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SCCC701 Engineering Development Project | P a g e

Development of an automatic robotic cleaning system for photovoltaic plants

Student: Nawaf Albaqawi

ID No: 10330652

Bachelor of Engineering Technology (Electrical)

SCCC701 Engineering Development Project

Academic Supervisor: Alireza Gheitasi

Tutor: Debbie Hogan

2014

SCCC701 Engineering Development Project | P a g e i

PROJECT DETAILS

STUDENT

Name: Nawaf Albaqawi

Email: [email protected]

Phone: 021794441

ACADEMIC SUPERVISORS

Name: Alireza Gheitasi


Direct Work Line: 07-8348800 ext 3143

TUTOR

Name: Debbie Hogan


Direct Work Line: 07-834 8800 ext 7839

mailto:[email protected]



SCCC701 Engineering Development Project | P a g e ii

Abstract

Use of renewable energy sources in New Zealand such as photovoltaic (PV) panels

has been increasing over the last few years. The Thames energy group is planning to

explore the possibility of using a more sustainable energy. Alkhaldi Mohammed, a

Wintec student did a study to install 327 kw PVs system over the Thames hospital

roof which has an area of 2950m,2 and another Wintec student Alnajrani Hassan, did

a study to install 11064 KW PV systems with an area of 99576m2 to cover the needs

of Thames domestic houses. However, with Thames being near the coast, and

surrounded by forest, there were some environmental issues affecting the PV

output, such as dust which accumulated from pollen and sea salt.

This project was to maintain the PVs to generate power at high efficiency. The i7

cleaner robot which was initially designed to clean houses was studied and new

software was developed to be able to efficiently work on PV panels. Then the robot

structure will be developed by the mechanical team next semester so that it will be

ready to use.

The developed software reduced the cleaning time for a 1x2.20 meter panel from

eight minutes to two minutes by setting a path on the surface of the PV panels for

the robot, instead of just a semi random movement. Whereas the old software could

clean 11 panels in 90 minutes, the new program can clean 37 panels in the same

time.

SCCC701 Engineering Development Project | P a g e iii

Abbreviations

DC – Direct current

kW – Kilowatt

m2 – Square meter

µc – Microcontroller

PV – Photovoltaic

V1 – The name of the cleaning robotic system

Glossary

Array – Is a way of photovoltaic (PV) modules electrical connection that providing a

single electrical output.

Direct current (DC) – The PV systems genera electricity in DC, which is defined as the

electricity flow, continues through conductors.

Kilowatt (kW) – A unit of electrical power equal to 1,000 watts.

Photovoltaic – is technology to generating power, which uses a semiconductor to

convert light into electricity.

Watt – A unit of measurement of electric power.

SCCC701 Engineering Development Project | P a g e iv

Table of Contents

PROJECT DETAILS ............................................................................................................ i

Abstract .......................................................................................................................... ii

Abbreviations ................................................................................................................ iii

Glossary ......................................................................................................................... iii

Table of Contents .......................................................................................................... iv

Table of Figures .............................................................................................................. v

Table of Tables .............................................................................................................. vi

1. Introduction ............................................................................................................ 1

2. Literature review .................................................................................................... 2

2.1 Growth of PV power usage ...................................................................................... 3

2.2 Environmental factors affecting efficiency of PV panels ......................................... 3

2.2.1 Shadow .............................................................................................................. 3

2.2.2 Snow .................................................................................................................. 4

2.2.3 Externally high temperature ............................................................................. 4

2.2.4 Dust, dirt, bird droppings, pollen and sea salt .................................................. 4

2.3 Effects of dust on solar panel efficiency .................................................................. 5

2.4 Methods used to clean PV panels ............................................................................ 6

2.4.1 Heliotex technology .......................................................................................... 6

2.4.2 Electrostatics cleaning ....................................................................................... 8

2.4.3 Robotic cleaning solutions ................................................................................ 9

3. Methodology ........................................................................................................ 13

3.1 Analyses of the i7 cleaning robot ........................................................................... 13

3.1.1 Analyses of the physical shape and internal components .............................. 13

3.1.2 Analysis of the movement pattern and the cleaning mechanism .................. 14

3.2 The mechanical stability testing ............................................................................ 15

3.3 Software development .......................................................................................... 16

3.3.2 The program development ............................................................................. 17

3.3.3 Conditions based on the sensors .................................................................... 18

3.3.4 Testing the operation of the new program ..................................................... 20

4. Result and discussion ............................................................................................ 22

4.1 The mechanical construction testing result ........................................................... 22

4.1.1 Testing the cleaning and the movement pattern of the robot on zero angle 22

4.1.2 The correct angle for the robot to be stable ................................................... 23

4.1.3 Testing the robot on a 45o angle ..................................................................... 24

4.1.4 Flipping angles ................................................................................................. 25

