ArticlePDF Available

Solar Panels Cleaning Frequency for Maximum Financial Profit

Authors:

Abstract

Allowing the dust to accumulate on solar panels without adequate cleaning leads to huge monetary losses. Proper judgment of when to call for washing of solar panels is a compromise between gross costs of cleaning the panels and how much reduction in efficiency of solar panels can be tolerated. In this paper, we derive a formula for the optimal number of days between cleaning cycles of a solar array by minimizing the cost of cleaning the array and the lost revenue from the unclean panels. The formula will aid in deciding cleaning periods based on the environment in which the solar panels are installed and cost incurred from undertaking the washing process.
Open Journal of Energy Efficiency, 2017, 6, 80-86
http://www.scirp.org/journal/ojee
ISSN Online: 2169-2645
ISSN Print: 2169-2637
DOI:
10.4236/ojee.2017.63006 Aug. 11, 2017 80 Open Journal of Energy Efficiency
Solar Panels Cleaning Frequency for Maximum
Financial Profit
Mohammad Abu-Naser
Electrical Engineering Department, Philadelphia University, Amman, Jordan
Abstract
Allowing the dust to accumulate on solar panels without adequate cleaning
leads to huge monetary losses. Proper judgment of
when to call for washing of
solar panels is a compromise between gross costs of cleaning the panels and
how much reduction in efficiency of solar panels can be tolerated. In this p
a-
per,
we derive a formula for the optimal number of days between cleaning
cycles of a solar array by minimizing the cost of cleaning the array and the lost
revenue from the unclean panels. The formula will aid in deciding cleaning
periods based on the environme
nt in which the solar panels are installed and
cost incurred from undertaking the washing process.
Keywords
Dust Deposition, PV Efficiency Degradation, Optimal Cleaning Cycle
1. Introduction
There is an established body of literature on the effect of dust on solar panel
performance and efficiency. However, the literature on the frequency of cleaning
solar panels from accumulated dust is limited.
One of the first rigorous experimental studies on the effect of dust on the I-V
characteristic curve was conducted by El-Shobokshy [1]. They studied the effect
of dust deposition on the reduction of solar intensity and the power output of
the solar panel. Although the experimental procedure was very robust to under-
stand the ramifications of dust accumulation on solar panel efficiency, the re-
sults drawn were for a specific solar panel type which was used in the labora-
tory.
To understand the process of dust particles accumulation on glaze surfaces at
the microscopic level, Al-Hasan [2] made a theoretical analysis on the trans-
How to cite this paper:
Abu-Naser, M.
(201
7)
Solar Panels Cleaning Frequency for
Maximum Financial Profit
.
Open Journal
of Energy Efficiency
,
6
, 80-86.
https://doi.org/10.4236/ojee.2017.63006
Received:
March 23, 2017
Accepted:
August 8, 2017
Published:
August 11, 2017
Copyright © 201
7 by author and
Scientific
Research Publishing Inc.
This work is licensed under the Creative
Commons Attribution International
License (CC BY
4.0).
http://creativecommons.org/licenses/by/4.0/
Open Access
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 81 Open Journal of Energy Efficiency
mittance of light through a layer of sand particles accumulated on the surface of
a photovoltaic panel. A mathematical relation was derived which relates trans-
mittance coefficient to the number of sand particles deposited on the surface.
In [3] an experimental study was performed on the relation between dust
accumulation and the tilt angle of the panel where horizontal panels caught the
most deposition of fine and coarse particles whereas vertical panels caught the
fine particles of dust only. Tilt angle effect on dust deposition has been further
studied in [4] and a regression-based model of the relationship between output
power and sand particle size and irradiance was derived.
In [5] performance degradation due to deposition of different types of sand
particles is investigated and a theoretical model is developed that is able to si-
mulate the dust deposition impact on the energy behavior of solar photovoltaic
(PV).
To our knowledge [6] is the only reference that suggests cleaning cycles for
different regions. However, the paper only provides guidelines for cleaning the
panels when installed in different climatic zones and based on the weather and
dust activity level. Our approach is different in that it is based on a quantitative
analysis of dust and hence yields optimal results compared to the cleaning cycles
suggested in [6] which are based on qualitative understanding of dust activities.
