1992-8645 DESIGN AND DEVELOPMENT OF AN EMBEDDED … · The embedded tracking system is built on SBC...

Journal of Theoretical and Applied Information Technology15th December 2016. Vol.94. No.1

© 2005 - 2016 JATIT & LLS. All rights reserved.

ISSN: 1992-8645 www.jatit.org E-ISSN: 1817-3195

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DESIGN AND DEVELOPMENT OF AN EMBEDDED ACTIVESOLAR TRACKING AND MANAGEMENT SYSTEM BASED

SBC1NASEER SABRI, 2SAIFALLAH M. ABGENAH, 3M. S. SALIM, 4NOAMAN M. NOAMAN,

2HAMZA A. JUMA1Computer Engineering Department, AlNahrain University, Iraq

2Engineering College, University of Tripoli, Libya3Laser and OptoElectronic Engineering Department, AlNahrain University, Iraq

4Informatics Engineering Department, AMA International University Bahrain, BahrainEmail: [email protected]

ABSTRACT

Solar energy is gaining a rapid notoriety as an important source of renewable energy. Per se, it is vital forthose who aim towards maximizing the total gain of its energy to utilize a method that will insure maximumenergy gain by tracking the sun's position during its daily cycle. This research targets the means ofcollecting the utmost solar energy distributed by the sun by implementing an embedded trackingmechanism that will track the sun as it changes its position during its daily cycle. This embedded trackingsystem is developed based on an open source embedded single board computer (SBC) using an open sourcecode that can be easily modified. The embedded tracking system is built on SBC type RaspberryPi as themain data collection and decision making unit for the system. This microcontroller is a part of an SBCdeveloper's board that has a number of GPIOs to connect different peripherals to be used in the trackingsystem and controlled by the microcontroller. These peripherals consist of four LDR sensors to be used forsensing the sun's position by reading the light intake and sending the readings to the microcontroller to beprocessed, the LDR with the most light intensity readings will be the targeted position for the embeddedtracking system to move the solar panel towards using two servo motors which will also be connected to theSBC via the GPIO pins, the two servo motors will have different tasks, one servo motor will be in charge ofmoving the solar panel vertically and the other servo will move the solar panel horizontally. Theperformance and characteristics of the solar tracker are experimentally analyzed to show the need andadvantages of using this method of embedded tracking system. The results show that the designedembedded solar tracking system is efficiently tracking the sun and collecting more energy as compared tothe static solar panels. In addition to the proposed embedded system has advantages over other systemrepresented by real time tracking based on an active sun potion computing technique. The embedded solartracking system offers cost effective and efficient solar tracking besides open source programming whichallows for future enhancement and modification.

Keywords: Embedded Systems, Open Source Technology, Solar Tracker, Sensing, Solar Panels,Renewable Energy

1. INTRODUCTION

The Sun is an important element in this world welive in. Without Sun, nothing could exist becauseit’s the main source of energy for all livingcreatures. One other advantage that we gain fromthe Sun is solar energy. For millions of years, thisenergy has been used to produce heat, light and togrow plants. Modern day technologies are beingdeveloped to harness the utilization of such a cleanenergy application in order to address the global

challenges of climate change and sustainabledevelopment. Solar energy is rapidly gainingnotoriety as an important mean of expandingrenewable energy resources. Solar energy is clean,renewable and is the largest natural source ofenergy. Engineers have developed various means tocollect Sunlight and convert it into energy, thisprocess is called solar energy, and they have madethis possible by inventing what's called SolarPanels. The main concept of a Solar Panel is tocollect Sunlight and convert it into energy as long as




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the Sunlight hits the surface of the Solar Panel, butwhen the sun rotates as part of its daily cycle theSunlight will not reach the surface of the SolarPanel, so the energy collected will reduce [1]. Tosolve this problem, a tracking system will beembedded into the Solar Panel. The basic functionof this embedded tracking system will be to trackthe Sun during its daily cycle. To know the Sun'sposition a light dependent resistor sensor will beused to locate the Sun's position and this sensor willsend data to a special program that will convert thisdata into coordinates. To move the Solar Panel, aServo Motor

will be used; this motor will get the coordinatesfrom the data sent from the sensor and move theSolar Panel to the desired location which in thiscase will be the position where the Sunlight is at itsmost intensity. The main processing unit for thisembedded tracking system will be an SBC singleboard computer. This system is suitable to be usedin homes or small factories that want to save theirbudget for a long term.

