CHAPTER#1: INTRODUCTION
1.1 The Need for Electricity and a Possile !ol"tion Not all countries possess all the commodities that are available to humanity. These so called underpr underprivi ivilege leged d countr countries ies lack lack amenit amenities ies such such as; abundant abundant food, food, clean clean water water,, medici medicine, ne, wealth wealth,, education, and a healthy environment. The World Bank and other institutions believe that the lack of access to clean and efficient energy services is a factor involved in underprivileged countries from gaining more resources associated with higher living quality, such as wealth !". !". There There are a few new forms of advanced energy, but electricity has been proven to be one of the cleanliest and most efficient forms !" !".. #ne possible solution to unreliable or none$istent central electricity distribution systems is to have distributed generation system %&'(. ) distributed generation system is characteri*ed by the fact that the electricity is produced locally rather than e$ternally. &' is often used in underprivileged countries; however, usually in the form of small generators that run on different types of fossil fuels. The use of renewable types of &' is preferable, since they provide a more sustainable and healthier environment. The most common &' options include; solar, wind, and thermal. + +"" n comparing the various forms of renewable &', five factors must be considered- location, ease of installation, reliability, capacity, and cost. Thermal power is a location dependent, high cost option whereas wind has a lower cost but is unreliable due to changing wind conditions and requires regular mechanical maintenance ". ". /olar /olar power has a relatively lower cost, easy to install and maintain, and for underprivileged countries near the equator, ideal for the location " ".. 0owever the problem with solar power is that it is directly dependent on light intensity. To produce the ma$imum amount of energy, a solar panel must be perpendicular to the light source 1". 1". Because Because the sun moves both throughout the day as well as throughout the year, a solar panel must be able to follow the sun2s movement to produce the ma$imum possible power. The solution is to use a tracking system that maintains the panel2s orthogonal position with the light source. There are many tracking system designs available including passive and active systems with one or two a$es of freedom 3" 3"..
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The goal of our pro4ect was to design an active, dual a$is, solar tracker that will have a minimum allowable allowable error of !56 and also be economically economically feasible feasible to market towards underprivilege underprivileged d countries. countries. We started by e$amining the prior work done in solar tracking methods to determine our course of action. 7rom there we designed and tested several mechanical and electrical options and chose the ones with the most desirable characteristics. 7inally, we built our final tracking system, tested and compared it to ensure that we met our original o riginal goal.
1. !olar Technolo$y )s mentioned above in the introduction, the use of a tracking system greatly improves the power gain from solar radiation. This background goes into further detail on the operation of solar cells and the reason tracking is needed. The different tracking technologies are also described and how they compare to one another.
1.% !olar Po&er '"nda(entals ) fundamental understanding of how a photovoltaic panel works is essential in producing a highly efficient solar system. /olar panels are formed out of solar cells that are connected in parallel or series. When connected in series, there is an increase in the overall voltage, connected in parallel increases the overall current. 8ach individual solar cell is typically made out of crystalline silicon, although other types such as ribbon and thin9film silicone are gaining popularity. : cells consist of layered silicon that is doped with different elements to form a p9n 4unction. The p9 type side will contain e$tra holes or positive charges. The n9type side will contain e$tra electrons or negative charges. This difference of charge forms a region that is charge neutral and acts as a sort of barrier. When When the p9n 4unction is e$posed to light, photons with the correct frequency will form an e$tra electron
current sources. The amount of current a : panel produces has a direct correlation with the intensity of light the panel is absorbing. Below is a simple drawing of the systems ystem-
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Figure 1: Angle of Incidence to Solar Cell
The normal to the cell is perpendicular to the cell2s e$posed face. The sunlight comes in and strikes the panel at an angle. The angle of the sunlight to the normal is the angle of incidence %?(. )ssuming the sunlight is staying at a constant intensity %@( the available sunlight to the solar cell for power generation %W( can be calculated asW A ) @ cos%?( 0ere, ) represents some limiting conversion factor in the design of the panel because they cannot convert !55 of the sunlight absorbed into electrical energy. By this calculation, the ma$imum power generated will be when the sunlight is hitting the : cell along its normal and no power will be generated when the sunlight is perpendicular to the normal. With a fi$ed solar panel, there is significant power lost during the day because the panel is not kept perpendicular to the sun2s rays. ) tracking system can keep the angle of incidence within a certain margin and would be able to ma$imi*e the power generated. Cousa*adeh et al. calculated the amount of power gained by tracking can come close to an ideal 3D difference 3"
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CHAPTER# : E)istin$ Trac*in$ Technolo$y
)s mentioned in the previous sub9section the absorption of light by a : panel is dependent on its angular position to the sun. ) : panel must be perpendicular to the sun for ma$imum solar absorption, which is done by using a tracking system. Cultiple tracking systems e$ist, which vary in reliability, accuracy, cost, and other factors. ) tracking system must be chosen wisely to ensure that the tracking method increases the power gained instead of decreasing it.
