SHROUDED WIND TURBINE MOBILE CHARGER
B TechMini Project Report2014Done by1. PRAJITH KS ETALEME0662.
PRANAV AV ETALEME0673. PRAVEEN PR ETALEME0684. PRAVEEN PRADEEP
ETALEME0695. PRAVEEN V PRASAD ETALEME070
Department of Mechanical EngineeringGovernment Engineering
CollegeThrissur-680 009
Government Engineering College, Thrissur Department of
Mechanical Engineering
2014CERTIFICATE Certified that this is a bonafide record of the
Project Work titled SHROUDED WIND TURBINE MOBILE CHARGERDone by 1.
PRAJITH KS ETALEME0662. PRANAV AV ETALEME0673. PRAVEEN PR
ETALEME0684. PRAVEEN PRADEEP ETALEME0695. PRAVEEN V PRASAD
ETALEME070of Third year B Tech Mechanical Engineering in partial
fulfilment of the requirement for the award of Bachelor of
Technology Degree in Mechanical Engineering under the University of
Calicut during the year 2014.
Project Guide Head of the DepartmentProf. Jayee K Varghese Prof.
Varughese Job
Thrissur Date.
ABSTRACT
This project discusses a novel type of energy converter that
uses wind energy to produce electricity. The objective of this
project is to harvest energy from low-speed wind flows, available
while travelling in trains and buses, in order to power and charge
mobile electronic devices like mobile phone. A DC generator and
integrated circuit is used in this project to provide constant
voltage supply required for charging of mobile devices. DC motor is
used as generator in the place of AC generator with a regulator
circuit comprising of different components like Voltage regulator
IC, Charging pin and capacitors for ripple free voltage supply. The
turbine is enclosed in housing instead of more common open
turbines, to utilise the venturi effect to generate maximise power.
Various designs of the housing were modelled and flow analysis was
conducted on each of them in a virtual wind tunnel using simulation
software to determine various parameters such as wind velocity,
pressure and density during the fluid flow through the housing.
Several possible designs of the housing are suggested and best
alternative amongst them is determined. The system is able to
charge the battery when the wind speed exceeds 36 km/hr.This
project could be used as emergency source for charging mobile phone
while travelling in a vehicle when charging outlets are not
available.
Key words: DC generator, charging, venturi effect, voltage
regulator, wind velocity, wind pressure, flow analysis, flow
simulation, pressure, velocity, kinetic energy,
ACKNOWLEDGEMENT
The success and final outcome of this project required a lot of
guidance and assistance from many people and we are extremely
fortunate to have got this all along the completion of our project
work. I would not forget to thank them.I respect and thank our
project guide Prof. Jayee K. Varghese, for providing me with all
the support and guidance I required to complete the project on
time. I am extremely grateful to him for providing such a nice
support and guidance though he had busy schedule managing.I owe my
profound gratitude to our Prof. Abdul Samad, who took keen interest
on our project work and guided us all along, till the completion of
our project work by providing all the necessary information.I would
not forget to remember Mr Kesavan for their unlisted encouragement
and more over for their timely support and guidance till the
completion of our project work.I heartily thank our head of the
department, Prof Varghese Jobs, and our group tutor Prof. Manmohan
CV, for the timely information provided to us during the completion
of this project work.I am thankful to and fortunate enough to get
constant encouragement, support and guidance from all Teaching
staffs of Department of Mechanical Engineering which helped us in
successfully completing our project work. Also, I would like to
extend my sincere regards to all the non-teaching staff of
department of computer science for their timely support.
