Design and Implementationof PV System Tracking by...

IPASJ International Journal of Electrical Engineering (IIJEE) Web Site: http://www.ipasj.org/IIJEE/IIJEE.htm

A Publisher for Research Motivation........ Email: [email protected] Volume 3, Issue 8, August 2015 ISSN 2321-600X

Volume 3, Issue 8, August 2015 Page 6

ABSTRACT This paper presents an automatic dual axis sun tracking system based PIC 16F877A microcontroller which is programmed by flow code. The tracker uses four LDR (Light Dependent Resistor) to sense the position of the sun. Microcontroller order the stepper motor and DC motor to rotate dependent on the voltage difference among the four LDR detectors. The stepper motor moves the PV panel in the horizontal direction from east to west while the DC motor moves the PV in the vertical direction. The practical results show that the overall output energy of tracking PV panel is increased by 20%. Keywords: Sun Tracking, Microcontrollers, PV, LDR, Stepper motor, DC motor. 1. Introduction The output power produced by the PV panels depends strongly on the incident light radiation. The continuous modification of the sun-earth relative position determines a continuously changing of incident radiation on a fixed PV panel. The point of maximum received energy is reached when the direction of solar radiation is perpendicular on the panel surface. Thus an increase of the output energy of a given PV panel can be obtained by mounting the panel on a solar tracking device that follows the sun trajectory [1]. Solar tracking strategies are several types and can be classified according to several criteria. One of them, A classification of solar tracking systems can be made depending on the orientation type. According to this criterion, we can identify solar tracking systems that orient the PV panels based on a previously computed sun trajectory, in comparison with panels with an on-line orientation system that reacts to the instantaneous solar light radiation. The later solution is simpler to achieve than former and it was chosen for the solar tracking system proposed in this paper. This paper deals with the design and execution of a solar tracker system dedicated to the PV conversion panels. The results from daily analyses show, as expected, that in clear days the dual axis tracker PV system provides the highest performance. The results indicated that a solar tracking system with photo-sensor is the optimum system and base on this result we can verify possibility to apply large scale system. Compared to a fixed panel, with tracker PV panel driven by a solar tracker is kept under the best possible irradiation for all positions of the Sun, as the light falls close to the geometric normal incidence angle. Automatic solar tracking systems (using light intensity sensing) may boost consistently the conversion efficiency of a PV panel, thus in this way deriving more energy from the sun. 2. Sun positions and module tracking. As depicted in Figure 1, the position of the sun with respect to that of the earth changes in a cyclic manner during the course of a calendar year. Tracking the position of the sun in order to expose a solar panel to maximum radiation at any given time is the main purpose of a solar tracking PV system[2].

Figure 1(a) Illustration of the summer and winter solstices

Design and Implementationof PV System Tracking by Microcontroller

Aref Y. Eliwa1, Emad A. Sweelem2

1Electronics Research Institute,El-Tahrir St., Dokki, Cairo, Egypt.

2Electronics Research Institute,El-Tahrir St., Dokki, Cairo, Egypt.




Figure 1 (b) Sun Path Diagram for 400 N Latitude During Winter and Summer Solstices.

For many years, several energy companies and research institutions have been performing solar tracking for improving the efficiency of solar energy production. A variety of techniques of solar energy production used have proven that up to 30% more solar energy can be collected with a solar tracker than with a fixed PV system1. The cost of such systems is however still very prohibitive for the average consumer or for a small-scale application. The current work shows that a comparable system can be designed at a much lower cost particularly for academic institutions. In addition, the solar trackers currently available are generally not programmable for location flexibility. Moving a system from the northern hemisphere to the southern hemisphere, coupled with latitudinal and longitudinal position changes, can result in considerable design changes to the tracker’s control circuitry. A typical solar tracking PV system must be equipped with two essential features: a) Azimuth tracking for adjusting the tilt angle of the surface of the PV array during changing seasons; and b) Daily solar tracking for maximum solar radiation incidence to the PV array. The Tilt Angle θ (as shown in Figure 2) of a PV system required at any given time in the year can be expressed as afunction of the seasonal Sun’s Altitude φ as follows [3,4]: Tilt Angle θ = 90 – φ

Figure 2 Tilt Angle θ of a PV array

3. PV Tracking System Design The dual axis tracking technique is design [5,6]to track the sun in both azimuth and altitude angles to enable the PV panel perpendicular to the illumination of the sun: i-The PV panel used in this system amorphous silicon solar cell, the maximum output power is 60W, open circuit voltage is 22V, short circuit current is 3.4A and its dimensions 315*925 mm and its weight 7.1 Kg (Figure 3)




Figure 3 PV panel.

ii- The mechanical mechanism as shown in Figure 4 includes a stepper motor and DC motor. The system consists of PV panel, frame, stepper motor, DC motor, sensor circuit and driver circuits.

