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UNIVERSITY OF NAIROBI

SCHOOL OF ENGINEERING

DEPARTMENT OF ELECTRICAL ANDINFORMATION ENGINEERING

SOLAR TRACKER FOR SOLAR PANELPROJECT INDEX: PRJ 141

BYKENEI DAVID KIBET

F17/1434/2011

SUPERVISOR: Mr. S.A. AhmedEXAMINER: Dr. G Kamucha

Project report submitted in partial fulfillment of the requirement for theaward for the degree of Bachelor of Science in Electrical and ElectronicsEngineering of the University of Nairobi 2016

Submitted on: 13th May 2016

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DECLARATION OF ORIGINALITY

FACULTY/ SCHOOL/ INSTITUTE: EngineeringDEPARTMENT: Electrical and Information EngineeringCOURSE NAME: Bachelor of Science in Electrical & Electronics EngineeringNAME OF STUDENT: Kenei David KibetREGISTRATION NUMBER: F17/1434/2011COLLEGE: Architecture & EngineeringTITLE OF WORK: SOLAR TRACKER FOR SOLAR PANEL

1) I understand what plagiarism is and I am aware of the university policy in this regard.2) I declare that this final year project report is my original work and has not been submittedelsewhere for examination, award of a degree or publication. Where other people’s work or myown work has been used, this has properly been acknowledged and referenced in accordancewith the University of Nairobi’s requirements.3) I have not sought or used the services of any professional agencies to produce this work.4) I have not allowed, and shall not allow anyone to copy my work with the intention of passingit off as his/her own work.5) I understand that any false claim in respect of this work shall result in disciplinary action, inaccordance with University anti-plagiarism policy.

Signature: ……………………… Date: ………………………

Approved by:

Supervisor: Mr. S. A. Ahmed

Signature: ……………………… Date…………………………

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DEDICATION

To my family especially my dad, Mr. Zakayo Cherono and mum, Mrs. Maria Cherono for

their relentless support in my University education.

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ACKNOWLEDGEMENT

I would like to express my heartfelt gratitude to Mr. S.A. Ahmed, who was my supervisor,

for his constant guidance in the implementation of this project. I especially thank him for

going out of his way to provide unrelenting advice and resources including the MSP430

Launchpad and solar panel together with meters, all of which were essential to the success of

this project.

I would like to express great gratitude to all the lecturers in the Electrical Engineering

department, University of Nairobi for equipping me with all the knowledge and skills that

provided enough competence to complete the project.

I would also like to acknowledge my examiner, Dr. G Kamucha for taking his time to

examine this project.

Thirdly, I would like to thank members of staff in the Electrical department including Mr.

Kinyua Wachira for his guidance and help in micro-controller programming, Mr. Rotich for

providing support in acquisition of components and Mr. Wangai of mechanical workshop for

his assistance in making of the PCB

Finally, I would like to thank my classmates & colleagues especially Caroline Jelagat,

Samuel Chege, Festus Okwado, Benson Mutuku and Tonny Silvance for their much valued

advice and great contribution towards the success of the project.

Above all, I would like to thank the almighty God for enabling me achieve this success and

showing me light at the end of the tunnel.

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Table of Contents

Abstract ........................................................................................................................................... 1

Chapter 1: Introduction ................................................................................................................... 2

1.1 General Background......................................................................................................... 2

1.2 Problem Statement ........................................................................................................... 2

1.3 Project Justification .......................................................................................................... 3

1.4 Objectives......................................................................................................................... 3

1.5 Scope of the Project.......................................................................................................... 3

1.6 Methodology .................................................................................................................... 4

1.7 Project report organization ............................................................................................... 4

Chapter 2: Literature Review.......................................................................................................... 5

2.1 The Orbit and Rotation of the Earth................................................................................. 5

2.2 Why Solar Tracking is necessary ..................................................................................... 7

2.3 Tracking the Sun .............................................................................................................. 8

2.4 Types of Solar Tracking Mechanisms............................................................................ 10

2.5 Light Sensor Theory....................................................................................................... 12

2.6 Servo- Motor Theory...................................................................................................... 15

2.7 Micro-controller Theory................................................................................................. 18

Chapter 3: Design and Implementation ........................................................................................ 24

3.1 Flowchart for the Motor Control .................................................................................... 24

3.2 Algorithm for the motor control..................................................................................... 25

3.3 Hardware Block Diagram............................................................................................... 25