.1 I((oile +ers"s ,oile &ifferent power applications require different tracking systems. 7or certain applications a tracking system is too costly and will decrease the ma$ power that is gained from the solar panel. &ue to the fact that the earth rotates on its a$is and orbits around the sun, if a : cell
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:)/)T increases the annual collection radiation by !5 over a 0/)T 3". Thus for one a$is a :)/)T or T/)T configuration would collect the most solar radiation. ) few of these tracker types are shown in 7igure +.
Figure 2: Different One Axis Trackers from Left to Rigt: !SAT and "ASAT
7or an additional power gain a dual9a$is tracking system can be used. The percent gain from going from a :/)T to a dual9a$is system is small 3", but as long as the system doesn2t use more power than gained, it still helps. )gain Wikipedia mentions two classifications for dual a$is trackers- Tip9Tilt &ual )$is Tracker %TT&)T( and )*imuth9)ltitude &ual )$is Tracker %))&)T(. The difference between the two types is the orientation of the primary a$is in relation to the ground. TT&)T2s have the primary a$is hori*ontal to the ground and ))&)T2s have theirs vertical. The a*imuth
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. DI''ERENT TRAC-IN !/!TE, There are three methods of tracking!( )ctive +( :assive and ( >hronological tracking. These methods can then be configured either as !( single9a$is +( &ual9a$is solar trackers.
.% ACTI+E TRAC-IN !/!TE, n active tracking, the position of the sun in the sky during the day is continuously determined by sensors. The sensors will trigger the motor or actuator to move the mounting system so that the solar panels will always face the sun throughout the day. This method of sun9tracking is reasonably accurate e$cept on very cloudy days when it is hard for the sensor to determine the position of the sun in the sky thus making it hard to reorient the structure. )u$iliary bifacial solar cell systems are the simplest of the four active systems. ) bifacial au$iliary solar cell %sensor cell( is fi$ed to the rotary a$le of the tracker and is placed perpendicular to the main bifacial solar panel array. The sensor cell is connected directly to a motor, usually a &> electromotor. When the sun moves, the angle of incidence increases on the sensor cell, which eventually produces enough power to move the motor and the solar panel array. The e$ample by :oulek and Kibra claimed their system was able to collect I3 of the energy with a L 36 tolerance. I" This e$ample can be seen in 7igure .
The electro9optical system is also another relatively simple system. Typically two photo resistors or : cells are used as sensors for one9a$is systems. These sensors are positioned near one another and have a divider, a tilted mount at a calculated angle, or use a collimator to create a useful current and
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Figure #: Auxiliar$
%ifacial Solar Tracker
Figure &: Tracker Sensor Setu's from Left to Rigt: Di(ider) Tilted *ount) and Collimator
.% PA!!I+E TRAC-IN !/!TE,
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:assive Tracking unlike active tracking which deter9mines the position of the sun in the sky, a passive tracker moves in response to an imbalance in pressure between two points at both ends of the tracker. The imbalance is caused by solar heat creating gas pressure on a Flow boiling point compressed gas fluid that is driven to one side or the otherJ which then moves the structure. 0ow9ever, this method of sun9tracking is not accurate.
