DESIGN AND FABRICATION OF VERTICAL AXIS

WIND TURBINE

A project report submitted at

Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal

in partial fulfillment of the degree

Bachelor of Engineering

in

Mechanical Engineering

Submitted by

Harshit Singh (0827ME101021)

Punit Purohit (0827ME101038)

Rohit Nayek (0827ME101044) Saket Sharma (0827ME101047)

Shreyans Gangwal (0827ME101054)

Mechanical Engineering Department

Acropolis Institute of Technology and Research, Indore

2013-2014

CERTIFICATE

This is to certify that Harshit Singh (0827ME101021), Punit Purohit (0827ME101038), Rohit

Nayek (0827ME101044), Saket Sharma (0827ME101047), Shreyans Gangwal (0827ME101054)

have completed their project work, titled “DESIGN AND FABRICATION OF VERTICAL

AXIS WIND TURBINE” as per the syllabus and have submitted a satisfactory report as a

partial fulfillment towards the degree of Bachelor of Engineering in Mechanical Engineering

from Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal.

Prof. Himanshu Bhiwapurkar

Project Guide

Prof. Prashant Geete

Project Coordinator

Prof. Tapan Jain

Head of Department

______________ _ _______________

Internal Examiner External Examiner

I

ACKNOWLEDGEMENT

I am thankful to our technical university RGPV, Bhopal that they have given me chance to

convert my theoretical knowledge into the practical skills through this project.

Any work of this magnitude requires input, efforts and encouragement of people from all sides

in compiling this project. I have been fortunate enough to get active and kind co-operation from

many people without my endeavors wouldn’t have been a success.

The project work has been made successful by the cumbersome effort of the faculties.

I would like to express my deep gratitude to my project guide Prof. Himanshu

under whose valuable guidance I was able to complete my project smoothly.

I am thankful to our Head of Mechanical Engg. Department Prof. Tapan Jain for encouraging me

regularly and providing me each and every facility.

Lastly, I am thankful to each and every person involved directly or indirectly in the project work.

Harshit Singh (0827ME101020)

Punit Purohit (0827ME101034)

Rohit Nayek (0827ME101044)

Saket Sharma (0827ME101047)

Shreyans Gangwal (0827ME101020)

II

ABSTRACT

We know that there is enough wind globally to satisfy much, or even most, of humanity's energy

requirements – if it could be harvested effectively and on a large scale. If the efficiency of a wind

turbine is increased, then more power can be generated thus decreasing the need for expensive

power generators that cause pollution. Vertical axis wind turbines (VAWTs), which may be as

efficient as current horizontal axis systems, might be practical, simpler and significantly cheaper

to build maintain than horizontal axis wind turbines (HAWTs).

Savonius wind turbine also have other inherent advantages, such as they are always facing the

wind, which might make them a significant player in our quest for cheaper, cleaner renewable

sources of electricity.

VAWTs might even critical in mitigating grid interconnect stability and reliability issue currently

facing electricity producers and suppliers. Additionally, cheap VAWT’s may provide an

alternative to the rain forest destruction for the growing of bio-fuel crops.

Vertical-axis wind turbines (VAWTs) are a type of wind turbine where the main rotor shaft is set

vertically. Among the advantages of this arrangement are that generators and gearboxes can be

placed close to the ground, and that VAWTs do not need to be pointed into the wind.

Major drawbacks for the early designs (Savonius, Darrieus, and cycloturbine) included the

pulsatory torque that can be produced during each revolution and the huge bending moments on

the blades. Some geographic features such as mountains also have an influence upon wind.

Mountains can create mountain breezes at night, because of the cooler air flowing down the

mountain and being heated by the warmer valley air causing convection current.

In this project we attempt to design and fabricate a Savonius Vertical Axis Wind Turbine with

the help of various interfaces software Catia V5R16, Autodesk Simulation CFD 2014.