3.4 Light Sensor Design ....................................................................................................... 26

3.5 The Choice of Microcontroller....................................................................................... 27

3.6 Hardware Schematic Diagram ....................................................................................... 28

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3.7 PCB Schematic of the circuit design.............................................................................. 29

Chapter 4: Results and Analysis ................................................................................................... 30

4.1 RESULTS....................................................................................................................... 30

4.2 ANALYSIS .................................................................................................................... 34

Chapter 5: Discussion, Conclusion and Recommendations ......................................................... 37

5.1 Discussion ...................................................................................................................... 37

5.2 Conclusion...................................................................................................................... 38

5.3 Recommendations .......................................................................................................... 38

References..................................................................................................................................... 40

APPENDIX................................................................................................................................... 42

Project Gantt Chart ................................................................................................................... 42

The code used in the micro-controller ...................................................................................... 42

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List of FiguresFigure 1: The orbit of the earth and declination at different times of the year ............................... 6

Figure 2: Sun angles showing altitude, azimuth and hour angle .................................................... 9

Figure 3: Tilt angle of the PV array .............................................................................................. 10

Figure 4: types of solar tracking platforms ................................................................................... 11

Figure 5: A typical Light Dependent Resistor-LDR Circuit symbol .......................................... 13

Figure 7: Typical resistance vs. light intensity characteristic of a LDR ....................................... 13

Figure 8 : utilizing the photo-cell to get a voltage input............................................................... 14

Figure 9: Components of the servo-motor unit............................................................................. 15

Figure 10: Pulse Width modulation .............................................................................................. 17

Figure 11: Pulse width and corresponding angle of rotation of the servo .................................... 18

Figure 12: General block diagram of a Micro-controller.............................................................. 19

Figure 13: illustration of the Harvard architecture ....................................................................... 21

Figure 14: Von-Neumann architecture ......................................................................................... 22

Figure 15: Light Sensor Design .................................................................................................... 26

Figure 16: Msp430G2553 pinout.................................................................................................. 27

Figure 17: Hardware Schematic.................................................................................................... 28

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LIST OF TABLES

Table 1: Results for Morning and Afternoon of 14th May 2016.................................................. 30

Table 2: Results for 11th May 2016 ............................................................................................ 33

Table 3: Values of Efficiency of the tracked and fixed panels ..................................................... 35

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ABREVIATIONS AND ACRONYMSADC Analog-to-Digital converter

DAC Digital-to-Analog converter

DC Direct-current

AC Alternating Current

LDR Light Dependent Resistor

PWM Pulse Width Modulation

LED Light Emitting Diode

MCU Micro-controller Unit

LUX Luminous Flux

PV Photovoltaic

UV Ultra-violet

Vcc DC supply voltage

PCB Printed circuit Board

R Resistor

MIN Minimum

MAX Maximum

EEPROM Electrically Eraseable Programmable Read Only Memory

USB Universal Serial Bus

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AbstractAlthough solar energy is the main energy source in the solar system, its potential as an energy source

has not been fully realized because of low efficiency of solar Photovoltaic cells. The main objective of

this project is to increase the efficiency of solar Panels by using a micro-controller based solar tracking

mechanism.

The project involved design and implementation of an automatic microcontroller based solar

tracker system expected to be used with photovoltaic solar panels. The proposed single-axis

solar tracker device functions to ensure the solar panel is optimally directed in accordance

with the real position of the sun and therefore increasing the efficiency of solar panels.

The operation of experimental model of the device was based on a servo motor which is

intelligently controlled by the pulse width modulated signals received from a microcontroller

unit (MCU). The microcontroller receives input from light sensors which measure the

intensity of the sun, and enables the motor to move the panel to a position at which it

receives optimal power.

The performance and characteristics of the solar tracker device are experimentally analyzed

in order to determine the efficiency of the fixed panel and the panel attached to the solar

tracker, hence, enabling the determination of efficiency improvement when using the single-

axis solar tracker.

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Chapter 1: Introduction

1.1 General Background

Solar power is considered as a very viable potential renewable energy source because the

largest energy source available is the sun, which supplies practically limitless energy. The

energy available from the sun far exceeds any foreseeable future demand.

The sun provides energy to sustain life in our solar system. According to [2], in one hour, the

earth receives enough from the sun to meet its energy needs for a year, this is 5000 times the

input to the earth’s energy budget from all other sources.

