Comparison of Single and Dual Axis Tracker Controlled with Fixed Tilt Solar PV System in Pakistan

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1 Comparison of Single and Dual Axis Tracker Controlled with Fixed Tilt Solar PV System in Pakistan 1 Tallal Ahmed*, 1 Waqas Khalid, 2 Imran Ali Shah 1 Center for Energy Research and Development, University of Engineering & Technology Lahore Pakistan 2 Alternate Energy Research & Innovation Lab, Al-Khawarizmi Institute of Computer Science, University of Engineering & Technology Lahore, Pakistan * engr.ahmedtallal@gmail.com Abstract In this study performance comparison of single axis and dual axis tracker controlled solar photovoltaic power system (PV-SPS) is done with fixed tilt PV-SPS. All three systems were simulated in grid connected configuration with identical power rating of 2.0 kwp and same modules and inverters. Fixed tilt and single axis tracker controlled PV-SPS were also physically implemented and results were recorded for complete one-year operation while the dual axis tracker controlled PV-SPS is simulated and results for a complete year are estimated. An averaged 4.5% difference in simulated and estimated energy values is observed and considered for estimation of dual axis tracker controlled PV-SPS results. Keywords Photovoltaic; single axis; dual axis; fixed tilt; solar tracker; PV performance; PVsyst I. INTRODUCTION Energy is an essential part of our fast-growing economies. There are numerous energy resources. Human beings started to extract energy from fossil fuels but growing population and increasing demands in energy has led to increase in fuel prices accordingly and depletion of fossil fuels [1]. Greenhouse gases (GHGs) concentration has become a major environmental concern, emissions from fossil fuel burning contains a major content of carbon dioxide (CO 2 ) which contributes to GHGs [2]. To reduce the consumption of fossil fuels utilized in thermal power pants alternate energy resources are being developed and implemented widely. With growing increase in energy demand and rapidly depleting fossil fuels the energy resources must be renewable and sustainable [3,4,5]. Solar energy is one of the cleanest renewable source of energy. Numerous technologies have been developed to generate electricity from solar energy. Solar photovoltaic (PV) is a widely implemented technology. Solar PV technology is simple and involves a direct conversion of sunlight to electricity without any use of engine or turbine. Solar PV system are rated in kilowatts peak (kwp), means the highest amount of power that can be generated with fully available sun. There are different types of PV systems depending on the type of load and grid configuration. Grid connected system is most common in the case of large scale PV systems. Grid Connected systems are like decentralized power generation system with an independent grid which is public electrical utility grid [6,7,8]. The system consists of many components but inverter and solar PV modules are the key components and play major role both in the solar PV solar power system s (PV-SPS) pricing and efficiency. The PV modules are affixed at such tilt angles that maximum of sunlight is incident on the module surface. But the path of sun over a specific area where modules are installed is not same throughout a year. In order to track the sun for maximum sunlight PV modules are adjusted in orientation and tilt angles. Tracker systems are being used for this purpose. Based on the direction and tilt angle following are the main types of PV-SPS. A. Fixed Tilt System PV modules are oriented to collect maximum possible sunlight. The PV modules are tilted perpendicular to the sun rays for maximum efficiency. Since the angle of sun varies all year so the tilt angel is different for summer and winter. Increasing the tilt angle increases energy generation in winter and decreasing the tilt angle is increases energy generation for summer season. PV modules in fixed tilt system are tilted at a fixed angle which is calculated as an optimum angle for the whole year [9,10,11]. Figure (1) shows a PV module oriented toward south and tilted at fixed angle. Figure (1). PV module at fixed tilt (facing South) Reference Number: JO-P