III

CONTENTS

CHAPTER 1

INTRODUCTION………………………………………………………………………………...1

1.1 BACKGROUND OF THE VAWT…………………………………………………………...3

1.2 SAVONIUS WIND TURBINE……………………………………………………………….4

1.3 PRINCIPLE OF OPERATION……………………………………………………………….5

1.4 CHARACTERISTICS OF VAWT……………………………………………………………6

1.5 REQUIRMENT OF PLACING……………………………………………………………….6

CHAPTER 2

LITERATURE REVIEW…………………………………………………………………………8

CHAPTER 3

PROBLEM DEFINATION……………………………………………………………………...11

CHAPTER 4

METHODOLGY………………………………………………………………………………...13

4.1 DESIGN AND ANALYSIS…………………………………………………………………14

4.2 CALCULATIONS…………………………………………………………………………...17

CHAPTER 5

EXPERIMENTATION AND RESULTS………………………………………………………..24

CHAPTER 6

CONCLUSION AND FUTURE SCOPE………………………………………………………..28

IV

List of Figures

Figure 4.1 : Wind speed data……………………………………………………….15

Figure 4.2 : Direction wise wind data……….……………………………………...16

Figure 4.3 : Various view of cad model of single blade……………………………18

Figure 4.4 : Various cad views of Coupled Blades…………………………………19

Figure 4.5 : Isometric view of complete assembly…………………………………19

Figure 4.6 : Various views of complete assembly………………………………….20

Figure 4.7 : Vector representation of CFD Result………………………………….21

Figure 4.8 : Shaded and vector representation of CFD Result……………………..21

Figure 4.9 : Complete view of CFD Result Screen………………………………...21

Figure 4.10 : Variation of wind speed along direction of wind…………………...…22

Figure 4.11 : Variation of wind speed perpendicular to the direction of wind………22

Figure 4.12 : Pressure change along direction of wind………………………………23

Figure 4.13 : Pressure change perpendicular direction of wind……………………...23

Figure 5.1 : View of final model……………………………………………………25

Figure 5.2 : View of Dynamo Assembly…………………………………………...25

Figure 5.3 : Velocity of air vs. power developed…………………………………...26

Figure 5.4 : Air velocity vs. efficiency……………………………………………..27

V

LIST OF TABLES

Table 4.1 : Value of cut-in speed, rated wind speed, and cut-out speed……………15

Table 4.2 : Summary of design parameters………………………………………...17

Table 4.3 : Summaries of rotor blade design……………………………………….18

Table 5.1 : Experimentation Result………………………………………………..26

VI

1

CHAPTER 1

INTRODUCTION

2

INTRODUCTION

If the efficiency of a wind turbine is increased, then more power can be generated thus

decreasing the need for expensive power generators that cause pollution. This would also reduce

the cost of power for the common people. The wind is literally there for the taking and doesn't

cost any money. Power can be generated and stored by a wind turbine with little or no pollution.

If the efficiency of the common wind turbine is improved and widespread, the common people

can cut back on their power costs immensely.

Ever since the Seventh Century people have been utilizing the wind to make their lives easier.

The whole concept of windmills originated in Persia. The Persians originally used the wind to

irrigate farm land, crush grain and milling. This is probably where the term windmill came from.

Since the widespread use of windmills in Europe, during the Twelfth Century, some areas such

as the Netherlands have prospered from creating vast wind farms. The towers without guy wires

are called freestanding towers. Something to take into consideration about a tower is that it must

support the weight of the windmill along with the weight of the tower.

The first windmills, however, were not very reliable or energy efficient. Only half the sail

rotation was utilized. They were usually slow and had a low tip speed ratio but were useful for

torque.

Since its creation, man has constantly tried to improve the windmill. As a result, over the years,

the number of blades on windmills has decreased. Most modern windmills have 5-6 blades while

past windmills have had 4~8 blades. Past windmill also had to be manually directed into the

wind, while modern windmills can be automatically turned into the wind. The sail design and

materials used to create them have also changed over the years.

In most cases the altitude of the rotor is directly proportional to its efficiency. As a matter of fact,

a modern wind turbine should be at least twenty feet above and three hundred feet away from an

obstruction, though it is even more ideal for it to be thirty feet above and five hundred feet away

from any obstruction.

Different locations have various wind speeds. Some places, such as the British Isles, have few

inhabitants because of high wind speeds, yet they are ideal for wind generation. Did you know

that the world's largest wind farm is located in California, and the total wind power generated

there exceeds 1,400 megawatts of electricity? (A typical nuclear power plant generates 1,000

megawatts.)

