Universal solar tracker final report

Universal Solar Tracker

Vassos Tapakoudes

10039266

Supervisor Dr Sanja Dogramadzi

Module UFMEAY-30-3

Undergraduate Final Year Project

Academic Year 2012-2013

11 April 2013

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Universal Solar Tracker Vassos Tapakoudes 10039266

Summary A detailed analysis has been accomplished in order to investigate the applied science of

Solar Energy systems equipped by a Solar Tracker. A solar energy tracking system was

mechanically designed in SolidWorks and a prototype was manufactured using mainly

existing components. A simple Arduino micro-controller board was designed which

functions with the physical model in order to create a dynamic solar tracking system.

Dynamic solar tracking systems is a proposed approach in order to increase the overall

energy received by a solar panel. Testing the physical model determined the feasibility of

operating a solar energy system with the aid of a solar tracker. Testing results made clear

to the audience that tracking systems are essential for photovoltaic solar energy systems

when an increase in the overall power of the system is required. Eventually the retail price

and the selling price of the Solar tracking system together with a 100W Solar panel is

calculated to be £440.91 and £551.14 respectively, which are significantly low compared

to other solar trackers available in the industrial market.

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Acknowledgements

I would like to express my deep gratitude to Dr Sanja Dogramazi and Dr Ramin Amali, my

supervisor and my module leader respectively, for their guidance, patient, encouragement,

critiques and everlasting help on this thesis. I would also like to thank and show my deep

appreciation to Nahuel Lavino, a graduate student of University of the West of England,

who spent much of his time in order to make clear to me some electronics principles while

helping me to take the real time testings.

Last but not least, I would like to thank “Harwal Group of Companies” and their

technicians who allowed me to work in their workshop and provided me with useful

manufacturing tips and advices in order to manufacture the Solar Tracker Prototype.

Finally I would like to thank my parents who provided me with courage and moral support

throughout my degree and especially during my final year project.

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Table of Content

Introduction .......................................................................................................................... 5

Motivation of the Thesis .................................................................................................. 5

Justification of the Thesis ................................................................................................ 5

Aims and objectives ......................................................................................................... 7

Applied Science on Solar Energy (tracking) Systems ......................................................... 8

Solar cells .......................................................................................................................... 8

Solar tracking theory ..................................................................................................... 10

Literature Review ................................................................................................................ 11

Solar energy system timeline ......................................................................................... 11

Prior Art on Solar Tracking Systems ........................................................................... 12

Tracking Techniques ............................................................................................................................... 13

Tracking system ....................................................................................................................................... 15

Solar sensors ............................................................................................................................................ 16

Solar Tracking Motion ............................................................................................................................. 18

Paraphernalia ................................................................................................................. 19

Application of Solar Energy Systems ........................................................................... 20

Solar Tracking System Methodology and Design ............................................................. 23

Methodology ................................................................................................................... 23

Concept & idea / Output Requirements ................................................................................................... 24

Alternative designs and Design Selection .................................................................... 25

Computer- Aided and Physical Design .............................................................................. 28

Computer-Aided Design ................................................................................................ 28

Implementation and Manufacturing Process .............................................................. 31

Electronic Design ........................................................................................................... 50

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Micro-controller Board ............................................................................................................................ 50

Motor-driver Board .................................................................................................................................. 51

LDR (Light Dependant Resistors) ........................................................................................................... 51

Remarkable Outputs and Experimental Results ............................................................... 54

Cost Analysis .................................................................................................................. 54

Do-It-Yourself Product .................................................................................................. 57

Real time-Testing of the Universal Solar Tracker ...................................................... 58

Method and Calibration of testing ........................................................................................................... 58

Fix position solar system Scenario .......................................................................................................... 60

Universal Solar Tracker Scenario ................................................................................ 62

Power produced: Fix position Vs. Universal Solar Tracker ...................................... 63

Future Modifications and Conclusion ............................................................................... 64

Extension kit Scenario ................................................................................................... 64

Conclusion ...................................................................................................................... 66

Reflective Statement ...................................................................................................... 67

Appendices .......................................................................................................................... 69

References ........................................................................................................................... 70

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Introduction

Motivation of the Thesis

Greenhouse effect has given rise to global warming due to the excess amount of CO2 in

the atmosphere resulting in unpredicted climate changes worldwide; an integral concern

for the world. John Mankins (2010), a 25-year NASA Veteran and head of the IAA study,

said “There is a consensus among scientists that greenhouse gas emissions pose a great

risk of irreversible global climate change. Hence, during the course of the century, it

seems critical that the mix of energy sources must shift away from fossil fuel, even as the

overall demand for energy soars.” Thus it’s significant that humanity and scientist

concentrate on reducing this phenomenon via alternative ways of producing energy rather

than fossil fuels; environmentally friendly and mainly obtained from natural sources such

as wind, sun and water. “You’d be hard pressed to find another industry with 26% job

growth rate for 2011” said by Rhone Resch (2011) president of the Solar Energy

Industries Association. In addition to that, Navigant Consulting states that by 2025, more

than 25% of nation’s energy must origin from solar energy. Both statements referred to a

considerably new way of energy production which seeks into the nearest future to capture

a big share in the world of energy and manufacturing, called Solar Energy.

Justification of the Thesis

Photovoltaic system, also known as solar energy system is considered to be one of the

leading and widespread alternative way of energy production worldwide. The term

photovoltaic is a combination of two words: the “φως” (phos), which means light, and

“volt”. In simple words, photovoltaic can be defined as “electrical energy provided from

light”. Solar energy systems use the radiation emitted from the sun and convert it directly

into electricity, using solar cells that exploit the properties of semiconductor materials such

as silicon.

Solar energy coming from the sun is unlimited and free of cost. In addition, silicon (raw

material) is the most abundance element on earth. It is an environmentally friendly

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technology as no pollutants are caused by power generation. Furthermore, solar energy

systems can be connected to electricity grids in order to sell the generated electricity and

provide an economical benefit to the investor. Due to the various benefits solar energy

systems offer to the world, the range of application around this technology has rapidly

increased; thus consumer’s demand appears to be at a higher level too. According to

Navigant Consulting, in 2013 global PV market will jump to 2.5 times more than 2008. By

2025 more than 25% of nation’s energy must come from solar energy. Thus, it is

significant that this alternative way of energy production can guarantee to be long lasting

and competitive in the market.

Improvements need to take place for the creation of more reliable and efficient solar

energy systems. Mainly, designers concentrate on the intensity source of radiation and

ways of storing the productive energy. The proposed and most effective way of improving

the efficiency of the system is by setting the system to continuous and direct exposure to

the intensity source of radiation; thus, collecting more energy over time.

There are two methods for increasing the mean intensity of solar radiation received by a

solar. The first method is by focusing the incident ray onto a rigid array, this will force the

incident-ray’s path to reach normal to the array surface. The second method is the use of

solar tracking system, which operates by tracking the radiation of the sun. Solar tracking

systems are divided into two categories; dynamic tracking and fix control algorithm

tracking.

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Aims and objectives

The main aim of this thesis is to create an engineering design prototype and demonstrate

the benefits of a solar tracking system. Testing in real life the prototype will prove that a

solar tracker can increase the efficiency of the system. Initial objective of the thesis was

the design of a single axis solar tracking system operated by a dynamic tracking system.

However the limitations a single axis system has on the aspect of geographical position of

the system, changed the system’s configurations to a dual-mode axis; aim for a worldwide

market; thus, Universal Solar Tracker. Eventually testing the product in real life together

with a cost analysis will exhibit the feasibility of the investment for both a manufacturer’s

and an investor’s point of view. In addition it validates the benefits aided by a solar

tracker. Potential improvements and modifications of the prototype will conclude this

thesis.

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Applied Science on Solar Energy (tracking)

Systems

Solar cells

Sunlight is integrated from photons, small particles of energy. Nuclear fusion reactions

that take place on the surface of the sun supply earth with energy. In fact, energy received

from the sun per minute is greater than the energy used by the world per year. Energy

primarily arrives to earth in the form of electromagnetic radiation, where electrons are

released from their atoms. Solar cell is a semiconductor device structured with p-n junction

diodes. P-n junction diodes are capable of generating a single direction current flow in the

presence of sunlight. A solar element is made of silicon and is usually square in shape,

with dimensions 120-160mm. There are two types of silicon available for the manufacture

of a solar cell: the amorphous and crystalline silicon. The latter one is divided into mono-

crystalline and poly-crystalline.

Poly-crystalline Mono-crystalline Amorphous Thin Film

efficiency Good (12-15%) Good (13-17%) Low (6-8%)

Cost scale 2 3 1

Watts per m^2 120-150 135-170 60-80

Outstanding

operating conditions

Hotter conditions Cooler conditions Hotter conditions

(less expensive in cooler

conditions)

Life span 25-30 years 25-30 years 3-6 months

Table 1-Types of Solar Panels

When the procedure described above takes place, direct current flows through and a charge

controller is maintaining the current flow accordingly in order for the sufficient amount of

current to arrive to the power supply. Energy is then stored in the power supply for later

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use. When energy is required from an appliance, DC power flows from the power supply

to the inverter, where DC power is eventually converted to AC voltage.

