म न टल इनऔरप ल टल इनस रफ ट व टकप नल क म ड ल ग, सम ल शनऔर दश न व षण

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1 MODELING, SIMULATION AND PERFORMANCE ANALYSIS OF MONOCRYSTALLINE AND POLYCRYSTALLINE SOLAR PHOTOVOLTAIC PANELS म न टल इनऔरप ल टल इनस रफ ट व टकप नल क म ड ल ग, सम ल शनऔर दश न व षण BY NEELAM RATHORE THESIS MASTER OF TECHNOLOGY IN AGRICULTURAL ENGINEERING (RENEWABLE ENERGY ENGINEERING) 2015 DEPARTMENT OF RENEWABLE ENERGY ENGINEERING COLLEGE OF TECHNOLOGY AND ENGINEERING MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY UDAIPUR

2 MODELING, SIMULATION AND PERFORMANCE ANALYSIS OF MONOCRYSTALLINE AND POLYCRYSTALLINE SOLAR PHOTOVOLTAIC PANELS म न टल इनऔरप ल टल इनस रफ ट व टकप नल क म ड ल ग, सम ल शनऔर दश न व षण A THESIS SUBMITTED TO THE MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY UDAIPUR IN PARTIAL FULFILMENT THE REQUIREMENT FOR THE DEGREE OF MASTER OF TECHNOLOGY IN AGRICULTURAL ENGINEERING (RENEWABLE ENERGY ENGINEERING) BY NEELAM RATHORE 2015

3 MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR Dated: CERTIFICATE-I This is to certify that Mrs. NeelamRathore has successfully completed the comprehensive examination held on 21 January 2015 as required under the regulations for Post- Graduate Studies in Master of Technology in Agricultural Engineering (Renewable Energy Engineering). Dr. Deepak Sharma Head Department of Renewable Energy Engineering, College of Technology and Engineering, Udaipur

4 MAHARANA PRATAP UNIVERSITY OF AGRICULTURE AND TECHNOLOGY COLLEGE OF TECHNOLOGY AND ENGINEERING, UDAIPUR Dated: June 30, 2015 CERTIFICATE-II This is to certify that this thesis entitled Modeling, Simulation and Performance Analysis of Monocrystalline and Polycrystalline Solar Photovoltaic Panels submitted for the degree of Master of Technology in Agricultural Engineering in the subject of Renewable Energy Engineering embodies bonafide research work carried out by Mrs. NeelamRathore under my guidance and supervision and that no part of this thesis has been submitted for any other degree. The assistance and help received during the course of investigation have been fully acknowledged. The draft of the thesis was also approved by the advisory committee on 29 June, Dr. Surendra Kothari Major Advisor Dr. Deepak Sharma Head of Department Renewable Energy Engineering Dr. B.P. Nandwana DEAN College of Technology and Engineering, Udaipur

5 ABSTRACT Solar photovoltaic systems can convert the solar energy directly into electrical energy. The amount of energy produced depends on the solar radiation captured by the PV panel.the user wants to operate the Photovoltaic (PV) array at its highest energy conversion output by continuously utilizing the maximum available solar power of the array. A mathematical model of aphotovoltaic (PV) cell used MATLAB-SIMULINK environment, is developed and presented. Modeling and simulation was done for monocrystalline panel and polycrystalline panel of 40 Watt. For both types of panels electrical characteristics were plotted and temperature effect was analyzed. During modeling and simulation the PV cell temperature is maintained constant at 25 C and the solar intensity is varied in steps up to the rated value of 1000 W/m 2.. Further MATLAB code was written to analyze effect of variation in temperature. Power was observed at 25 C, 50 C and 75 C using MATLAB coding.this model can be considered as a tool which can be used to study all types of PV modules available in markets, especially, their behavior under different weather data of standard test conditions (STC).Performance analysis of mono-crystalline and poly-crystalline solar photovoltaic panels was done considering certain parameters. The parameter which were taken are analysis of V-I curve, Effect of variation in tilt angle on PV module power, Effect of shading on PV Module power, Effect of increase of temperature on PV module power, Efficiency, Space efficiency and cost. Both the panels were compared on the basis of above parameters. Theoretically and Practically Effect of increase of temperature on PV module power was observed and it was concluded as temperature increases power decreases but the decrement of power is slightly lower for polycrystalline panel as compared to Monocrystalline panel. Efficiency of monocrystalline panel varies between 3% to 14% whereas Efficiency of polycrystalline panel varies from 2.5% to 9.5%.Effect of shading on PV Module powerwas done and it was observed that monocrystalline panel is less affected by shading and works better in shady condition as compared to polycrystalline panel.

6 CHAPTER 1 INTRODUCTION India is densely populated and has high solar isolation,whichis an ideal combination for using solar energy for different activities including powergeneration. Photovoltaic (PV) modules based power generation systems, represents the most suitable and prominent solution, to reduce CO 2 emissions.photovoltaic (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors by photovoltaic effect. Photovoltaic power generation employs solar panels which composed of a number of cells in the form of arrays and modules. Among the renewable energy sources,solar Photovoltaic power generation has been seen as a clean sustainable energy. Energy from PV modules offers several advantages, like requirement of little maintenance and no environmental pollution. PV arrays areused in many applications like, battery chargers, water pumping systems, grid connected PV systems, solar hybrid vehicles and satellite power systems etc. 1.1 Renewable Energy Status in India Looking to advantages at the Photovoltaic System, Government of India has taken several steps to boost upthe expansion of solar power capacityi.e. Jawaharlal Nehru National Solar Mission under the National Action Plan on Climate Change with plans to generate up to 1,00,000 MW grid-based solar powerup to The country added almost 950 MW of solar power capacity between April 2013 and March The year is expected to be an important year for the solar industry as the new government has come up with a number of solutions to boost the solar sector. Solar capacity in India is expected to grow at a rapid pace in the coming years with India expected to reach the 4GW mark by the end of the current year. As the PV panels play an important role in conversion of solar energy to electrical energy, it is necessary to have its complete information. The increase in a number of Photovoltaic system installed all over the world brought the need for proper supervision and control algorithms as well as modeling and simulation tool for predicting overall efficiency of system. The modeling and simulation of photovoltaic (PV) have made a great transition and form an important part of power generation in this present era. The cost and the performance of PV plants strongly depend

