Study and Development of a Photovoltaic Panel Simulator
Contents
1. Ww Dar von en 4A 0 I I CAN damad Voltage at Max Power 17 198 n diode factor 41 025 ma O AN I vg Fill Factor 1 1 14 0 769654 o o o Eor Solar Cells 136 o Efficiency 11 9283 c ec rnm O l I I I I I I I I j I 8 9 10 11 12 13 14 15 16 17 18 19 20 21 100 Voltage V voc T min Want to change cell in series Want to change cell in parallel Control de Rs Cells in series Cells in parallel Area m 2 f PR 0 r 36 r l 36 4 A P Figure 50 Solarex MSX 60 for STC from simulator 40 Parameters Manufacturer Data Simulator Results Percentage Deviation Vmp V 17 1 17 19 0 526 Imp A 3 5 3 58 2 2857 Pmax W 60 61 7 2 84 Efficiency 12 11 928 0 6 Table 4 Experimental results for Solarex MSX 60 5 4 Testing conclusions There have been done a series of trials to test the proper operation of the simulator Logically when irradiation increases and the operating temperature decreases the maximum power that the panel can deliver to the load is greater Moreover the accuracy of the panel output characteristics differ little from reality We analyzed the behavior of the panel at the knee of the curve the most interesting place since it is where the maximum power occurs It has been shown that the errors obtained are of approximately 5 of the expected value But these errors are very different between tests so2. These cells are combined in series to increase voltage V or parallel to increase current without increasing voltage The current generated is stored in batteries and converted to AC through inverters Fig 5 Solar Irradiance Solar ia Electric Charge Panel s IT ASG Current Controller Lag h andior pj Battery per System Inverter AC Power C DC Power C Figure 5 Off grid PV system 2 2 1 The Cell Much of the electrical characteristics of photovoltaic solar cells depend on the physical properties of semiconductor materials used in its manufacture and industrial processes applied When a photon is absorbed by a semiconductor material increases the energy of the valence band electrons and makes the jump into the conduction band resulting in free electrons This occurs when the incident photon energy is greater than the band gap semiconductor Fig 6 Upon this jump the holes generated in the crystal lattice the burden associated with these gaps should be the same as the electron but of opposite sign thus creating hole electron pair Density of states At the junction photovoltaic cells is the most widely used pn junction in which the band gap Eg of semiconductor materials is the same By combining both types of materials the diffusion of electrons in the p lead to the recombination of electrons and holes causing the appearance of negatively charged ions in this area The loss of negative cha
3. diode Factor C K i output selection H model type e PI i GPIB address ab ID query EG error query mi error in gt Annex 2 LabVIEW Block Diagram of With Hardware vi 48 E output on off eH PM 285 PM 285 EE METER E Aib AA al E FROTECT ZH clear status IESUS Ez instrument state overcurrent protection reprogramming delay DEL gt I inicial PDBL c4 KE EEE Sa DBL Voltage Output Matrix DBL Current Output Matrix supply voltage matrix Dj FDBL Serer errr ee Supply voltage cutoff subtraction fst Cutoff of subtraction is O PDBL N decimal D 10 n use n Di Supply power cutoff Supply current cutoff PDBL stop TENG
4. not affected t hd c Q im pus 3 0 HR Power W UJ O Ns 24 N O Voltage V Figure 25 P V characteristic as a function of the number of cells in series 20 The Fig 26 and Fig 27 are providing information on associations in parallel The resulting intensity of the panel increases proportionally to the number of cells while the voltage is not affected It is observed that the power supplied by the panel is equal in both cases since a proportional increase of the current or voltage 80 rn t hd c Q im im 3 0 60 ON oo TTT 0 0 1 0 2 0 3 0 4 0 5 0 6 0 0 7 Voltage V Figure 26 I V characteristic as a function of the number of cells in parallel IN Power W UJ 0 3 0 4 Voltage V Figure 27 P V characteristic as a function of the number of cells in parallel 21 Chapter 4 Software Design in LabVIEW LabVIEW is a platform on which the programmer using graphical language G and the virtual instrumentation can simulate the behavior of equipment that are used in the area of electrical engineering The user will reduce costs since LabVIEW can simulate hundreds of systems before to purchase the devices LabVIEW offers a high level graphic programming language and a friendly environment The tasks can be executed much faster than in other languages and it is quite easy for the programmer to create in a fast way a simulator easy to understan
5. not vary more However as caution the number of iterations is 20 in case if it takes longer to reach convergence Apart from the creation of the curves they were created three conditional structures associated with their corresponding switches that are disable by default The first is to have direct control of the series resistance although this depends on the temperature so that the user could see the changes in the curve if this increases or decreases The second is created if the user wants to change the number of cells in series of the panel if is already determined the number of cells Ns given by the manufacturer The third is another control to change the number of cells in parallel 4 2 Power Supply The power supply is a vital part of the project because it will be responsible for generating the voltage and current of the simulated panel This section attempts to explain its functioning The source will mimic the IV curve done by the algorithm and will simulate the photovoltaic panel as close as possible to the reality The programmable power supply allows controlling and maintaining constant the output voltage or output current of the load to which it is connected 27 When the source operates in continuous current mode will give a constant current to the load at different voltages which will be determined by the load connected to the source according to Ohm s law V I R Fig 34 On the other hand when acting in t
6. 4 Master Thesis Structure sesescssesesecsesesesesesesesesesescessesesececeseseseseseseo 4 Figure 5 Off orid PV System 2 smart Qe bo ago eb ead possa a bei ad ssa mad bora te buco s D Figure 6 Band Gap in Semiconductors 3 edited eese 6 Fieure 7 Pnotovottale Cell Scheme pA 6 Figure 8 The Shockley Queisser Limit or the Efficiency of a Solar Cell 3 edited 7 Figure 9 Breakdown of the Causes for the Shockley Queisser limit 4 edited 7 Figure 10 Solar Radiation Spectrum 5 edited eere n 8 Figure 11 Best Research Cell Efficiencies 6 eee mnn 10 Figure 12 Two diode equivalent circuit of a PV cell c eeeeeeeeeeeeeee 11 Figure 13 One diode equivalent circuit of a PV cell eee 12 Figure 14 A Typical current voltage I V curve for a solar cell eese 14 Figure 15 A Typical power voltage P V curve for a solar cell 15 Figure 16 I V characteristic as a function of irradiance eee cceeeeecceeeeeees 16 Figure 17 P V characteristic as a function of irradiance 16 Figure 18 I V characteristic as a function of operating temperature 17 Figure 19 P V characteristic as a function of operating temperature 17 Figure 20 I V characteristic
7. In this work has been developed a photovoltaic emulator able to test photovoltaic inverters and MPPT algorithms in conditions close to real Currently there are equipment that can perform these testing but are based on actual solar panels that are illuminated by the sun or artificial light source the problem with this type of emulators is directly dependent on climatic conditions in the time of testing in addition to poor performance and they cannot get high power from a single panel The software developed in LabVIEW to control a power source for this has the characteristics of a photovoltaic panel Given a user specified load the emulator displays an output voltage and current for the type of panel to be simulated and the temperature and irradiation conditions desired This will test and improve the photovoltaic system components such as inverters or banks of batteries The software can be used to analyze the functioning of photovoltaic module and helps to do a system design and get the performance of the available modules on the market without the need of purchasing them for tests Due to its good precision can be simulated several types of panels 42 6 2 Research and Improvements Areas One way to improve the simulator will be implementing a data acquisition system and integrate it in the software A temperature sensor a light intensity meter and a conventional solar panel can vary the temperature and irradiance of the simulator over a