Figure 1-Solar Energy System [Available from: http://www.nuffieldfoundation.org/practical-physics/motion-sun]

In order for photovoltaic technology to be competitive in the market, improvements are

necessary. There are three proposals for improving the system: solar cell efficiency,

intensity source of radiation and ways of storing energy. Photovoltaic user’s proposed and

meanwhile simpler way to improve efficiency is by tracking the position of the sun Figure

2- The motion of the sun [Available from: http://www.nuffieldfoundation.org/practical-physics/motion-sun]thus

increasing the intensity source of radiation.

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Figure 2- The motion of the sun [Available from: http://www.nuffieldfoundation.org/practical-physics/motion-sun]

Solar tracking theory

Since both sun and earth don’t have a fixed position, a solar energy system, using the

mechanical advantages provided from a solar tracker, can face the sun directly and

continuous, thus optimize the operation of solar energy receivers. A solar tracker can

increase the sufficiency of a solar energy system by an extra 30%.

Figure 3- Solar Tracker [Available from:http://www.projectfreepower.com/solar-power/building-a-sun-tracker.html]

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Advantages and Disadvantages of solar tracking systems

Solar tracking systems have the following advantages:

• Improves the efficiency of the photovoltaic system by 30% for single axis and an additional 16% for dual axis.

• Reduces the number of panels required in a system; thus reducing the cost of the overall investment.

• Environmentally friendly technology since no pollutants are caused by power generation. • There is no need of electricity; instead solar energy is used for the system to operate. • With proper control of algorithms inputted in the system, tracking is done automatically. • Cheap and easy to install compared to other methods of improving a solar energy system. • Investment is only required once. • Long lasting. • Low maintenance is needed in order to ensure the accuracy of the system.

Solar tracking systems have the following disadvantages:

• Large surface area is essential. • Expensive investment. • Maintenance is needed in order to ensure the accuracy of the system. • Extra costs and expenses to a solar energy system.

Literature Review

Solar energy system timeline

Going back to 1830, the first solar cell technology research was initiated by Edmond

Becquerel (1830). After 9 years, he was eventually credited with the “Solar Panel

Research” after observing the photovoltaic effect.

However this technology was not applied in real life until 1860s. Auguste Mouchout

(1860) a French mathematician, he was funded by the French monarch for further research

in solar energy. He designed the first motor that could operate with solar energy systems.

In addition he also invented the first solar- powered steam engine.

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Charles Fritz, in 1883, was named as the first person to create a solar energy system that

would turn solar energy to electricity. He used junctions that were created when the

semiconductor was coated by a thin layer of gold.

The solar energy development was an on-going challenge, and around 1904, Henry

Willsie, was accredited with the honours of the first person who managed to store energy

for later use.

In 1941, Russel Ohl accidentally discovered the potential of silicon for use in solar

technology at Bell Laboratories. The first silicon solar panel had an efficiency of 1%.

By 1956, commercial solar cells were available in the market. However they were

extremely expensive at that time ($300 per watt).

Continues researches and developments related to solar energy systems all over the world

lead us to 1999 were photovoltaic capacity reached 1000 megawatts.

The low efficiency solar energy systems have is still an issue in nowadays. Today solar

cells have an efficiency of 15-17%. They highest efficiency achieved was 40% by HEMM

solar cells created in 2007 by the National Renewable Energy Laboratory and Boeing

Spectrolab.

Prior Art on Solar Tracking Systems

Technology is surrounded by constrains. Similarly, a solar energy systems encompass

various obstacles. The main challenge faced by solar energy system researches is to

increase the overall efficiency. This can be achieved the contribution of a solar tracker to

the system, as already mentioned. The way the solar tracker contributes with the system is

divided into the following aspects: Tracking techniques (dynamic or fix control algorithm),

tracking system (single or dual axis), Sensors justification and Solar tracking motion.

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Tracking Techniques

Control signals of solar tracker are inputted via 2 techniques: fix controls algorithms and

dynamic tracking.

Fix control algorithms use a controller, which works along with control algorithms that are

set according to the geographical position and current time of the system. Records of the

intensity the sun has throughout the year are used as an input for the fixed controlled

algorithms method. A controller device is used to move the system to the position that

faces the maximum intensity of solar radiation at specific times.

The second method is dynamic tracking, which operates using photo sensors. These photo

sensors can instantly determine the current latitude of the radiation source where the higher

energy emission can occur. Signal from the photo sensors are sent to the controller and the

motor drives accordingly. If earth was flat and did not rotate, the fix control algorithm

would have been as accurate as dynamic tracking. Depending on your geographical

position, azimuth angle varies. You can also lose up to three hours of charging, due to the

unpredictable exact time of sunrise and sunset. Thus dynamic tracking is more efficient

than fixed control algorithms, since tracking is done instantly according to the photo

sensors. Additionally, dynamic tracking is more reliable in unexpected climates compared

to fix control algorithms. This is because fix control algorithms are set according to the

expected weather conditions.

In 2009, Nelson A. Kelly and Thomas L. Gibson, made a research called “Improved

Photovoltaic Energy Output for Cloudy Conditions with a Solar Tracking System”; a

research regarding the benefits a solar tracker can provide to a solar energy system. A

detailed description of the theoretical and experimental procedure is included, where a

fixed control algorithm dual –axis solar tracker was used to determine the operating mode

that a solar tracker should run during overcast condition. Referred to the features of a fixed

controlled algorithm method, a FCA system will not be able to produce peak energy at

times where unexpected climate conditions can limit significantly the light intensity

received from the sun to the earth. Concluding with the analysis of data demonstrated;

during overcast conditions, solar panels tilting away from the zenith-axis will cause

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irradiance to decrease in the horizontal configuration and thus improve the overall

efficiency of fixed control algorithm solar energy systems. In order to avoid complexity,

while producing a more efficient solar energy system, fixed controlled algorithm method

should be replaced by dynamic tracking.

In addition,Azhar Ghazali M. and Abdul Malek Abdul Rahman, in 2012, also made an

efficiency research called “The performance of Three Different solar Panels for Solar

Electricity Applying Solar Tracking Device under the Malaysian Climate Condition”. A

dynamic, single axis solar tracker was used to determine the efficiency of poly-crystalline,

mono-crystalline and amorphous silicon solar panels, which were tested under the hot and

humid climate in Malaysia. Poly-crystalline photovoltaic panels have shown better

performance ratio and average panel efficiency. As mentioned previously, Mono-

crystalline PVP provides us with higher efficiency, contrariwise, in Malaysia’s weather

conditions Polly-crystalline PVP performs best. In UK, where the climate is cooler, Mono-

crystalline PVP would function best.

Figure 4-Dynamic Solar tracking diagram

Solar panels

Motors Photo-sensorController

Radiation source

sunlight is emitted from the solar

panels

Photo sensors determining

radiation source

Motors rig with two axis

Motors rotating the photo sensor

Provides signal to turn the motor and

solar panels

Signals sent to controller when sensor detect

sunlight

Power supply

Power suply

Excessive energy stored for later use

Power Supply for solar tracking

system

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Dynamic tracking operation is divided into three main functioning operations. These

operations are: tracking system, justification of solar sensors, and solar tracking motion.

All three operations are described in detail below.

Tracking system

This operation includes a device, which orients solar panels towards the sun. Trackers are

added to a solar energy system in order to increase the output of the system. There are two

common designs for tracking: single axis and dual axis.

Single axis solar trackers track the sun in only one direction. Axis direction is determined

according to the geographical position of the system. In tropical regions, where the sun

gets very high at noon but the days are short, horizontal axis is used. Meanwhile, vertical

axis is used in high latitudes, where the sun does not get very high and days are longer.

Single axis tracker can increase the annual output of a solar energy system by a minimum

of 30%.

Figure 5- Single-axis Solar Tracker [Available from: http://www.solarchoice.net.au/blog/solar-trackers]

On the other hand, dual axis solar trackers, involves tracking the source of radiation in

both horizontal and vertical axle. This type of solar trackers can operate with the same

efficiency all over the world due to the dual-axis commands it can receive. Dual-axis

tracker can increase the annual output efficiency by a minimum of 36%. However, they are

more mechanically complicated in designing and installation. Two motor are usually used

for dual axis instead of one for a single axis.

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Figure 6- Dual-axis solar tracker [Available from: http://www.solarchoice.net.au/blog/solar-trackers

Francisco Javier Gomez-Gil, Xiaoting Wang and Allen Barnett, in “Energy Production of

Photovoltaic Systems”, in 2012 demonstrated a comparison of energy production and

performance ratio of three photovoltaic system configurations: fixed, 1-axis and 2-axis

tracking flat plate, and concentrating photovoltaic. Detailed analysis and real time

performance of these types of PV system configurations were tested in Spain; Gain in the

annual energy production: 22.3% for single-axis, 25.2% for dual-axis and 16.1% (close to

fixed position) for CPV. A dual axis solar tracker will provide you with the higher energy

production, where a single axis solar tracking system follows with a small difference of

2.9%. The difference between the two moving systems and the CPV is significantly large.

