Renewable Energy 164 (2021) 867e875

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Renewable Energy
journal homepage: www.elsevier.com/locate/renene

An efficient pulsed- spray water cooling system for photovoltaic

panels: Experimental study and cost analysis
Amirhosein Hadipour a, Mehran Rajabi Zargarabadi a, *, Saman Rashidi b
a
Faculty of Mechanical Engineering, Semnan University, P.O.B. 35131-191, Semnan, Iran
b
Department of Energy, Faculty of New Science and Technologies, Semnan University, Semnan, Iran

a r t i c l e i n f o a b s t r a c t

Article history: Cooling of photovoltaic panels is an important factor in enhancing electrical efficiency, reducing solar cell
Received 13 February 2020 destruction, and maximizing the lifetime of these useful solar systems. Generally, the traditional cooling
Received in revised form techniques consume considerable amount of water, which can be a major problem for large scale
18 August 2020
photovoltaic power stations. In this experimental study, a pulsed-spray water cooling system is designed
Accepted 3 September 2020
Available online 16 September 2020
for photovoltaic panels to improve the efficiency of these solar systems and decrease the water con-
sumption during the cooling process. The results of the photovoltaic panel with the pulsed-spray water
cooling system are compared with the steady-spray water cooling system and the uncooled photovoltaic
Keywords:
Photovoltaic panels
panel. A cost analysis is also conducted to determine the financial benefits of employing the new cooling
Water cooling system systems for the photovoltaic panels. The results show that as compared with the case of non-cooled
Pulsed-spray panel, the maximum electrical power output of the photovoltaic panel increases about 33.3%, 27.7%,
Electrical efficiency and 25.9% by using the steady-spray water cooling, the pulsed-spray water cooling with DC ¼ 1 and 0.2,
Cost analysis respectively. The pulsed-spray water cooling system with DC ¼ 0.2 can reduce the water consumption to
one-ninth in comparison with the case of steady-flow one. The levelized cost of electricity by the un-
cooled system was found lower than the spray-cooled systems but very near to pulsed-spray water
cooling with DC ¼ 0.2. The levelized cost of electricity produced by the PV system is reduced about 46.5%
and 76.3% by using the pulsed-spray water cooling system with DC ¼ 1 and 0.2, respectively as compared
with the case of steady-spray water cooling system. As a result, the new pulsed-spray water cooling is
efficient from the economic point of view.
© 2020 Elsevier Ltd. All rights reserved.

1. Introduction efficiency can decrease about 0.5% with 1  C increase in panel

temperature [4,5].
Due to the increasing demand for energy and the limitation of In most of cooling methods designed for PV panels, water and
fossil energy sources as well as increasing environmental pollution, air are used as the working fluids. Air cooling needs less energy as
the need to use renewable energy sources is very high. Photovoltaic compared with water cooling, while, cooling capacity of water is
panels (PV) are the technology of the direct conversion of solar more than the cooling capacity of air. Wang et al. [6] focused on the
energy into electrical energy. However, the energy conversion ef- direct-contact fluid film cooling method used for the solar panel.
ficiency of these panels is quite low because most of solar energy is They controlled the mean temperature of the solar panel below
lost as heat. Accordingly, the temperature of PV cells increases and 80  C by using this method. Jakhar et al. [7] used the water as the
this leads to reduce the voltage and the electrical efficiency of the coolant in the PV panel. They set the water channels at the rear of a
system [1e3]. As a result, designing efficient cooling system for PV PV panel. Their results showed that this system can increase the
panels is essential. Many studies have focused on the negative ef- efficiency of the PV panel. Chandrasekar and Senthilkumar [8]
fects of increase in the temperature on the efficiency reduction of cooled down the PV panels by the heat spreaders in conjunction
PV panels. These investigations have shown that the electrical with the cotton wick structures. They found that the temperature of
the PV panel decreases up to 12%, and the electrical efficiency of
this device increases about 14% by using this cooling technique.
* Corresponding author.
Bahaidarah [9] investigated the potentials of jet impingement
E-mail address: rajabi@semnan.ac.ir (M. Rajabi Zargarabadi). cooling system for controlling the temperature of the PV panel.

https://doi.org/10.1016/j.renene.2020.09.021
0960-1481/© 2020 Elsevier Ltd. All rights reserved.
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