Despite the immense energy output if the sun, harvesting solar energy has proved to be a

great challenge because of the limited efficiency of solar cells. The efficiency of solar cells

has been estimated to be between 10-20 percent. This project is based on the concept of

improving this efficiency by means of a solar tracking mechanism.

The main purpose of a solar tracking system is to track the position of the sun in order to

expose a solar panel to maximum radiation at any given time of the day, as mentioned. This

is because the position of the sun with respect to the earth changes in a cyclic manner in the

course of the year.

Solar tracking is seen to improve the efficiency of solar energy production. It has been

shown that use of solar tracking improves the efficiency of solar energy production by up to

30-40%.

There are various types of trackers that can be used for increase in the amount of energy that

can be obtained by solar panels. Dual axis trackers are among the most efficient, though this

comes with increased complexity. Dual trackers are the best option for places where the

position of the sun keeps changing during the year at different seasons. Single axis trackers

are a better option for places around the equator where there is no significant change in the

apparent position of the sun.

1.2 Problem Statement

The problem that is posed is the implementation of a solar tracking system that is capable of

enhancing the efficiency of solar power collection by photovoltaic cells by up to 30-40%.

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The circuit used a Micro-controller unit to control a motor which positions the solar panel

optimally.

1.3 Project Justification

The main aim of this project is to implement a solar tracking system that ensures the sun rays fall

perpendicularly on the solar PV panel and thus harness the maximum amount of solar energy

possible. In doing so, increases the efficiency of solar cells.

The project seeks to solve the problem of accurate, efficient and economical micro-controller

based solar tracking system that can be implemented within the available time and using

available resources so as to track the motion of the sun.

Motor control using pulse width modulated (PWM) signals is generated by the MSP430G2553

micro-controller is effected to move the solar panel, directing it towards the sun.

1.4 Objectives

The project was aimed at achieving the following objectives

1. To design and implement a micro-controller based solar ultra-violet light tracking

system that can direct a solar panel towards the sun

2. To show that the use of solar tracking increases the efficiency of solar panels

considerably

1.5 Scope of the Project

The design of the project was limited to single axis tracking because of two reasons, firstly, there

was the issue of cost and mechanical structure complexity. Secondly, there was the issue that

since the tracker was to be used in Kenya, which is situated within the tropics, then the sun’s

position does not vary significantly during the various seasons, in Polar Regions (North and

south), then dual axis tracking becomes a necessity because of the changing position of the sun

during various seasons.

The project also used servo motors because of the various advantages it poses, such as, low cost,

smooth rotation at low speeds, usage of no power at stand-still, and high peak torque.

Also, embedded software was programmed into the MSP430 Micro-controller IC. The

programming language used was C++ which is an object oriented language.

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1.6 Methodology

The solar tracking system can be sub-divided into three parts. Firstly, there is the input stage

which comprised of light sensors (Light Dependent Resistors) and resistors. The two are

designed in such a way that they form a voltage divider, the voltage from the divider then is

proportional to the light intensity falling on the light sensor.

Secondly, there is the micro-controller (MSP430 IC) that takes the two analog voltages from the

sensors as input, compares them and sends out an actuating signal to move the motor

appropriately.

Thirdly, there is the servo-motor which adjusts its position appropriately, so as to direct the panel

towards the sun.

Finally, a wooden mounting is designed and constructed to hold the panel and components of the

solar tracker.

1.7 Project report organization

The project report is divided into 5 chapters;

Chapter 1: This is the introduction to the project that describes the general background and

justification for doing the project. The problem statement, objectives, methodology and scope of

the project are also described.

Chapter 2: This has the literature review that shows the material that was used during research

and shows background information relevant to the scope of the project.

Chapter 3: The chapter involves the design and implementation of the project.

Chapter 4: It involves results and analysis.

Chapter 5: This chapter has the discussion, conclusion and recommendations to improve future

versions of the project.

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Chapter 2: Literature ReviewAs mentioned in [1] , solar power is considered as a very viable potential renewable energy

source because the largest energy source available is the sun, which supplies practically

limitless energy. The energy available from the sun far exceeds any foreseeable future

demand.

The sun provides energy to sustain life in our solar system. Possible solar-energy systems

may include home heating or power production systems, orbiting-space systems and steam-

driven electrical power systems. The position of the sun in the sky is varied both with

seasons and time of day as the sun moves across the sky.

