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International Journal of Energy and Power Engineering
2015; 4(4): 227-231
Published online July 31, 2015 (http://www.sciencepublishinggroup.com/j/ijepe)
doi: 10.11648/j.ijepe.20150404.15
ISSN: 2326-957X (Print); ISSN: 2326-960X (Online)
Experimental Investigation of the Effect of Tilt Angle on the
Dust Photovoltaic Module
Tariku Negash, Tassew Tadiwose
Department of Mechanical Engineering, Debre Markos University, Debre Markos, Ethiopia
Email address:
thismuch@ymail.com (T. Negash)
To cite this article:
Tariku Negash, Tassew Tadiwose. Experimental Investigation of the Effect of Tilt Angle on the Dust Photovoltaic Module. International
Journal of Energy and Power Engineering. Vol. 4, No. 4, 2015, pp. 227-231. doi: 10.11648/j.ijepe.20150404.15
Abstract:
This research paper investigate the effect of tilt angle on the accumulation of dust PV module on energy
production and presents a module for predicting soiling losses for eight different tilt angle (0
0
, 5
0
,11.6
0
,15
0
,21.5
0
,25
0
,30
0
and
35
0
) including the latitude of Bahir Dar city (11.6
0
) and 21.5
0
tilt angle of 10Kw hybrid solar power plant PV module which is
currently installed in Bahir Dar university. The study has shown that during the experimental investigation period there was
total loss of insolation due to soiling was 32.32% and 4.8KWh/m
2
total energy has been absorbed at 0° tilt angle. Modules at
11.6° and 21.5° tilt angles the total insolation loss were 21.92% and 16.78% respectively since it has been covered with dust.
Approximately both modules have 5.3KWh/m
2
of energy has been absorbed. However, at 25
0
tilt angle had a least insolation
loss and largest amount of energy absorbed when compared to the remaining seven different tilt angles; it has only 10.77% of
insolation loss and 5.7KWh/m
2
of energy has been absorbed. The remaining tilt angles of 5°, 15°, 30° and 35° the total
insolation loss were 25.45%, 19.08%, 14.20%, and 12.54% respectively, and also the total energy of 5.08KWh/m
2
,
5.52KWh/m
2
, 5.2KWh/m
2
and 4.59 KWh/m
2
were absorbed respectively. Thus, soiling effect has present at any tilt angle, but
the magnitude is evident: the flatter the solar module is placed the more energy it will lose.
Keywords:
Solar PV, Soiling, Tilt Angle, Insolation Loss
1. Introduction
A solar Photovoltaic is a method of generating electrical
power by converting the solar radiation into direct current
electricity using semiconductors that exhibit the photovoltaic
effect [1].Photovoltaic system installation has played a big
role in renewable energy because PV systems are pollution
free, economically reliable for long-term operation and
secure energy source. The major obstruction of PV
technology is its high capital costs comparedto conventional
energy sources and also it is the more widely used
technology all over the world; there is 100GW of solar PV
now installed in our world [2, 3].
It is estimated that a total of some 5.3MWp of PV is now
in use in Ethiopia.In April 2012 Ethiopia has established the
first Polycrystalline solar PV module assembly plant with the
cooperation of SKY Energy International, Metals and
Engineering Corporation (METEC) and an Ethiopian state
enterprise. The plant would expected to achieve 20% of
Ethiopian power capacity coming from solar energy within
the next five years including 3Million solar home systems
distribution plan and may also be exported to a neighboring
country [4]. Performance of these solar-photovoltaic (PV)
system not only depends on its basic electrical characteristics;
maximum power, tolerance rated value of percentage,
maximum power voltage, maximum power current, open-
circuit voltage (Voc), short-circuit current (Isc), maximum
system voltage, but also is negatively influenced by several
obstacles such as ambient temperature, relative humidity,
dust storms and suspension in air, shading, global solar
radiation intensity, spectrum and angle of irradiance [5].The
radiation received by cells in the PV module is lower than
radiation reaching the module surface. The main causes of
these energy difference are dirt accumulation on the surface
of the modules, reflection and absorption losses by the
materials covering the cells and the tilt angle of the PV
module. To better understand the effect of tilt angle on
soiling, one has to know how it affects the current of the PV
modules as it is directly proportional to the irradiance
reaching the solar cells. The incident irradiance on PV cells
228 Tariku Negash and Tassew Tadiwose: Experimental Investigation of the Effect of Tilt Angle on the Dust Photovoltaic Module
inside a PVmodule and the operating temperature of PV cells
primarily dictate the power output of module. On a dual axis
tracker, when module surface and the incident light rays are
perpendicular to each other, the power output will be the
highest. Therefore, this study aims to provide a better
understanding of the extent at which tilt angle affects the dust,
and hence the performance, of PV modules.
