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PORTABLE ROBOT SYSTEM FOR CLEANING SOLAR PANELS

Chapter 1: Introduction1.1 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

SIET, VIJAYAPURA Dept. of EEE Page 1


Chapter 2: WORKING PRINCIPLE2.1 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 technologyHeliotex 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 PV panels

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 system that uses electrostatic cleaning

2.1.3 Robotic cleaning solutionsThe 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 system of 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 robotThe 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 RobotThe 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 system operation 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 subsystem for 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 system schematic



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: System test (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

panelsSolar 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 SnowPV 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 CONCLUSIONDust 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

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Zeitoon, B., 75-111, 2011.

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[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,

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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

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