Analysis of shading pattern of solar panels

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 02 | Feb-2014, Available @ http://www.ijret.org 594
ANALYSIS OF SHADING PATTERN OF SOLAR PANELS
Gargi Sarkar1
, Kanchan Bakade2
1
Student, Electronics and Telecommunication, NMIMS MPSTME, Maharashtra, INDIA
2
Assistant Professor, Electronics and Telecommunication, NMIMS MPSTME, Maharashtra, INDIA
Abstract
Abstract –The shading pattern of a Solar Panel if analyzed helps to improve the performance of a Solar panel. Shades on top of a
Solar Panel are one of the major factors which causes disturbance on a solar panel. This paper helps analyze the shading on a
solar panel which is caused by steady clouds. This may help to increase the efficiency of a solar panel. Various methods of Image
processing technique is used to get the desired output. Those methods include techniques like median filtering and various
morphological functions like usage of structuring element which gives the desired output. The problem of Boundary Estimation of
a shading patter on a solar panel is addressed. Short-time shading and lightning is not at all useful for solar power plant. If the
solar panel is shaded then proper measures have to be taken to keep the efficiency intact else there would be a serious loss in the
amount of current generated with the help of a solar panel. Here the pixel values are measured and thus the exact numbers of
dark and bright pixels are calculated and even the pixel values are reconfigurated to get the correct boundary estimation. The
bypass diode is used to bypass the shaded area on the panel, which in turn helps to increase the efficiency of a solar panel by a
significant amount. This method takes care of processing all kinds of shade on the solar panel from whatever source the shade is
generated from.This concept can be taken further to analyse the various other parameters for effective operation.
Key Words: Cloud; Solar power plant; Partial shading; Image processing; Efficiency; Bypass diode
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1. INTRODUCTION
The use of solar energy dates from antiquity. Between 1907
and 1913 the American engineer F. Shumman developed
solar driven hydraulic pumps. With the increasing
availability of low-cost oil and natural gas, interest in solar
energy for power production is needed. Much amount of
work was not done on solar energy from 1915-1950, but the
interest was initiated by the American Association for the
Advancement of Science at Washington DC in 1949 in the
section of “future energy sources”. At that time the future
potentials as well as the economic problems for solar power
was discussed. The wide spread discussion of solar energy
was done only after the oil-embargo that occurred in
1973[5].
The performance of a PV array can be affected by various
factors, such as temperature, solar isolation, solar angel of
incidence, shading, inclination, angel of panel and array
configuration. The power output of a solar panel depends on
the solar intensity and angel of a PV array. A PV array can
get shaded or partially shaded by various factors such as
trees, clouds, buildings etc [2].Thus monitoring of an PV
array needs to be done for maximum output of a solar panel.
This method can be used for the boundary estimation of
anything which would require an exact estimation and pixel
count. After this boundary estimation method is compiled
with, the solar panel could be attached with bypass diode to
get the good results of the amount of current produced.
Some researchers used to use blocking diode on a solar
panel to stop the current from getting into an infinite loop in
the circuit itself, but the blocking diode itself does not help
to safeguard the solar cells or provide any protection to
reduce the output current according to the shading patterns
on the solar panels.
Thus bypass diodes are used which are far more useful than
a blocking diode and provides complete safety against any
fluctuations which may cause the peak voltage to change in
a particular situation.
The maximum current obtained from an solar panels or an
array does not only matter only on the size (the number of
panels on an array) but also how the configurations
(connections of the panels) and the way the shading pattern
is handled by a solar panel. Thus all the factors have to be
taken care for the increase in the efficiency.
2. STIMULATION PROCEDURE
The reason for using MATLAB is that it is available in most
academic, research, and industrial organizations and
considered useful for several engineering disciplines. It
provides several features that can be used to simulate highly