8. a function of incident solar irradiance The curves correspond to 1000 W m 750 W m 500 W m 250 W m a 25 C It is noted of course that with increasing incident light power more power is generated N UT 1 SUN gd zs ese 0 5 Suns LN m BL MW LN 10 15 20 Voltage V 2 E o 2 fa 3 Q E UT Figure 16 I V characteristic as a function of irradiance O I Sun 5 Suns Power W UJ O ese 0 5 Suns 0 25 Suns Voltage V Figure 17 P V characteristic as a function of irradiance 16 In Fig 18 and Fig 19 make sure that the temperature adversely affects the power of the cell because even slightly increase the intensity voltage loss is more pronounced This effect is observed in the hour of greatest irradiance the power decreases slightly due to increased temperature t c Q im im 3 0 Voltage V Figure 18 I V characteristic as a function of operating temperature Power W N QJ B O O O m O Voltage V Figure 19 P V characteristic as a function of operating temperature 17 The ideality factor also known as the quality factor varies from 1 to 2 depending on the fabrication process and semiconductor material see in Fig 20 and Fig 21 Show that with increasing the diode quality factor reduces the maximum power that the panel could provide In addition deteriorating fill factor because although Isc and Voc does n
9. data taken from above to calculate the fill factor of the panel with the equation 3 16 Finally the SuvVI 4 Fig 32 calculates the efficiency of the panel according to maximum power irradiation and a defined area with the equation 3 17 24 DELE Elementary Charge C vocl DEL Em Icc1 mi DELE E5 Boltzmann E 1 38E 23 gt AM Rs gt gt gt Ns dwdi vac EE IL B 1 va Temperature Ki DEC per gt Figure 29 SubVI 1 25 voltage current Current at Max Power ILDEL E voltage at Max Power DEL voltage at Open Circuit DEL Current at Short Circuit PEL Figure 31 SubVI 3 Power Max power per EB num x Ta ph Eres A PESE Power N voltage v i gt Current at Max Power gt Hi voltage at Max Power far 555 Current A Voltage v B B HJEL max voltage voc E B Edi POEL max Current Tec E Figure 30 SubVI 2 Maximum Power DEL gt FDEL Fill Factor arca EH G LDELE gt OBL Efficiency Figure 32 SubVI 4 26 TAKES THE VALUES CREATES THE SPECIFIED BY THE USER VOLTAGE SAMPLING CALCULATE CELL COEFFICIENTS TRUE STARTS AT ZERO 7 NEWTON s METHOD 1 20 INTENSITY FALSE CALCULATES EV CURVE OUTPUT CURRENT MATRIX P V CURVE Figure 33 Algorithm used to obtain the IV curve It is found that for the MX 60 panel from the second iteration the intensity value does
10. de radia o solar e da temperatura Da mesma forma a aplica o fornece outras informa es teis tais como a pot ncia desenvolvida em qualquer instante o fator fill ou a sua efici ncia para uma determinada rea O resultado final um emulador que corresponde muito bem realidade quando comparado com as curvas caracter sticas fornecidas pelo fabricante do painel e com os determinados pelo simulador Abstract The rising cost of conventional energy sources and their environmental impact requires the implementation of renewable energies such the photovoltaic energy which had increased exponentially in the last years Thus it is important to develop emulators that allow the testing and improving these systems The motivation corresponds to the need for a simulator able to test PV inverters and their MPPT algorithms in conditions near to real time During the work to prepare the dissertation various topics regarding the photovoltaic panel LabVIEW programming and programmable power supply were addressed The initial part of the thesis deals with a literature review of photovoltaic energy and the model of photovoltaic array In particular is presented the theoretical basis of the elements involved and then deal with the programming and application development that will control the simulator Through this it became possible to build a test platform that allowed emulate one solar panel The simulator calculates the voltage current chara
11. efficiency is more profitable Thin film Solar Cell TFSC They are manufactured by placing a thin film photovoltaic material on a wide variety of surfaces These are less efficient and less costly to produce than the previous two types These solar panels are built in roll form eliminating many costly processes involved in manufacturing of the conventional panels These cells are categorized according to the photovoltaic material used Amorphous Silicon They not follow any crystal structure His power is reduced over time especially during the first months after which are basically stable They are used for small electronic devices These cells present in the laboratory efficiencies of up to 13 with commercial modules of about 8 23 Cadmium Telluride It is usually sandwiched with cadmium sulfide to form a p n junction photovoltaic solar cell CdTe cells use a n i p structure Laboratory performance 16 and 8 commercial modules 23 Copper Indium Diselenide Laboratory performance close to 17 and 9 commercial modules 23 Efficiency Dye sensitized Solar Cell It is based on a semiconductor formed between a photo sensitized anode and an electrolyte a photo electrochemical system Gallium Arsenide One of the most efficient consisting of a mixture of gallium and arsenic Gallium is a byproduct of the smelting of other metals such as aluminum and zinc Laboratory performance of 25 7 and 20 commercial modules 23 Mul
12. hardware needed or he only wants to view the characteristic curve of a panel at the market he has to use the one called Without hardware VI The advantages of this program is that don t have limitations in order to emulate any type of panels since the program it is only mathematical based it don t have the limitations of the power supply characteristics However the main objective of the thesis is to create a simulator through the power supply so from here we analyze the program with hardware 33 Below it is explained how to understand the LabVIEW front panel of the simulator Fig 43 The interface without hardware is analogous to this so is explained the most complex Calculate Icc at T2 with coefficient Alpha 5 071 Gp icc T2 0 936 alpha 15 na a Panel parameters T1 STC K 298 T2 kK an 348 Tec STC T1 0 9 2 Tec at Tz EN 3 07 voc at Ti E n diode Factor HE t vg 1 17 Solar Cells 36 2 Voc T min 100 t Area mo 0 144 Current T 1 75 1 65 0 6 0 55 E un a gt I Diesen 1 25 As Control de Rs To a Figure 43 Environmental Conditions Irradiation amp Suns 1 Sun 1000 ime Co RR Temperature 27 O A I I I I I I lp 2s Wise rs cx esse 15 2 40 20 0 ry Afi a r E g l I I I I I I I I I I I I I I ud dl des PIS ole l l ml a0 l de cR voltage V Want to change cell in series Cells i
13. the supply voltage with the new values obtained This method works in all regions of the curve Both the line of resistance as the curve will have a very FINDS INTERSECTION POINT high number of points for the two lines intersect at a particular point Fig 38 If the resistance is higher the line will approach more to the open circuit point In my case the line sweeps from 0 ohm SET POWER SUPPLY VOLTAGE TO THE ONE wants to approach more to the Voc point only have to OF THE INTERSECTION in the Isc point to the 100 ohms near the Voc point If the user increase the resistance This is shown in figure 40 Figure 38 Algorithm used to set the supply 30 For the understanding of this section is recommended the view of the annex 2 These were the steps taken 132 Measured current DELA Measured voltage DEL V Find a LabVIEW driver for PM2832 source Set the source to synchronize the communication port channel chosen GPIB with LabVIEW Initialize the source and set as 11076 of the short circuit current the initial intensity Read the output current and voltage source which depend on the load Taking the above data to interpolate a straight V 1 Rin the SubVI 5 Fig 39 Subtract the current array of the curve with the current array of the line to find a point where they become zero Find that point in the voltage array of the curve Enter the voltage value of the intersection at the source of power Repeat t
14. with coefficient Alpha C Max Voltage Voc 18 916 T2 K Max Current Icc 348 0 38 Icc STC T1 Max Power pps 0 4 5 76544 Icc at T2 Current at Max Power FR r 3 92 A 0 35872t AA JAMOd Voc at T1 Voltage at Max Power 521 1 16 072 Supply current cutofF n diode factor i 0 358637 20 1 025 l Supply voltage cutoff vg 16 076 01 14 i Supply power cutoff Solar Cells 5 76544 f 1 r 36 4 Fill Factor 1 0 E I I I I I I I I I I I I I I I Voc T min 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Malin m 100 voltage V Efficiency Area m 2 Want to change cell in series Want to change cell in parallel 11 1453 00 5173 C 9 C e C e Control de Rs Cells in series Cells in parallel o 236 136 Figure 49 Solarex MSX 60 for 100W m2 from simulator Environmental Conditions Irradiation G Suns 1 Sun 1000W m2 Temperature 9C A o dd I I I Lu 1 1 1 I 0 0 25 05 075 1 1 25 1 5 1 75 2 40 20 0 20 40 60 80 100 alpha 15 pec O D Ic T2 3 9235 n Panel parameters Output parameters T1 STC K 3 87 11298 3 6 i 3 4 D 21 098 ES 3 2 348 P 3 Max Current Icc Icc STC T1 2 8 3 8 m 3i 8 2 5 Calculate Icc at T2 with coefficient Alpha C Max Voltage Voc 2 4 Max Power Icc at T2 61 705 f 13 92 IN co N N I I L Current at Max Power 3 58792 Voc at Ti 821 1 e ro P bs vw
