simulink based generalized model of pv module
DESCRIPTION
Thesis PaperTRANSCRIPT
Simulink Based Generalized Model of PV Cell / Module
Submitted by
Sheikh Mahedi HasanMd. Atiqur RahmanMd. Monimul Islam
Aneek Islam
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
Bachelor of Science
in
ELECTRICAL AND ELECTRONIC ENGINEERINGUNITED INTERNATIONAL UNIVERSITY
July 2013
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Declaration
This is to certify that the Thesis/Project entitled “Simulink based generalized Model of PV cell/
module” has been completed satisfactorily.
-----------------------------------------------------Dr. Md. Iqbal Bahar ChowdhuryAssistant Professor and SupervisorDepartment of Electrical and Electronic Engineering
-----------------------------------------------------Sheikh Mahedi HasanStudent ID: 021-092-013
-----------------------------------------------------Md.Atiqur RahmanStudent ID: 021-092-063
-----------------------------------------------------Md.Monimul IslamStudent ID: 021-092-067
-----------------------------------------------------Aneek IslamStudent ID: 021-092-054
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Abstract
This work proposes a MATLAB/Simulink Model of a photovoltaic (PV) system. The main
contribution of this work is the utilization of a two-diode model of a PV solar cell using
Similink. This model considers the series and shunt resistance and simulates the effects of
various parameters such as temperature, irradiance and ideality factor. To reduce simulation
time, the input parameters are reduced to few and based on the available information from the
PV module datasheet. The values of series and shunt resistance are estimated by an efficient
iteration method. The developed model allows the user to predict PV a cell’s current-voltage and
power-voltage characteristics curve by varying sunlight, cell temperature, ideality Factor and
series resistance value. The characteristics curves obtained by the simulation of
Matlab/Simulink model is matched with the data provided by manufactures by changing the
value of mentioned internal parameters.
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To our Parents
“If we did all the things we arecapable of doing, we wouldastound ourselves.”
-Thomas A. Edison
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Acknowledgements
First and foremost we would like to thank our creator Almighty Allah who is the most Gracious
and most Merciful. By the grace of Almighty Allah we are successfully complete the Simulink
based generalized model of PV cell / model. We would like to express our deepest gratitude to
our advisor, Dr. Md. Iqbal Bahar Chowdhury, for his excellent guidance, caring, patience,
assistance and providing us with an excellent atmosphere for doing this thesis. We further extend
thanks to our parents because without their mental and physical supports we are not able to reach
in this position.
Information of Students:
Sheikh Mahedi Hasan, Cell Phone:+880171-1456616,E-mail: [email protected]
Md.Atiqur Rahman, Cell Phone:+880192-1427929, E-mail: [email protected]
Md.Monimul Islam, Cell Phone:+880172-7229280 ,E-mail: [email protected]
Aneek Islam, Cell Phone:+880191-2273106 ,E-mail: [email protected]
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List of Tables
2.1 Country wise manufacturer company list ………………………………………………...…18
5.1 Solarex MSX 60 Specifications data …………………………………………..……………58
5.2 Temperature Variation for Single diode & two diode ………………..……………………..68
5.3 Irradiance Variation ……………………………………………………………..…….…….75
5.4 Ideality Factor Variation……………………………………………………………….…….81
5.5 Rs variation ……………………………………………………….…………………………87
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List of Figure
2.1 Practical Photovoltaic cell ………………………………………………………………..…072.2 platinum electrode solar cell ……………………………………………………………...…082.3 Photovoltaic effect in selenium ………………………………………………….……..……092.4 "Thin-film" photovoltaic cell………………………………………………………...………092.5 copper-cuprous oxide rectifiers and photovoltaic cell……………….………………………102.6 Thallous-sulphide PV cell……………………………………………………………………11
3.1 solar cell………………………………………...……………………………………………203.2 Photovoltaic Installation…………………………………………..…………………………343.3 p-n junction by doping process………………………………………………………………353.4 Electric current flow…………………………………………………………………………363.5 Phenomenon of doping process………………………………………………………...……373.6(a) Flat plate system…………………………………………………………………….…….383.6(b) Concentrator system…………………………………………………………………....…393.7 Radiation of solar energy………………………………………………………………….…393.8 Sun Power Corp. Model SPR-215-BLK modules ……………………………….…….……40
4.1 Equivalent Model of Single-Diode Photovoltaic cell……………..…………………………424.2 Equivalent Model of Single-Diode Photovoltaic cell…………………………………..……444.3 SIMULINK example block diagram………………………………………………………...494.4 SIMULINK output result…………………………………………………………………….504.5 Block diagram for calculate light generated current…………………………………………504.6 Block diagram for calculate light generated current…………………………………………514.7 Block diagram for calculate Reverse saturation current………………………..……………514.8 Block diagram for calculate current………………………………………………………….524.9 Block diagram for Shunt Current………………………………………………….…………534.10 Current block diagram for single diode with Rs………………………...………….………534.11 Current block diagram for two diode with Rs…………………………………..….………544.12 Subsystem block diagram for single diode with Rs……………………………….….….…554.13 Subsystem block diagram for two diode with Rs……………………….…………….……56
5.1 I-V & P-V curve for single diode……………………………………………………………595.2 I-V & P-V curve for single diode with Rs……………………………………………...……605.3 I-V & P-V curve for two diode…………………………………………………………....…615.4 I-V & P-V curve for two diode with Rs……………………………………………………..625.5 single diode I-V characteristic curve……………………………………………………...…645.6 Two diode I-V characteristic curve……………………………………………………….…655.7 Single diode P-V characteristic curve………………………………………….……………665.8 Two diode P-V characteristic curve………………………………………….………………675.9 Difference between two diode and single diode compare with ideal diode for power……....68
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5.10 Difference between two diode and single diode compare with ideal diode for voltage……695.11 Difference between two diode and single diode compare with ideal diode for current……695.12 Single diode I-V characteristic curve……………………………………………………….715.13 Two diode I-V characteristic curve…………………………………………………………725.14 Single diode P-V characteristic curve………………………………………...…………….735.15 Two diode P-V characteristic curve…………………………………………………….…..745.16 Difference between two diode and single diode compare with ideal diode for power……..755.17 Difference between two diode and single diode compare with ideal diode for voltage……765.18 Difference between two diode and single diode compare with ideal diode for current……765.19 Single diode I-V characteristic curve varying ideality factor………………………………775.20 Two diode I-V characteristic curve varying ideality factor…………………………….…..785.21 Single diode P-V characteristic curve varying ideality factor………………………….…..795.22 Single diode P-V characteristic curve varying ideality factor…………………………...…805.23 Difference between two diode and single diode compare with ideal diode for power…..…815.24 Difference between two diode and single diode compare with ideal diode for voltage……825.25 Difference between two diode and single diode compare with ideal diode for current…....825.26 Two diode I-V characteristic curve (Effect of Rs)…………………………………….……835.27 Single diode P-V characteristic curve (Effect of Rs)……………………………….………845.28 Two diode P-V characteristic curve (Effect of Rs)……………………………………..…..865.29 Difference between two diode and single diode compare with ideal diode for voltage……885.30 Difference between two diode and single diode compare with ideal diode for current…....885.31 Single diode I-V characteristic curve……………………………………………………….895.32 Single diode P-V characteristic curve…………………………………………………...….905.33 Two diode I-V characteristic curve at different temperature…………………………...…..915.34 Two diode P-V characteristic curve at different temperature………………………..……..92
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Contents
DeclarationAbstractAcknowledgmentsContentsList of TablesList of Figures
Chapter 1 Introduction1.1 Objective1.2 Literature Review1.3 Scope of the work1.4 Organization
Chapter 2 Overview2.1 Photovoltaic cell (PV Cell) 2.2 History of Photovoltaic (PV) Solar Energy2.3 Advantage of Solar PV cell2.4 Disadvantages of Solar PV cell 2.5 Reasons to Use Solar Electricity.2.6 List of photovoltaic power stations2.7 Leading Companies over the world
Chapter 3 Theory3.1 Solar Cell3.2 Solar cells internal basic operation3.3 Basic attributes3.4 Working principle3.5 Diffuse and Direct Solar Radiation3.6 Measurement3.7 Solar Energy Resources3.8 Different Materials of solar cell3.9 Important and Efficient of Solar Energies3.10 Photovoltaic solar cells
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3.11 Photovoltaic cells internal basic operation and doping process3.12 How PV cells are made3.13 Types of Solar PV Cell3.14 Solar Radiation Energy3.15 Silicon Solar PV Product
Chapter 4 Modeling4.1 Basic equations4.2 Basic parameters4.3 Matlab/Simulink4.4 Modeling for single diode ideal model 4.5 Modeling for single diode with Rs 4.6 Modeling for two diode with Rs 4.7 Modeling of Subsystem for single diode with Rs4.8 Modeling of Subsystem for two diode with Rs
Chapter 5 Result and Discussion5.1 Effect of Cell Temperature5.2 Effect of Irradiance
` 5.3 Effect of Ideality Factor5.4 Effect of Rs
Chapter 6 Conclusion6.1 Outcome of the work6.2 Limitation and Suggestion6.3 Future work
References
Chapter1
Introduction
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1.1 Objective
Large and small scale PV power systems have been commercialized in many countries due to
their potential long term benefits, generous fed-in tariff schemes and other attractive initiatives
provided by various governments to promote sustainable green energy. In PV power generation,
due to the high cost of modules, optimal utilization of the available solar energy has to be
ensured. This mandates an accurate and reliable simulation of designed PV systems prior to
installation. The most important component that affects the accuracy of a simulation is the PV
cell modeling, which primarily involves the estimation of the non-linear I-V and P-V
characteristics curves. Though impractical, the simplest model is the single diode model i.e. a
current source in parallel to a diode. It only requires three parameters, namely the short-circuit
current (Isc), the open circuit voltage (Voc) and the diode ideality factor (A). This model is
improved by the inclusion of one series resistance, Rs. Despite its simplicity, this model exhibits
serious deficiencies when subjected to temperature variations. An extension of the model which
includes an additional shunt resistance Rp. Although a significant improvement is achieved, this
model demands significant computational effort. Furthermore its accuracy deteriorates at low
irradiance levels, especially near Voc. Here we consider all the parameters for single diode and
two diode model.
1.2 Literature Review
The modeling and simulation of photovoltaic (PV) have made a great transition and form an
important part of power generation in this era. The modeling of PV module generally involves
the approximation of the non-linear I-V and P-V characteristic curve.
If we review the literature of photovoltaic cell, it start its journey at the beginning 1977 with
“Enhancement of the power output of photogalvanic cell."” by P.V. Kamat, M.D. Karkhanavala,
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and P.N. Moorthy. After 1977 several researcher are researched for its development and they try
to increase its performance as well as reduce its cost.
