A. Solar TrackerA solar tracker is an electro-mechanical device fororienting a solar photovoltaic panel toward the sun trackers,especially in solar cell applications; require a high degree ofaccuracy to ensure that the concentrated sunlight is directedprecisely to the powered device .Solar trackers can be active or passive and may be singleaxis or dual axis . Single axis trackers normally use a polarmount for maximum solar efficiency and employ manualelevation (axis tilt) adjustment on a second axis, which can beadjusted regularly during the year. It has been estimated thatthe yield from solar panels can be increased by 30 to 60percent by utilizing a tracking system instead of a stationaryarray .Trackers can be relatively inexpensive for photovoltaics.This makes them especially effective for photovoltaic systemsusing high-efficiency panels . Solar trackers usually needinspection and lubrication on a regular basis.Active trackers, which use motors and gear trains, arecontrolled by an electronic circuit responding to the solardirection.B. ApplicationsIn this paper a solar tracker is realized to detect amaximum power from sunlight. The position of maximumdetection power is stored in memory. The stored data can beapplicable for many application such as Large photo voltaicpanels can track the sun all the day light and by that giveabove 95% efficiency in generating electricity; solar heaterswill also track the sun all the day light and by that less panelsare required at the initial cost; while in the home automationsystems, this system is also needed in turning light ON andOff and also for opening and closing the curtains.The detection of the position of the sun undergoes severalsteps. A digital system is used to calculate the maximum sunradiation. It is connected to a stepper motor and toPhotoresistors to redirect the panel to the sun. It sends thereceived data (position of the sun) to the stepper motors inorder to position it toward the sun. The position tangles aresaved in the registers of the digital processor such as amicrocontroller and can be displayed on an LCD or can betransmitted to control a remote system. Figure 2 illustrates thesystem block diagram.Figure 2. Block diagram of the sun trackerIII. HARDWARE SYSTEM IMPLEMENTATION OFTHE PROPOSED SYSTEMThe smart solar system is a self-powered system; allcomponents of the system depend on each others, the systemdoes not need any supply from the external world but only sunlight. Those components interconnect with each others inorder to form a closed system.The solar radiation gathered by the photovoltaic cell istransformed into electrical energy; the panel will feed theinput of the charger which will charge a 12 Volt DC battery.The second functionality of the cell is to give precise voltageto the tracker, in order to reach the most efficient direction andorientation of the system which will allows maximum sunlightabsorption.The battery will supply the system with a 12 Volt DC. Themotors, the charger, the tracker and the sensors are suppliedby the battery. The battery is charged by the photovoltaic cellthrough the charger controller as shown in figure 3.Figure 3. Relations between main parts of the systemFigure 4 shows the block diagram of the tracking system.It explains the dependency of the tracker. As for the firstrunning, the system has to detect sun light in a quick andaccurate way, for this reason photoresistors are used . Itwill allows the tracking system to locate the nearest positionof the light based on comparisons done in the digitalprocessor, this will guide the system in a x-y-z plane, thatmeans all angles and locations can be detected and reacheddue to the two motors (two rotational axes).The accuracy of the system is enhanced by the gear factorand ratio, the used steppers motors are of 3.5 degrees/step,with the gears added to the motors many factors wereimproved such as the degree/step (less degree per step whichleads to better accuracy in position and angles) and hightorque for the motors.Figure 4. Dependency of the trackerThree photoresistors are used in the tracking system all arefixed on the upper part of the system near the photovoltaic cellin an X-O-Y manner as shown in figure 5. It allows areference photoresistors the one at position O which will be
compared with the photoresistors X and Y and depending onthe voltage output.The tracker will compare X and O positions, thecomparison will end after a very near values of outputs ofthose two photoresistors are reached, a loop will control thestepper motor motion and steps till a near equality of sunlightdistribution will be reached. After reaching an acceptableposition and values for the X-O position test, the Y-Ophotoresistors are tested and compared in the same manner.Figure 5. Three photoresistors installed on PVFigure 6 shows the flowchart algorithm of the trackersystem. When the system is started the output values of thesensors will be compared together in order to locate the lightdirection. If the output of the sensor X is greater than that ofsensor O then the system will deviate toward X, the systemwill rotate in the x-y plane, in order to reach a value where thetwo sensors have nearly the same output voltage.The same operation is done for the z-plane, as the sensor Oand X have a similar output voltage then, a comparison withthe Y sensor will allow the system to rotate in the z- plane.Using this method