![photovoltaic panels. This is consistent with the results of Lu et al. 's study on the effect of dust deposition on ground-mounted solar PV arrays [22]. The trajectory distribution of snow particles is shown in Figure 5. Snow particles mainly accumulate on the surface of photovoltaic panels and the ground at the junction, which is caused by snow falling and accumulating on the ground under the influence of gravity. At the same time, snow accumulates on the ground below the photovoltaic panels due to turbulence on the back of the photovoltaic panels. Therefore, in practical engineering, we can increase the height of the panel from the ground to increase the sliding of snow.](https://www.researchgate.net/publication/368520361/figure/fig1/AS:11431281120392406@1676476443696/photovoltaic-panels-This-is-consistent-with-the-results-of-Lu-et-al-s-study-on-the_Q320.jpg)
Available via license: CC BY 4.0
Content may be subject to copyright.
Citation: Quan, Z.; Lu, H.; Zheng, C.;
Zhao, W.; Xu, Y.; Qin, J.; An, F.
Experimental Measurement and
Numerical Simulation on the
Snow-Cover Process of Solar
Photovoltaic Modules and Its Impact
on Photoelectric Conversion
Efficiency. Coatings 2023,13, 427.
https://doi.org/10.3390/
coatings13020427
Academic Editor: Alessandro Latini
Received: 19 December 2022
Revised: 17 January 2023
Accepted: 27 January 2023
Published: 13 February 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
coatings
Article
Experimental Measurement and Numerical Simulation on the
Snow-Cover Process of Solar Photovoltaic Modules and Its
Impact on Photoelectric Conversion Efficiency
Zijia Quan 1, Hao Lu 1, 2, *, Chuanxiao Zheng 1, * , Wenjun Zhao 2, Yongzhong Xu 2, Jing Qin 1and Feng An 1
1Laboratory of Energy Carbon Neutrality, School of Electrical Engineering,
Xinjiang University, Urumqi 830047, China
2Center of New Energy Research, School of Future Technology, Xinjiang University, Urumqi, 830047, China
*Correspondence: luhao@xju.edu.cn (H.L.); cxz@stu.xju.edu.cn (C.Z.)
Abstract:
The snow falling on the surface of photovoltaic modules tends to reduce the output power.
In order to understand the process of snow accumulating on solar photovoltaic modules and reveal
the impact of snow accumulation on photovoltaic conversion efficiency, the snow-cover process
was simulated on the surface of photovoltaic modules with different tilt angles by computational
fluid dynamics (CFD). On this basis, the relationship between the amount of snow and tilt angle
was explored. The snow effect of photovoltaic modules on photoelectric conversion efficiency was
studied by building a test platform. At the same time, a measurement platform of snow accumulation
on photovoltaic modules and photoelectric conversion efficiency was constructed. Through the
experiment of the relationship between snow thickness and snow sliding distance and the power
generation efficiency of photovoltaic (PV) modules, the influence of snow thickness and snow area
on the power generation efficiency of PV modules is discussed. The results show that the larger
angle between the photovoltaic panel and the ground is adverse to the accumulation of snow on
the panel. When the thickness of snow reaches 1 cm, the power generation efficiency of the entire
photovoltaic module reduces to 7.1% of that as normal. At the same time, the sliding of snow on
the photovoltaic panel improves the efficiency of photoelectric conversion. Through the analysis of
numerical simulation and experimental results, targeted suggestions are made on how to improve
the efficiency of power generation for photovoltaic power stations under snowy conditions, which
may provide a reference for engineering work.
Keywords:
photovoltaic modules; tilt angle; snow-cover process; photoelectric conversion efficiency
1. Introduction
At present, many countries around the world are actively promoting the development
of renewable energy. As a major source of clean energy in the future, photovoltaic sys-
tems offer considerable policy support, showing a promising prospect [
1
–
6
]. However,
the shielding of snow on photovoltaic modules could cause the failure of photovoltaic
panels, which has a major impact on photovoltaic power generation. It not only reduces
photovoltaic output but also hampers the prompt resumption of normal operation, which
puts the stability of the power grid at risk. In cold, snowy areas, when photovoltaic panels
are covered with snow, it can result in a complete power outage, and the total photovoltaic
power generation can be reduced by one-third throughout the winter [
7
,
8
]. In winter
months, the decline of power generation efficiency means that the grid-connected photo-
voltaic power stations face difficulty maintaining their power output as normal, which
easily causes light abandonment and is detrimental to the long-term development of the
whole photovoltaic industry [9–11].
According to Bill and Loren et al., it is not uncommon for snow to remain on photo-
voltaic panels for days or even weeks [
11
,
12
]. As demonstrated by Brench et al., photovoltaic
Coatings 2023,13, 427. https://doi.org/10.3390/coatings13020427 https://www.mdpi.com/journal/coatings
Coatings 2023,13, 427 2 of 15
system generation was reduced by 4% to 56% due to snow cover on the day after snowfall,
even in relatively mild weather [
13
]. Heidari et al. explored the impact of snow cover
on photovoltaic power generation, revealing that the energy loss caused by snowfall was
largely affected by the tilt angle and the severity of ground interference. According to the
study, the annual energy loss can be effectively reduced from 34% to 5% by increasing
the tilt angle of the barrier-free system from 0
◦
to 45
◦
[
14
]. By simulating the effect of
snow on the performance of photovoltaic systems, Loren et al. found out that for the fixed
inclination arrays installed at inclination angles ranging from 39
◦
to 0
◦
(flat), the annual loss
in typical years was expected to reach 12%–18%. Moreover, monthly losses are much more
severe, and when the snow is several feet thick, the PV panel output is lost for a month due
to the small tilt angle of the PV panel [
12
]. In order to prevent the impact of snow on the
output power of photovoltaic panels, Wang et al. studied the snow-removing coating on
the surface of photovoltaic modules. The results show that the presence of surface coating
can mitigate the impact of snow on photovoltaic panels by reducing adhesion and friction
or by partially absorbing solar irradiance to decompose snow [
15
,
16
]. Rahmatmand and
Yan et al. put forward the method of removing snow by electric heating for photovoltaic
panels, and the results show that this is a beneficial and practical method for removing
snow for photovoltaic panels, when the thickness of the snow is greater than the equivalent
height and the inclination angle of the photovoltaic panel is greater than the minimum
inclination angle [
17
,
18
]. Anadol introduced a method of snow melt on the surface of
photovoltaic modules heated by polyvinyl butyral interlayer transparent resistance wire.