4.1.5 Crossing between two boards ......................................................................... 25

SCCC701 Engineering Development Project | P a g e v

4.1.6 Experiments to stop the robot flipping ........................................................... 26

4.2 The prototype testing result .................................................................................. 27

4.2.1 The forward path............................................................................................. 27

4.2.2 Rotation 180o right or left ............................................................................... 28

4.2.3 Right edge detected ........................................................................................ 28

4.2.4 Ending the cleaning process ............................................................................ 29

5. Conclusion and recommendation ........................................................................ 30

6. Student Declaration .............................................................................................. 31

7. References ............................................................................................................... 32

8. Appendix .................................................................................................................. 34

Appendix A The full codes of the developed software ................................................ 34

Appendix B The specification of the cleaner robot ..................................................... 42

Appendix C Photos of the robot’s movement process during cleaning ...................... 43

Table of Figures

Figure 2-1: Thames location over New Zealand. ........................................................... 2

Figure 2-2: Heliotex cleaning technology using water and soap to clean the surface of

PV panels (Heliotex, 2013). .................................................................................... 6

Figure 2-3: Structure of PVs system that uses electrostatic cleaning (Jalbuena, 2010).

................................................................................................................................ 8

Figure 2-4: Traveling system of robot V1.0 head along of the panel arrays (Anderson,

2012) ...................................................................................................................... 9

Figure 2-5: Drive Wheel Paired Via a Chain (Anderson, 2012). ................................... 10

Figure 2-6: The results of a single pass of the V1 cleaning robot ................................ 10

Figure 2-7: Sun Brush full automatic cleaning over solar panels (Siemens, 2013)...... 11

Figure 2-8: The i7 house-cleaning robot. ..................................................................... 12

Figure 3-1: i7 Cleaning robot components. ................................................................. 13

Figure 3-2: Moving in the zigzag mode ........................................................................ 14

Figure 3-3: Moving in the spiral mode. ........................................................................ 14

Figure 3-4: The i7 cleaning robot’s bins (Pursonic i7 vacuum cleaner robot, 2012). .. 14

Figure 3-5: Cleaning experiment. ................................................................................. 15

Figure 3-6: The new constant path of the cleaner robot. ........................................... 16

Figure 3-7: The searching path of the robot. ............................................................... 17

Figure 3-8: The prototype of the new program represented by LED lights and

controlled by Arduino microcontroller. ............................................................... 20

Figure 3-9: Wiring diagram of the prototype. ............................................................. 21

Figure 4-1: Soft powder left after cleaned the board. ................................................. 22

SCCC701 Engineering Development Project | P a g e vi

Figure 4-2: The dirt bin storage. .................................................................................. 22

Figure 4-3: The robot tested on 19.4 degree angle. .................................................... 23

Figure 4-4: Tip supported on the front of the robot. .................................................. 24

Figure 4-5: The robot flipping over when it climbed on 45 degree angle. .................. 24

Figure 4-6: Starting flipping angle which is 23 degree angle. ...................................... 25

Figure 4-7: The robot crossing between two boards. ................................................. 25

Figure 4-8: Extra weight added to the robot. .............................................................. 26

Figure 4-9: The left edge detected and the robot back to the path. ........................... 27

Figure 4-10: The front edge detected and the robot rotated. .................................... 27

Figure 4-11: Rotation 180 degree to the right. ............................................................ 28

Figure 4-12: Rotation 180 degree to the left. .............................................................. 28

Figure 4-13: The right edge detected and the robot back to the path. ...................... 28

Figure 4-14: Detecting the End and back to the starting point. .................................. 29

Table of Tables

Table 3-1 The truth table of the new program sensors and actuators action. ........... 18

Table 3-2 Existing i7 cleaning robot motors control movement. ................................ 19

SCCC701 Engineering Development Project | P a g e 1

1. Introduction

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 20011 (Sustainble

Electricity Association New Zealand, 2013).

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

township.


2. Literature review

For solar power to be efficient, elimination of some environmental effects is needed.

This section will discuss the PVs’ efficiency which is influenced by the environment,

especially the effects of dust. The previous automatic cleaning methods that were

used have been evaluated with the purpose of developing an i7 cleaning robot which

will be efficient at removing dust and pollen from the PV panel’s surface.