7 on the modules. Theperformance and electrical parameters of the modulesi.e. open circuit voltage and short circuit current, can be different than those provided by the manufacturer. Therefore, the behavior of the mathematical model of a PV module can t match with the real operating conditions. The output characteristic of PV module depends on the solar insolation, the cell temperature and the output voltage of PV module. 1.2Photovoltaic Cell PV cell are basically semiconductor diode. This semiconductor diode has got a p-n junction which is exposed to light. When the diode is illuminated by sunlight it generates electric power. Generally thepv cells are made up of various semiconductor materials, but mono-crystalline silicon and poly-crystalline silicon are mainly used for commercial use. Fig1.1: Photovoltaic Effect Working of PV cell is based on the basic principle of photovoltaic effect. The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light. As shown in Fig 1.1, when sunlight strikes the surface of photovoltaic cell, some portion of the solar energy is absorbed in the semiconductor material. If absorbed energy is greater than the band gap energy of the semiconductor, the electron from valence band jumps to the conduction band. Due to this, pairs of hole-electrons are created in the illuminated region of the semiconductor. The electrons thus created in the conduction band are now free to move. These free electrons are forced to move in a particular direction by the action of electric field present in the PV cells. These

8 flowing electrons constitutes current and can be drawn for external use by connecting a metal plate on top and bottom of PV cell. This current and the voltage produces required power. 1.3Photovoltaic Module As the power produced by a single PV cell is not enough for general use, so by connecting many single PV cell in series (for high voltage requirement) and in parallel(for high current requirement) the desired power can be achieved.therefore, PV module is a packaged, connected assembly of solar cells. Generally commercial modules consist of 36 or 72 cells. The modules consist of transparent front side, encapsulated PV cell and back side. The front side material is usually made up of low-iron and tempered glass. The efficiency of a PV module is less than a PV cell as some radiations are reflected by the glass cover and frame shadowing etc. To increase total voltage of the module, cells have to be connected in series as shown in Fig. 1.2(V out =V1+V2+V3+ ). Connecting PV cells in parallel, as shown in Fig.1.3, increases the total current generated by the module (I out =I1+I2+I3+...). The total current is equal to sum of current produced by each cell. Fig 1.2: PV cells in series

9 Fig 1.3: PV cells in parallel 1.4Characteristics of a PV Cell In a PV characteristic there are basically three important points viz. open circuit voltage (V OC ), short circuit current ( I SC ) and maximum power point (P MAX ). The power output increases as the module voltage increases, it reaches the peak and it drops as the voltage approaches to open circuit voltage. The output power of the solar cell peaks up at certain voltage and current. The maximum power that can be extracted from a PV cell are at the maximum power points.this peak power is mentioned by the manufacturer. Normally the module output is less than peak output power. As shown in curve below MPP refers to maximumpowerpoint at I MP (maximumcurrent) and V MP (maximum voltage).

10 Fig 1.4:Characteristics of PV Cell Short circuit current (I sc ): The maximum current that flows in a solar cell when its terminals at P side and N side are shorted with each other i.e. V =0. It is also called as light generated current and photocurrent Open circuit voltage (V OC ): It is maximum voltage generated across the terminals of a solar cell when they are kept open i.e. I=0. It depends on short circuit current and reverse saturation current Fill factor (F.F): It is ratio of maximum power P M = I M * V M that can be extracted from solar cell to an ideal power P o = V OC * I sc.the F.F represents the squareness of the solar cell I-V curve and is represented in terms of percentage. F.F =P M / (I SC V OC ) Efficiency (ƞ): Efficiency of solar cell is the ratio between the maximum power and the incident light power. P in is taken as the product of the solar irradiation of the incident light (G=1000 W/m 2 ), measured in W/m 2, with the surface area (Ac) of the solar cell in m 2.The efficiency of the solar cells fall when temperature increases, mainly, due to the decrease of the open circuit voltage. Ƞ = P M / P in Pin = G. Ac Solar radiation and temperature plays an important role in output power produced by panels. 1.5 Effect of Solar Radiation The power output of the solar PV module strongly depends on solar radiation falling on it. The power of a module decreases almost linearly with the decrease in intensity of solar radiation. The current produced by a PV module is linear function of the radiation intensity.thus if the radiation is half the peak radiation intensity(1000 W/m 2 ), the module will produce half the peak current. But the voltage of the module is a logarithmic function of the radiation intensity. Therefore, the drop in module voltage is not significant for a large change in radiation intensity.

11 Fig 1.5: Effect of Solar Radiation 1.6 Effect of Temperature The output power of solar PV module depends on temperature at which module is operating. The module temperature is normally higher than the ambient temperature. The module temperature could be up to 20 C to 30 C higher than the ambient temperature. The increased cell temperature results in an increase in the short circuit current and decrease in the open circuit voltage. Decrease in the Open circuit voltage is more prominent than the increase in the short circuit current. Therefore, the power output and the efficiency of solar cell and modules decreases with the increase in its operating temperature. The current increase with temperature is due to the decrease in the band gap of Si and voltage decreases with temperature due to the increase in the carrier recombination. The effect of increasing temperature on the PV characteristics is shown in graph: I SC Cell Temperature

