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PORTABLE ROBOT SYSTEM FOR CLEANING SOLAR PANELS
SIET, VIJAYAPURA Dept. of EEE Page 1
Chapter 1: Introduction
1.1 Background
Photovoltaic panel production has increased globally in response to the
growing demand for solar energy.
This has been the result of an increased awareness of the damage to the
environment that using fossil fuel sources has had over the years. The rate of solar
panel usage in New Zealand has increased 370% since 2011
There are many factors that affect PV power efficiency, such as shadow,
snow, high temperatures, pollen, bird droppings, sea salt, dust and dirt. The main
factor that affects a PV panel’s efficiency is dust, which can reduce its efficiency by
up to 50%, depending on the environment.
As the Thames Energy Group eager to explore the possibility of using a more
sustainable power source. The possibility of installing many PV panels into the area
brought about the need to consider how to increase long term efficiency by the
regular removal of debris from the PV panels. In particular, dust which is made up of
pollen, sea salt and dirt particles.
This project investigated the possibility of using the i7 cleaning robots (usually
used for house cleaning) to remove dust, sea salt and pollen from the surfaces of PV
panels.
The limitation of this project was that the new software was tested in
simulated conditions, but has not been used in actual environmental conditions in the
Thames towns

Chapter 2: WORKING PRINCIPLE
2.1 Methods used to clean PV panels
At present, PV panels can be cleaned manually and automatically. Over time,
manual cleaning is more costly compared to automatic cleaning. This seminar
considered some different cleaning technologies available on the market today, such
as; the Heliotex rinse, electrostatic cleaning, the V1 cleaning robot system and the
SunBrush robot system. These cleaning methods were chosen to review, so as to
determine whether the development of the i7 house-cleaning robot will work on a PV
panel’s surface. Furthermore, the use of PV panels cleaning robotics has been
expanding over the last few years to reduce the need for manual cleaning. The
cleaning methods are explained below.
2.1.1 Heliotex technology
Heliotex is an automatic cleaning system that washes and rinses solar panel
surfaces. The cleaning system can be programmed whenever it is necessary,
depending on the environment. It does not require any further attention except the
replacement of the water filters and the occasional refilling of the soap concentrate. It
contains a five-gallon reservoir for soap, which does not cause any damage to the
solar panels and roofing materials.
Fig 2.1: Heliotex cleaning technology using water and soap to clean the surface of PVpanels
2.1.2 Electrostatics cleaning
Electrostatics cleaning technology is named “Harvesting electricity”. This cleaning
technology was first developed by scientists to solve the problem of dust deposits on the
surfaces of PVs located on Mars. This technology can also be used in dry dusty areas on

Earth. Electrostatic charge material is used on a transparent plastic sheet or glass that
covers the solar panels. Sensors monitor dust levels and activate the system into cleaning
mode.
Fig 2.2: Structure of PVs systemthat uses electrostatic cleaning
2.1.3 Robotic cleaning solutions
The section below discusses and analyses cleaning robots, such as the V1 cleaning
fixed robot and the Sun Brush cleaner robot, to develop a better solution for using the i7
vacuum-cleaning robot on PV panels.
Fig 2.3(a): Traveling systemof robot V1.0 head along of the panel arrays
The drive system consists of three main components of motion: the top and bottom
trolleys and the cleaning head. The top and bottom trolleys use a 12V DC motor, to
provide motion to the cleaning system. The top and bottom can be controlled
independently along the panel rows. Contrinex 500 M30 sensors located on the trolley
frame detect the edges of the panel, giving a command to the control system to slow or
stop the motion when the trolley reaches the end of the panel array. The drive wheels of
each trolley are composed of two pairs. Each pair is linked via a chain as shown in