Many researchers used circuit based approach to characterize the PV module of which the
simplest model is the current source in parallel to a diode (Da Silva R. M. et al., 2010; Altas H. I.
et al., 2007; Nena S. et al., 2010 and Gradella Marcelo et al., 2007). In a PV system, peak power
point changes continuously due to environmental variations, sometime substantial drop in power
especially during partial shading conditions. Several computational methods are proposed by
several researchers (Ishaque K, Zainal Salam, 2011, Dell R. V. et al., 2010, Da Silva R. M. et al.,
2010; Jung J. H. and Ahmed S., 2010 and Walker G., 2001; Dell Aquila R. V., 2010; Ebrahim
M., 2007). Simple circuit-based photovoltaic model has proposed in (Da Silva R. M. et al., 2010;
Jung J. H. and Ahmed S., 2010; Walker G., 2001; Yushaizad Yusof, et al., 2004 and Jung Jee-
Hoon, Ahmed S., 2010). Indirect methods have also been proposed by some researchers where
the, I-V curve is adjusted through artificial intelligence techniques (Veerachary M., 2005;
Chowdhury S., Chowdhury S.P., 2008; Zegaoui A., 2011; Ramaprabha R. and Mathur B. L.,
2011). Although some of these methods are impractical, complicated and require high
computational effort, and some of these modeling was limited to simulation of photovoltaic
module characteristics. Thus, because of the numerous challenges, an accurate and
comprehensive design of PV system using the detailed circuit model in MATLAB Simulink
model was proposed.
In 29 Apr 2013 (Updated 06 May 2013) Shivananda Pukhrem analysis, “A circuit based
simulation model for a PV cell for estimating the IV and PV characteristic curves”.
It is now still one of the most talkative matters that’s why several researchers are researched behind
this hard and soul. Especially several organizations are financially support behind this.
Now a day’s several researchers’s researching the following fields as-
Simulation between two photovoltaic cell models
Modeling of Photovoltaic Panel and Examining Effects of Temperature module
Extraction of the Internal Parameters of Solar photovoltaic module
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Photovoltaic Array Simulation for Matlab-Simulink GUI Environment
Modeling and Simulation of Photovoltaic using MATLAB/Simulink module
Mathematical Modeling and Simulation of Photovoltaic Cell using Matlab-Simulink
Environment
MATLAB/SIMELECTRONICS Based Study of Solar Cells module
MATLAB/Simulink Model of Solar PV Module and MPPT Algorithm
Matlab/Simulink-Based Photovoltaic Array Module Employing Sim Power Systems
Toolbox
Development and Simulation of Solar Photovoltaic model using Matlab/Simulink and its
parameter extraction
Development of Generalized Photovoltaic Model Using MATLAB/SIMULINK
1.3 Scope
Now a day’s it is one of the most challenging issue to improve PV cells performance. Such case
we consider PV cell as challenge for increasing its performance as well as development.
Consider the single diode and two diode model’s parameters (i.e. Rs, sun light, temperature,
Ideality factor), we observe the I-V, P-V characteristics curves.
1.4 Organization
To organize the whole papers we have to maintain a sequence.
In chapter 1, we try to include the introduction in to an organized way. On there we try to
introduce our thesis objective, literature review and scope of the work.
In chapter 2, we try to include the overview of PV cells. Its background history,
advantage, disadvantages. We also include photovoltaic’s power stations and leading
company at present world.
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In chapter 3, we try to include the basic theory of solar cell, basic principle, working
principle, solar energy resources. Then we try to include about photovoltaic solar cell, its
basic principle as well as working principle and types.
In chapter 4, we include the modeling. In this chapter, we discuss about basic equations,
basic parameters, a short description of Matlab and Simulink, model with Rs and Rp and
without Rs and Rp.
In chapter 5, we discuss about results and discussions. Such case we consider the
variation of cell temperature, irradiance and the effect of Rs .
In chapter 6, we try to include the conclusion of the work, its limitation and future
development.
Finally, we include some reference that helps us a lot to collect information for this thesis
purpose.
Chapter 2
Overview
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2.1 Photovoltaic cell (PV Cell)
Photovoltaic’s (PV) is a method of generating electrical power by converting solar
radiation into direct current electricity by using semiconductors that exhibit the photovoltaic
effect. Photovoltaic power generation employs solar panels composed of a number of solar
cells containing a photovoltaic material. Materials presently used for photovoltaic’s
include mono-crystalline silicon, polycrystalline silicon,amorphous silicon, cadmium telluride,
and copper indium gallium selenide/sulfide. Due to the increased demand for renewable energy
sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in
recent years.
Fig 2.1: Practical Photovoltaic cell
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2.2 History of Photovoltaic (PV) Solar Energy
Historical background:
In 1839, Edmond Becquerel appears to have been the first to demonstrate the photovoltaic effect.
Working in his father's laboratory as a nineteen year old; he generated electricity by illuminating
an electrode with different types of light, including sunlight (see the figure below). Best results
were obtained with blue or ultraviolet light and when electrodes were coated with light sensitive
material such as AgCl or AgBr. Although he usually used platinum electrodes, he also observed
some response with silver electrodes. He subsequently found a use for the photovoltaic effect by
developing an "actinograph" which was used to record the temperature of heated bodies by
measuring the emitted light intensity.
Fig 2.2: platinum electrode solar cell
In 1876, the next significant photovoltaic development arose from the interest in the
photoconductive effect in selenium. While investigating this effect, William Grylls Adams and
his student, Richard Evans Day, noted an anomaly they thought could be explained by the
generation of internal voltages. They investigated this anomaly more carefully using samples as
shown below. Heated platinum contacts were pushed into opposite ends of small cylinders of
vitreous selenium. The objective of one experiment conducted by Adams and Day upon such
specimens was to see 'whether it would be possible to start a current in the selenium merely by
the action of light'.
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Fig 2.3: Photovoltaic effect in selenium
The result was positive! This was the first demonstration of the photovoltaic effect in an all
solid-state system. Adams and Day attributed the photo generated currents to light induced
crystallization of the outer layers of the selenium bar. Several decades were to pass before the
development of physics allowed more insight into this process.
In 1883, the next significant step forward came seven years later with the work of Fritts. By
compressing molten selenium between plates made from two different metals, Fritts was able to
prepare thin Se films which adhered to one of the two plates, but not to the other. By pressing a
gold leaf to the exposed selenium surface, he thereby prepared the first "thin-film" photovoltaic
devices. These first thin-film devices were as large as 30 cm2 in area.
Fig 2.4: "Thin-film" photovoltaic cell
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He was also the first to recognize the enormous potential of photovoltaic devices. He saw that
the devices could be fabricated at very low cost and noted that ‘the current, if not wanted
immediately, can either be “stored” where produced, in storage batteries … or transmitted … to a
distance, and there used, or stored’. It was, however, to be nearly fifty years before there was
another significant burst of activity in this area.
In 1905, Albert Einstein published the first theoretical work describing the photovoltaic effect
titled “Concerning an Heuristic Point of View Toward the Emission and Transformation of
Light.” In the paper, he showed that light possesses an attribute that earlier scientists had not
recognized. Light, Einstein discovered, contains packets of energy, which he called light quanta.
Einstein’s bold and novel description of light, combined with the [1898] discovery of the
electron, gave scientists in the second decade of the twentieth century a better understanding of
photo electricity. They saw that the more powerful photons carry enough energy to knock poorly
linked electrons from their atomic orbits in materials like selenium. When wires are attached, the
liberated electrons flow through them as electricity. By the 1920s, scientists referred to the
phenomenon as the “photovoltaic effect.”
In 1927, Grondahl describes the development of both copper-cuprous oxide rectifiers and
photovoltaic cells.The figure below shows the very simple structure used by the earlier cells
based on the copper-cuprous oxide junction. A coil of Pb wire is used to give a grid contact to
the illuminated surface of the cell. This approach was subsequently refined by sputtering the
metal on the outer surface and removing a part of it so as ‘to form a grid of any desired fineness’.
These developments seem to have stimulated a great deal of activity in this
area. Grondahl documents 38 publications dealing with copper-cuprous oxide photovoltaic cells
over the period 1930-32.
Fig 2.5: copper-cuprous oxide rectifiers and photovoltaic cell
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This activity also seems to have reawakened interest in selenium as a photovoltaic material. In
particular, Bergmann reported improved selenium devices in 1931. These proved superior to the
copper-based devices and became the commercially dominant product. In 1939, a thallous-
sulphide cell of similar performance was also reported by Nix. The structure of this device and of
the most efficient selenium and copper-cuprous oxide devices took the form shown in the figure
below.
Fig 2.6: Thallous-sulphide PV cell
In 1953, Bell Laboratories (now AT&T labs) scientists Gerald Pearson, Dary Chapin and Calvin
Fuller developed the first silicon solar cell capable of generating a measurable electric current.
The New York Times reported the discovery as “the beginning of a new era, leading eventually
to the realization of harnessing the almost limitless energy of the sun for the uses of civilization.”
In 1958 while early efforts to commercialize the silicon solar cell faltered, the US Army and Air
Force saw the device as the ideal power source for a top-secret project – earth-orbiting satellites.
But when the Navy was awarded the task of launching America’s first satellite, it rejected solar
cells as an untried technology and decided to use chemical batteries as the power source for its
Vanguard satellite. The late Dr. Hans Ziegler, probably the world’s foremost expert in satellite
instrumentation in the late 1950s, strongly differed with the Navy. He argued that conventional
batteries would run out of power in days, silencing millions of dollar worth of electronic
equipment. In contrast, he argued, solar cells could power a satellite for years. Through an
unrelenting crusade led by Dr. Ziegler to get the Navy to change its mind, the Navy finally
relented and, as a compromise, put a dual power system of chemical batteries and silicon solar
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cells on the Vanguard. Just as Ziegler predicted, the batteries failed after a week or so, but the
silicon solar cells kept the Vanguard satellite communicating with Earth for years.
In 1970’s while the use of solar cells in space flourished during the 1960s and early 1970s, down
on Earth electricity generated from the sun seemed very distant. Cost was never a factor for
space cells. Manufacturers worried more about size, efficiency and durability: the cost of the
launch and the continuing operation of equipment once in space far outweighed the cost of
power in space applications. But on Earth, the primary criterion was, and still is, cost per
kilowatt hour.
Solar-cell technology proved too expensive for terrestrial use until the early 1970s when Dr.
Elliot Berman, with financial help from Exxon Corporation, designed a significantly less costly
solar cell by using a poorer grade of silicon and packaging the cells with cheaper materials.
Bringing the price down from $100 a watt to $20 per watt, this approach yielded solar cells that
could compete in situations where people needed electricity distant from power lines. Off-shore
oil rigs, for example, required warning lights and horns to prevent ships from running into them
but had no power other than toxic, cumbersome, short-lived batteries. Compared to their
installation, maintenance and replacement, solar modules proved a bargain. Many gas and oil
fields on land but far away from power lines needed small amounts of electricity to combat
corrosion in well heads and piping. Once again, electricity from the sun saved the day. Major
purchases of solar modules by the gas and oil industry gave the fledgling terrestrial solar cell
industry the needed capital to persevere.
In Nov. 4, 1978 Jimmy Carter signs Solar Photovoltaic Energy Research, Development, and
Demonstration Act. Due to dedicated research worldwide, the efficiency of photovoltaic’s has
continued to increase while production costs have dropped substantially over the years;
especially significant were cost reductions seen in the 2005-2009 timeframe. Currently at about
$5.50 a watt for the entire solution, installed, on a residential scale, PV solar is becoming cost
competitive with traditional energy sources, and will become even more so as the costs of coal,
gas and oil continue to increase. – Jim Bartlett, Co-Founder & CEO, Arise Energy Solutions,
LLC.
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2.3 Advantage of solar PV Cell
PV panels provide clean – green energy. During electricity generation with PV panels
there is no harmful greenhouse gas emissions thus solar PV is environmentally friendly.
