Report

ZOUHIR ISMAIL | ERASMUS REPORT | 2012/2013
Solar Energy
MODELING OF PHOTOVOLAIC PANELS

Solar Energy 2012/2013
ZOUHIR ISMAIL 1
Summary
Introduction ………………………………………………………………………….………………2
Mainstream renewable technologies ………………….…………………………………3
Wind power………………………………………………… …………………3
Hydropower………………………………………………………………………4
Biomass……………………………………………………………………………6
Solar energy……………………………………………… ……………………6
History of Photovoltaics …………………….…………………………………………………7
Objectives of my project…………….…………………………………………………………7
Solar cell structure…………….…………………………………………………..…………….8
Description of PV model………….………………………………………………….………9
Objectives of my project…………….…………………………………………………………8
Areas of operating PV model……………………………………………………………….14
V-I cures…………………………………………………………………………………..………....15
V-I curves for different radiations………………………………………………………15
V-P curves for different radiations………………………………………………………16
V-I curves for different temperatures………….………………………………………17
V-P curves for different temperatures……………………………………………..…18
Influence of series resistances………………………………………..……………………19
Influence of shunt resistances…………………………………………………………..…21
From modules to array……………………….……………………………….………………23
Serie/Parallel association…………………………………………………………23
Serie association……………………………………………..………………………24
Parallel association…………………………..………………………………………25
How to maximize energy (MPPT)………………………………..…………………………………………26
Conclusion……………………………………………………………………………………………………………...28
Bibliography……………………………………………………………………………………………………………29

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INTRODUCTION
The use of renewable energy sources, such as solar, wind and
hydraulic energies, is very old; they have been used since many centuries
before our time but humans were more interested in using fossil fuels due
to the low price of petroleum, so the renewable enegies were abandoned.
During recent years, due to the increase in fossil fuel prices and the
environmental problems caused by the use of conventional fuels, we are
reverting back to renewable energy sources.
Energy is called renewable because it is produced from inexhaustible
resources. It has long been exploited fossil fuels or "energy stock": oil,
coal, gas, primarily uranium. Clean, they improve the management of
local resources and create jobs. One of these is solar power.
In my project, i will focus on the solar energy and how does it work
by using a software « Matlab » which will allow me to model PV panels
and study their characterisitcs.

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Mainstream renewable technologies
Before to start talking about the solar panel, its characteristics and how
does it works, let’s have an idea about the main sources of renewable
enrgies.
Wind power :
An easy method to produce electricity is wind energy: the supplied by
the wind. The device able to perform this conversion is called wind
generator, this consists of a mechanical system of rotation which is
powered by blades as in old windmills. This rotary system is connected
to an electric generator whose axis joined to the driving system. In this
way the wind, forcing the blades to turn, drives the electric generator
which can be either a dynamo or an alternator (the alternator, in
comparison to the dynamo, presents the advantage of a higher efficiency).

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Hydropower :
Hydropower is a very low-emission energy greenhouse gas emissions.
This renewable energy source uses the movement of water powered by
the sun and gravity through the water cycle, tides and ocean currents.
They use the waterfalls, natural (waterfalls) or artificial (hydroelectric
dams), the flow of rivers and ocean currents (tidal thermohaline
circulation ...), hydropower plants produce mechanical energy converted
mostly to electricity.
The hydraulic energy represents 19% of total electricity production in the
world and 13% in France. This is the most used renewable energy source.
However, all the world's hydroelectric potential has not yet been
exploited.

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Biomass :
Biomass is the second renewable energy in
the world. It produces electricity, heat via
combustion of wastes and residues of plant
and animal organic matter.Through the
process of photosythesis, plants capture the
sun's energy. When the plants are burnt, they
release the sun's energy they contain. In this
way, biomass functions as a sort of natural
battery for storing solar energy.
Solar Energy
Photovoltaic solar energy comes from the
conversion of sunlight into electricity in
semiconductor materials such as silicon or
covered with a thin metallic layer. These
photosensitive materials have the property
of releasing their electrons under the
influence of external energy. This is the
photovoltaic effect. A photovoltaic solar
generator consists of photovoltaic modules themselves compound of
interconnected photovoltaic cells.