Figure 2.3(a) the wheels were designed in pairs to avoid falling down when it is crossing
gaps between two panels.
The V1 cleaning robot system was initially tested on one pass of cleaning at a rate of
2.33 m2/min. The results of the cleaning pass can be seen in Figure 2.3(b) which shows
one side of a dirty panel (as shown below), while the right side stayed as it was to
highlight the difference.
Fig 2.3(b): The results of a single pass of the V1 cleaning robot.
2.1.4 The SunBrush robot
The SunBrush is a similar fixed cleaning robot primarily designed for cleaning snow
from PV panels. It is a fully automated cleaning system for the PV panels. This cleaning
robot was produced in Germany to remove snow from the solar power surfaces as shown
in Fig. 2.4 the main use was in solar heating systems, as removal of the accumulated
snow reduced the amount of sunlight going into the panels, which impacted on the
amount of hot water produced. Use of this system has led to a 15-18% increase in solar
panel efficiency and up to a 20% increase in hot water production. The structure of the
SunBrush is simple. It is fixed to the roof and is composed of a brush that is driven by a
small motor through a roller, as shown below.

Fig.2.4: Sun Brush full automatic cleaning over solar panels
The disadvantages of using these fixed robotic systems are that they are expensive
and difficult to install over a large PV area; while, the i7 cleaning robot is smaller,
flexible and cheaper.
2.1.5 Cleaning Vacuum i7 Robot
The i7 vacuum robot was designed to clean homes and is good for a wooden and
ceramic floor plus short-haired carpet (Pursonic i7 vacuum cleaner robot). The i7 robot is
an advanced cleaning robot with various intelligent cleaning modes. It has wall-detection
sensors and anti-fall sensors to detect edges. Theses sensors make the cleaning robot
smarter. The cleaning time can be scheduled to be done daily, weekly or on a specific
date. The i7 cleaning robot can be controlled remotely using a remote control. The i7
vacuum-cleaning robot is designed to work on a flat surface, so some change required to
the structure and software to enable it to work on PV panels at different angles.

Chapter 3: OVERVIEW OF THE CLEANING SYSTEM
The cleaning system design main criterion is its ability to clean multiple panels in a
solar farm using a single robot. Such a system is considerably much simpler than having
multiple robots in the same farm working simultaneously. In order to facilitate the robot
transfer from one panel to another, the system consists of two main parts; the first is the
cleaning robot and the second is the automated carrier cart (see fig. 3.1). The carrier part
is a cart that moves on a rail platform. The cart transfers the robot from one panel to the
next.
The operation sequence of the system is shown in Figure 3.1 That is, the carrier cart
aligns itself with the solar panel at which point the robot leaves the cart to clean the
panel through forward and backward sweeps (Fig. 3.1-1) and returns to the cart which
transports the robot to the next panel (Fig. 3.1-2). Then, the robot performs the cleaning
sweeps as before (Fig. 3.1-3).
Fig.3.1: The proposed systemoperation sequence
The cleaning robot, as shown in figure 3, travels the entire length of a solar panel
while cleaning the panel in the process. The robot mainly consists of two brushes on
the extreme ends, four wheels, four motors, sensors and controller subsystem.

Two motors are installed on each side of the robot frame. On motor is used to drive
two wheels and the other motor is used to drive one brush. The robot is symmetrical so
the weight distribution is uniform and this increases the stability of the robot on top of a
tilted solar panel. The design of the robot side panels insures the robot guided movement
along the panels while cleaning.
Fig. 3.2: The cleaning robot system(1. brush, 2. wheels, 3. motors, 4. connecting rods, 5.side panels, 6.
wheel driving system, 7. brush driving system)
The main advantage of this symmetrical design is that it can be easily modified to
handle wider solar panels, as illustrated in figure 3.3 The connecting rods and brushes
can be modified with the same driving system.
Fig.3.3: Adapting the robot subsystemfor different solar panels.