As Thames wants to be a renewable energy township, and as its locality is near the

sea, tourism is especially important to the town in the summer months. The map of

Thames location on the Coromandel Peninsula is shown in Figure 2-1. There are a lot

of renewable energy projects for the township currently being undertaken. The

largest renewable energy project is to install PV panels for most houses and

businesses. As this project is located in Thames, there are some environmental

effects on PVs’ output, which are sea salt, bird dropping and pollen, as Thames faces

the sea and is surrounded by forest (B. Stanton (personal communication, 6

November 2013)).

Figure 2-1: Thames location over New Zealand.


2.1 Growth of PV power usage

PV power is one of the most efficient renewable sources of energy. The use of PV

power energy is growing worldwide. In New Zealand it has been reported that the

installations of PV panel systems have increased dramatically by 370% since 2011,

which has also led to a need to find a way to effectively keep the PV panels clean

(Sustainble Electricity Association New Zealand, 2013). The current capacity of an

installed PV system in New Zealand is 8.2MW (Sustainble Electricity Association New

Zealand, 2013). Lower cost and ease of use are the two key drivers behind the

growth of PV panels in New Zealand (Sustainble Electricity Association New Zealand,

2013). In other countries the situation is the same; for example, the residential PV

capacity installed in the United States is projected to grow from 1.4 GW in 2010 to

10.6 GW by 2016 (Clean Energy Prize, 2013).

2.2 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.

2.2.1 Shadow

When installing PV panels, it is important to consider where shadows fall (Sullivan,

2011). 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 (Sullivan, 2011).


2.2.2 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

(Adele, 2010). 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 (Adele, 2010). In this project snow was not considered because it has

rarely snowed in Thames.

2.2.3 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 (Hill, 2013). In this project extremely high

temperatures were not be considered, as the temperature in Thames rarely reaches

this level.

2.2.4 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 (Kasim, 2010). 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 (B. Stanton

(personal communication, 6 November 2013)).


2.3 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% (Adinoyi, 2013). 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 (Kasim, 2010).

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 (B.

Stanton (personal communication, 6 November 2013)).


2.4 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 project 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 (Anderson, 2012).

The cleaning methods are explained below:

2.4.1 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 (Heliotex, 2013). 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 (Heliotex, 2013).

The Heliotex system sources the water from the residence via a hose or pipe

connected to the pump and attached to nozzles on the solar panel surface without

causing rubbing. See Figure 2-2.

The Heliotex system can be installed for any size or number of solar panels. The cost

of installation for the Heliotex is US$2,258.00 to cover 50 PV panels (Conduit, 2014).

Figure 2-2: Heliotex cleaning technology using water and soap to clean the surface of PV panels (Heliotex, 2013).


The advantages and disadvantages of using the Heliotex cleaning system are listed

below:

Advantages:

Good for areas with ready access to water.

Improves the effectiveness of the PV panels after being washed by almost

100%.

The Heliotex cleaning system is reliable (warranted for 10 years).

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.


2.4.2 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 (Jalbuena, 2010).

The dust is shaken off the solar panels when an electrically charged wave breaks

over the surface material. This is not a safe way for homeowners who are using solar

panels because the panel shakes which may loosen its connection to the roof and it

could fall down and cause injury. However, it is an effective solution for larger

systems elsewhere. The structure of the panels is strong and flexible to avoid

breakage that may be caused by shaking, as shown in Figure 2-3 (Jalbuena, 2010).

In two minutes this system can remove up to 90% of dust from the surfaces of the

PV panels by sending an electrical dust deterring wave which causes the dust to fall

off onto the ground. (Jalbuena, 2010).However, this system is not going to remove

dust when it gets wet, or if it is in a moist environment. The movement of the wave

mechanism requires only a small amount of electricity which makes it a power

efficient system however at present; the worldwide usage of the harvesting system

is only 4% (Jalbuena, 2010)

Figure 2-3: Structure of PVs system that uses electrostatic cleaning (Jalbuena, 2010).


2.4.3 Robotic cleaning solutions

The section below discusses and analyses cleaning robots, such as the V1 cleaning

fixed robot and the SunBrush cleaner robot, to develop a better solution for using

the i7 vacuum-cleaning robot on PV panels.

2.4.3.1 The PV cleaner V1 robot

The robotised V1 system was designed for cleaning the surface of the PV panels

automatically to maximize the output of energy (Anderson, 2012). The V1 robot is

composed of a cleaning head and a drive system. The cleaning head has two

cylindrical brushes traveling upward and downward along the panel surface edges by

a pair of motorized trolleys to generate a clean PV panel as shown in Figure 2-4

(Anderson, 2012). A guide cable is connected to each drive trolley to control the

movement of the cleaning head and prevent unwanted rotation (Anderson, 2012).