12 Fig 1.6:Effect of temperature 1.7 Justification Basically modeling and simulation of solar cell allows designers and engineers to avoid repeated building of multiple physical prototypes to analyze designs for new or existing parts. Before creating the physical prototype, users can virtually investigate many digital prototypes. Photovoltaic systems are important as they can generateelectricity on-site where it is needed, avoiding transport losses and reducing to CO 2 emission reductions in urban areas.knowledge of the characteristic of a PV panel is a prerequisite for designing and dimensioning a PV power plant. As PV module has non-linear characteristics,it is necessary to model it for the design and simultaneously to simulate the PV system for differentapplications. This motivates to develop a generalized model for PV cell, module and array usingmatlab/ Simulink. This project includes comparison of monocrystalline and polycrystalline panel on the basis of various parameters like efficiency, cost, shading effect, and temperature effect and space efficiency. As efficiency is important during establishment of PV power plant, so MATLAB coding is made which be useful for plotting electrical characteristics. From these characteristics power can be calculated at various radiations. Temperature effect is also shown in MATLAB coding for both panels. The modeling of PV module generally involves the approximation of thenon-linear I-V curve. In order to size a PV system for efficient working and to meet the desired load requirements under the local meteorological conditions, the characteristic performance of each component in the PV system is required.the solar efficiency indicates how much electricity a single panel can produced based on surface area. Further it is necessary to have complete information of panels which is an important part of Photovoltaic System for generation of electricity as solar photovoltaic system is an efficient solution to usage of diesel generators. PV system can reduce operating cost of generating electricity and provide an uninterrupted power supply throughout life. On an average, per unit cost with diesel generator varies fromrs18-22, while the cost with solar system does not exceed Rs 8 per unit and it remains constant throughout the life of power plant. The developed model is

13 valid for measuring I-V characteristics and can work with few parameters of input demonstrate to graph and numerically the operation of a solar model. The objective is develops in the future a complete model to simulate the electrical behaviour of the PV systems. Objectives: 1. Modeling of Mono-Crystalline and Poly-Crystalline Solar Photovoltaic Panel. 2. Simulation of Selected Solar Photovoltaic Panels. 3. Performance Analysis of Mono-Crystalline and Poly-Crystalline Solar Photovoltaic Panels.

14 CHAPTER 2 REVIEWS OF LITERATURE This section deals with the review of the research work carried out in relation to the objectives of the proposed work. Modeling and simulation has been studied by many researchers in all over the world. Some important and relevant research papers were reviewed which are as follows: 2.1 Simulation Model of Photovoltaic Panel Sukamongkolet al. (2001) described the development of a simulation model for predicting the performance of a solar photovoltaic (PV) system under specified load requirements and prevailing meteorological conditions at the site location. Simulated results from the model under the same operating and environmental conditions were compared with those observed from the experimental tests. Tsai et al.(2008) presented the implementation of a generalized photovoltaic model using MATLAB/Simulink software alongwith verification using a PV cell and a commercial module. Taking the effect of sunlight irradiance and cell temperature into consideration, the output current and power characteristics of PV model were simulated and optimized using the proposed model. It was observed that with increase of working temperature, the short-circuit current of the PV module increases, whereas the maximum power output decreases. Villalvaet al. (2009) has analyzed the development of a method for the mathematical modeling of photovoltaic arrays.itdescribed the method which was used to obtain the parameters of the array model using information from the datasheet. The photovoltaic array model could be simulated with any circuit simulator. The equations of the model were presented in details and the model was validated with experimental data. This text presented in details the equations that form the I-V model and the method used to obtain the parameters of the equation. Hernanzet al. (2010)presented a photovoltaic model using MATLAB. They proposed main characteristics and parameters that have to consider while modeling a photovoltaic module. Different models were compared to analyze the performance of solar cells. IV and PV characteristics were plotted and the model was validated with experimental data of commercial

15 PV module, Mitsubishi PV-TD1185MF5. When curves were plotted it was observed that the higher the irradiation, the greater the current while voltage is going to maintain almost constant although the irradiation increases or diminishes. Further the efficiency of the solar cells falls when temperature increases. Pandiarajan and Ranganath (2011) presented a unique step-by-step procedure for the simulation of photovoltaic modules with MATLAB/ Simulink. It also presented the PV module equivalent circuit and equations for Ipv, the output current from the PV module. One-diode equivalent circuit is employed in order to investigate I-V and P-V characteristics of a typical 36 W solar module. I-V and P-V characteristics under varying irradiation with constant temperature were obtained. It was found that with increase of operating temperature the current output increases and the voltage output decreases while when the irradiation increases, the current output increases and the voltage output also increases. Basim (2012) proposed a MATLAB Simulik based simulation study of PV cell/pv module/pv array.it presented brief introduction to the behavior and functioning of a PV device and the basic equation of the two-diode model. The simulation model makes use of the two-diode model basic circuit equations of PV solar cell, taking the effect of sunlight irradiance and cell temperature into consideration on the output current I-V characteristic and output power P-V characteristic. A particular typical 50W solar panel was used for model evaluation. It concludedthe influence of irradiation on maximum power point, the higher the irradiance the major the maximum power point will be. The model curves exactly match with the experimental data at the three remarkable points provided by the data sheet therefore simulation results show excellent correspondence to manufacturers published curves in data sheet. Chouderet al. (2012) presented a detailed characterization of the performance and dynamic behaviour of photovoltaic systems by using Lab-VIEW real-time interface system. Comparison of simulation results with monitored data in real-time was done. The model obtained the I-V characteristic of a PV module using LABVIEW environment. The input parameters for the calculations were: Open circuit voltage of the solar cell (Voc), short circuit current of the solar cell (Isc), series resistance (Rs), shunt resistance (Rsh), number of cell in series ( Ns), number of