15. work and a value of Vdcmax which must not be exceeded even under open circuit and the minimum temperature of the PV module 70 q Pmax o 10 15 Vmax a 25 Voltage V Figure 15 A Typical power voltage P V curve for a PV module For practical applications the question arises at which values of Vmpp an inverter should reasonably be tested and which interval the STC array voltages Vmppa stc and Voca stc of the PV plant should be chosen The simulator can calculate the maximum power point of the photovoltaic module chosen with the desired environmental conditions Thus you can connect the inverter to the power source programed and analyze his behavior The following graphics are made with the application developed in LabVIEW without hardware and then exported to an Excel workbook to improve its design and understandins The panel chosen for the analysis of curves is the MX 60 The starting parameters used are for the standard conditions STC Later we will analyze the process carried out to program the software STC Standard Conditions for testing panels solar radiation of 1000 W m PV cell temperature 25 C spectral value 1 5 AM It should be noted that the radiation is almost always less than 1000 Watts m2 the temperature often exceeds 25 C while the spectral value can vary between 0 7 high above sea level and very large values 15 The Fig 16 and Fig 17 show the dependence of the photovoltaic cells as
16. 2343 EG EE EE 1 5 Supply power cutoff nd 10 7372 Supply voltage cutoff 18 76 0 5 Fill Factor 1 zi I I I I I I I I I I I I I SJ ey alfa ah Se ales Gly alo leo als ae Zusz rd Fer a us Mine Voltage V Efficiency Want to change cell in series Want to change cell in parallel 10 9832 Control de Rs Cells in series Cells in parallel o 136 Jl 36 Figure 46 Solarex MSX 10 for STC from simulator Manufacturer Data Simulator Results Percentage Deviation 17 1 18 76 9 707 0 58 0 572 1 38 10 10 7372 7 372 11 10 9832 0 1527 Table 3 Experimental Results for Solarex MSX10 38 Figure 48 Solarex MSX 10 for different temperatures from simulator 5 3 3 Solarex MSX60 9 Since this panel has a short circuit current more than 2A we can t simulate with the supply but by decreasing the radiation of 1000W m2 to for example 100W m2 simulated panel will decrease his short circuit current and it is shown that works perfectly within their ranks Also the comparative analysis is done through the without hardware simulator as in the previous case with the Sharp panel to determine its precision 39 Envitonmental Conditions Irradiation G Suns 1 Sun 1000W fmz Temperature 9C o TT 1 1 5 I I I I I I I I I i 0 02505075 1 1 5 L5 1 75 2 40 20 0 20 40 60 80 100 alpha 19 065 OC D kee T2 3 9235 a Panel parameters Output parameters T1 STC K 1298 Calculate Icc at T2
17. FACULDADE DE ENGENHARIA DA UNIVERSIDADE DO PORTO Study and Development of a Photovoltaic Panel Simulator Pablo Gonz lez Bernal Master in Electrical and Computers Engineering Supervisor Rui Esteves Ara jo PhD January 2012 Pablo Gonz lez Bernal 2012 Resumo O aumento do custo da energia das fontes convencionais e o seu impacto ambiental requer a implementa o de energias renov veis tais como a energia fotovoltaica a qual tem aumentado exponencialmente nos ltimos anos Assim importante desenvolver simuladores que permitam o ensaio e a melhoria destes sistemas A essa motiva o corresponde necessidade de dispor de um simulador capaz de testar inversores fotovoltaicos e os seus algoritmos de MPPT em condi es pr ximas das reais Durante o trabalho de prepara o da disserta o v rios t picos foram endere ados tal como os modelos dos paineis fotovoltaicos a programa o em LabVIEW e a utiliza o de fontes de tens o program veis A parte inicial da tese dedicada revis o bibliogr fica da energia fotovoltaica e sua modela o Em particular apresentada a base te rica dos elementos envolvidos bem como a programa o da aplica o que controla o simulador Com isso tornou se possivel construir uma plataforma de teste que permitiu emular um painel fotovoltaico O simulador determina a curva carateristica de tens o corrente atraves das informa es fornecidas pelo fabricante do nivel
18. In LabVIEW Tools Measurement and automation explorer My system Devices and Interfaces GPIBO Then change the primary address to a number between 1 and 30 2 In the Philips Fluke power supply press the AUX as many times as necessary to display ADDRESS and enter the number chosen in LabVIEW 32 The power supply Philips Fluke PM 2832 launch date was from January of 1997 so it is quite old now is discontinued but was very useful to test the concept Finally rheostat of 100 ohms is connected to the power supply to have the variable resistor The figure 42 shows a general view of the workplace and the switchgear i res Ku o hund E IL md o am Ll ee EGG se qm ORA i i 1 Siin nem a 4 Pts Figure 42 Workplace 5 2 User Guide The user could download the program at http paginas fe up pt ext11140 pasge id 23 called LabVIEW Simulator rar inside the user will see two programs and a folder called SubVI with the files necessary for the operation of these Also there are the National Instruments Drivers for the Philips Fluke power supply This is the folder where the drivers must be introduced C Program Files x86 National Instruments LabVIEW 201 1Vinstr lib The user could use two programs one that support the hardware With Hardware vi and the other one that it is develop without hardware Without Hardware vi If the user don t have the
19. W connected only during the month of June in 2010 in Germany Germany is the country added more capacity in PV in 2010 followed by Italy Czech Republic Japan and the United States Germany is also the country with the largest installed capacity of PV 44 followed by Spain 10 Japan 9 Italy 9 and USA 6 Europe as you can see accounts for over 75 of global installed capacity of PV Fig 2 In total the new capacity installed in 2010 the volume of the accumulated total power is on the edge of adding the 40 000 MW At the beginning of the decade in 2000 the total power installed globally was only of 1 500 MW Also in 2010 became the first renewable power in Europe with a 22 share ahead of the wind 17 and second only to the gas 52 In total photovoltaic now account for 3 of the installed power in the EU Yet all renewable sources excluding the large scale hydropower contributed only 3 3 of global electricity production 10 Rest of the World South Korea 2 Other EU 2 Belgium 2 United States China France Czech Republic 5 Figure 2 Solar PV Capacity 2010 1 The PV power installed capacity by 2010 is 40 GWp 17 GWp compared to 2009 Was planned for November 2011 to install over 24 GW so the global capacity will now be exceeded more than 64 GW Photovoltaic energy is still the fastest growing renewable annual average between 2005 and 2010 49 Fig 3 ae a 40 gt fe 30 Pr a
20. ameters at maximum power and the efficiency calculated with the area Parameters Vmp V Imp A Pmax W Efficiency Manufacturer Data Simulator Results Percentage Deviation 27 4 26 058 5 102 7 6 7 907 4 039 208 206 055 0 936 14 13 9038 0 6872 Table 2 Experimental Results for SHARP UN U208FC 37 5 3 2 Solarex MSX10 8 This panel meets all requirements with the power supply The rheostat has been changed moving the resistance line until meet the intersection point with the I V curve that provides the greatest power So the supply is set up with the theoretical max power of the simulated panel Calculate Icc at T2 with coefficient Alpha C Environmental Conditions Irradiation G Suns 1 Sun 1000W m2 Temperature 9C Mes EFE 114 Sara I I I I 1 I I I I I RS 08040803 al ole up mem a orm As Mage E zu san 20 40 60 80 100 alpha J 0 065 LD Icc T2 0 6195 z 1 4 Panel parameters T1 STC K 1298 T2 K 348 Icc STC T1 40 6 Icc at T2 203 92 A Voc at T1 221 1 n diode Factor 2 1 025 A eg 1 14 Solar Cells 136 Voc T min 100 A Area m 2 20 0 09776 A Parameters Vmp V Imp A Pmax W Efficiency Output parameters Max Voltage Voc 21 098 Max Current Icc 0 6 Max Power 10 7372 6 5 EID ics 4 5 Current at Max Power 0 57198 A smog Voltage at Max Power 18 772 mu Supply current cutoff 3 5 0 57
21. and free electrons increase due to thermal ionization phenomenon The panel exposure to sunlight causes the increase of temperature of the cells representing a small increase in intensity because the band gap decreases with temperature Yet at the same time there is a larger decrease in the value of the voltage because it is maximum and of equal value than the band gap when the temperature is absolute zero So the overall effect is the reduction of the power supplied by the panel The power will therefore increase with increasing radiation and lower temperature 2 2 Types of Photovoltaic Cells There are commercially available several types of PV cells Here it is given a brief explanation of what are their main advantages and disadvantages Currently are emerging continuously new technologies to market so here it will not appear all that exist but the best known Monocrystalline Silicon Sections are based on a perfectly crystallized silicon bar in one piece Efficiency above 24 in laboratory but in reality commercial panels are around 15 23 They are more expensive heavier and more fragile to shocks Polycrystalline Silicon The crystallization process of silicon is different from before Sections are based on a silicon bar that is structured as small disordered crystals These cells present an efficiency of up to 19 in the laboratory and about 14 in the modules market 23 The cost is lower than the monocrystalline so that their