TABLE OF CONTENTS
1. ABSTRACT2. ACKNOWLEDGMENT3. LIST OF TABLES4. LIST OF
FIGURES5. LIST OF SYMBOLS6. LIST OF SYMBOLS7. CHAPTER 1
INTRODUCTION8. CHAPTER 2 SIMULATION OF WIND FLOW ANALYSIS9. CHAPTER
3PRESSURE, VELOCITY AND DENSITY ANALYSIS10. CHAPTER 4
CONSTRUCTION11. CHAPTER 5 SCOPE AND CONCLUSION12. REFERENCES
LIST OF TABLES
TABLE1: Parameters fixed for simulationTABLE2: Estimated wind
energy harvested by different models
LIST OF FIGURESFigure 1: Cylindrical closed pipe constructed for
analysing the flow Figure 2.a: Cut plot of X component of velocity
of wind through Actual modelFigure 2.b: Cut plot of X component of
velocity of wind through Test model 1Figure 2.c: Cut plot of X
component of velocity of wind through Test model 2Figure 2.d: Cut
plot of X component of velocity of wind through Test model 3Figure
3.a: Cut plot of Total velocity of wind flowing through Actual
modelFigure 3.b: Cut plot of Total velocity of wind flowing through
Test model 1Figure 3.c: Cut plot of Total velocity of wind flowing
through Test model 2Figure 3.d: Cut plot of Total velocity of wind
flowing through Test model 3Figure 4.a: Cut plot of pressure of
wind flowing through actual modelFigure 4.b: Cut plot of pressure
of wind flowing through test model 1Figure 4.c: Cut plot of
pressure of wind flowing through test model 2 Figure 4.d: Cut plot
of pressure of wind flowing through test model 3Figure 5.a: Cut
plot of density of wind flowing through Actual modelFigure 5.b: Cut
plot of density of wind flowing through Test model 1Figure 5.c: Cut
plot of density of wind flowing through Test model 2Figure 5.d: Cut
plot of density of wind flowing through Test model 3Figure 6:
Shrouded wind turbine mobile chargerFigure 7: TurbineFigure8: 20V
DC GeneratorFigure 9: IC 7806Figure 10: Circuit DiagramLIST OF
SYMBOLS
E - E.m.f generated across the coil of generatorEext - E.m.f
required across external circuitEmax - Peak voltage of generator
outputf - Frequency of generator output - Density of air flowing
through the housingV -velocity of flow of the air in throatA -area
of cross section of throat
CHAPTER 1INTRODUCTION
With rapid developments in the technology availability of mobile
electronic devices has only shown a rising trend. This tremendous
increase in usage of these devices has brought up an important
problem of charging these devices on the move. Many times
circumstances arise when we are unable to charge our daily use
gadgets like mobile phones when we have to travel to a different
place. But this problem can be tackled by using energy resources
charging pins powered automobile battery and alternators, using
solar panels or through hand operated dynamo through a combination
of many gears are used for charging mobile phones. But a problem
occurs when there is no sunlight or the light is not in a proper
amount. Also the person might be using a public transport system or
the automobile battery is not in a condition to charge the device.
Also the use of hand operated geared charging unit is very
laborious to use and also not effective for long. In such
circumstances in order to overcome charging limitations,
exploration has been carried out with mobile phone charger based on
wind energy and at present we have come with a solution of
maintaining sustainability of energy stored in the phone battery by
Wind Driven Mobile Battery Charger .This concept utilises wind
generated electrical energy to charge the mobile phones
battery.
1.1 WIND TURBINEAwind turbineis a device that convertskinetic
energyfrom thewind into electrical power. A wind turbine used for
charging batteries may be referred to as awind charger. The result
of over a millennium of windmill development and modern
engineering, today's wind turbines are manufactured in a wide range
of vertical and horizontal axis types. The smallestturbinesare used
for applications such as battery charging for auxiliary power for
boats orcaravansor to power traffic warning signs. Slightly larger
turbines can be used for making small contributions to a domestic
power supply while selling unused power back to the utility
supplier via theelectrical grid. Arrays of large turbines, known
aswind farms, are becoming an increasingly important source
ofrenewable energyand are used by many countries as part of a
strategy to reduce their reliance onfossil fuels.
1.2 TYPES OF WIND TURBINES
1.2.1 HORIZONTAL AXIS WIND TURBINE (HAWT)Horizontal-axis wind
turbines (HAWT) have the mainrotorshaft andelectrical generatorat
the top of a tower, and must be pointed into the wind. Small
turbines are pointed by a simplewind vane, while large turbines
generally use a wind sensor coupled with aservo motor. Most have a
gearbox, which turns the slow rotation of the blades into a quicker
rotation that is more suitable to drive an electrical generator.
1.2.2 VERTICAL AXIS WIND TURBINE (VAWT)Vertical-axis wind
turbines(or VAWTs) have the main rotor shaft arranged vertically.
One advantage of this arrangement is that the turbine does not need
to be pointed into the wind to be effective, which is an advantage
on a site where the wind direction is highly variable, for example
when the turbine is integrated into a building. Also, the generator
and gearbox can be placed near the ground, using a direct drive
from the rotor assembly to the ground-based gearbox, improving
accessibility for maintenance.The key disadvantages include the
relatively low rotational speed with the consequential
highertorqueand hence higher cost of the drive train, the
inherently lowerpower coefficient, the 360 degree rotation of the
aerofoil within the wind flow during each cycle and hence the
highly dynamic loading on the blade, the pulsating torque generated
by some rotor designs on the drive train, and the difficulty of
modelling the wind flow accurately and hence the challenges of
analysing and designing the rotor prior to fabricating a
prototype.