Figure 2-4: Traveling system of robot V1.0 head along of the panel arrays (Anderson, 2012).


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 2-5. The wheels were designed in pairs to avoid falling down

when it is crossing gaps between two panels (Anderson, 2012).

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 2-6 which shows

one side of a dirty panel (as seen on the left side), while the right side stayed as it

was to highlight the difference (Anderson, 2012).

Figure 2-6: The results of a single pass of the V1 cleaning robot (Anderson, 2012).

Figure 2-5: Drive Wheel Paired Via a Chain (Anderson, 2012).


2.4.3.2 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 Figure 2-7. 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 in

(Siemens, 2013).

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.

Figure 2-7: Sun Brush full automatic cleaning over solar panels (Siemens, 2013).


2.4.3.3 Potential cleaning robot

After looking at all the cleaning methods, the idea came to develop the i7 vacuum

robot, which was designed to clean floors in houses, to work on solar panel surfaces.

The i7 cleaning vacuum robot was chosen for this project because it is flexible, small,

and has an intelligent control system.

2.4.3.4 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, 2012). 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. It has a display screen, as shown in Figure 2-8 (Pursonic i7 vacuum

cleaner robot, 2012).

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.

Figure 2-8: The i7 house-cleaning robot.


3. Methodology

This section describes the methodology used to modify the i7 cleaning robot to clean

the PV panels’ surfaces. The methods for developing the cleaner robot are divided

into 3 sections:

1) Analyses of the i7 cleaning robot

2) Mechanical stability analyses

3) Software development

In the first section components of the i7 cleaning robot have been identified. This

analysis was needed to enable the mechanical improvement and the software

improvement. In the mechanical analysis section the robot was tested at different

angles to find the most stable movement for the new software, also to address the

issues needed to be improved by the mechanical team. In the software section new

software was developed and tested to enable the robot to work on the surfaces of

PV panels.

3.1 Analyses of the i7 cleaning robot

Different components of the i7 cleaner robot were analyzed in order to understand

the process of cleaning, based on the current software. This analysis was to

understand the mechanism of operation of the robot to design new software that

enables the robot to work effectively on the surface of PV panels.

3.1.1 Analyses of the physical shape and internal components

The cleaner robot is shown in Figure 3-1; the diameter of the robot is 320mm and

the height is 87mm with weight of 3.2kg. This robot has several components

including, a cleaning brush which is spun by a DC motor and a small side brush. Two

servo DC motors drive the robot, while a small vacuum motor drives the cleaning

process. The robot has 10 sensors, of which four are underneath to detect ledges;

another four are located along the front of the bumper, and two object sensors are

located on the sides of the bumper.

Figure 3-1: i7 Cleaning robot components.


3.1.2 Analysis of the movement pattern and the cleaning mechanism

The i7 cleaning robot follows no preset path; it is controlled by a microcontroller

(µc). The methods of the i7 cleaning robot’s movement are zigzag, spiral and anti-fall

as shown in Figures 3-2 and 3-3. When the robot is in the zigzag mode it travels

straight for a set distance, then changes direction, or also will change direction if it

detects an object. At a set distance it will go into the spiral mode, where the robot

spirals on one spot for a short time, then goes back to the zigzag mode.

Dirt, pollen and dust are scoured by the brush into the main dirt bin and the soft

dust is vacuumed through the inlet vacuum as shown in Figure 3-4. For more

specifications of the i7 cleaning robot see appendix B.

Figure 3-4: The i7 cleaning robot’s bins (Pursonic i7 vacuum cleaner robot, 2012).

Figure 3-2: Moving in the zigzag mode. Figure 3-3: Moving in the spiral mode.


3.2 The mechanical stability testing

In this section the i7 cleaning robot’s stability was tested at different angles to find

the most stable movement for the new software. Also to find the stable angle for the

robot to work on and the maximum angle that it is able to operate at. The processes

of the stability test are listed below:

Testing the robot’s cleaning ability and its movement on zero angle. The robot was tested on a zero angle board to ascertain effectiveness of the cleaning provided, and the capacity of the dirt storage. Carpet cleaning powder and tree leaves with some pollen were sprayed on the top of the board as shown in Figure 3-5. The size of the board was 1×2.20 meters. The robot’s movement was tested to see its movement patterns during the cleaning process. Also, the time spent to cover all of the board was noted to find how fast the robot worked.

The best angle for the robot to be stable. The robot was tested on a 19.4 degree angle on a smooth wooden board to find the best angle that the robot can operate and remain stable at.