16 cell in parallel (Np), solar irradiation ( G), temperature( T), and the solar cell ideality factor (n). The validation of the procedure is carried out by comparing real measurement of I V characteristics measured at outdoor conditions and the simulated one generated by introducing the expected five model parameters. The results show that there is a good agreement between the measured and simulation results values. Salmiet al. (2012) presented MATLAB/SIMULINK model of a photovoltaic cell. The developed model allows the prediction of PV cell behavior under different physical and environmental parameters. The model can also be used to extract the physical parameters for a given solar PV cell as a function of temperature and solar radiation. This paper carried out a MATLAB/SIMULINK model of monocrystalline PV cell that made possible the prediction of the PV cell behavior under different varying parameters such as solar radiation, ambient temperature, series resistor, shunt resistor. The module model was simulated and validated experimentally using the high efficient PVL-124 solar laminate panel. Dev andjaya Prabha(2013)defined a simplified electrical based mathematical modeling and its MATLAB simulation of photovoltaic cell. They estimated the physical and electrical behaviour of the PV cell with respect to changes on environmental parameter of temperature and irradiance. Four parameters were introduced in this model to account for the complex dependence of the PV module performance upon solar-irradiance intensity and PV module temperature i.e. the short circuit current, open-circuit voltage, fill factor and maximum power-output of the PV module. They concluded that Irradiance and temperature plays an important role in predicting the I-V characteristic i.e. the irradiance affects the output and temperature mainly affects the terminal voltage. Soumyadeep(2013) presented a modified step-by-step procedure for the simulation of photovoltaic modules with Matlab/Simulink. One-diode equivalent circuit was employed in order to investigate I-V and P-V characteristics of a typical 45 W solar module (PM045). MATLAB code for generating P-V and I-V curves was presented. All the possible graphs of I-V and P-V were drawn by varying the parameters like temperature, radiation and seriesresistance. Venkateswarlu and Raju (2013) developed the Simulation model for simulation of a single solar cell and two solar cells in series using sim electronics (MATLAB /Simulink) environment.

17 Asolar cell block is available in simelectronics, which was used with many other blocks to plot I- V and P-V characteristics under variations of parameters considering one parameter variation at a time. Effect of two environmental parameters of temperature and irradiance variations could also be observed from simulated characteristics. They achieved similar IV and PV characteristics curves to the graphs that were provided by the manufacturer of the different solar panels. Sudeepika and Khan(2014) analyzed the mathematical model of PV cell(46 W solar module) in MATLAB /Simulink.They verified the I-V and P-V characteristics for constant irradiation (1000w/m2) and constant temperature(25ºc).they also plotted P-V & I-V characteristics for different irradiation (1000W/m 2, 600W/m 2, 200W/m 2 ) and for different temperatures (25ºC, 50ºC and 75ºC). 2.2 Modeling and Simulation of PV panels Dunford et al. (2004) proposed a novel modeling process to configure a computer simulation model, which was able to demonstrate the cell s output features in terms of environmental changes in irradiance and temperature. Three types of solar module (CIS thin film, m-si and c- Si) were modeled and evaluated. The effectiveness of this approach was evaluated through comparison of simulation results to the data provided by product. The evaluations prove the effectiveness of this method based on a simplified one-diode model. Adamo et al. (2009)described the first results of a simulation and characterization tool useful to evaluate electrical performances of photovoltaic (PV) panels. An electrical model for a typical 10 Wp PV panel is estimated and tested of the measured I-V characteristic. A simple one-diode model was used in order to estimate the electrical parameters of a PV panel and predict how the I-V characteristic changes with environmental parameters such as temperature and irradiance. They also estimated the proposed tool the two unknown parameters (series and shunt resistances) with the help of proposed tool. Das.Det al. (2011)aimed to increase the efficiency and power output of the system. As it is required that constant voltage to be supplied to the load irrespective of the variation in solar irradiance and temperature so this problem was sort out in this paper using boost convertor. They designed system in such a way that with variation in load, the change in input voltage and power

18 fed into the converter follows the open circuit characteristics of the PV array. The open circuit P- V, P-I, I-V curves were obtained from the simulation of the PV array designed in MATLAB and dependence on the irradiation levels and temperatures. S.Sheik Mohammed (2011)presented modeling of photovoltaic (PV) module using MATLAB/Simulink. The model was developed on the basis of mathematical model of the PV module. Two particular PV modules were selected for the analysis of developed model. The essential input parameters such as maximum voltage (Vm), maximum current ( Im), open circuit voltage (Voc),short circuit current (Isc), number of cell in series (Ns), temperature (Tc) and irradiation ( G) were taken from the manufacturers datasheet for the typical 60W and 64W modules selected for analysis. I-V and P-V characteristics curves were obtained for the selected modules with the output power of 60W and 64W from simulation and compared with the curves provided by the datasheet. The results obtained from the simulation model were well matched with the datasheet information. Hadjabet al. (2012) presented the results of the characterization and modeling of the electrical current-voltage and power-voltage of the photovoltaic (PV) panel BP 3160W, using a new approach based on artificial intelligence. The electrical parameters of solar cells and electrical parameters of the optimal PV panel (current, voltage and power) analyzed according to changes in weather (temperature, irradiation) by the simulation programs carried out in MATLAB. It found that the current of a solar cell is proportional to the solar illumination, it increases slightly with temperature, and the open circuit voltage of a solar panel varies slightly with the solar illumination and decreases with increasing temperature. Abdulkadiret al. (2012) presented the modeling and simulation of photovoltaic model using MATLAB/Simulink software package. MXS 60 PV Module is taken as the reference module for simulation they take the effect of irradiance and temperature into consideration and the output current and power characteristic of PV model were simulated using the proposed model. The PV current Isc is a function of the solar irradiation and is the only energy conversion process in which light energy is converted to electrical energy. The proposed model was found to be better and accurate for any irradiance and temperature variations. This paper provided a clear and concise understanding of the, I-V and P-V characteristics of PV module. Hence, this circuit