Based on economic viability analysis results, it was concluded that the surface-heating
method is cost-effective when it is compared to the mechanical stripping method, as it only
uses electricity that is already available [
19
]. Amer et al. developed an electric curtain to
cover the surface of photovoltaic modules at night and during sandstorms. The system
successfully reduced the effects of condensation and dirt accumulation that may affect the
performance of photovoltaic panels and reduce their efficiency. This study also studied the
use of super-hydrophobic and super-hydrophilic coatings on the surface of photovoltaic
modules to reduce the impact of pollution through experiments. These two recommen-
dations can significantly reduce the frequency of cleaning photovoltaic panels, thereby
reducing water use, especially in areas with limited water supply [20].
However, most studies have used experiments to study the impact of snow cover
on photovoltaic power generation, and there are few studies on the simulation of the
snow-cover process through computational fluid dynamics (CFD). Based on numerical
simulation, this paper studies the influence of snow cover on the surface of a series of solar
photovoltaic modules with different tilt angles analyzes the snow-cover process on the
surface of solar photovoltaic modules and discusses the relationship between the snow
cover and the tilt angle of photovoltaic modules. On this basis, the impact of snow cover
on photovoltaic modules on the efficiency of photoelectric conversion was studied through
experimentation. At the same time, the test platform of photovoltaic snow and photovoltaic
conversion efficiency was constructed. Through the experiment of the relationship between
snow thickness and snow sliding distance and the power generation efficiency of PV
modules, the influence of snow thickness and snow area on the power generation efficiency
of PV modules is discussed.
2. Numerical Simulation and Result Analysis
In order to study the change of the flow field, it is necessary to consider the impact of
various variables such as pressure and the density of flow, establish a theoretical model
of the flow field, and solve the partial differential equations in the model through the
numerical iteration assisted by a computer [
21
]. To describe the flow field, there are three
basic laws involved: the law of conservation of momentum, the law of conservation of mass,
and the law of conservation of energy. Expressed as some basic mathematical equations,
these physical laws are also the governing equations of the flow field.
Coatings 2023,13, 427 3 of 15
The following is the momentum conservation equation:
→
f−1
ρgrad ·P+v∇2→
v=d→
v
dt
where
→
f
represents the mass force on the fluid, in N;
ρ
indicates the fluid density, in kg/m
3
;
P
denotes the static pressure, in Pa;
v
refers to the kinematic viscosity of the fluid, in m
2
/s;
and →
v stands for the velocity of the fluid, in m/s.
The following is the mass conservation equation:
∂ρ
∂t+∂(ρu)
∂x+∂(ρv)
∂y+∂(ρw)
∂z=0
where
t
represents time, in s, and
u
, and
w
refer to the components of the velocity vector in
the x, and z directions, respectively.
The energy conservation equation is expressed as
∂(ρT)
∂t+div(ρvT)=divk
CP
gradT+ST
where
CP
represents the specific heat capacity at constant pressure, in J/(kg.K);
k
indi-
cates the heat transfer coefficient of the fluid, in W/m
2
.K;
T
denotes the thermodynamic
temperature, in K; and STrefers to the viscous dissipation term.
According to the heat balance equation, the liquid-dust particles in the snow accumu-
lation process of PV modules meet the following equation:
d/dt (k+U)=Ne+Q
where d/dt is the total time derivative, K is the kinetic energy of the substance in the
control volume, N
e
is the power of external forces, and Q is the energy supply from external
sources per unit time.
In the computational domain, a structured grid developed by ANSYS ICEM 21.0 is
adopted, as shown in Figure 1. Only the whole area of the computing grid is shown in the
3D model in Figure 1a, and the three views of the computing grid are presented in Figure 1b.
The number of grids is 640,866, that of the quadrilateral is 48,620, and that of the hexagon
is 617,100. The mesh growth factor is 1.2, the mesh quality is 0.91, and the mesh angle
quality is 56.30. The finite volume method is applied to solve the conservation equation of
the wind field, while the SIMPLE algorithm is adopted to decouple the pressure field from
the velocity field. The convection and diffusion terms are discretized by the second-order
upwind scheme and the second-order central difference scheme, respectively. Moreover,
the Runge–Kutta method is used to solve the equation of motion of dust particles.
Figure 2shows the effect of snow at different tilt angles, and Figure 3shows the
relationship between the amount of snow on the surface of a PV module and the tilt angle.
According to the number of particles deposited on the photovoltaic module with different
tilt angles, the load applied to the photovoltaic module under snowy conditions can be
calculated. With each snowflake assigned a weight of 0.1 g, the load change curve of the
photovoltaic module in 10 sets of simulated data can be calculated. As suggested by the
calculation results, a larger tilt angle of the photovoltaic module leads to a smaller number
of snow particles deposited on the photovoltaic panel. The result shows the load applied
to the photovoltaic module decreases; this is because the larger the tilt angle, the greater
the gravity component of the downward motion of the snow particles. In practice, an
increase in the tilt angle is adverse to snow accumulation but conducive to snow removal.