1.2.3 COMPACT WIND ACCELERATION TURBINECompact Wind Acceleration
Turbines (CWATs)are a class ofwind turbinethat uses structures to
accelerate wind before it enters the power-generating element.The
concept of these structures has been around for decades but has not
gained wide acceptance in the marketplace. 1.3 SUBTYPES OF
VERTICALAXIS WINDTURBINE 1.3.1 DARRIEUS WIND TURBINEDarrieus
turbines were named after the French inventor, Georges
Darrieus.They have good efficiency, but produce large torque ripple
and cyclical stress on the tower, which contributes to poor
reliability. They also generally require some external power
source, or an additional Savonius rotor to start turning, because
the starting torque is very low. The torque ripple is reduced by
using three or more blades which results in greater solidity of the
rotor. Solidity is measured by blade area divided by the rotor
area. Newer Darrieus type turbines are not held up byguy-wiresbut
have an external superstructure connected to the top bearing.
1.3.2 SAVONIUS WIND TURBINEThese are drag-type devices with two
(or more) scoops that are used in anemometers, and in some
high-reliability low-efficiency power turbines. They are always
self-starting if there are at least three scoops.
1.3.3 TWISTED SAVONIUSTwisted Savonius is a modified savonius,
with long helical scoops to provide smooth torque. This is often
used as a rooftop wind turbine and has even beenadapted for
ships.
Not all the energy of blowing wind can be harvested, since
conservation of mass requires that as much mass of air exits the
turbine as enters it.Betz' lawgives the maximal achievable
extraction of wind power by a wind turbine as 59% of the total
kinetic energy of the air flowing through the turbine.Further
inefficiencies, such as rotor bladefrictionanddrag, gearbox losses,
generator and converter losses, reduce the power delivered by a
wind turbine. Commercial utility-connected turbines deliver about
75% of the Betz limit of power extractable from the wind, at rated
operating speed.
CHAPTER 2SIMULATION OF WIND FLOW
Study of flow through the proposed models of the wind turbine is
required for determining the best design solution for the housing
of the turbine. The design of the housing must enhance the amount
of kinetic energy available at the throat of the housing. This
would improve the wind energy density available at cross sectional
area of the throat. Thus proper design of the housing can improve
the energy extracted from wind. Here we conducted simulation
studies on four possible types of designs of housing. 1. Actual
model2. Test model 13. Test model 24. Test model 3One of these
models (Actual model) was designed to be virtual replica of the
constructed model. We used the flow simulation add on available in
SolidWorks, a commercial simulation software to conduct the study.
For the purpose of comparison we analysed the flow by choosing a
cylindrical computational domain 132cm long with a diameter of. One
face of the cylinder was chosen for the inlet boundary condition
representing steady wind flow velocity of 10m/s (36km/hr).The
boundary condition on the other face was selected as the pressure
equal to atmospheric pressure. The throat area and length of the
convergent and divergent parts of the housing were made to be the
same for each of the four models. Also the type of material,
roughness of surface, very suitable selected but the same for all
models.
PARAMETERS FIXEDVALUE
Total length of housing32cm
Length of computational domain132cm
Roughness of surface10 micron
Inlet and outlet diameter17cm
Throat diameter9cm
Boss diameter3cm
Free stream velocity10m/s
Table 1: Parameters fixed for simulation
Figure 1: Cylindrical closed pipe constructed for analysing the
flow
Figure1 shows the modelling done for conducting the flow
simulation. Each of the four models was modelled in the same manner
by enclosing them in similar cylindrical closed pipe. Meshes were
later created by computer for solving the various flow parameters
such as total velocity component of velocity, pressure and density.
The flow through the housing were analysed without introducing the
turbine blades. This was done because of three reasons. One, the
flow of the air through the housing with turbine is highly
turbulent and therefore the cut plots will have large variations
according to the selection of planes. Two, the maximum wind energy
available at throat occurs when there is no obstruction to flow of
wind through the housing. This value obtained from each of the four
models could be compared easily without considering the complicated
design of the turbine. Third, the mass rotational speed of turbine
is required to simulate the flow through turbine. Since the speed
of turbine varies with mass of blades and frictional torque of the
generator it becomes cumbersome to incorporate the effect on wind
flow in the housing after the introduction of the turbine.