3

Some geographic features such as mountains also have an influence upon wind. Mountains can

create mountain breezes at night, because of the cooler air flowing down the mountain and being

heated by the warmer valley air causing a convection current. Valleys are affected in much the

same way. In the daytime, the cooler air is above the valleys and the hot air is above the

mountains. The hot air above the mountain rises above the valleys and cools, thus creating a

convection current in the opposite direction and creating a valley wind. The oceans create

convection currents, as well as they mountains or valleys. In the day, the hotter air is above the

same and the cooler air is above the ocean. The air heats up over the sand and rises above the

ocean and then cools, creating the convection current. At night, the cooler air is above the sand

and the warmer air is above the ocean, so the air heats up over the ocean and cools over the sand.

As you can clearly see, the time of day also affects the wind.

We know that for windmills to operate there must be wind, but how do they work? Actually

there are two types of windmills -- the horizontal axis windmills and the vertical axis windmills.

-The horizontal axis windmills have a horizontal rotor much like the classic Dutch four-arm

windmill. The horizontal axis windmills primarily rely on lift from the wind. As stated in

Bernoulli's Principle, "a fluid will travel from an area of higher pressure to an area of lower

pressure." It also states, "as the velocity of a fluid increases, its density decreases." Based upon

this principle, horizontal axis windmill blades have been designed much like the wings of an

airplane, with a curved top. This design increases the velocity of the air on top of the blade thus

decreasing its density and causing the air on the bottom of the blade to go towards the top ...

creating lift. The blades are angled on the axis as to utilize the lift in the rotation. The blades on

modern wind turbines are designed for maximum lift and minimal drag.

1.1 BACKGROUND

Vertical axis windmills, such as the Savonius (built in 1930) use drag instead of lift. Drag is

resistance to the wind, like a brick wall. The blades on vertical axis windmills are designed to

give resistance to the wind and are as a result pushed by the wind. Windmills, both vertical and

horizontal axis, have many uses. Some of them are: hydraulic pump, motor, air pump, oil pump,

churning, creating friction, heat director, electric generator, Freon pump, and can also be used as

a centrifugal pump.

There are many types of windmills, such as: the tower mill, sock mill, sail windmill, water pump,

spring mill, multi-blade, Darrieus, savonis, cyclo-turbine, and the classic four-arm windmill. All

of the above windmills have their advantages. Some windmills, like the sail windmill, are

relatively slow moving, have a low tip speed ratio and are not very energy efficient compared to

the cyclo-turbine, but are much cheaper and money is the great equalizer.

4

There have been many improvements to the windmill over the years. Windmills have been

equipped with air breaks, to control speed in strong winds. Some vertical axis windmills have

even been equipped with hinged blades to avoid the stresses at high wind speeds. Some

windmills, like the cyclo-turbine, have been equipped with a vane that senses wind direction and

causes the rotor to rotate into the wind. Wind turbine generators have been equipped with

gearboxes to control [shaft] speeds. However, Europeans had been experimenting with curved

blades on vertical wind turbines for many decades before this. Wind turbines have also been

equipped with generators which convert shaft power into electrical power. Many of the sails on

windmills have also been replaced with propeller-like airfoils. Some windmills can also stall in

the wind to control wind speed. But above all of these improvements, the most important

improvement to the windmill was made in 1745 when the fantail was invented. The fantail

automatically rotates the sails into the wind.

Most wind turbines start to generate power at 11 m/s and shut down at speeds near 32m/s.

Another variable of the windmill's efficiency is its swept area. The swept area of a disk--shaped

wind wheel is calculated as: Area equals pi times diameter squared divided by four (pi equals

3.14).

Another variable in the productivity of a windmill is the wind speed. The wind speed is

measured by an anemometer. Savonius and other vertical-axis machines are good at pumping

water and other high torque, low rpm applications and are not usually connected to electric

power grids.

Another necessity for a windmill is the tower. There are many types of towers. Some towers

have guy wire to support them and others don't. The towers without guy wires are called

freestanding towers. Something to take into consideration about a tower is that it must support

the weight of the windmill along with the weight of the tower. Towers are also subject to drag.

Scientists estimate that, by the 21st Century, ten percent of the world's electricity will come from

windmills.

1.2 SAVONIUS WIND TURBINE

Savonius wind turbines are a type of vertical-axis wind turbine (VAWT), used for converting the

force of the wind into torque on a rotating shaft. The turbine consists of a number of aerofoils,

usually—but not always—vertically mounted on a rotating shaft or framework, either ground

stationed or tethered in airborne systems.