22. are the controls of the operating temperature of the panel and the solar irradiation which are by default in the STC conditions 25 C 1000W m2 Just below the graph it s the STOP bottom that ends the program also there is a direct control of the series resistance of the panel and another two controls to change the number of cells in series or parallel All three are disable by default It s important that if the user want to change the number of cells it have to be the original number of cells in series of the panel to simulate The right side of the graph is for the column of the output parameters These indicators depend on the variables chosen The values called with cutoff are the ones that correspond to the values of the supply So if the user wants to simulate the maximum power allowed by the panel under the environmental conditions has to modify the resistance until the value of Max Power it s the same as the value of Supply Power cutoff Finally at the bottom right is the legend of the chart These are the steps required to use the simulator e Connect the supply to the computer via the GPIB port e Connect the supply to the resistor e Open WITH HARDWARE vi e Enter the desired input parameters Panel parameters and environment conditions e Press RUN e Vary the resistance to find the desired operating point e Press STOP to end The advantages of this program is that change in real time You don t have to STOP the program t
23. as a function of diode quality factor sse 18 Figure 21 P V characteristic as a function of diode quality factor 18 Figure 22 I V characteristic as a function of series resistance 19 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 Figure 37 Figure 38 Figure 39 Figure 40 Figure 41 Figure 42 Figure 43 Figure 44 Figure 45 Figure 46 Figure 47 Figure 48 Figure 49 Figure 50 Figure 51 P V characteristic as a function of series resistance 19 V characteristic as a function of the number of cells in series 20 P V characteristic as a function of the number of cells in series 20 I V characteristic as a function of the number of cells in parallel 21 P V characteristic as a function of the number of cells in parallel 21 Inputs and outputs of the Matlab simulator eere 23 SUD VIM cora ida E E DD SIRENE ass 25 UV Zn a EE DU ga OI a pas doadas 26 SUS ae 26 SE TE EE EE ER adie sled Gator 26 Algorithm Used to Obtain the IV Curve ccc cee ccc ee cece eee cceeecceeecceeees 2 Output of a Constant Voltage left and Constant Current right Supply 28 Output Characteristic of a Constant Voltage Constant Current Supp
24. btaining IV Curve Lu os seek e quand NENNT E ER Danca a RH SY US RE ER a A EUR 22 2 2 Power SUP PSP AD AUDI ER RUE 27 4 3 Hardware Implementation oonnnvvnnnevnnnnvnnnnennnnunennnennnnenennunennneeennee 30 CIADLER PE aN 32 Experimental Results sage 32 5 1 Workplace and Switchgear Used uunuvnnnnnvnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnene 32 GE User QUO m 33 TETEN 36 5 3 1 Sharp Electronics Corporation NU U208FC 37 5 9 2 9 SOlarex NT 38 29 2919 5 SOEX MA GO osos eee andina Und RE NAA ENEE RE CNS CRUS REA MUERE a eh 39 5 4 STES UNS CONCUSSIONS Lens 41 EDAD Or NETTE NE RE EE EE 42 Conclusions and Future Research Areas e eeeeee eee eee eene 42 H CORE iio coc 42 6 2 Research and Improvements reas arnnnnvnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnenene 43 RET OM f ippe c rr 44 OG CJ ENE OE ar samademcecmeaeneacmaceaesacmue ares 46 1 LabVIEW Block Diagram of Without Hardware vi aonnnnnnvennnnnvvnnnnnnennnneee 47 2 LabVIEW Block Diagram of With Hardware vi esses nnn 48 viii List of Figures Figure 1 Renewable Power Capacities 2010 1 Lecce 1 Figure 2 Solar PV Capacity 2010 Tussa paga 2 Figure 3 Solar PV Existing World Capacity 1995 2010 1 2 Figure
25. cteristic curve through the construction details of the panel solar radiation levels and temperature Likewise the application provides other useful information such as the power developed at any time the fill factor or its efficiency in a given area The result is a reliable simulator which fits very well with reality when are compared the characteristics curves provided by the manufacturer and those determined by the simulator vi Index RESUMO see iii DUNN V lj EE Ene vii He RT T TN ix PTE ETT I I IE UENIRE xi Abbreviations and Symbols saus xii Chapter Issues ETC NNN 1 IMEFOGUGUION Re 1 141 Analysis of Current SITUATION as t eS oov cba need asas aii aaa ede e revelan edo ES ES 1 VESEN 3 13 Master Thesis SIE suas aaa EN ARR E RENNES REN NERIS REA NES RON NU SE RUN be 3 CRADLEL e TE ERE 5 Fundamentals of Photovoltaic Energy cccccccccccccccceccceccceccceeccs 5 22 TE Ca 6 211 Semiconductor LIMI aars did REEE EKO Rod d SUO A MEUS 7 2212 dBA enn 8 STATE NNN 9 2 2 TYPES OF PNOLOVOILAIC GEUS ez es s tessek s s dedi Eo keksz coda dama E EPATP lidas k 9 vil CRADLE Saa 11 Modeling or solar panel assina RE UR E 11 EEA MOC Pm 11 3 1 1 Equivalent Circuit of Two Diodes 11 3 1 2 Equivalent Circuit of One Diode ecce 12 MENN 14 TT NNN 22 Software Design in LabVIEW vvs 22 4 1 gt O
26. ctrical model based on well known electrical components An ideal cell can be modeled as a current supply connected in parallel to a diode The PV simulator must have a current and output voltage given by the diode equivalent model as close as possible to the real system or to the characteristics provided by manufacturers 3 1 1 Equivalent circuit of two diodes 16 The most complete model consists of a current source whose intensity I is directly proportional to radiation G in parallel with two diodes one that simulates the diffusion of minority charge and the other corresponding to the recombination of the junction The parallel resistance Rsh represents the leakage current losses and the series resistor Rs represents the internal losses of the cell the heat losses by Joule effect due to current flow impurities and losses among cell connections Fig 12 RL Figure 12 Two diode equivalent circuit of a PV cell 11 I I Ip1 Ip2 su 3 1 q V Rs I g V Rs I V ReI I I lopi e niKT 1 Iop2 e n2 K T 1 v 3 2 SH 3 1 2 Equivalent circuit of one diode 17 The model that will work is a simplified version of this but that fits quite well to reality and greatly facilitates the process of computing and programming In this ideal model the current source and the diode represent the conversion of solar energy in electric energy The simplified model is based on a current source in parallel
27. d 25 23 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Figure 3 Solar PV Existing World Capacity 1995 2010 1 In a short term is expected that photovoltaic energy will be one of the fastest growing market This growth creates new problems for manufacturers since testing a large number of photovoltaic modules before installation is complicated Currently testing for the connected equipment such as inverters we use a real panel This leads to a problem since the oscillations of temperature and radiation is difficult to isolate the variables that affect the panel performance Using a programmed voltage source the testing procedures can be performed using constant values of both voltage and current But this is not entirely similar to the operation of the panel since it does not take into account climatic conditions The simulator developed would be the midpoint in order to perform these measurements based on the characteristics of the panel radiation and temperature but giving constant values of voltage and current So this simulator is a more sophisticated system than the other two in order to identify the inverters needed for installation The user then can identify the factors that affect performance of the panel analyzing the resulting curve by changing variables Thus it is also more accurate measurements made in other components connected to the photovoltaic panel This simulator allows you to t