.0 CHRONOOICA TRAC-IN !/!TE,
>hronological tracker is a timer9based tracking system whereby the structure is moved at a fi$ed rate throughout the day. The theory behind this is that the sun moves across the sky at a fi$ed rate. Thus the motor or actuator is programmed to continuously rotate at a Fslow average rate of one revolution per day %!3 degrees per hour(J. This method of sun9tracking is very accurate. 0owever, the continuous rotation of the motor or actuator means more power consumption and tracking the sun on a very cloudy day is unnecessary.
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CHAPTER# %: DETAI! O' ACTI+E TRAC-IN !/!TE,
%.1 CO,PONENT! U!ED !( +( ( 1(
7our K&Ms Two .3 M:C &> motor >ontrol #f &> motor Esing Melays )rduino EN# M
%. 2OC- DIARA,
6OR,
0 DR
chronolo$ical
T&o %.3 RP, DC (otor
Ard"ino UNO
0 Relay for 'or&ard 4 Re5erse Control
1+ DC s"77ly
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%.% DE!CRIPTION
7or the purpose of clarity, the east9west of the tracker will be called the Fhori*ontal trackingJ while the angular height tracker will be referred to as Fvertical trackingJ. )n active, dual9a$is tracking system prototype has al9ready been designed and built by 1", which consists of the sensor system to determine the position of the sun and a control system which reads data from the sensors to command the movement of the tracker. ) program to control the tracking system has been also developed 1". The sensor system consists of two sensors- one to deter9mine the position of the sun in the sky and another to determine the position of the sun2s movement from east to west. 8ach sensor consists of two >admium /ulphate %>d/( light dependent resistors %K&Ms(.
The K&Ms were placed as shown in 'i$"re 8, a shadow will fall on one of the K&Ms when the sensor is not pointing directly toward the sun resulting in difference of the level of resistance between the two K&Ms. This difference will be detected by the )rduino in the control system and will move the tracker accordingly so that both K&Ms are pointing towards the sun.
Figure +: Sensor res'onse once a sado, is cast on one LDR
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%.0 !UN ,O+E,ENT THROUHOUT /EAR
To decide how the tracker would move, it is important to consider the movement of the sun in the sky through9out the year. The sun path diagram of 'i$"re 9 shows the annual variation of the path of the sun in 'andhinagar.
Figure -: Sun 'at diagram for .andinagar) India
7rom the sun path diagram, the movement of the sun in the sky throughout the year in 'andhinagar can be divided into three different scenarios. )s the sun rises from the 8ast to sets to the West, the sun path may move in the /outhern or Northern region, or it may move almost directly overhead. f the path of the sun is in the Northern region, the structure must be able to track the sun from 8ast to West in anti9clockwise direction. f the path of the sun is in the /outhern region, the structure must be able to track the sun from 8ast to West in clockwise direction. f the sun is moving overhead, only the 11
a$is which tracks the angular height of the sun will move. n all three situations, there must be a way to turn back the tracker to its original position after it has followed the movement of the sun from morning to dusk. To achieve this, limit switches are added to the system. When the limit switch is triggered at the end of the day, the tracker will move back to its original position.
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CHAPTER#0:
INTER'ACIN
OPEN!OURCE
HARD6ARE
6ITH
,ATA2
0.1 O7en !o"rce Hard&are #pen9source hardware %#/0W( consists of physical artifacts of technology designed and offered in the same manner as free and open9source software %7#//(. #pen9source hardware is part of the open9 source culture movement and applies a like concept to a variety of components. The term usually means that information about the hardware is easily discerned. 0ardware design %i.e. mechanical drawings, schematics, bill of materials, :>Blayout data, 0&K source code and integrated circuit layout data(, in addition to the software that drives the hardware, are all released with the 7#// approach. Different O7en so"rce hard&are
)rduino K8'# Cind storm N$t :anda Board Beagle Board etc.