2.
Methodology
2.1. Description of the Study and Set up of the PV Module
Bahir Dar city is located at latitude of 11°36′N and
longitude of 37°23′E respectively, and an elevation of 1,840
meters above sea level. [6]. Fig 1 shows four modules that,
two modules were dirt and tilt different two angles and the
other two modules were clean by washing water and
detergent and tilt similar to the two dust modules.And also
due to the location of Bahir Dar those four modules face
towards south by using compass, since more near to the
equator and the system were installed at a minimum height of
1.5 meter from the ground.
Fig. 1. Clean and dust PV module at 21.50 and 250 tilt angle.
2.2. Calibration and Linearitycheck of the PV Module
The international Electronic Commissions (IEC) 60904-10
standard describes the procedures utilized for determination
of the degree of linearity of any photovoltaic device
parameter in relation to a test parameter. A device is linear
when it meets the requirements of IECat section 7.3, which is
stated as follows. When some device is claimed to be linear,
the applicable range of irradiance, voltage, temperatures, or
other necessary conditions should also be stated. The
requirements for the acceptable limits of non-linearity
(variation) are:
a. For the curve of short-circuit current versus irradiance,
the maximum deviation from linearity should not
exceed 2 %.
b. For the curve of open-circuit voltage versus the
irradiance logarithm, the maximum deviation from
linearity should not exceed 5 %.
c. If the temperature coefficient of short circuit current
doesn’t exceed 0.1 %/°K, the device can be regarded as
linear in relation to this parameter [7, 8].
During the outdoor experiment, the temperature and the
output voltage of all the modules were recorded
simultaneously every 15 minute using a multi-meter and a
digital thermometer. As well as the irradiance and the short
circuit current flow that analysed the linearity of the
experiment.
2.3. Properties of Dust Based on the Laboratory Testing
Due to small diameter and less density of dust, can be
blows in the environment with natural force. This dust
diameter that flows on Bahir Dar city that estimatesaround
0.5-150 microns [9]. However it will vary from place to place.
Thus, the average particle diameter is used for this
experiment by sieving the dust with diameter of 0.075mm
and it distributed 25 gram amount of dust to each tilt angle of
PV module to make dirty.
2.4. Hydrometer Analysis: Composition of the Finer Dust
Particles
According to ASTM D 422 claysare defined as particles
diameter of between 0.075mm to 0.005mm and silt particles
less than 0.005mm in diameter. Thus, from the 50 gram
sample test of dust silt and clay amount were 63.62% and
36.38% respectively. Fig 2 shows that percentage of finer
versus grain size diameter (mm).
Fig. 2. Hydrometer analysis of percentage of passing versus diameter of
particle size.
2.5. Experimental Set up and Data Collecting of Wind
Speed
The vantage pro 2 instrument as shown below on Fig 3
that has been used to measure the weather condition of the
environment (solar radiation, rainfall, etc). But, for this
experiment it is only used to measure the wind speed of the
environment close to the PV module installed. The
instrument has been installed 2.5m away from the PV and at
an average height of 1.7m. The wind data has been stored in
the data logger of the wireless vantage pro 2 (Fig 4) devices
and export the record data by connecting USB cable to the
International Journal of Energy and Power Engineering 2015; 4(4): 227-231 229
personal computer. The wind speed and direction data were
record for eight days within 30 minutes time interval. During
this time the tilt angles are changed in two days interval.
