Performance Evaluation of Solar Panel and Proposed New Algorithm of Solar Tracking System Al Jumlat Ahmed
Shougat Nazbin Khan
Centre for Green Energy Technology Pondicherry University Pondicherry, India
[email protected]
Centre for Green Energy Technology Pondicherry University Pondicherry, India
[email protected]
Abstract— The output of a Solar Panel is highly dependent on solar radiation and other climatic conditions. Performance evaluation shows a solar panel can generate output power above 60% of its rated value for only six hours of a day from 9.00 am to 3.00 pm in Pondicherry, India. Based on the performance evaluation, we have proposed a new algorithm for timer based solar tracking system to harvest more sunlight by solar Panel. Keywords- solar panel; performance evaluation; harvesting sunlight; new algorithm; solar tracking system
I.
INTRODUCTION
Solar cell is a photovoltaic (PV) device which converts sunlight into electricity and a solar panel is array of identical solar cells connected in series [1]. Solar panel is been rated at standard test condition (STC): 1000 w/m2 solar radiation, 250C cell temperature and 1.5G air mass [1] which means a solar panel can give rated power output only at STC. The power output of a solar panel strongly depends on the solar radiation falling on it. And due to the variation of solar radiation, the power output of a solar panel also changes throughout the day. In order to maximize the amount of sunlight harvested by a solar panel, the panel needs to track the sun position throughout the day. A single axis tracking system which rotates around the vertical axis with movement in east-west direction can increase the power output of solar panel by 20% compared to a solar panel having fixed position facing toward north or south with a tilt angle equal to the local latitude angle [2]. There are mainly two different types of controlling mechanism used in the solar tracking system: Sensor based controlling mechanism and Timer based controlling mechanism. In the sensor based controlling system different light sensors like LDR, small sized solar cells are used to detect the position of the sun and to give signal to the microcontroller [2]. But in the timer based controlling system the solar panel moves from east to west with a constant angle in regular interval. Sensor based system is more accurate but the timer based system is robust and free from environmental effect.
II.
PERFORMANCE EVALUATION OF SOLAR PANEL
Performance evaluation has been done of a 75W p mono crystalline solar panel manufactured by Bharat Heavy Electronics Limited (BHEL). The model number is BE75S12, Open circuit voltage (Voc) is 21.6V and Short circuit current (Isc) is 4.87A [3]. The solar radiation data has been measured by a digital radiation recorder and the model number of pyranometer is LP PYRA 03 manufactured by Delta Ohm [4]. Experiment has been done in Pondicherry University Campus and geographical location of Pondicherry University is 12o01’35.02’’ N and 79o 50’ 57.91”E. The average solar radiation (W/m2) and power output (W) of solar panel from 6.00 AM to 5.00 PM of a week are tabulated in TABLE 1. It is noticeable from the table that the panel gives reasonable power output when solar radiation is 488.98 W/m2 or more and the power output is 47W or more from 9.00 AM to 3.00 PM. Remaining of the day, power output of solar panel is very low. TABLE I AVERAGE SOLAR RADIATION DATA AND SOLAR PANEL OUTPUT Time
Solar Radiation (w/m2)
Solar Panel Output (W)
6:00:00
46.42
0.08
7:00:00
175.17
2.76
8:00:00
351.39
3.7
9:00:00
537.94
47
10:00:00
737.21
50.22
11:00:00
818.94
58.328
12:00:00
835.96
57.83
13:00:00
828.78
57.739
14:00:00
666.07
55.874
15:00:00
488.98
49.776
16:00:00
304.29
12.456
17:00:00
102.55
11.937
The performance evaluation shows that a 75W p solar panel can generate power output above 60 % of its rated value for only six hours in a day due to low solar radiation in remaining hours of the day. III.
can be harvested by the solar panel in an effective way. Algorithm of the solar tracking program is shown in Fig. 2. From 6.00 AM To 9.00 AM
NEW ALGORITHM OF SOLAR TRACKING SYSTEM
Panel position will be fixed at -45o Position
o
Observing the sun from earth, sun rotates 15 in one hour from east to west which is called solar hour angle [5]. At 12.00 PM, when sun is at the zenith point, the hour angle is zero degree. For morning hours, solar hour angle is negative and for afternoon hours, the angle is positive. For example: At 10 AM, the hour angle is -30o and at 2.00 PM, the hour angle is +30o.
From 9.00 AM To 3.00 PM Panel will rotate from -45o to + 45o (15o degree in one hour)
If the solar panel can be rotated 15o in each hour from east to west it will follow the posion of the sun and sun ray will be always perpendicular to the panel. Consequently more sun light will be harvested and the output of the panel will be higher compared to a solar panel having fixed position facing toward north or south with a tilt angle equal to the local latitude angle. It has already been proven that solar tracking system can increse the ouput power of solar panel by approximately 20% [2]. The sun position, hour angle and relative position of solar panel are shown in Fig. 1.