Solar energy is energy supplied by nature – it is thus free and abundant!
Solar energy can be made available almost anywhere there is sunlight
Solar energy is especially appropriate for smart energy networks with distributed power
generation – DPG is indeed the next generation power network structure!
Solar Panels cost is currently on a fast reducing track and is expected to continue
reducing for the next years – consequently solar PV panels has indeed a highly promising
future both for economical viability and environmental sustainability.
Photovoltaic panels, through photoelectric phenomenon, produce electricity in a direct
electricity generation way.
Operating and maintenance costs for PV panels are considered to be low, almost
negligible, compared to costs of other renewable energy systems.
PV panels have no mechanically moving parts, except in cases of –sun-tracking
mechanical bases; consequently they have far less breakages or require less maintenance
than other renewable energy systems (e.g. wind turbines).
PV panels are totally silent, producing no noise at all; consequently, they are a perfect
solution for urban areas and for residential applications (see solar panels for homes).
Because solar energy coincides with energy needs for cooling PV panels can provide an
effective solution to energy demand peaks – especially in hot summer months where
energy demand is high.
Though solar energy panels’ prices have seen a drastic reduction in the past years, and are still
falling, nonetheless, solar photovoltaic panels are one of major renewable energy systems that
are promoted through government subsidy funding (FITs, tax credits etc.); thus financial
incentive for PV panels make solar energy panels an attractive investment alternative.
Residential solar panels are easy to install on rooftops or on the ground without any interference
to residential lifestyle.
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2.4 Disadvantages of Solar PV Cell
As in all renewable energy sources, solar energy has intermittency issues; not shining at
night but also during daytime there may be cloudy or rainy weather.
Consequently, intermittency and unpredictability of solar energy makes solar energy
panels less reliable a solution.
Solar energy panels require additional equipment (solar inverters) to convert direct
electricity (DC) to alternating electricity (AC) in order to be used on the power network.
For a continuous supply of electric power, especially for on-grid connections,
Photovoltaic panels require not only Inverters but also storage batteries; thus increasing
the investment cost for PV panels considerably.
In case of land-mounted PV panel installations, they require relatively large areas for
deployment; usually the land space is committed for this purpose for a period of 15-20
years – or even longer.
Solar panels efficiency levels are relatively low (between 14%-25%) compared to the
efficiency levels of other renewable energy systems.
Though PV panels have no considerable maintenance or operating costs, they are fragile and can
be damaged relatively easily; additional insurance costs are therefore of ultimate importance to
safeguard a PV investment.
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2.5 Reasons to Use Solar Electricity:
Motive of Solar Electricity
The use of solar cells has been very effective in providing electric power to remote, inaccessible
and isolated places. The important uses of solar cells are given below:
Solar Heating is Affordable Green Power
Solar energy is clean, renewable, and good for the environment. A portion of Vermont's
electricity comes from nuclear and fossil fuel-burning power plants, which produce emissions
including long-lived radioactive wastes, greenhouse gases and other air pollutants, including
those responsible for acid rain. By using renewable solar energy to meet a portion of your
household's electric needs, you can significantly reduce your household's contribution to the
release of these pollutants. The following chart illustrates an example of greenhouse gas
emissions for a family of four's electricity consumption, and the emission reductions created by a
PV system that meets 25% of their household electric needs.
Emergency Power
Solar electric systems can provide your household with emergency back-up electricity in the case
of storm caused or other utility outages. At these times solar electric power systems can work
along with a conventional generator or alone. They can also be designed to provide power to
critical loads over extended periods of cloudy weather.
Remote Power
If we plan to build away from established utility service, we should consider the cost of installing
a utility line needed to provide the utility's energy. Often, the cost of extending conventional
power to our residence is more expensive than the solar option.
Solar electric systems are also often a good choice for providing electricity for use in areas that
don't have convenient power sources nearby. Common uses can include boats, electric fence
chargers, outdoor lighting, and remote water pumping.
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Educational Power
By investing in a renewable energy system we provide a hands-on demonstration of clean power.
We can teach our friends, neighbors, and family about how energy systems work, and about how
energy choices impact our environment.
Solar is widely thought to be the energy choice for the future. As we enter a new century and
millennium modern societies may be ready to reduce the amount of effort spent on searching for,
retrieving, processing and transporting non-renewable fossil fuels. At the same time, we can
increase efforts devoted to the sustainable harvesting of local solar energy. After all, long ago
there was a global transition away from hunting and gathering for food (similar to looking for
fossil fuels) towards agriculture (similar to harvesting of renewable energy). We can apply the
same principals to our energy future today.
Independent Power
Renewable energy systems provide our home or business with increased independence. They
also reduce Vermont's and the United States energy imports. Reducing dependence on traditional
fuel sources provides long-term protection from growing energy costs and uncertain supplies. By
relying on local resources renewable energy systems you contribute to Vermont's traditions of
independence and wise resource use
The solar cells have gained too much importance in the last few decades because solar cells are
being used increasingly for providing electricity to artificial satellites and space-probes; for
providing electricity to remote areas and for operating modern instruments like electronic
watches and calculators. The greatest advantage of solar cells is that they make use of
"everlasting solar energy" and their use does not produce any environmental pollution.
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2.6 List of photovoltaic power stations
Many solar photovoltaic power stations have been built, mainly in Europe. As of July 2012, the
largest photovoltaic (PV) power plants in the world are the Agua Caliente Solar Project (USA,
247 MW), Charanka Solar Park (India, 214 MW), Golmud Solar Park (China, 200 MW), Perovo
Solar Park (Ukraine 100 MW), Sarnia Photovoltaic Power Plant (Canada, 97 MW),
Brandenburg-Briest Solarpark (Germany 91 MW), Solarpark Finow Tower (Germany 84.7
MW), Montalto di Castro Photovoltaic Power Station (Italy, 84.2 MW), Eggebek Solar Park
(Germany 83.6 MW), Senftenberg Solarpark (Germany 82 MW), Finsterwalde Solar Park
(Germany, 80.7 MW), Okhotnykovo Solar Park (Ukraine, 80 MW), Lopburi Solar Farm
(Thailand 73.16 MW), Rovigo Photovoltaic Power Plant (Italy, 72 MW), and the Lieberose
Photovoltaic Park (Germany, 71.8 MW).
There are also many large plants under construction. The Desert Sunlight Solar Farm under
construction in Riverside County, California and Topaz Solar Farm being built in San Luis
Obispo County, California are both 550 MW solar parks that will use thin-film solar photovoltaic
modules made by First Solar. The Blythe Solar Power Project is a 500 MW photovoltaic station
under construction in Riverside County, California. The California Valley Solar Ranch (CVSR)
is a 250 megawatt (MW) solar photovoltaic power plant, which is being built by SunPower in the
Carrizo Plain, northeast of California Valley. The 230 MW Antelope Valley Solar Ranch is a
First Solar photovoltaic project which is under construction in the Antelope Valley area of the
Western Mojave Desert, and due to be completed in 2013. The Mesquite Solar project is a
photovoltaic solar power plant being built in Arlington, Maricopa County, Arizona, owned by
Sempra Generation. Phase 1 will have a nameplate capacity of 150 megawatts.
Many of these plants are integrated with agriculture and some use innovative tracking systems
that follow the sun's daily path across the sky to generate more electricity than conventional
fixed-mounted systems. There are no fuel costs or emissions during operation of the power
stations.
18
2.7 Leading Companies over the world
Now a day’s several organizations are working for manufacture PV cells in the world. If we
consider the country wise manufacturer company list then it will as shown in below:
Region Country Number of Company
Europe
Germany 94
Italy 87
Spain 30
Others 118
Asia Pacific
China 556
India 77
Japan 24
Korea 33
Taiwan 30
Other 63
America
Canada 21
United states 76
Others 9
Other Africa 12
Middle East 5
Table 2.1: Country wise manufacturer company list
Chapter 3
Theory
20
3.1 Solar Cell
Solar sell is basically p-n junction fabricated in a thin wafer or layer of semiconductor. The
electromagnetic radiation of solar energy can be directly converted electricity through the
photovoltaic effect. Being exposed to the sunlight, photons with energy greater than the band-
gap energy of the semiconductor are absorbed and create some electron hole pair proportional to
the incident radiation. As photons are absorbed in the cell their energy causes electrons to get
free, and they move to the bottom of the cell, and exit through the connecting wire which creates
electricity (flow of electrons). The bigger amount of the available sunlight the greater the flow of
electrons and the more electricity gets produced in the process. Under the influence of the
internal electric field of the p-n junction, these carries are swept apart and create a photocurrent
which is directly proportion to solar insulation. PV system naturally exhibits a non linear I-V and
P-V characteristics which vary with the radiant intensity and cell temperature.
Fig 3.1: solar cell
By combining these individual solar cells into photovoltaic panels we can produce enough
energy to power our homes as well as for many other purposes (space satellites).
21
3.2 Solar cells internal basic operation
The solar cell is the elementary building block of the photovoltaic technology. Solar cells are
made of semiconductor materials, such as silicon. One of the properties of semiconductors that
makes them most useful is that their conductivity may easily be modified by introducing
impurities into their crystal lattice. For instance, in the fabrication of a photovoltaic solar cell,
silicon, which has four valence electrons, is treated to increase its conductivity. On one side of
the cell, the impurities, which are phosphorus atoms with five valence electrons (n-donor),
donate weakly bound valence electrons to the silicon material, creating excess negative charge
carriers. On the other side, atoms of boron with three valence electrons (p-donor) create a greater
affinity than silicon to attract electrons. Because the p-type silicon is in intimate contact with the
n-type silicon a p-n junction is established and a diffusion of electrons occurs from the region of
high electron concentration (the n-type side) into the region of low electron concentration (p-type
side). When the electrons diffuse across the p-n junction, they recombine with holes on the p-
type side. However, the diffusion of carriers does not occur indefinitely, because the imbalance
of charge immediately on either sides of the junction originates an electric field. This electric
field forms a diode that promotes current to flow in only one direction. Ohmic metal-
semiconductor contacts are made to both the n-type and p-type sides of the solar cell, and the
electrodes are ready to be connected to an external load. When photons of light fall on the cell,
they transfer their energy to the charge carriers. The electric field across the junction separates
photo-generated positive charge carriers (holes) from their negative counterpart (electrons). In
this way an electrical current is extracted once the circuit is closed on an external load.
3.3 Basic attributes
Every location on Earth receives sunlight at least part of the year. The amount of solar radiation
that reaches any one spot on the Earth's surface varies according to the given parameters. Those
are
Geographic location
Time of day
Season
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Local landscape
Local weather
Because the Earth is round, the sun strikes the surface at different angles, ranging from 0° (just
above the horizon) to 90° (directly overhead). When the sun's rays are vertical, the Earth's
surface gets all the energy possible. The more slanted the sun's rays are, the longer they travel
through the atmosphere, becoming more scattered and diffuse. Because the Earth is round, the
frigid Polar Regions never get a high sun, and because of the tilted axis of rotation, these areas
receive no sun at all during part of the year.
The Earth revolves around the sun in an elliptical orbit and is closer to the sun during part of the
year. When the sun is nearer the Earth, the Earth's surface receives a little more solar energy. The
Earth is nearer the sun when it is summer in the southern hemisphere and winter in the northern
hemisphere. However, the presence of vast oceans moderates the hotter summers and colder
winters one would expect to see in the southern hemisphere as a result of this difference.