5

The Savonius wind turbine was invented by the Finnish engineer Sigurd Johannes Savonius in

1922. However, Europeans had been experimenting with curved blades on vertical wind turbines

for many decades before this. The earliest mention is by the Italian Bishop of Czanad, who was

also an engineer. He wrote in his 1616 book Machinae novae about several vertical axis wind

turbines with curved or V-shaped blades. None of his or any other earlier examples reached the

state of development made by Savonius. In his Finnish biography there is mention of his

intention to develop a turbine-type similar to the Flettner-type, but autorotationary. He

experimented with his rotor on small rowing vessels on lakes in his country. The Savonius

turbine is one of the simplest turbines.

Savonius turbines are used whenever cost or reliability is much more important than efficiency.

Most anemometers are Savonius turbines for this reason, as efficiency is irrelevant to the

application of measuring wind speed. Much larger Savonius turbines have been used to

generate electric power on deep-water buoys, which need small amounts of power and get very

little maintenance. Design is simplified because, unlike with horizontal axis wind turbines

(HAWTs), no pointing mechanism is required to allow for shifting wind direction and the turbine

is self-starting. Savonius and other vertical-axis machines are good at pumping water and other

high torque, low rpm applications and are not usually connected to electric power grids. They

can sometimes have long helical scoops, to give smooth torque.

The most ubiquitous application of the Savonius wind turbine is the Flettner Ventilator, which is

commonly seen on the roofs of vans and buses and is used as a cooling device. The ventilator

was developed by the German aircraft engineer Anton Flettner in the 1920s. It uses the Savonius

wind turbine to drive an extractor fan. The vents are still manufactured in the UK by Flettner

Ventilator Limited.

Small Savonius wind turbines are sometimes seen used as advertising signs where the rotation

helps to draw attention to the item advertised. They sometimes feature a simple two-

frame animation.

1.3 PRINCIPLE OPERATION

Aerodynamically, it is a drag-type device, consisting of two or three scoops. Looking down on

the rotor from above, a two-scoop machine would look like an "S" shape in cross section.

Because of the curvature, the scoops experience less drag when moving against the wind than

when moving with the wind. The differential drag causes the Savonius turbine to spin. Because

they are drag-type devices, Savonius turbines extract much less of the wind's power than other

6

similarly-sized lift-type turbines. Much of the swept area of a Savonius rotor may be near the

ground, if it has a small mount without an extended post, making the overall energy extraction

less effective due to the lower wind speeds found at lower heights.

1.4 CHARACTERISTICS OF VAWT

Wind Speed

This is very important to the productivity of a windmill. The wind turbine only generates power

with the wind. The wind rotates the axis (horizontal or vertical) and causes the shaft on the

generator to sweep past the magnetic coils creating an electric current.

Blade Length

This is important because the length of the blade is directly proportional to the swept area.

Larger blades have a greater swept area and thus catch more wind with each revolution. Because

of this, they may also have more torque.

Base Height

The height of the base affects the windmill immensely. The higher a windmill is, the more

productive it will be due to the fact that as the altitude increases so does the winds speed.

Base Design

Some base is stronger than others. Base is important in the construction of the windmill because

not only do they have to support the windmill, but they must also be subject to their own weight

and the drag of the wind. If a weak tower is subject to these elements, then it will surely collapse.

Therefore, the base must be identical so as to insure a fair comparison.

1.5 REQUIREMENT OF PLACEMENT

Site Selection considerations The power available in the wind increases rapidly with the speed; hence wind energy conversion

machines should be located preferable in areas where the winds are strong & persistent. The

following point should be considered while selecting site for Wind Energy Conversion System

(WECS).

High annual average wind speed The wind velocity is the critical parameter. The power in the wind P

w, through a given X section

area for a uniform wind Velocity is

Pw

= KV3

(K is constant)

7

It is evident, because of the cubic dependence on wind velocity that small increases in V

markedly affect the power in the wind

e.g. doubling V, increases Pw

by a factor of 8.

Availability of wind V(t)

curve at the proposed site

This important curve determines the maximum energy in the wind and hence is the principle

initially controlling factor in predicting the electrical o/p and hence revenue return of the WECS

machines, it is desirable to have average wind speed V such that

V≥12-16 km/hr i.e. (3.5 – 4.5 m/sec).