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Solar Energy
History of photovoltaics panels :
Photovoltaics is the process of converting sunlight directly into
electricity using solar cells. Today it is a rapidly growing and increasingly
important renewable alternative to conventional fossil fuel electricity
generation, but compared to other electricity generating technologies, it
is a relative newcomer, with the first practical photovoltaic devices
demonstrated in the 1950s. Research and development of photovoltaics
received its first major boost from the space industry in the 1960s which
required a power supply separate from "grid" power for satellite
applications. These space solar cells were several thousand times more
expensive than they are today and the perceived need for an electricity
generation method apart from grid power was still a decade away, but
solar cells became an interesting scientific variation to the rapidly
expanding silicon transistor development with several potentially
specialized niche markets. It took the oil crisis in the 1970s to focus world
attention on the desirability of alternate energy sources for terrestrial use,
which in turn promoted the investigation of photovoltaics as a means of
generating terrestrial power. Although the oil crisis proved short-lived
and the financial incentive to develop solar cells abated, solar cells had
entered the arena as a power generating technology. Their application and
advantage to the "remote" power supply area was quickly recognized and
prompted the development of terrestrial photovoltaics industry. Small
scale transportable applications (such as calculators and watches) were
utilised and remote power applications began to benefit from
photovoltaics.
In the 1980s research into silicon solar cells paid off and solar cells began
to increase their efficiency. In 1985 silicon solar cells achieved the
milestone of 20% efficiency. Over the next decade, the photovoltaic
industry experienced steady growth rates of between 15% and 20%,
largely promoted by the remote power supply market. The year 1997 saw

ZOUHIR ISMAIL 7
a growth rate of 38% and today solar cells are recognized not only as a
means for providing power and increased quality of life to those who do
not have grid access, but they are also a means of significantly
diminishing the impact of environmental damage caused by conventional
electricity generation in advanced industrial countries.
Objectives of my project :
Describe model of PV cell
Characterize V-I & V-P curves for different radiations G.
Characterize V-I & V-P curves for different temperatures T.
Study the influence Rs.
Study the influence of parrallel resistance Rsh.
Associate cells.
Propose algorythms to maximize energy.

ZOUHIR ISMAIL 8
Solar Cell Structure
A solar cell is an electronic
device which directly converts
sunlight into electricity. Light
shining on the solar cell produces
both a current and a voltage to
generate electric power. This
process requires firstly, a material
in which the absorption of light
raises an electron to a higher
energy state, and secondly, the
movement of this higher energy
electron from the solar cell into
an external circuit. The electron
then dissipates its energy in the
external circuit and returns to the
solar cell.
The basic steps in the operation of a solar cell are:
The light absorption in the material
The transfer of light energy to the electrons
The dissipation of power in the load and in parasitic resistances.

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Description of a PV model
A photovoltaic cell converts the solar energy into the electrical energy
by the photovoltaic effect. Solar cells are widely used in terrestrial and
space applications. The photovoltaic cells must be operated at their
maximum power point. The maximum power point varies with
illumination, temperature, radiation dose and other ageing effects.
A PV cell can be modeled by a current generator in parallel with a
diode. The photo current (Il) is a function of the solar irradiation. A
series resistor Rs and a parallel resistor represent respectively the
voltage loss and the leakage current of the cell. The diode D
characterises the non linear behavior of the cell and the dependency of
its performance on ambient temperature.

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Figure 2: The circuit diagram of the PV model with shunt resistance
The equations which describe the I-V characteristics of the cell
are:
 IL: photo current
 Temperature dependence of
the photo current IL.
 Series resistance Rs, which
gives a more accurate shape
between the maximum power
point and the open circuit
voltage.
 Shunt resistance Rsh in
parallel with the diode.
 Either allowing the diode
quality factor n to be- come a
variable parameter (instead of
being ﬁxed at either 1 or 2) or
introducing two parallel diodes
(one with A =1, one with A =2)
with indepen- dently set
saturation currents.

ZOUHIR ISMAIL 11
Modelisation of a PV cell on Simulink
Create Subsystem
2
-
1
+
PSS
Simulink-PS
Converter
Rsh
Rs
+-
DiodeControlled Current
Source
1
E
E
+
-
Solar panel

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==> We will simulate the model of the solar panel to verify its characteristics.
Figure 3 : Modeling of PV panel on Matlab/Simulink
Objectives :
 Characterise V-I & V-P curves for different radiations G.
 Characterise V-I & V-P curves for different temperatures