The 23.5° tilt in the Earth's axis of rotation is a more significant factor in determining the amount
of sunlight striking the Earth at a particular location. Tilting results for longer days in the
northern hemisphere from the spring (vernal) equinox to the fall (autumnal), equinox and longer
days in the southern hemisphere during the other 6 months. Days and nights are both exactly 12
hours long on the equinoxes, which occur each year on or around March 23 and September 22.
Countries such as the United States, which lie in the middle latitudes, receive more solar energy
in the summer not only because days are longer, but also because the sun is nearly overhead. The
sun's rays are far more slanted during the shorter days of the winter months. Cities such as
Denver, Colorado, (near 40° latitude) receive nearly three times more solar energy in June than
they do in December.
The rotation of the Earth is also responsible for hourly variations in sunlight. In the early
morning and late afternoon, the sun is low in the sky. Its rays travel further through the
atmosphere than at noon, when the sun is at its highest point. On a clear day, the greatest amount
of solar energy reaches a solar collector around solar noon.
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3.4 Working principle
Solar (or photovoltaic) cells convert the sun’s energy into electricity. Whether they’re adorning
your calculator or orbiting our planet on satellites, they rely on the photoelectric effect: the
ability of matter to emit electrons when a light is shone on it.
Silicon is what is known as a semi-conductor, meaning that it shares some of the properties of
metals and some of those of an electrical insulator, making it a key ingredient in solar cells. Let’s
take a closer look at what happens when the sun shines onto a solar cell.
Sunlight is composed of miniscule particles called photons, which radiate from the sun. As these
hit the silicon atoms of the solar cell, they transfer their energy to lose electrons, knocking them
clean off the atoms. The photons could be compared to the white ball in a game of pool, which
passes on its energy to the colored balls it strikes.
Freeing up electrons is however only half the work of a solar cell: it then needs to herd these
stray electrons into an electric current. This involves creating an electrical imbalance within the
cell, which acts a bit like a slope down which the electrons will flow in the same direction.
Creating this imbalance is made possible by the internal organization of silicon. Silicon atoms
are arranged together in a tightly bound structure. By squeezing small quantities of other
elements into this structure, two different types of silicon are created: n-type, which has spare
electrons, and p-type, which is missing electrons, leaving ‘holes’ in their place.
When these two materials are placed side by side inside a solar cell, the n-type silicon’s spare
electrons jump over to fill the gaps in the p-type silicon. This means that the n-type silicon
becomes positively charged, and the p-type silicon is negatively charged, creating an electric
field across the cell. Because silicon is a semi-conductor, it can act like an insulator, maintaining
this imbalance.
As the photons smash the electrons off the silicon atoms, this field drives them along in an
orderly manner, providing the electric current to power calculators, satellites and everything in
between.
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3.5 Diffuse and Direct Solar Radiation
As sunlight passes through the atmosphere, some of it is absorbed, scattered, and reflected by the
following factors.
Air molecules
Water vapor
Clouds
Dust
Pollutants
Forest fires
Volcanoes.
Those parameters are diffuse solar radiation. The solar radiation that reaches the Earth's surface
without being diffused is called direct beam solar radiation. The sum of the diffuse and direct
solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam
radiation by 10% on clear, dry days and by 100% during thick, cloudy days.
3.6 Measurement
Scientists measure the amount of sunlight falling on specific locations at different times of the
year. They then estimate the amount of sunlight falling on regions at the same latitude with
similar climates. Measurements of solar energy are typically expressed as total radiation on a
horizontal surface or as total radiation on a surface tracking the sun.
Radiation data for solar electric (photovoltaic) systems are often represented as kilowatt-hours
per square meter (kWh/m2). Direct estimates of solar energy may also be expressed as watts per
square meter (W/m2).
25
Radiation data for solar water heating and space heating systems are usually represented in
British thermal units per square foot (Btu/ft2).
3.7 Solar Energy Resources
Solar radiation, often called the solar resource, is a general term for the electromagnetic
radiation emitted by the sun. Solar radiation can be captured and turned into useful forms of
energy, such as heat and electricity, using a variety of technologies. However, the technical
feasibility and economical operation of these technologies at a specific location depends on the
available solar resource.
3.8 Different Materials of solar cell
A solar cell consists of semiconductor materials. Materials presently used for photovoltaic solar
cells include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium
telluride, and copper indium selenide/sulfide. Currently available solar cells are made from bulk
materials that are cut into wafers between 180 to 240 micrometers thick that are then processed
like other semiconductors.
Other materials are made as thin-films layers, organic dyes, and organic polymers that are
deposited on supporting substrates. A third group are made from nanocrystals and used as
quantum dots (electron-confined nanoparticles). Silicon remains the only material that is well-
researched in both bulk and thin-film forms.
3.8.1 Crystalline silicon:
a. Monocrystalline silicon (c-Si): Often made using the Czochralski process. Single-crystal
wafer cells tend to be expensive, and because they are cut from cylindrical ingots, do not
completely cover a square solar cell module without a substantial waste of refined silicon. Hence
most c-Si panels have uncovered gaps at the four corners of the cells.
26
b. Polycrystalline silicon or multicrystalline silicon (poly-Si or mc-Si): made from cast square
ingots — large blocks of molten silicon carefully cooled and solidified. Poly-Si cells are less
expensive to produce than single crystal silicon cells, but are less efficient. United States
Department of Energy data show that there were a higher number of polycrystalline sales than
monocrystalline silicon sales.
c. Ribbon silicon is a type of polycrystalline silicon: it is formed by drawing flat thin films
from molten silicon and results in a polycrystalline structure. These cells have lower efficiencies
than poly-Si, but save on production costs due to a great reduction in silicon waste, as this
approach does not require sawing from ingots.
d. Mono-like-multi silicon: Developed in the 2000s and introduced commercially around 2009,
mono-like-multi, or cast-mono, uses existing polycrystalline casting chambers with small "seeds"
of mono material. The result is a bulk mono-like material with poly around the outsides. When
sawn apart for processing, the inner sections are high-efficiency mono-like cells (but square
instead of "clipped"), while the outer edges are sold off as conventional poly. The result is line
that produces mono-like cells at poly-like prices.
3.8.2 Thin films:
Thin-film technologies reduce the amount of material required in creating the active material of
solar cell. Most thin film solar cells are sandwiched between two panes of glass to make a
module. Since silicon solar panels only use one pane of glass, thin film panels are approximately
twice as heavy as crystalline silicon panels. The majority of film panels have significantly lower
conversion efficiencies, lagging silicon by two to three percentage points. Thin-film solar
technologies have enjoyed large investment due to the success of First Solar and the largely
unfulfilled promise of lower cost and flexibility compared to wafer silicon cells, but they have
not become mainstream solar products due to their lower efficiency and corresponding larger
area consumption per watt production. Cadmium telluride (CdTe), copper indium gallium
selenide (CIGS) and amorphous silicon (A-Si) are three thin-film technologies often used as
outdoor photovoltaic solar power production. CdTe technology is most cost competitive among
them. CdTe technology costs about 30% less than CIGS technology and 40% less than A-Si
technology in 2011.
27
3.8.3 Cadmium telluride solar cell:
A cadmium telluride solar cell uses a cadmium telluride (CdTe) thin film, a semiconductor layer
to absorb and convert sunlight into electricity. Solarbuzz has reported that the lowest quoted
thin-film module price stands at US$0.84 per watt-peak, with the lowest crystalline silicon (c-Si)
module at $1.06 per watt-peak.
The cadmium present in the cells would be toxic if released. However, release is impossible
during normal operation of the cells and is unlikely during fires in residential roofs. A square
meter of CdTe contains approximately the same amount of Cd as a single C cell Nickel-cadmium
battery, in a more stable and less soluble form.
3.8.4 Copper indium gallium selenide:
Copper indium gallium selenide (CIGS) is a direct band gap material. It has the highest
efficiency (~20%) among thin film materials (see CIGS solar cell). Traditional methods of
fabrication involve vacuum processes including co-evaporation and sputtering. Recent
developments at IBM and Nanosolar attempt to lower the cost by using non-vacuum solution
processes.
3.8.5 Gallium arsenide multijunction:
High-efficiency multijunction cells were originally developed for special applications such as
satellites and space exploration, but at present, their use in terrestrial concentrators might be the
lowest cost alternative in terms of $/kWh and $/W.These multijunction cells consist of multiple
thin films produced using metalorganic vapour phase epitaxy. A triple-junction cell, for example,
may consist of the semiconductors: GaAs, Ge, and GaInP2. Each type of semiconductor will
have a characteristic band gap energy which, loosely speaking, causes it to absorb light most
efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a
portion of the spectrum. Combinations of semiconductors are carefully chosen to absorb nearly
all of the solar spectrum, thus generating electricity from as much of the solar energy as possible.
GaAs based multijunction devices are the most efficient solar cells to date. In October 15, 2012,
triple junction metamorphic cell reached a record high of 44%.
28
Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP),
gallium arsenide GaAs, and germanium Ge p–n junctions, are seeing demand rapidly rise.
Between December 2006 and December 2007, the cost of 4N gallium metal rose from about
$350 per kg to $680 per kg. Additionally, germanium metal prices have risen substantially to
$1000–1200 per kg this year. Those materials include gallium (4N, 6N and 7N Ga), arsenic (4N,
6N and 7N) and germanium, pyrolitic boron nitride (pBN) crucibles for growing crystals, and
boron oxide, these products are critical to the entire substrate manufacturing industry.
Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time
World Solar Challenge winners Nuna in 2003, 2005 and 2007, and also by the Dutch solar cars
Solutra (2005), Twente One (2007) and 21Revolution (2009).
3.8.6 Light-absorbing dyes (DSSC) :
Dye-sensitized solar cells (DSSCs) are made of low-cost materials and do not need elaborate
equipment to manufacture, so they can be made in a DIY fashion, possibly allowing players to
produce more of this type of solar cell than others. In bulk it should be significantly less
expensive than older solid-state cell designs. DSSC's can be engineered into flexible sheets, and
although its conversion efficiency is less than the best thin film cells, its price/performance ratio
should be high enough to allow them to compete with fossil fuel electrical generation.
Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of light-absorbing
material. The dye-sensitized solar cell depends on a mesoporous layer of nanoparticulate
titanium dioxide to greatly amplify the surface area (200–300 m2/g TiO2, as compared to
approximately 10 m2/g of flat single crystal). The photogenerated electrons from the light
absorbing dye are passed on to the n-type TiO2, and the holes are absorbed by an electrolyte on
the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which can
be liquid or solid. This type of cell allows a more flexible use of materials, and is typically
manufactured by screen printing or use of Ultrasonic Nozzles, with the potential for lower
processing costs than those used for bulk solar cells. However, the dyes in these cells also suffer
from degradation under heat and UV light, and the cell casing is difficult to seal due to the
solvents used in assembly. In spite of the above, this is a popular emerging technology with some
commercial impact forecast within this decade. The first commercial shipment of DSSC solar
modules occurred in July 2009 from G24i Innovations.