The large tilt angle makes it easier for snow to slide quickly on the photovoltaic module.
Therefore, in those areas prone to heavy snowfall, the tilt angle can be increased to reduce
snow accumulation, which facilitates snow removal.
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(a) The entire area of the structured grid.
(b) A triplex view of a structured mesh.
Figure 1. Structured grid of high-speed airflow on the photovoltaic surface.
Figure 2 shows the effect of snow at different tilt angles, and Figure 3 shows the re-
lationship between the amount of snow on the surface of a PV module and the tilt angle.
According to the number of particles deposited on the photovoltaic module with different
tilt angles, the load applied to the photovoltaic module under snowy conditions can be
calculated. With each snowflake assigned a weight of 0.1 g, the load change curve of the
photovoltaic module in 10 sets of simulated data can be calculated. As suggested by the
calculation results, a larger tilt angle of the photovoltaic module leads to a smaller number
of snow particles deposited on the photovoltaic panel. The result shows the load applied
to the photovoltaic module decreases; this is because the larger the tilt angle, the greater
the gravity component of the downward motion of the snow particles. In practice, an in-
crease in the tilt angle is adverse to snow accumulation but conducive to snow removal.
The large tilt angle makes it easier for snow to slide quickly on the photovoltaic module.
Therefore, in those areas prone to heavy snowfall, the tilt angle can be increased to reduce
snow accumulation, which facilitates snow removal.
Figure 1. Structured grid of high-speed airflow on the photovoltaic surface.
Coatings 2023,13, 427 5 of 15
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The airflow streamlines on the photovoltaic array are shown in Figure 4. As can be
seen from Figure 3, the streamlines in the area away from the solar PV panel are quite
stable and parallel to the ground wall. However, solar PV panels generate a large number
of turbulent eddies in the near-wall region. The largest turbulent eddies are behind solar
photovoltaic panels. This is consistent with the results of Lu et al. ‘s study on the effect of
dust deposition on ground-mounted solar PV arrays [22]. The trajectory distribution of
snow particles is shown in Figure 5. Snow particles mainly accumulate on the surface of
photovoltaic panels and the ground at the junction, which is caused by snow falling and
accumulating on the ground under the influence of gravity. At the same time, snow accu-
mulates on the ground below the photovoltaic panels due to turbulence on the back of the
photovoltaic panels. Therefore, in practical engineering, we can increase the height of the
panel from the ground to increase the sliding of snow.
(a) 0°
(b) 5°
(c) 10°
(d) 15°
(e) 20°
(f) 25°
Coatings 2023, 13, x FOR PEER REVIEW 6 of 16
(g) 30°
(h) 35°
(i) 40°
(j) 45°
Figure 2. Snow-cover renderings of photovoltaic modules with different tilt angles.
Figure 3. Relationship between the density of snow on PV module surface and tilt angle.
Figure 2. Snow-cover renderings of photovoltaic modules with different tilt angles.
Coatings 2023,13, 427 6 of 15
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(g) 30°
(h) 35°
(i) 40°
(j) 45°
Figure 2. Snow-cover renderings of photovoltaic modules with different tilt angles.
Figure 3. Relationship between the density of snow on PV module surface and tilt angle.
Figure 3. Relationship between the density of snow on PV module surface and tilt angle.
The airflow streamlines on the photovoltaic array are shown in Figure 4. As can be
seen from Figure 3, the streamlines in the area away from the solar PV panel are quite
stable and parallel to the ground wall. However, solar PV panels generate a large number
of turbulent eddies in the near-wall region. The largest turbulent eddies are behind solar
photovoltaic panels. This is consistent with the results of Lu et al. ‘s study on the effect
of dust deposition on ground-mounted solar PV arrays [
22
]. The trajectory distribution
of snow particles is shown in Figure 5. Snow particles mainly accumulate on the surface
of photovoltaic panels and the ground at the junction, which is caused by snow falling
and accumulating on the ground under the influence of gravity. At the same time, snow
accumulates on the ground below the photovoltaic panels due to turbulence on the back of
the photovoltaic panels. Therefore, in practical engineering, we can increase the height of
the panel from the ground to increase the sliding of snow.
Coatings 2023, 13, x FOR PEER REVIEW 7 of 16
Figure 4. Streamlines for airflow around solar PV panel.
Figure 5. Snow particle trajectory distribution map.
Figure 4. Streamlines for airflow around solar PV panel.
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Figure 4. Streamlines for airflow around solar PV panel.
Figure 5. Snow particle trajectory distribution map.
Figure 5. Snow particle trajectory distribution map.