Nomenclature DC duty cycle (the ratio of on-time to off-time in a cycle)

CRF capital recovery factor
Ap effective surface of the PV panel, (m2) O&M operating and maintenance
a absorptivity i Interest rate (%)
e evaporation coefficient, (kg m2/s) n life of panel (years)
E solar irradiation, W/m2 LCOE levelized cost of electricity
P partial pressure, Pa Pe electric power output of the PV panel, W
r latent heat of the water evaporation, (J/kg)
Pe electric power output of the PV panel, W Greek symbols
h convection heat transfer coefficient, (W/m2 K) u the uncertainty of different parameters
Qe total evaporation heat loss from the PV panel, (W) t time period, (s)
Qc total convection heat loss from the PV panel, (W) s StefaneBoltzmann constant, (W/m2 K4)
Qr total irradiation heat loss from the PV panel, (W) ε emissivity
Q loss overall heat loss from the PV panel, (W)

They recorded the maximum cell temperature of 69.7  C for an used to improve the efficiency of the PV panel in a hybrid wind and
uncooled panel. The jet impingement cooling system can decrease solar system. They observed that the total power generated by the
the cell temperature about 31.1  C and 36.6  C for December and system increases about 21% by using the jet impingement cooling
June, respectively. In addition, the power efficiency improves up to system as compared with the simple cooling system. There are
49.6% and 51.6% for December and June, respectively by using this other studies about using water as the coolant for the PV panels
technique. Castanheira et al. [10] used the On/Off system instead of [23e25]. In all these studies, the power output was increased in the
continuous water flow in the PV power plant. It was concluded that range of 10%e20% by using the cooling techniques. In the experi-
the annual energy production can be improved about 12% on a mental and numerical studies, Chow et al. [26] investigated the
5 kW section of a 20 kW plant by using this technique. In another effects of different parameters on the performance of a PV-thermal
investigation, Fakouriyan et al. [11] designed a new cooling module system. They used the water as the working fluid. They showed that
for the PV panel. They employed the hot water generated by the efficiency of PV-thermal system enhances by using the glass
absorbing the thermal energy from the PV panel for supplying the cover. Tiwari et al. [27] examined the effects of ambient tempera-
hot water for the domestic applications. They recorded the payback ture on the efficiency of the PV panels. They conducted their ex-
period of 1.7 years for their system. Ni
zeti
c et al. [12] investigated periments in the summer days. Their results showed that in the
the performance and economic effects of the active cooling mod- midday, the PV system has the least efficiency as the air tempera-
ules for the PV panel. They found that 10%e20% improvement in the ture is high. Alami [28] studied the effects of the evaporative
performance can be achieved by using the water cooling tech- cooling implemented on the PV system. It was found that the power
niques. In addition, their economic study indicated that the active output of the PV system can increase up to 19% by using this cooling
cooling techniques are not economically viable and they need the technique.
advanced control systems to reduce their costs. Generally, in the The literature review indicated that the efficiency of PV systems
water cooling systems, the water is sprinkled on the surface of PV can improve considerably by using an efficient cooling technique.
panel or the water channels are used to control the temperature of The previous studies conducted on the water spray cooling systems
the panel [13e16]. Yang et al. [17] integrated a spray cooling showed that the cooling of PV panel from the front is significantly
module with a shallow geothermal energy heat exchanger to better as compared with other cases [19,20]. In most cases, the
improve the efficiency of the PV panels. They concluded that the cooling system with the steady-flow design was used to cool down
system with a u-shaped borehole heat exchanger is more efficient and control the temperature of the PV panels in the previous
than the system without the u-shaped borehole heat exchanger. studies. However, these systems consume considerable amount of
Bahaidarah et al. [18] reviewed the PV panel cooling systems. Their water, which can be a major problem for large scale PV power
review showed that the active cooling by impingement jet, stations. As a result, in the present study, a pulsed-spray water
microchannels, and hybrid impingement jet-microchannel are cooling system is designed and tested to cool down the PV panel
more effective for removing high heat flux from the PV surfaces. and decrease the water consumed during the cooling process. The
Abdolzadeh and Ameri [19] sprayed the water on the front side of electrical efficiency of the PV panel, IeV characteristic curves,
the PV panel. They observed the significant improvement in the temperature of cells, and the amount of water consumed during the
electrical efficiency of the system by using this technique. In an cooling process are investigated for two cooling systems. The re-
experimental study, Ni
zeti
c et al. [20] investigated the effect of sults of the PV panel with the pulsed-flow spray cooling system are
water spray cooling on the PV panel performance. They investi- compared with the steady-spray water cooling system and the
gated the effects of the water spray cooling system on the perfor- uncooled PV panel. Finally, a cost analysis is arranged to determine
mance of PV panel for three cases. They used the water spray on the the financial benefits of employing the new cooling systems for the
front side, back side, and both back and front sides of the PV panel photovoltaic panels.
in these cases. Their results showed that for the case of the water
spray used on the front side, the efficiency of PV panel is signifi- 2. Experimental setup
cantly better than the case of the water spray employed on the back
side. A back side water cooling method is used by Bahaidarah et al. 2.1. Experimental procedure details
[21]. Their results showed that the electrical efficiency can be
improved about 9% for the hot climate condition by using this In this study, the experimental setup comprises of two PV units.
cooling method. Rahimi et al. [22] performed both experimental Each PV unit has 36 monocrystalline silicon solar cells. The details
and numerical investigations on a jet impingement cooling system of the units are presented in Table 1. The realistic and schematic
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A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