A. Embedded SystemsA system is a set of programs or connected

hardware that has one or many tasks. The termEmbedded System is commonly used by computersystems that are dedicated to a certain function ormany functions within a larger system. The mainadvantages that an embedded system has over anygeneral purpose computer is that it has lower powerconsumption, smaller size, portable and lightweight, costs less and rugged operating ranges.Embedded systems nowadays exist everywhere likerobotics, automobiles, airplanes, digital cameras,home appliances and even mobile phones [ 2].

There are many platforms that are considered tobe embedded systems one of them is called theSingle Board Computer (SBC). The SBC can carryout the tasks that a general purpose computer can dobecause it has a processor, storage unit, RAM andI/O ports that can be used to connect to otherhardware devices and an operating system. SBCcompanies are widely spread and each companydesigns its own board based on the developersneeds for example RaspberryPI, TechnologicSystems, Beagle Bone and many more [3]. Beside,Microcontrollers are considered to be embeddedsystems which can also perform one or many tasksin a system.

B. Open Source TechnologiesOpen source technology is the development and

production philosophy of making available the

developed source code of the software to end usersand developers not only to use the code but they canalso modify as per their own needs. The name OpenSource is not only limited to software, but there canbe open source hardware, where the end users candevelop the hardware and modify it to suit their ownneeds [ 4].

2. EMBEDDED ACTIVE SOLARTRACKING SYSTEM

Optimize utilizing of maximum solar energythrough solar panels can be achieved by adopting;firstly, design an embedded system that can detectand compare the intensity of light. Secondly, designan embedded system that is able to move a Servo-Motor based on the intensity of light and show thevoltage intake of Solar Panel, and lastly is byadopting an open source monitoring and trackingpackage that easiest to use system for otherdevelopers.

The proposed research is focused on designingand building the prototype of an embedded solartracking system that would be a starting point tobuild the realistic solar tracking system. Therefore,this prototype will cover the scope as follows:

Move 90° vertically and 180° horizontallywest and east.

Use two Servo-Motors for vertical andhorizontal movements.

Use 4 Light Dependent Resistor [LDR] assensors.

Read voltage intake of the solar panel usingADC and LCD.

Develop an open source tracking code.

3. RELATED WORK

Solar tracking is an important part of solar energycollection, because it maximizes the energycollected by following the Sun's location during theday as many researchers have found out byexperiments various types of tracking methods. Inthis chapter the work done on solar tracking byvarious numbers of researchers is reviewed.

A. The Earth’s Movement around the SunThe earth rotates around the Sun on a level called

elliptical orbit having the Sun as the foci. A yearcan be defined as the time earth takes forcompleting this orbit. The relative locus of earth andthe Sun is appropriately shown by means of




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celestial sphere around earth. The equatorial planeand celestial sphere intersect in polar axis andcelestial equator. The motion of the earth around theSun can be visualized by ostensible motion of theSun in elliptic tilted at 23.458 degree w.r.t celestialequator. The angle between the lines that join thecenters of the earth and the Sun and its prognosis onthe equatorial plane is known as solar declinationangle (δ). On March 20/21 and on September 22/23,this angle becomes zero. The rotation of the eartharound polar axis is one revolution per day. This isrepresented by the rotation of the celestial sphereabout the polar axis and prompt locus of Sun islabeled by hour angle v, the angle between themeridian of the site and meridian passing throughSun. At solar noon, the hour angle is zero and thisrises in the east. For observers on the surface of theearth at a place with latitude φ, an expedientcoordinate system is described by one vertical lineat location that crosses the celestial sphere on twopoints, the nadir and the zenith, and subtends theangle φ with polar axis, Figure 1.

Figure 1: Graphic depiction of solar angles [5]

The big circle that is perpendicular to verticalaxis is horizon. The latitude [φ] of a location can bedefined as the angle made by radial line that joinsthe location to earth’s center with line’s projectionon equatorial plane. The rotation axis of the earthcrosses the surface of the earth at 900 of North Polelatitude and 900 of South Pole latitude. Any placeon earth’s surface can be described by intersectionof latitude and a longitude angle. The α, solaraltitude angle, thus can be described as the verticalangle between the direction of rays of the Sunpassing through the point and the prognosis of therays of the Sun on the horizontal plane asrepresented in Fig. 2. Alternatively, the altitude ofthe Sun can be defined in solar zenith angle i.e. θzthat is vertical angle between rays of the Sun and aperpendicular line to horizontal plane from the point

defined by θz = 900 - α. γs i.e. solar azimuth angle isdefined as the horizontal angle from south tohorizontal projection of rays of the Sun [ 6]. Inorder to calculate the solar positions and fordefining relationship between stated parameters,many surveys are conducted. A FORTRANprogram is used by Walraven to calculate the valueof the parameter for Sun’s position. The parameterscomputed were for time, Sunset and Sunrise actualtimes, elevation, local azimuth, and declination andthe computed Sun’s position was within 0.018 ofaccuracy [ 7].