Pv module support

Figure 4 PV tracking mechincal mechanism. a- Stepper Motor. Stepper motors (Figure5)[7] provide a means for precise positioning and speed control without the use of feedback sensors. The basic operation of a stepper motor allows the shaft to move a precise number of degrees each time a pulse of electricity is sent to the motor. Since the shaft of the motor moves only the number of degrees that it was designed for when each pulse is delivered, you can control the pulses that are sent and control the positioning and speed. The rotor of the motor produces

Figure5 Stepper Motor used

torque from the interaction between the magnetic field in the stator and rotor. The strength of the magnetic fields is proportional to the amount of current sent to the stator and the number of turns in the windings. The stepper motor uses the theory of operation for magnets to make the motor shaft turn a precise distance when a pulse of electricity is provided. You learned previously that like poles of a magnet repel and unlike poles attract. Fig 6 shows a typical cross-sectional view of the rotor and stator of a stepper motor. From this diagram you can see that the stator (stationary winding) has eight poles, and the rotor has six poles (three complete magnets). The rotor will require




24 pulses of electricity to move the 24 steps to make one complete revolution. Another way to say this is that the rotor will move precisely 15° for each pulse of electricity that the motor receives. The number of degrees the rotor will turn when a pulse of electricity is delivered to the motor can be calculated by dividing the number of degrees in one revolution of the shaft (360°) by the number of poles (north and south) in the rotor. In this stepper motor 360° is divided by 24 to get 15°. When no power is applied to the motor, the residual magnetism in the rotor magnets will cause the rotor to detent or align one set of its magnetic poles with the magnetic poles of one of the stator magnets. This means that the rotor will have 24 possible detent positions. When the rotor is in a decent position, it will have enough magnetic force to keep the shaft from moving to the next position. This is what makes the rotor feel like it is clicking from one position to the next as you rotate the rotor by hand with no power applied.

.

Figure6 Diagram that shows the position of the six-pole rotor and eight-pole stator of a typical steppermotor

Stepper Motor Advantages[8]: 1. The rotation angle of the motor is proportional to the input pulse. 2. The motor has full torque at standstill (if the windings are energized) 3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 – 5% of a step

and this error is non-cumulative from one step to the next. 4. Excellent response to starting/stopping/reversing. 5. Very reliable since there are no contact brushes in the motor. 6. Therefore the life of the motor is simply dependent on the life of the bearing. 7. The motors response to digital input pulses provides open-loop control, making the motor simpler and less costly to

control. 8. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft. 9. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.

The center taps are connected to a positive voltage while the coil ends are alternately grounded to cause a reversal of the field direction in that winding and Phase motor. The number of phases is equal to two times the number of coils. The motor is rotated by applying power to the windings in a sequence as shown in table 1.




Table 1: Four positions of stepper motor operation. S1 S2 S3 S4 Result

1 0 0 1 Motor moves

right

0 1 1 0 Motor moves left

0 0 0 0 Motor free runs

0 1 0 1 Motor brakes

1 0 1 0 Motor brakes

1 1 0 0 Shoot-through

0 0 1 1 Shoot-through

Figure7 Bridge drives motor.

An H bridge (Figure7) is built with four switches (solid-state or mechanical). When the switches S1 and S4 (according to Figure7) are closed (and S2 and S3 are open) a positive voltage will be applied across the motor. By opening S1 and S4 switches and closing S2 and S3 switches, this voltage is reversed, allowing reverse operation of the motor. Using the nomenclature above, the switches S1 and S2 should never be closed at the same time, as this would cause a short circuit on the input voltage source. The same applies to the switches S3 and S4. This condition is known as shoot-through Operation

Figure8 The two basic states of an H bridge




The H-bridge arrangement (Figure8) is generally used to reverse the polarity of the motor, but can also be used to 'brake' the motor, where the motor comes to a sudden stop, as the motor's terminals are shorted, or to let the motor 'free run' to a stop, as the motor is effectively disconnected from the circuit. b- DC motor A DC motor [8] used in this work to move the pv panel in azimuth direction is shown in Figure9 and disk drives, or in large sizes to operate steel rolling mills and paper machines. Modern DC motors are nearly always operated in conjunction with power electronic devices.