2 B. Single Axis and Dual Axis Tracker System Tracker controlled PV systems are installed to track the sun by changing the orientation all day making sure that maximum energy is absorbed by the PV modules. The power consumption of tracker systems is 2-3% of the increased output [12]. There are two main types of solar trackers, single axis and dual axis tracker. Single axis solar trackers can rotate in one direction on one fixed axis. Depending on the rotation there are different types of single axis trackers such as tilted, horizontal, vertical and polar aligned. Figure (2) shows a single axis tracker on a tilted axis. This study is conducted to evaluate the performance of single axis and dual axis tracker controlled PV systems in Pakistan. There is a growing trend of renewable energy especially solar energy in Pakistan. Currently the solar industry evaluates the success of the project in terms of its price per kwp. At present the tracker controlled PV systems are higher in cost than the conventional fixed tilt PV systems; and recent reduction in prices mainly PV modules the economical gain energy by the implementation of tracker controlled systems is questionable [21]. The aim of this study is the detailed comparison of single axis and dual axis tracker controlled system with fixed tilt PV- SPS in terms of annual energy generation. Figure (2). South oriented single axis tracker system Dual axis solar trackers are capable of moving in both directions vertically and horizontally and hence generating more output power as compared to single axis tracker systems. The dual axis tracker system is designed in such a manner that the it always faces the sun and sunlight is incident to the collector s surface [13,14,15,16]. A dual axis solar tracker system is shown in Figure (3). II. METHODOLOGY This study is in continuation of our previous study on single axis tracker controlled PV system with fixed tilt PV system. A detailed energy and economic analysis of single and tracker controlled PV system was performed by both simulation and actual physical installation [22]. This study is done in a similar way but currently only system is designed theoretically and simulation are performed. The simulation results are compared with the previous conducted study and feasibility of practical implementation is evaluated. A. PV System Type and Rating A 2kWp grid connected photovoltaic system is selected for this study. 8 modules each 250 Wp from Hanwha Q cells and 2.0 kwac Sunny Boy inverter form SMA is used. The specifications of PV module and inverter are mentioned in Table I and Table II respectively TABLE I. PV MODULE SPECIFICATIONS UNDER STC Figure (3). Dual axis tracker system Selection of tracker system depends on various factors mainly geographical condition of the selected site, utility tariffs, system type, system size and weather. Horizonal axis solar trackers are suitable for utility and large-scale projects and vertical axis tracker system are favorable for high latitudes. Dual axis trackers are favorable in the regions with high Fee- In-Tariffs by government. Single axis tracker system perform more than fixed tilt solar systems and dual axis tracker systems generates even more energy than single axis tracker. The performance varies for different type of systems and operation environments [17,18,19,20,21]. Electrical Characteristics Units Value PV module Rated Power W 250 Average Power Pmpp W Short Circuit Current Isc A 8.94 Open Circuit Voltage Voc V Current at Pmpp Impp A 8.45 Voltage at Pmpp Vmpp V Efficency (Nominal Power) h % 15 TABLE II. 2.0 kwac SMA SUNNY BOY INVERTER SPECIFICATIONS Electrical Characteristics (Input DC) Units Value Max DC Power W 2100 Max DC Voltage V 700 MPP Voltage Range V 560 DC nominal voltage V Min. DC Voltage/ Start Voltage V Reference Number: JO-P

3 Electrical Characteristics (Input DC) Units Value Max Input Current per String A 1-2 Electrical Characteristics (Output AC) Units Value AC Nominal Power W 2000 Max AC Apparent Power VA 2000 AC Voltage Range V 220,230; AC Grid Frequency: Range Hz 50,60 : ± 4.5 Max Output Current A 11.4 A fixed tilt solar power system with the specifications mentioned above is installed, the fixed tilt angle is 32 A single axis tracker system is also installed in E-W single axis orientation [22]. The tilt limits of implemented single axis solar tracker is shown in Figure (4). Figure (6). Meteo data of site Figure (4). Horizontal Axis E-W single axis solar tracker After finding this study helpful for many projects now another study is being performed with dual axis solar tracker. The tilt limits of dual axis solar tracker are shown in Figure (5). C. Simulations Simulations are performed before every physical installation of PV-SPS. A fixed tilt and horizontal single axis EW solar tracker system was simulated using solar simulation software PVsyst 5.61 [22]. Both the systems were simulated with same electrical and geographical parameters for a complete year. The simulation results of both