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In the above representation of I-V characteristic, a sign convention is used, which
takes as positive the current generated by the cell when the sun is shining and a positive
voltage is applied on the cell’s terminals. A real solar cell can be characterized by the
following fundamental parameters:
- Short Circuit Current: It is the
greatest value of the current generated
by a cell. It is produced under short
circuit conditions: V = 0
- Open circuit voltage: Corresponds
to the voltage drop across the diode
(p-n junction), when it is traversed by
the photocurrent Iph (namely ID=Iph)
when the generator current is I = 0. It reflects the voltage of the cell in the night,
- Maximum power point:Is the operating point A (Vmax, Imax) at which the power
dissipated in the resistive load is maximum: Pmax = Imax * Vmax
- Maximum efficiency: Is the ratio between the maximum power and the incident light
power
Figure 4 : Characteristics I-V of PV cell

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Areas of operation of solar module
AREA 1 AREA 2 AREA3
Figure 5 : Different operating areas
AREA 1 : the current remains constant regardless of the voltage,
PV generator operates as a current generator
AREA 2 : it’s the best area for the operation of the generator, where the point optimal
(characterized by a maximum power) can be determined.
AREA 3 : that zone is characterized by a change in current corresponding to
voltage nearly constant, in which case the generator is similar to a voltage
generator.
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
Current(A)
V-I curves for G=1000W/m²
Voltage (V)

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1) V-P curves for differents radiations
Figure 6 : Variation of current with different radiations
This simulation allows the appearance of values given by the manufacturers and those
features that are found on the model. From this simulation, we have:
Power max = 59,83 W and Voc= 17.1 V ===> Simulation
Power max = 60 W and Voc= 17,1 V ===> Manufacturers
The simulation results and those found on the label manufacturers
are almost the same.
0 5 10 15 20 25
0
10
20
30
40
50
60
X: 17.1
Y: 59.83
Voltage (V)
Power(W)
V-P curves for different radiations
400W/m²
600W/m²
800W/m²
1000W/m²

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2) V-I curves for differents radiations
Figure 7 : Variation of power output with different radiations
It can be observed from this figure that the short circuit current
decreases with decrease when the the radiation is increased.
Regarding the maximum power output of a photovoltaic cell, it is
clear that when the irradiance is higher, the cell generates more
power.
Obviously, irradiance has a large effect on short-circuit current.
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
Current(A)
Voltage (V)
V-I curves for different radiations
400W/m²
600W/m²
800W/m²
1000W/m²

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1) V-I curves for differents temperatures
Figure 8 : Variation of current output with different temperatures
If the temperature increases with a constant radiation, the open circuit
voltage Voc decreases with temperature. Increase the temperature 
Voc is low. The influence of temperature on Isc can be neglected in
most cases.
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
Voltage (V)
Current(A)
V-I curves for different temperatures
The
temperature increases

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2) V-P curves for differents temperatures
Figure 9 : Variation of power output with different temperatures
This figure displays the response of a solar cell to varying
temperature. You have to know that Contrary to popular belief, the
efficiency of a solar cell decreases with increasing temperature. The
reason for this, is that a higher temperature increases the conductivity of
the semiconductor.
0 5 10 15 20 25
0
10
20
30
40
50
60
V-P curves for different temperatures
Voltage (V)
Power(W)
The
temperature
increases

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Radiations and temperatures are the two main parameters that
modify the characteristics of PV cells. These parameters should be
carefully considered when setting up solar panels.
The influence of Series Resistances
Series resistance in a solar cell has three causes: firstly, the
movement of current through the emitter and base of the solar cell;
secondly, the contact resistance between the metal contact and the
silicon; and finally the resistance of the top and rear metal contacts. The
main impact of series resistance is to reduce the fill factor, although
excessively high values may also reduce the short-circuit current.
Figure 10 : Schematic of a solar cell with series resistance.
For the simulation, I increase the value of Rs :
Rs
2.5 * Rs
3.5 * Rs
20 * Rs

ZOUHIR ISMAIL 20
Figure 11 : Influence of Serie Resistance
The series resistance react on the slope of the characteristic I-V in the
area where PV generator operates as a voltage generator. It does not affect
the open-circuit voltage, and when R is too high, it decreases the value of
curent short-circuit.
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
Voltage (V)
Current(A)
Influence on Rs
rs
2.5rs
3.5rs
20rs

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The influence of Shunt Resistances
Significant power losses caused by the presence of a shunt
resistance, RSH, are typically due to manufacturing defects, rather than
poor solar cell design. Low shunt resistance causes power losses in solar
cells by providing an alternate current path for the light-generated current.
Such a diversion reduces the amount of current flowing through the solar
cell junction and reduces the voltage from the solar cell. The effect of a
shunt resistance is particularly severe at low light levels, since there will
be less light-generated current. The loss of this current to the shunt
therefore has a larger impact. In addition, at lower voltages where the
effective resistance of the solar cell is high, the impact of a resistance in
parallel is large.
Figure 14 : Circuit diagram of a solar cell including the shunt resistance.