2. Derivation of the Optimal Number of Days between
Cleaning Cycles
The effect of sand dust particles accumulation on light transmittance coefficient
is investigated mathematically and experimentally in [2]. A transmittance coef-
ficient of 0 means the light beam did not pass and that it has been completely
reflected or absorbed while a coefficient of 1 means light has passed completely
without attenuation. The relation between transmittance coefficient (
τ
) and
number of particles accumulated (
n
) has been derived as [2]
2
1π
e
nQ r
τ
= −
(1)
where
is the radius of the sand particle and
e
Q
is the particle extinction
efficiency which has been assumed to be equal to 2 since the sand dust particles
settle on the surface of the glass of the photovoltaic panel far away, in com-
parison to the size of dust particles, from where the light is detected by the
photovoltaic cells. This relation is linear with transmittance decreasing with
more sand dust particles settling on the surface. In [2] a comparison between
this mathematical derivation and experimental observation shows good agree-
ment for light transmittance values in the range 0.5 to 1. For transmittance
coefficients below 0.5 the relation observed starts to deviate from the linear
relationship and becoming more nonlinear. However, in practice to maintain the
efficiency of the photovoltaic panels, the cleaning of panels should be performed
before transmittance coefficient falls to such low values. So in our derivation of
the optimal solar panel cleaning cycle, the relation between efficiency and the
amount of dust accumulation will be assumed to be linear without much loss of
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 82 Open Journal of Energy Efficiency
accuracy.
Dust accumulation on the surface of the solar panels will cause the efficiency
of the solar panel to decrement from its nominal value. So
nominal
η γη
=
(2)
and
1N
γα
= −
(3)
where
α
is the average daily losses in solar conversion efficiency due to dust
and
N
is number of days between cleaning cycles. So the financial loss due to
power degradation as a result of dust accumulation on the PV system for
N
consecutive days is
( )
123 N si
αβ
+++ +
(4)
where
is the average sun hours per day,
i
is the capacity of installed PV
system, and
β
is the price of kWh.
So the financial loss due to power degradation as a result of dust accumulation
per annum is
( )
1
365 123C N si
N
αβ
= +++ +
(5)
( )
365 12
N
N si
N
αβ
= +
(6)
()
365 1
2N si
αβ
= +
(7)
and if
P
is the cost of cleaning solar array, then the cost of cleaning the panels
per annum is
2
365 .CP
N
=
(8)
So the total cost is
12
JCC= +
(9)
( )
365 365
1.
2N si P
N
αβ
=++
(10)
Finding the optimal number of days between cleaning cycles is achieved by
minimizing
J
with respect to
N
ˆarg min .
N
NJ
=
(11)
So
2
d 365 365 0,
d2
J si P
NN
αβ
= −=
(12)
or
2
2
ˆ,
P
Nsi
αβ
=
(13)
or
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 83 Open Journal of Energy Efficiency
2
ˆ.
P
Nsi
αβ
=
(14)
3. Determination of Parameter Values
3.1. Average Daily Loss in Solar Conversion Efficiency
The factors that affect rate of dust deposition on PV panels are the concentration
of airborne dust particles, wind speed, and relative humidity. It was reported in
[7] that the higher the concentration of dust particles in the air, the higher the
rate of dust deposition on the PV panels. Also relative humidity is positively
correlated with rate of dust deposition since the dust particles become stickier in
humid weather. On the contrary, wind speed was negatively correlated with dust
deposition since higher wind speed aid in the removing of dust particles from
the surface of the solar panels. These three factors differ from region to region
and hence will affect the average daily loss in solar conversion efficiency in the
region. For example, in California the average daily loss in solar conversion
efficiency was 0.051% [8]. In Santiago, Chile the values ranged from 0.14% to
0.56% depending on the season and pollution level [9]. In the middle east, the
values are high as well due to dusty weather conditions. For example, in Qatar
the average daily loss in solar conversion efficiency could be as high as 0.55%
[7].
3.2. Cleaning Cost
The process of cleaning the solar array should be performed by professional
cleaner. The cost of cleaning include the cost of materials used in the cleaning
process plus labor cost [10]. The cost will vary from case to case depending on
the soiling type and country where the PV system is installed [11]. In the middle
east region, for example, the soiling of panels is mainly due to dust accumulation
and hence cleaning can be performed relatively easy with basic tools, water, and
some cleaning chemicals. In cases where other types of dirts exit such as bird
dropping or extra pollution, the cleaning process may involve more cost and
labor.
Depending on the cost of cleaning and the level of dust accumulation, the
cleaning operation may be justified or it may not be justified. In a study by
Tanesab
et al.
[12], it was found that cleaning cost of PV panels installed in Perth,
Western Australia will be much higher than loss caused by dust and hence
cleaning is not justified. So the system operator can rely on natural cleaning such
as rain and wind to clean the panels. In another study by Stridh [13] in three
locations in Europe: Murcia in spain, Munich in Germany, and Stockholm in
Sweden, it was concluded that cleaning is justified in Murcia, and to some degree
in Munich, but not justified for Stockholm.