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3.8.7 Quantum Dot Solar Cells (QDSCs) :
Quantum dot solar cells (QDSCs) are based on the Gratzel cell, or dye-sensitized solar cell,
architecture but employ low band gap semiconductor nanoparticles, fabricated with such small
crystallite sizes that they form quantum dots (such as CdS, CdSe, Sb2S3, PbS, etc.), instead of
organic or organometallic dyes as light absorbers. Quantum dots (QDs) have attracted much
interest because of their unique properties. Their size quantization allows for the band gap to be
tuned by simply changing particle size. They also have high extinction coefficients, and have
shown the possibility of multiple exciton generation.
In a QDSC, a mesoporous layer of titanium dioxide nanoparticles forms the backbone of the cell,
much like in a DSSC. This TiO2 layer can then be made photoactive by coating with
semiconductor quantum dots using chemical bath deposition, electrophoretic deposition, or
successive ionic layer adsorption and reaction. The electrical circuit is then completed through
the use of a liquid or solid redox couple. During the last 3–4 years, the efficiency of QDSCs has
increased rapidly with efficiencies over 5% shown for both liquid-junction and solid state
cells.[44] In an effort to decrease production costs of these devices, the Prashant Kamat research
group[45] recently demonstrated a solar paint made with TiO2 and CdSe that can be applied using
a one-step method to any conductive surface and have shown efficiencies over 1%.
3.8.8 Organic/polymer solar cells:
Organic solar cells are a relatively novel technology, yet hold the promise of a substantial price
reduction (over thin-film silicon) and a faster return on investment. These cells can be processed
from solution, hence the possibility of a simple roll-to-roll printing process, leading to
inexpensive, large scale production.
Organic solar cells and polymer solar cells are built from thin films (typically 100 nm) of organic
semiconductors including polymers, such as polyphenylene vinylene and small-molecule
compounds like copper phthalocyanine (a blue or green organic pigment) and carbon fullerenes
and fullerene derivatives such as PCBM. Energy conversion efficiencies achieved to date using
conductive polymers are low compared to inorganic materials. However, it has improved quickly
in the last few years and the highest NREL (National Renewable Energy Laboratory) certified
efficiency has reached 8.3% for the Konarka Power Plastic.[47] In addition, these cells could be
beneficial for some applications where mechanical flexibility and disposability are important.
30
These devices differ from inorganic semiconductor solar cells in that they do not rely on the
large built-in electric field of a PN junction to separate the electrons and holes created when
photons are absorbed. The active region of an organic device consists of two materials, one
which acts as an electron donor and the other as an acceptor. When a photon is converted into an
electron hole pair, typically in the donor material, the charges tend to remain bound in the form
of an exciton, and are separated when the exciton diffuses to the donor-acceptor interface. The
short exciton diffusion lengths of most polymer systems tend to limit the efficiency of such
devices. Nano-structured interfaces, sometimes in the form of bulk hetero-junctions, can improve
performance.
In 2011, researchers at the Massachusetts Institute of Technology and Michigan State University
developed the first highly efficient transparent solar cells that had a power efficiency close to 2%
with a transparency to the human eye greater than 65%, achieved by selectively absorbing the
ultraviolet and near-infrared parts of the spectrum with small-molecule compounds. Researchers
at UCLA more recently developed an analogous polymer solar cell, following the same
approach, that is 70% transparent and has a 4% power conversion efficiency. The efficiency
limits of both opaque and transparent organic solar cells were recently outlined. These
lightweight, flexible cells can be produced in bulk at a low cost, and could be used to create
power generating windows.
3.8.9 Silicon thin films:
Silicon thin-film cells are mainly deposited by chemical vapor deposition (typically plasma-
enhanced, PE-CVD) from silane gas and hydrogen gas. Depending on the deposition parameters,
this can yield.
Amorphous silicon (a-Si or a-Si:H): An amorphous silicon (a-Si) solar cell is made of
amorphous or microcrystalline silicon and its basic electronic structure is the p-i-n junction. a-Si
is attractive as a solar cell material because it is abundant and non-toxic (unlike its CdTe
counterpart) and requires a low processing temperature, enabling production of devices to occur
on flexible and low-cost substrates. As the amorphous structure has a higher absorption rate of
light than crystalline cells, the complete light spectrum can be absorbed with a very thin layer of
photo-electrically active material. A film only 1 micron thick can absorb 90% of the usable solar
31
energy. This reduced material requirement along with current technologies being capable of
large-area deposition of a-Si, the scalability of this type of cell is high. However, because it is
amorphous, it has high inherent disorder and dangling bonds, making it a bad conductor for
charge carriers. These dangling bonds act as recombination centers that severely reduce the
carrier lifetime and pin the Fermi level so that doping the material to n- or p- type is not possible.
Amorphous Silicon also suffers from the Staebler-Wronski effect, which results in the efficiency
of devices utilizing amorphous silicon dropping as the cell is exposed to light. The production of
a-Si thin film solar cells uses glass as a substrate and deposits a very thin layer of silicon by
plasma-enhanced chemical vapor deposition (PECVD). A-Si manufacturers are working towards
lower costs per watt and higher conversion efficiency with continuous research and development
on Multijunction solar cells for solar panels.
Amorphous silicon has a higher bandgap (1.7 eV) than crystalline silicon (c-Si) (1.1 eV), which
means it absorbs the visible part of the solar spectrum more strongly than the infrared portion of
the spectrum. As nc-Si has about the same bandgap as c-Si, the nc-Si and a-Si can
advantageously be combined in thin layers, creating a layered cell called a tandem cell. The top
cell in a-Si absorbs the visible light and leaves the infrared part of the spectrum for the bottom
cell in nc-Si.
Protocrystalline silicon or Nanocrystalline silicon (nc-Si or nc-Si:H): protocrystalline silicon
with a low volume fraction of nanocrystalline silicon is optimal for high open circuit voltage.
These types of silicon present dangling and twisted bonds, which results in deep defects (energy
levels in the band gap) as well as deformation of the valence and conduction bands (band tails).
The solar cells made from these materials tend to have lower energy conversion efficiency than
bulk silicon, but are also less expensive to produce. The quantum efficiency of thin film solar
cells is also lower due to reduced number of collected charge carriers per incident photon.
3.8.10 Indium Gallium Nitride:
The ability to perform band gap engineering with Indium gallium nitride (InGaN) over a range
that provides a good spectral match to sunlight makes InGaN suitable for solar photovoltaic
cells. It is possible to grow multiple layers with different band gaps, as the material is relatively
insensitive to defects introduced by a lattice mismatch between the layers. A two-layer
multijunction cell with bandgaps of 1.1 eV and 1.7 eV can attain a theoretical 50% maximum
32
efficiency, and by depositing multiple layers tuned to a wide range of bandgaps an efficiency up
to 70% is theoretically expected.
Significant photoresponse was obtained from experimental InGaN single-junction devices. In
addition to controlling the optical properties, which results in band gap engineering, photovoltaic
device performance can be improved by engineering the microstructure of the material to
increase the optical path length and provide light trapping. Growing
nanocolumns on the device can further result in resonant interaction with light, and InGaN
nanocolumns have been successfully deposited on SiO2 using plasma enhanced evaporation.
3.9 Important and Efficient of Solar Energies
Already, the sun’s contribution to human energy needs is substantial — worldwide, solar
electricity generation is a growing, multibillion dollar industry. But solar ’s share of the total
energy market remains rather small, well below 1 percent of total energy consumption, compared
with roughly 85 percent from oil, natural gas, and coal.
Those fossil fuels cannot remain the dominant sources of energy forever. Whatever, the precise
timetable for their depletion, oil and gas supplies will not keep up with growing energy demands.
Coal is available in abundance, but its use exacerbates air and water pollution problems, and coal
contributes even more substantially than the other fossil fuels to the buildup of carbon dioxide in
the atmosphere.
For a long-term, sustainable energy source, solar power offers an attractive alternative. Its
availability far exceeds any conceivable future energy demands. It is environmentally clean, and
its energy is transmitted from the sun to the Earth free of charge. But exploiting the sun’s power
is not without challenges. Overcoming the barriers to widespread solar power generation will
require engineering innovations in several arenas — for capturing the sun’s energy, converting it
to useful forms, and storing it for use when the sun itself is obscured.
Many of the technologies to address these issues are already in hand. Dishes can concentrate the
sun’s rays to heat fluids that drive engines and produce power, a possible approach to solar
33
electricity generation. Another popular avenue is direct production of electric current from
captured sunlight, which has long been possible with solar photovoltaic cells.
In commercial solar cells, most often made from silicon; typically convert sunlight into
electricity with an efficiency of only 10 percent to 20 percent, although some test cells do a little
better. Given their manufacturing costs, modules of today’s cells incorporated in the power grid
would produce electricity at a cost roughly 3 to 6 times higher than current prices, or 18-30 cents
per kilowatt hour [Solar Energy Technologies Program]. To make solar economically
competitive, engineers must find ways to improve the efficiency of the cells and to lower their
manufacturing costs.
Prospects for improving solar efficiency are promising. Current standard cells have a theoretical
maximum efficiency of 31 percent because of the electronic properties of the silicon material.
But new materials, arranged in novel ways, can evade that limit, with some multilayer cells
reaching 34 percent efficiency. Experimental cells have exceeded 40 percent efficiency.
Another idea for enhancing efficiency involves developments in nanotechnology, the
engineering of structures on sizes comparable to those of atoms and molecules, measured in
nanometers (one nanometer is a billionth of a meter).
Recent experiments have reported intriguing advances in the use of nanocrystals made from the
elements lead and selenium. In standard cells, the impact of a particle of light (a photon) releases
an electron to carry electric charge, but it also produces some useless excess heat. Lead-selenium
nanocrystals enhance the chance of releasing a second electron rather than the heat, boosting the
electric current output. Other experiments suggest this phenomenon can occur in silicon as well.
Theoretically the nanocrystal approach could reach efficiencies of 60 percent or higher, though it
may be smaller in practice. Engineering advances will be required to find ways of integrating
such nanocrystal cells into a system that can transmit the energy into a circuit.
34
3.10 Photovoltaic Solar Cells
A photovoltaic cell (PV cell) is a specialized semiconductor diode that converts visible light into
direct current (DC). Some PV cells can also convert infrared (IR) or ultraviolet (UV) radiation
into DC electricity. Photovoltaic cells are an integral part of solar-electric energy systems, which
are becoming increasingly important as alternative sources of utility power.
First used in about 1890, "photovoltaic" has two parts: photo, derived from the Greek word for
light, and volt, relating to electricity pioneer Alessandro Volta. And this is what photovoltaic
materials and devices do—they convert light energy into electrical energy, as French physicist
Edmond Becquerel discovered as early as 1839.
Becquerel discovered the process of using sunlight to produce an electric current in a solid
material. But it took more than another century to truly understand this process. Scientists
eventually learned that the photoelectric or photovoltaic effect caused certain materials to
convert light energy into electrical energy at the atomic level.
A number of solar cells electrically connected to each other and mounted in a single support
structure or frame is called a ‘photovoltaic module’. Modules are designed to supply electricity
at a certain voltage, such as a common 12 volt system. The current produced is directly
dependent on the intensity of light reaching the module.
Fig 3.2: Photovoltaic Installation
35
Several modules can be wired together to form an array. Photovoltaic modules and arrays
produce direct-current electricity. They can be connected in both series and parallel electrical
arrangements to produce any required voltage and current combination.