Thus, according to your design principles, a choice between the two systems that are in

motion should be taken.

Solar sensors

Light sensors detect and determine the solar radiation source for a solar tracker. Feedback

from the sensors is then sent to the controller for process. The output of this process is

used to control the movements of the motor accordingly. In a dynamic tracking system the

following sensors are used for both absorbing energy and determining the solar source.

The types of sensors, which are functionally preferred for a solar tracker, are:

• LDR - light Dependent Resistors: This type of sensors response to light visible on

the human scale. Their resistance increases as light intensity increases. This sensor,

also known as photo-resistor, is useful for detecting light. It will fit in a dynamic

tracking system for providing signals for the movements of the motor. LDR are

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small, cheap and low power users. They are also simple and liable. LDR are mostly

used as automatic switches for devices, such as outdoor lights.

• Photovoltaic light sensors are also called solar cells. This type of sensor is

responding to light intensity by converting sunlight energy into electrical energy.

Energy is then stored in silicon cells. Solar cells provide us with DC current and

the efficiency is about 30%. They have a life expectancy of 25 to 30 years. Solar

cells are mostly used in watches and calculators due to their small size and the low

wattage they provide. However, they can be combined together to provide large

amounts of current. A combination of solar cells is used in solar panels for a solar

energy system. Again these types of sensors respond to light visible on the human

scale.

Other types of sensors:

o Photodiode is a PN junction diode, which has a transparent casing in order for

light to be able to reach the junction. When light is received from the junction,

either current or voltage is generated. Photodiodes have very fast response;

however the current flow is relatively small.

o Phototransistor is a photodiode, which operates with amplification. It is an

NPN transistor and is more sensitive than photodiode. The frequent response of

a phototransistor is not good; however, it can provide 50-100 times greater

output than a photodiode.

In 2011, as a part of Renewable Energy, C.S. Chin, A. Babu and W. Mcbride wrote a

thesis called “Design, modelling and testing of a standalone single axis active solar tracker

using MATLAB/Simulink”. Different operating modes are provided to the user based on a

dynamic tracker. Two light-dependent resistors (LDR) sensors were installed on the

surface of the PVP. The system was also designed in MATLAB in order to predict the

outcome. Experimental testing agreed partially with the expected outcome. Mainly, the

reliability of the solar tracker to follow the sun continuously was not at a high level

resulting to less energy production.

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Solar Tracking Motion

Signals provided from photovoltaic light sensors are sent to the controller for analysis. The

output of the analysis is used as instructions, which are forwarded to the motor. Motors are

used to drive solar panels at the direction of the sun in a solar tracking system. The most

common types of motors used for solar trackers are stepper motors. A stepper motor is a

brushless DC electric motor that moves in steps. They are made of permanent magnets and

coils surrounding the magnets. As a result an electromagnet is produced. Magnets rotate in

a rotating shaft called rotor. The operation of stepper motors is easy, and the number of

steps performed can determine the distance travelled. Signals received from the controller

of the motor are used to control the speed. The most common and basic type of stepper

motor in the market is the Permanent-magnet stepper motor. The rotor of the permanent

magnet motor has a permanent magnet with two or more poles, in the shape of a disk.

Coils surrounding the magnet will attract or repulse the permanent magnet and as a result

torque is generated. Permanent-magnet stepper motors are divided into two types of motor:

• Unipolar stepper motor: A rotating permanent magnet that is surrounded by four

coils. The controller needs four output lines to operate. It also contains four

electromagnets. Current flows in one direction through each coil in repeating

patterns.

• Bipolar stepper motor: On the other hand, this type of permanent-magnet motors

requires two coils, half required for the unipolar. This specification makes it

cheaper than unipolar stepper motors. However, bipolar stepper motors lack centre

taps and as a result bipolar motors require a different type of controller to operate.

They need a controller that can reverse the current flow through the coils by

alternating the polarity of the terminals. Higher torque is achieved using bipolar

stepper motors.

Other types of motors:

o DC motor: Direct motor is one of the simplest motors existing. They work with

a direct current supply. A permanent magnet is coiled up with loops of wires to

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the stator. Current flows through the field of coils; from the negative to the

positive terminal. As a result, voltage is induced in the windings opposing the

current flow. It is not easy to determine the control of the speed of such a motor

because a DC motor spins very fast and insufficient torques are created. The

fast spin it provides is used for applications that require fast speed.

o Servo motor: A servo motor contains a DC motor. Electric input is used to

determine the position of the armature of a DC motor. As the motor rotates, a

variable resistor changes; and as a result the direction and position of the

motor’s shaft can be detected. If the desired position is achieved, the motor’s

power supply is stopped. The speed of the motor varies according to the

difference between the current position and the desired position of the motor.

The speed is proportional with this difference. Servo motor is popular due to its

small size and its accuracy. However, full revolutions are not applicable

(usually between 180-270 degrees).

Paraphernalia

In addition to the above mechanisms and systems required to drive and operate the solar

energy system, more equipment are essential, mainly for adjusting the configurations of

the voltage:

• Inverter - the electricity generated by a solar cell comes in the form of DC current.

Special equipment designed to transform the output voltage into AC voltage is

used. As a result, a solar energy system can provide energy to equipment running

with an alternative current.

• Storage batteries - electricity generated by the solar panels is stored in batteries.

Batteries can be connected in series or parallel in order to achieve the desired input

voltage for the inverter. The most common battery used is the deep cycle lead acid

battery. This type of battery is divided into:

1) Flooded type, also known as wet cells, that is filled with fluid. The main

advantage of a flooded battery is that despite being bulky, it is very

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economical. They are commonly used as solar batteries since they can

provide the required energy for an off-grid system or high power loads.

2) Sealed type, also known as absorbed gas mat batteries. They have pads

that were previously soaked in fluid. These pads are structured between

the plates of the battery. They are small and mainly used for lower

power equipment. Voltage of sealed batteries is lower than voltage of

flooded batteries, due to the limited fluid existing in the flooded type.

• Charge controllers - Charge controllers are used to prevent overcharging and

discharging the batteries. This is because excessive voltage can result in the

damage of the battery. A charge controller maintains the rate of charging the

batteries. Proper charging will avoid damage and increase the life and performance

of the batteries. Charge controllers are divided into three stages:

1. Bulk Stage- the voltage steadily increases to the bulk level (usually14.4-

14.6 volts) while the batteries draws maximum current.

2. Absorption Stage - voltage is maintained at bulk level for a specified time.

Meanwhile current gradually tapers off as the batteries charge up.

3. Float Stage - after the absorption stage, voltage is lowered to float level

(usually 13.4-13.7 volts) and batteries draw a small maintenance current

until the next cycle.

Application of Solar Energy Systems

Since the early stages of solar energy’s development, the range of application has never

been limited. In fact, in the early years of solar energy, 1955, William G. Cobb of the

General Motors Corp. (GM) displayed his 180 mm “sunmobile”, the first solar energy

automobile.

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The everyday use of systems powered by solar energy is increasing day by day. Solar

energy systems are now added in many systems due to the reduction in cost over the years.

Such systems are listed below:

1. Cell phone charger

2. Notebooks

3. Radio

4. Solar calculators

5. Auxiliary power in boats and cars

6. LCD displays

7. Traffic lights

The low efficiency solar systems have, limits the range of application in systems that

require a higher amount of power to operate such as cars. However solar energy system

can be connected to electric network grids. Photovoltaic parks are becoming popular since

the investor can sell the stored electricity. In addition, due to the environmentally friendly

behaviour of solar energy systems, government funds are available encouraging the

investor for a higher net profit. In 2012, in USA, Youma country, AZ, the biggest

photovoltaic park was installed. It generates a power of 250MW.

Furthermore, extra add-ons appear in modern designs such as strength kits and wind

turbines while, other designers provide us with portable designs in a variety of shapes and

sizes. Designs to fit caravans (Figure 7- Portable solar energy system [Available from:

http://www.patriotsolargroup.com]) and portable aluminium solar energy cases are two

examples of the expansion in the market solar energy gained over the years. These lead

one to conclude that designers of solar tracking systems aim to produce designs that have s

stable, reliable and accurate design alignment, while costing less to the customer and

performing as effectively as possible, according to the consumer’s needs.

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Solar panel fitting in trucks are available from Patriot solar group. Panels are installed on

trucks replacing fuel generators.

Figure 7- Portable solar energy system [Available from: http://www.patriotsolargroup.com]

A bag designed mainly for campers. Solar panels fitted on the bag provide the user of the

bag with energy. The bag is available in the web community, where more unique solar

energy designs are available.

Figure 8-Solar panel bag [Available from: http://www.voltaicsystems.com/fuse4w.shtml]

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Solar Tracking System Methodology and

Design

Methodology

Design can be defined as a drawing or model. However, through the vision of an engineer

design is defined as problem solving process; art with a purpose. The following design

principles demonstrated in the diagram below, were used to derive the concept requirement

and produce a final design.

Figure 9- Methodology diagram

Concept & Idea

Output

Requirements

Mechanical and

Electrical

Design

Modifications (if

required)

Physical Model

Testing Output Results

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Concept & idea / Output Requirements

The main concept and idea of this thesis is to design an efficient Solar Tracking System.