19 model presents the relationship between module parameters and circuit performance. Kondawara and Vaidya (2012) analyzed two different methods to maximize the generated power which included comparison between the perturb and observe control method and the incremental conductance control method.the comparison was done with help of boost convertor. In order to compare the accuracy and efficiency of two MPPT algorithms selected MATLAB/Simulink is used to implement the task of modeling and simulation. They included solar panel that has standard value of insolation and temperature in the simulation circuit. Finally they concluded that the best controller for MPPT is Perturb & Observe controller. Bikaneriaet al. (2013) examined the behavior of ideal solar cell model and the behaviors of the solar cell with series resistance model were studied in this paper. They used the BP SX 150S PV module. Simulation studies were carried out with different temperatures & irradiations.they studied effects like: temperature dependence, solar radiation change, and diode ideality factor and series resistance influence. For simulation result the mathematical models for the ideal solar cell and the solar cell with series resistance were implemented in MATLAB/Simulink. Various P-V and I-V characteristics showing effects of temperature, irradiance and ideality factor were plotted. Edouard and Njomo (2013) proposed a simple method of modeling and simulation of photovoltaic panels using MATLAB software package. The method is used to determine the characteristic of PV panel and to study the influence of different values of solar radiation at different temperatures concerning performance of PV cells. Taking the effect of irradiance and temperature into consideration, the output current and power characteristic of photovoltaic module were simulated using the proposed model. Detailed modeling procedure for the circuit model was presented. It was concluded that the I-V, P-Vand P-I characteristics of a solar cell/module are highly dependent on the solar irradiance values. At constant module temperature, with increase of solar irradiance, the increase in short-circuit current and inmaximum power output of the PV module is much larger than the increase in the open circuit voltage Modeling to Study the Effects of Partial Shading H. Patel and VivekAgarwal (2008) studied the effect of partial shading on PV module. It presenteda MATLAB-based modeling and simulation scheme suitable for studying the I V and

20 P V characteristics of a PV array under a non-uniform insolation due to partial shading. It was observed that, for a given number of PV modules, the array configuration (how many modules in series and how many in parallel) significantly affects the maximum available power under partially shaded conditions.it was demonstrated that, if the likely shading pattern on the PV array is known, the simulation model is handy to design the most optimum configuration of the PV array to extract the maximum power.

21 CHAPTER 3 MATERIALS AND METHODS 3.0 General The presentstudy on modeling, simulation and comparative analyses of PV panels was carried out at the Department of Renewable Energy Engineering, CTAE, Udaipur. The study area falls at latitude of N, longitude of and at an altitude of m above mean sea level. This project focuses on modeling and simulation of monocrystalline and polycrystalline panels each of 40 W. The developed model allows the prediction of PV cell behaviour under different physical and environmental parameters. Since the field tests are very expensive and depend primarily on weather conditions, MATLAB coding is presented so that V-I curve could be achieved at any time. A MATLAB-based modeling and simulation scheme desirable for studying the I-V and P V characteristics of a photovoltaic panel is presented. Taking the effect of irradiance and temperature into consideration, the current - voltage (I-V) and power - voltage (P- V) characteristics of PV model are simulated using the proposed model. Further MATLAB code is written to analyze effect of variation in temperature. Modeling here means coding in MATLAB with the certain parameters.the essential parameters required for modeling the system are taken from datasheet provided by manufacturer. I-V and P-V characteristics curves are obtained for the selected modules with the output power of 40W from simulation. Both the selected panel has 36 cells in series and 1 cell in parallel. In another section Monocrystalline and polycrystalline panels were compared on the basis of various parameters like effect of increase in temperature on power, efficiency, effect of shading on power, effect of tilt on power, space efficiency and cost. Various parameters were analyzed using Solar PV Training and Research Kit available in department. The modeling procedure, equipment, instrument used and experimental procedure have been discussed in this chapter through the following objectives. Modelingof Mono-Crystalline and Poly-Crystalline Solar Photovoltaic Panels. Simulation of selected Solar Photovoltaic Panels. Performance Analysis of Mono-crystalline and Poly-crystalline Solar Photovoltaic Panels.

22 3.1Modeling of Mono-crystalline and Poly-crystalline Solar Photovoltaic Panels: The modeling and simulation of polycrystalline and monocrystalline panels based on mathematical equations was made using MATLAB/Simulink software.modeling of PV cell involves the estimation of the V-I and P-V characteristics curves to emulate the real cell under various environmental conditions. For getting voltage current (V-I) characteristics, MATLAB was selected. Since the field tests are very expensive and depend primarily on weather conditions, MATLAB coding was presented so that V-I curve could be achieved at any time (APPENDIX A.1 TO A.4). Further MATLAB code was written to analyze effect of variation in temperature. Power was observed at 25 C, 50 C and 75 C using MATLAB coding. For both types of panels electrical characteristics were plotted and temperature effect was analyzed.a MATLAB-based modeling and simulation scheme isdesirable for studying the V-I and P V characteristics of a photovoltaic panel was presented. Modeling here means coding in MATLAB with the certain parameters.the essential parameters required for modeling the system were taken from datasheet provided by manufacturer. V-I and P-V characteristics curves will be obtained for the selected modules with the output power of 40W fromsimulation. Both the selected panel had 36 cells in series and 1 cell in parallel. The modeling of selected PV panels was made using certain equationsthat are described in this section. Main parameters that were calculated while modeling are Reverse saturation current, Photocurrent and Output of PV panel. The building block of PV arrays is the solar cell, which is basically a p-n junction that directly converts light energy into electricity. Its equivalent circuit as shown in Fig 3.1 Fig3. 1: Solar cell model using single diode with R S and R P