From 3.00 PM To 6.00 PM Panel position will be fixed at +45o Position
After 6.00 PM Panel will back to -45o position Figure 2. Algorithm of solar tracking program
The block diagram of the solar tracking system is shown in Fig. 3. The solar panel is coupled with a stepper motor which is controlled by an electrical control circuit connected as load to the charge controller. Charge Controller
Battery
Control PPPPPP popppp PPPPpP thPPPP Ppanelth
Solar Panel
Bipolar Stepper Motor
Electrical Control Circuit
Load
Figure 3. Block diagram of solar tracking system Figure 1. Sun position, hour Angle and relative position of solar panel
The performance evaluation shows the panel output is very low during 6.00 AM to 9.00 AM and from 3.00 PM to 6.00 PM due to low solar radiation. But to follow sun position during these time periods, the tracker needs more energy because of the panel position. For this reason, the proposal of this paper is to track the sun position from 9.00 AM to 3.00 PM because solar radiation is high during this section of day. From 6.00 AM to 9.00 AM, the panel will be fixed at -45o position and again it will be fixed at +45o position from 3.00 PM to 6.00 PM. By this new algorithm of timer based solar tracking system, more sun light
IV.
PROTOTYPE OF THE TRACKING SYSTEM
A prototype of solar tracking system has been developed based on proposed algorithm as shown in Fig. 4. In this prototype, ATmega16L microcontroller of Atmel has been used in the controller circuit to generate the input signal at specific time interval to drive the stepper motor with help of diver circuit.
Distance, Required Torque,
d= 0.125 m T= 2x9.8x0.125 = 2.45 Nm
Stepper motor with rated torque of 3Nm has been chosen to rotate the panel around the vertical axis as shown is Fig. 4. C. Stepper Motor and Driver Circuit Bipolar stepper motor with 12V operating voltage, 1.8o step size and 4 wire configuration has been operated in full wave mode and been coupled with solar panel by a rubber belt as shown in Fig. 2. The rated torque of the motor is 3 Nm. The motor has been driven by a L298N IC as shown is Fig. 6 [8]. The biasing voltage of the driver circuit is 12 V and operating current is 0.1 A [6].
Figure 4. Prototype of single axis solar tracking system
A. Microcontroller Based Control Circuit ATmega16L is an 8 bit microcontroller with 16K byte in system programmable flash memory [7]. It has been operated in 8 MHz by external crystal and first four pins of Port C have been used as output pins connected to stepper motor driver circuit. The operating voltage of controller circuit is 5V and power consumption is 5.5 mW at active mode [6]. The schematic of the control circuit is shown in Fig. 5.
Figure 6. The electrical control circuit of solar tracking system
D. Step Size of the Stepper Motor Step size of the stepper motor is 1.8o which means in one step it can rotate 1.8o in clockwise or anti clockwise direction. To rotate a solar panel 15o in one hour, it has been seen from calculation that the panel should rotate single step (1.8o ) in every 7.2 min. In total, the panel has to rotate 90 o (from -45o to +45o ) in 6 hour by 50 steps from 9.00 AM to 3.00 PM. And remaining of the day, the panel has to be in fixed position. After 6.00 PM the panel has to back at -45o position and to wait for next 15 hour till 9.00 AM of the next day. From 9.00 AM of the next day, the same routine has to be followed. E. Cost Calculation Cost of different components have been used in the prototype system is listed in Table II. Components have been collected from the local market. Total cost of the system is 3206 INR. Figure 5. Schematic of the control circuit
B. The required torque calculation To rotate the solar panel by a stepper motor, the rated torque of motor should be higher than the required one. Calculation of required torque is, Weight of the panel, m= 2 Kg
TABLE II. COST OF DIFFERENT COMPONENTS OF THE SOLAR TRACKING SYSTEM Component Price (INR) 2000 Mechanical Structure Stepper Motor 500 Microcontroller 280 L298N IC 350 Electrical Components 76 Total 3206
V.
CONCLUSIONS
The performance evaluation has shown that a solar panel can generate 60% of its rated power output for only six hours of a day in Pondicherry, India. Performance of solar panel is highly dependent on local climatic conditions like solar radiation. An indigenous algorithm of solar tracking system has been proposed so that the solar panel can harvest more sunlight in an effective way and a prototype of the solar tracking system has been developed for further study. ACKNOWLEDGMENT We would like to express our sincere gratitude to Dr. Prasanth Ravindran for his invaluable suggestions and support. We are grateful to Center for Green Energy Technology, Pondicherry University for providing laboratory facilities to carry out the experiments. REFERENCES [1]
[2]
[3]
[4] [5] [6] [7] [8]
Chetan Singh Solanki, Solar Photovoltaics: Fundamentals, Technologies and Applications , New Delhi, India: PHL Learning Pvt. Ltd.,2009 Barsoum Nader and Vasant Pandian, “Simplified Solar Tracking Phototype,” Global Journal on Technology & Optimization, Vol.1, p. 38-45, 2010 Shougat Nazbin Khan, “Modeling and Performance Analysis of PV Module for Standalone Systems,” M.Tech thesis, Pondicherry University, Pondicherry, India, Dec 2013 Pyranimeter (LP PYRA 03), Delta Ohm (2014) The Wikipedia Website. [Online].Available: http://en.wikipedia.org/wiki/Hour_angle Al Jumlat Ahmed, “Single Axis Timer Based Solar Tracking System,” M.Tech thesis, Pondicherry University, Pondicherry, India, Dec 2012 “ATmega16L datasheet,”AVR Microcontroller, Atmel Corporation, USA “L298N datasheet,” Dual Full-Bridge Driver, STMicroelectronics