Fig. 3. Set up of vantage pro2 with clean and dusty PV module.
Fig. 4. Wireless data logger.
2.6. Data Collecting System and Period of Experiment
On this outdoor experiment, a systematic series of
measurements were conducted for several time periods
corresponding for eight different tilt angles on soiling and
clean PV. The experimental data collection was carried out,
for 32 days (September 12 to October 16/2013) excluding the
holiday and uncomfortable weather condition. Through those
days the experiment was conducted before and after rainfall
condition. Particularly, the performance of the clean pair
panel was compared with the corresponding of the soiled pair
panels under different tilt angle for four days each. The
experiment was mostly measured under clear sky, and
different atmospheric conditions (e.g. ambient temperature,
humidity, wind velocity etc.), for 1 hour there were 4
measurements recorded (approximately one measurement per
15 minute). During the recording procedure the values of the
current and voltage of the PV-panels were recorded along
with the values of the ambient temperature and solar
radiation (W/m2). The loss of energy conversion efficiency
can be calculated using the equation (1).
(%) =
,
,
,
(1)
Where: -
,
: Energy of clean PV,
,
: Energy of
dust PV and,
(%): Percentile insolation loss.
3.
Experimental Results Analysis and
Discussion
3.1. Effect of Tilt Angle Before Rainfall
As shown in Fig 5, as the tilt angles becomes increasingly
from the horizontal surface, the insolation loss or soiling
effect increases. Energy losses was varied from 31.24% to
38.40% with 0
0
title angle (horizontal) solar modules. For the
latitude of 11.6° energy loss is not as high, but still varied up
to 24.68%, depending on the daylight conditions, the amount
of dust it has been accumulating soil before rainfall. The 25
0
tilt angle of the PV module highly decreased the insolation
loss from 17.56% to 13.14% than others of tilt angles and it
absorbed high amount of energy through 4 days measurement,
1518.80 Wh/m
2
and 1298.03 Wh/m
2
on the clean and soiled
PV module respectively. Fig. 6 illustrated that unexpected
increasing of insolation losses at 30
0
and 35
0
tilt angleswere
conducted since there was Agro-stone dust particles are
blowing on the environment near to the experiment site. For
angle of 0
0
, 5
0
and 11.6
0
energy harness is very low but they
have large insolation losses.
Fig. 5. Average Daily Insolation loss for each tilt angle: Sept12-28/2013.
Fig. 6. Total Daily Energy for clean and unclean solar PV before rainfall.
230 Tariku Negash and Tassew Tadiwose: Experimental Investigation of the Effect of Tilt Angle on the Dust Photovoltaic Module
3.2. Effect of Tilt Angle After Rainfall
During this study from Sept 29- Oct16/2013, there was
rainfall from 0.2mm to 34.5mm based on Bahir Dar city
weather station data, and it did effectively clean the solar
modules from dirt accumulation. However, when there was
only 1mm of rainfall or less and no wind, it made the soiling
effect much worse. Rainfall makes a difference, because rain
can act to clean the modules.
As shown on Fig. 7 and 8, the insolation losses decreased
linearly up to the 25
0
of tilt angle. Within 12.9mm average
rainfall the drop energy a conversion loss for both the latitude
(11.6
0
) and 15
0
tilt angle were decreasedfrom 19.24% to 16.83
% and from 15.89% to 13.67% through 4 day incessantly
measurement respectively. However, with in 8.0mm rain fall
from Oct.6 to Oct.9 for 21.5
0
and 25
0
tilt angle the energy
losses were decreased from 11.26% to 9.67% and 7.17% to
5.61% respectively. Beside this, the drop of energy loss are
low at 30
0
and 35
0
of tilt angle even if the tilt angle is high.
This illustrates that the soiling effect on PV modules needs
more work for long period of time that helps to quantify its
effect.However, the rainfall that clean the dust PV modules,
still there are insolation loss particularly at small tilt angles.