23 The current source I SC represents the cell photo current, R s and R p are used to represent the intrinsic series and shunt resistance of the cell respectively. Usually the value of R p is very large and that of R s is very small, hence they may be neglected to simplify the analysis. PV cells are grouped in larger units called PV modules which are further interconnected in series-parallel configuration to form PV arrays. The ideal photovoltaic module consists of a single diode connected in parallel with a light generated current source ( I SC ) as shown in Figure 3.2. The PV mathematical model used to simplify our PV array is represented by the equation. Neglecting the series resistance and parallel resistance the solar cell model becomes: Fig 3.2:Solar cell model using single diode with R S I = I SC -I RS Where I sc is photocurrent which is the light-generated current at the nominal condition (25 C and1000w/m 2 ), atconstant temperature the photon generated current I sc is directly proportional to solar insolation. I rs is reverse saturation current or the diode current I D which is that part of the reverse current in a diode caused by drift of minority carriers. The equations of reverse saturation current and photocurrent are given by: I rs =I scref [e ( qvoc NsKAT ) 1] s I sc =[ I scref + K (T T ref )] 1000 The equation that describes the I-V characteristic of the circuit in Fig 3.2 is given by

24 I SC I D V D / R P - I PV = 0 Thus I pv = I sc I D V D / R P And the I rs =I scref [e ( qvoc NsKAT ) 1] is reverse saturation current or diode current I D. I 0 = I rs -[( T Tref )3 e [ ( qeg 1 )*( KA Tref 1 T dependent and it increases with increase in temperature. )]] is module saturation current which is highly temperature Output of PV Module: It represents the output current generated which depends on the PV module voltage, solar irradiance on PV module, wind speed, and ambient temperature. I PV = N P I SC - N S I O {exp (q(v PV +I PV R S )/ N S AKT)- 1} - V PV + (I PV R S / R P ) Where k is the Boltzmann constant (1.38 x 10 ^ -23 J K -1 ), q is the electronic charge (1.602 x 10 ^ -19 C), T is the cell temperature (K), A is the diode ideality factor, the series resistance R S (Ω) and is the shunt resistance R P (Ω).N S is the number of cells connected in series = 36. Np is the number of cells connected in parallel and V OC = V PV. These reference values are generally provided by manufacturers of PV modules for specified operating condition such as STC (Standard Test Conditions) for which the irradiance is 1000 W/m 2 and the cell temperature is 25 C. As the value of the parallel resistance R P is generally high and the series resistance R s is low, hence neglected to simplify the model. Neglecting R P by: I pv = N p I sc N s I 0 {e ( qvoc NsKAT ) 1} and R s the output of PV module is given This propose model includes a current source I sc depends on solar radiation and cell temperature; a diode in which the inverse saturation current I O depends mainly on the operating temperature.as shown in coding(appendix A.1 to A.4) T refers to operating temperature of panel in kelvin and Tr refers to reference temperature which is 298K (25 C). Tr was changed to 323 K (50 C), 348 K (75 C) and power was observed at different temperature for both panels. Power output was compared for both panels.

25 Nominal Test Conditions This task was carried out to compare the performance between different PV cells. The parameters are generally given in a datasheet. The datasheets provide remarkable parameters regarding the performance and characteristics of PV arrays with respect to these standard test conditions. The nominal (standard) test conditions are as follows: R = 1000 W/m 2 T = 25 C Simulation of Selected Solar Photovoltaic Panels. A Mathematical simulation was proposed and evaluated. Here simulation refers to the result of modeling using MATLAB. Simulation results give electrical characteristics at different radiation. Basically Modeling and Simulation allows designers and engineers to avoid repeated building of multiple physical prototypes to analyze designs for new or existing parts. Before creating the physical prototype, users can virtually investigate many digital prototypes.the simulation of PV module generally involves the approximation of the non-linear I-V curve. In order to size a PV system for efficient working and to meet the desired load requirements under the local meteorological conditions, the characteristic performance of each component in the PV system is required.the simulation tool gives also the advantage of simulating different PV array sizes and the possibility to arrange virtually the panels or arrays as a network to analyze the behaviour and performances of a plant in a lot of possible configurations. The solar efficiency indicates how much electricity a single panel produces based on surface area PV Panel characteristics Photovoltaic cell is characterized by four parameters. The panel selected from VIKRAM (ELDORA) solar which had specific V-I Characteristics values mentioned below: Short circuit current (I SC ) This is the maximum current that flows in a solar cell when its terminal at P side and N side are shorted with each other, i.e., V= 0. As provided by manufacturer: Short circuit current I sc = 2.45A (polycrystalline panel)

26 Short circuit current I sc = 2.40 A(monocrystalline panel) Open circuit voltage (V oc ) It is maximum voltage generated across the terminals across the terminals of solar cell when they are kept open, i.e., I=0. Open circuit voltage depends on the photocurrent and reverse saturation current. As provided by manufacturer: v oc = V (polycrystalline panel) v oc = V (monocrystalline panel) Fill Factor(FF) Fill Factor is essentially a measure of quality of the solar cell. It is calculated by comparing the maximum power to the theoretical power that would be output at both the open circuit voltage and short circuit current together. This is key parameter in evaluating the performance of solar cell. Higher the fill factor, solar panel has les parasitic losses, i.e., losses due to series resistance and parallel resistance within the cell itself. For better efficiency fill factor should be greater than 50% FF =P MAX / (I SC V OC ) =V M * I M / (I SC V OC ) FF p = 74.5% FF m = 76% Theoretical calculation: - According to the parameters provided by manufacturer, fill factor of both panels are calculated below 1. for polycrystalline panel = 17.40*2.30/21.90*2.45 =0.745 = 74.5% 2. for monocrystalline panel = 17.60*2.27/21.90*2.4 = = 76% Efficiency (η)