3. Experiment and Results Analysis
3.1. Effects of Snow-Cover Thickness on the Photoelectric Conversion Efficiency
In order to measure the output power of the photovoltaic panel, a measurement test
bench was developed, as shown in Figure 6. In this experiment, two 1000 W high-voltage
spherical hernia lamps were used to simulate solar radiation, while a voltage regulator was
employed to avoid voltage fluctuations by maintaining the output voltage as a constant
and avoid the change of the radiation light of the high-voltage spherical hernia lamp. The
trigger was applied to the anode and cathode of the xenon lamp at high frequency and high
voltage to make the xenon in the lamp ionization discharge, and a conductive channel was
established. The low-voltage DC current from the power supply of the xenon lamp could
continuously pass through the originally non-conductive xenon lamp, and the lighting of
the xenon lamp was triggered. As part of the solar-source simulation device, the dimmer
was used to adjust the intensity of the lighting for simulating the different intensities of
solar radiation. We conducted the experiment on the roof of the Electrical Engineering
College of Xinjiang University. The surface temperature was
−
12
°C
, and the average
snowfall rate was 69.3%. The temperature of the PV module was
−
10
°C
, and the ambient
temperature was
−
12
°C
. The solar cells used in the experiment were monocrystalline
silicon solar cells, with dimensions of 650 mm
×
350 mm, maximum power P
max
of 100 W,
open-circuit voltage V
oc
of 22.1 V, working voltage V
dc
of 18.5 V, short-circuit current I
sc
of
6 A, and working current I
mp
of 5.4 A. The MPPT controller was used in combination to
determine the maximum power point on the solar panel, and the energy-storage battery
was used to store the output energy of the photovoltaic panel as the system load. The
photovoltaic-power-generation power measurement system was constructed to measure
the output power of the photovoltaic panel accurately in the process of snow accumulation
under fixed lighting. The snow used in this experiment was a natural storm [23].
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3. Experiment and Results Analysis
3.1. Effects of Snow-Cover Thickness on the Photoelectric Conversion Efficiency
In order to measure the output power of the photovoltaic panel, a measurement test
bench was developed, as shown in Figure 6. In this experiment, two 1000 W high-voltage
spherical hernia lamps were used to simulate solar radiation, while a voltage regulator was
employed to avoid voltage fluctuations by maintaining the output voltage as a constant and
avoid the change of the radiation light of the high-voltage spherical hernia lamp. The trigger
was applied to the anode and cathode of the xenon lamp at high frequency and high voltage
to make the xenon in the lamp ionization discharge, and a conductive channel was estab-
lished. The low-voltage DC current from the power supply of the xenon lamp could contin-
uously pass through the originally non-conductive xenon lamp, and the lighting of the
xenon lamp was triggered. As part of the solar-source simulation device, the dimmer was
used to adjust the intensity of the lighting for simulating the different intensities of solar
radiation. We conducted the experiment on the roof of the Electrical Engineering College of
Xinjiang University. The surface temperature was −12 ℃, and the average snowfall rate was
69.3%. The temperature of the PV module was −10 ℃, and the ambient temperature was −12
℃. The solar cells used in the experiment were monocrystalline silicon solar cells, with di-
mensions of 650 mm × 350 mm, maximum power Pmax of 100 W, open-circuit voltage Voc of
22.1 V, working voltage Vdc of 18.5 V, short-circuit current Isc of 6 A, and working current Imp
of 5.4 A. The MPPT controller was used in combination to determine the maximum power
point on the solar panel, and the energy-storage battery was used to store the output energy
of the photovoltaic panel as the system load. The photovoltaic-power-generation power
measurement system was constructed to measure the output power of the photovoltaic
panel accurately in the process of snow accumulation under fixed lighting. The snow used
in this experiment was a natural storm [23].
Figure 6. Experimental system layout.
In order to study the effect of snow cover with different thicknesses on the photoe-
lectric conversion efficiency of photovoltaic modules, the photovoltaic panels were placed
horizontally outdoors in snowy weather to separately measure the output power of pho-
tovoltaic modules with a snow thickness ranging from 1 to 6 cm. Figure 7 shows the layout
of the experimental measurement with a snow thickness of 1–6 cm. Figure 8 shows the
impact of snow thickness on the efficiency of photovoltaic power generation. When there
Figure 6. Experimental system layout.
In order to study the effect of snow cover with different thicknesses on the photoelec-
tric conversion efficiency of photovoltaic modules, the photovoltaic panels were placed
horizontally outdoors in snowy weather to separately measure the output power of pho-
tovoltaic modules with a snow thickness ranging from 1 to 6 cm. Figure 7shows the
layout of the experimental measurement with a snow thickness of 1–6 cm. Figure 8shows
the impact of snow thickness on the efficiency of photovoltaic power generation. When
there was no snow, the photoconversion efficiency of the photovoltaic battery was 100%.
According to the experimental data, the power generation efficiency of the photovoltaic
module reduced to 7.1% at a 1 cm snow thickness. When it increased from 1 cm to 6 cm, the
power generation efficiency of the photovoltaic module continued a decreasing trend to
zero. When the thickness of snow reached 2 cm and 3 cm, the power generation efficiency
of the photovoltaic modules was unchanged, which is attributable to the impact of weather
during the experiment or the insufficient accuracy of the solar controller involved. When
the thickness of snow ranged between 3 cm and 6 cm, every 1 cm increase of snow thick-
ness reduced the power generation efficiency of photovoltaic modules by about 2%, which
basically conforms to a linear reduction. With the increase of snow thickness, the power
generation efficiency of photovoltaic modules is sharply reduced, which has a significant
impact on the power generation of photovoltaic power stations.
Solar radiation is a form of electromagnetic wave, which is similar to visible light
when projected onto the surface of an object. In this context, absorption, reflection, and
penetration can occur. Comprising the total energy Q projected onto the snow surface of
the photovoltaic module outside, part
Qα
is absorbed by the snow; part
Qp
is reflected
on the snow surface; and the rest, denoted as Qτpenetrates the snow to the surface of the
photovoltaic module. According to the law of conservation of energy, which is expressed
as
Q=Qα+Qp +Qτ
, the larger the thickness of snow, the more energy, indicated by gets
absorbed. However, the surface for the total amount of solar radiation, denoted as Q, is
finite, so it is inevitable that solar radiation infiltrates the snow to reach the surface. After
receiving solar radiation, photovoltaic modules reduce the photovoltaic-module output
power, as evidenced by the experimental data when the power generation efficiency of
photovoltaic modules declines.