PV systems are already an important part of our daily lives. Simple PV systems provide power
for small consumer items such as calculators and wristwatches. More complicated systems
provide power for communications satellites, water pumps, and the lights, appliances, and
machines in some homes and workplaces. Many road and traffic signs also are now powered by
PV. In many cases, PV power is the least expensive form of electricity for these tasks
The operation of a photovoltaic (PV) cell requires 3 basic attributes:
• The absorption of light, generating either electron-hole pairs or excitons.
• The separation of charge carriers of opposite types.
• The separate extraction of those carriers to an external circuit.
Photovoltaic material of device converts process:
Light Photon Energy Electric Energy
Silicon Photovoltaic Cell= A device made of semiconductor materials that produce electricity
under light.
A p-n junction is created in silicon by a doping process:
Fig 3.3: p-n junction by doping process
36
The photons from the exposed light promoted electrons flowing from n-junction to p-junction
Fig 3.4: Electric current flow
3.11 Photovoltaic Cells Internal Basic Operation and Doping Process
The first PV cells were made of silicon combined, or doped, with other elements to affect the
behavior of electrons or holes (electron absences within atoms). Other materials, such as copper
indium selenide (CIS), cadmium telluride (CdTe), and gallium arsenide (GaAs), have been
developed for use in PV cells. In a PV cell, flat pieces of these materials are placed together, and
the physical boundary between them is called the P-N junction. The device is constructed in such
a way that the junction can be exposed to visible light, IR, or UV. When such radiation strikes
the P-N junction, a voltage difference is produced between the P type and N type materials.
Electrodes connected to the semiconductor layers allow current to be drawn from the device.
Doping process:
Doping for common semiconductor, e.g. silicon (Si) involves adding atoms with different
number of electrons to create unbalanced number of electrons in the base material (e.g.
Si)
The base material, after doping, with excessive electrons will carry –ve charge.
The base material, after doping, with deficit in electron will carry +ve charge.
37
Doping of silicon can be achieved by “ion implantation” or “diffusion” of Boron (B)
atom for +ve charge or of Arsenide (As) or Phosphorus (P) for –ve charge.
Fig 3.5: Phenomenon of doping process
3.12 How PV Cells are Made
The process of fabricating conventional single- and polycrystalline silicon PV cells begins with
very pure semiconductor-grade polysilicon - a material processed from quartz and used
extensively throughout the electronics industry. The polysilicon is then heated to melting
temperature, and trace amounts of boron are added to the melt to create a P-type semiconductor
material. Next, an ingot, or block of silicon is formed, commonly using one of two methods:
1) By growing a pure crystalline silicon ingot from a seed crystal drawn from the molten
polysilicon or
2) By casting the molten polysilicon in a block, creating a polycrystalline silicon material.
Individual wafers are then sliced from the ingots using wire saws and then subjected to a surface
etching process. After the wafers are cleaned, they are placed in a phosphorus diffusion furnace,
creating a thin N-type semiconductor layer around the entire outer surface of the cell. Next an
anti-reflective coating is applied to the top surface of the cell and electrical contacts are
imprinted on the top (negative) surface of the cell. An aluminized conductive material is
38
deposited on the back (positive) surface of each cell, restoring the P-type properties of the back
surface by displacing the diffused phosphorus layer. Each cell is then electrically tested, sorted
based on current output, and electrically connected to other cells to form cell circuits for
assembly in PV modules
3.13 Types of Solar PV Cell
Basically two types of PV cell are most commonly used.
a. Flat plate systems:
On rigid flat surface
Usually from single wafers from 300 to 250 to 200 μm tk
Area: 170 cm2 approx.
Output power: 1 - 2 W approx.
Output Voltage: 0.5 v approx
Fig 3.6 (a): Flat plate system
B. Concentrator systems:
With optical components, e.g. lenses to direct and
concentrate sunlight on the PV cells of small areas.
Involving tracking mechanisms for directing the sunlight
Can increase power flux of sunlight hundreds of times
Heat dissipation required
39
Fig 3.6(b): Concentrator system
3.14 Solar Radiation Energy
Spectrum of sun light
Density on Earth surface: 1.4 KW/m2
Solar energy is associated with photons in the rays
Fig 3.7: Radiation of solar energy
40
3.15 Silicon Solar PV Product
Silicon Solar PV Panels
Fig 3.8: Sun Power Corp. Model SPR-215-BLK modules
Sun Power Corp. Model SPR-215-BLK modules Specification:
798 mm wide x 1559 mm long x 46 mm thick (with 72 cells)
Weight: 15 kg
Output: 40 v, 5.4 A (216 W)
Conversion efficiency: 17.3% (21.5% for all-black-contact cells)
Chapter 4
Modeling
42
4.1 Basic equations
The simplest solar cell model consists of diode and current source connected parallel. Current
source current is directly proportional to the solar radiation. The relationship between the PV cell
output current and terminal voltage according to the single-diode model is governed by the
equation is
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1 )p h DI I I
Where,
p hI = Light generated photo current (A)
DI =Diode current (A)
Fig 4.1: Equivalent Model of Single-Diode Photovoltaic cell
[ e x p ( ) 1 ] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ( 2 )D
q V
k TI I o
A
Where,
V = Diode voltage (V)
T = Temperature (K)
A = Diode ideality factor (A = 1 for ideal diode)
23k 1.380658 10 (Boltzmann constant [J/K])
43
19q 1.6 10 Charge of electron
I0=Reverse Saturation Current
[ e x p ( ) 1 ] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ( 3 )p hI Iq V
I oA k T
This basic equation of the elementary PV cell does not represent the I-V characteristic of practical one.
Practical modules are composed of several connected PV cells which requires the inclusion of
additional parameters Rs (series resistance) and Rp (parallel resistance). Then the I equation becomes
[ex p ( ) 1] ................................( 4 )S S
p hp
V R I V R IIo
A VI I
t R
Thermal voltage VT (V) can be calculated by
.k TV t
q
Where,
k = Boltzmann constant = 1.38·10-23 J/K
T =Temperature (K)
q = Charge of electron = 1.6·10-19 C
If we consider the two diode module of the PV cell then we get
1 2................................................................(5)ph d dI I I I
Where
1 11
[exp( ) 1]D
q VIo
A kI
T
44
2 22
[exp( ) 1]D
q VIo
A kI
T
Fig 4.2: Equivalent Model of Single-Diode Photovoltaic cell
So the final equation becomes
Where
p hI = is the current generated by the incident light
1DI =is the diode equation due to diffusion
2DI =is the diode equation due to charge recombination mechanisms
1I o , 2I o = are the reverse saturation current of the diodes d1 and d2 respectively
V = Diode voltage (V)
T = Temperature (K)
A1 & A2 = Diode ideality factor (A1 = 1 and A2=1.2 for ideal diode)
23k 1.380658 10 (Boltzmann constant [J/K])
19q 1.6 10 Charge of electron
1 21 2
[exp( ) 1] [exp( ) 1] .......................(6)S S
phS
p
V R I V R I V R IIo Io
A Vt AI I
Vt R
45
4.2 Basic parameters
Short-circuit current: The short-circuit current, Isc, is the current that flows through the
external circuit when the electrodes of the solar cell are short circuited. The short-circuit current
of a solar cell depends on the photon flux density incident on the solar cell, that is determined by
the spectrum of the incident light. For the standard solar cell measurements, the spectrum is
standardized to the AM 1.5 spectrum. The Isc depends on the area of the solar cell. In order to
remove the dependence of the Isc on the solar cell area, the short-circuit current density is often
used to describe the maximum current delivered by a solar cell. The maximum current that the
solar cell can deliver strongly depends on the optical properties (absorption in the absorber layer
and total reflection) of the solar cell.
Isc Iph K G
Where
Where, K is a constant and G is the irradiance (W/m²).
The open circuit voltage:
The open-circuit voltage is the voltage at which no current flows through the external circuit. It
is the maximum voltage that a solar cell can deliver. The Voc corresponds to the forward bias
voltage, at which the dark current compensates the photo-current. The Voc depends on the
photo-generated current density.
. l n ;A k T I p v
V o c I p v I oq I o
.
The maximum Power (Vmp):
In the maximum power where the voltage versus current product is maximum .Vmp is related to
Voc through the relation
0.8Vmp Voc
The maximum Current (Imp):
46
Imp is related to Isc through the relation of
0.9Imp Isc
Standard test conditions:
When
Irradiance equal to 1000W/m²
Cells Temperature equals to 25°C and
Spectral distribution (Air Mass) AM is equal to 1.5
Temperature
Solar cells work best at low temperatures, as determined by their material properties. All cell
materials lose efficiency as the operating temperature rises. Much of the light energy shining on
cells becomes heat, so it is good to either match the cell material to the operation temperature or
continually cool the cell.
Resistance
Larger electrical contacts can minimize electrical resistance, but covering a cell with large,
opaque metallic contacts would block too much incident light. Therefore, a trade off must be
made between loss due to resistance and loss due to shading effects. Typically, top-surface
contacts are designed as grids, with many thin, conductive fingers spread over the cell's surface.
However, it is difficult to produce a grid that maintains good electrical contact with a cell while
also resisting deterioration caused by changes in temperature or humidity. Generally, the back-
surface contact of a cell is simpler, often being just a layer of metal. Other designs for electrical
contacts include placing everything on the cell's back surface, or, as in some thin films,
depositing a thin layer of a transparent conducting oxide across the entire cell.
47
4.3 Matlab/Simulink
MATLAB
For analysis in our PV model we have to use Matlab software. MATLAB (matrix laboratory)
is a numerical computing environment and fourth-generation programming language which is
developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and
data, implementation of algorithms, creation of user interfaces, and interfacing with programs
written in other languages, including C, C++, Java, and Fortran.
Although MATLAB is intended primarily for numerical computing, an optional toolbox uses the
MuPAD symbolic engine, allowing access to symbolic computing capabilities. An additional
package, Simulink, adds graphical multi-domain simulation and Model-Based Design for
dynamic and embedded systems. MATLAB users come from various backgrounds of
engineering, science, and economics. MATLAB is widely used in academic and research
institutions as well as industrial enterprises. The MATLAB application is built around the
MATLAB language, and most use of MATLAB involves typing MATLAB code into the
Command Window (as an interactive mathematical shell), or executing text files containing
MATLAB code and functions.
SIMULINK
Simulink which is developed by MathWorks is a data flow graphical programming language
tool for modeling, simulating and analyzing multidomain dynamic systems. Its primary interface
is a graphical block diagramming tool and a customizable set of block libraries. It offers tight
integration with the rest of the MATLAB environment and can either drive MATLAB or be
scripted from it. Simulink is widely used in control theory and digital signal processing for
multidomain simulation and Model-Based Design.
48
Advantages of Simulink:
• State flow extends Simulink with a design environment for developing state machines
and flow charts.
• Simulink Verification and Validation enables systematic verification and validation of
models through modeling style checking, requirements traceability and model coverage
analysis.
• Simulink can automatically generate C source code for real-time implementation of
systems
• Capacity for quick iteration
• Reduce time for code generation and condition apply
• Do not need command window for input data
• More efficient, flexible and more faster
The basic difference between Matlab and Simulink:
MATLAB is the programming environment which need to program in the command window or
m files. Whereas SIMULINK is used to do simulations that have so many blocks. So we just
need to drag and connect them as whenever we need.