28. d for its intuitive graphical interface What concern us it is to build a simulator tool to simulate photovoltaic panels supplyins with the power supply controlled an electric load One of the objectives is to put the simulation of the PV panel close to the maximum power point thus delivering to the load the highest possible quantity of energy The MPP tracking is obtained by connecting a DC DC converter between the solar panels and the load which could be the electric grid or a battery bank In real situation the additional energy is stored in batteries and can be used later when there is not enough sunlight and the PV panel cannot deliver enough energy to supply the grid 4 1 Obtaining I V Curve This section explains how to make the programming algorithm used to create the software The algorithm is based on which is an example done in Matlab whose script is presented below Its parameters are the voltage at the panel terminals radiation and the operating temperature for a MX 60 panel Fig 28 The user will introduce the climatic conditions and the panel parameters provided by manufacturer and the program will create the voltage sampling 22 PARAMETERS OF THE SOLAR PANEL VOLTAGE gt Va IRRADIANCE gt Suns Ia CURRENT TEMPERATURE gt Tac Figure 28 Inputs and outputs of the Matlab simulator function Ia solar Va Suns Tac 6For solar panel MSX 60 Calculate the current through the voltage irradiation and tempera
29. day to determine the efficiency of longer term panel Light Source Solar Panel VA 2 Light Intensity Meter Temperature Sensor ETSI Figure 51 Example of a Photovoltaic Test System 10 It can be add a database with the parameters of many panels so that the user does not have to know the characteristics of each panel to simulate you can simply look for the panel within a list and LabVIEW are responsible for enter the relevant data Another way to continue the work will be to introduce a number of parameters to make the panel work in terms of a time and place For example determining a month of the year time of day and location for placement of the panel gives a result dependent on the actual conditions of the environment It could also take into account the effect produced by the partial shading because a photovoltaic generation system with X panels have a level of irradiation heterogeneous especially at dawn or sunset or sporadically over a cloud It could also investigate a custom power supply for the simulator to be able to simulate most of the solar panels reducing hardware costs 43 References 1 2 3 4 5 6 7 8 9 Ren21 Renewables 2011 Global Status Report 11 July 2011 http www ren21 net Portals 97 documents GSR REN21_GSR2011 pdf Hawk Energy Solutions Solar PV System Energy 2010 http www solar pv system com Solar PV System Solar PV Energy html Wik
30. do not follow a particular pattern Errors can come as a result of simplification of the electric model of the panel since it is not taken into account the parallel resistance of the leakage currents Furthermore it has been taken that the values of the series resistance of each panel are the same and this is not true For all three panels are taken the series resistance of MSX60 Solarex panel giving rise to greater errors with it Also this explains the error is so low in this panel The reason for not changing the series resistance is because it is a piece of information with difficult access which cannot be found in a simplified datasheet as those found online However if the user has the data of the value of the series resistance of the panel to emulate he has only to activate the Boolean located at the bottom left of the simulator and input the data there In conclusion the simulator developed can emulate via a power supply with acceptable errors at least all the panels up to 20W leaving the panels with higher power a software simulation which does not allow the testing of photovoltaic equipment 41 Chapter 6 Conclusions and Future Research Areas 6 1 Conclusions The growing demand and implementation of photovoltaic power generation systems required to investigate and develop emulators that allow for testing and improving these systems The design of photovoltaic systems is complicated due to the variability of weather conditions
31. el goes into the CV mode refer to figure 5 5 7 This means that Vigag 8V and load becomes 8V 16Q 0 5A If Road decreases from 802 to 402 then Risad lt Ro so the output channel goes into the CC mode refer to figure 5 5 7 This means that ljyag 1A and Vigag becomes 1A x 40 4V The source with which they were tested in the laboratory is a Philips Fluke PM2832 Fig 36 EL ble power suppl 00V 2A 120W 60V 2A 120W me Figure 36 Philips Fluke PM2832 power supply The main characteristics are e Dual output E PM 2832 programmable power supply c0v 24 120W sov 2a 120w EL e Vmax 60V e Imax 2A oc STEP FLT CV CC OGP 4 e Pmax 120W nda le B Fieure 37 Philips Fluke PM2832 power supply detail 29 The problem with using this source is that we cannot simulate panels above open circuit voltage over 60 V which is not going to be a big limitation since most of the photovoltaic panels on the market fall within this range The panels with high power will have higher Voc like the SunPower E19 320 Solar panel that have an open circuit voltage of 64 8V and develops an output of 320 W The supply will not support this range of powers But the greater limitation will be by the short circuit current because the PV panel to simulate it may not exceed 2 A In conclusion only the PV panels with small powers can be simulated Because of this limitation is advisable to use another power source with maximum i
32. est hundreds of panels without having to purchase them besides being able to control their response to different conditions of temperature and radiation 1 2 Objectives The ultimate goal of this thesis is to build a solar panel emulator in the LabVIEW programming environment This has been developed the following steps 1 Understand the patterns and factors that affect the behavior of the photovoltaic cell 2 Determine the current voltage curve dependence of on these factors 3 Controlling a power source following the I V characteristic curve 4 Conclusions and proposals for future research 5 Make a project report and publish it on the web 1 3 Master Thesis Structure This master thesis is within the area of alternative energies focusing the same in the study and development of a computational tool aiming to simulate the PV modules performance under different operating conditions resulting from different levels of temperature and radiance The first chapter is an introduction that shows a general analysis of the situation nowadays in the market of photovoltaic systems In addition they are marked the desired objectives of the thesis The second chapter studies the general functioning and the limits of the photovoltaic cell to enter in the third chapter to capture this operation in his electrical equivalent circuit and analyze the variables that affect the behavior of the cell though the study of the l V and P V characteristic curve
33. he continuous voltage mode will give a constant voltage to the load at different intensities which will be determined similarly by the load Fig 34 CURRENT A CURRENT A Vs VOLTAGE V VOLTAGE V Figure 34 Output of a constant voltage left and constant current right supply The point where the power switch from one mode to another depends on the load connected to it in addition to the maximum current limit determined by the user When the load requires a greater amount of current than the limit set by the user then the source will change to the constant current mode The resistance Rc is the critical resistance that determines the operating mode where the source gives the maximum power Fig 35 RL Rc CC MODE CURRENT A RL gt RC CV MODE VOLTAGE V Figure 35 Output characteristic of a constant voltage constant current supply 28 Below is a numerical example taken from the user manual of the power supply used where you can see clearly what was explained above Example for a variable load resistance Veet Voltage programmed let Current programmed Road 22 to 2002 variable Required The V 4 and Il ezt parameter have been coupled for the selected output channel Iser 1A Programmed current becomes 1A Vset 8V Programmed voltage becomes 8V The crossover point resistance R V4 Iser 802 If Rag increases from 802 to 1602 then Riad gt Re so the output chann
34. he process and graphically display the cutoff point Measured voltage matrix FDEL voltage matrix Current matrix Current Measured current matrix voltage Original Data n ER arc 1D Interpolation Graph aml frr n z E Interp id i Be iben Figure 39 SubVI 5 Isc Imax 3 2 5 Current A m in P 0 5 10 15 Vmax Voc Voltage V Figure 40 Resistance line 31 Chapter 5 Experimental Results 5 1 Workplace and Switchgear Used Figure 41 Connection Scheme Much of the work performed and which required the use of switchgear for the hardware implementation and test of different photovoltaic panels has been developed in the laboratory 1105 from the department of electrical and computer engineering of FEUP The rest of the work was done on my home computer Figure 41 shows from top to bottom the connection scheme of the elements involved First the computer will be responsible for sending the signals through the LabVIEW Plug and Play Instrument Driver of the power supply to remotely control this one The connection with this will be done through a GPIB Controller for Hi Speed USB The connection GPIB USB HS IEEE 488 2 it is from National Instruments and you can download the drivers at his website 22 The computer and the power supply will have to be configured with the same GPIB communication channel which was quite tricky You must perform the following steps 1