B. Radiation on an Inclined and Tracking SurfaceThe data of solar radiations is generally found in

global radiations form on horizontal surface and theposition of PV panels is at an angle to horizontalplane. Consequently, the energy input to the PVsystem has to be calculated accordingly. There arethree steps of this calculation. Firstly, fordetermining the beam and diffuse components ofglobal irradiations on horizontal plane, the data forthe site is used. This can be done by the use ofextraterrestrial daily irradiation Β0 as reference andby calculating the ratioKT = G/Β0, called clearness index where G is dailyglobal irradiation on horizontal plane, and KT can bedescribed as the mean reduction in solar radiationby atmosphere in a month at a specified. Secondly,diffuse radiation is found with the use of practicalrule that the diffuse fraction D/G of globalirradiation is general function of clearness index KT.As B=G-D, this technique determines beanirradiation and diffuse on horizontal plane. Thirdly,apposite angles dependence of all factors is used indetermining the beam irradiation and the diffuse oninclined surface. Allowing reflectivity of contiguousarea, the albedo can be determined too. By addingabove stated three elements, one can get total dailyirradiation on inclined surface [8].

The Sun move on the sky in the day. Theprojection of collector area on plane perpendicularto the directions of radiations in fixed solarcollectors is given by function cosine of angle ofincidence, Figure 2.

The angle of incidence is denoted by θ and thehigher the value of θ, the lower the power is. Incase of the usage of tracking collectors, theoreticalcalculation of extracted energy is done presumingmaximum irradiation intensity at I=1100Wm-2

falling on the area perpendicular to the radiationdirection.




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Figure 2: The θ, angle of incidence of solar radiation [8]

Taking the length of the day as t=12h=43,200s,the intensity of tracking collector is always orientedoptimally facing the Sun as compared to the fixedcollector perpendicularly oriented to the radiationdirection at the time of noon only. The collectorarea is denoted by S0..

C. Energy Gain in Tracking SystemsOne axis can be used for the implementation of

solar tracking but if more accuracy is required thenobviously two-axis Sun-tracking systems will berequired. Two kind of Sun tacking systems areavailable for two-axis as; polar tracking andelevation/azimuth tracking. The solar trackerincreases the accumulated energy and this is adevice that preserves photo thermal panels or PV inoptimal place that is perpendicular to radiations ofthe Sun in day light. Finster introduced the firstcompletely mechanical tracker in 1962. After oneyear, an automatic-electronic-control mechanismwas introduced by Saavedra that was used toorientate an “Eppley pyrheliometer” [8]. There is noneed to place tracker direct towards Sun forefficiency. If the purpose is achieved by 100, 98.5percent output of full tracking the output can betaken. While if it is cloudy, foggiest positions, 20percent of the annual gain may be reduced. In atypically good area, the range of annual outcomewould be 30 percent to 40 percent are normal. Therange of outcome may vary between zeros to 100percent in any day [ 9].

Agee et al. examined field applications and trendsin market of technologies related to solar tracking,the allied costs and expenses, requirements formaintenance and ways to improve their efficiency.These researches include program-control systems,hydraulic systems and trackers based on sensors likesingle-axis or dual-axis types and trackers based onpolar-axis. For installations of lower capacity,hydraulic systems found to be more suitable.Moreover, they asserted that the performance ofpolar-axis tracking systems is like two-axis type

systems but their cost is equal to single-axistracking system [ 10].

There are few common characteristics of all typesof tracking systems as follows [11][12][13][14]:

Two or one motors those are moving. Structure based on one column. Device of light sensing. Auxiliary or independent supply of

energy. Moving or following light as per calendar. Step-wise or continuous movement. Whole year tracking or in exception of

winter.With or without tilt angle adjustment orientation.

4. EMBEDDED SYSTEM DESIGNINGAPPROACH

The Dual axis solar tracking system will track theSun during the Sun's daily movement in a dualmode horizontally and vertically, the trackingprocess is done by using the SBC controller thatwill collect data from four Light dependent resistorsensors, data will be read from all four sensors butonly the sensor with the highest light intensityreadings will cause the Solar Panel to move towardsthe Sun's position using two servo motors, the firstmotor is for the vertical movement and the secondmotor is for the horizontal movement of the SolarPanel. An analog to digital convertor ADC0804 isused in system to show how much voltage we aregathering from the Sun with assist of attached LCDmodule. Figure 3 shows the overall systemarchitecture.