Tested the robot on a angle. The robot was tested on different angles to find the maximum angle that can be climbed. The robot was tested up to and this was considered to be its maximum.

Flipping angle The robot was tested on different angles starting from 19.4 degrees to find the slope angle where the robot would start to flip over.

Crossing between the two panels The robot was tested on two flat boards to prove the ability of the robot when it crosses between the boards. This was to determine whether the edge detecting sensors will detect the gap.

Stopping flipping experiments The robot was supported by different weights to stop it flipping, and tested at different angles.

Figure 3-5: Cleaning experiment.


3.3 Software development

As explained in Section 3.1.2, the i7 cleaner robot was moving semi randomly, and

that caused higher power consumption. The existing software is locked by the

manufacturer so that new software needed to be developed. The new software is

programmed to follow a path on the surface of PV panels as shown in Figure 3-6, to

minimize the cleaning time and power consumed. The robot’s path was chosen to be

vertical to make the robot more stable; if the path is set to be horizontal some force

from the side will push the robot down.

The new software program is set to start from the left bottom corner and end on the

right side of the panel as shown in Figure 3-6. When the robot detects the end of the

panel it will return to the starting point. It will be either on the top right side of the

panel or on the bottom right side when it is finished. The robot will then stops and

wait to restart to do the next run of cleaning.

starting

End

Figure 3-6: The new constant path of the cleaner robot.


3.3.2 The program development

The new program process for the cleaning robot is shown in the flow diagram in

Figure 3-7 and the full codes of the program are indicated in appendix A. This

program is an alternative to the i7 cleaning robot program. The new program has

these considerations:

1. Follow the sequence process as shown in Figure 3-7

2. By using anti-fall sensors the ledges of the PVs are recorded so that it

does not fall off

3. Returns to the starting point after finishing the cleaning process

Idle

Straight

Obstacle

front

Obstacle

left

Obstacle

right

Stop, Turn

Left 4cm

Stop, Turn

Right 4 cm,

Stop, back 10 cm

Rotate 180°

right

Stop, back 10 cm

Rotate 180°

left

Obstacle

front

Obstacle

left

Obstacle

right

Stop, Turn

Left 4cm

Stop, Turn

Right 4 cm,

Straight

Back to original place

Then

Front sensor & right

sensor engaged

Front sensor & left

sensor engaged

Figure 3-7: The searching path of the robot.


3.3.3 Conditions based on the sensors

This section explains the sensors’ detection and the robot directions based on the

searching path in the flow diagram as demonstrated in Section 3.4.2. In this

development three main underneath sensors were used, which are the front, the left

and the right sensors. Other sensors were not necessary when the robot was used

on the PV panels. Table 3-1 points out each sensor’s working and the robot’s

direction. These sensors were used to control the movement of the robot by using

actuators. There are two possible situations for each sensor which are high or low. A

high situation happens when one of the robot sensors detects the ledge and the low

situation means the sensor has not detected an edge. These situations are based on

the sensor’s signal.

Table 3-1: The truth table of the new program sensors and actuators action.

Front Sensor

Left sensor

Right sensor

Direction

Low Low Low Forward

High Low Low Find route right or left

Low High Low Turn right

Low Low High Turn left

High High High Find route right

High High Low Find route right

High Low High Find route left

Low High High Find route right


The movement and rotation of the i7 cleaning robot was controlled by the right and

left wheels. A similar method was used to design the new software as shown in

Table 3-2. The new program was simulated on the Uno Arduino microcontroller.

Table 3-2: The cleaner robot’s motors control movement.

Robot Movement Left Motor Right Motor

Straight Straight Straight

Avoid the left edge Stop Reverse

Avoid the right edge Reverse Stop

Backward Reverse Reverse

Right-Rotating 180o Straight Stop

Left-Rotating 180o Stop Straight

This table demonstrated the direction movement of the robot when a sensor detects

an edge. There are six possible ways to change the robot’s direction.

First way; when all the sensors are low the robot will travel straight.

The second one; when the left sensor detects an edge on the left

side it will stop then turn to the right side four centimeters until the

left sensor goes to low.

The third situation; when the right edge is detected it will do the

same as the left sensor’s job when it detects the edge, but the

motor’s directions will be opposite.

The fourth situation is when the robot drives backward in three

circumstances. If the front sensor and the right sensor go high the

robot will stop, drive back 10cm, and change to the left direction,

and if all three sensors are high, the robot will stop and drive back

10cm, then find a route right. The last circumstance is if the front

sensor and the left sensor are high, the robot will stop and drive

back 10cm, then find a route right.