CHAPTER 3VEELOCITY, PRESSURE AND DENSITY STUDYVELOCITY
STUDYVelocity of wind flowing through the housing is an important
parameter which determines the kinetic energy available for
harvesting. Increase in velocity of wind increases the kinetic
energy of the wind. By principle of continuity rate of mass flowing
into a flow element should be equal to rate of mass flow out of the
element. Mathematically, A V = constant Equation 1So reduction in
area increases the velocity of wind flow through the reduced
section. This is called venturi effect there is a limitation as to
how much the area of throat can be reduced. When the velocity of
flow approaches 0.3 mach the flow starts becoming compressible.
When this happens the velocity of flow doesnt increase even if
inlet flow rate is increased. Figure 1.1 a, b, c, d (next page)
shows the cut plots for the X component of velocity of wind in the
X-Y plane within the preset computational domain. The cut plots
show variation in the x component of wind velocity by using a false
colour image with a colour scale. It may be noted that the colour
scale varies with the each model. It can be observed that in the
actual model peak x-velocity at throat is only 13.56 m/s. It is
also to be noted that major region of the flow outside the actual
model consists of high velocity wind which cannot be harvested
since turbine is placed inside the housing. There is major
restriction to wind flow as the velocity at inlet is only 6m/s
while the free stream velocity is 10m/s. This shows that the design
of actual model has to be improved for more efficient housings. The
Test models show better x-velocity profile. The velocity of flow
outside the Test models never exceeds the x-velocity at the throat.
The throat x-velocity of Test model 1 is especially promising at
18.94 m/s. Peak throat x-velocity for Test models 1 and 2 are
18.05m/s and 17.18m/s. Negative x-Velocity occurs on outer side of
housings. This indicates the formation of turbulent vortices.
Figure 2.a:Cut plot of variation of X component of velocity of
wind through Actual model
Figure 2.b: Cut plot of variation of X component of velocity of
wind through test model 1
Figure 2.c:Cut plot of variation of X component of velocity of
wind through test model 2
Figure 2.d:Cut plot of variation of X component of velocity of
wind through test model 3
Resultant velocity or total velocity profile shown in figure
3.a, b, c and d also shows similar trends. However there are no
negative velocities since on magnitudes are considered. The peak
throat velocity for actual model is 14.95m/s and for Test models 1,
2 and 3, the peak throat velocities are 19.13m/s, 18.18m/s
and17.18m/s.The net kinetic energy available per second from wind
flowing at the throat can be calculated using the formulaKE=1/2 AV3
Equation 2
ModelTotal available KE at throat
WKE at throat after AccommodatingBethz limit of 59%WAssuming 50%
mechanical and electrical lossesPossible output powerW
Actual model11.346.693.34
Test model 123.7514.017.01
Test model 220.3912.036.01
Test model 317.2010.155.08
Table 2: Estimated wind energy harvested by different models
Figure 3.a:Cut plot of Total velocity of wind flowing through
Actual model
Figure 3.b:Cut plot of total velocity of wind flowing through
Test model 1
Figure 3.c:Cut plot of total velocity of wind flowing through
Test model 2
Figure 3.d:Cut plot of total velocity of wind flowing through
Test model 3
PRESSURE STUDYFigure 4.a, b, c and d show the cut plots of
variation of pressure of air flowing through the different models.
Common to all pressure cut plots there is a low pressure region
generated at the throat of the housing. This indicates a drop in
pressure energy .This drop in pressure energy is converted to
kinetic energy of air. Comparing the figure 3.a, b, c and d and
figure 4.a, b, c and d respectively shows an overlap between
regions of high velocity and regions of low pressure.In the inlet
portion of each model there is a sudden increase in pressure before
it lowers as it reaches the throat of the housings. This is due to
sudden obstruction offered to the free wind stream at the
inlet.
Figure 4.aCut plot of pressure variation of wind flowing through
test model 1
Figure 4.bCut plot of pressure variation of wind flowing through
test model 1
Figure 4.cCut plot of pressure variation of wind flowing through
test model 1
Figure 4.dCut plot of pressure variation of wind flowing through
test model 1
DENSITY STUDY
Figure 5.a, b, c and d show us the cut plots of variation of
density of air flowing through the different models. The respective
colour scale show that the variation of density of air is of the
order of 10-3 when the colour changes from red to blue. This
indicates that the flow is incompressible. This observation was
expected as the velocity of air should exceed threshold limit of
0.3 mach for the flow to be compressible. The velocity of wind
selected is 0.03 mach (10m/s).