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Figure 15 : Influence of Shunt Resistance
In general, the shunt resistance is elevated, its effect is noticed
especially in the part of the current generation.
The effect of the shunt resistor on the curve results in a slight
decrease in the open circuit voltage and an increase of the slope of the
curve in the cell area corresponding to operation as a current source.
0 5 10 15 20 25
0
0.5
1
1.5
2
2.5
3
3.5
4
Voltage (V)
Current(A)
Influence of Rsh
1000 Ohms
150 Ohms
20 Ohms

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From Modules to Arrays
A PV module consists of a number of interconnected solar cells
(typically 36 connected in series) encapsulated into a single, long-lasting,
stable unit.
Serie/Parallel Association  When highpower is needed
0 5 10 15 20 25 30 35 40 45
0
1
2
3
4
5
6
7
8
Current(A)
Voltage (V)
V-I curves for serie/parallel association
1 solar panel
4 solar panels (serie/parallel)

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Association in serie  at any given current (which ﬂows through each of
themodules), the total voltage is just the sum of the individual module voltages
Matlab Simulation
0 5 10 15 20 25 30 35 40 45
0
0.5
1
1.5
2
2.5
3
3.5
4
Voltage (V)
Current(A)
V-I curves for serie association
1 Solar panel
2 solar panels

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Association in parallel  at any given voltage, the I–V curve of the parallel
combination is just the sum of the individual module currents at that voltage.
0 5 10 15 20 25
0
1
2
3
4
5
6
7
8
Voltage (V)
Current(A)
I-V cures for parallel association
1 Solar panel
2 solar panels

ZOUHIR ISMAIL 26
How to maximise Energy
Solar cells have a complex relationship between solar irradiation,
temperature and total resistance that produces a non-linear output
efficiency which can be analyzed based on the I-V curve.
To get the maximum possible power from one or more photovoltaic
devices, typically solar panels though optical power transmission systems
can benefit from similar technology we use a technique called : Maximum
power point tracking (MPPT)
Maximum power point trackers may implement different algorithms
and switch between them based on the operating conditions of the
array and one of this algorithm :
Perturb and Observe
The concept behind the “perturb and observe” method is to modify the
operating voltage or current of the photovoltaic panel until you obtain
maximum power from it. For example, if increasing the voltage to a cell
increases the power output of a cell, the system increases the operating
voltage until the power output begins to decrease. Once this happens, the
voltage is decreased to get back to the maximum power output value. This
process continues until the maximum power point is reached. Thus, the
power output value oscillates around a maximum power value until it
stabilizes. Perturb and observe is the most commonly used MPPT method
due to its ease of implementation.

ZOUHIR ISMAIL 27
Figure 15 : Algorithm of P&O method
One of the major drawbacks of the perturb and observe method is that
the power obtained oscillates around the maximum power point in
steady state operation. Also, this algorithm can track in the wrong
direction under rapidly varying irradiance levels.

ZOUHIR ISMAIL 28
Conclusion
The work presented in this report concerns the modeling of a
photovoltaic panel. The study is based on the impact of various
parameters on I (V) and P (V) characteristics of a system of photovoltaic
panels.
The solar cell acts as a generator:
- Current generator
- Voltage generator
The characteristic of I (V) is influenced by many parameters:
temperatures, radiations, serie resistance, shunt resistance.
I found from the result that in the association of cells in series, for a
constant current, the voltage increases, and in association of cells in
parallel, for a constant voltage, the current increases.
In another phase, I was looking for the maximum power that can be
extracted from a photovoltaic panel. Indeed, the production of electric
energy using a photovoltaic panel has an optimum operating point. This
optimum point has the characteristic to change with the temperature and
illumination.
I want to thank Roberto Villafafila for monitoring and assistance has given me and the people
who work in international relations office who gave me this chance to live a great experience,
an experience I'd retried the coming years.

ZOUHIR ISMAIL 29
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ZOUHIR ISMAIL 30
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