Chapter 4: Robot Operation and flow chart
4.1 CONTROLLER SUBSYSTEM
To ensure autonomous movement of the robot, a control system is implemented (see
fig.4.1). On-off control scheme was adopted based on Arduino microcontroller, a motor
controller and infrared sensors were used to provide the robot with the necessary
feedback about the PV panel boundaries. This makes the robot to stop before reaching
the edge of the panel.
The mode filter was used for processing of the collected signals from the infrared
sensors. Once the fused sensors’ reading exceeds a predefined threshold at which the
panel edge is found, the robot stops before reaching the edge
Fig.4.1:Control systemschematic

4.2. Robot Operation
Figure 4.2 describes the flow diagram of robot cleaning subsystem operation steps.
Initially, the robot stationed at the panel end waits the user start command. Once the
command is received the brushes start working and then the robot starts moving in one
direction while cleaning the panel.
Fig.4.2: Robot operation flowchart

During the operation, the robot keeps moving at constant speed until the sensors
signal reaching the panel edge at which point the robot slows down and stops. If this is
the robots first pass on the panel, it will switch direction and move backward until it
reaches the edge again where the carrier subsystem is located

Chapter 5: EXPERIMENTAL TESTING & RESULTS
The fully integrated robot cleaning system is shown in Figures 5.1 and 5.2 It can be
seen that, during cleaning, the robot moves along the panel length while covering the
whole width. The box in the middle contains the microcontroller and the battery to run
the motors. Sensors installed at both sides of the robot signal the reach of panel edge at
which point the robot returns back to the starting position, making a second cleaning pass
Fig.5.1: The panel integrated robot cleaning system. Fig.5.2: Direction of robot motion while cleaning.
To validate the robot designed operating capabilities, several experimental testing
scenarios were carried out focusing on the effectiveness of the robot in both static and
dynamic modes. First, the solar panel was covered with different amounts of sand (see
figures 5.3a and 5.3b) to simulate dust accumulation process.
It should be noted that after two passes, the robot was able to clear more than 80%
of the surface and repeated tests show the same results. Some dust is left on the panel due
to the use of short brushes, hence incomplete brush coverage of the panel surface width.
This problem should be addressed in future works.

a b
Fig.5.3: Systemtest (a) dusty panel (b)post cleaning.
To test the ability of the robot to function on tilted panels, the maximum tilt angle
at which the robot remains effective is of interest. The robot was placed on a panel
with a tilt sensor. The panel was tilted manually while the robot was operating and
the angle was measured (see figure 5.4). It was found that the robot can be used to
clean any solar panel at tilt angles between 0° and 40°.
Fig. 5.4: Robot functionality test on tilted solar panel.

Chapter 6: Environmental factors affecting efficiency of PV
panels
Solar power generation can be influenced by many factors. The major factors that
reduce or impede the generation of power for the PV panels are; shadows, snow, high
temperatures, dust, dirt, bird droppings, pollen and sea salt. The environmental
factors affecting solar energy generation will be discussed below.
6.1 Shadow
When installing PV panels, it is important to consider where shadows fall.
When PV panels are not installed correctly, their output can be reduced. To avoid
reducing the efficiency of the PV panel, the following should be considered:
 The dimensions of any shadow at different times of the year
 The structure and angle of the PV panel
 Tracking how the shadow influences the panel
6.2 Snow
PV panels can still generate electricity under a light snowfall, but once the snow
completely blocks out the sun radiation, the PV panels will stop generating electricity .
Further, if one area of a solar panel is completely covered by snow, the rest of the panel
can stop functioning because of the way the solar cells are wired together. In this project
snow was not considered because it has rarely snowed in Thames.
6.3 Externally high temperature
When panels reach high temperatures, power efficiency drops. Hill reported that the
efficiency of energy output drops by 1.1% for every extra degree in Celsius once the PV
panel temperature reaches 42 degree Celsius. In this seminar extremely high
temperatures were not be considered.