The fifth situation of the robot directions is when the robot rotates

180o to the right side. This happens when the robot reaches the top

ledge of the panel; it will stop and travel back 10cm, then rotates

180o as it drives down along the panel.

The last situation is when the robot rotates to the left side from the

bottom of the panel and drives up along the panel. The process of

the rotation is the same as for the right rotation.


3.3.4 Testing the operation of the new program

The new controlling program was tested on the Arduino µc with LED lights that

represented actuators, and three switches to represent the i7 cleaning robot’s

sensors as shown in Figure 3-8. The green lights represented the forward movement

of the robot; the red LED lights represented the backward movement of the robot,

and the orange LED light represented the brush actuator. The green and the red

LEDs on the right side of the prototype represented the right-motor of the i7

cleaning robot and the left side LED lights represented the left-motor. The three

sensors which are the front sensor, the left sensor and the right sensor are

controlling the robot movement on a set path and protect it from falling off the

panel. The circuit wiring diagram of the prototype is shown in Figure 3-9.

Figure 3-8: The prototype of the new program represented by LED lights and

controlled by Arduino microcontroller.

1. Represents the front sensor

2. Represents the left sensor

3. Represents the right sensor

4. Represents the right-motor forward

5. Represents the right-motor reverse

6. Represents the left-motor forward

7. Represents the left-motor reverse

8. Represents the brush’s motor

9. Represents the on and off switch

10. The Arduino microcontroller


The Arduino µc was used because it is useful in the robotics and the ease

of the installation. In addition, many useful examples can be downloaded

from the Arduino website.

Figure 3-9: Wiring diagram of the prototype.

D4

D5

D4

D6

D3

Left-Motor Right-Motor

Brush-Motor

Brush-MotorR-Motor-ReversL-Motor-ReversL-Motor-ForwardR-Motor-Forward

Front-SensorLeft-SensorRight-Sensor

+5V

D13

D11D12

Front-Proximity Sensor

Left-Proximity Sensor Right-Proximity Sensor


4. Result and discussion

In this section the results regarding the cleaning provided and the robot’s movement

on different angled boards are presented and discussed. Also, the result of testing

the new software is discussed. Some issues were found, and these problems will

affect the efficiency of the robot if it used on the PVs surface. The issues have been

divided into two main groups:

1- Mechanical construction analysis

2- Software development

4.1 The mechanical construction testing result

4.1.1 Testing the cleaning and the movement pattern of the robot on zero angle

The i7 cleaning robot proved a good cleaning method by removing all the tree leaves

and pollen to the main storage bin. Some of the powder was removed to the main

bin while the soft sticky powder was removed to the small bin; these processes were

carried out several times.

While some of the soft sticky powder was left behind as shown in Figure 4-1, this

was because the vacuum was not strong enough, and the thickness of the brush was

light. Also the storage bin was filled from covering of one board as shown in Figure 4-

2, which could cause a problem if multiple PVs are connected together, as it would

need emptying many times. Those issues will be addressed by the mechanical team.

The robot was moving around one area many times, even though that area had been

previously cleaned. The intelligence of the controlling program worked perfectly, but

it took time to cover all the areas, because of the semi random movements. The

robot spent 7 to 10 minutes cleaning all the areas of the board. More pictures of the

robot’s movement process during cleaning are indicated in the appendix C.

Figure 4-1: Soft powder left after cleaned the board.

Figure 4-2: The dirt bin storage.


4.1.2 The correct angle for the robot to be stable

On a board, the robot traveled up and down the smooth wooden board perfectly on

a 19.4 degree angle as shown in Figure 4-3. However the robot went a bit faster than

normal when it was going down the slope, but this did not affect the robot’s

movement, because the robot was still stable.

The robot slipped down when it was turned off at the top of the board because the

material of the wheels could not stop the robot from slipping.

Figure 4-3: The robot tested on 19.4 degree angle.


4.1.3 Testing the robot on a 45o angle

The robot was first tested on a 45 degree angle and it climbed well, however it

needed tip support on the front to give it more stability to avoid flipping, as shown in

Figure 4-4. If the robot does not have support in the front it will flip over, as shown

in Figure 4-5. Also, the movement of the robot was hard and more slippery.

When the robot traveled downward, it went faster than the normal speed because

of the weight of the robot pushing it down. If there was no raised edge on the panel

it would have fallen down, because there was not enough time for the edge

detecting sensor to sense this and then send a command to the microcontroller to

rotate the robot.

From this experiment it was found that the motors and the gearboxes that drove the

wheels were strong enough, and were capable of moving the robot on a 45 degree

angle.