illustrations of the experimental setup are shown in Figs. 1 and 2. As

shown in Fig. 1, one of the PV panels has a spray cooling system,
while the other one is not equipped with the cooling system. Two
systems are placed in the direction of the south with angle of 30
with respect to the horizontal. They are tested under the same
conditions. The cooling nozzles are also placed with angle of 30
with respect to the PV panel. The cooling system has 9 five-micron
nozzles with 12 cm distance with each other. The nozzle type is a
simple orifice and the distance between the nozzle and PV panel is
8 cm. In this experiment, a solenoid valve is used to regulate the
periodicity of the water spray (See Fig. 2). The infrared camera and
the type K thermocouple are employed to measure the tempera-
tures of the PV cells and ambient, respectively. The current and
voltage are measured by using the digital multimeter with data
storage capability. In addition, the total solar radiation is measured Fig. 1. Photograph of the PV panel.
by a pyranometer with data storage capability. The pyranometer is
installed parallel to the PV panel. The experimental data are
collected on the certain days of June 2019 from 11:30 a.m. to 3:30
p.m., at 10-min intervals. The tests are carried out in Semnan with
geographical coordinates of 53 230 E, 35 330 N, Iran.

2.2. Uncertainty analysis

The uncertainties of the measuring instruments used in the

experiment are presented in Table 2. To analyze the uncertainties of
measurements in the experiments, the equation of uncertainty and
the measurement error provided by Holman [29] are used. The
uncertainty for the efficiency of PV panel is defined by:
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
uh  u  2  u  2  u  2 u 2
V I E Ac
¼ þ þ þ (1)
h V I E Ac

where V, I, E, and Ac are the voltage, current, solar irradiation, and

cross-section of the PV panel, respectively. u indicatesthe uncer-
tainty of different parameters and h is the efficiency of the PV panel.
The maximum uncertainty of the efficiency of the PV panel recor-
ded in the experiment is 2.92%.
Fig. 2. Schematic view of the PV panel with spray cooling system.

3. Theoretical aspects and analytical model

Table 2
As already mentioned, a row of water spray nozzles with peri- Uncertainties of measuring instruments.
odical and steady flows is used as the cooling system in this study to Measuring instrument Uncertainty
reduce the temperature of PV panel and increase the electric power
Infrared camera ±0.4
output of this solar system. Generally, a small portion of the solar Pyranometer ±5
irradiation, E, received by the panel surface, Ap; can be used to Voltmeter ±0.5
generate the electrical power. The major amount of the solar irra- Amperemeter ±0.5
diation is used to increase the internal energy of PV panel as DUpanel
and the rest amount is wasted into the surroundings as Qloss .
General energy flows and heat transfer mechanisms in the PV panel
are disclosed in Fig. 3. As shown in this figure, the overall heat loss QSolar ¼ a:E:Ap (2)
consists of convection, QC , radiation, QR , and evaporation heat loss,
QE . The solar irradiation received by the PV panel, as the energy where a is the absorption coefficient. The overall heat loss can be
input of the system, is defined by: calculated as follows:

Table 1
Details of the examined PV panel.
.
PV panel characteristics under the standard conditions (E ¼ 1000W and T ¼ 25  C)
m2
Model STP085B-12/BEA
Number of cells in the module 36
Maximum power 85 W ± 5%
Current at P max/short-circuit current 4.8/5.15 A
Voltage at P max/open-circuit current 17.8/22.2 V
Dimensions 1195 mm*541 mm*30 mm
Energy class A

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A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

the heat rejection from the panel surface, which is highly related to
the evaporation coefficient. In addition, the evaporation coefficient
depends on the surrounding air conditions and the average tem-
perature of the water film on the panel surfaces.

4. Results and discussion

Fig. 4 shows the different flow modes considered for the cooling
system in this study. To obtain the reliable results, the PV panel is
tested in four different circumstances. These circumstances are
listed as follows:

(a) PV panel without the cooling system

(b) PV panel cooled down by the steady-flow water spray cool-
ing system
Fig. 3. General energy flows and heat transfer mechanisms from the PV panel. (c) PV panel cooled down by the pulsed-spray water cooling
system with the duty cycle (DC) of 1. The duty cycle is defined
Qloss ¼ QC þ QR þ QE (3) as the ratio of on-time to off-time in a cycle.
(d) PV panel cooled down by the pulsed-spray water cooling
The heat lost by the convection should be considered for both system with the duty cycle of 0.2.
sides of the PV panel as follows:
The water flow rates considered for the pulsed-spray cooling
QC ¼ QC;F þ QC;B (4) systems with DC ¼ 0.2 and 1 are 0.12 and 0.52 L/min per m2 of PV
module, respectively. In addition, the water flow rate used for the
where QC;F and QC;B are the heats lost by the convection from the steady flow cooling system is 1.24 L/min per m2 of PV module.
front and back sides of the PV panel, respectively. QC;F and Q C;B are
calculated by:
4.1. General experiment circumstances
 
QC;F ¼ hF Ap TP;F  Ta;F
The experimental data were obtained on the specific summer
  days with ambient temperature in the range of 28  Ce31  C. All
QC;B ¼ hB Ap TP;B  Ta;B (5) experiments were performed outdoors with the air velocity in the
The overall heat lost by the radiation can be expressed as range of 1e1.4 m/s. The effect of air velocity changes on heat
follows: transfer from the PV panel is negligible. The inlet water tempera-
ture is approximately constant at 18  C. Fig. 5 displays the intensity
QR ¼ QR;F þ QR;B (6) of solar irradiation during the experiment for June 04, 2019. The
data in this figure are obtained at 10-min intervals. According to
where QR;F and QR;B are the heats lost by the radiation from the this data, the average amount of solar irradiation is 985 W=m2 .
front and back sides of the PV panel, respectively. QR is defined by:
  4.2. The effect of pulsed-spray water cooling system on the
QR ¼ s:ε:Ap :Fxy Tx4  Ty4 (7) electrical power output and electrical efficiency of the PV panel

In this equation, Fxy is the appropriate view factor for the front Fig. 6 shows the effect of different values of duty cycle on the
and back sides of the PV panel. maximum electrical efficiency. As shown in this figure, by
The overall heat lost by the evaporation is related to different decreasing DC to 0.16, 0.13, and 0.1, the maximum electrical effi-
parameters such as the temperature of water flow sprayed on the ciency significantly decreases, while, by decreasing DC to 1 and 0.2,
PV panel, surrounding air temperature, surrounding air velocity, small changes in maximum electrical efficiency can be observed
and relative humidity of surrounding air. Since in this study a row of
water jet is sprayed on the front side of the PV panel, the heat lost
by the evaporation can be obtained by using the following
equation:

QE ¼ QE;F (8)

The general form of the heat lost by the evaporation is:

QE ¼ e:Ap :ðPs  Pd Þ:r (9)

where e and r represent the evaporation factor and the latent heat
of evaporation, respectively. Ps and Pd are the partial pressures.
The evaporation coefficient has a significant influence on the
evaporation heat loss, which generally depends on the surrounding
air temperature, water jet temperature, and relative humidity of
the surrounding air. Due to the heat transfer rate between the panel
surface and the water jet, the average temperature of the panel is
also very important. The main purpose of this study is to increase Fig. 4. Velocity profiles of water jet sprayed on the PV panel.