Wind structures at the proposed site Wind especially near the ground is turbulent and gusty, & changes rapidly indirection and in

velocity. This departure from homogeneous flow is collectively referred to as ―the structure of

the wind‖.

Altitude of the proposed site If affects the air density and thus the power in the wind & hence the useful WECS electric power

o/p. The winds tends to have higher velocities at higher altitudes.

Local Ecology If the surface is bare rock it may mean lower hub heights hence lower structure cost, if trees or

grass or ventation are present. All of which tends to destructure the wind.

Nature of ground Ground condition should be such that the foundations for WECs are secured, ground surface

should be stable.

Favorable land cost

Land cost should be favorable as this along with other sitting costs, enters into the total WECS

system cost.

8

CHAPTER 2

LITERATURE REVIEW

9

The Source of Winds

In a macro-meteorological sense, winds are movements of air masses in the atmosphere mainly

originated by temperature differences. The temperature gradients are due to uneven solar heating.

In fact, the equatorial region is more irradiated than the polar ones. Consequently, the warmer

and lighter air of the equatorial region rises to the outer layers of the atmosphere and moves

towards the poles, being replaced at the lower layers by a return flow of cooler air coming from

the Polar Regions. This air circulation is also affected by the Coriolis forces associated with the

rotation of the Earth. In fact, these forces deflect the upper flow towards the east and the lower

flow towards the west. Actually, the effects of differential heating dwindle for latitudes greater

than 30oN and 30

oS, where westerly winds predominate due to the rotation of the Earth. These

large-scale air flows that take place in all the atmosphere constitute the geotropic winds.

The lower layer of the atmosphere is known as surface layer and extends to a height of 100 m. In

this layer, winds are delayed by frictional forces and obstacles altering not only their speed but

also their direction. This is the origin of turbulent flows, which cause wind speed variations over

a wide range of amplitudes and frequencies. Additionally, the presence of seas and large lakes

causes air masses circulation similar in nature to the geotropic winds. All these air movements

are called local winds.

The Power in the Wind

The power in the wind can be computed by using the concepts of kinetics. The wind mill works

on the principle of converting kinetic energy of the wind to mechanical energy. The kinetic

energy of any particle is equal to one half its mass times the square of its velocity,

Kinetic Energy =½ mv2

.

Amount of Air passing is given by

m = ρ AV …………………..(1)

Where

m = mass of air transversing

A=area swept by the rotating blades of wind mill type generator

ρ = Density of air

V= velocity of air

Substituting this value of the mass in expression of K.E.

= ½ ρ AV.V2

watts

= ½ ρ AV3

watts ………………….. (2)

Second equation tells us that the power available is proportional to air density (1.225 kg/m3

) & is

proportional to the intercept area. Since the area is normally circular of diameter D in horizontal

axis aero turbines, then,

10

A = πD2

(Sq. m)

4

Put this quantity in equation second then

Available wind power Pa = ρ π D2

V3

watt.

8

11

CHAPTER 3

PROBLEM DEFINATION

12

The development of vertical axis wind turbines can be traced back to 300 – 900 A.D. where

these were utilized for grain grinding and water pumping processes. VAWTs offer a number of

advantages over traditional horizontal-axis wind turbines (HAWTs). They can be packed closer

together in wind farms, allowing more in a given space. They are quiet, Omni-directional, and

they produce lower forces on the support structure. They do not require as much wind to

generate power, thus allowing them to be closer to the ground where wind speed is lower. By

being closer to the ground they are easily maintained and can be installed on chimneys and

similar tall structures.

Research at Caltech has also shown that carefully designing wind farms using VAWTs can result

in power output ten times as great as a HAWT wind farm the same size.

VAWTs are much quieter than HAWTs, with dB levels at ground level ten meters from the

tower measured at around 95 dB for a HAWT versus 38dB for a VAWT. This is due to several

factors, starting with the much lower tip speed of VAWTs.

However most of the above claims are considered debatable by people with experience of wind

engineering such as Paul Gipe, Mick Sagrillo and most of the active installers. There is very little

history of successful VAWT operation, despite their long history.

Thus in this project we aim to carefully design, analyze, fabricate and calculate the performance

of a Vertical axis wind turbine to determine problems with these turbines and attempt to suggest

some solution to the determined problem.