Figure 4-5: The robot flipping over when it climbed on 45 degree angle.

Figure 4-4: Tip supported on the front of the robot.


4.1.4 Flipping angles

The robot started to flip when the angle was increased to 23 degrees, as shown in

Figure 4-6. The robot started to lose it stability at this point. The cause of flipping

was that the shape of the robot was designed to work on flat surface, not on angles.

4.1.5 Crossing between two boards

The maximum gap the robot can cross between two panels was 2cm as shown in

Figure 4-7; for gaps more than 2cm, the robot managed to detect the gap and then

changed direction to avoid falling down. Also, as the sizes of the wheels were small

the robot could not jump between two panels if the gap was bigger.

Figure 4-6: Starting flipping angle which is 23 degree angle.

Figure 4-7: The robot crossing between two boards.


4.1.6 Experiments to stop the robot flipping

Two experiments were carried out to find a solution to the robot flipping when it

worked at a angle or greater.

4.1.6.1 Support the robot by using different weights

The robot was tested again on a 45 degree angle supported with a 1 kg weight on

the front. It still started to flip over, even with the support of 1kg weight. The weight

was increased until the robot stopped flipping, and the support weight was 1.4 kg.

The robot climbed the board successfully, but without stability. Whereas, when

the robot traveled back down, it started to flip from the back and lost control as is

shown in Figure 4-8. This was because the movement was too fast.

4.1.6.2 Tested with a supported weight of 800 g

The robot was tested until a 30.4o angle and supported by a 800g weight on the top-

front. It climbed without flipping, but still needed some support to avoid slipping.

However, increasing the weight of the robot affected the battery life and the motor’s

life.

Figure 4-8: Extra weight added to the robot.


4.2 The prototype testing result

The result of the software development program, which was required to drive the

robot in a set path, was that it worked well. The time for the robot to clean a board

sized 1×2.20 meters in a set path was 2.42 minutes. However, the time taken in the

original program to cover same board was 7 to 10 minutes, which was an average of

8.50 minutes, because of the semi random movement. The time of the robot’s

battery life is 90 minutes when it is cleaning on a flat surface, but with the new

program it can clean 37 panels size 1×2.20 meters in 90 minutes, whereas in the

existing program it could only clean 11 panels of the same size in that time.

After thorough testing it was proven that the sensors worked effectively in all

aspects of controlling the robot, and prevented it from falling off the edge of the PV

panel. The full details of the testing process and the results are outlined below.

4.2.1 The forward path

The robot was moving along the left edge as shown in Figure 4-9 where there were

two possibilities of detecting edges. The first situation was when the robot started

moving up the panel and lost its direction on the left side. In this situation the left

sensor detected the edge then stopped, reversing the right motor 4cm each time

until the robot went back to the set path. The second situation was when the robot

reached the top edge; then the front sensor detected it, stopped and went backward

10cm, then rotated 180o before driving down as shown in Figure 4-10.

Top

L R

F

1 Go back

10cm

2 Rotate

180o

L R

F

Top

Reverse

Figure 4-10: The front edge detected and the robot rotated.

Figure 4-9: The left edge detected and the robot back to the path.


4.2.2 Rotation 180o right or left

The robot was rotating when the front sensor engaged. When the robot reached the

top edge it stopped, went backward 10cm, then rotated as shown in Figure 4-11.

Also the left rotation was the same as the right rotation process; however the robot

was rotated left when it reached the bottom of the panels as shown in Figure 4-12.

4.2.3 Right edge detected

The right sensor engaged whether the robot drove to the top or the bottom of the

panel. The right-side edge detection mode started the robot, then stopped it,

reversed the left motor 4cm each time until the robot went back to the set path as

shown in Figure 4-13.

Reverse

Top

L R

F

Figure 4-12: Rotation 180 degree to the left.

Figure 4-11: Rotation 180 degree to the right.

Figure 4-13: The right edge detected and the robot back to the path.


4.2.4 Ending the cleaning process

When the robot was on the top right of the panel, and rotating to the right side, the

front sensor and the right sensor engaged, and that meant that the robot had

reached the end (the right side of the panel) as shown in Figure 4-14. It then went

down to the original location, and then shifted into the idle mode until it restarted.

Whereas if the robot reached the end of the bottom of the panel during the

rotation, and if the front sensor and the left sensor engaged as shown in Figure 4-14

the robot went to the original location then shifted to the idle mode until the robot

restarted.

Rotating

left & F-L

sensors

engaged

Rotating

right & F-R

sensors

engaged

Top L

R

F

L

R F Starting

point

Figure 4-14: Detecting the End and back to the starting point.