870
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

efficiency of solar panels are mainly affected by the visible portion

of the solar spectrums rather than the infra-red light.
Fig. 8 illustrates the variations of the electrical power output
versus the voltage for four cases (cases a to b) in the period of
highest solar irradiation levels. As can be seen in this figure, the
maximum electrical power output is 54 W for the uncooled panel.
In addition, the maximum electrical power outputs of 72 W, 69 W,
and 68 W can be achieved by using steady cooling system, pulsed
cooling systems with DC ¼ 1, and DC ¼ 0.2, respectively in the PV
panel.
As a result, the maximum electrical power output of the PV
Fig. 5. Variation of solar irradiation intensity during the experiment for June 04, 2019.
panel increases about 33.3%, 27.7%, and 25.9% by using steady
cooling system, pulsed cooling systems with DC ¼ 1, and DC ¼ 0.2,
respectively as compared with the case of uncooled panel. The
maximum electrical power output for the uncooled panel is
recorded at voltage of 13.5 V. For three PV panels with the cooling
system, this voltage is shifted to about 17 V. It is clear that the use of
a water spray cooling system causes to shift the point with the
maximum output power to a higher voltage.
Fig. 9 discloses the IeV characteristic curves for four cases. The
mean maximal electrical efficiency of 9.1% is recorded for the case
of uncooled PV panel. The efficiencies of 12.1%, 11.6%, and 11.5% can
be achieved by using steady cooling system, pulsed cooling systems
with DC ¼ 1, and DC ¼ 0.2, respectively. Accordingly, as compared
with the case of uncooled PV panel, the mean output power in-
creases about 29.6%, 25.2%, and 24.1%, respectively as the steady
cooling system, pulsed cooling systems with DC ¼ 1, and DC ¼ 0.2
were applied. Generally, the short circuit current and open circuit
voltage are under the influence of the temperature variation of the
Fig. 6. Effects of the periodic water jet flow on the electrical efficiency and the water cells. The results of previous studies indicated that the open circuit
consumption.
voltage reduces with increasing the temperature of cells. This leads
to decrease in the electrical efficiency of PV panel [30]. In addition,
between the steady cooling system and the pulsed-spray cooling the dusts can decrease the panel efficiency. Dusts act as a barrier
systems with DC ¼ 1 and 0.2. However, the water consumption is and prevent from the penetration of the sunlight through the PV
drastically reduced. module glass cover and barricade to reach the solar cells. In this
The effects of the periodic water jet flow on the electrical effi- situation, free electrons cannot be excited to conduction band by
ciency and the water consumed by the cooling system for different the photons of sunlight radiation and hole-electron cannot be
pulsations are shown in Fig. 6. It can be seen that the panels cooled separated. As a result, the electric currents cannot be generated by
down by the pulsed-spray cooling systems with DC ¼ 1 and 0.2 the PV cells. This results in a considerable decrease in PV efficiency
have approximately the same values of the maximum electrical [32]. These dusts can be removed by using the water spray cooling
efficiency. The panel cooled down by the pulsed-spray cooling system in the front of the panel. All three cooling systems consid-
systems with DC ¼ 1 and 0.2 have approximately the same values of ered in this study can decrease the temperature of PV panel and
the maximum electrical efficiency has only 5% lower maximum remove the dusts from the panel surface.
electrical efficiency as compared with the panel cooled down by the As shown in Figs. 8 and 9, the differences between the electrical
steady-flow cooling system. However, the pulsed-spray cooling power outputs of three cooling systems are negligible. However,
system with DC ¼ 0.2 can reduce the water consumption to one- the pulsed-spray cooling system is more efficient as it consumes
ninth in comparison with the case of the steady-flow cooling lower amount of water. It should be highlighted that although the
system. water flow rate is reduced considerably by using a pulsed-spray
Fig. 7 shows the effects of cooling method on temperature and cooling system, but the panel remains moist. Accordingly, the
power output of the PV panel for different intensities of solar panel can be cooled down after disconnecting the water jet.
irradiation. According to this figure, the water spraying cooling is
more effective in high solar irradiation. It can be seen that as the 4.3. The effect of different cooling systems on the panel temperature
solar irradiation increases from 800 to 1200 W/m2, more temper- reduction
ature reduction is observed in PV panel and consequently, higher
power output can be achieved. It can be concluded that the increase The variations of the temperature of PV cells with time for four
in solar irradiation from 800 to 1200 W/m2 does not affect the cases are shown in Fig. 10. It can be seen that the temperature of the
priority of cooling method. panel surface decreases considerably by using different cooling
It should be noted that the reflection of electromagnetic radia- systems. The temperature of panel surface for the uncooled PV
tions by water film in the PV panel with cooling system is small. system is varied in the range of 56.8  C and 57.9  C, while by
However, during the transmission of electromagnetic radiations applying the spray cooling systems, pulsed-flow or steady-flow, the
through the water layer, a portion of the electromagnetic spec- temperature of panel surface can be varied in the range of
trums may be absorbed by the water molecules. This absorption 24.2  Ce27.8  C. The results of previous studies showed that by
occurs at a specified range of wavelengths. Fortunately, the ab- using a steady-spray cooling system, the temperature of panel
sorption occurs mainly in the red-infrared region [31] and the surface can decrease about 2.4 times in comparison with the case of
uncooled panel [19,20].
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A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

