VAWT is used in
this lighting system. Once this turbine rotates, then the generator will get it as
mechanical input & generate the output as electrical energy.

This turbine is arranged on the dividers of the highway roads. The shape of turbine
wings is curved to get the wind for revolution from the 2-way road where the vehicle
speed will make this turbine turn. Here, wind speed is used in different ways based
on our requirements.

A vertical axis wind turbine is connected to the Gearbox which includes gears. This gearbox
is directly connected to the electric generator shaft.
This turbine will revolve once the wind blows & the gearbox in this system will enhance the
turbine rotations internally & send these rotations to the generator like a mechanical input.

So the generator will generate the output as the electrical energy by using this input so that
this output will be stored within the rechargeable battery.
In this way, electricity is generated and stored in the battery using the vehicle’s speed with
the help of a turbine.
The stored energy is used for the automatic lighting system. The LDR circuit uses a resistor,
LDR (Light Dependent Resistor), transistor, battery, and LED (Light Emitting Diode).

The transistor collector terminal is connected to the LED’s negative terminal whereas
the emitter is connected to the GND.

Here, the resistor terminals are connected directly to the voltage source whereas the
negative is connected to the LDR.

When the LDR circuit is connected directly to the battery, then the LDR will start
detecting the light. So when the intensity of light is decreased then LED will be
activated automatically.

So this LDR circuit is applicable in automatic ON or OFF light systems. When the
light intensity of the Sun is decreased in the dusk then LDR will detect the light &
supply the LED.

Vertical Axis Wind Turbine Types

The vertical axis wind turbines are available in two types like Savonius Wind Turbine &
Darrieus Wind Turbine.

Types of Vertical Axis Wind Turbine

Savonius Wind Turbine

Savonius wind turbine includes the blades which are arranged around the vertical shaft
within a helix form. One of the most significant features of this turbine is the solid wind-
receiving area. These turbines mainly rely on the mechanism of flow resistance to make the
rotors active which means, the dynamic force of the wind against the turbine blades thrust
the rotor into revolution.

Simultaneously, the reverse side of the blades meets an aerodynamic resistance force. This
is like when running or cycling, we experience the airflow coming opposite to us. Because of
this, these turbines can simply turn fast like the wind speed. Please refer to this link to know
more about Savonius Wind Turbine.
 Darrieus Wind Turbine

Darrieus wind turbine name is taken from the French inventor namely; Georges Darrieus. It
is also called an egg-beater. These turbines include curved & long wings where each end of
these wings is connected to the top & base of the rotor shaft.

These types of wind turbines use the aerodynamic force of the lift to revolve. By flowing
around the construction, the wind will create suction on the front face of the wind turbine to
drive the wings to revolve. Like Savonius turbines, these turbines do not experience as
much drag due to the shape of wings. Once the revolution begins, these turbines will go
faster to rotate faster than the speed of the wind. Please refer to this link to know more
about Darrieus Wind Turbine.

Advantages of a vertical axis wind turbine

include the following.
 Safety for manpower.
 Scalability.
 They can generate electricity in any direction of the wind.
 It doesn’t require a strong supporting tower because the gearbox, generator & other
components are arranged on the ground.
 As compared to horizontal axis turbines, these are cheaper to design.
 Installation is easy as compared to other types.
 These are portable so we can simply move from one location to another.
 These are designed with fewer speed blades to reduce the risk to birds & people.
 They work in all weather conditions like variable winds & mountain conditions.
 These are allowable where taller structures are not allowed.
 Its operation is simple so they don’t bother people in residential areas.
 These turbines can be arranged close to the earth so that maintenance, the cost for
construction can be reduced.
 To operate these turbines, we don’t require any mechanisms.
 You can use the wind turbine where tall structures are not allowed.
 These are economical, quiet, efficient & ideal for residential energy sources, particularly
in urban areas.
Disadvantages
The disadvantages of a vertical axis wind turbine include the following.
 As compared to HAWT, the efficiency level will be decreased because of the drag that
happens in the blades when they rotate.
 These are very hard to arrange on towers because they are connected on bases like
buildings or ground.
 The efficiency of rotation is low.
 Lower accessible wind speed.
 Component Wear-down.
 Low efficiency.
 Self-Starting mechanism.
 Some animals or birds may interrupt its rotation because it is arranged in an open area.
 They have high vibration due to the flow of air close to the ground makes the turbulent
flow
 They produce noise pollution
Applications
The applications of a vertical axis wind turbine include the following.
 Used in small wind projects
 Used in residential applications
 These turbines are used to generate power even in not stable weather conditions like
gusty wind & turbulence.

Difference between Horizontal Axis and Vertical Axis Wind Turbines

Basis of Horizontal Axis Wind

Vertical Axis Wind Turbine
Difference Turbine

A horizontal axis wind

A wind turbine is called a
turbine is the one whose
Definition vertical axis wind turbine if its
axis of rotation is
axis of rotation is vertical.
horizontal.

Abbreviated HAWT is the abbreviation VAWT is the abbreviation used

name used for horizontal axis to denote the vertical axis
 wind turbine. wind turbine.

For the horizontal axis wind For the vertical axis wind
Axis of rotation
turbine, the axis of rotation turbine, the axis of rotation of
with respect to
of turbine is parallel to the the turbine is perpendicular to
wind stream
wind stream. the wind stream.

In the horizontal axis wind

Location of In the vertical axis wind
turbine, the electric
electric turbine, the generator is
generator is installed at the
generator installed on the ground.
top of the tower.

In HAWT, the gearbox is In VAWT, the gearbox is

Location of
installed at the top of the installed at the bottom of the
gearbox
turbine tower. turbine.

In the horizontal axis wind The vertical axis wind turbine

turbine, the yaw does not require yaw
Need of yaw
mechanism is required to mechanism because it
mechanism
orient the turbine in the receives wind from all
direction of wind. directions.

Vertical axis wind turbine is

not self-starting, hence a
Horizontal axis wind turbine
Self-starting starting mechanism is required
is self-starting.
to start it from stationary
position.

The design and installation The design and installation of

Design and
of a horizontal axis wind a vertical axis wind turbine is
installation
turbine is complex. comparatively simple.

Horizontal axis wind turbine Vertical axis wind turbine

Operation space
requires large space for requires small space for
of blades
blade's operation. blade's operation.

The operation of vertical axis

The operation of horizontal
wind turbine is independent of
Dependency on axis wind turbine is
the wind direction because it
wind direction dependent on wind
receives wind from all
direction.
directions.

The vertical axis wind turbine

The height of the horizontal
Height from is installed at comparatively
axis wind turbine from
ground smaller distance from the
ground is large.
ground.

In case of horizontal axis

There is no need of nacelle in
wind turbines, a heavy
Need of nacelle case of vertical axis wind
nacelle is installed at the
turbines.
top of the tower.
 Horizontal axis wind turbine
Vertical axis wind turbine has
Power coefficient has a high power
a low power coefficient.
coefficient.

Vertical axis wind turbine has

Tip speed ratio Horizontal axis wind turbine
considerably low tip speed
(TSR) has high tip speed ratio.
ratio.

Vertical axis wind turbines

The operation of horizontal
Noise produced produce comparatively less
axis wind turbine is noisy.
noise.

The ideal efficiency of The ideal efficiency of vertical

Efficiency horizontal axis wind turbine axis wind turbine is usually
is around 50% to 60 %. more than 70%.

Horizontal axis wind

Vertical axis wind turbines are
turbines are more
less expensive because their
Cost expensive due their
design and installation is quite
complex design and
simple.
installation.