Modeling of a PV cell system by using Simulink is shown in below with details:
Simulink provides a library browser that allows you to select blocks from libraries of standard
blocks and a graphical editor that allows you to draw lines connecting the blocks. You can model
virtually any real-world dynamic system by selecting and interconnecting the appropriate
Simulink blocks.
A Simulink block diagram is a pictorial model of a dynamic system. It consists of a set of
symbols, called blocks, interconnected by lines. Each block represents an elementary dynamic
49
system that produces an output either continuously (a continuous block) or at specific points in
time (a discrete block). The lines represent connections of block inputs to block outputs. Every
block in a block diagram is an instance of a specific type of block. The type of the block
determines the relationship between a block's outputs and its inputs, states, and time. A block
diagram can contain any number of instances of any type of block needed to model a system.
Blocks represent elementary dynamic systems that Simulink knows how to simulate. A block
comprises one or more of the following: a set of inputs, a set of states, and a set of outputs. An
example of simple Simulink block diagram is described in below:
Simulink Example Block Diagram
Fig 4.3: SIMULINK example block diagram
In this example we use two constant value as A and B. Value of A and B are 5 and 2 respectively
.We consider a gain G=2 and finally use Chirp Signal block as a signal input. Finally we use ‘To
workspace’ and ‘Scope block’ for export data in command window and show the output result in
a graph respectively.
50
Outputs:
Fig 4.4: SIMULINK output result
4.4 Modeling for single diode ideal model
Modeling for the single diode ideal model we have to consider ideal diode’s basic equation. For
calculating the light generated current, our block diagram seems like as shown in below.
Fig 4.5: Block diagram for calculate light generated current
51
For calculating the Diode current, our block diagram seems like as shown in below.
Fig 4.6: Block diagram for calculate light generated current
For calculating the Reverse saturation current, our block diagram seems like as shown in below.
Fig 4.7: Block diagram for calculate Reverse saturation current
52
For calculating the current, our block diagram seems like as shown in below.
Fig 4.8: Block diagram for calculate current
After calculate the current, we can easily find out the P (power). For that we have to just
multiplication the current with voltage.
4.5 Modeling for single diode with Rs
For modeling the single diode with Rs (Series resistance), on such case we have to consider the
Ish (Shunt current). For calculate Ish, we have to know the value of Rs (Series resistance) & Rp
(Parallel resistance). Now if we want to input value of Rs & Rp then we have to consider
iteration. Basically in this part is calculated by using Matlab ‘m’ file. After finding the value of
Rs & Rp, we can easily solve Ish. The block diagram for Ish seems like as shown in below
53
Fig 4.9: Block diagram for Shunt Current
Now we can calculate the current for single diode with Rs and that diagram is look like as
shown in below
Fig 4.10: Current block diagram for single diode with Rs
54
4.6 Modeling for two diode with Rs
The two diode model with Rs the whole procedure is just as like as before (Single diode with)
but in this case we have to consider two diode Id1 & Id2 for diode 1 and diode 2 respectively.
Now calculate the I (current) for two diode with Rs that diagram is look like as shown in below
Fig 4.11: Current block diagram for two diode with Rs
55
4.7 Modeling of Subsystem for single diode with Rs
For modeling the overall system with a subsystem then we get a block diagram that look like as
shown in below:
Fig 4.12: Subsystem block diagram for single diode with Rs
In this subsystem we can see the two portions. Those are subsystem (shown as light blue block)
and PV cell model (shown as solar cell image).
In subsystem part is basically user define block. On that block a user can input his/her required
data for temperature, Sunlight/irradiance and Voltage.
In PV cell model we can input data value for different model of solar cell. For example if we use
BP solar MSX-60 then we have a particular value for open circuit voltage ,short circuit current,
temperature co-efficient of open circuit voltage, temperature co-efficient of short circuit current
etc. Again if we use MSX-50 model PV cell then its open circuit voltage, short circuit current,
temperature co-efficient of open circuit voltage, temperature co-efficient of short circuit current
etc will different. So by using this subsystem a user can easily handle the overall process.
Now after input as required the data we can observe the I-V & P-V characteristic curve.
56
4.8 Modeling of Subsystem for two diode with Rs
In this subsystem is also as same as before (Subsystem of Single diode with Rs) that we already
know. But main difference in this case is that we consider one more extra diode for modeling the
overall process.
Fig 4.13: Subsystem block diagram for two diode with Rs
This is the overall block diagram design define in our subsystem for two diode model with Rs.
Chapter5
Result
58
SIMULATION RESULTS:
It is clearly derived from (1) through (6), the PV array exhibits a highly nonlinear radiation and
temperature dependent I–V and P–V characteristic curve, being both curves simulated for the
parameters given in Table 5.1 for MSX-60 module by using the Simulink environment and
illustrated in figures for Standard temperature condition (1000 W/m2 and Temperature 298 K)
levels of solar radiation and cell temperature for varying internal parameters such as ideality
factor, series and shunt resistance to match the parameters (ISC, VOC, Imp, Vmp, Pmax) given
by manufactures.
Solarex MSX 60 Specifications (1kW/m2, 25°C) data is shown in below:
Table 5.1: Solarex MSX 60 Specifications data
Characteristics SPEC
Typical peak power (Pp) 60 W
Voltage at peak power (Vp) 17.1 V
Current at peak power (Ip) 3.5 A
Short-circuit current (ISC) 3.8 A
Open-circuit voltage (VOC) 21.1 V
Temperature coefficient of open-circuit voltage -73mV/°C
Temperature coefficient of short-circuit current (Ki) 3mV/°C
Approximate effect of temperature on power -0.38W/°C
Nominal operating cell temperature (NOCT) 49 °C
59
To obtain the value Vmp & Imp plot shown in figures. X-Axis gives the voltage corresponding
to peak or maximum power of the PV module and corresponding point at y-axis gives Imp.
If we observe the I-V & P-V curve for a single graph then it seems as shown in below:
Fig 5.1: I-V & P-V curve for single diode
0 5 10 15 20 25 300
Voltage
I-V & P-V curve
Vol
tage
0 5 10 15 20 25 300
Pow
er
60
Fig 5.2: I-V & P-V curve for single diode with Rs
0 5 10 15 20 250
Voltage
I-V & P-V curve
Vol
tage
0 5 10 15 20 250
Pow
er
61
Fig 5.3: I-V & P-V curve for two diode
0 5 10 15 20 250
Voltage
I-V & P-V curve
Vol
tage
0 5 10 15 20 250
Pow
er
62
Fig 5.4: I-V & P-V curve for two diode with Rs
0 5 10 15 20 250
Voltage
I-V & P-V curve
Vol
tage
0 5 10 15 20 250
Pow
er
63
5.1 Effect of Cell Temperature
Result for single diode I-V & P-V curve (Ns=36):
The effect of temperature on the maximum output power, Pm of the cell was investigated solar
Irradiance (Ir) value was taken as 600 (W/m2). The Ideality factor, A was taken as 1.2. The
Circuit Temperature (SPICE Environment Parameter) was varied from 0oC to 75oC.
Observations from simulations of Temperature variations are shown in Fig.5.7& Fig.5.8 and
Table 5.2. It can be observed that increase in temperature adversely affected the power obtained
from the solar cell and hence Pm. The reason of reduction in power with increase in temperature
is due to the increase in Id with temperature. For single cell, Vm fell by approx1.75mV/oC, and
for two cells, Vmfell by approx3.5mV/oC
64
Fig 5.5: single diode I-V characteristic curve
0 5 10 15 20 250
0.5
1
1.5
2
2.5
voltage
curren
t
Voltage Vs Current
Temp=0 C
Temp=25 CTemp=50 C
Temp=75 C
65
Fig 5.6: Two diode I-V characteristic curve
0 5 10 15 20 25 300
0.5
1
1.5
2
2.5
voltage
curren
t
Voltage Vs Current
Temp=0 C
Temp=25 CTemp=50 C
Temp=75 C
66
Fig 5.7: Single diode P-V characteristic curve
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
45
50
55
Voltage
Pow
er
Voltage Vs Power
Temp=0 C
Temp=25 C
Temp=50 C
Temp=75 C
67
Fig 5.8: Two diode P-V characteristic curve
0 5 10 15 20 250
5
10
15
20
25
30
35
40
45
voltage
Pow
er
Voltage Vs Power
Temp=0 C
Temp=25 CTemp=50 C
Temp=75 C
68
Table 5.2: Temperature Variation for Single diode & two diode
Temperature(°C) No series cell(Ns) 273 298 323 348
Pm(W)
36(Two diode)
42.5990 38.5953 34.4117 30.0569
Vm(V) 19.9000 17.8000 15.7000 13.6000
Im(A) 2.1407 2.1683 2.1918 2.2101
Pm(W)
36(single diode)
52.4128 46.4099 40.4974 34.6911
Vm(V) 24.0000 21.4000 18.9000 16.4000
Im(A) 2.1839 2.1687 2.1427 2.1153
Fig 5.9: Difference between two diode and single diode compare with ideal diode for power
7.587213.5901
19.502625.3089
17.40121.1017
25.588329.9431
0
5
10
15
20
25
30
35
Difference
Temperature
Single Diode
Two Diode
69
Fig 5.10: Difference between two diode and single diode compare with ideal diode for voltage
Fig 5.11: Difference between two diode and single diode compare with ideal diode for current
6.9
4.3
1.80.7
2.8
0.71.4
3.5
0
1
2
3
4
5
6
7
8
Difference
Temperature
Single Diode
Two Diode
1.31611.3313
1.3573
1.3847
1.3593
1.3317
1.30821.2899
1.24
1.26
1.28
1.3
1.32
1.34
1.36
1.38
1.4
Difference
Temperature
Single Diode
Two Diode
70
5.2 Effect of Irradiance
Changes in I-V and P-V Characteristics are plotted for the variation in Irradiance, Ir, in Fig.5.14
Ideality factor, A is taken as 1.2. The Circuit temperature (SPICE Environment Parameter) was
kept at 25oC. Irradiance was taken 400 W/m2 ,600 W/m2 , 800 W/m2,100 W/m2.From Fig.
5.15 and Table 5.3, it can be observed that the irradiance value impacted the short-circuit
current, Isc, as well as open-circuit voltage, Voc, but more affected was the value of Isc. As
irradiance value increased, the short -circuit increased and the maximum power, Pm also
increased.