Figure9 DC motor used.

c- LDR A photo resistor or light dependent resistor (Figure10a) [9,10]is a component that is sensitive to light. When light falls upon it then the resistance changes. Values of the resistance of the LDR may change over many orders of magnitude the value of the resistance falling as the level of light increases (Figure10b). It is not uncommon for the values of resistance of an LDR or photo resistor to be several megohms in darkness and then to fall to a few hundred ohms in bright light. With such a wide variation in resistance, LDRs are easy to use and there are many LDR circuits available (Figure10c). LDRs are made from semiconductor materials to enable them to have their light sensitive properties. Many materials can be used, but one popular material for these photo resistors is cadmium sulphide (CdS).

(a) LDR photo. (b) LDR circuit.

(c) Variation of resistance with light.

Figure10 LDR sensor




4. Experimental Work and System Tracking Circuit The solar panel is moved in two axis by The Light Detector Resistance LDR are mounted on the solar panel. This senses the position of the sun with respect to the position of the photovoltaic panel.The tracker should be has microprocessor controlled, to be able to calculate optimum sunlight position and drive the motors in order to position the photovoltaic panel directly to the optimum sunlight. To control the tracker and solar movement, PIC 16877A were used by using the C programming language. The block diagram of the system is shown in Figure11. This research is designed with solar panels, LDR, Microcontroller, DC Motor and stepper motor and its driving circuit as shown in Figures 12&13.

Figure11 The block diagram of PV system tracker

Figure12 Stepper Motor Driving circuit




Figure13 DC motor Driving Circuit

In this research LDR are fixed on the solar panel at a distinct point. LDR varies the resistance depending upon the light fall. The varied resistance is converted into an analog voltage signal. The analog voltage signal is then fed to an Analogue to Digital Converter ADC inside the PIC 16F877A. ADC is nothing but analog to digital converter which receives the LDR voltage signals and converts them to corresponding digital signal. Then the converted digital signal is given as the input of the microcontroller. Microcontroller receives the digital signals from the ADC and compares them. The LDR signals are not equal except for normal incidence of sunlight. When there is a signal at LDR voltage levels the microcontroller program drives the DC or stepper motor towards optimal incidence of sunlight. The voltage regulator module is used to protect PIC and other connected sensors / actuators from over voltage. This is because PIC and all other connected sensors, actuators all support 5V DC only. Over voltage will cause any of the module burn. The practical circuit drivers and Thepv tracker is shown in Figures 14&15.

Figure14 The practical circuits of circuit drivers




Figure15Photo of two axis tracking system.

5. Flow Chart Of the Control Circuit The flow chart of the control system is shown in Figure 16. If the difference between the value of LDR1 and LDR4 is less than a certain value (e), the microcontroller generates no control signals because that means that the PV panels are perpendicular to the source light. When the difference between LDR1 and LDR4 is more than (e), the microcontroller generates control signals to drive stepper motor 1 to the left. When the difference between LDR4 and LDR1 is more than e, the microcontroller generates control signals to drive stepper motor 1 to the right [1][4]. The same test is done for LDR2 and LDR3 in order to control DC motor 2 up and down. The system is programmed so that after sunset the PV panels are directed to east waiting the sunrise. The microcontroller has been programmed using Flow code software.

Figure 16 Flow chart of the control system.




6. Result The output power versus time characteristic is shown in Figure17, indicate that there is an overall increase of output energy about 20% for the two axis sun tracking system compared to the fixed PV system as shown in Figure18. The tracking mechanism is capable of tracking the sun according to the direction of beam propagation of solar radiation and it has a provision in the software for adjustment of the system in case of seasonal variation if necessary. The power consumption by the system is very low because of low energy consumption devices are used like as COMS digital IC’s and other low power consuming solid state electronic components. Also, consumes a small amount of energy because it rotates only for a fraction of every interval of time.

Figure17 Power-TIME variation comparison of fixed and tracking system.

Figure 18 Energy variation comparison of fixed and tracking system.

7. Conclusion This paper introduced the design and implementation of PV system sun tracking using microcontroller. Sun tracking system allows the pv panel perpendicular to the sun light. To minimize the energy consumption due to the panel movement, the microcontroller test the output voltage difference of LDR’s sensors every a constant time (about half hour) and sent pulse to the drivers circuit of the motors. The output energy reported for tracking system is about 20 % over the that for fixed pv panel.