Fig. 7. Effect of variations in solar irradiation on (a) PV temperature and (b) electrical efficiency.

Fig. 8. Variations of electrical power output with the voltage for four cases (cases a to
b). Fig. 10. Effects of different cooling systems on the panel temperature reduction.

panel temperature decreases from 26.5  C to 57.1  C by using the

pulsed cooling system with DC ¼ 0.2 instead of the uncooled panel.
The results of this experimental study for different cases in the
highest solar irradiation levels are summarized in Table 3. The ef-
fects of periodic water jet flow on the electrical efficiency, electrical
power output, and temperature of PV panel surface are presented
in this table. As can be seen from the results, the steady-spray
cooling system has the best cooling mode, but there is no impor-
tant difference between the electrical efficiencies for the cases of
the steady-flow and pulsed-spray cooling systems. As a result, it is
recommended to use the pulsed-spray cooling system for PV panels
as this system can reduce the water consumption significantly.

Fig. 9. IeV characteristic curves for four cases.

5. Cost analysis

The same temperature reduction can be observed by using the A cost analysis is conducted for the proposed system. This anal-
pulsed-spray cooling system. However, the water consumption ysis is important as it can determine the cost of electricity generated
reduces considerably by using a pulsed-spray cooling system as by the PV system [33e35]. The details of cost analysis are presented
compared with the case of steady-spray cooling system. in the appendix. The results of this analysis for four cases are pre-
The effects of different cooling systems on the mean electrical sented in Table 4. The life of panel is ten years, n ¼ 10. It should be
efficiency and mean temperature of PV panel are investigated in pointed out that for the ideal environmental conditions and under
Fig. 11. This figure shows that the mean electrical efficiency and the certain other conditions, the lifetime of PV panels may be about 30
mean temperature of the panel cooled down by three cooling years. However, the operating temperature has the considerable ef-
systems, steady cooling system, pulsed cooling systems with fects on degradation of PV panels. The lifetime of PV panels can
DC ¼ 1, and DC ¼ 0.2, are approximately the same. The panel drastically decrease with increasing the operating temperature. For
electrical efficiency increases from 9.1% to 11.5%, while the mean example, Ogbomo et al. [36] presented a model to predict the life-
time of the PV panel under different operating conditions. Their
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A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

Fig. 11. Effects of different cooling systems on the mean electrical efficiency and mean
temperature of PV panel.
Fig. 12. Comparison between the costs and electrical efficiencies of all PV systems.

Table 3
Highlights of different cooling systems investigated in this paper.

Type of cooling system Power output Average temperature of panel Increase in power output Electrical efficiency Water consumption (L/
(W) ( C) (%) (%) min)

Uncooled PV panel 54 57.1 e 9.1 e

Steady-cooling system 72 24.8 33.3 12.1 0.81
Pulsed-cooling system with DC ¼ 1 69 25.7 27.7 11.6 0.32
Pulsed-cooling system with 68 26.5 25.9 11.5 0.078
DC ¼ 0.2

Table 4
The results of the cost analysis for four cases and n ¼ 10.