4. Results and Discussion
The following is a hypothetical example that shows how the result of the paper
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 84 Open Journal of Energy Efficiency
appearing in Equation (14) can be used. The parameter values used are typical
for the middle east in general. Note that the cleaning cost of the 1 MW array
which is $250 is relatively small compared to other countries. This is due to the
fact that the type of soiling predominant in the middle east is sand which does
not require much material or labor in order to be cleaned.
Example 1.
A
1
MW solar PV system is subjected to dust accumulation that
causes an average daily loss in solar conversion efficiency of
0.002.
If the PV
system receives an average of
5
sun hours per day, the price of
1 kWh
is
$0.1,
and the cost of cleaning a solar array is
$250.
How often should the solar array
be cleaned to maximize the gain
?
2 250
ˆ500 22 days.
0.002 5 1000 0.1
N×
= = ≈
×× ×
(15)
Remarks:
Our derivation is based on the assumption that dust accumulation is linearly
increasing with time. However, the climatological system is more complex
and the linear assumption can work most of the time as an approximation
only. Two special climatological events should be observed: rainfall and sand
storms. Rainfall event will aid in cleaning the solar panels while sand storms
will accumulate huge amounts of dust on the panels and cleaning should be
usually performed after such event. Also it should be noted that in dry
regions dust removal can occur naturally when wind blows on dusty solar
panels which will further aid in the cleaning of the panels. Based on these
different scenarios, our result is expected to be conservative in maintaining
the solar panels clean.
To compare the result of this paper to the approach followed in the literature
by the scientific community thus far [10], we find that it will take almost 22
days till the cost due to lack of energy production becomes 250 dollars. And it
is at this instant when the cleaning of the panels should be performed.
However, this coincidence will not necessarily hold true if dust accumulation
is not a linear function of time.
The optimal number of days between cleaning cycles depends on a number
of factors;
1)
P
: the cost of cleaning solar array in units of $,
2)
α
: the average daily losses in solar conversion efficiency due to dust in
units of day−1,
3)
s
: average sun hours per day in units of hours/day,
4)
i
: capacity of installed PV system in units of kW,
5)
β
: price of 1 kWh of electricity in units of $/kWh.
Note that the multiplication of the last four factors (
si
αβ
) which appears in
the denominator of (14) represents the decremental daily loss in revenue due to
dust accumulation on the PV panels in units of $/day/day.
This paper is considered as first attempt toward making decisions about
cleaning solar panels based on quantitative analysis. Generally these decisions
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 85 Open Journal of Energy Efficiency
are made based on understanding the environment in which the solar panels
are installed which might not be the best decision made. We believe further
studies on the effect of dust on solar panel efficiency should be performed on
a region by region bases similar to the studies performed in [8] and [14] for
California region.
5. Conclusion
From economic perspective, solar panels should be regularly cleaned to improve
the efficiency and maximize gain. However, cleaning process incurs a cost and
could not be performed very frequently. Here we show a mathematical result
that maximizes the gain from the solar array. The main result of the paper
appearing in (14) was based on minimizing the cost function (9). Adopting this
cost function is the correct approach to find the optimal number of days between
cleaning cycles. And it is more appropriate than the approach followed in the
literature by the scientific community thus far which is based on comparing the
cleaning cost to the cost due to lack of energy production due to dust, and it is at
the instant when these two costs become the same the cleaning activity should be
performed.
References
[1] El-Shobokshy, M.S. and Hussein, F.M. (1993) Degradation of Photovoltaic Cell
Performance Due to Dust Deposition on to Its Surface.
Renewable Energy
, 3, 585-
590. https://doi.org/10.1016/0960-1481(93)90064-N
[2] Al-Hasan, A.Y. (1998) A New Correlation for Direct Beam Solar Radiation Received
by Photovoltaic Panel with Sand Dust Accumulated on Its Surface.
Solar Energy
, 63,
323-333. https://doi.org/10.1016/S0038-092X(98)00060-7
[3] Hegazy, A.A. (2001) Effect of Dust Accumulation on Solar Transmittance through
Glass Covers of Plate-Type Collectors.
Renewable Energy
, 22, 525-540.
https://doi.org/10.1016/S0960-1481(00)00093-8
[4] Mani, F., Pulipaka, S. and Kumar, R. (2016) Characterization of Power Losses of a
Soiled PV Panel in Shekhawati Region of India.