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was no snow, the photoconversion efficiency of the photovoltaic battery was 100%. Ac-
cording to the experimental data, the power generation efficiency of the photovoltaic
module reduced to 7.1% at a 1 cm snow thickness. When it increased from 1 cm to 6 cm,
the power generation efficiency of the photovoltaic module continued a decreasing trend
to zero. When the thickness of snow reached 2 cm and 3 cm, the power generation effi-
ciency of the photovoltaic modules was unchanged, which is attributable to the impact of
weather during the experiment or the insufficient accuracy of the solar controller in-
volved. When the thickness of snow ranged between 3 cm and 6 cm, every 1 cm increase
of snow thickness reduced the power generation efficiency of photovoltaic modules by
about 2%, which basically conforms to a linear reduction. With the increase of snow thick-
ness, the power generation efficiency of photovoltaic modules is sharply reduced, which
has a significant impact on the power generation of photovoltaic power stations.
Solar radiation is a form of electromagnetic wave, which is similar to visible light
when projected onto the surface of an object. In this context, absorption, reflection, and
penetration can occur. Comprising the total energy Q projected onto the snow surface of
the photovoltaic module outside, part Qα is absorbed by the snow; part Qp is reflected
on the snow surface; and the rest, denoted as Qτ penetrates the snow to the surface of the
photovoltaic module. According to the law of conservation of energy, which is expressed
as Q = Qα +Qp +Qτ, the larger the thickness of snow, the more energy, indicated by gets
absorbed. However, the surface for the total amount of solar radiation, denoted as Q, is
finite, so it is inevitable that solar radiation infiltrates the snow to reach the surface. After
receiving solar radiation, photovoltaic modules reduce the photovoltaic-module output
power, as evidenced by the experimental data when the power generation efficiency of
photovoltaic modules declines.
(a) 1 cm
(b) 2 cm
(c) 3 cm
(d) 4 cm
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(e) 5 cm
(f) 6 cm
Figure 7. Experimental measurements with snow thicknesses of 1–6 cm.
Figure 8. Impact of snow thickness on photovoltaic power generation efficiency.
3.2. Test of the Influence of Snow Slip Distance on Photovoltaic Power Generation Efficiency
The current snow-removal technology relies on the heating of snow on the surface of
the photovoltaic module to melt part of the snow. The snow water generated by the melting
plays a role in lubrication between the photovoltaic module and the snow, thus reducing
the friction coefficient between them. As a result, the snow gradually falls from the surface
of the photovoltaic module. However, in winter, the temperature fluctuates around the
freezing point most of the time, and there is often heavy wind blowing. The melted snow
water tends to freeze rapidly due to the cooling effect of wind, thus making the snow attach
tightly to the surface of the photovoltaic modules. Consequently, it is difficult to conduct
snow-removal operations. Therefore, it is particularly important to slide the snow away
from the surface of the photovoltaic modules in time. In order to faithfully simulate the im-
pact of snow on photovoltaic power generation, especially when the snow falls from the
photovoltaic panel, the impact of different sliding distances on power generation efficiency
was studied. This experiment was mainly to simulate the sliding process of snow on the
surface of photovoltaic modules. The snow was made manually, and the tilt angle of solar
cells was 45°. This experiment was very important to explore the relationship between the
sliding distance of the snow on the surface of the PV module and the power generation
efficiency of the PV module and to analyze the change characteristics of the power genera-
tion efficiency of the PV module during the sliding process. On this basis, targeted sugges-
tions are made on snow removal for photovoltaic modules in winter.
According to the influence of snow thickness on photovoltaic experimental effi-
ciency, it is known that when the snow thickness reaches 1 cm, the photovoltaic-module
-1 0 1 2 3 4 5 6 7 8
0
20
40
60
80
100
Photoelectric conversion efficiency(%)
The thickness of the snow(cm)
Efficiency
Figure 7. Experimental measurements with snow thicknesses of 1–6 cm.
Coatings 2023, 13, x FOR PEER REVIEW 10 of 16
(e) 5 cm
(f) 6 cm
Figure 7. Experimental measurements with snow thicknesses of 1–6 cm.
Figure 8. Impact of snow thickness on photovoltaic power generation efficiency.
3.2. Test of the Influence of Snow Slip Distance on Photovoltaic Power Generation Efficiency
The current snow-removal technology relies on the heating of snow on the surface of
the photovoltaic module to melt part of the snow. The snow water generated by the melting
plays a role in lubrication between the photovoltaic module and the snow, thus reducing
the friction coefficient between them. As a result, the snow gradually falls from the surface
of the photovoltaic module. However, in winter, the temperature fluctuates around the
freezing point most of the time, and there is often heavy wind blowing. The melted snow
water tends to freeze rapidly due to the cooling effect of wind, thus making the snow attach
tightly to the surface of the photovoltaic modules. Consequently, it is difficult to conduct
snow-removal operations. Therefore, it is particularly important to slide the snow away
from the surface of the photovoltaic modules in time. In order to faithfully simulate the im-
pact of snow on photovoltaic power generation, especially when the snow falls from the
photovoltaic panel, the impact of different sliding distances on power generation efficiency
was studied. This experiment was mainly to simulate the sliding process of snow on the
surface of photovoltaic modules. The snow was made manually, and the tilt angle of solar
cells was 45°. This experiment was very important to explore the relationship between the
sliding distance of the snow on the surface of the PV module and the power generation
efficiency of the PV module and to analyze the change characteristics of the power genera-
tion efficiency of the PV module during the sliding process. On this basis, targeted sugges-
tions are made on snow removal for photovoltaic modules in winter.