Solar energy and solar tracking systems were examined in detailed and meanwhile

overview assumptions were recorded. The next step will determine the output

requirements that are necessary for this system. Table 2- Aspects and Features indicates

the main design features that will form the foundation of the design.

Aspects and features Explanation

Dynamic Tracking Photo Sensors are used for tracking instead

of fixed control algorithms.

Dual-Axis Earth and Sun both rotate.

Cheap Product Cheap components, reduce raw material.

Display the increase in efficiency of the

overall system

Dual- axis, dynamic tracking. Best proposed

method in solar tracking.

Stability Stiff product, wind resistance, raw material

used.

3- mode system Fixed, Single Axis, Dual-axis functions.

Display the investor’s benefit. Energy used to drive the system< excess

energy provided from the solar tracker.

Foundation for extra PV panels. Availability for the user to add more PV

panels on the system.

Universal solar tracker Being able to work both in the northern and

southern hemisphere

Table 2- Aspects and Features

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Alternative designs and Design Selection

Having in mind the features mentioned above, three proposed concepts of dual- axis solar

tracking system were designed, using SolidWorks. Each of the design can track the solar

radiation using different techniques. A design selection process is vital in order to

determine the best suitable design this project. A description of the proposal designs is

provided below.

Design 1: Two Rotational Actuators

The first design involves two rotational actuators for controlling both axes. Design 1’s

main disadvantage is the limitation in support for the solar panel thus external forces such

as wind can force the solar panel to rotate and loose accuracy.

Figure 10- Design 1

26


Design 2: Two Linear Actuators

The second design involves two linear actuators for controlling both axis. It is consider to

be an effective and simple design.

Figure 11- Design 2

Design 3: One Rotational and One Linear Actuator

The third design includes one linear actuator, for controlling the movements of the system

along the azimuth-axis, and one rotational actuator, for rotating along the x-axis. This

design is integrated by using the main benefits and ideas from design 1 and 2. It has a

stable and accurate approach of tracking sunlight.

Figure 12- Design 3

27


Moving on, a criteria analysis was undertaken in order to display the advantages and

disadvantages of each design, in order choose the most appropriate one. Stuart Pugh, in

1996, published a criteria analysis procedure through the book called “Creative Innovative

Products Using Total Design”. The criteria analysis performed for the solar tracker is a

simplified procedure to the one written by Stuart Pugh. A choice of criteria were used and

credits were acknowledge to each feature according to their significance; not significant: 1,

significant: 2 and very significant: 3. Eventually an average score was calculated to

determine the most suitable design. An excel database was created for the feature analysis.

The Display sheet shows the score that each design achieved on each criterion from with a

scale out of 10. The score is discussed and backed up in the respective sheet of each

criterion [Appendix B].

Criteria Design 1 Design 2 Design 3 Credits

Risk of Failure 6 8 9 3

Power Consumption 7 9 8 3

Cost 9 6 8 2

Life Span 5 7 9 2

Maintenance requirements 6 7 9 2

Weight 9 8 7 2

Ease of Manufacturing 6 8 7 1

Raw material 8 7 6 1

Installation 7 9 8 1

Potential extension 6 5 9 1

Average Score out of 10 6.9 7.6 8.2 18

Table 3-Design selection score

28


Design 3 obtained the highest average score. It provides us with an efficient method of

alignment both in stability and reliability. Additionally, it achieved the highest score in 4

out of 9 of the criterion and most importantly for the one regarding the risk of failure. Thus

the next stage was to mainly concentrate on the disadvantages of design 3 and attempt to

create an improved and more effective system.

Computer- Aided and Physical Design

Computer-Aided Design

The proposed design needs further improvement in order to produce a mechanical system

that will be as efficient as possible. SolidWorks allows the user to produce detailed designs

and simulations to display the output performance in different aspects and condition. The

final design of the dual-axis solar tracking system is shown below.

Figure 13- Suitable design

The design can be divided into the bottom part and top part. The bottom part involves a

cylindrical tube, which can be used as a protective case for electronic miscellaneous. The

tube also supports the whole system by applying a vertical force to the base (balance the

system). A shaft installed at the centre of the tube is rotated by the gearbox attached to it.

On the top edge of the shaft, a disc is placed that rotates the top part.

29


Figure 14-Bottom part

Regarding the top part of the design, two isosceles rectangular tubes are used as a support

for the PVP. An extra support tube is used to connect the two diagonal tubes. Hinges

connect the tubes with the PVP allowing circular motion. Meanwhile, a linear actuator,

which stands on the disc, is hinged to the centre of the lower part of the PVP forcing it to

move along the azimuth axis when operating. The shaft rotates all three components.

Initially, a ball groove bearing was installed at the top part of the cylindrical tube.

However, the diameter of the tube requires a bearing with a significantly large diameter;

thus, increasing the total cost. As a result, bearings were relocated. A deep groove ball

bearing and a thrust ball bearing were fitted in the bottom edge of the shaft. Finally,

compared to the proposed design 3, the linear actuator is now positioned on the cylindrical

tube. Due to the limitations in the range of movements allowed to the linear actuator when

placed in the tube, the linear actuator is now fixed perpendicular to the disc. This

modification increases the total height of the design. In addition, as mentioned above, a

horizontal tube is connected perpendicular to the isosceles tubes, providing support to

them and reducing the overall stresses across the design. These were the most important

changes made to the design

Cylindrical

tube

Shaft

30


Figure 15-Top part

Furthermore, design embodiment procedures were undertaken in order to ensure that the

system would not fail. The most significant component of the system is the shaft, since

both vertical and torsional forces are acting on it with the possibility of failure. The most

important specification of the shaft needed to be determined was its diameter.

Since we know that 𝜎! =

!! and 𝐹𝑂𝑆 = !!

!! Equation 1

Where σz is the normal stress, F is the force, A is the area and Sy is the Yield strength.

Then minimum diameter of the shaft is 2 mm [Appendix D] from the equation shown

below:

𝐷!! !×!

!×!!!"#

Equation 2

Using the minimum diameter and the total weight of the top part of the system, which is

22.88Kg the system can be manufactured with a minimum FOS of 3.

Hinges

Horizontal tube

31


Implementation and Manufacturing Process

Having available a workshop in Sharjah, UAE, for the needs of “Harwal group of

Companies”, I was able to understand and apply in real time different types of

manufacturing processes and procedures in order to create a physical model of the

designed solar tracker. Through the use of existing components, manufactured by the

factory, a solar tracker was built at a low cost.

As an initiating step, a shaft was chosen. The diameter of the shaft used is 44mm and it has

a height of 500mm. It is made of mild steel. Yield strength and Young modulus were taken

according to the specifications of SolidWorks for Cast Carbon Steel as 248MPa and

200GPa respectively. The diameter of the shaft is 44mm, which is 22 times greater than

the minimum diameter required in order for the system not to fail. The reason behind this

is mainly due to the small range of gears available on the shelves of the workshop. The

driven gear was welded on the shaft to a height parallel to its driven gear.

Figure 16-Shaft

A bearing case consists of a deep groove ball bearing and a thrust ball bearing was used as

a base while also supporting for the shaft. The bearing case was screwed on a square base

with dimensions 520*520 mm. The square base was initially made of steel. However, the

steel was replaced by PVC due to the lighter weight properties it has. PVC is suitable for

32


all weather conditions; thus, avoiding the need for galvanising the steel. The same applies

for the choice of the cylindrical tube, which is used as a protective case for electronics and

as an overall support for the system. The cylindrical PVC tube used was an existing pipe

manufactured by the factory. The cylindrical PVC tube and the square PVC base were

joined together by welding.

Figure 17-Exploded assembly shaft and bearing case

The final stage regarding the manufacturing of the bottom part of the system had to do

with a cylindrical disc made of steel, which was welded at the top part of the shaft. The

disc has 4 symmetric holes and a bigger hole located at the centre of its cross sectional

area. The four symmetric holes were used in order to screw the disc with a PVC disc,

which functions as a countersunk for the cylindrical PVC pipe. The centre hole was used

to fit the shaft in. Due to the fact that the diameter of the shaft was greater than the fitting

diameters of the bearing case and the steel disc, the shaft was grinded at its two edges in

order to fit the steel disc centre hole and the bearing case respectively.

Shaft

Bearing Case

Cap

Thrust

Ball Deep Groove

Ball Bearing

Bearing Case

33


Figure 18-Bearing case 2D drawings

The construction of the bearing case was the most complicated part this project. For that

purpose, lathe, drilling and grinding were required. A cylindrical steel beam was used with

a diameter of 136mm. The beam was then turned by lathe with a depth of 14mm and a

height of 43mm. A drilling machine was then used to create holes according to our needs

as indicated in Figure 18-Bearing case 2D drawings. The diameters of the Bearing and the

shaft, determined the internal diameters of the holes, in order for them to fit in. Eventually,

holes were drilled in order to connect the case with the PVC base and a cap was attached

on the top of the bearing case to hold it stable.