Figure 5.a:Cut plot of density of wind flowing through Actual
model
Figure 5.b:Cut plot of density of wind flowing through test
model 1
Figure 5.c:Cut plot of density of wind flowing through test
model 2
Figure 5.d:Cut plot of density of wind flowing through test
model 3
CHAPTER 4CONSTRUCTIONThe constructed model consists of four main
components that is the turbine(with housing), DC generator and chip
integrated on PCB for voltage regulation, and mobile set charging
pin.
Figure 6: Shrouded wind turbine mobile charger
Turbine Aturbineis a rotary mechanical device that
extractsenergyfrom afluidflow and converts it into usefulwork. A
turbine is aturbo machinewith at least one moving part called a
rotor assembly, which is a shaft or drum withbladesattached. Moving
fluid acts on the blades so that they move and impart rotational
energy to the rotor. The turbine used in the model has 7 blades. In
a wind turbine as number of blades increases, for a given mass, its
efficiency increases. Wind turbinesuse anairfoilto generate a
reactionliftfrom the moving fluid and impart it to the rotor. Wind
turbines also gain some energy from the impulse of the wind, by
deflecting it at an angle.
Figure 7: Turbine20 volt D.C Generator A simple D.C generator is
preferred over the A.C generator so as to avoid the use of
rectifier circuit and to make the circuit cheap and compact and
also to avoid extra cost. The main difference in the A.C and D.C
generator lies in the manner in which the rotating coil is
connected to the external circuit connecting the load.
Figure8: 20V DC Generator
In an A.C generator both end of the coil is connected to the
external circuit via brushes. In this manner, the e.m.f Eext in the
external circuit is always the same as the e.m.f E generated around
the rotating coil. In a D.C generator the two ends of the coil are
attached to the different halves of a single split ring which
co-rotates with the coil. The split ring is connected to the
external circuit by means of metal brushes. The combination of
split rings and the stationary metal brushes is called a
commutator. The purpose of the commutator is to ensure that the
e.m.f Eext in the external circuit is equal to the e.m.f E
generated around the rotating coil for half the rotating period,
but is equal and opposite of polarity of this e.m.f for the other
half. In the special case as theoretical, the e.m.f seen in the
external circuit is simply.
Eext = E =Emax sin (2ft) Equation -3
If Eext is plotted as a function of time according to the
formula, the variation of the voltage with respect to time is very
similar to that of an A.C generator, except that when the negative
polarity of an A.C generator is reversed to the positive one by the
commutator. So, as to avoid the use of diodes in the A.C generator
D.C generator is preferred. So, as a result a bumpy DC which rises
and fall but never changes the direction is achieved at the output
terminals of the generator.
I.C 7806
I.C. 7806 voltage regulator employ built in current limiting,
thermal shutdown, and safe area protection which make them
virtually immune to damage from output overload. With adequate heat
sinking it can deliver in excess of 0.5 A of current. The most
prominent voltage for charging the mobile phones is 5 Volts. So,
I.C 7806 is used as a regulator. A diode is connected in series to
the output to prevent current flowing in the reverse direction.
0.5V is dropped across the diode. So the output voltage is
regulated to about 5.5V.The Figure 9 shows the circuit diagram of
the voltage regulator.
Figure 9: IC 7806
Figure 10: Circuit Diagram
CHAPTER 5SCOPE AND CONCLUSION
A portable wind powered charging unit of great relevance in the
current scenario. As observed from velocity and pressure cut plots
test model 1 is suitable design for efficient wind power
harvesting. High voltage dc brushless generators could improve the
efficiency of the system so that power output could be stepped up
to 10 watts. The size of the turbine is one of the limitations of
the model.Smaller turbines could be designed at the expense of
lowered power rating for the charger. Designing smaller,
lightweight and efficient turbines can help in improved efficiency.
The turbine could be designed as easy to knock down unit to enhance
portability. The design of the housing could be extended to large
scale power generation since this size of the turbine could be
reduced.Further simulation studies could be conducted involving
various other parameters such as lengths of convergent and
divergent part of the housing. This could further enhance the
efficiency the turbine.
REFERENCESFluid mechanics and hydraulic machines by RK
Bansal
Department of ME, GEC, Thrissur