0. Ard"ino )rduino is a tool for making computers that can sense and control more of the physical world than your desktop computer. ts an open9source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board. )rduino can be used to develop interactive ob4ects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. )rduino pro4ects can be stand9 alone, or they can be communicating with software running on your computer %e.g. 7lash, :rocessing, Ca$ C/:.( The boards can be assembled by hand or purchased preassembled; the open9 source &8 can be downloaded for free. The )rduino programming language is an implementation of Wiring, a similar physical computing platform, which is based on the :rocessing multimedia programming environment.
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6hy Ard"ino
There are many other microcontrollers and microcontroller platforms available for physical computing. :aralla$ Basic /tamp, Netmedias BO9+1, :hidgets, CTs 0andyboard, and many others offer similar functionality. )ll of these tools take the messy details of microcontroller programming and wrap it up in an easy9to9use package. )rduino also simplifies the process of working with microcontrollers, but it offers some advantage for teachers, students, and interested amateurs over other systems•
ne$pensive 9 )rduino boards are relatively ine$pensive compared to other microcontroller platforms. The least e$pensive version of the )rduino module can be assembled by hand, and even the pre9assembled )rduino modules cost less than P35
•
>ross9platform 9 The )rduino software runs on Windows, Cacintosh #/O, and Kinu$ operating systems. Cost microcontroller systems are limited to Windows.
•
/imple, clear programming environment 9 The )rduino programming environment is easy9to9use for beginners, yet fle$ible enough for advanced users to take advantage of as well. 7or teachers, its conveniently based on the :rocessing programming environment, so students learning to program in that environment will be familiar with the look and feel of )rduino.
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#pen source and e$tensible software9 The )rduino software is published as open source tools, available for e$tension by e$perienced programmers. The language can be e$panded through >QQ libraries, and people wanting to understand the technical details can make the leap from )rduino to the )M > programming language on which its based. /imilarly, you can add )M9> code directly into your )rduino programs if you want to.
•
#pen
source
and
e$tensible
hardware
9The
)rduino
is
based
on
)tmels )TC8')+G microcontroller. The plans for the modules are published under a >reative >ommons license, so e$perienced circuit designers can make their own version of the module, e$tending it and improving it. 8ven relatively ine$perienced users can build the breadboard version of the module in order to understand how it works and save money.
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Figure /: Arduino
0.%,ATA2 Interface for Ard"ino: C)TK)B and /imulink support )rduino, an ine$pensive, open9source microcontroller board. )rduino boards provide fle$ibility for introducing concepts such as signal processing and mechatronics. 7eatures of the )rduino platform includeWide adoption and useful support from numerous websites, newsgroups, and user forums 8$tensibility through plug9in boards for a broad range of applications, such as motor control, wireless communication, audio processing, and data logging 8asy setup of simple signal processing or motor control pro4ects C)TK)B and /imulink support two )rduino boards)rduino Cega +3=5 board %recommended(, which features• • • • •
)Tmega+3=5 processor running at != C0* !+G RB of flash memory != analog and 31 digital <# channels with !1 :WC outputs Built9in E/B, /:, and +>
)Tmega+G processor running at != C0* • • •
+ RB of flash memory = analog and !1 digital <# channels with = :WC outputs Built9in E/B, /:, and +>
Re;"ired Code 'or Ard"ino Interface 6ith ,ATA2:
This lets you control your )rduino board over E/B from a C)TK)B session, in either Windows, Cac or Kinu$. 7or e$ample you can instantiate an )rduino ob4ect from C)TK)B using-
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<< a=ard"ino>?CO,%?@
Figure 0: Arduino Initialiation
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CHAPTER#3: INTER'ACIN DRs 6ITH ,ATA2
3.1 CONNECTION DE!CRIPTION ) light sensor %K&M or Kight &ependent Mesistor( is a simple component that provides a variable resistance those changes with light, which we can read into the )rduino board as an analog value. if light intensity increases value of resistant is decreases. Caterial needed• • • •
)rduino board K&M ! k ohm resistor cables
We connect three wires to the )rduino board. The first goes to ground from one of the pins of the K&M. The second goes from 3 volts to one of the pins of the ! k ohm resistor, the other pin of the resistor goes to the free pin in the K&M. The third goes from analog input + to the K&M pin that is connected to the resistor.