Figure 19-Bottom part annotations

Steel Disc

(welded to

the shaft)

PVC Disc

(screwed to the

steel disc)

PVC Cylindrical

Tube PVC

Square

Base

34


Additionally, regarding the top part of the system, two hollow rectangular steel tubes were

cut, de-burred and finally welded on a flat steel sheet in an angle, so that the horizontal

distance of the two top edges of the tubes would be equal to 1165 mm, which is the

distance between the two hinges. The hinges were then bolted on the PVP and the steel on

the PVC cap accordingly. A third tube was cut, which was welded at an angle of 26

degrees to the isosceles tubes as an extra support, reducing the overall forces acting in the

structure. All three tubes and the sheet of steel were galvanized; thus, preventing

corrosion.

Tube Length (mm) Angle at the edge (degrees) Quantity

1 1205.5 26 2

2 614 26 1

Table 4-Tubes

Figure 20-Top part annotations

Tube 1

Tube 2

Hinges screwed on the

solar panel (1165 mm)

Welded

joints Steel sheet

35


The next step included drilling of the PVC disc. Holes were drilled in order to meet the

dimension criteria of the linear actuator and the isosceles rectangular beams. The

horizontal distance (passing through the centre) between the isosceles legs and the linear

actuators’ position (which was perpendicularly hinged on the PVP when the PVP was at an

angle of 45 degrees) was measured to be 295.5mm. Thus, holes were drilled accordingly.

Eventually the hinges were welded on the top horizontal edges of the two beams.

Figure 21-PVC disc 2D drawing

Finally, assembling the bottom part and the top part resulted in a dual axis solar tracking

mechanism. The limitation in the range of components determined the overall size of the

system. The overall mechanism size, which was mainly integrated by the shaft’s diameter

and the linear actuator’s height, appears to be overdesigned as it has the tolerance in

reducing the overall size of the design, thus decreasing raw materials/manufacturing cost.

36


Shaft

A shaft can be described as a mechanical component, which transmits rotational motion. It

is essential for mechanical systems that are rotated by a motor or an engine. A static

analysis is crucial in order to display the combined stresses, because of the existence of

torsional shear and normal stresses due to bending.

As an initiating step, the minimum diameter of the shaft was calculated to be 2mm. A shaft

of 44mm diameter and 0.5m height was used.

Euler Buckling and J.B. Johnson procedures were then performed in order to prevent

failure.

𝐸𝑢𝑙𝑒𝑟 𝐵𝑢𝑐𝑘𝑙𝑖𝑛𝑔!!!!!"!!

Equation 3

Where:

𝐼!!!!

! Equation 4

And

!.!.!"!!"#!(!"#)! !

𝑆! −!!!!∗ !!

!∗ !!"

Equation 5

Where: I-second moment of inertia, L-length of shaft, K-radius of gyration, E-young

modulus, T-Torque and C can be obtained from the table below:

Table 5-Constant C

Furthermore, the torque of the shaft was calculated in order to find its efficiency.

𝑇𝑜𝑟𝑞𝑢𝑒(𝑇!)!!∗!!∗!!

Equation 6

37


𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦!!"#$% !"#$%& (!!)

!"#!"# (!! Equation 7

Where 𝑓! is the friction coefficient and𝑇!!!∗!!!

.

Finally, the Factor of Safety (FOS) of the shaft was evaluated using the Von Misses

Stresses Procedure. The Von Misses stresses acting on our shaft are calculated below:

𝜎! =!! Equation 8

𝑡!" =!∗!!

Equation 9

𝑉𝑜𝑛 𝑚𝑖𝑠𝑠𝑒𝑠 𝑠𝑡𝑟𝑒𝑠𝑠𝑒𝑠(𝜎! = !![𝜎!! + 𝜎!! + 6 ∗ 𝑡!"! ]

!! Equation 10

𝐹𝑂𝑆 = !!!!

Equation 11

Where s’ is the Von misses stresses and J is the Polar moment of inertia and it’s calculated from: = !!∗ 𝜋𝑟!

(𝑚!).

38


Equations and known values were input in an Excel database and a simulator was created

to calculate the output values. The crucial values of the simulation are displayed in the

table below:

Shaft

Input Force N 224.5

Material module of elasticity ( E) GPa 200

Material Yield Stress MPa 248

Minimum Diameter m 0.002

Length of the shaft (l) m 0.5

F ( Critical) - Euler N 1801324.775

F ( Critical) - J.B Johnson N 673.339

f ( coefficient of friction) 0.11

Diameter m 0.044

Torque Nm 0.543

e (efficiency) 32.883

σy MPa 0.148

τxy MPa 0.032

Von Misses Stress MPa 0.158

FOS 1569.80

Table 6- Excel template results for shaft

39


In addition, an FEA (Finite Element Analysis) analysis was performed in SolidWorks to

demonstrate the statics of the shaft. FEA is a common design procedure used by designers

in order to perform complex mathematical expressions, where solutions are hard obtained.

By using Meshing technique, which breaks the system down according to your desired

percentage, results can be obtained for any point of the part. An FEA analysis is crucial in

where large stresses are acting on the component. In our case, stresses acting on the shaft

appear to be very small, as calculated from the Von Misses Stress equation; thus

performing an FEA analysis it would indicate stresses to be at their minimum.

Figure 22- Shaft FEA analysis

The first step requires to denoting the forces acting on the shaft. A vertical force of 224.5N

and a torsional force of 0.543 Nm were used for the FEA analysis. The next step required

meshing of the component. Eventually results were demonstrated using a scale of stresses,

denoting a colour for a range of stresses acting on it. Starting from the minimum stress

occurring in our design which is 10,882.9 N/m^2 indicating blue and ending with the

maximum stress of 2,522,566.0 N/m^2 indicated in red. As shown in the Figure 22- Shaft

FEA analysis above, the majority of the system appears to be blue verifying the

calculations in Table 6- Excel template results for shaft.

40


Gear Box

Gears can be defined as components used to transmit motion between two parts. Gears are

crucial parts for a mechanical device. They can be found in everyday mechanism used, as

well as in complex machines used in factories. There are many types of gears according to

your desired output available. The most common types of gears are shown in the table

below:

Type of Gears Description

Spur Gears Have teeth parallel to the axis

of rotation and are used to

transmit parallel motion

http://students.autodesk.com/?nd=showcase_

detail_page&gallery_id=14153&jid=191413

Helical Gears Have teeth inclined to the axis

of rotation in order to develop

thrust loads and bending

couples. Due to the gradual

engagement of the teeth during

meshing, noise is limited.

http://www.enterprise-europe-

network.ch/marketplace/index.php?file=bbs-

show.php&bbsref=07%20GB%20EAST%200IBL

Bevel Gear Have teeth formed on conical

surfaces. Mainly transmitting

motion between intersecting

shafts. http://www.beam-

wiki.org/wiki/Compound_gear#Compound_Gears

Worm Gear Mainly used when the speed

ratios of the two shafts are

quite high.

http://www.stepanlunin.com/Worm_Gear_software.html

Table 7-Types of gears

41


A set of Spur gears was used to transmit parallel rotational movement for the solar tracking

system. Spur gears are the simplest gears; thus, reducing the complexity of the overall

assembly. The gears used/available in the workshop matching our requirements are

displayed below:

Table 8- Chosen gears specifications

Using the above parameters, the train value was calculated to be 0.4 using the following

formula:

𝑇𝑟𝑎𝑖𝑛 𝑉𝑎𝑙𝑢𝑒!!"!"#$%"!"!"#$%&

Equation 12

Since 1892, engineering designers have used the Lewis bending equation in order to

estimate the stress in gears. By dividing the Yield strength of the gears by the calculated

LBS, the Factor of safety of the gears can be determined.

𝐿𝑒𝑤𝑖𝑠 𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑟𝑒𝑠𝑠!!!!!

!"# Equation 13

𝐹𝑂𝑆!!!!

Equation 14

Where Kv is the Dynamic factor, w is the angular velocity, T is the torque and Wt is the tangential

transmitted load.

The final FOS was calculated to be 1260.377, as shown in Table 9-Excel template for the

bending stress of gears. The factor of Safety calculated is too high. A significantly lower

FOS would have been sufficient in our model.

Gear Driver Driven

Pitch Diameter (mm) 60 150

Module 3 3

Number of teeth (Nt) 20 50

Pressure Angle (deg) 20 20

Face Width (mm) 30 30

42


Bending Stress Analysis

GEAR Driver Driven

Torque 0.000109 0.54322302 Nm

Wt tangential transmitted

load 0.003621 7.24297359

N

Wn 0.001318 2.63622679 N

W angular velocity 1.047198 0.83775804 Rad/s

V- velocity 0.031416 0.06283185 m/s

Kv- dynamic Factor 1.000000 1.00000000 Low speed

Lewis bending equation stress 0.000125 0.19676647 MPa

FOS from Lewis 1984555.076 1260.377

Table 9-Excel template for the bending stress of gears

An AGMA stress procedure and a Bending stress calculations were performed [Appendix

D] where the final results are shown in the table below:

Driver Driven

Bending FOS 144554.479 125.6846804

AGMA stress Equation 0.003 3.788

Table 10-AGMA stress equation

Eventually, by calculating the FOS from Lewis bending stress and AGMA stress equations

we can ensure that gears will not fail and that they can transmit the required torque. The

next step involved the assembly of the gears. A base was created, which will hold the

rotary actuator and the gears at a fixed position, as indicated in Figure 23-Gear assembly .