Solar Energy
, 131, 96-106.
https://doi.org/10.1016/j.solener.2016.02.033
[5] Kaldellis, J.K. and Kapsali, M. (2011) Simulating the Dust Effect on the Energy Per-
formance of Photovoltaic Generators Based on Experimental Measurements.
Ener-
gy
, 36, 5154-5161. https://doi.org/10.1016/j.energy.2011.06.018
[6] Mani, M. and Pillai, R. (2010) Impact of Dust on Solar Photovoltaic (PV) Perfor-
mance: Research Status, Challenges and Recommendations.
Renewable and Sus-
tainable Energy Reviews
, 14, 3124-3131. https://doi.org/10.1016/j.rser.2010.07.065
[7] Javed, W., Guo, B., Wubulikasimu, Y. and Figgis, B.W. Photovoltaic Performance
Degradation Due to Soiling and Characterization of the Accumulated Dust.
[8] Mejia, F.A. and Kleissl, J. (2013) Soiling Losses for Solar Photovoltaic Systems in
California.
Solar Energy
, 95, 357-363. https://doi.org/10.1016/j.solener.2013.06.028
[9] Urrejola, E., Antonanzas, J., Ayala, P., Salgado, M., Ramrez-Sagner, G., Corts, C.,
Pino, A. and Escobar, R. (2016) Effect of Soiling and Sunlight Exposure on the Per-
formance Ratio of Photovoltaic Technologies in Santiago, Chile.
Energy Conversion
and Management
, 114, 338-347. https://doi.org/10.1016/j.enconman.2016.02.016
M. Abu-Naser
DOI:
10.4236/ojee.2017.63006 86 Open Journal of Energy Efficiency
[10] Faifer, M., Lazzaroni, M. and Toscani, S. (2014) Dust Effects on the PV Plant Effi-
ciency: A New Monitoring Strategy.
Proceedings of the
20
th IMEKO TC
4
Interna-
tional Symposium and 18th International Workshop on ADC Modelling and Test-
ing
, Benevento, 580-585.
[11] Pavan, A.M., Mellit, A. and De Pieri, D. (2011) The Effect of Soiling on Energy
Production for Large-Scale Photovoltaic Plants.
Solar Energy
, 85, 1128-1136.
https://doi.org/10.1016/j.solener.2011.03.006
[12] Tanesab, J., Parlevliet, D., Whale, J. and Urmee, T. (2016) Dust Effect and Its Eco-
nomic Analysis on PV Modules Deployed in a Temperate Climate Zone.
Proceed-
ings of the
3
rd International Conference on Power and Energy Systems Engineer-
ing
, Kitakyushu, 65-68. https://doi.org/10.1016/j.egypro.2016.10.154
[13] Stridh, B. (2012) Economical Benefit of Cleaning of Soiling and Snow Evaluated for
PV Plants at Three Locations in Europe.
Proceedings of the
27
th European Photo-
voltaic Solar Energy Conference and Exhibition
, Frankfurt, 4027-4029.
[14] Kimber, A., Mitchell, L., Nogradi, S. and Wenger, H. (2006) The Effect of Soiling on
Large Grid-Connected Photovoltaic Systems in California and the Southwest Re-
gion of the United States.
Proceedings of the
4
th IEEE World Conference on Pho-
tovoltaic Energy Conference
, Waikoloa, 2391-2395.
https://doi.org/10.1109/WCPEC.2006.279690
Submit or recommend next manuscript to SCIRP and we will provide best
service for you:
Accepting pre-submission inquiries through Email, Facebook, LinkedIn, Twitter, etc.
A wide selection of journals (inclusive of 9 subjects, more than 200 journals)
Providing 24-hour high-quality service
User-friendly online submission system
Fair and swift peer-review system
Efficient typesetting and proofreading procedure
Display of the result of downloads and visits, as well as the number of cited articles
Maximum dissemination of your research work
Submit your manuscript at: http://papersubmission.scirp.org/
Or contact ojee@scirp.org
... The major concern for surface cleaning applications is identifying cost-effective and sustainable operations without degrading the optical, morphological, and mechanical properties of the surfaces. Regular cleaning of the device surfaces, such as photovoltaics and solar concentrated troughs, significantly improves the device output power and efficiency [11], although the self-cleaning processes require external efforts, such as electrical or mechanical power. Self-cleaning methods adopt mechanisms mimicking nature, such as the water repellency of lotus leaves, rose petals, and rice rusks, and they have several advantages over the other methods in terms of cost and sustainability [11]. ...