Type of PV system i (Interest rate (%)) CRF Capital cost O&M Water cost Cooling system cost Annual output LCOE
($)a ($) ($)b ($)c (kWh) ($/kWh)

Uncooled PV panel 20 (10) 0.24 160 4.8 0 0 166.0 0.26 (0.20)

(0.15)
Steady-spray cooling system 20 (10) 0.24 160 4.8 311 8 220.8 1.61 (1.54)
(0.15)
Pulsed-spray cooling system DC ¼ 1 20 (10) 0.24 160 4.8 131 40 211.7 0.86 (0.78)
(0.15)
Pulsed-spray cooling system 20 (10) 0.24 160 4.8 29 40 209.8 0.38 (0.3)
DC ¼ 0.2 (0.15)

In this study, all costs of system are calculated based on the prices in Iran.
a
The capital cost includes all costs of the PV system, such as the costs of mounting frames, cables, inverters, etc.).
b
In this study, the cost of water is calculated based on the price of water in Iran (2.2 $/m3).
c
The cooling system cost includes the costs of jet nozzle assembly, solenoid value, and electricity consumed by the solenoid valve and piping. Also, in this study the city
water pressure is used.

results showed that the lifetime of panel can be reduced to 9 years cooling system with DC ¼ 0.2 has considerable higher efficiency
for hot climate. The proposed cooling system can be widely used for and the slight higher cost as compared with the case of uncooled PV
PV systems installed in the regions with hot climate. As a result, panel. As a result, this pulsed-spray cooling system is recom-
n ¼ 10 years is selected for the lifetime of the system in this study. In mended for the usage in the practical applications.
addition, the levelized costs of electricity produced by four PV sys- The results of sensitivity analysis for various economic param-
tems are compared in Table 4. It can be seen that the levelized cost of eters are shown in Fig. 13. For the sample, a photovoltaic system
electricity produced by the PV system is reduced about 46.5% and with pulsed cooling with DC ¼ 1 is considered and the costs of all
76.3% by using the pulsed-spray cooling systems with DC ¼ 1 and 0.2, parameters, such as the water cost, cooling system costs, PV module
respectively as compared with the case of steady-spray cooling cost, etc. are reduced by 50% to determine the parameter with the
system. As a result, the new pulsed-spray cooling system is efficient highest impact on LCOE. As shown in Fig. 13, the cost of water
from the economic point of view. It should be highlighted that the consumption has the most impact on LCOE and the reduction in the
use of cooling system can eliminate the hot spots on the panel sur- cost of water reduces the LCOE, significantly. In addition, the cost of
face and accordingly, increases the lifetime of the panel, which is also cooling system equipment has the least impact on the LCOE. As a
benefit from the economic point of view. result, in this study, it is recommended to use the pulsed-spray
The costs and electrical efficiencies of all PV systems are water cooling system as it can increase the electrical efficiency of
compered in Fig. 12. As shown in this figure, the uncooled PV panel the PV system and reduce the water consumption and cost.
has the minimum cost, while the panel with the steady-spray Accordingly, for countries with high water costs, it is recommended
cooling system has the maximum cost. However, the efficiency of to use a pulsed-spray water cooling system with the low-duty cycle
uncooled PV panel is significantly lower as compared with other (DC) cooling system.
systems. The usage of steady-spray cooling system imposes
considerable cost on the system. The panel with the pulsed-spray

873
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

draft, Formal analysis, Writing - review & editing, conceived of the

presented idea, developed the theory and performed the compu-
tations, carried out the experiment, wrote the manuscript, dis-
cussed the results and commented on the manuscript, processed
the experimental data, performed the analysis, drafted the manu-
script and designed the figures, wrote Review & Editing. Mehran
Rajabi Zargarabadi: Conceptualization, Writing - original draft,
Formal analysis, Writing - review & editing, conceived of the pre-
sented idea, wrote the manuscript, discussed the results and
commented on the manuscript, processed the experimental data,
performed the analysis, drafted the manuscript and designed the
Fig. 13. Sensitivity analysis: Re-calculated LCOEs for the DC ¼ 1 pulsed-spray cooling figures, wrote Review & Editing. Saman Rashidi: Writing - original
system if key financial and cost parameters are reduced by 50% (reference LCOE draft, Formal analysis, Writing - review & editing, developed the
$0.86 at 100%). theory and performed the computations, wrote the manuscript,
processed the experimental data, performed the analysis, drafted
6. Conclusion
the manuscript and designed the figures, wrote Review & Editing.