27 Efficiency of solar cell is the ratio between the maximum power and the incident light power. P in is taken as the product of the solar irradiation of the incident light, measured in W/m 2, with the surface area (Ac) of the solar cell in m 2.The efficiency of the solar cells fall when temperature increases, mainly, due to the decrease of the open circuit voltage.the percentage of the energy that is converted into electrical energy is the panel's efficiency. If a 0.2 square-meter panel have a power output rating of 40 watts. Assuming 1,000 available watts, this panel converts 14 percent of that solar energy into electrical energy. Therefore, this panel has an efficiency of 14 percent. According to international standard for characterization of solar cell efficiency is calculated at radiation of 1000 W/m 2. η= P max / P in =I M* V M / P in Pin = G. Ac η p = 20% η m = 22% Practical efficiency is always 20% - 40% less than theoretical efficiency. An efficiency of 20% means panel will convert 20% of solar light into electricity. 3.3.Performanceanalysis of monocrystalline and polycrystalline solar photovoltaic panels Monocrystalline and polycrystalline panels were compared on the basis of various parameters like effect of increase in temperature on power, efficiency, effect of shading on power, effect of tilt on power, space efficiency and cost. Experimental setup and procedure: Solar PV Training and Research Kit available in department was used. This kit mainly consists of 2 PV panels which are detachable, so monocrystalline and poly-crystalline panel both was employed one by one and readings were taken. The main parts of the kit are Control unit, Logger Plotter, Dc-Dc Converter and Inverter. It has control unit which displays open circuit voltage and short circuit current. Any change on the panel i.e. Change in radiation, when panel get shaded, when panel get tilted, change in

28 temperature, is shown by change in voltage and current on control unit. Kit has magnetic tape which shows tilt angle in degrees so panel can be tilted and power can be observed at various tilt angles. Brief description of PV training kit: The block diagram of the kit is shown: Control Logger PV1 PV2 Computer Unit Plotter DC-DC Converter & Inverter Fig. 3.3 Block diagram of PV research & training kit The description and name of the different components of kit are given below: 1. Control unit 1 AC ammeter 4 DC ammeter and 4 DC meter voltmeter 1 AC voltmeter 1 fixed AC load of 5 W 1 fixed DC load of 8W (8 LED of 1W each) Two batteries of 4.5 Ah,12V 2 Diodes 1 potentiometer of 200 ohm 1Temperature meter with RTD 2. DC DC converter & Inverter Buck type DC-DC converter Fig 3.4 Control unit

29 50W Inverter 3. Source unit PV 1 and PV 2 are panels One module stand 4. Logger Plotter Used to make computer interface of Photo voltaic system with computer to draw automatic I-V characteristics. Fig 3.5Source Unit Fig3.6DC-DC Converter Inverter and logger plotter Types of panel used 1.Monocrystalline Panel The typical monocrystalline solar cell is a dark black color, and the corners of cells are usually missing as a result of the production process. Monocrystalline solar cells are made out of silicon ingots, which are cylindrical in shape.

30 Fig.3.7 Monocrystalline panel 2. Polycrystalline Panel PolycrystallinePanel is identifiable by its signature light or dark blue color. It is made up ofraw silicon which is melted and poured into a square mold, which is cooled and cut into perfectlysquare wafers. Fig.3.8 Polycrystalline panel Instrument used to measure radiation: Solar Power Meter

31 Fig. 3.9: Solar power meter 3.3.1Analysis of V- I Characteristics: PV module is characterized by its V-I and P-V characteristics. In I-V characteristics maximum current at zero voltage is the short circuit current ( I sc ) which can be measured by shorting the PV module and maximum voltage at zero current is the open circuit voltage (V oc ). In PV curve the maximum power is achieved at only one point which is called MPP and the voltage and current corresponding to this point are referred as V MP and I MP. On increasing the temperature,v oc of the module decreases while I SC remains the same which in turn reduces the power. On changing the solar insolation I SC of the module increases while the V oc increases very slightly. The circuit diagram to evaluate I-V and P-V characteristics of module is shown. The fig shows PV system which includes PV module and variable resistor (Pot Meter) with ammeter and voltmeter for measurement. Pot meter in this circuit works as a variable load for the module.when load on the module is varied by pot meter the current and voltage of the module gets changed which shift the operating point on I-V and P-V characteristics. The solar radiation was measured by solarimeter. Radiation on module was calculated by taking average of the radiation

32 recorded at three different positions on module (upper end, middle and lower end). Readings were taken at different radiation and at constant temperature of 25 C.The V-Iand P-V characteristics can be achieved by following connections in control board. As shown in figure 3.10, A was ammeter which gave current readings and V was voltmeter which gave voltage readings. The power was calculated by multiplication of voltage and current.solar panel refers to type of panel that was used i.e., monocrystalline panel or polycrystalline panel. At one time one panel was connected and readings were taken. Any change on the panel i.e. change in radiation, change in temperature, shading and tilt can be seen by change in voltage and current.maximum power was calculated for both the panels. Fig 3.10: Circuit diagram to analyze V-I characteristics Fig 3.11: Experimental setup for observation from polycrystalline panel

33 Fig3.12:Experimental setup for observation from monocrystalline panel 3.3.2Effect of variation in tilt angle on PV module power: Tilt is the angle between the plane surface under consideration and the horizontal plane. PV array works best when the sun s rays shine perpendicular to the cells. When the cells are directly facing the sun in both azimuth and altitude, the angle of incidence is normal. Therefore, tilt angle should be such that it faces the sun rays normally for maximum number of hours. For best performance throughout the year, tilt should be equal to the latitude angle. The positioning of solar panels determines the power output. The angle of the sun in relationship to the angle of the solar panel determines the maximum power density. The tilt angle has the biggest effect on the efficiency of the solar panel. When the angle of the sun is perpendicular to the solar panel, it provides the maximum energy output. In the kit the tilt angle of the module can be changed by rotating the lever below the module. Following connections were done to analyze the effect of tilt on power. The pot meter was kept at fixed position and power is measured at different tilt angles. For different tilt positions radiation was calculated and power was measured.