A. Hardware Design

The hardware used in the system can bedescribed in simple components, starting with themain part of the systems which acts as the maincontroller of the system. The SBC based on a900MHz quad-core ARM Cortex-A7 CPU with1Gbyte RAM as the main processing unit that has anumber of GPIOs that link the board to four LDRsensors and the two Servo motors that are connectedto the Solar Panel and a digital voltmeter that isconnected to the Solar Panel.




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Figure 3: Overall Active Dual Axis Solar TrackingSystem Architecture

D. System DesignThe system design consists of a an SBC board

and four LDR sensors that are connected to theSBC board using the GPIO pins, each LDR sensorwill be placed on the Solar Panel in a crossposition, bottom left LDR sensor will be connectedto PIN0 and to the GND PIN on the SBC board,bottom right LDR sensor will be connected toPIN1 and to the GND PIN on the SBC board, topleft LDR sensor will be connected to PIN2 and tothe GND PIN on the SBC board and the top rightLDR sensor will be connected to PIN3 and to theGND PIN on the SBC board. Each of the LDRsensors will be connected to a 10k Ohm resistorbefore being connected to the GND PIN see Fig. 7and 8 for system design and schematics.

The next step is to connect the two Servomotors throughout the signal conditioning anddriving circuit to the SBC board, the first motorwill move the Solar Panel horizontally and it isconnected to PIN9 on the SBC board and thesecond motor will move the Solar Panel verticallyand it is connected to PIN10 see Figure 4 forsystem design and schematics.

E. Software and System Operation

There are many types of tracking systemalgorithms that can be used to track the Sun, butsince LDR sensors are used in this particularsystem this means that the system has an activetracking mechanism.

What is meant by active tracking is that thetracking systems use sensors to find the placewhere the Sun is at its most intense brightness andmove the Solar Panel towards that position, if thisposition is changed it would immediately move the

Solar Panel towards the new position withoutwaiting for a certain command or mathematicalalgorithms. The software part for the system isdeveloped using a program that is written in C++language.

Figure 4: Active Dual Axis Tracking System Schematic

The software of the system can be dived tothree main functions. The first is the startupposition or what is called the initial position. Sincethe system is an active tracking system the startingposition of the Solar Panel is not an issue becauseas soon as the system is powered on, it will detectthe Sun's position and immediately move the SolarPanel towards the Sun's position.

The second part is reading data from the fourLDR sensors, the tracking system will be readingfrom all LDR sensors, but will only respond to theaverage LDR sensors either left top or left buttoncompared to right LDR sensors with the highestlight intensity reading, Figure 5.

Top left(TL)

Top Right(TR)

Bottom Left(BL)

TL,BL TR,TL Top Left(TL)

BottomRight (BR)

BR,BL TR,BR Bottom Left(BL)

Figure 5: Light Detection Sequence

When an LDR sensor receives light from alight source or the Sun the other three LDR sensorsare shadowed out by the cross design that is used toplace the four LDR sensors on the tracking system.The Solar Panel will move to the direction of theLDR sensor that has the least resistance whichmeans that this LDR sensor is facing the source oflight with the greatest light intensity Figure 6shows the cross design used to place the four LDRsensors on the tracking system.




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The third part of the program is to move thetwo Servo motors based on the readings collectedfrom the LDR sensors.

Figure 6: Cross Design used for LDR Sensors Placementon the Tracking System

One servo motor is going to be responsible forthe vertical movement of the system and the otherServo motor will move the system horizontally asshown in Figure 7.

Figure 7: Vertical and Horizontal Movement of theTracking System

5. ANALYSIS AND EVALUATIONCRITERIA

The validating process carried out for this design isto perform side by side the embedded active solartracking design and passive system design under samesunspot and orientation. The accumulated percentagedifference between those systems will be recorded for 10hours with variant day environment such as clouds andclear sky. Cloudy sky has been categorized into fully andpartially cloudy day. Indeed, system response time iscomputed.

6. RESULTS AND DISCUSSION

The results indicate that the tracking system hasgained more voltage intake than the static systemby showing an increase in voltage intake in thetimes where the sun had changed its position fromthe direction of the static system directed towards,as Figures 8,9 and 10 show. Moreover the dualaxis tracking system has shown good performanceby the time it takes to respond to the light's position

by having a response time of less than one secondto move the solar panel towards the sun's positionand this delay is due to the prototype's design notthe actual code and tracking method see Figure 11.

