International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:15 No:01
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Effect of Weather Conditions on the Energy and
Exergy Efficiencies of Mono-crystalline Photovoltaic
Module
Nouar Aoun1, 2,*, Boukheit Nahman2, Rachid Chenni3 and Kada Bouchouicha1.
1
Research Unit in Renewable Energies in the Saharan Medium, URERMS, P.O. BOX 478, Development Centre of Renewable
Energies, CDER 01000, Adrar, Algeria.
2
Department of physics, University of Constantine 1, Constantine 25000, Algeria.
3
Department of Electrical Engineering, University of Constantine 1, Constantine 25000, Algeria.
E-mail : [email protected]
Abstract-- This article analyzes and modeling the efficiencies of
the energy, the exergy and the power conversion of monocrystalline photovoltaic module under outdoor weather
conditions in Adrar, Algeria (0.18 W, 27.82 N).The experimental
data sets are determined for typical clear and cloudy days of
March 21 to 23, 2013. The effect of solar radiation, ambient
temperature and wind speed on the exergy efficiency is also
analyzed. It is observed that the exergy efficiencies vary rapidly
throughout the day. However, with an increase of wind speed and
ambient temperature there is a decrease in the exergy efficiency.
On the other hand, the exergy efficiency increases with an
increase in solar radiation.
Index Term-- energy; power energy; exergy; efficiency;
photovoltaic
INTRODUCTION
Due to the high damaging effects of the pollution and the
carbon emission from power plants on the environment and
the life on earth, many countries have officially signed the
Kyoto protocol to date in order to reduce this pollution. One
of the best solutions is to use the renewable sources of energy
(i.e., Photovoltaic, solar-thermal, wind turbines or
geothermal). Photovoltaic systems can meet most of the
world's electricity demand, its advantages are : the direct
conversion of solar energy into electric power, non-polluting,
no mechanical moving parts, silence and the energy source
from the sun used to liberate the pair electron/hole is
free,…etc.
The efficiency of a photovoltaic system strongly depends on
the outdoor weather conditions such as ambient temperature,
solar radiation, humidity, wind speed…etc.
The evaluation of the performance of photovoltaic modules is
the most important study; it provides us the energy and exergy
efficiency given by the system.
The energy efficiency of the system is calculated according to
the first law of thermodynamics, and the exergy analysis is
based on the second law of thermodynamics which is the
maximum useful work that can be obtained from a system
every time [1]-[2]- [3].
In literature there are many researches which studing the
energy and exergy phenomenon from different systems such:

PV/T water collectors [4]-[5].

PV/T air collectors [6] - [7].

Photovoltaic modules [8]-[9].
In Ref. [10] two different PVT water collectors are tested, one
with a tube-and-sheet, and the second integrated with a
parallel-plate. It’s found that the average efficiency of the
PVT modules is about 0.4% higher than the normal PV
module.
Numerical and experimental validations of PV/T water
collector, with and without glazing cover are studied and
compared in [11]. It is found that the glazed collector
efficiency is better than the unglazed collector.
Ref. [12] presents a mathematical model for single and twice
glass cover of PVT air collector with natural convection flow.
Two different geometrical shapes in the middle of the air
channel are compared. It found that the collectors with
triangular shapes are more efficient than those with
rectangular.
In Ref. [13] a comparative energy, exergy and carbon credit
analysis of different type PVT air collector are studied. It is
found that the annual exergy efficiency of unglazed and
glazed PVT tiles air collector is higher by 9.6% and 53.8% as
compared to conventional PVT air collector, respectively.
In Ref. [14] a new approach to determine exergy efficiency of
photovoltaic system is proposed and compared with exergy
efficiency proposed by [15]. Exergy efficiency of the new
approach showed lower values than in [15].
In Ref. [16] the energy and the exergy efficiencies of
photovoltaic systems are calculated according to the first and
second law of thermodynamics. It is found that the energy and
exergy efficiencies vary from a minimum of 33% to a
maximum of 45% and from a minimum of 7.8% to a
maximum of 13.8%, respectively.
The purpose of this paper is to present and compare the
efficiencies of power conversion, energy and exergy in
different weather condition represented by three days of
March i.e., cloudy day (21 March 2013), and clear days
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(March 22-23, 2013). This paper also provides the effect of
ambient temperature, radiation solar and wind speed based on
experimental data.
And the energy efficiency can be defined as below:
Photovoltaic efficiencies
Test Data Sets
The exergy analysis is the maximum quantity of work that can
be created by a system. Moreover, it is considered as the
losses related to the system [17]. Equation (1) presents the
exergy of photovoltaic module, where the first term represents
the electrical exergy, and the second the thermal exergy terms
of the photovoltaic panel. Moreover, the negative sign
represents the heat loss [16].