6.4 Dust, dirt, bird droppings, pollen and sea salt
Accumulated dust on the surfaces of PV panels can come from many different
sources, and can have a big impact on electricity production. The efficiency of the solar
panel can be reduced by up to 50% in a dusty environment, as this interferes with the
amount of direct sunlight received to the PV array. The rate of dust in Thames is low, but
annual cleaning is still recommended to remove dust that has accumulated over this time.
Pollen from flowering trees, bird droppings and salt spray from the sea are particular
problems for the Thames area
6.5 Effects of dust on solar panel efficiency
The power output generated by PV panels is known to suffer power efficiency losses
over time due to accumulation of dust and other dirt. In the Middle East, India and
Australia, PV power output is significantly affected by the accumulation of dust on the
surfaces of PV arrays. In Saudi Arabia, the accumulation of dust decreases the power
production by up to 50%. Research done by an engineering student in Baghdad in 2010
found that the transmittance decreased over a one-month period by approximately 50%
on average, due to the natural deposition of dust on PV panels.
As the growth of PV panel use increases, so does the need for monitoring and
cleaning the panels’ surfaces. The frequency of cleaning the PV panels depends on the
environment of the solar installation. A New Zealand company suggests solar panels
should be cleaned once to twice a year in the New Zealand environment.

Chapter 7: Advantages & Application of robot
7.1 Advantages
 Time saving
 Helps you to maximize solar production on daily basis
 Helps to recover lost kilowatt power at pennies per watt
 Advanced futures
 Improves the effectiveness of the PV panels after being washed by almost 100%.
7.2 Disadvantages
 Expensive equipment such as the soap, hoses and pumps which are required.
 Requires ready access to plenty of water.
 Needs regular checking for the water and soap residue build up
 The soap may affect the environment of plants.
7.3 Applications
 Used to cleaning solar pv panels

Chapter 8: CONCLUSION AND FUTURE SCOPE
8.1 CONCLUSION
Dust accumulation on PV panels can significantly reduce their power output. While
the GCC region is solar-energy rich, the desert conditions are quite dusty threatening the
PV systems power generation potential. The robotic system proposed in this paper is a
simple way to tackle this challenge effectively.
8.2 FUTURE SCOPE
 In the future, the robot’s software can be developed to be smarter, such as that when
it cleans any PV panel surface, it will save the information about ledges, size and its
location.
 Install the Arduino µc with the developed program into the robot after the mechanic
development.
 Instead of increasing the robot weight to make it stable, changing the robot’s shape
with better cleaning mechanism is recommended.
 Portable robot which is monitoring PV panels wirelessly, and developing software
connection to give alarms and alerts.
 Now days the solar energy generation is more so u can use this technique to clean
solar panel.

REFERENCES
[1] W.E. Alnaser and N.W. Alnaser, “The Status of Renewable Energy in the GCC
Countries”, Renewable and Sustainable Energy Reviews, 15, 3074-3098, 2011.
[2] B.M.A. Mohandes, L. El-Char and L.A. Lamont, Application study of 500 W
Photovoltaic (PV) system in the UAE, Applied Solar Energy, 45 (4), 242-247, 2009.
[3] I. Abdel Gelil, F. Chaban and L. Dagher, Chapter 3: Energy, in Arab environment 4-
Sustainable transition in a changing Arab World, (Eds.) Abaza, H., Saab, N and
Zeitoon, B., 75-111, 2011.
[4] M. Dinçer and M.E. Meral, Critical Factors that Affecting Efficiency of Solar Cells,
Smart Grid and Renewable Energy, 1, 47-50, 2010.
[5] D. Thevenard and S. Pelland, S. (2011), Estimating the uncertainty in long-term
photovoltaic yield predictions, Solar Energy, 91, 5, 432-445, 2013.
[6] H.L. Macomber, J.B. Rizek and F.A. Costello, Photovoltaic Stand-Alone Systems,
Preliminary Engineering Design Handbook, DOE/NASA/0195-1, NASA CR-
165352, M206, 1981.
[7] Solarch (2005), Best Practice Guidelines for Solar Power Building Projects in
Australia, The Centre for a Sustainable Built Environment, Faculty of the Built
Environment, University of New South Wales, 17-20, 2005, http://www.re-
systems.ee.unsw.edu.au/documents/ BiPV%20Best%20Practice%20guidelines.pdf
[8]A. Ibrahim, A., Effect of Shadow and Dust on the Performance of Silicon Solar Cell,
J. Basic. Appl. Sci. Res.,

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