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complex systems, electronic and power electronic circuits
and
systems and distributed generation power systems. To get
the input image a simple camera is used with a good pixel
count, so the clarity of the image remains intact.[1]
Figure 1- Flow Chart of the Stimulation Procedure
2.1 Conversion of colored image to binary image
Here a simple predefined function in MATLAB is used
for the conversion of colored image to binary image.
2.2 Application of median filter on the binary
image
This is a nonlinear digital filtering technique which is
used to reduce and remove the noise (disturbances in an
image).This stage usually aids to get better results in the
following procedures to be performed. In this application
method a window would be applied on the entire image.
The pixel value in the entire image is taken into
consideration and the median value of it is the intensity
value of the output pixel.
2.3 Application of structuring element
This is a set of non linear functions usually related to
shape or morphology of an image. The morphological
functions do not deal with the intensity value of an
image. Here the relative positions of the pixel values are
dealt with according to the neighborhood pixels.
In this procedure another kind of window is applied
all over the image. These windows are called structuring
elements and these come in various shape. User uses
whichever shape according to the usage.
For example, this code creates a flat, diamond-shaped
structuring element.
Se = strel ('diamond',3)…………………………….1
Decomposition: 3 STREL objects containing a total of
13 neighbours
Neighbourhood:-
0 0 0 1 0 0 0
0 0 1 1 1 0 0
0 1 1 1 1 1 0
1 1 1 1 1 1 1
0 1 1 1 1 1 0
0 0 1 1 1 0 0
0 0 0 1 0 0 0
Comparisons of the structuring element along with the
neighboring pixels are done and thus the approximate
shape of the object in the image can be identified
The structuring elements work better in a binary
image because the structuring element is usually a
window of different shapes having intensity value of the
image as either zero or one.
Here the structuring element of “disk” is being used here.
Figure 2- Structuring Element having the shape “square”.
2.4 . Application of Erosion.
Morphological operations include the application of
erosion and dilation too.Erosion is used to remove pixels
from the boundary of an image object,detected earlier in
the procedure.
Erosion will occur according to the neighbourhood
pixels of an image. Erosion might cause the boundary

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pixels of an image to either go dark or light according to
the neighbourhood pixel intensity value[10]
Figure 3-Original image of a flower
Figure 4-Eroded image of a flower
2.5.OUTPUT IMAGE
The ouput image obtained would be used to differentiate
between the dark area and the light area and thus the
bypass diode would work according to amount of light
area available on the solar panel[3]
This way the solar cells which maybe shaded due to any
obstruction may be easily byppassed with the help of
bypass diode.
This analysis would help us to get the current with
minimanl loss and thus a significant increase in
efficiency.
Figure 5-Original Picture of the Clouds
Figure 6-Boundary Estimation done by the algorithm used
3 .SOLAR CELLS
Photovoltaic is a method to generate electrical energy by
converting solar energy into direct current electricity using
semiconductors which exhibit photovoltaic effect.
Materials used for manufacturing of photovoltaic’s are
monocrystalline silicon, polycrystalline silicon, amorphous
silicon, cadmium telluride, and copper indium gallium
selenide/sulfide.
Photovoltaic is used for power generation by including
multiple solar cells together and then forming an array of
solar cells.[4]
The operation of a photovoltaic (PV) cell requires 3 basic
attributes: 1.absorption of light, generating either electron
hole pair or exitrons.2.separation of charge carriers of
opposite types.3.The separate extraction of those carriers to
an external circuit.

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Photovoltaic’s is the direct conversion of light into
electricity at the atomic level. Some materials exhibit a
property known as the photoelectric effect that causes them
to absorb photons of light and release electrons. When these
free electrons are captured, an electric current result that can
be used as electricity [12].
Figure 7-Forming of a PV array
Figure 8-Working Of an PV array
4.BYPASS DIODE
Bypass diode are used on a solar panel for two reasons
i) To provide improved safety to the panels
ii) To help improve the performance and thus improve the
efficiency of the Solar panel[11].
The primary reason that bypass diodes are used is to prevent
the operating voltage of the module and the series string
from getting too low if a panel has any partial shading. The
shaded portion of the panel is, as the name suggests,
bypassed [7].
A partially shaded SOLAR panel will always try to get the
maximum output. Under shaded conditions also, a Solar
Panel will always try and give maximum output, which
causes the solar panel to give more output then possible,
which causes loss of current and also increases the circuit
temperature. Eventually causes the life of the circuit to
reduce and also reduced outputs.
Figure 9-Bypass diode in normal mode and in bypass
mode
So the bypass diode helps to reduce all the disadvantages of
the solar panels and hence improve the overall output and
thus improve efficiency.
The bypass diodes which are attached to the solar cell are
usually at a reverse bias mode, thus allowing current to
completely pass through it. The moment even a small
percentage of the solar cell gets shaded due to any reason,
the bypass diode switches from reverse bias to forward bias
thus allowing the current to completely bypass the shaded
cells.
This may cause the output voltage to reduce ,but atleast the
effects of shaded cells causing damage to the whole array
will significantly reduce[6-8]
Figure 10-Output Characteristics of the solar panel with
and without bypass diode.