Fig. 7. Average Daily Insolation losses for each tilt angle: Sept.29-Oct.
16/2013.
Fig. 8. Total Daily Energy absorbed for clean and unclean solar PV before
rainfall.
3.3. Effect of Tit Angle Both Before and After Rainfall
To compare the insolation losses before and after the
rainfall, the averages were calculated four days each for
before and after the rainfall. Fig. 9bars represent a percentage
loss of insolation between clean and soiled solar PV module
before and after rainfall. The percentage differences of the
insolation loss of before and after rainfall were: 2.80% and
11.18% at 0
0
and 21.5
0
tilt angle: that is the least and the
highest value out of the entire tilt angle respectively.
Fig. 9. SoilingComparisononbeforeandafterrainfall from Sept.12/2013-
Oct16/2013.
3.4. Effects of Wind Load on a Dust Pv Module
As illustrated the above fig. 10the wind load has less effect
at 0
0
and 5
0
tilt angle to clean the dust PV module due to this
there were least energy absorbed difference are shown. As
increased the tilt angle the wind load has a power to blown
the dust from PV module. Likewise, the amount of the
energy absorbed increase as increase number of days.
However, the two days variation of energy absorbed were
large at 30
0
and 35
0
tilt angle the amount of energy absorbed
as much as expected. This is due to large tilt angle of the dust
PV module.
Fig. 10. Effect of wind load on a dust PV module.
3.5. Selected Tilt Angles Comparison Before and After
Rainfall
Three different angles have been selected to compare the
insolation loss at different rainfall amount of each tilt angle,
International Journal of Energy and Power Engineering 2015; 4(4): 227-231 231
for instance: horizontal surface (0
0
), latitude of Bahir Dar city
(11.6
0
), and the 10KW hybrid solar power plant of tilt angle
in Bahira Dar University (21.5
0
). On Fig. 11 the insolation
loss can be calculated by interpolated the measured rainfall
data between upper and lower value of the insolation loss.
This helps to quantify the direct relationship of amount of
rainfall to the insolation loss. The insolation loss for each tilt
angle at the 0 mm of rainfall was calculated the average total
insolation loss of before rainfall. Thus at zero millimeter of
rainfall the insolation loss was 33.59%, 25.29% and 22.21%
at 0°, 11.6° and 21.5° tilt angle. On the day six the insolation
loss was increased linearly at 11.6° and 21.5° during the 2
mm of rainfall. However, the insolation loss was decreased
highly at the maximum of the rainfall of 16 mm that was
29.62%, 17.21% and 9.73% at 0°, 11.6° and 21.5° tilt angle
respectively.
Fig. 11. Daily Interpolated Insolation Loss at different estimated rainfall.
4.
Conclusion
The outdoor experimental result reveals that, for horizontal
surface (0
0
) tilt angle, there was a total loss of 32.32% due to
dust and around 4.8KWh/m
2
total energy absorbed. Likewise
the study showed that, for 11.6
0
and 21.5
0
tilt angles the total
insolation losses were 21.92% and 16.78% respectively
because of dust, but they have almost similar energy gained
around 5.3KWh/m
2
. This implied that the 11.6
0
and 21.5
0
tilt
angles had a lower insolation loss than the horizontal surface
tilt angle but large amount of energy was absorbed. However,
at 25
0
tilt angle had a least insolation loss and largest amount
of energy absorbed when compared to the remaining seven
different tilt angles; it was only 10.77% of insolation loss and
5.7KWh/m
2
of energy was absorbed. The remaining tilt angle
wherefor 5°, 15°, 30° and 35° the total insolation loss were
25.45%, 19.08%, 14.20%, and 12.54% and also the total
energy absorbed were 5.08KWh/m
2
, 5.52KWh/m
2
,
5.2KWh/m
2
and 4.59 KWh/m
2
respectively. Thus, the dust
effect has been present at any angle, but the magnitude is
varied: more energy will lose, when the solar modules flatter
angle. Nevertheless, the effect of tilt angle on the dust is
depending on the environmental condition.
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