In addition, a solenoid was added on the base which will be activated when the gears are

43


not in motion in order to hold the gears still and avoid motion caused by external winds

acting on the solar panel.

Figure 23-Gear assembly

Linear Actuator

A linear actuator was used for tilting the PVP along the azimuth axis. A relatively cheap,

low weight and meanwhile powerful linear actuator was desired. The linear actuator used

in the design, was bought from Actuator Zone, a company selling mechanical components

online [Available from: http://www.actuatorzone.com/actuator-linear-actuator-pa-02-24-400-24-inch-

stroke-400-lbs-force-actuator.aspx ]. Specifications of PA-02-24-400 actuator:

• Stroke: 0.6 m

• Weight: 2.72 Kg

• Speed: 0.015 m/s

• Force: 1780 N

• Voltage: 12Volts

• Price: 90 UKP

44


The linear actuator was the most expensive investment of the project. The price of linear

actuators are higher compared to prices for rotational actuators. However, despite its high

cost, the linear actuator was preferred in order to reduce support tubes which would have

been necessary without the linear actuator’s present and to provide accuracy.

The choice of the linear actuator was crucial in meeting the requirements of this system.

The linear actuator provides one with a very high value of stroke force (1780 N). One solar

panel (7.5 Kg) was installed to the system, thus the minimum stroke force required was

calculated using the equations below.

Figure 24

Since x=y

𝐹!"# + 𝐹! = 𝐹 Equation 15

so

𝐹!"# ∗ 0.27 = 𝐹! ∗ 0.27

Where F is the force applied by the solar panel: 7.5 ∗ 9.81 = 73.58𝑁, Fact is the stroke Force and Fs is the

force applied by the two rectangular beams.

Finally substituting the two equations, we obtain 2𝐹! = 𝐹 which allows us to calculate the

Fact which is 18.395N.

Thus, apart from satisfying requirements, it also gives us the potential to add more PVP to

the system with the help of an extension kit. Due to the fact that the sun moves very slowly

along the day, the small velocity (0.015m/s) the linear actuator has increase the overall

accuracy of the system. In addition, the mounting brackets at the two edges of the linear

45


actuator provide a simple assembly to the user. Concluding, a smaller in size (mainly in

height) and stroke force linear actuator could have been used. However, due to the

limitation in time and the fact that the company was out of stock in smaller linear

actuators, I had to choose the specific one. The difference in size for linear actuators does

not affect the price, as it is the same despite the size. A smaller in size linear actuator could

have only reduced the overall height of the system.

Figure 25-Linear actuator

Rotational Actuator

A rotational motor can operate as a prime mover for the shaft; thus rotating the whole

system. The motor must drive the solar panel in small angles between 0 and 180 degrees at

a low speed.

The DC motor used is of unknown properties due to the fact that it was removed from an

existing machine. A multi meter was connected parallel to the DC motor in order to

identify its voltage which is of 12 volts.

Bearings

By the time the first wheel was invented, people realised that motion can be achieved

easier on rollers. In addition, lubrication is another way to reduce the relative motion

between surfaces. These two features were combined together to form bearings. A bearing

is a mechanism, which is used in mechanical systems to support relative motion between

46


moving parts. Even though is not viable to everyday life, bearings are ubiquitous in our

everyday life; automobile, computers, electrical appliances, tools, etc.

Figure 26-Bearing acting loads [Available from: http://www.rbcbearings.com/ballbearings/selguide.htm]

The main benefits that bearings provide to a system are listed below:

• Power saving

• Lubrication and labour saving

• Reliability

• Cleanliness

• Reduced fire hazards

• Increased production

• Life span

A range of bearings, in sizes and dimensions, are available in the market functioning to the

desired application. The most common types of bearings available in market are listed in

the table below:

Type of Bearing Features Application

Deep groove ball • High speed and precision

• Average radial and thrust load

Automobiles, cutting tools,

water pumps, machinery.

Self-aligning ball • Support radial and thrust load where shaft and

housing are subjected to misalignment

Rubber mixers, vertical

pumps.

Thrust ball • Support thrust load Automobile, gauges and

47


instruments.

Needle roller • Support of radial load where radial dimension

is limited

Oil pumps, harvesters.

Cylindrical roller • Low speed and heavy load

• Support only radial load

Machine tools, tractor,

motors.

Spherical roller • Support radial and thrust load.

• For long shafts

Mill machinery, air

compressors, cranes.

Table 11-Types of bearings

This project involves both a thrust and a radial load acting on the shaft. Radial load is the

torque applied by the driver gear to the driven gear in order to rotate the system. The

weight of the top part of the system acts perpendicular to the shaft. Two bearings were

installed in the system in order to reduce friction reduction; thus less power required to

rotate the system and more reliable design. Table 12-Chosen bearings specifications

indicates the specifications of the two bearings used.

Type Internal diameter (mm) External diameter (mm)

Deep Groove Ball bearing 40 68

Thrust Ball bearing 30 48

Table 12-Chosen bearings specifications

A deep groove ball and a thrust bearing were placed accordingly. The deep grove ball

bearing was used to enable motion along the shaft and overcome the radial force. This type

of bearing operates with the need of high precision in the rotation of the shaft. In addition,

it can accept average thrust loads. The second bearing is a thrust ball bearing that

overcomes the vertical forces acting on the shaft. Thus a thrust ball bearing is installed

onto the shaft in order to co-operate with the deep groove bearing and produce a reliable

design. The assembly of the bearings with the shaft is displayed below using SolidWorks.

48


Figure 27-Bearing assembly

In addition, calculations were made in order to predict the life expectancy of the bearings.

These were based on a life expectancy of 60 million revolutions. Using the formula below,

the basic dynamic load rating (C kN) was calculated.

𝐿!" = 10! ∗ 𝑎! ∗ 𝑎! ∗ 𝑎! ∗ (!!)! Equation 16

Where the equivalent dynamic load = 𝑋𝐹𝑟 + 𝑌𝐹𝑎 , L10 is the basic rating life and p,a1,a2 and a3 are

provided by the manufacture booklet of the bearings.

Calculations were performed in excel and results are shown in the table below:

BEARING LIFE

Deep Groove Ball Bearing

L10- basic rating life 1.752 revolutions

C- basic dynamic load rating 0.0087316 KN

P - the equivalent dynamic load 0.0072430 KN

p 3

a1- Reliability life factor 1

a2- materials life factor 1

a3- debris life factor 1

49


Thrust Ball Bearing

L10- basic rating life 1.752 revolutions

C- basic dynamic load rating 0.205 KN

p 0.170 KN

p 3

a1- Reliability life factor 3

a2- materials life factor 1

a3- debris life factor 1

Table 13-Bearing life calculations

PVP (photovoltaic Panel)

Solar panels or PVP are identified based to their raw material: Thin amorphous, mono-

crystalline and poly-crystalline photovoltaic panels. Furthermore, the amount of power

capable to produce is another criterion for a PVP. A 100watts PVP made of mono-

crystalline solar cells was selected. It weight 7.5Kg with dimensions of 1200 × 500 × 30

mm. The PVP was bought online at the price of 90 UKP from the following link:

[Available from: www.ebay.co.uk]

The PVP’s dimensions were an initiating integrating factor for the top part of the design.

The width of the PVP, as mentioned above, determined the distance between the top edges

of the two rectangular tubes in order for the hinges to connect the PVP to the tubes and

allow it to tilt.

Figure 28-PVP 2D drawings

50


Electronic Design

In order to produce an effective solar tracker based on the principles of a dynamic solar

tracking system analysed in the literature review, an accurate control system is required to

reliably track the sun by exposing it to the point of peak light intensity for the longest

possible time. With the aid of electronics, a dynamic solar technique system will be

designed. The performance of the controlling system will be demonstrate with the aid of

real life testing. Results will prove that a solar panel using a solar tracker provides more

power compared to a fixed position solar system.

Micro-controller Board

A controller board is used to interface with peripherals and act depending on these. The

aim is to be able to read the LDR sensors (input signals) on top of the panel and make

some basic calculations (output instructions) to finally drive the motors accordingly to

make the panel face the sun; Thus a dynamic solar tracking system.

Figure 29- Arduino micro-controller [Available from: http://www.arduino.cc/]

To achieve this, an Arduino Duemilanove board is used due to its simplicity interfacing

with the hardware which is supported worldwide and has a big community which is always

there to help.

51


The USB connection used to program the Arduino board is also used to gather data from

the sensors and is able to log important data onto the computer through UART (Universal

Asynchronous Receiver/Transmitter) to later on graph it and obtain feasible results. The

microcontroller in the Arduino board will hold the algorithm which is written in C, a

coding language, [Appendix E].