... Regular cleaning of the device surfaces, such as photovoltaics and solar concentrated troughs, significantly improves the device output power and efficiency [11], although the self-cleaning processes require external efforts, such as electrical or mechanical power. Self-cleaning methods adopt mechanisms mimicking nature, such as the water repellency of lotus leaves, rose petals, and rice rusks, and they have several advantages over the other methods in terms of cost and sustainability [11]. In self-cleaning applications, the surface characteristics are created while imitating nature; the wetting state of the surface is modified to be hydrophobic, self-repelling the particles on surfaces. ...
... However, large size droplets undergo wobbling/puddling during rolling/sliding on the surfaces because of the dynamically changing retention forces and gravitational influence. The droplet mass center also changes for wobbling droplets while affecting the droplet inertia and acceleration [11]. The potential energy of the deformed droplet, due to puddling, differs from that of the spherical droplet by a factor of ρgR 3 , and the three-phase contact line of the deformed droplet (l) is in the ...
Article
Environmental dust mitigation from hydrophobic surfaces by rolling water droplets is considered and the dust particle removal mechanism by rolling droplet fluid is examined. The dust particles are analyzed evaluating elemental composition, shapes, and sizes. The solubility of some dust compounds in the droplet fluid is also assessed. Glass surfaces are hydrophobized through deposition of the functionalized nano-size silica particles using the dip coating method. A high speed recording system is utilized monitoring and tracking of the droplet liquid infusion (cloaking) on the dust particle surfaces. Similarly, the droplet motion on the inclined dusty hydrophobic surface is monitored and tracked. The findings reveal that dust possess various elements and alkaline and alkaline earth metal compounds can dissolve in water while forming a chemically active solution, which can damage the dusty surfaces. The droplet liquid infusion (cloaking) on the surface of the dust particles remains essential for removing dust from the hydrophobic surfaces by rolling water droplets. The droplet liquid spreading ceases for low surface energy dust particles. This prevents the droplet fluid spreading onto the surface of the dust particles; hence, these particles remain as dust residues on the surface. Rolling water droplet cleans the dusty hydrophobic surface and improves the optical transmittance of the surface.
... Optimisation of the cleaning procedure is a necessity and this involves finding a balance between the cost of cleaning and the cost of not cleaning [21]. While periodic cleaning is justified, too frequent cleaning intervals result in huge financial losses while too long periods between cleaning intervals result in huge energy losses [22]. ...
... The results showed that cleaning was not necessary for panels with 20 o tilt angle or higher. A generic study for the Middle East by Abu-Naser [21] employed quantitative analysis in optimising the cleaning frequency of a hypothetical 1MW solar power plant. The results showed that the optimal number of days between successive cleaning intervals is 22 days. ...
... It was further concluded that the study can be employed anywhere within the Middle East region. Karkee and Khadka [22] further developed the same model by Abu-Naser [21] and introduced absolute hourly loss in conversion efficiency and optimised the cleaning frequency to minimise financial losses and also to reduce the payback period. In a study in Pakistan, Ullah et al. [23] worked on optimising the cleaning schedule for PV modules in Lahore, Pakistan. ...
Article
Full-text available
Soiling is a major issue that can be a drawback to the wider deployment of solar photovoltaic systems. In this study, the influence of soiling on energy loss in Muzarabani, Zimbabwe was investigated. The daily and monthly variations in energy generated and soiling were also studied. An empirical soiling loss model was developed based on the experimental studies. It was revealed that soiling is not uniform with each passing day but rather depends on the daily differences in weather conditions. Soiling was observed to be high during the period from July to November and was less in May and June. Particle Swarm Optimisation was employed to minimise the number of days between cleaning events. Cleaning was found to be necessary every 15 days to minimise the losses due to both frequent cleaning as well as losses caused by not cleaning the panels.
... Second, the method of cleaning, where the safety for both humans and panels should be taken into account. Moreover, the cleaning process itself is kept simple and efficient, and, naturally, there is rainfall, gravity, and wind speed that can help in the cleaning process [4,[79][80][81]. ...