34 Fig 3.13:Circuit diagram to analyze effect of variation of tilt angle Magnetic Tape showing Tilt angle Fig. 3.14Experimental setup for tilt angle (polycrystalline panel) of 30 o

35 Fig 3.15:Experimental setup for tilt angle (monocrystalline panel) of 10 o Effect of shading on PV module power: If solar panels are shaded directly or receive a reduced amount of sunlight, their current decreases. Therefore, they will produce a lower amount of power. If a shaded cell is connected in series with other cells, the overall current of the series connection is limited to that of the shaded cell. In extreme cases, this power imbalance can damage a solar panel. For this reason, panels are typically equipped with components called bypass diodes, which redirect the flow of current around shaded or impaired cells. Shading obstructions can be from soft or hard sources. If a tree branch, roof vent, chimney or other item is shading from a distance, the shadow is diffuse or dispersed. These soft sources significantly reduce the amount of light reaching a solar panel s cells. Hard sources are defined as those that stop light from reaching solar cells, such as a blanket, tree branch, bird dropping sitting directly on top of the glass. If even one full cell is hard shaded, the voltage of that modulewill drop to half of its un-shaded value in order to protect itself. If enough cells are hard shaded,the module will not convert any energy.

36 Fig 3.16: Examples of partial cell shading Partial shading of even one cell of a 36-cell solar panel will reduce its power output. As all cells are connected in a series string, the weakest cell will bring the others down to its reduced power level. Therefore, whether 1/2 of one cell is shaded or 1/2 a row of cells is shaded, (as shown above), the power decrease will be the same and proportional to the percentage of area shaded, in this case 50%. When a full cell is shaded, it can consume energy produced by the remainder of the cells, and trigger the solar panel to protect itself. The solar panel will route the power around that series string. If even one full cell in a series string is shaded, as seen in diagram, it will likely cause the module to reduce its power level to 1/2 of its full available value. If a row of cells at the bottom of a solar panel is fully shaded, as seen in Figure, power output may drop to zero. Fig 3.17: Examples of full cell shading In the considered panels there are 36 solar cells in a module. These 36 solar cells are in series without bypass diode so shading of one cell will be sufficient to reduce the power to zero. The arrangement gives zero power if the entire row gets shaded. Diode is very important element in

37 the PV system. This element can work as blocking diode or as a bypass diode. Diodes connected in series with cells or modules are called blocking diodes and diodes connected across cells or modules are called bypass diodes.a shaded solar cell is not able to pass as much current or voltage as an un-shaded cell, causing its maximum power point to drop as a result. The more the cell is shaded, the more the power drops. It is far worse to have one cell shaded by 75% than it is to have three cells shaded by 25%. As un-shaded cells try to pass more current than the shaded cell is capable of handling, it actually develops a negative voltage and draws power. As the power output of a module drops, it pulls the rest of the panels in the string down as well. The inverter will begin to reduce power output, and eventually the string voltage may drop out of the inverter s operating window. For analyses of shading effect, shading was done on both the panels and power was measured. The readings for single cell shaded, two cell shaded, four cell shaded and nine cell shaded were observed for both types of panels i.e. Polycrystalline and monocrystalline panel. Both panels were compared on the basis of power obtained during shading. Fig. 3.18: Analysis of shading effect To analyze shading effect voltage and current was observed when different cell were shaded. Shading was done using cardboard or any hard thing and readings were taken for 0 cell shading, 1 cell shading,2 cell shading and 9 cell shading. Both panels were affected in different way by shading.

38 Fig 3.19: Experimental setup for one cell shading (polycrystalline panel) Fig 3.20: Experimental Setup for full row shading (polycrystalline panel)

39 Fig 3.21: Experimental setup for one cell shading (monocrystalline panel) Fig 3.22: Experimental setup for full row shading (monocrystalline panel)

40 3.3.4Effect of Increase of Temperature on PV Module Power The solar cells are sensitive to temperature. Increases in temperature reduce the band gap of a semiconductor, thereby effecting most of the semiconductor material parameters. The decrease in the band gap of a semiconductor with increasing temperature can be viewed as increasing the energy of the electrons in the material. Lower energy is therefore needed to break the bond. In the bond model of a semiconductor band gap, reduction in the bond energy also reduces the band gap. Therefore increasing the temperature reduces the band gap. In a solar cell, the parameter most affected by an increase in temperature is the open-circuit voltage. The short-circuit current, I sc, increases slightly with temperature, since the band gap energy decreases. Assuming panel s exposure to sunlight the effect of increase of temperature on the efficiency and the power, voltage current readings was observed at different temperature. Both the panels got affected by increase in temperature in different way. The connection on control board is shown below: Fig 3.23: Circuit diagram to analyze effect of increase of temperature Both panels were exposed to sunlight and readings were taken for different temperature i.e., 25 C, 50 C and 75 C for both panels. As shown in below figure module temperature refers to module temperature which is 25 C greater than ambient temperature. Module current shows short circuit current in amperes and module voltage shows open circuit voltage in volts. Temperature was measured and voltage current was observed.

41 Fig 3.24Display showing temperature, current and voltage of panel 3.3.5Space Efficiency The space efficiency refers to achieve the maximum of power output with the minimum of area.if we had one polycrystalline and one monocrystalline solar panel, both rated 40 watt, they would generate the same amount of electricity, but the one made of monocrystalline silicon would take up less space. Basically one square meter of monocrystalline solar cells will generate around190w and one square meter of polycrystalline solar cells will generate around 180W. Monocrystalline silicon solar panels are space-efficient. Since these solar panels yield the highest power outputs, they also require the least amount of space compared to any other types. In. this work, space efficiency of monocrystalline and polycrystalline cells were examined by standard method.