single axis and fixed tilt systems were compared. In this study, a simulation for dual axis tracker controller PV-SPS is performed. The simulation is performed in PVsyst The system parameters in simulation are kept same as they were in last study. The man simulation parameters are shown in Figure (7). A brief comparison of all the simulations can be found in results section of this paper. Figure (5). Dual axis solar tracker The study is based on the simulation and comparison in the output generation with single axis and dual axis system is performed. The simulations are performed to evaluate the economic viability of the dual axis tracker system in Pakistan, so that the decision of its physical implementation can be made. B. Geographical and Irradiance Data The site is located in the Khyber Pakhtunkhwa province of Pakistan. Site coordinates are 33 51'1N 72 51'8E. The detailed temperature and monthly solar hour data is already discussed in last paper [22]. The irradiation and temperature of the selected site is shown in Figure (6). Figure (7). System s Simulation Parameters D. Physical Installtions Both the fixed tilt and single axis tracker controlled PV- SPS were physically installed. Since the selected is an industrial region and there are no electrical outages in the area, so the systems are installed in grid connected mode. Gridconnection allows the system to generate the energy independent of the load variations ultimately favoring a clear and detailed study of performance in terms of energy generation. Both the systems were installed nearby with an approximate distance of 15 meters. The systems are installed on a same site as much near as possible to avoid any differences in irradiance, temperature and other weather conditions that might affect the PV generations and Reference Number: JO-P

4 performance analysis. Both systems were installed with precalibrated energy meters and daily energy generation was recorded in the computer. The systems were also periodically monitored and maintained to make sure there is no fault and conditions like dust are same for both the systems. Figure (8) shows the fixed tilt (left) and single axis tracker controlled (right) PV-SPS physical installations. Month Fixed Tilt Single Axis Tracker E_Grid (kwh) Dual Axis Tracker October November December Year Figure (8). Physical installtions of fixed tilt and E-W tracker controlled PV- SPS III. RESULTS In this study a dual axis solar tracker system is simulated and energy generation of complete year is calculated, while single and dual axis tracker PV-SPS were simulated and then physically installed. The details and analysis of both the systems is done in last study [22]. Results from last study are used for overall performance comparison of single axis and dual axis tracker with fixed tilt PV-SPS. Simulation results of all three systems are summarized in Table III. The results measured by physical installation of fixed tilt and single axis tracker PV-SPS are mentioned in Table IV. The difference in simulation and actual installation for fixed tilt PV-SPS is 5.7% and 3.3% for single axis tracker PV-SPS. Figure (9) shows a bar chart for monthly simulated and physical installation results for both fixed tilt and single axis tracker controlled PV- SPS. Actual results for both the systems are used for comparison with the dual axis PV-SPS simulated results. Month TABLE III. Fixed Tilt SIMULATION RESULTS Single Axis Tracker E_Grid (kwh) Dual Axis Tracker January February March April May June July August September Figure (9). Simulated and actual energy generated by fixed tilt and single axis tracker controlled PV-SPS. By considering difference in estimated and measured values from previous study an average 4.5% reduction in energy generation is expected when dual axis system will be physically installed and on basis of this estimated values fo for dual axis system are enlisted in Table IV. The dual axis esimated results are compared with the measured results of fixed tilt and single axis PV-SPS. Table IV shows the estimated energy that would inject in grid in case of dual axis PV SPS and measured results of energy fed to grid by fixed tilt and single axis tracker PV-SPS. The dual axis tracker PV- SPS generated 694.4kWh more enrgy than single axis tracker PV-SPS and 914.9kWh more than fixed tilt PV-SPS, while the single axis tracker system generated 220 kwh more energy in one complete year as compard to fixed tilt PV-SPS. In terms of percentage the single axis tracker PV-SPS generated 7% more energy as compared to fixed tilt PV-SPS while dual axis tracker PV-SPS generated 18% more eneryg than single axis tacker and 24% more eneryg than fixed tilt PV-SPS. Figure (10) shows performance comparison based on the monthly energy yield of PV systems for compete year. Reference Number: JO-P