Article
Full-text available
The performance of photovoltaic (PV) solar panels is dependent on certain factors, such as dust effects. Even though Palestine’s energy issues are well-known, no research has been undertaken on the soiling effect on solar energy generation in Palestine’s climatic circumstances. The study’s findings can aid Palestine’s efforts to achieve long-term energy sustainability and solar energy use. Outdoor research was conducted in Tulkarm, Palestine, to explore the impact of dust on PV systems. The current study examined the impact of dust accumulation based on the Mediterranean climate. To accomplish this, a one-year experiment was conducted from 1 January to 31 December 2021. An 85-kW PV power plant at Tulkarm was utilized in the study. Knowing the efficiency reduction over time will aid in minimizing cleaning expenses by selecting the most appropriate cleaning interval. The results concluded that in January, February, November, and December, there will be a two-month cleaning period, monthly cleaning in March and October, as well as two weeks of cleaning in April and May. It may also be concluded that the plant should be cleaned weekly throughout the months of June, July, August, and September. This recommendation is necessary to maintain the PV panel plant operating at peak efficiency.
... A study conducted in Perth, Western Australia suggests that cleaning cost is higher than the loss caused by the dust accumulation [10]. Such a system can rely on natural cleaning such as wind and heavy rain [11]. However, a weak rainfall makes the dust accumulation even worse as it was found in Jazan, Saudi Arabia [12]. ...
Technical Report
Full-text available
This paper studies the effectiveness of the downward thrust of the drone created due to its cruise at certain height above the ground to remove the dust from photovoltaic (PV) panel and enhance its energy output. In the Kingdom, the sandstorms are quite frequent and cause dust accumulation on the exposed surfaces in general and in the present case on panel surfaces. As a result of which the solar radiation energy absorption decreases and causes decrease in the energy output of the panels. The present effort aims at reducing the dust accumulation on PV panels by flying the drone above these panels at certain height and time interval. The experimental investigation conducted three types of drone movements (horizontal, vertical and diagonal) and recorded the output energy from the panel in each scenario to find out the optimal path for maximum dust removal. The tests were conducted at King Fahd University of Petroleum and Minerals (KFUPM) beach, Dhahran, Saudi Arabia by loading the panels uniformly with 20, 50 and 100ml volume of dust. The results showed that the horizontal path is the best overall, then the diagonal but performs worse at 20 ml, and finally the vertical path has overall lowest results and very low efficiency at high volumes, which is unwanted in dusty areas such as Saudi Arabia.
... Both quantitative and qualitative methods are applied to understand the deposition of dust particles over the PV surface in various climates and PV tilts [10,13]. The effects of tilt angle on the deposition of dust particles on the PV panel front surface and the relationship between output power, dust particle size, and irradiance were studied experimentally and mathematically [14,15]. ...
Article
Full-text available
Dust accumulation on the photovoltaic (PV) surface decreases the solar radiation penetration to the PV cells and, eventually, the power production from the PV system. To prevent dust-based power losses, PV systems require frequent cleaning, the frequency of which depends on the geographical location, PV integration scheme, and scale of the PV power plant. This study aims to measure the drop-in radiation intensity, as well as power output, due to dust and to determine the optimal time interval for PV cleaning in the United Arab Emirates (UAE) climate. In this research, a dusting study experiment was carried out at the Renewable Energy Laboratory, Falaj Hazza Campus, UAE University, Al Ain, UAE, for 3.5 months, from 22 April 2018 to 7 August 2018. To measure the pure radiation losses caused by the dust, four transparent glasses were used to mimic the top glass cover of the PV modules. The dusting induced power losses were measured for four selected PV cleaning frequencies (10 days, 20 days, 1 month, and 3 months). This study revealed that up to 13% of power losses occurred in PV panels that remained dusty for 3 months, compared to panels that were cleaned daily. PV cleaning after 15 days brought the losses down to 4%, which was found the most feasible time for PV cleaning in this study, considering a reasonable balance between the cleaning cost and energy wasted due to soiling.
... Finally, the influence of rain, RH, and ambient PM concentrations is considered. This comprehensive study looks to address gaps in regional soiling knowledge to allow energy producers to make more informed management decisions regarding mitigation of soiling (Tanesab et al., 2018;Baras et al., 2016;Abu-Naser, 2017;Dolan et al., 2015;Jones et al., 2016). ...
Article
Deposition of particulate matter (PM) onto solar photovoltaic (PV) panels - known as soiling - has been estimated to reduce energy production by 10–40% in many regions of the world. Despite this, many key properties including soiling rates, PM source contributions, physical and optical properties of the deposited particles, and the impact of rain and relative humidity (RH) are not well understood. With this in mind we conducted a field study in Gandhinagar, India. Our approach combines soiling monitoring with a reference station and a low-cost digital microscopy system, sample collection for mass loading information, glass sample slides for size resolved soiling impacts, and monitoring of rain, RH, and panel temperature for insight into meteorological impacts on cleaning and soiling rates. Results indicate soiling reduces PV energy production by 0.37 ± 0.09% day⁻¹. The low cost (<100$) digital microscope estimated soiling within ~1% of measured losses, confirming the feasibility of this low-cost alternative to expensive soiling stations. Deposited PM decreased energy production by 5.12 ± 0.55% per PM mass loading (g m⁻²). Microscopy analyses of field samples revealed that > 90% of deposited mass loading is from particles > 5 µm in diameter, with > 50% of the soiling impacts estimated to be from particles < 5 µm. While heavy rain cleaned PV panels, light rains and high RH contributed to a 2x soiling rate and 5-10x PM deposition velocities as compared to dry periods.