In the present experimental study, a pulsed-spray cooling system

was designed for the PV panels. The results of this design were Declaration of competing interest
compared with the steady-spray cooling system and the case of
uncooled panel. The electrical efficiency of the PV panel, IeV char- The authors declare that they have no known competing
acteristic curves, temperature of cells, and the water consumed financial interests or personal relationships that could have
during the cooling process were investigated for two cooling sys- appeared to influence the work reported in this paper.
tems. The main results of this study are summarized as follows:

 The maximum electrical power output of the PV panel increases Appendix

about 33.3%, 27.7%, and 25.9% by using the steady-flow water
spray cooling system, pulsed-spray cooling system with DC ¼ 1, The cost of PV system is expressed by cost per area ($/m2).
and 0.2, respectively as compared with the case of uncooled However, the modules are often sold based on their cost per peak
panel. watt ($/Wp). Wp is potentially generated under peak solar irradiance
 The electrical efficiency decreases from 12.1% to 11.5% by using conditions. The following equation is used to convert the cost per
the panel cooled down by the pulsed-spray cooling system square meter to the cost per peak watt [33,37]:
instead of panel cooled down by the steady-flow cooling system.
$=m2
However, the pulsed-spray cooling system with DC ¼ 0.2 can $ Wp ¼ (A1)
h:1000Wp=m2
reduce the water consumption to one-ninth in comparison with
the case of steady-flow cooling system. In this study, the peak solar irradiance is 1000 W/m2 and the
 The temperature of panel surface reduces from 57.1  C to 24.8  C photovoltaic panel with cost of 160 $/m2 is used. Accordingly, the
and 26.5  C by using the steady-spray cooling system and cost per peak watt is 1.3 $/Wp for different modes investigated with
pulsed-flow cooling system with DC ¼ 0.2, respectively as the efficiency of h ¼ 12%.
compared to the uncooled PV system. As the basic economic concept for each PV system, the costs
 The levelized cost of electricity produced by the PV system is should be recovered by the useful energy produced by the system
reduced about 46.5% and 76.3% by using the pulsed-spray over its lifetime. The levelized cost of electricity, LCOE, is defined as
cooling system with DC ¼ 1 and 0.2, respectively as compared the ratio of the total cost of life cycle to the total lifetime energy
with the case of steady-spray cooling system. production based on the following equation [33,37,39]:
 The levelized cost of electricity by the uncooled system was
found lower than the spray-cooled systems but very near to ðAnuual cost þ O&MÞ ð$Þ
LCOE ¼ (A2)
pulsed-spray water cooling with DC ¼ 0.2. It should be Anuual output cost ðkWhÞ
mentioned that the small additional cost of the pulsed-cooling
The following equation is used to calculate the capital recovery
system can be justifiable in cases where high ambient temper-
factor, CRF, for the PV systems [34,38]:
atures cause premature failures of uncooled PV modules.
ið1 þ iÞn
CRF ¼ (A3)
ð1 þ iÞn  1
CRediT authorship contribution statement
The parameters, required to calculate the LCOE, are given in
Amirhosein Hadipour: Conceptualization, Writing - original Table A1 [34].

Table A1
The parameters required to calculate the LCOE

Annual output ¼ Average Annual Insolation  Efficiency

5KWh 365day
Average Annual Insolation ¼  ¼ 1825 kWh
day:m2 year
Annual Cost ¼ (Installation Cost  CRF) þ water cost þ (cooling system cost  CRF) þ O&M (O&M ¼ 3% of installation Cost per year)
Installation Cost ¼ Capital Cost  Station Capacity ¼ 160$
Station Capacity ¼ 1 m2
a
Capital Cost ¼ 160 $/m2 or (1.3 $/W)
a
The capital cost includes all costs of the PV system (mounting frames, cables, inverters, etc.).

874
A. Hadipour, M. Rajabi Zargarabadi and S. Rashidi Renewable Energy 164 (2021) 867e875

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