The outdoor experimental testing data sets for a typical two
days (21st-22nd March 2013) in Adrar (0.18 W, 27.82 N),
Algeria, are used to measure energy efficiency, and exergy
efficiency. Mono-crystalline silicon solar cell, i.e., S-Energy
SMXXXMH1Series PV module was experimentally selected
to testing data sets. The PV panel was tilted at an angle equal
to 36.8°, opposite the south. The data sets included solar
irradiation, open-circuit voltage, short-circuit current,
maximum power point (Ip, Vp and Pp), cell temperature,
ambient temperature, and wind speed. The experimental
outdoor data is performed as: The meteorological radiation is
measured with a CM11 type Kipp & Zonen pyranometer. The
IV photovoltaic characteristics (Isc, Voc, Ip, Vp, IV and PV
curves) were measured with a MP-160 I–V curve tracer.
Finally the ambient temperature and the wind speed are
measured by the meteorological station of NEAL installed in
URER/MS Adrar (Research Unit in Renewable Energies in
the Saharan Medium); the interval of measure is one minute.
The electrical specific parameters of the module at reference
conditions are: The short-circuit current Isc= 9.13 A, the opencircuit voltage Voc= 38.7 V, the current at maximum power
point Ip= 8.34 A, the voltage at maximum-power point Vp= 30
V, the maximum-power point Pp= 250 W, the number of cells
Ns=60 cells and the surface area A=1620mm x 980mm.
(
)
(1)
The photovoltaic convective heat transfer coefficient for air
flowing over the outside surface of the glass cover obtained by
[18]:
(2)
A and v are, the PV area surface and wind velocity
respectively.
The exergy efficiency of a photovoltaic system is defined as
the ratio of the exergy of the PV system which is mainly the
electrical power output of the system to the exergy rate from
the solar irradiance. The exergy efficiency gives the
quantitative and the qualitative of energy [17]. Therefore,
exergy efficiency of the photovoltaic panels can be expressed
as [16]:
(
(
The cell temperature is measured by using Equation (7) given
as:
)
)
(3)
Where GT is the solar radiation and Tsun is the sun temperature
6000 K [19].
The solar cell power conversion efficiency is the ratio of
actual electrical output and input solar energy incident on the
solar cell area [20]-[21].
(4)
The solar cell power conversion efficiency can also be
presented with the fill factor term:
(5)
(6)
(7)
The experimental open-circuit voltage, short-circuit current
and maximum power point at March 21 to 23, 2013 utilized in
this paper are plotted at the same graph in Figure 1.
RESULTS AND DISCUSSION
The wind speed used in this paper during the three days is
shown in Figure 2. The wind speed ranges between 1.7 m/s to
7.1 m/s, between 0 m/s to 4.1 m/s and between 0.3 to 10.7
m/s from the days of March 21, 22 and 23, 2013 respectively.
We note here, that the wind speed is an essential factor effects
on the efficiencies of photovoltaic panel.
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50
250
40
200
30
150
20
100
63
Power (W)
Voltage (V)
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Voltage Voc
Power Pp
Current Isc
10
0
0
20
50
40
60
80
100
120
140
160
0
180
Times
Fig. 1. Experimental open-circuit voltage, short-circuit current and maximum power point at March 21 to 23, 2013.
12
March 21-22-23, 2013
10
Wind speed (m/s)
8
6
4
2
0
0
20
40
60
80
100
120
140
160
180
Times
Fig. 2. Hourly wind speed measured at the site of the tested days.
Figures 3-5 shows the variation in efficiencies, ambient
temperature and solar radiation at the three tested days of
March 21, 22 and 23, 2013, respectively.
Figure 3 present the plotted of the efficiencies during the
cloudy day of March 21. The energy efficiency varies between
22.3% and 17.2%. The exergy efficiency varies between 5.3%
and 12%. The power energy efficiency varies between 12.3%
and 16.10%. The ambient temperature varies from a minimum
of 19.13°C to a maximum of 29.21°C at 09:20 am and 14:10
pm respectively. The solar radiation varies from446 W/m2 to
1061.8 W/m2 at 09:20 am and 13:10 pm respectively. Figure 4
presents the plotted of the efficiencies during the clear day of
March 22. The energy efficiency varies between 10.83% and
21.85%. The exergy efficiency varies between 7.98% and
14.54%. The power energy efficiency varies between 8.10%
and 16.38%.The ambient temperature varies from a minimum
of 19.17 °C to a maximum of 31°C at 09:20 am and 16:20 pm
respectively. The solar radiation varies from90.14 W/m2 to
996 W/m2 at 18:40pm and 13:10 pm respectively.
However, Figure 5 presents the plotted of the efficiencies
during the clear day of March 23.The energy efficiency varies
between 9.28% and 22.06%. The exergy efficiency varies
between 1.8% and 15.5%. The power energy efficiency varies
between07.55% and 16.83%.