Article
This review provides a comprehensive, detailed description and contextualization of soiling research evolution in the solar energy field throughout time. The analysis consists of past soiling research, including important notes on notable works and main researches. The current state of the art is presented, followed by an extended literature survey covering from 1942 to 2019, facilitating the finding of primordial research concerning each of the available technologies, and enriching knowledge regarding the existing extensive research database. Moreover, soiling analysis and comments are made for several specific topics, such as cleaning techniques and environmental effects on soiling deposition. Finally, future prospects and research directions on the soiling effect are given.
Article
Full-text available
Solar panels are susceptible to dust accumulation on their surface for long term operation. Scheduled cleaning work is thus important to maintain the efficiency and reliability of the solar panel for producing electricity. The paper presents a preliminary design of the cleaning mechanism for the solar panel surface using a semiautomatic wiper control system. A DC motor is utilized to power the wiper. The amount of water is sprayed over the solar panel surface, while the wiper is moving back and forth. The manual switch buttons are used to control the rotation direction of the DC motor. The experimental tests are conducted to obtain the solar panel performance, namely output voltage, output current, output power, and panel efficiency under clean and dusty conditions. The comparison of both conditions has been made to determine the cleaning effectiveness of the proposed prototype. The test results show that the wiper swept repetition of 10, 20, and 30 times delivers 57.0 percent, 79.1 percent, and 86.7 percent of the performance of the initial clean surface condition, respectively.
Article
Full-text available
The aim of this study is to investigate the effect of dust on the degradation of PV modules deployed in a temperate climate region, Perth, Western Australia. Results revealed that PV performance, quantified by normalised maximum power output, varied with season. For a one-year period of study, over which the only cleaning activities were due to wind and rain, the performance of PV modules deployed in Perth, decreased at the end of summer and spring, tended to increase at the end of autumn and reached their peaks at the end of the winter season. Assuming the effect of dust on Pmax output is similar among the PV modules and is linear among the consecutive seasons, economic analysis indicated that the total cost of production losses of 13 polycristalline silicone PV modules caused by dust (A$ 5.47) is lower than total cleaning cost (A$ 78). Therefore, no cleaning procedure is recommended for the grid-connected PV system simulated in the case study.
Conference Paper
Full-text available
The objective of this study was to determine the daily loss of energy output caused by dust accumulation on photovoltaic (PV) modules, to quantify the dust accumulation rate on PV panels and to determine the physicochemical properties of dust accumulated on PV panels, and their relations to soiling-induced PV performance and environmental conditions. Averaged over the one-year study period, the PV performance loss due to soiling was-0.52% per day for modules cleaned every sixth month, and-0.55% per day for modules cleaned every second month, in terms of a " cleanness index " (CI). The average dust accumulation rate (DAR) was found to be 260 ±100 mg m-2 day-1 , with the winter values higher than the summer ones. The DAR was significantly correlated with dust concentration (PM10), wind speed and relative humidity. A significant negative correlation was also found between daily ∆CI and DAR. On average, very 100 mg m-2 dust loading led to a ∆CI of-0.5%. Particle size analysis showed that 90 percent of the dust (by volume) was composed of particles less than 36 μm. The mean and median particle size (by volume) was approximate 18 and 14 μm, respectively. Chemical analysis showed that the dust mainly consisted of calcium, silicon, iron, magnesium and aluminum, and calcite, dolomite, and quartz being the dominant mineral forms in dust accumulated on PV panels.
Article
Full-text available
Soiling is the accumulation of dust on solar panels that causes a decrease in the solar photovoltaic (PV) system’s efficiency. The changes in conversion efficiency of 186 residential and commercial PV sites were quantified during dry periods over the course of 2010 with respect to rain events observed at nearby weather stations and using satellite solar resource data. Soiling losses averaged 0.051% per day overall and 26% of the sites had losses greater than 0.1% per day. Sites with small tilt angles (<5°) had larger soiling losses while differences by region were not statistically significant.