References [1] Byeong-Ho Jeong, Ju-Hoon Park, Seung-Dai Kim, Jong-Ho Kang, “Performance Evaluation of Dual Axis Solar

Tracking System with Photo Diodes”, 2013 International Conference on Electrical Machines and Systems, Oct. 26-29, 2013, Busan, Korea.

[2] http://wattsun.com/resources.html. [3] XC95108 properties at http://xilinx.com/xlnx/xil_prodcat_product.jsp?title=xc9500_page [4] Xilinx ISE 8.1i Foundation in depth tutorial at http://www.xilinx.com/ise/logic_design_prod/foundation.htm. [5] OkamBingol, Ahmet Altintas, YunusOner, “Microcontroller based solar-tracking system and its implementation”,

Journal of Engineering Sciences, Vol 2, No. 12, pp. 243-248, 2006. [6] M.R.I. Sarker, Md. Riaz Pervez and R.A. Beg, “Design, fabrication and experimental study of a novel two-axis sun

tracker”, International Journal of Mechanical and Mechatronics Engineering IJMME-IJENS , Vol. 10, No. 01, 2010.

[7] Nasir Ahmed Filfil, DeiaHalbootMohussen and Dr. Khamis A. Zidan, “Microcontroller based sun path tracking system”, Eng. And Tech. Journal , Vol. 29, No. 07, 2011.

[8] Jing-Min Wang and Chia-Liang Lu, “Design and implementation of a sun tracker with adDual-axis single motor for an optical sensor-based photovoltaic system”, Sensors, pp. 3157-3168, 2013.

[9] Mohammad Shoaib, V.Nagaraj, “Proteus based simulation of PV inverter for rural electrical Service”, International Journal of Modern Engineering Research (IJMER), Vol 3,Issue 2 No. 1, pp. 1212-1219, 2013.

[10] M. Anish John Paul, “Design and performance analysis of automated two axis solar tracking system for steam generation”, international conference on energy efficient technologies for sustainability, IEEE, Vol--,Issue -- No. --, pp 432-437, 2013.

[11] Marwan Mahmud, “Solar electric powered ROBrackish water desalination system in Palestine”,Proceedings of the 3th international conference onenergy and environmental protection insustainable development, Hebron, Palestine,pp 124-132, 9-10October2013.

AUTHOR

A. Y. Eliwa: I had born in Cairo on Sept. 1964. June 2000, Ph.D was awarded from , Faculty of Engineering, Ain Shams University in the field of solar cells technology. Bachelor of Electrical Engineering, (very good with honor degree) from Faculty of Engineering (Shoubra), Zagazig University (May 1987). Since 1989 , I'm working at Electronics Research Institute, PV Department in the field of Technology and Applications of Solar. I shared in some projects ; "“New Antireflection Coating Material for Solar Cells" 1992-1997, "Design and Implementation of an Optimum Solar Pumping System”, 1996-1998, “Study and Selection of the Available Technology

for Mass Production of Solar Cell Modules” Final report 1996-1998, “Researches in the Technology of Production of Electronic Components”, 1998-2002.

E. A. Sweelem: I had born in Cairo on Aug. 1969. Feb. 2003 PhD in Electrical Engineering, Cairo University, EgyptThesis: A New Development for Modeling and Control of PV Hybrid Energy System. A Government Fellowship in Cottbus-Germany (Technical University of Cottbus), where the experimental part of my PhD were done there (from 18/11/2000 to 17/11/2002). Nov. 1997 M.Sc. in Electrical Engineering Cairo University, Egypt Thesis: A Modified Air Cooling for Photovoltaic System. A Scholarship from DAAD(German Authority) in Kassel-German (Solar Energy Institute ISET), Where experimental part of my M.Sc. were done there (from 1/11/1995 to 31/12/1996). July 1991 B.Sc. in Electrical Engineering Cairo University, Egypt Grade: very good with honors Graduation project grade: distinction. I am working now in

Electronics Research Institute, PV Department and my position is Researcher Since 2003 till now. I have published more than 14 papers in the field of solar cells and take shared in more than 5 research projects.

Date post:	28-Mar-2018
Category:	Documents
Upload:	ngokhanh
View:	212 times
Download:	0 times

Design and Implementationof PV System Tracking by...

Documents