Motor-driver Board

An Ardumoto Shield [Available from: https://www.sparkfun.com/products/9815] is

directly connected to the Arduino board in order to control the two actuators in the design.

The Ardumoto is based on an L298 H-bridge which will give power to the motors. Two

LEDs in the board indicate the direction of each actuator which is helpful for testing and

debugging purposes.

Figure 30-Ardumoto

LDR (Light Dependant Resistors)

LDRs are sensors that vary their resistance depending on the light intensity. Four of these are positioned in each corner of the panel to measure the light difference between. This light difference will tell the direction at which the motors should move. To achieve a good

52


performance, a voltage divider was built with each photo resistors as per the picture.

Figure 31-Resistance VS Light intensity graph [Available from: http://www.kitronik.co.uk/resources/understanding-electronics/how-a-ldr-light-dependent-resistor-works]

In order to achieve a good performance, a voltage divider was built with each photo

resistors as in Figure 32-Voltage divider . The voltage divider converts the resistance to a

voltage so that the Arduino can read the input from the LDRs. In addition LDRs are

calibrated in order that to for all four of them to give the same value in different light

conditions.

Figure 32-Voltage divider

Voltage

divider

53


Software

The Arduino is a micro-controller which allows a user friendly interfacing. A software was uploaded and calibrated in order to function the mechanical part of the system. The software [Appendix E] functions by recording the values of the sensors and basic mathematics are performed to identify the direction and magnitude of the signals sent to the actuators accordingly.

When the sum of right hand side sensors is deducted from the sum of the left hand side sensors [(1+2)-(2+3) =x-axis], the difference will determine the direction for the x-axis (rotary actuator) whereas the same procedure is performed to determine the y-axis (linear actuator) direction [(2+3)-(1+4) =y-axis] as shown in Figure 33.

This will then select which direction the motors should move. Later on the Arduino will send PWM signals to the Ardumoto to drive the motors in an accelerated and pulsed pattern.

The current sensed obtained from the ADCs (analogue to digital converters) will be sent to a host PC through serial and saved in text files. Excel would then be used to graph this data.

Figure 34-Dynamic tracking methodology

3 2

1 4

Figure 33- LDR’s alignment

Read sensors

Calculate light difference

Select motor direc5on

Move motors if needed

Stop motors

Send current sense values through serial

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Remarkable Outputs and Experimental

Results

Cost Analysis

A cost analysis procedure was performed where the retail price of the solar tracker was

calculated. One of the initiating objectives of the project was to manufacture a

significantly cheap solar tracker. Solar trackers available in the market of United

Kingdom, range from 600UKP to 2000UKP. Thus, our aim was to build a solar tracker,

whose price would allow the seller to add an extra 25% profit. The 25% profit was

calculated by comparing retail prices of products manufactured by Harwal Group of

Companies with the selling prices used by distributors of their products. The choice of

materials were chosen in such a way so that the retail price will range between £400- £600.

A detailed costing datasheet is provided below where shipping is excluded.

MATERIAL Price

PV PANEL £ 90.00

SUPPORT BEAM DIAGONAL (2) £ 3.00

SUPPORT BEAM HORIZONTAL £ 1.00

PVC DISC £ 5.00

PVC CYLINDRICAL TUBE £ 15.00

PVC SQUARE BASE £ 6.00

SHAFT £ 5.00

BEARINGS £ 7.00

ACCESSORIES £ 5.00

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FASTENERS £ 3.00

ARDUINO MICRO-CONTROLLER £ 15.00

ARDUMOTO £ 10.00

ELECTRONIC PERIPHERALS £ 5.00

LDR SENSORS £ 2.00

12 VOLT POWER SUPPLY £ 15.00

LINEAR ACTUATOR £ 90.00

ROTARY ACTUATOR £ 30.00

OTHER (INCLUDING PACKING COST) £ 12.50

TOTAL MATERIAL COST £ 319.50

LABOUR & OVERHEADS (15% LABOUR + 5% OVERHEAD) £ 63.90

TOTAL COST £ 383.40

GROSS PROFIT 15% (ROUNDED) £ 57.51

RETAIL PRICE £ 440.91

Table 14-Costing Datasheet

The solar tracker’s selling price with an additional 15% Gross profit for the manufacturer

was calculated to be £440.91, ranging between the set margins of £400-£600. This will

allow the distributor to add a 25% profit for himself. Thus a solar tracking system with a

100Watt PVP can be sold at the price of £551.14. The costing datasheet above was based

on a similar procedure used by “Harwal Group of Companies” to calculate their selling

prices. Comparing this price to the one of solar trackers available online, it is cheaper by

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approximately £50. Thus our 100W solar tracker prototype can be described as relatively

cheap.

As previously mentioned, the most expensive equipment bought for this project was the

linear actuator. The linear actuator was bought at a price of £90; thus, is the component

that significantly increased the selling price. Instead of using a linear actuator, a second

rotary actuator could have been used with modifications to reduce the cost. However the

retail cost will range about the same price calculated, £440,91, due to the fact that an

improved controller should be replace for more accurate and effective output results

Additionally, the same costing datasheet was used to calculate the cost without the solar

panel. The new raw material cost was calculated to be £229.50, the retail price £263.92

and the selling price £329.90.

In addition, the payback period for the solar tracker was calculated. Using figures provided

by Sunrise Sunset [Available from: http://www.projectbritain.com/weather/sunshine.htm] the average

hours of daylight was calculated. The cost of electricity in the UK is 15.32 Pences/Kw

according to energysavingtrust.org.uk. Thus using the following equation an estimated

payback time was calculated.

!"#$!"#$"%& !"#$

= 𝑓 ∗ 𝑃 ∗ ℎ𝑜𝑢𝑟𝑠 𝑜𝑓 𝑑𝑎𝑦𝑙𝑖𝑔ℎ𝑡!"# !"#$ ∗!"#$!%# !!"#$ !" !"#$%&!!

!"#∗ 𝑐𝑜𝑠𝑡 𝑜𝑓 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦

Equation 17

Where f is the efficiency and P is the power of the solar panel.

Since the cost of our solar energy system is £440.91, substituting in the formula above an

estimated payback time of 14.34 years

An excel spreadsheet simulator was used to calculate the payback time, and a scenario of a

solar tracker with a higher output power was performed in order to calculate the payback

time for it. It was assumed that 4 solar panels of 150Watts were operating installed in our

system. The total cost of the system will increase to £1,292.89 and the total power will

now change to 600W. Substituting our new criteria in the payback template, the payback

time is now 5.61 years.

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It is crucial to mentioned that the payback period is based on theoretical assumptions.

However the overall costing price ranges low compared to the solar tracking system’s

market.

Do-It-Yourself Product

A DIY (do-it-yourself) product was manufactured. One of the principles followed to

integrate the prototype is to provide an easy assembly to the buyer. This is a modern

business strategy used by one of the biggest and most profitable manufacturing company

in the word, IKEA. A self-assembly solar tracking energy system will not require the need

of a technician thus reducing the overall cost of the investment. In addition this feature

allows the user to maintenance the system in case of any malfunction by replacing only the

damaged part.

Figure 35-Exploded assembly

Assembling the mechanical and the electronica components of the solar tracker (for a

second time) took me approximately 18 and 13 minutes respectively total of 31 minutes.

For an everyday user who is not familiar with the design, a period of one hour would be

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sufficient in order to assembly a stiff and robust system with the help of a manual booklet.

This is one of the biggest advantage of the product.

Real time-Testing of the Universal Solar Tracker

Testing in real time was performed in order to demonstrate that the solar tracker was

operated based on the principles of a dynamic solar tracking system. Two scenarios were

tested: 1) the photovoltaic panel was at a fix position at an angle of 45 degrees facing south

–west and 2) a dual axis solar tracker- between 12:00 and 13:00 o clock mid-day in two

consecutive days. This two experimental scenarios allows us to display difference between

the overall performances of a solar tracking system and fix position solar system. The

figure below demonstrates the power output analysis for a solar tracking system compared

to a fixed mounting position performed by POWERWAY [Available from:

http://www.pvpowerway.com/news/829.html].

Figure 36- POWERWAY power chart for a period of a day

Method and Calibration of testing

In order to be able to calculate the power that the electronics are using at any given time, a

current sense resistor was used. To make calculations easy, a 1 ohm 50w power resistor

was connected in series at the output of the power supply at which the electronics were

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connected. Current will be then calculated depending on the voltage difference across it, as

follows: 𝑉 = 𝐼 ∗ 𝑅, Where V is the voltage, I is the current and R is the resistance.

As we know the resistance is 1ohm we can deduce that and we end up with a simple

formula we can use to convert the voltage measured: V=I*1 à V=I

Figure 37-Current Sense resistor

Finally a dummy load was used to be able to draw a constant amount of current from the

solar panel. Thus current can be measured easily with a similar approach as described

above. The dummy load is available

by:http://www.arachnidlabs.com/blog/2013/02/05/introducing-re-load/. The figure below

shows the basic circuit for building a constant current load provided by the manufacturer

in the left hand side and on the right hand side is the load connected to the Arduino micro-

controller. Finally the load needs to be calibrated so that it actually gives 1mV for every

amp.