As known, the Sun has a daily movement cycle,causing the amount of Sunlight hitting the surfaceof the Solar Panel to change depending on thedirection the Solar Panel is facing. This will causethe decrease of energy collected when the SolarPanel is not facing the Sun directly. To solve thisproblem this project a number of different trackingmethods have been presented to increase the SolarPanel's performance of collecting Sunlight bytracking the Sun's position during the its dailycycle. Figure 8 shows that both the passive anddesigned the active tracker system behave withlittle bit variation during daylight morning hoursfor sunny days while before sunset the percentagedifference increased for the active system since ithas the ability to track the sunspot accordingly togain maximum energy.

Figure 8: Percentage difference between the static andtrack systems for the sunny day

While the active tracker shows high gaincompared to passive system during cloudy skyduring the morning hours as Figure 9 shows. Thisis true since the sun is high over the horizon anddue to its tracking face the solar panel as possibletowards the sunspot.




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Figure 9: Percentage difference between the static andtrack systems for the cloudy day

Contrarily, the passive system missed thisduring this time. While the percentage differencedecreases when time moving towards evening dayand hence both systems can not got sunspot eventheir solar panel face the sunspot. In general,during cloudy day the system behave showsconfused results even though the active systemyields the most energy gain.

Partially cloudy day affects the percentagedifference for both systems, as shown in Figure 10.The active system has shown its high gain ofenergy compared to passive system since afternoontime due to the sun movement that cause thesunlight to be partially invisible and thus the activesystem based on maximizing sensing energyprovide a better gain of solar energy compared topassive and this increase all the time fromafternoon till sunset.

Figure 10: Percentage difference between the static andtrack systems for the partially cloudy day

Figure 11: Testing time delay for the tracking system

Figure 11 presents the delay time in secondsof the designed active solar tracker systemmovement which indicate the performance of thetracker algorithm that guide the solar panel. Sincethe delay time for all position movements arewithin one second due to adaptive track movementexcept the point of sunrise where the system isinitialized to track the sunspot in the early daylight.

Most of the developed tracking systemsrequire a high level of engineering andprogramming skills to maintain and develop iffuture developments are needed. Some other solartracking systems developed using what is calledpassive tracking, which mainly depends onmathematical algorithms that calculate the Sun'smovement depending on the location andgeographical landscape the Sun tracker is placed,this method is not efficient because every time theSolar Panel is moved from its location newalgorithms need to be calculated, and only peoplethat are experts in the calculation can set the solartracker again in its new location. Other trackingsystems only track the Sun In one direction andknown as single axis tracking systems. Thismethod is not efficient because the Sun moves inmore than one axis, which will make the amount ofenergy collected will be less than the solar energythat is out there to be collected.

This project presents an active dual axis solartracking system that will track the Sun during theSun's daily cycle. The term active means that thesolar tracking system will be on standby when thethere is no Sunlight or light source, as soon as theLDR sensors of the tracking system senses a lightsource it will move the Solar Panel towards thelocation of that light source, and if the direction ofthat light source changes the solar tracker willfollow the light source to its new position.A number of tests have been conducted on theactive dual axis solar tracking system and all of




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them show the advantage of using this trackingmechanism as the tests were done in three differentweather conditions, sunny, partially cloudy andcloudy. All three tests gave the active dual axissolar tracking system an advantage over the SolarPanel that did not have a tracking system. As forthe financial scale of the active dual axis solartracking system, it has been found that the costs forbuilding the system is very cheap compared to theother tracking systems out there, because thesystem uses an SBC board that is based on the SBCof Raspberry Pi as a main core of the system whichis open source and cheap to buy SBC platform.

7. CONCLUSION

In conclusion the tracking systems are veryuseful for increasing the collection of solar energynot only in a single axis, but also in a dual axismode and the method of active tracking is moreefficient than passive tracking because it itsportable and does not depend on a complex methodof tracking. And thus, efficient energy accumulatedis achieved beside simple and flexible open sourcesingle embedded system designed that can beadapted for different task situations as needed forsystem enhancements and optimization.

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[5] Clifford, M. J., & Eastwood, D. [ 2004].Design of a novel passive solar tracker.SolarEnergy, 77[ 3], 269-280.

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1992-8645 DESIGN AND DEVELOPMENT OF AN EMBEDDED … · The embedded tracking system is built on SBC...

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