71
Result for I-V & P-V curve(Ns=36):
Fig 5.12: Single diode I-V characteristic curve
0 5 10 15 20 25 300
0.5
1
1.5
2
2.5
3
3.5
4
voltage
curren
t
voltage Vs current
Irradiance=1
Irradiance=.8
Irradiance=.6
Irradiance=.4
72
Fig 5.13: Two diode I-V characteristic curve
0 2 4 6 8 10 12 14 16 18 20 220
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
voltage
curr
ent
voltage Vs current
Irradiance=1
Irradiance=.8Irradiance=.6
Irradiance=.4
73
Fig 5.14: Single diode P-V characteristic curve
0 5 10 15 20 250
10
20
30
40
50
60
70
voltage
Pow
er
voltage Vs power
Irradiance=1
Irradiance=.8Irradiance=.6
Irradiance=.4
74
Fig 5.15: Two diode P-V characteristic curve
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
voltage
Pow
er
Voltage Vs Power
Irradiance=1
Irradiance=.8Irradiance=.6
Irradiance=.4
75
Table 5.3: Irradiance Variation for Single diode & two diode
Irradiance(W/m2) No series cell(Ns) 1 .8 .6 .4
Pm(W)
36(Two diode)
59.2289 46.7111 34.1934 22.3043
Vm(V) 16.1000 16.1000 16.1000 15.1000
Im(A) 3.6788 2.9013 2.1238 1.4771
Pm(W)
36(single diode)
69.6928 54.9860 40.4974 26.3007
Vm(V) 19.5000 19.2000 18.9000 18.4000
Im(A) 3.5740 2.8639 2.1427 1.4294
Fig 5.16: Difference between two diode and single diode compare with ideal diode for power
9.69285.014
19.5026
33.6993
0.7711
13.2889
25.8066
37.6954
0
5
10
15
20
25
30
35
40
Difference
Irradiance
Single Diode
Two Diode
76
Fig 5.17: Difference between two diode and single diode compare with ideal diode for voltage
Fig 5.18: Difference between two diode and single diode compare with ideal diode for current
2.42.1
1.81.3
1 1 1
2
0
0.5
1
1.5
2
2.5
3
Difference
Irradiance
Single Diode
Two Diode
0.074 0.6361 1.3573 2.07060.1788 0.5987 1.3762 2.02290
0.5
1
1.5
2
2.5
Difference
Irradiance
Single Diode
Two Diode
77
5.3 Effect of Ideality Factor
I-V and P-V characteristics were simulated for variation in Ideality Factor. The Circuit
temperature (SPICE Environment Parameters) was kept at 25oC. Irradiance (Ir) value was taken
as 600 W/m2. Ideality factor, N was varied as 1, 1.2, 1.3 and 1.5.
Fig 5.19: Single diode I-V characteristic curve varying ideality factor
0 5 10 15 20 25 300
0.5
1
1.5
2
2.5
voltage
curr
ent
Voltage Vs Current
Alpha=1
Alpha=1.2Alpha=1.3
Alpha=1.5
78
Fig 5.20: Two diode I-V characteristic curvevarying ideality factor
0 5 10 15 200
0.5
1
1.5
2
2.5
voltage
curren
t
Voltage Vs Current at different value of Alpha1 & Alpha2
Alpha1=1 & Alpha2=1.2
Alpha1=1.2 & Alpha2=1.2Alpha1=1.5 & Alpha2=1.2
Alpha1=1.8& Alpha2=1.2
79
Fig 5.21: Single diode P-V characteristic curve varying ideality factor
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
45
50
Voltage Vs Power
voltage
Pow
er
Alpha=1
Alpha=1.2Alpha=1.3
Alpha=1.5
80
Fig 5.22: Single diode P-V characteristic curve varying ideality factor
0 5 10 15 20 25 300
5
10
15
20
25
30
35
40
45
50
voltage
Pow
er
Voltage Vs Power at different value of Alpha1 & Alpha2
Alpha1=1 & Alpha2=1.2
Alpha1=1.2 & Alpha2=1.2Alpha1=1.5 & Alpha2=1.2
Alpha1=1.8& Alpha2=1.2
81
Table 5.4: Ideality Factor Variation
Alpha1 &
Alpha2
No series
cell(Ns)
Alpha1 =1
Alpha2=1.2
Alpha1=1.2
Alpha2=1.2
Alpha1=1.5
Alpha2=1.2
Alpha1=1.8
Alpha2=1.2
Pm(W)
36(Two
diode)
34.4117 39.6536 41.3687 41.4674
Vm(V) 15.7000 18.1000 18.9000 18.9000
Im(A) 2.1918 2.1908 2.1888 2.1940
Pm(W)
36(single
diode)
33.7455 40.4974 43.8712 50.6215
Vm(V) 15.7000 18.9000 20.5000 23.6000
Im(A) 2.1494 2.1427 2.1401 2.1450
Fig 5.23: Difference between two diode and single diode compare with ideal diode for power
26.2545
19.502616.1288
9.3785
25.5883
20.3464 18.6313 18.5326
0
5
10
15
20
25
30
Difference
Ideality Factor
Single Diode
Two Diode
82
Fig 5.24: Difference between two diode and single diode compare with ideal diode for voltage
Fig 5.25: Difference between two diode and single diode compare with ideal diode for current
1.4 1.8
3.4
6.5
1.4 11.8 1.8
0
1
2
3
4
5
6
7
Difference
Ideality Factor
Single Diode
Two Diode
1.35061.3573 1.3573 1.355
1.3082 1.3092 1.3112 1.306
1.28
1.29
1.3
1.31
1.32
1.33
1.34
1.35
1.36
1.37
Difference
Ideality Factor
Single Diode
Two Diode
83
5.4 Effect of Rs
The variation of the maximum output power of the cell was investigated for Rs values of
0.39(Calculated),0.1,0.01, 0.001ohms. Irradiance (Ir) value was taken as 600 W/m2 which
corresponds to Iph = 3.8A. The Circuit Temperature (SPICE Environment Parameters) was taken
as 25oC. The Ideality factor, A was taken as 1.2.
Result for I-V & P-V characteristics curve With Rs:
Fig 5.26: Single diode I-V characteristic curve(Effect of Rs)
0 2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
2.5
3
voltage
curr
ent
Voltage Vs Current at difference Rs
Rs=.39(calculated)
Rs=.1Rs=.01
Rs=.001
84
Fig 5.26: Two diode I-V characteristic curve(Effect of Rs)
0 5 10 15 20 250
0.5
1
1.5
2
2.5
voltage
curren
t
Voltage Vs Current at different Rs
Rs=.39(calculated)
Rs=.1Rs=.01
Rs=.001
85
Fig 5.27: Single diode P-V characteristic curve (Effect of Rs)
0 2 4 6 8 10 12 14 16 18 200
5
10
15
20
25
30
35
40
voltage
Pow
er
Voltage Vs Power at different Rs
Rs=.39(calculated)
Rs=.1Rs=.01
Rs=.001
86
Fig 5.28: Two diode P-V characteristic curve (Effect of Rs)
0 5 10 15 20 250
5
10
15
20
25
30
35
40
45
voltage
Pow
er
Voltage Vs Power at different Rs
Rs=.39(calculated)
Rs=.1Rs=.01
Rs=.001
87
Table 5.5: Rs variation
Rs(Ω) No series
cell(Ns)
.39(Calculated) .1 .01 .001
Pm(W)
36(Two
diode)
8.4742 25.5200 39.6259 41.1753
Vm(V) 11.0100 13.0100 18.0100 19.0100
Im(A) 0.7697 1.9616 2.2002 2.1660
Pm(W)
36(single
diode)
5.9167 18.8955 32.0465 33.26944
Vm(V) 9.1000 10.1000 15.1000 16.1000
Im(A) 0.6502 1.8708 2.1223 2.0664
Fig 5.28: Difference between two diode and single diode compare with ideal diode for power
54.0833
41.1045
27.9535 26.73056
51.5258
34.48
20.3741 18.8247
0
10
20
30
40
50
60
Difference
Variation of Rs
Single Diode
Two Diode
88
Fig 5.29: Difference between two diode and single diode compare with ideal diode for voltage
Fig 5.30: Difference between two diode and single diode compare with ideal diode for current
89
21
6.09
4.09
0.911.91
0
1
2
3
4
5
6
7
8
9
10
Difference
Variation of Rs
Single Diode
Two Diode
2.8498
1.62921.3777 1.4336
2.7303
1.53841.2998 1.334
0
0.5
1
1.5
2
2.5
3
Difference
Variation
Single Diode
Two Diode
89
Result for single diode I-V & P-V curve With Rs and Rp effect (Ns=36):
Tc=323k ;Rs=.01;Rp=123
Fig 5.31: Single diode I-V characteristic curve
0 2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
2.5
3
3.5
4
voltage
curren
t
Voltage Vs Current
Irradiance=1
Irradiance=.8Irradiance=.6
Irradiance=.4
90
Fig 5.32: Single diode P-V characteristic curve
0 2 4 6 8 10 12 14 16 18 200
10
20
30
40
50
voltage
Pow
er
Voltage Vs Power
Irradiance=1
Irradiance=.8Irradiance=.6
Irradiance=.4
91
Result for two diode I-V & P-V curve (Ns=36) with Rs and Rp
Rs=.01ohm, .Rp=123 ohm
Irradiance=.6
Fig 5.33: Two diode I-V characteristic curve at different temperature
0 5 10 15 20 250
0.5
1
1.5
2
2.5
voltage
curren
t
Voltage Vs Current at different temperature
Temp=0 C
Temp=25 CTemp=50 C
Temp=75 C
92
Fig 5.34: Two diode P-V characteristic curve at different temperature
0 5 10 15 20 250
5
10
15
20
25
30
35
40
45
voltage
Pow
er
Voltage Vs Power at different temperature
Temp=0 C
Temp=25 CTemp=50 C
Temp=75 C
Chapter 6
Conclusion
94
6.1 Outcome of the work
A generalized PV model which is representative of the all PV cell, module, and array has been
developed with Matlab/Simulink and it has been verified with a PV cell and a commercial
module. The proposed model takes sunlight irradiance and cell temperature as input parameters
and outputs the I-V and P-V characteristics under various conditions. This model has also been
designed in the form of Simulink block libraries. The masked icon makes the block model more
user-friendly and a dialog box lets the users easily configure the PV model. Such a generalized
PV model is easy to be used for the implementation on Matlab/Simulink modeling and
simulation platform. Especially, in the context of the SimPowerSystem tool, there is now a
generalized PV model which can be used for the model and analysis in the field of solar PV
power conversion system.
6.2 Limitation and Suggestion
Limitation:
When we use this model for analysis then we get a simulate result as output but in realistic case
it is may not be exactly same. In such case there must be a few losses.
In this module we can input any value for our analysis purpose but sometimes in real case such
temperature does not possible to reach. For example if we input 6000 K then it will show an I-v
& P-V curve but in realistic case we never thought to analysis on such type temperature for a real
modeling.
A small variation in Rs will significantly affect the PV output power. That’s why we have to
consider a very small value of series resistance sometimes it is quit impossible for realistic
application.
95
Suggestion:
Though this model has a few limitations but it is easiest process to find out the I-V & P-V curve.
Because to observe the curve in realistic case it is not quit easy and it is also cost affected. That’s
why by changing different values for temperature, sunlight/irradiance or input voltage, it is
easiest and best procedure for prediction. After prediction and fulfill all condition we are now
ready to implement for realistic purpose.
6.3 Future work
Photovoltaic provides an extreme wide range of power. The presented examples show that it is
possible in many cases to replace conventional energy supply systems with a PV power supply.
Advantages (e.g. easy handling, low maintenance costs and less use of batteries) provide further
arguments for photovoltaic in photovolatically powered appliance section. In addition, in case of
grid-dependent PV systems, PV generators can be coupled with other power supplies, especially
in areas where solar radiation fluctuates strongly. In spite of higher costs, photovoltaic is often
more economic than laying grid connection. The applications of photovoltaic will increase both
for small-decentralized power supplies and for large power stations. This makes a significant
energy contribution. The rate of this progress will depend on the amount of expert knowledge,
contributes by those involved in the planning, construction and operation of PV system.
96
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