13

CHAPTER 4

METHODOLOGY

14

4.1 Design Methodology

Wind power, Pw is defined as the multiplication of mass flow rate, ρAV and the kinetic energy

per unit mass, ½ V2 (Musgrove, 2010). The wind power is denoted by the equation of:

Pw = ½ ρAV3 (1)

Hayashi, et al. (2004) found that the swept area for Savonius Wind Turbine is calculated by

multiplication of rotor diameter, D and the rotor height, H. The larger the swept area, the larger

the power generated.

A = D.H (2)

The wind power in Equation (3) represents the ideal power of a wind turbine, as in case of no

aerodynamic or other losses during the energy conversion processes. However, as stated by

Manwell et al., (2009) there is not possible for all energy being converted into useful energy. The

ideal efficiency of a wind turbine is known as Betz limit. According to the Betz limit, as

supported by Musgrove (2010) there is at most only 59.3 % of the wind power can be converted

into useful power. Some of the energy may lose in gearbox, bearings, generator, transmission

and others (Jain, 2011). The maximum power coefficient, Cp for Savonius rotor is 0.30. Hence,

the Cp value used in this project is 0.30 and the power output, P with considering the power

efficiency is:

P = 0.15 ρAV3 (3)

4.2 Parameters

Wind speed is the major element that affects the power output. The three wind speed parameters

involve in this project is cut-in speed, rated wind speed and cut-out speed. Jain (2011) stated that

the three wind speed parameters related to the power performance are as follow:

Vcut-in = 0.5 Vavg (4)

VRated = 1.5 Vavg (5)

Vcut-out = 3.0 Vavg (6)

15

All these parameters depend on the value of average wind speed. The average wind speed, Vavg

was found by gathering the data of wind speed from march 2013 to feburary 2014 from

windfinder.com website and the average wind speed was found to be 3m/s in Indore. Table 1

summarizes the value of these three wind speed parameters.

Table 4.1: Value of cut-in speed, rated wind speed, and cut-out speed.

Wind Speed Parameter Equation Calculation

Cut-in speed, Vcut-in Vcut-in = 0.5 Vavg 1.5 m/s

Rated wind speed, VRated VRated = 1.5 Vavg 4.5 m/s

Cut-out speed, Vcut-out Vcut-out = 3 Vavg 9 m/s

4.3 Selection

Aspect ratio is a crucial criterion to evaluate the aerodynamic performance of Savonius rotor.

Johnson (1998) suggests the Savonius rotor is designed with rotor height twice of rotor diameter

and this lead to better stability with proper efficiencies.

Figure 4.1: Wind Speed data of Indore

16

Aspect ratio is a crucial criterion to evaluate the aerodynamic performance of Savonius rotor.

Johnson (1998) suggests the Savonius rotor is designed with rotor height twice of rotor diameter

and this lead to better stability with proper efficiencies.

AR = H/D (7)

Tip speed ratio, λ is defined as the ratio of the linear speed of rotor blade ω.R to the undisturbed

wind speed, V (Solanki, 2009). ω is the angular velocity and R represent the radius revolving

part of the turbine. The maximum tip speed ratio that Savonius rotor can reach is 1. Manwell et

al., (2009) write that high tip speed ratio improves the performance of wind turbine and this

could be obtained by increasing the rotational rate of the rotor.

λ = ω.R /V (8)

Figure 4.2: Direction wise wind data

17

According to Manwell et al., (2009) solidity is related to tip speed ratio. A high tip speed ratio

will result in a low solidity. Musgrove (2010) defines solidity as the ratio of blade area to the

turbine rotor swept area. For VAWT, the solidity is defined as

σ = nd /R (9)

Where n is the number of blades, d is the chord length or can be defined as the diameter of each

half cylinder, and R is radius of wind turbine. Many researchers have proved that the higher the

number of blades, the higher the performance of most wind turbine. However, Saha et al., (2008)

and Zhao et al., (2009) found that the two-bladed Savonius rotor has higher performance than

three-bladed Savonius rotor. Referring to Saha then the two-blade rotor has been chosen for this

project. Table 3.2 shows the design parameters used in this research.

Table 4.2: Summary of design parameters.

Parameter Value

Power Available in the wind 17 W

Swept Area 0.31 m2

Rated Wind Speed 4.5 m/s

Aspect Ratio 1.2

Tip Speed Ratio 1.0

Solidity 2.114

Diameter – Height 0.51 m – 0.61 m

Number of Blade 2

4.4 Design specification.

The design of the Savonius rotor blade is shown in Figure 2, while Table 3 shown the detail

dimension of the Savonius rotor blade. The material proposed for the Savonius rotor blade in this

project is Aluminium.