Conference Paper
As well known dust deposition on PV panels results in a decrease of the electrical power produced by the panel/photovoltaic system. In order to assess this decrease and carry out a long-term economic analysis, it is desirable to make an accurate prediction of the efficiency of the system and of the maintenance costs. Starting from this assumption, an economic model that takes into account the relationship between the losses in the energy production and the cost of maintenance is very useful. In this paper the losses due to the dust will be evaluated considering radiation data provided by public meteorological stations installed which are few kilometers far from the considered PV system.
Article
This paper introduces a model that quantifies the relationship between power output, incident irradiance and soil particle size composition of soiled photovoltaic panels. Soil samples used in artificial soiling experiments were collected from Shekhawati region in India and their relative percentage of standard particle sizes is determined from sieve analysis. A non-linear relationship between irradiance and power is obtained using regression analysis showing the effect of particle size composition present on the panel. Further, the tilt angle for maximum power extraction is determined for each soiled panel and the deviation from the optimum tilt angle of a clean panel is observed. It is concluded that, when the soil present on the panel is rich in the particles with diameter (75 μm and below), the deviation from the tilt angle of a clean panel is 4°, however if the soil contains higher composition of both 150 μm and 300 μm particle sizes the deviation is 8°.
Conference Paper
Energy loss due to soiling is one of the most important factors than can be influenced by the operator during the life of a PV plant. Snow cover can be seen as a special case of soiling applicable in countries with colder climate. A break-even analysis between energy loss due to soiling and cleaning cost was conducted for a 1 MW plant by modeling with PVsyst for three different European locations, considering both fixed tilt angle and with 2-axis tracking. As basis for net present value calculations feed-in tariffs, consumer price or spot price for electricity was used.
Article
One of the least analyzed side effects of atmospheric air pollution is the degradation of PV-panels’ performance due to the deposition of solid particles varying in composition, size and type. In the current study, the experimental data concerning the effect of three representative air pollutants (i.e. red soil, limestone and carbonaceous fly-ash particles) on the energy performance of PV installations are analyzed. According to the results obtained, a considerable reduction of PVs’ energy performance is recorded, depending strongly on particles’ composition and source. Subsequently, a theoretical model has been developed in order to be used as an analytical tool for obtaining reliable results concerning the expected effect of regional air pollution on PVs’ performance. Furthermore, experimental results concerning the dust effect on PVs’ energy yield in an aggravated – from air pollution – urban environment are used to validate the proposed theoretical model.
Article
This work aims to evaluate the effect of soiling on energy production for large-scale ground mounted photovoltaic plants in the countryside of southern Italy. Since the effect of pollution can seriously compromise the yield of solar parks, the results obtained in this study can help the operation and maintenance responsible in choosing the proper washing schedule and method for their plants and avoid wasting money. In order to determine the losses due to the dirt accumulated on photovoltaic modules, the performances at Standard Test Conditions (STC – Irradiance: 1000W/m2; Cell temperature: 25°C; Solar spectrum: AM 1.5) of two 1MWp solar parks before and after a complete clean-up of their photovoltaic modules have been compared. The performances at STC of the two plants have been determined by using a well-known regression model that accepts as an input two climate data (the in-plane global irradiance and the photovoltaic module temperature), while the output results in one electrical parameter (the produced power). A regression model has been preferred to a common performance ratio analysis because this latter is too much influenced by the seasonal variation in temperature and by the plant availability. The results presented in this work show that both the soil type and the washing technique influence the losses due to the pollution. A 6.9% of losses for the plant built on a sandy soil and a 1.1% for the one built on a more compact soil have been found. Finally, these results have been used in order to compare the washing costs with the incomings due to the performance improvement.
Article
The effects of dust accumulation on the surface of photovoltaic cells were experimentally investigated. The dust used in this study was prepared in the laboratory from known materials, then examined under an optical microscope to determine the size distribution of the particles. The two main parameters of the size distribution were determined, namely, the mean diameter and the standard deviation. A solar simulator consisting of halogen lamps was used to carry out controlled experiments. The dust particles were dispersed uniformly over the test photovoltaic panel and the characteristics were determined. The dust deposition density in g/m2 of panel surface area was determined in each test run. The effect of dust deposition density on the short circuit current, output power and the fill factor was determined and discussed. It was concluded that dust accumulation considerably deteriorates the performance of the photovoltaic cells. However, in carrying out the investigation on the effect of dust and particulate pollution, the physical characteristics of dust must be determined and correlated to the observed effects.