35. hese panels in order to test all the possible variations of the simulator and check that it works correctly 36 5 3 1 Sharp Electronics Corporation NU U208FC 7 Current A Current Power vs Voltage Characteristics Figure 44 SHARP UN U208FC from data sheet 7 Cell Temperature 25 C Power W Voltage V Current vs Voltage Power vs Voltage At figure 44 we can see the curves corresponded to the UN U208FC SHARP panel from the datasheet This panel exceeds the limits of current of the power supply so the simulation of the curves is done with the program without hardware s we can see the simulator fig 45 conforms quite well to reality since the model given by the manufacturer notes at 25 C and 1000W m2 the maximum power in 208W while our simulator indicates a maximum power of 206 05 W for a diode quality factor of 1 026 and band gap of 1 11 V the values for monocrystalline silicon panels 9 g 250 1000W m2 200 800W m2 600W m2 190 400w m2 200W m2 100 Power 1000W m2 Power 800W m2 Power 600W m2 WM 50 im Power 400W m2 M Power 200W m2 O 30 35 Figure 45 SHARP UN U208FC for different irradiance from simulator The simulator plots the l V and P V curve at different irradiances quite similar than does in the datasheet with a slight error At table 2 are shown the percentage deviations of the electric par
36. ion Once the mathematical model takes all the input parameters is performed within the SubVI 1 fig 29 the calculation of I Rs and Ig with the equations 3 5 3 6 3 7 3 8 3 9 3 10 3 11 to arrive at this formula where we have just as unknown output current 1 for a sampling of voltages created by a loop gU RS I I Ig e n K T 1 4 1 We can see that this equation is not linear due to the characteristic equation of the diode So for the resolution is used Newton s method with successive iterations to be performed until the method has converged sufficiently FR f Xn DR 4 2 If we had used two diodes in the electrical model approximation this equation will be more complicated The resolution of the formula will give us an array of intensities depending on the array created from O volts to the maximum open circuit voltage allowed by the panel The two arrays enter the SubVI 2 Fig 30 to have the same number of elements and their values end up in court with the X axis since we only care what happens in the first quadrant You also get the maximum voltage Voc the maximum current Isc and create the scatter plot we created the IV curve Within this SubVI also multiply matrices and voltage to find another chart that indicates the power that can be developed based on the panel voltage determining the point of maximum power and the voltage and intensity where this occurs The SubVI 3 Fig 31 takes the
37. ion Taylor amp Francis 2006 Pages 141 186 15 Bishop Robert H Learning with LabVIEW 6i Prentice Hall 2001 16 F Adamo F Attivissimo M Spadavecchia Tool for Photovoltaic Panels Modeling and Testing Electrical and Electronic Measurements Laboratory DEE Polytechnic of Bari http ieeexplore ieee org stamp stamp jsp tp amp arnumber 5488070 17 Francisco M Gonzalez Longatt Model of Photovoltaic Module in Matlab II CIBELEC 2005 http personnel univ reunion fr lanson typosite fileadmin documents pdf Heuristiques M2 Projet lectur e ModelPYV pdf 18 National Instruments Corporation Tutorial Photovoltaic Cell I V Characterization Theory and LabVIEW Analysis Code December 2009 http zone ni com devzone cda tut p id 7230 19 Verdiseno Inc SolarDesignTool Compare Solar Panels http www solardesigntool com compare solar panels modules html 20 University of Pennsylvania Department of electrical engineering Basics of Power Supplies October 2011 http www ese upenn edu detkin instruments HPpower PS3631A html 21 National Instruments Corporation Fluke Philips flpm28xx Power Supply LabVIEW Plug and Play Instrument Driver http sine ni com apps utf8 niid web display download page p id guid E3B19B3E 920A659CE034080020E74861 22 National Instruments Corporation GPIB USB HS Ni 488 2 3 0 driver for windows http joule ni com nidu cds view p id 2706 lang en 23 lsidro Elvis Pereda Soto Celdas fo
38. ipedia Band Gap Last modified on 7 December 2011 http en wikipedia org wiki Band_gap Wikipedia Shockley Queisser limit Last modified on 28 January 2012 http en wikipedia org wiki Shockley E2 80 93Queisser limit Four Peaks Technology Solar Efficiency Limits 2010 http solarcellcentral com limits page html National Renewable Energy Laboratory NREL Golden CO February 2012 http www nrel gov ncpv Sharp Electronics Corporation NU U208FC Solar Panel Datasheet 2009 http files sharpusa com Downloads Solar Products sol dow NUU208FC pdf Solarex MSX5 MSX10 Solar Panel Datasheet November 1998 http www deltastrumenti it misura Datataker MSX10 pdf Solarex MSX60 MSX64 Solar Panel Datasheet 1998 http www californiasolarcenter org newssh pdfs Solarex MSX64 pdf 10 National Instruments Corporation Tutorial I V Characterization of Photovoltaic Cells Using PXI February 2012 http zone ni com devzone cda tut p id 7231 11 Free Energy Europe FEE 14 12C Solar Panel Datasheet February 2010 http www freeenergyeurope com pdf FEE 14 12C EN pdf 44 12 Fluke Pm2811 pm2812 pm2813 pm2831 pm2832 User s Manual 1997 http igor chudov com manuals Fluke PM2813 User Manual pdf 13 National Instruments Corporation Tutorial Getting Started with NI LabVIEW Student Training June 2010 http Zone ni com devzone cda tut p id 7466 14 Patel Mukund R Wind and solar power systems design analysis and operat
39. ity of Maine EJ RCA ZO RCA RCA n RCA RCA a 1975 1980 1985 1990 NREL EL S si NRELEU O CIS United Solar oein O Photon Energy Lu United Solar SINREL Solar Spectrolab Junction lattice matched Fraunhofer ISE ios metamorphic 299x Boeing metamorphic 454x Spectrolab Boeing Spectrolab Boeing Spectrolab Semiconductor metamorphic metamorphic 179x _ metamorphic 240x Re NREL Kc inverted metamorphic NREL inverted metamorphic i 325 7x Sharp IMM 1 sun NREL inverted 2 metamorphic 1 sun FhG ISE v 1 sun Japan Energy z Spectrolab 4 0 cm2 1 sun NREL UNSW UNSW Culin Ga Sez UNSW 14x Sanyo Georgia Eurosolare N Georgia Tech Tech Univ Sharp itsubishi n Mitsubishi oPower g RE area United Solar st NREL small area Chemical UCLA Sumitomo K Chemical 45 um thi um thin ited Solar film transfer CdTelCIS aSilncSiincSi e LI United Solar NREL Konarka Univ Linz Groningen i N 4 V Peto A rietalok Univ of University Siemens Dresden NREL Toronto Linz ZnO PbS QD PbS QD 2005 2010 IBM N A CTZSSe Konark University Linz 1995 2000 2015 Figure 11 Best Research Cell Efficiencies 6 10 Chapter 3 Modeling of photovoltaic panel 3 1 Electric Model This section formulates the model of a photovoltaic isolated cell To understand the behavior of a solar cell it is useful use an equivalent ele
40. ly 28 Philips Fluke PM2832 Power Supply ccccceeccccecccceccccccccesscceeces 29 Philips Fluke PM2832 Power Supply Detail 29 Algorithm Used to Set the Power Supply eere nn 30 SUE qr n 31 asked et m 31 CONNECTION STENE vene 32 b fod delicia f CER 33 LabVIEW Front Panel of With Hardware vi eee 34 SHARP UN U208FC from Data Sheet 7 ccc cee ccc ee ec cceeccceececeeeecees 37 SHARP UN U208FC for Different Irradiances from Simulator 37 Solarex MSX 10 for STC from Simulator 5 2 9 ENSE E T IOS E us 38 Solarex MSX 10 for different temperatures from datasheet 8 39 Solarex MSX 10 for different temperatures from simulator 39 Solarex MSX 60 for 100W m2 from simulator eese 40 Solarex MSX 60 for STC from simulator eese 40 Example of a Photovoltaic Test System 10 eere 43 List of Tables Table 1 Diode quality factor and band gap voltage 36 Table 2 Experimental Results for SHARP UN U208FC 37 Table 3 Experimental Results for Solarex MSX10 cec e nn 38 Table 4 Experimental Results for Solarex MSX60 csse enne 41 XI Abbreviati
41. n series 36 Want to change cell in parallel Cells in parallel Me d LabVIEW Front Panel of WITH HARDWARE VI 34 5 Eos a i Jano 40 40 60 100 Cutput parameters Max voltage vac 21 908 Max Current Tec 0 9 Max Power 16 4515 Current at Max Power 085242 voltage at Max Power 19 5 Supply current cutoff 0 849695 Supply voltage cutoff 19 36 Supply power cubaFF 16 4502 Fill Factor 951 0 830974 Efficiency 11 4249 The front panel of LabVIEW it is a graphical and intuitive interface that shows the characteristic curve of the panel simulated and his operating point Also shows the power curve with his corresponding point The left column is reserved for the panel parameters where the user will introduce all the characteristic parameters which are easy to find out in the manufacturer s website The parameters of T1 T2 there would almost never be changed because they are the usually defined by the manufacturer and the Voc T min almost never change the functioning of the cell so rarely it s going to be changed At the top left the user could calculate the Isc at temperature 2 which is able by default The variations of the short circuit current due to the temperature of the panel usually are given by the manufacturer with a coefficient alpha C So if this alpha is changed the program automatically calculates the new Isc at T2 At the top right there