The ambient temperature varies from a minimum of 16°C to a
maximum of 32.73°C at 07:10 am and 16:20 pm respectively.
The solar radiation varies from 11.9 W/m2 to 989 W/m2 at
07:10 am and 13:10 pm respectively.
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60
Exergy efficiency
Energy efficiency
Power energy efficiency
Ambient temperature
March 21, 2013
50
Solar radiation (W/m2)
Solar radiation
800
40
600
30
400
20
200
10
0
5
10
15
20
25
30
Efficiencies (%) and Ambient temperature (°C)
1000
0
64
0
35
Times
Fig. 3. Variation in efficiencies, ambient temperature and solar radiation in March 21, 2013.
1200
throughout the day. These variations are occurred to the rapid
dependence rapidly of the wind speed, solar radiation and
ambient temperature.
Solar radiation
March 22, 2013
Exergy efficiency
Energy efficiency
Power energy efficiency
Ambient temperature
Solar radiation (W/m2)
1000
60
50
800
40
600
30
400
20
200
10
0
0
10
20
30
Times
40
50
Efficiencies (%) and Ambient temperature (°C)
The effect of weather conditions i.e., solar radiation, ambient
temperature and wind speed on the exergy efficiency is shown
in Figures 6-8, respectively. We observed in Figures 6-8 that
the exergy efficiencies vary rapidly
0
60
Fig. 4. Variation in efficiencies, ambient temperature and solar radiation in March 22, 2013.
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Exergy efficiency
Energy efficiency
Power energy efficiency
Ambient temperature
1000
March 23, 2013
50
Solar radiation (W/m2)
Solar radiation
800
40
600
30
400
20
200
10
0
0
10
20
30
Times
40
Efficiencies (%) and Ambient temperature (°C)
1200
65
0
60
50
Fig. 5. Variation in efficiencies, ambient temperature and solar radiation in March 23, 2013.
With an increase of wind speed and ambient temperature there
is a decrease in the exergy efficiency. However, the exergy
efficiency increases with an increase in solar radiation.
In general, it is clear that the efficiencies decreased as a
function of time during the day.
The exergy efficiency decreases from 11.84% to 6.69% at
09:18 am to 15:50 pm from the testing day of March 21 and
from 14.54% to 7.98% at 09:20 am to 18:40 pm from the
testing day of March 22.
0.16
0.14
Exergy efficiency (%)
0.12
0.1
0.08
0.06
23/03/2013
22/03/2013
21/03/2013
linear fit
0.04
0.02
0
100
200
300
400
500
600
Solar radiation (W/m2)
700
800
900
1000
Fig. 6. Exergy efficiency vs. solar radiation of the three days.
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0.16
0.14
Exergy efficiency (%)
0.12
0.1
0.08
0.06
23/03/2013
22/03/2013
21/03/2013
linear fit
0.04
0.02
0
10
20
30
40
50
Ambient temperature (°C)
60
70
Fig. 7. Exergy efficiency vs. ambient temperature of the three days.
0.16
23/03/2013
22/03/2013
21/03/2013
linear fit
0.14
Exergy efficiency (%)
0.12
0.1
0.08
0.06
0.04
0.02
0
0
2
4
6
Wind speed (m/s)
8
10
12
Fig. 8. Exergy efficiency vs. wind speed of the three days.
CONCLUSION
In this paper, an investigate of three different efficiencies i. e.,
energy efficiency, power energy efficiency and exergy
efficiency of the photovoltaic module performance are studies
and analyzed during three days i.e., March 21-22, 2013. It is
clear found that the efficiencies decreased as a function of
time during the day. The effect of weather conditions i.e.,
solar radiation, ambient temperature and wind speed on the
exergy efficiency are also analyzed.We have noticed that the
three exergy efficiencies vary in an expeditious manner with
the variation of climatic factors throughout the day. This
change resulted from the negative impact of wind speed and
ambient temperature and positive impact of solar radiation on
the efficiency. In other words, with increasing the wind speed
and the ambient temperature we observe a decrease in the
exergy efficiency and however, the increase in solar radiation
leads to an increase in the exergy efficiency.
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