Figure 38 Dummy Load and schematic diagram[Available

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Summarizing from the approach taken to test the • Connect the four resistors to “ADC0”, “ADC1”, “ADC2”, “ADC3”.

• Arduino is connected to pins 3, 11, 12 and 13 on the Ardumoto.

• The panels is connected with “resistor 1” next to it and the yellow resistor to ADC4.

• Connect the power supply with “resistor 2” and the 2 wires on the ardumoto (“ADC5)

Figure 39- Experimental Approach

Fix position solar system Scenario The solar panel mounting position was set in

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Figure 40-Fix position current Graph

Graph as expected, has an increasing linear pattern between 12:00 and 12:33 o clock,

where the sun was moving in a position closer to it’s the systems ideal position (direct

exposure). Coming next, a stable current between 12:33 and 12:45 was observed. The

stability in current received is due to the fact that sun, over this period of time, hits the

solar panel directly. In addition peak current of 4.2 Amps was achieved between 12:33 and

12:45, validating the statement that more power can be received by a solar energy system

when exposed to direct sunlight, as It appears to be at that period. Finally between 12:45

and 13:00 o clock, even though the graph is still in a constant pattern, a slight reduction in

current was observed. This is due to the fact that sun’s magnitude is moving, slowly, away

from the direct exposure angle.

Universal Solar Tracker Scenario

The second experimental test involved recordings of the current received by the solar panel

with the aid of the universal solar tracker, during the same period of time on a different

day.

The current sense resistor was now connected

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Figure 41-Universal Solar Tracker Current Graph

A constant curve was formed from the data

Power produced: Fix position Vs. Universal Solar Tracker

It is significant to calculate the total power produced by a solar energy system, an

important specification. Power=Current*Voltage in Watts, using this equation the power

produced for each system was calculated. Voltage was recorded in time intervals of 10

minutes with the aid of a multi meter due to the fact that the Arduino micro-controller

didn’t have any ADCs left on. Out of the recordings an average value of 18.7 Volts was

calculated and used in order to predict the likely power output in each scenario and be able

to compare them.

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Figure 42-Fix position Vs. Universal Solar Tracker

The graph above shows the predicted pattern

Once again, comparing a solar tracking system to a standalone solar energy system with

the aid of Figure 42-Fix position Vs. Universal Solar Tracker, effectiveness and overall

performance between the two of them proves the literature review and proposed methods

of tracking. The area under each curve denotes the net power production of each scenario.

The area covered by a solar is much higher compare to the fix position system. It is

important to be mentioned that the day on which the Universal solar tracker scenario was

tested was a cloudy day which directly affects the performance of a solar energy system. In

addition, the fix position solar panel maximum output is higher compared to the other

scenario. This statement should have been opposite and shows the lack in accuracy

provided by the controlling system.

Expanding the graph in Figure 42-Fix position Vs.

Future Modifications and Conclusion

Extension kit Scenario As already stated, the linear actuator used provides us with a stroke force of 1780N. This

high stroke force are capable of accepting an extension kit stand on which more solar

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

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13:00

Power (W

a*s)

Time

Fix Posi2on Vs Universal Solar tracker Universal Solar Tracker Fix Posi5on

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panels can be install on the system. As calculated above, the linear actuator used requires

only 18.395N in order to tilt the solar panels. Calculations were made in order to check the

feasibility of replacing our solar panel with four 150W panels. Assuming that the average

weight of a 150W solar panel is 12Kg and the stand used is 5Kg, then the total required

stroke force is calculated using the same procedure as in 𝐹𝑎𝑐𝑡+𝐹! = 𝐹

Equation 15 and is 129.98N. This modification directly

affects significant forces acting on our system thus it was crucial to calculate the new

Factor of safety for the shaft. By replacing once again our new criteria in the excel

spreadsheet [Appendix D], our new FOS is 525.29, which again is very high. The stand

kit, together with the four 150W panels, was designed in SolidWorks and they replaced the

solar panel, as shown in the picture below.

Figure 43- 600W solar tracker

In addition, an FEA analysis was performed under the 4 solar panel scenario, in order to

verify that the two isosceles rectangular beams would not fracture due to overloading.

Results of the FEA analysis are demonstrated in Error! Reference source not found.,

where maximum stresses appear to take place at the point of joint between the horizontal

and the diagonal beams.

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Figure 44-FEA analysis

Conclusion

After examining the information obtained by the real time testing of the prototype, it can

be said that the proposed way of a dynamic solar tracking system, is a practicable method

of maximizing the mean intensity of sunlight received by a solar energy system. The

limited knowledge I have on electronics and controlling system commands makes the solar

tracking system incomplete. As already mentioned, the micro-controller used is not

reliable. The principle of dynamic tracking of the sun was achieved however it lacked of

accuracy and effectiveness due to electronic limitations.

The concepts which integrated the mechanical part of the Universal Solar Tracker

appeared to be effective. A product which can be assembled by the user in only one hour, a

robust structure. Additionally the significantly low angular velocity that was achieved by

the gear box combined with the low linear velocity provided by the linear actuator increase

the accuracy of the system. Even though the system is over-designed, with the appropriate

reductions in dimensions such as tube length and shaft diameter would decrease the raw

material required; thus, an even cheaper product can be created.

The linear actuator, which was the most expensive component used for this project, was

worth the money spend on it because of its various benefits, as previously identified. Some

of these are its high stroke force, its accuracy, the fact that it is easy to install and finally its

ability to function straight away. Therefore, the linear actuator has directly affected the

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design as a whole, as well as the performance of the tracker. Moreover, despite its price, it

was appropriate to choose and use the actuator in order to tilt the solar panel.

Concluding, as proved while having in mind that this is the prototype of the Universal

Solar Tracker, the overall system with the following modifications can compete in the

market of solar trackers as an effective, low cost, DIY solar tracker:

• Reduce raw materials by decreasing the overall size.

• Installation of an effective controlling system.

• Design a stand kit in order for the system to accept more solar panels.

• Supply the system with a battery and an inverter

Reflective Statement

This project has provided me with a priceless experience, which will unquestionably be of

great benefit in my future career as an engineer, as well as assist me in the areas of

industry and business. Having to produce such a big piece of work for the first time taught

me various things, amongst which are time management, finding effective methods for

problem solving, and generally enriched me with great knowledge. By completing this

project, I also gained experience in overcoming unpredictable obstacles; such as using an

unfitting mechanical part in manufacturing a product, having to come up with a practical

solution and learn to reschedule task’s deadlines.

Having worked hard, mainly by consulting and experimenting on various principles and

strategies that have been used for years from a range of companies, designers and

engineers, my project, was successfully built and functioned to a satisfying point. This

project, namely ‘The Universal Solar Tracker’, was my first engineering design model,

which I built from scratch.

A better and more critical knowledge and understanding of the areas of solar energy and

solar tracking system was achieved by the aid of the literature review. The various

resources of current awareness, which I have read indicated that it is important for an

engineer to have knowledge of the market surrounding his research areas. This is mainly

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because nowadays, customers’ demands are high due to the evolution of technology. Thus,

it is important for an engineer to make an adequate research based on the current market,

otherwise, the manufacture of products that do not meet the ends of the consumers will end

up in being a failure in the market.

Having to design a model of the product enriched me with experience and confidence in

working with SolidWorks, an engineering design software. Additionally, using the

Arduino micro controller in order to design the electronics provided me with adequate

knowledge of the programme, which I had never used before. Finally, the manufacture of

the product itself gave me the opportunity to use old-fashioned and modern manufacturing

processes and understand their importance. In addition I strongly feel that this project is

actually an engineering design project. The mechanical parts of the system, on which

through my Mechanical Engineering degree I gained rich full skills and confidence on this

area, were approached, investigated and manufactured as an amateur engineering designer

would have done.

Having tested the Universal Solar Tracker verified the research outputs. The researches

made and the design proved to have been successful as more power was gained with the

use of a solar tracker, as compared to a fix position solar system: Dynamic solar tracker.

Despite that, I honestly don’t feel satisfy from the electronic area of the project, since I

have never before worked on electronics and at this stage I believe I should have read and

worked on it even harder. In my opinion, this is an area where the prototype lacks in

competence. A short and unprofessional video was recorded while testing the system and

is available from: http://www.youtube.com/watch?v=KtwnweP7T-A . Additionally, the

prototype of Universal Solar Tracker is located in room 1N25 at the University of the West

of England, which it would be appreciated and respected if you investigate it and provide

me with feedback.

In conclusion, despite the exhaustion and stress that I have felt over the past six months, I

have now realised that this project assisted me in improving my confidence and making

me a more responsible person. Most importantly, my knowledge in this area has reached

an advanced level.

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Appendices

See the CD submitted for the appendices

Appendix A- Gantt chart

Appendix B- Design Selection

Appendix C- SolidWorks 2D/3D Drawings and Simulations

Appendix D- Solar tracking system calculations [Excel template]

Appendix E- Arduino Code

Appendix F- Experimental results [Excel template]

Appendix G- Cost Analysis

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Universal solar tracker final report

Engineering

Transcript of Universal solar tracker final report