18

Table 4.3: Summaries of rotor blade design and the material properties of Aluminum.

Parameter Value

Swept Area, A 0.31 m2

Rotor Diameter, D 510 mm

Rotor Height, H 610 mm

Chord Length, d 260 mm

Overlap Distance, e 101.6 mm

Blade Thickness, t 1 mm

Density 2700kg/m3

Young’s modulus 0.69 GPa

Poisson’s ratio 0.33

Tensile yield strength 276MPa

Analysis

CAD model of Savonius blade and assembly was done using Caria v5 for the purpose of

Computational fluid Dynamics analysis and to simplify fabrication process

Below the figure shows various views of the CAD model of Savonius blades and the overall

assembly

19

The above picture is a clip of Savonius blade taken from Catia v5 software. The blade were

modeled in catia v5 to exact dimension as produced above in design to visualize actual size of

the model and for proper assembly.

The next Figure below shows the combine geometry of the blades after combining the two

blades this model was used for CFD analysis of the model to produce reliable results as the

models were of actual size. Complete assembly was modeled in Catia V5 software as shown in

pictures below.

Figure4.4: Various cad views of Coupled Blades

Figure4.5: Isometric view of complete assembly

20

Computational fluid dynamics

Air flow around the turbine was simulated using Autodesk Simulation CFD 2014 this was done

to understand the flow around the turbine and understand the variation in wind speed in various

regions around.

For visualization of flow and Variation in wind speed, the inlet air velocity was set at 5m/s

second and static zero gauge pressure. The flow pattern and variation as observed are shown

below in the following pictures

The flow pattern observed were as expected wind deep blue regions near the blades surface

shows the boundary layer formation and the bend of air around the blades and through the

overlap region. The contour plot analysis gives an idea about the flow physics of a wind rotor.

The contour plot analysis gives an idea about the flow physics of a wind rotor and its power

production mechanism. In the present study, relative velocity magnitude (velocity of the rotor

relative to wind) and static pressure contours of the Savonius rotor are analysed. The contour

plots are obtained for tip speed ratio at which power coefficient of the rotor is the highest for

each overlap condition. Picture show the relative velocity contours of the two-bucket Savonius

rotor for overlap conditions of 12.37%, The relative velocity magnitude contours show that there

is a decrease of relative velocity magnitude from the upstream side to the downstream side of the

rotor. Fig. 6(a) for 12.37% overlap shows that relative velocity decreases from upstream to

downstream across the rotor.

Figure 4.6: Various views of complete assembly

21

Figure 4.7: Vector representation of

CFD Result

Figure 4.8: Shaded and vector representation

of CFD Result

Figure 4.9: Complete view of CFD Result Screen

22

Figure 4.10: Variation of wind speed along the direction of wind through the Savonius

blade

Figure 4.12: Pressure change along direction of wind

23

Figure 4.11: Variation of wind speed perpendicular to the direction of

wind

Figure 4.13:Pressure change perpendicular direction of wind

24

CHAPTER 5

EXPERIMENTATION AND RESULT.

25

Model

The model of the Savonius turbine was made in college workshop. Pictures of model are shown

below. To get electrical power output a DC motor was used inversely with Savonius input

connected to motor shaft and electrical output taken from terminals of the motor. This energy

was used to charge battery and thus making the model a reliable source of continuous energy.

Figure 5.1: View of final model

Figure 5.2: view of Dynamo Assembly

26

Observations.

To test the model at different speeds an external fan was used to generate the desired speed of

wind and then electrical power generated was determined using a multi-meter. From thus

accumulated data the efficiency of the turbine was determined.

RPM Velocity of air in m/s

Power available power (watts) VI (watts) Efficiency

46 0.1175 0.069 0.0103 14

54 0.877 0.124 0.018 15

67 1.036 0.209 0.032 15.5

75 1.19625 0.3245 0.051 16

83 1.355 0.466 0.0745 16

98 1.595 0.776 0.124 16.9

118 1.915 1.941 0.226 17

163 2.553 3.143 0.55 17.5

188 3.05 5.17 0.939 18.18

223 3.58 8.699 1.54 17.8

0

0.5

1

1.5

2

2.5

3

3.5

4

VI 0.0103 0.018 0.032 0.051 0.0745 0.124 0.226 0.55 0.939

Ve

loci

ty o

f ai

r in

m/s

Figure 5.3Velocity of air vs Power developed

Table 5.1 Experimentation Result

27

Efficiency of the model was variable with wind speed with maximum of 18.18% in the region of

wind speed produced by the fan.