5 Month TABLE IV. Fixed Tilt E_Grid (Measured) PERFORMANCE COMPARISON Single Axis Tracker E_Grid (Measured) Dual Axis Tracker E_Grid (Estimated) January February March April May June July August September October November December Year Figure (10). Performance Comparison IV. CONCLUSION In this study performance of a 2 kwp single and dual axis tracker controlled PV-SPS is compared with fixed tilt PV-SPS with identical parameters. The annual electricity yield is 2917 kwh for fixed tilt PV-SPS, 3137 kwh for single axis tracker PV-SPS and 3832 kwh for dual axis tracker PV-SPS. The single axis horizontal EW tracker PV-SPS generates 7% more energy than a fixed tilt PV-SPS with same specifications, while a dual axis tracker system generates 18% more energy than single axis tracker PV-SPS and 24% more energy than fixed tilt PV-SPS. The difference in simulated and measured values is 3.3% for fixed tilt PV-SPS and 5.7% for single axis tracker controlled PV-SPS. An averaged difference of 4.5% is considered for estimating energy yield of dual axis PV-SPS. REFERENCES [1] Dincer F. The analysis on photovoltaic electricity generation status, potential and policies of the leading countries in solar energy. Renewable and Sustainable Energy Reviews Jan 31;15(1): [2] Mondal MA, Denich M. Assessment of renewable energy resources potential for electricity generation in Bangladesh. Renewable and Sustainable Energy Reviews Oct 31;14(8): [3] Chu S, Majumdar A. Opportunities and challenges for a sustainable energy future. nature Aug 16;488(7411):294. [4] Ahmed T, Wahid A, Saad A, Paul S Development of Smart Hybrid Charge Controller, Proceeding of 1st Multi Disciplinary Student Research Conference, Wah, Pakistan, Nov 14-15, 154. [5] Photovoltaics Report, Fraunhofer Institute for Solar Energy Systems, ISE, July. [6] Branker K, Pathak MJ, Pearce JM. A review of solar photovoltaic levelized cost of electricity. Renewable and Sustainable Energy Reviews Dec 31;15(9): [7] Denholm P, Margolis RM. Evaluating the limits of solar photovoltaics (PV) in traditional electric power systems. Energy policy May 31;35(5): [8] Mondal MA, Islam AS. Potential and viability of grid-connected solar PV system in Bangladesh. Renewable energy Jun 30;36(6): [9] Ulgen K. Optimum tilt angle for solar collectors. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects Sep 1;28(13): [10] Lave M, Kleissl J. Optimum fixed orientations and benefits of tracking for capturing solar radiation in the continental United States. Renewable Energy Mar 31;36(3): [11] Kacira M, Simsek M, Babur Y, Demirkol S. Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey. Renewable energy Jul 31;29(8): [12] Mousazadeh H, Keyhani A, Javadi A, Mobli H, Abrinia K, Sharifi A. A review of principle and sun-tracking methods for maximizing solar systems output. Renewable and sustainable energy reviews Oct 31;13(8): [13] Wang JM, Lu CL. Design and implementation of a sun tracker with a dual-axis single motor for an optical sensor-based photovoltaic system. Sensors Mar 6;13(3): [14] Tudorache T, Kreindler L. Design of a solar tracker system for PV power plants. Acta Polytechnica Hungarica Jan 1;7(1): [15] Chin CS, Babu A, McBride W. Design, modeling and testing of a standalone single axis active solar tracker using MATLAB/Simulink. Renewable Energy Nov 30;36(11): [16] Yao Y, Hu Y, Gao S, Yang G, Du J. A multipurpose dual-axis solar tracker with two tracking strategies. Renewable Energy Dec 31;72: [17] Chang TP. Output energy of a photovoltaic module mounted on a single-axis tracking system. Applied energy Oct 31;86(10): [18] Chang TP. The gain of single-axis tracked panel according to extraterrestrial radiation. Applied Energy Aug 31;86(7): [19] Al-Mohamad A. Efficiency improvements of photo-voltaic panels using a Sun-tracking system. Applied Energy Nov 30;79(3): [20] Dolara A, Grimaccia F, Leva S, Mussetta M, Faranda R, Gualdoni M. Performance analysis of a single-axis tracking PV system. IEEE Journal of Photovoltaics Oct;2(4): [21] Eke R, Senturk A. Performance comparison of a double-axis sun tracking versus fixed PV system. Solar Energy Sep 30;86(9): [22] Shah IA, Khalid W, Ahmed T, Mehfooz Q, Irshad N. Energy yield and economic analysis of tracker controlled and fixed angle photovoltaic solar power system. Universal Journal of Electrical and Electronic Engineering 5(3): 56-66, Reference Number: JO-P

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