the tracker will have the sun position. Thisposition will be updated each time a variation will occurs inthe outputs of the sensors , the time of updating the track canbe regulated (knowing that the deviation of the sun will notoccurs each second ), so a period time can be added once thesystem is in stable position in order to reach the second stableposition .The benefit of the smart tracker is that allows a preciseposition of the sun light. The sun direction is measured in athree axis diagram (position and angle). The information thatthe tracker will detect will be sent to different systems that hasthe same functionality (that rotates following the solar rays toreduce the power consumption of the system).IV. SPECIFICATIONS AND PRIMARY RESULTSA. SpecificationsIn order to demonstrate the efficiency of the proposedsystem, a control algorithm is generated as shown in table 1.TABLE I. CONTROL ALGORITHMStep # Action1 Install the small PV2 Put PV in initial position (0,0,0)3 Find the maximum sun light, using the photoresistors, and savethe position of the PV4 Measure the current (I)5 If I < threshold value (minimum current); wait for 30 minutes andgoto step 3, otherwise goto step 66Turn PV left for 3.5°, measure the current; if it is greater then theprevious current continue turning left until finding the maximumcurrent in x and y axis; Otherwise turn right and do the same.After finding the maximum current turn up or down to get themaximum current in z-axis, and wait for 45 minutes.7 Send the coordinates (x,y,z) to the heater or large panels wired orwireless.8 Goto step 3B. Preliminary ResultsIn order to assess the efficiency of the proposed system,some measurements were taken during a sunny summer day.Table 2 shows the comparison between the maximum currentusing a fixed Photovoltaic panel (PV) and using the proposedsystem at different times.TABLE II. COMPARISON OF THE CURRENT BETWEEN FIXED PV ANDUSING THE PROPOSED SYSTEMTime Current using a fixed PV(Amp)Current using theproposed system (Amp)8:00 AM 0.42 0.859:00 AM 0.55 0.9010:00 AM 0.75 0.9211:00 AM 0.81 0.9512:00 PM 0.92 0.991:00 PM 0.95 0.992:00 PM 0.88 0.993:00 PM 0.76 0.984:00 PM 0.42 0.955:00 PM 0.23 0.956:00 PM 0.15 0.927:00 PM 0.08 0.728:00 PM 0.01 0.25Total 6.93 11.36.The efficiency of the proposed system can be calculatedusing the equation (1):%92.6393.6100*)93.636.11(=−=Efficiency (1)It seems that the efficiency of the proposed system can beincreased around 64% on a summer sunny day. In addition,the proposed system consumes little power to turn the PVpanel using a small stepper motor instead of using large panelwhich consumes larger amount of power . Moreover, thissystem can power itself from the PV panel using a 12 voltbattery.V. CONCLUSIONIn this paper a universal multi-function solar trackersystem is reported. The proposed system was implemented inreduced complexity architecture such as a microcontroller.The control system which is the brain of the proposed systemis used to turn a small PV panel in three directions todetermine the maximum output current.Three photoresistors are used every 45 minutes to redirectthe PV panel to het the nearest value of the maximum sun.
Figure 6. Flowchart algorithm of the tracker systemACKNOWLEDGMENTThe authors would like to acknowledge the financialsupport from faculty of Engineering of NDU.REFERENCES A. Zahedi, “Energy, People, Environment, Development of an integratedrenewable energy and energy storage system, an uninterruptible powersupply for people and for better environment,” The InternationalConference on Systems, Man, and Cybernetics, 1994. Humans,Information and Technology, Vol. 3 pp. 2692-2695, 1994. R. Singh, and Y.R. Sood, “Transmission tariff for restructured Indianpower sector with special consideration to promotion of renewableenergy sources”, The IEEE Conference TENCON-2009, pp. 1-7, 2009. J. Arai, K. Iba, T. Funabashi; Y. Nakanishi, K. Koyanagi, and R.Yokoyama, “Power electronics and its applications to renewable energyin Japan, ” The IEEE Circuits and Systems Magazine, Vol. 8, No. 3, pp.52-66, 2008. S. Takemaro and Shibata Yukio, “Theoretical Concentration of SolarRadiation by Central Receiver Systems,” The International Journal ofSolar Energy, 261-270, 1983. S. Armstrong and W.G Hurley “Investigating the Effectiveness ofMaximum Power Point Tracking for a Solar System”, The IEEEConference on Power Electronics Specialists, pp.204-209, 2005. O. Aliman, and I Daut, “Rotation-Elevation of Sun Tracking Mode toGain High Concentration Solar Energy”, The IEEE InternationalConference on Power Engineering, Energy and Electrical Drives,pp.551-555, 2007. A.K. Saxena and V. Dutta, “A versatile microprocessor- based controllerfor solar tracking”, IEEE Proc., 1990, pp. 1105 – 1109. E. Karatepe, T. Boztepe, and M. Colak, “Power Controller Design forPhotovoltaic Generation System under Partially Shaded InsolationConditions”, The International Conference on Intelligent SystemsApplications to Power Systems, pp. 1-6, 2007. N. Barsoun, “Implementation of a Prototype for a Traditional SolarTracking System”, The Third UKSim European Symposium onComputer Modeling and Simulation, pp. 23-30, 2009. C. Jaen, J. Pou, G. Capella, A. Arias, and M. Lamich, M, “On the use ofsun trackers to improve maximum power point tracking controllersapplied to photovoltaic systems”, The IEEE conference on Compatibilityand Power Electronics, pp. 67-72, 2009.