According to the influence of snow thickness on photovoltaic experimental effi-
ciency, it is known that when the snow thickness reaches 1 cm, the photovoltaic-module
-1 0 1 2 3 4 5 6 7 8
0
20
40
60
80
100
Photoelectric conversion efficiency(%)
The thickness of the snow(cm)
Efficiency
Figure 8. Impact of snow thickness on photovoltaic power generation efficiency.
3.2. Test of the Influence of Snow Slip Distance on Photovoltaic Power Generation Efficiency
The current snow-removal technology relies on the heating of snow on the surface of
the photovoltaic module to melt part of the snow. The snow water generated by the melting
plays a role in lubrication between the photovoltaic module and the snow, thus reducing
the friction coefficient between them. As a result, the snow gradually falls from the surface
of the photovoltaic module. However, in winter, the temperature fluctuates around the
freezing point most of the time, and there is often heavy wind blowing. The melted snow
Coatings 2023,13, 427 10 of 15
water tends to freeze rapidly due to the cooling effect of wind, thus making the snow
attach tightly to the surface of the photovoltaic modules. Consequently, it is difficult to
conduct snow-removal operations. Therefore, it is particularly important to slide the snow
away from the surface of the photovoltaic modules in time. In order to faithfully simulate
the impact of snow on photovoltaic power generation, especially when the snow falls
from the photovoltaic panel, the impact of different sliding distances on power generation
efficiency was studied. This experiment was mainly to simulate the sliding process of snow
on the surface of photovoltaic modules. The snow was made manually, and the tilt angle
of solar cells was 45
◦
. This experiment was very important to explore the relationship
between the sliding distance of the snow on the surface of the PV module and the power
generation efficiency of the PV module and to analyze the change characteristics of the
power generation efficiency of the PV module during the sliding process. On this basis,
targeted suggestions are made on snow removal for photovoltaic modules in winter.
According to the influence of snow thickness on photovoltaic experimental efficiency,
it is known that when the snow thickness reaches 1 cm, the photovoltaic-module power
generation efficiency decreases to 4%. Therefore, it is considered that the photovoltaic panel
cannot work normally under the condition of 1 cm of snow. Therefore, in order to facilitate
the experiment and related operations, the snow thickness of the snow slip distance on the
power generation efficiency of the photovoltaic module was set to 1 cm. Figure 9illustrates
the experimental process of snow-cover sliding on photovoltaic panels.
Coatings 2023, 13, x FOR PEER REVIEW 11 of 16
power generation efficiency decreases to 4%. Therefore, it is considered that the photovol-
taic panel cannot work normally under the condition of 1 cm of snow. Therefore, in order
to facilitate the experiment and related operations, the snow thickness of the snow slip
distance on the power generation efficiency of the photovoltaic module was set to 1 cm.
Figure 9 illustrates the experimental process of snow-cover sliding on photovoltaic panels.
94.57%
89.13%
83.70%
78.26%
72.83%
67.39%
56.25%
51.09%
45.65%
Figure 9. Cont.
Coatings 2023,13, 427 11 of 15
Coatings 2023, 13, x FOR PEER REVIEW 12 of 16
40.22%
34.78%
29.35%
13.04%
7.61%
0%
Figure 9. Experimental process of snow-cover sliding on a photovoltaic panel.
Figure 10 shows the curve of the relationship between the snow sliding distance and
the light point conversion efficiency of photovoltaic panels. In the initial stage of snow
sliding, covering the four data points of 0 cm, 5 cm, 10 cm, and 15 cm, the power genera-
tion efficiency of photovoltaic modules shows no significant change. Instead, it is main-
tained at about 4.8%. This was due to the snow covering the first group (the first longitu-
dinal row) of photovoltaic modules not being completely removed and the photovoltaic
module not being completely exposed to solar radiation. Consequently, the efficiency of
power generation remained at the same level as the photovoltaic modules that were com-
pletely covered with snow. In the experiment, under the impact of snow thickness on the
power generation efficiency of photovoltaic modules, the power generation efficiency
achieved when the snow was less than 1 cm in thickness was about 7% of that as normal.
By taking account of weather conditions and other factors, the data obtained from the two
experiments are basically consistent.
In the second stage of snow sliding, when the sliding distances were 20 cm, 25 cm, 30
cm, 35 cm, and 40 cm, the power generation efficiency of photovoltaic modules started to
improve compared with the previous stage. Due to the full exposure of the top-end pho-
tovoltaic modules, the efficiency of power generation significantly increased from 4.8% to
12.8%. In the second stage, the efficiency of power generation also improved but to an
insignificant degree, from 12.8% to 17.9%. This was due to the photovoltaic module being
composed of multiple batteries in series and parallel. When a battery is partially blocked,
its power generation efficiency is far less than that of the whole battery exposed to sun-
light. When the snow sliding distance was 40 cm, half of the photovoltaic modules re-
Figure 9. Experimental process of snow-cover sliding on a photovoltaic panel.
Figure 10 shows the curve of the relationship between the snow sliding distance and
the light point conversion efficiency of photovoltaic panels. In the initial stage of snow
sliding, covering the four data points of 0 cm, 5 cm, 10 cm, and 15 cm, the power generation
efficiency of photovoltaic modules shows no significant change. Instead, it is maintained
at about 4.8%. This was due to the snow covering the first group (the first longitudinal
row) of photovoltaic modules not being completely removed and the photovoltaic module
not being completely exposed to solar radiation. Consequently, the efficiency of power
generation remained at the same level as the photovoltaic modules that were completely
covered with snow. In the experiment, under the impact of snow thickness on the power
generation efficiency of photovoltaic modules, the power generation efficiency achieved
when the snow was less than 1 cm in thickness was about 7% of that as normal. By
taking account of weather conditions and other factors, the data obtained from the two
experiments are basically consistent.