42. ntensity values higher This source is used because that is what was available in the laboratory however the procedures to emulate the higher power panels are analogous to those performed In order to test the hardware we are going to change the panel so far used for the analysis of the graphs the msx60 because this one have a short circuit current of 3 8 A but also will prove the MSX60 reducing the value of the irradiation from 1000W m2 to 100W m2 thus the current will fall and the simulation will be within the limits of the source In Chapter 5 experimental results this will be shown The source is connected to a rheostat The rheostat resistance will vary from short circuit to a 100 ohm resistor which simulates an open circuit Because of this you can check if the source mimics the curve created in LabVIEW from Voc to Isc 4 3 Hardware Implementation To control the power source with the voltage and current MEASURES VOLTAGE values given by the curve previously created the algorithm AND CURRENT OF that is used is explained below Essen The method is to find the point of intersection between the curve and the line of resistance It creates a line from the origin to the measured output CREATES current The line is equivalent to the resistor connected to RESISTANCE LINE the source 1 R The intersection between the line and the curve will be the working point the algorithm is used to find this intersection and change
43. o change the input parameters or the resistance the curve will change according to changes and the program looks for the new operating point quite quickly 35 5 3 Test Panels In this chapter are tested some commercial panels to see how reliable is the simulator developed The panels are compared with the I V curves and the characteristics provided by the manufacturer At the end of this section they are some conclusions of the tests done The panels chosen are the following e Sharp Electronics Corporation NU U208FC e Solarex MSX10 e Solarex MSX60 For testing the panels are necessary know the values of the diode quality factor and the band gap voltage of the different materials used in the cells Table 1 Cell Type Diode quality factor n Bandgap Voltage Vg Mono Silicon 1 026 1 11 Poly Si 1 025 1 14 a Si H 1 8 1 65 a Si H tandem 3 3 2 9 a Si H triple 3 09 1 6 Cadmium telluride CdTe 1 5 1 49 Copper Indium Sellenium CIS 155 1 48 Gallium arsenide AsGa 1 3 1 43 Table 1 Diode quality factor and band eap voltage Another thing to keep in mind is that values of voltage and current given by the manufacturer are for the STC conditions so for another temperatures or irradiance is more complicated to compare the simulator however some manufacturers for example Solarex gives a graph of the behavior at different temperatures and the manufacturer Sharp gives a chart of the behavior at different irradiance They are chosen t
44. ons and Symbols Nomenclature Meaning Ip Diodo current branch A lou Rsh current branch A Io Diode saturation current A Roy Parallel resistance 0 V Band gap voltage eV V Thermal voltage V G Irradiance Suns W m K Boltzmann constant 1 38065x10 7 J K n Maximum efficiency 75 T Operating temperature K FF Fill factor 26 Chapter 1 Introduction 1 1 Analysis of Current Situation The increasing cost of conventional energy sources and their environmental impact suggests an increasing penetration of renewable energies in the field of electricity production This is already a reality since about half of all new power plants in the world produce electricity from renewable energy Although this does not seem to be enough because in 2010 the world reached a record high of 10 000 million tons of CO2 which means an increase of 49 over the past two decades according to report in the journal Nature Climate Change Fig 1 Gigawatts 350 312 Others 300 Geothermal power Solar PV m Biomass power Wind power 200 150 100 50 World Developing EU 27 United China Germany Spain India total Countries States Figure 1 Renewable Power Capacities 2010 1 Still 2010 was an extraordinary year for photovoltaic only between 2009 and 2010 the installed capacity grew by 72 1 Photovoltaic again demonstrated its ease and speed of deployment reaching more than 2 100 M
45. ot change if it does the curvature of the knee where the maximum power occurs rn lt x c U Sm im 3 0 Voltage V Figure 20 I V characteristic as a function of diode guality factor Power W QJ B O O N O pa O Voltage V Figure 21 P V characteristic as a function of diode quality factor 18 The Fig 22 and Fig 23 show the effect of the series resistance As the value of the resistor in series increases it degrades the performance of the cell The resistive behavior tends to change the curve of the diode resulting in the above case as a decline in both the power and fill factor regardless of Isc and Voc not change Rs 0 01 0 rn t c Q im im 3 0 Rs 0 02 Q Rs 0 03 0 Voltage V Figure 22 I V characteristic as a function of series resistance Rs 0 01 0 Power W Rs 0 02 Q Rs 0 03 0 10 15 Voltage V Figure 23 P V characteristic as a function of series resistance 19 Photovoltaic solar panels are interconnected in series to form arrays strings which in turn are connected in parallel Solar panels similar electrical characteristics are grouped into strings Each string is composed of N series connected photovoltaic panels The Fig 24 and Fig 25 are providing information on associations in series The voltage resulting from the panel increases proportionally to the number of cells while the current is
46. re is the maximum current Ij zi 3 12 The open circuit voltage will occur when R with O all the photocurrent through the diode and it produces the maximum voltage value In the darkness the characteristic curve of the photovoltaic cell is very similar to the exponential curve of a diode Voc represents the voltage of the cell in the dark Voc In V In 3 13 V P 3 14 When the cell works in the Isc and Voc points the power developed by the panel will be zero The maximum power dissipated by a resistive load connected to the panel is easily calculated by the equation P max Vmax Imax 3 15 13 Fill Factor FF Is another interesting parameter to study the behavior of a solar cell It expresses the ratio between the maximum power point and the product of the open circuit voltage and short circuit current is a way of measuring the quality of the photovoltaic cell FF maxmax 3 16 Voc lsc Maximum efficiency is the ratio enters the maximum power and power of the incidence of light Vmax Tmax n AG 3 17 3 2 Curve analysis The electrical characteristics of the cell are represented through their I V and P V curves First explains the IV curve and the PV curve then how these vary with the change of radiation temperature diode quality factor series resistance and coupling of more cells either connected in series or in parallel Connecting the simulator to a resistive load his proper
47. rge electrons in n type material near the joint area will generate positive ions Conduction Band Bandgap Valence Band Electron Energy Figure 6 Bandgap in semiconductor 3 edited Incident light External Load Figure 7 Photovoltaic cell scheme Both types of ions form an electrical potential barrier and therefore a current that is proportional to the incidence of radiation The cell behavior is very similar to the classic p n junction diode Fig 7 2 1 1 Semiconductor Limits The solar panel efficiency is largely determined by the type of doping material and the band gap of the semiconductor Shockley Queisser limit refers to the theoretical maximum efficiency can be obtained from a solar cell that uses a p n junction Fig 8 30 20 10 Max Efficiency 0 1 2 3 Bandgap eV Figure 8 The Shockley Queisser limit for the efficiency of a solar cell 3 edited The causes of Shockely Queisser limit is indicated in the figure The orange area is the useful power the red area is the energy of below band gap photons the green height is energy lost when hot photo generated electrons and holes relax to the band edges the blue zone is energy lost in the tradeoff between low radioactive recombination versus high operating voltage Fig 9 100 dent gi Light Energy o o inci Percent of N o 0 1 2 Bandgap eV C3 Fieure 9 Breakdown of the causes for the Shockle