5. Conclusion and recommendation

This project highlights the effect of dust, dirt, pollen, sea salt, and bird droppings on

the PV system’s efficiency. However, the development of the i7 cleaner robot can

help solve those problems. This development is divided into two parts; mechanical

(stability and cleaning mechanism) which will be developed by mechanical team next

semester, and the software development. The software development for the i7

cleaner robot has been done in this project. The cleaning time has been reduced

from eight to two minutes by setting a path for the robot on the surface of the PV

panels, instead of using the semi random movement method.

From this project learned about the field of robotics and designing programs using

Arduino software. Also learned how to lead and manage a project in the future.

The weaknesses of this project were the limited time and the fact that the

mechanical team work will not start until next semester.

Recommendations

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.

Future development could be to connect the cleaner robot to Almalki Ali’s project,

which is monitoring PV panels wirelessly, and developing software connection to

give alarms and alerts. Further and useful information about the cleaner robot is

obtainable from

http://www.robotiklubi.ee/_media/kursused/roomba_sumo/failid/hacking_roomba.

pdf

http://www.robotiklubi.ee/_media/kursused/roomba_sumo/failid/hacking_roomba.pdf

http://www.robotiklubi.ee/_media/kursused/roomba_sumo/failid/hacking_roomba.pdf


6. Student Declaration

I have not copied any part of this report from any other person’s work, except as

correctly referenced. Collaboration: No other person has written any part of this

report for me.

Student Name: Nawaf Albaqawi

Student Signature: ________________________ (signature)

Hand-in Date 6 / 06 / 2014

Completion Date 5 / 06 / 2014


7. References

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One Block Off the Grid: http://1bog.org/blog/the-effect-of-snow-on-solar-

panels/

Adinoyi, M. J. (2013). Effect of dust accumulation on the power outputs of solar

photovoltaic modules. Retrieved 9 29, 2013, from sciencedirect:

http://www.sciencedirect.com/science/article/pii/S0960148113003078

Anderson, A. G. (2012). ROBOTIC DEVICE FOR CLEANING PHOTOVOLTAIC PANEL

ARRAYS. Retrieved 9 12, 2013, from Northeastern University:

http://www.coe.neu.edu/Research/robots/papers/CLAWAR09.pdf

Clean Energy Prize. (2013, 2 26). PV Cleaner. Retrieved 2 20, 2014, from Clean Energy

Prize: http://cep.mit.edu/wp-

content/uploads/2013/02/PV_Cleaner_Executive_Summary.pdf

Conduit, S. (2014). Solar Conduit. Retrieved 2 18, 2014, from solarconduit:

https://solarconduit.com/shop/checkout/cart/

Heliotex. (2013). HELIOTEX AUTOMATIC SOLAR PANEL CLEANING SYSTEM. Retrieved

9 14, 2013, from solarconduit: https://solarconduit.com/shop/sun/pv-

module-washing-systems/heliotex-automatic-solar-panel-cleaning-system-

50.html

Hill, C. (2013). The Effects of Temperature on Solar Panel Power Production.

Retrieved 10 1, 2013, from sfgate: http://homeguides.sfgate.com/effects-

temperature-solar-panel-power-production-79764.html

Jalbuena, K. R. (2010, 8 27). mars-inspired technology makes pv-panels-self cleaning.

Retrieved 9 14, 2013, from ecoseed.org/technology:

http://www.ecoseed.org/technology/13801-mars-inspired-technology-

makes-pv-panels-self-cleaning

Kasim, N. K. (2010). New Technique for Treatment of the dust accumulation from PV

solar panels surface. Iraqi Journal of Physics, 2010.

Siemens. (2013). The Dirt Must Disappear. Retrieved 9 14, 2013, from Siemens:

http://www.industry.siemens.com/topics/global/en/magazines/process-

news/sustainability/logo-controls-automatic-panel-

cleaning/pages/default.aspx


Sullivan, R. M. (2011). SHADOW EFFECTS ON A SERIES-PARALLEL ARRAY OF SOLAR

CELLS. Retrieved 10 1, 2013, from Nasa:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650020213_1965020

213.pdf

Sustainble Electricity Association New Zealand. (2013, 11 7). SOLAR PV SURVEY

RESULTS RELEASED. Retrieved 2 25, 2014, from Sustainble Electricity

Association New Zealand: http://www.seanz.org.nz/News-Events/News/NZ-

Solar-PV-Surey-Results-released


8. Appendix

Appendix A The full codes of the developed software









Appendix B The specification of the cleaner robot


Appendix C Photos of the robot’s movement process during cleaning

Documents

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