3. CIRCUITE DIARA, AND CONNECTION ON 2RAD2ORD
FI.R3 14: CIRCIT CO553CTIO5 OF LDR
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f change in the amount of light incident on the K&M, we change the amount of resistance on the K&M, witch changes the voltage value, giving us a different analog input. Well read different values between 5 %for 5( and !5+ %for 3(. 7or read this value C)TK)B provide following codear=a.analo$Read>@
here )rduino convert analog value to digital value by using )to& converter, which is already configured on board. /o C)TK)B get the value between 5 to !5+. Now from above command C)TK)B save K&M save the value of resistance in Sar2. /o like this we can stored values of four K&M and compare them with each other in pair. /o by comparing two K&Ms we can sense change in light intensity from both direction hori*ontal as well as vertical.
FI.R3 11: CO553CTIO5 OF LDR 6IT! ARDI5O
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"
3.5 RPM 12V DC servo
Forward/Rev erse contro
Arduino UNO
Figure 12: connection of ,ole 'ro7ect
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CHAPTER#8 CODIN
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CHAPTER#9 'UTURE !COPE
•
>ircuit of comparison of two values of K&M resistance using Cicrocontroller
•
)TGIc3! is very complicated. /o, we use the )rduino and C)TK)B program where )rduino works as channel
•
between K&Ms, two motors C)TK)B. We can also provide MT> by 4ust programming in C)TK)B which switch rotation of
•
motor to set plate at its original position. We can also make 'E for simple operation for start and stop the whole program and also we can also monitor continuously value of K&Ms.
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CONCU!ION
)t ma$imum, the solar tracker was perpendicular to the light source by !.3 degrees. The built system had a calculated annual energy gain of 1G.IG+ compared to an immobile solar panel. >ompared to a single a$is tracker, the dual9a$is tracker had an annual energy gain of =.351. 7urthermore, testing showed that the power used by the tracking system built was much less than the power gained by tracking the sun accurately. This means that if the tracking system were to charge its own batteries, it would be entirely self9sufficient e$cept for maintenance.
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RE'RANCE
!" Bailis, Mobert. FWood in 0ousehold 8nergy EseJ. 3nc$clo'edia of 3nerg$. +551. :ages 3!=, 3!G. +" )ckermann, T., )ndersson, '., /Uder, K. F&istributed generation- a definitionJ. 3lectric "o,er S$stems Researc . )pril +555. :age !I3. " Baner4ee, F>omparison of #ptions for &istributed 'eneration in ndiaJ. 3nerg$ "olic$. :ages !539!!5. 1" 'oet*berger, )., 0ebling, >., /chock, 0.. F:hotovoltaic materials, history, status and outlookJ. *aterials Science and 3ngineering: R: Re'orts . +55+. 3" Cousa*adeh, 0., Reyhani, )., Vavadi, )., Cobli, 0., )brinia, R., /harifi, ).. F) review of principle and sun9tracking methods for ma$imi*ing solar systems outputJ. Rene,a8le and Sustaina8le 3nerg$ Re(ie,s . Vanuary +55I. :ages !G55, !G55, !G51, !G5=, !G!+. =" Rrauter, /tefan. F/olar 8lectrical :ower 'eneration- :hotovoltaic 8nergy /ystemsJ. /pringer. +55=. :ages +!9++. D" Cehleri, 8., ervas, :., /arimveis, 0., :alyvos, V., Carkatos, N.. F&etermination of the optimal tilt angle and orientation for solar photovoltaic arraysJ. Rene,a8le 3nerg$ . )pril +5!5. :age +1=I. G" /efa, ., &emirtas, C., Xolak, .. F)pplication of #ne9)$es sun Tracking /ystemJ. 3nerg$ Con(ersion and *anagement . +55I. :age +D!5. I" :oulek, ., Kibra, C.. F) ery /imple /olar tracker for /pace and Terrestrial )pplicationsJ. Solar 3nerg$ *aterials and Solar Cells . +55I. :ages II9!5!. !5" http-<
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