In the second stage of snow sliding, when the sliding distances were 20 cm, 25 cm,
30 cm, 35 cm, and 40 cm, the power generation efficiency of photovoltaic modules started
to improve compared with the previous stage. Due to the full exposure of the top-end
photovoltaic modules, the efficiency of power generation significantly increased from 4.8%
to 12.8%. In the second stage, the efficiency of power generation also improved but to
an insignificant degree, from 12.8% to 17.9%. This was due to the photovoltaic module
being composed of multiple batteries in series and parallel. When a battery is partially
blocked, its power generation efficiency is far less than that of the whole battery exposed
to sunlight. When the snow sliding distance was 40 cm, half of the photovoltaic modules
remained covered with snow. Therefore, the output power was extremely limited, only
under less than 18% of the normal working condition of the power. Although the greater
the sliding distance of snow on the panel, the higher the power generation efficiency of
photovoltaic panels, the complete exposure of individual batteries within photovoltaic
panels is an important factor affecting power generation efficiency.
Coatings 2023,13, 427 12 of 15
Coatings 2023, 13, x FOR PEER REVIEW 13 of 16
mained covered with snow. Therefore, the output power was extremely limited, only un-
der less than 18% of the normal working condition of the power. Although the greater the
sliding distance of snow on the panel, the higher the power generation efficiency of pho-
tovoltaic panels, the complete exposure of individual batteries within photovoltaic panels
is an important factor affecting power generation efficiency.
In the third stage, when the sliding distances were 45 cm, 50 cm, 55 cm, 60 cm, and
65 cm, the power generation efficiency of the photovoltaic modules began to show signif-
icant improvement. When it increased from 40 cm to 45 cm, the efficiency of power gen-
eration increased from 17.9% to 21.2%, which is insignificant. This was due to when the
snow sliding distance was 40 cm, both the first and second batteries were exposed to solar
radiation and covered with the snow of a smaller thickness than 1 cm. Therefore, the im-
provement of power generation efficiency was limited. In the third stage, the power gen-
eration efficiency of the photovoltaic modules improved from 21.2% at the sliding dis-
tance of 45 cm to 31.4% at a sliding distance of 65 cm, which was twice the increase of
power generation efficiency in the second stage. This was due to more than half of the
photovoltaic modules being exposed to sunlight since the third stage. Meanwhile, the
photovoltaic modules functioning as normal outnumbered those covered with snow. As
a result, the resistance of the snow-covered PN junction to the current in the closed loop
was reduced.
In the fourth stage of snow sliding, when the sliding distance reached 70 cm, 75 cm,
80 cm, 85 cm, and 90 cm, the power generation efficiency of photovoltaic modules im-
proved significantly. When it increased from 65 cm to 70 cm, the power generation effi-
ciency improved from 31.4% to 42.3%, which is basically consistent with that in the previ-
ous process from the second stage to the third stage. This was due to all the photovoltaic
modules corresponding to this stage being basically exposed at the end of the previous
stage. As a result, there was a slight increase in the efficiency of power generation when
all the photovoltaic modules of this group were exposed. In this stage, the most significant
improvement in power generation efficiency was achieved in the whole experimental pro-
cess, with the power generation efficiency of photovoltaic modules enhanced from 42.3%
at the sliding distance of 70 cm to 100% at the sliding distance of 90 cm.
Figure 10. Relationship curve between snow slip distance and light point conversion efficiency of
photovoltaic panel.
4. Discussion
Based on the numerical simulation and experimental and analytical results, some
suggestions for improving the power generation efficiency of PV panels under snow cover
are proposed. When the thickness of snow exceeds 1 cm, it is necessary to carry out snow
020 40 60 80 100
0
20
40
60
80
100
Photovoltaic power generation efficiency(%)
Snow slip distance(cm)
Photoelectric conversion efficiency
Figure 10.
Relationship curve between snow slip distance and light point conversion efficiency of
photovoltaic panel.
In the third stage, when the sliding distances were 45 cm, 50 cm, 55 cm, 60 cm,
and
65 cm
, the power generation efficiency of the photovoltaic modules began to show
significant improvement. When it increased from 40 cm to 45 cm, the efficiency of power
generation increased from 17.9% to 21.2%, which is insignificant. This was due to when
the snow sliding distance was 40 cm, both the first and second batteries were exposed to
solar radiation and covered with the snow of a smaller thickness than 1 cm. Therefore, the
improvement of power generation efficiency was limited. In the third stage, the power
generation efficiency of the photovoltaic modules improved from 21.2% at the sliding
distance of 45 cm to 31.4% at a sliding distance of 65 cm, which was twice the increase of
power generation efficiency in the second stage. This was due to more than half of the
photovoltaic modules being exposed to sunlight since the third stage. Meanwhile, the
photovoltaic modules functioning as normal outnumbered those covered with snow. As
a result, the resistance of the snow-covered PN junction to the current in the closed loop
was reduced.