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A single Bypass diode might be used for multiple solar cells
together. That is usually done because a single bypass diode
for every single cell would not be feasible because of the
increased cost[9].
5.TEST RESULTS
Figure 11- Original picture of the solar panel
Figure 12-Boundary estimation done to the original
picture of a solar panel.
6. CONCLUSIONS
This procedure consists of separating the dark pixels
from the bright pixels and giving an exact count of the
number of dark pixels and bright pixels. It is very important
to understand the MATLAB program used to differentiate
the dark and bright area. This procedure has a step wise
routine which includes various methods to convert the binary
image to complete black and white along with the pixel
count.
After the boundary estimation is done, a bypass diode can be
used to bypass the solar cells which are partially shaded and
thus the efficiency of a solar panel can be improved
ACKNOWLEDGEMENT
Gargi Sarkar says thanks to her guide Kanchan Bakade
and S.P.Duttagupta. A special thanks to Ashwini and
Bhavani Patnaik because of their helpful insights and
valuable advice.
Would like to say thanks to my classmates for their help
and advice. A very special thanks to my friends and family
for their unconditioned support and help.
REFERENCES
[1]. Hideaki Obane, Student Member, IEEE, Keiichi
Okajima, Member, IEEE, Takashi Oozeki, Member,
IEEE,and Takafumi Ishii “PV System With Reconnection to
Improve Output Under Nonuniform Illumination” IEEE
Journal (Volume:2 , Issuse 3),JULY 2012.
[2]. B.Patnaik, P.Sharma, E.Trimurthulu1, S.P.Duttagupta
and V.Agarwal Department of Electrical Engineering, IIT-
Bombay, Mumbai, India“Reconfiguration Strategy For
Optimization Of Solar Photovoltaic Array Under Non-
Uniform Illumination Conditions”IEEE Journal,JUNE 2011.
[3]. Mario A. T. Figueiredo, Jose M. N. Leitao ,Instituto de
Telecomunicaqdes and DEEC,Instituto Superior Tbcnico
Lisboa Codex,Anil.k.Jain,department of computer
science,Michigan University PORTUGAL“Adaptive B-
Splines and Boundary Estimation” IEEE Computer Society
conference,June 1997.
[4]. Lian Peng,Hua Fang, Ming Tang Department of
Electronic Information and Control Engineering Guangxi
University of Technology,Liuzhou, 545006, China “Solar
power wireless monitoring system based on ARM7”
Artificial Intelligence, Management Science and Electronic
Commerce (AIMSEC), 2011 2nd International Conference
on AUG 2011.
[5]. Ben-Gurion University of the Negev Faculty of
Engineering Sciences Department of Nuclear
Engineering.“Real-Time Clouds Motion Analysis And
Possibility Of Its Application To Solar Engineering” by
Roman Palatnik.
[6]. Hiren Patel and Vivek Agarwal. MATLAB-Based
Modeling to Study the Effects of Partial Shading on PV
Array Characteristics. IEEE Transactions On Energy
Conversion, VOL. 23, NO. 1, MARCH 2008.
[7].http://www.civicsolar.com/forum/9824/what-bypass-
diode“Bypass Diode”
[8].http://solarprofessional.com/articles/design-
installation/q-a-bypass-diodes-improve-system-
performance-and-safety “Bypass Diode”
[9].http://pveducation.org/pvcdrom/modules/bypass-
diodes“Working Of Bypass Diode”.

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[10] Desikachari Nadadur and Robert M. Haralick, Fellow,
IEEE- “Recursive Binary Dilation and Erosion Using
Digital Line Structuring Elements in Arbitrary
Orientations”, IEEE TRANSACTIONS ON IMAGE
PROCESSING, VOL. 9, NO. 5, MAY 2000
[11] Atsushi Kajihara,Gunma Industrial Technology Center
Kamesatotyou 884-1 Maebashi, Tetsumi Harakawa
Maebashi Institute of Technology Kamisadorityou 460-
1Maebashi, “Model of Photovoltaic Cell Circuits under
Partial Shading”, 2005 IEEE TRANSACTIONS .
[12] http://science1.nasa.gov/science-news/science-at-
nasa/2002/solarcells ,”WORKING OF SOLAR CELLS”
BIOGRAPHIES
Gargi Sarkar completed her Btech in
Electronics from Mukesh Patel School
of Technology Management and
Engineering, affiliated to NMIMS
University in 2012.She has continued to
study for her MTECH degree and is
currently pursuing her master’s from
Mukesh Patel School of Technology
and Management and would be
graduating by 2014.
Kanchan Bakade is currently working
as an Assistant Professor in Mukesh
Patel School of Technology
Management and Engineering ,
affiliated to NMIMS University since
from 2008.She has done her MTECH
from IIT Roorkee in RF and
Microwaves .Her area of interest are
Wireless Communication ,Satellite
Communication and RF.

Analysis of shading pattern of solar panels

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Analysis of shading pattern of solar panels