02468

101214161820

Effi

cie

ncy

in %

Figure 5.4: Air velocity vs Efficiency

28

CHAPTER 6

CONCLUSION AND FUTURE SCOPE

29

Conclusion

The efficiency of the fabricated wind turbine was found to be around 18 percent with variation at

different velocities of the wind. Though the efficiency seems quite low but It can be seen as

usable power generated from nothing. These turbines have a great advantage over Horizontal

axis wind turbine that they can work on low height thus these turbines can be installed on

individual houses for their particular use. The power generated from the turbine can be stored or

used to charge a storage device and then the storage device can be used as a continuous power

source. Having said that there are some limitation of these turbines VAWT blades are rarely at

an optimal angle to the wind or in clean air, so they can never be as efficient as a tripled HAWT

and won’t generate more electricity, HAWTs almost never collapse due to lateral stress, and

VAWTs typically have very asymmetrical front and rear stresses on their bearings, and To

generate the same electricity, VAWTs would have to be as tall as HAWTs, so visual impact will

be virtually identical.

Yet with more and more engineers and researchers working on the design and development of

Vertical axis wind turbine the efficiency can be increased and the usability of these turbines can

be increased.

Future Consideration

Due to the large variations in testing data, additional testing is required. This testing should focus

on the following key areas to improve testing results:

Data Acquisition System– Increase the sampling frequency of the DAQ to allow for a more

accurate reading of the rotational speed of the shaft. Increasing the sample rate will permit the

use of a LED sensor that can count the number of rotations made by the turbine.

Braking Mechanism– The friction brake presented problems in pulse loading. It should be

determined if the use of an eddy current is feasible. Alternatively, a friction brake more suited to

the current testing methods can be acquired and used.

Additional considerations to validate or invalidate this particular design include:

30

Install a small generator– Connect the turbine to a small generator to determine the power

output of the entire system. This particular study focused on the blade performance but the full

concept should include the total system efficiency.

Reliability Testing– Testing of the turbine should be conducted under various weather

conditions to determine the reliability of the turbine. This turbine should be subjected fully

developed and turbulent winds under icing and snowing conditions. The components should also

undergo longer term reliability testing when subjected to Newfoundland’s environment.

31

REFERENCES.

Becker, W. S. ―Wind Turbine Device.‖ US Patent # 7,132,760 B2. Filed (Jul. 29, 2003).

Benesh, A. ―Wind Turbine System Using Twin Savonius-Type Rotors.‖ US Patent #

4,830,570. Filed (Dec. 15, 1987).

Bertony, J. ―Vertical Axis Wind Turbine with Twisted Blade or Auxiliary Blade.‖ US

Patent Application # 2008/0095631 A1. Filed (Oct. 19, 2005).

Cleanfield Energy. V3.5 ―Vertical Axis Wind Turbine System: Product Overview and

Key Benefits‖. Retrieved From:

http://www.cleanfieldenergy.com/site/sub/p_we_overview.php.

Cooper, P. & Kennedy, O. ―Development and Analysis of a Novel Vertical Axis Wind

Turbine‖. University of Wollongong. Filed (March, 2003).

Savonius, S. J. Wind Rotor. US Patent #1,766,765. Filed (Oct. 11, 1928).

Mario Pozner, ―Early history through 1875‖ Retrieved From:

http://telosnet.com/wind/early.html

Mike Bernard, ―Why aren’t vertical-axis wind turbines more popular?‖ Retrieved From:

http://barnardonwind.com/2013/02/23/why-arent-vertical-axis-wind-turbines-more-

popular/

James F. Manwell, Jon G. McGowan, Anthony L. Rogers ―Wind Energy Explained:

Theory, Design and Application‖ December 2009: published by: Wiley.

Ion Paraschivoiu ―Wind Turbine Design: With Emphasis on Darrieus Concept‖, Presses

inter Polytechnique, 2002