48. s After the presentation of the basics of the photovoltaic cell the Chapter 5 and Chapter 6 deal with the theoretical and practical develop of the simulator there is detailed and discussed all the work done through the program LabVIEW and shows the result obtained by the experimentation The structure of the document is shown in figure 4 Finally the chapter 6 contains conclusions and future research areas Chapter 2 Chapter 4 Chapter 3 Chapter 5 FUNDAMENTALS PHOTOVOLTAIC ENERGY PROGRAMMING WORK Chapter 1 Chapter 6 ELECTRIC HARDWARE MODEL IMPLEMENTATION INTRODUCTION CONCLUSIONS CURVE EXPERIMENTAL ANALYSIS RESULTS LABVIEW Figure 4 Master Thesis Structure Chapter 2 Fundamentals of Photovoltaic Energy The photovoltaic effect is the electrical potential developed between two different materials when their common junction is illuminated by photon irradiation In other words photovoltaic solar energy is the use of electromagnetic radiation of the sun shining on a photovoltaic cell produces electricity in a direct way The solar cell is composed of a semiconductor material usually silicon which when crossed by the photons generated in one side an electric current produced by the photovoltaic effect The manufacture of these cells is expensive in both time and money although silicon with which they are made is very abundant in the earth its procedure is laborious and complicated
49. ti junction or Tandem Cells Are solar cells that contain multiple pn junctions Each union is set to a different wavelength reducing a major source of losses and increasing efficiency Currently the best examples of laboratory silicon solar cells have an efficiency of traditional about 25 while examples of laboratory multi junction cells have demonstrated superior performance to 42 23 Given the diode quality factor and the band gap voltage of the semiconductor material the simulator will have no problem to emulate all types of cells in the market Fig 11 Best Research Cell Efficiencies Multijunction Cells 2 terminal monolithic Y Three junction concentrator v Three junction non concentrator A Two junction concentrator Single Junction GaAs A Single crystal A Concentrator V Thin film crystal Crystalline Si Cells m Single crystal D Multicrystalline Thick Si film e Silicon Heterostructures HIT Thin Film Technologies e Cu In Ga Se o CdTe O Amorphous Si H stabilized 4 Nano micro poly Si O Multijunction polycrystalline Emerging PV O Dye sensitized cells Organic cells various types 4 Organic tandem cells Inorganic cells Q Quantum dot cells Varian Varian 216x Stanford IBM T J Watson Georgia Tech University So Florida Boeing No Carolina Mobil State Univ Solar Solarex da Boeing p Je ig Matsushita Boeing e Boeing RCA Solarex LJ E A Univers
50. tovoltaicas en generaci n distribuida Pontifical Catholic University of Chile 2005 Pages 24 43 http web ing puc cl power paperspdf pereda pdf 45 Annexes 46 Panel parameters Tab Control Tab Control Output parameters Environmental Conditions Calculate Tec at Tz with coefficient Alpha e 190C7 Zi j j j j j im N oc To A Voltage FDEL DELS voc at T1 LE DELS Solar cal DEL gt n diode Factor DELS TI ESTO Kk net H vg EE a i 4 om ost Power POEL Max Power OBL Fill Factor 1 OBL Current af Max Power lis OBL voltage at Max Power XY Graph Area m 2 BEL OBL Efficiency HE Max Current Tec HOEL Max voltage vac o P TFH Output Current FDEL Annex 1 LabVIEW Block Diagram of Without Hardware vi 47 Jo Panel parameters 2 Tab Control 2 Output parameters Environmental Conditions Calculate Icc at T2 with coefficient Alpha 95 9C vy L L 50000 NW me B pw AY o l FS PSBL Fill Factor 1 PBL Voltage at Max ower voc T min Dett Efficiency OBL Max Current Icc voltage Voc voltage Area m 2 Det Irradiation G Suns 1 Sun 1000W m2 Voc at T1 CET Solar Cells Output Current BL om Det b Temperature pent n
51. ture Ia solar Va G T voltaje vector Ia Va current and voltaje vector sG number of Suns 1 sun 1000W m 2 T temperatura in Celsius kK 1 386 23 amp Boltzman s constant q 1 60e 19 electron charge n 1 2 diode quality factor Vg 1 12 Band voltage Ns 36 Number of series cell TI T OZ SE Vocl 21 06 Ns Open circuit voltage per cell at Tl Icole3 90 Short circuit current per cell at TI 2 30 795 Voc2 17 05 Ns Open circuit voltage per cell at T2 100223 982 Short circuit current per cell at T2 TaK 273 TaC To Kelvin K 9 IGC2 1001 T2 Tl Lilertool sSu s LLIeILISKOTUCTAR TL S T01 1Icc1 exp q Voc1 n k T1 1 X Diode current LO FOT TER TL NSA G VG7 a k 0 lof Teak 1 TN KV LOL G7 in RT ENG VOGEL AR TIN dvdI Voc 1 15 Ns 2 Manufacter information Rs dVdI Voc 1 Xv series resistance per cell Vt Ta n k TaK q vt AkT q Vc Va NS Ta zeros size Vc 23 SNewton s method For jelzo LlacIla l l4 I0 18Xp VOTIa PRES Ve TEL SNL I0 exp VofTa FRS VE Ta 1 4 RS 7Vt Ta End V 0 0 1 24 Voltage sampling la solar V l 295 5 plot risy rt axis 0 250 0 5 xlabel Voltage ylabel Current hold on For the understanding of this section is recommended the view of the annex 1 Through the software created in LabVIEW user can also enter panel parameters as variables through a series of controls in addition to irradiation and temperature of operat
52. ty meets Ohm s law I V 1 R in this way the power generated by the panel depends only on the value of the resistance Fig 14 4 A Theoretical Isc power Pt Imax 3 2 5 2 1 5 1 R 1 0 5 o 0 5 10 is Vmax 20 Voc 25 Figure 14 A Typical current voltage I V curve for a solar cell If R is small the panel will work in the point A to the left of the maximum power point where you have a behavior similar to a current source If R is close to zero the panel will work on short circuit Isc point where no power is generated If R is large the panel will work in the point B to the right of maximum power point where you have a behavior similar to a voltage source If R approaches infinity work on open circuit Voc point where not produce any power There will be an optimal R where the panel develops maximum power which is calculated by the fill factor which can be seen graphically as the ratio of green area Pmax Imax Vmax for the white area Pt Voc e ISC 14 The PV curve is the product of voltage and output current The PV systems are designed to work near the knee slightly to the left side Fig 15 Most manufacturers of inverters for photovoltaic plants make a wide range between the maximum power point of maximum and minimum Vppmax Vppmin where the inverter acts properly and has no problem to find the maximum power point in where the panel is working In addition will also point Vomax Vomin and where the inverter can
53. with a diode and only taken into account the series resistance Rs Rsh value usually has a very high value more than 200 Ohms and our hypothesis we despise since the panel efficiency is insensitive to changes in Rsh Fig 13 In an ideal cell Rs O there will be no voltage drop before the load and Rsh no other roads where you can lose part of the current IDEAL MODEL RL Figure 13 One diode equivalent circuit of a PV cell g V Rs I I I Ig e nKT 1 3 4 The saturation current of the diode and the photocurrent depend with the temperature The following equations consider the radiation and temperature as parameters that affect the behavior of the panel 17 I I T4 Ko T T4 3 5 12 G I T4 E Isc T1nom y 3 6 Isc T2 Igc T1 Ko TT 3 7 3 cavar A T Xn L Io Io T1 e nK 3 8 Isc T1 Ig T4 Vo 3 9 e nkT4 1 Equation 3 10 represents the series resistance inside each cell in the connection between cells and the internal losses The series resistance will vary with the temperature since equation 3 11 depends on the saturation current of the diode dV 1 R 0 3 10 q qV oc T1 Xy IQ T4 nKT nKT1 3 11 The model takes two fixed values of temperature to calculate the output parameters of the panel at the operating temperature The short circuit current will occur when R 0 in totally lighting conditions with V 0 the
54. y Queisser limit 4 edited 2 1 2 Irradiation Limits The amount of current generated in the PV is affected by two variables the intensity of incident light and the wavelength of the incident rays Each semiconductor material shall have a limited absorption of radiation Below this no electrons make the photovoltaic effect The energy of a photon is determined by the wavelength but not by the intensity of light against shorter have more energy Increasing light intensity increases proportionally photoelectron emission rate in the photovoltaic material Solar cells are usually coated with an anti reflective material to capture the maximum amount of radiation possible Below is a graph where we can see the range that can take advantage of a silicon photovoltaic cell Fig 10 UV visible infrared 1 6 O solar spectrum AM 1 5 G 1000 W m 1 2 converted by crystalline silicon cell 1100 nm 1 1 eV band gap of silicon energy W m nm 400 800 1200 1600 2400 2400 wavelength nm Figure 10 Solar radiation Spectrum 5 edited Photons with wavelengths too high will pass through the panel in the form of heat Photons with a wavelength less than 1 100nm have more energy than the required to separate the electron the excess energy is converted to heat losses 2 1 3 Temperature Limits As the temperature rises above the absolute zero the number of electrons that jump to the conduction b
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