In the fourth stage of snow sliding, when the sliding distance reached 70 cm, 75 cm,
80 cm
, 85 cm, and 90 cm, the power generation efficiency of photovoltaic modules improved
significantly. When it increased from 65 cm to 70 cm, the power generation efficiency
improved from 31.4% to 42.3%, which is basically consistent with that in the previous
process from the second stage to the third stage. This was due to all the photovoltaic
modules corresponding to this stage being basically exposed at the end of the previous
stage. As a result, there was a slight increase in the efficiency of power generation when all
the photovoltaic modules of this group were exposed. In this stage, the most significant
improvement in power generation efficiency was achieved in the whole experimental
process, with the power generation efficiency of photovoltaic modules enhanced from
42.3% at the sliding distance of 70 cm to 100% at the sliding distance of 90 cm.
4. Discussion
Based on the numerical simulation and experimental and analytical results, some
suggestions for improving the power generation efficiency of PV panels under snow cover
are proposed. When the thickness of snow exceeds 1 cm, it is necessary to carry out snow
removal immediately from the surface of the photovoltaic modules, thus ensuring the
normal operation of the photovoltaic power station during the day. When the snow thick-
ness reaches 6 cm, the power generation efficiency is reduced to zero for the photovoltaic
power station, which means the operation of the station is stopped. This has a massive
impact on the normal functioning of the power grid. At this time, manual snow removal
should be considered. For large photovoltaic power stations, manual snow removal is a
Coatings 2023,13, 427 13 of 15
laborious and costly process. Therefore, in those areas with heavy snowfall, the selection of
photovoltaic modules for use in photovoltaic power stations is of much importance. When
a photovoltaic power station is under construction, the photovoltaic modules should be
installed at a certain height from the ground. This is due to when the snow is falling, there
is not enough space allowed to pile up the snow falling from the photovoltaic modules,
which hinders the snow from sliding. When it is not possible to completely clear the snow
from the photovoltaic panels, we recommend that the snow cover of the individual battery
be completely cleared.
5. Conclusions
In this paper, the effect of snow thickness on photovoltaic-module power generation
efficiency is discussed by numerical simulation. Additionally, the effect of photovoltaic-
module snow on photoelectric conversion efficiency was studied by building a test bed.
Based on the numerical simulation and experimental and analytical results, some sugges-
tions for improving the power generation efficiency of PV panels under snow cover are
proposed. On this basis, the following conclusions can be drawn:
By simulating the process of snow covering the photovoltaic modules, it is found that
the tilt angle of the photovoltaic modules affects whether the photovoltaic modules can be
easily cleared of snow. The smaller the tilt angle, the more likely the photovoltaic module
is to be covered with snow, hence the greater the amount of snow accumulation and the
larger the snow thickness.
Through the experiment on how snow thickness impacts on the power generation
efficiency of photovoltaic modules, it is discovered that the thickness of snow directly affects
the power generation efficiency of photovoltaic modules. This is due to the reflection-of-
snow-to-solar-radiation being only related to the reflectivity of the surface of snow. When
the thickness of snow increases, the amount of snow staying on the photovoltaic module
increases. In this case, the absorbed solar radiation increases, thus reducing the amount
of radiation reaching the surface of the photovoltaic module. When the snow thickness
reaches 1 cm, the power generation efficiency of the entire photovoltaic module reduces
to 7.1% of that as normal. When the snow thickness reaches 6 cm, the power generation
capacity of the photovoltaic module is zeroed, which means it does not function at all.
The sliding of snow on the photovoltaic panel is beneficial to enhance the efficiency of
photoelectric conversion. Although the greater the sliding distance of snow on the panel,
the higher the power generation efficiency of photovoltaic panels, the complete exposure
of the individual battery within photovoltaic panels is an important factor affecting power
generation efficiency.
In this paper, the characteristics of photovoltaic cells are not fully considered when
studying the snow accumulation process of solar photovoltaic cells, and the variable of
sliding angle is not considered when studying the snow removal on the surface of solar
cells. Therefore, in the next study, we will test the energy generation and solar radiation
of solar cells to further evaluate the efficiency of solar cells. We will compare and study
the I–V curve of solar cells under normal conditions and coverage conditions. In addition,
for the snow-removal phenomenon on the surface of solar cells, we will add the solar-cell
tilt angle as a variable to illustrate the impact of different angles on the sliding speed and
power generation.
Author Contributions:
Conceptualization, Z.Q., C.Z. and W.Z.; methodology, Z.Q.; software, C.Z.;
validation, H.L. and W.Z.; formal analysis, Z.Q. and F.A.; investigation, W.Z.; resources, Z.Q. and F.A.;
data curation, H.L.; writing—original draft preparation, Z.Q., C.Z. and W.Z.; writing—review and
editing, C.Z., Y.X. and J.Q.; visualization, C.Z.; supervision, H.L.; project administration, H.L.; funding
acquisition, H.L. All authors have read and agreed to the published version of the manuscript.
Funding:
The authors appreciate the financial supports provided by the National Oversea High-
level Talents Program of China, the National Natural Science Foundation of China (No. 52266017),
and the Major Project of the National Social Science Foundation of China (No. 21&ZD133). This
Coatings 2023,13, 427 14 of 15
study was also supported by the Xinjiang Natural Science Fund for Distinguished Young Scholars
(No. 2021D01E08), the Xinjiang Regional Coordination Special Project-International Science and
Technology Cooperation Program (No. 2022E01026), the Xinjiang Major Science and Technology
Special Project (No. 2022401002-2,2022A01007-1,2022A01007-4), the Xinjiang Key Research and
development Project (No. 2022B03028-2, No. 2022B01033-2, and No. 2022B01022-1), the Central
Guidance on Local Science and Technology Development Project (No. ZYYD2022C16), the Innovation
Team Project of Xinjiang University (No. 500122006021), the High-level Talents Project of Xinjiang
University (No. 100521001), the Outstanding doctoral student research innovation Project of Xinjiang
University (No. XJU2022BS100).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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