2.1 The Orbit and Rotation of the Earth

The earth revolves around the sun once per year in an elliptical orbit with the sun at one foci.

As mentioned in [2], such distance from the sun is given by= 1.5 × 10 1 + 0.017 360( − 93)365Where n represents the day of the year, with January 1st as day 1.

The earth also rotates on its own polar axis per day.

The polar axis of the earth is inclined at 23.45 degrees to the plane of the earth’s orbit around

the sun. This inclination causes the sun to be higher in the sky in the summer than in the

winter. It is also the cause of longer summer sunlight hours and shorter winter sunlight hours.

The figure below shows the orbit of the earth around the sun, and declination at different

times of the year.

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Figure 1: The orbit of the earth and declination at different times of the year, from [3]

It is worth to note that, on the first day of northern Hemisphere summer, the sun appears

vertically above the tropic of Cancer, which is latitude 23.45 degrees north of the Equator.

Also, on the first day of spring and fall, the sun is directly above the equator. Finally, on the

first day of winter, the sun appears vertically above the tropic of Capricorn, whose latitude is

23.45 degrees south of the Equator. This is as mentioned in [2]

Hence, from the above information, we can deduce that on the first day of spring and the first

day of fall, the sun is directly above the Equator. From fall to spring, the sun is south of the

equator while from spring to fall, the sun is north of the Equator.

The angle of deviation of the sun from directly above the equator is called the angle of

declination, δ.

If angles north of the equator are considered positive and angles south of the equator are

considered negative, then at any day of the year, the angle of declination can be found fromδ = 23.45 Sin 360( − 80)365

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It is also important to be able to determine the time at which solar noon occurs. Solar noon

occurs at 12 Noon time at only one longitude, L1, within any time zone.

At longitude east of L1, solar noon will occur before 12 noon, while at longitudes west of L1,

solar noon occurs after 12 noon.

2.2 Why Solar Tracking is necessary

All solar panels are rated by the DC power they produce in standard test conditions. A typical

solar panel produces about 200 Watts of electricity based on the efficiency and size of what

is installed.

The factors affecting the amount of power produced by solar panel systems are

1. Sun intensity- The power produced is directly proportional to the sun intensity

2. Solar cell efficiency- higher efficiency means higher power output

3. Solar panel size

4. The amount of sunlight directly hitting the panel

The main purpose of a solar tracking PV system is to track the position of the sun in order to

expose a solar panel to maximum radiation at any given time of the day, as mentioned in [4].

This is because the position of the sun with respect to the earth changes with respect to the

earth in a cyclic manner in the course of the year.

Solar tracking is seen to improve the efficiency of solar energy production. It has been

shown that use of solar tracking improves the efficiency of solar energy production by up to

30-40%, this is according to [5].

As mentioned in [2], approximately 50% more energy can be collected in the summer in a

dry climate such as that found in Phoenix, Arizona, by using a tracking collector. During

winter months, however, only about 20% more energy is collected using a tracker. In Seattle,

Washington, which receives somewhat more diffuse sunlight than Phoenix, a tracking

collector will collect about 35% more in the summer but only 9% more energy compared to

an optimized fixed collector in the winter. These studies show that the efficiency

improvement of tracking the sun depends on the season and the climate of the region.

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Despite the major benefits involved in using solar tracking systems, there are a few

limitations, which include

1. The cost of solar tracking systems including maintenance costs tend to discourage the

average consumer or small- scale power producers. In large scale applications, regular

maintenance and is necessary for performance to stay consistent, and this is economically

feasible. However, in small-scale applications this raises the question if solar trackers are

worth the extra costs and maintenance.

2. The increased complexity of the solar PV system inevitably introduces additional

possibilities for malfunction and failure. For most small-scale producers, simplicity will

yield the highest long term savings.

3. Solar trackers available are generally not programmable for location flexibility. This is an

important factor to consider when, for example, moving a system from the Northern to

the southern hemisphere, coupled with latitude and longitude position changes can result

in considerable changes in the tracker’s control circuitry.

When solar trackers are designed to be less costly, then the benefits outweigh the limitations

and having a solar-tracker system proves to be very beneficial. This is so, especially in

regions within the tropics, where single axis trackers, with simple circuitry can be

implemented effectively.

Photovoltaic (PV) or solar cells that are installed on the roof to convert photons (energy

packets) from the sun to direct current (DC) electricity that flows through an inverter where

the DC power is transformed into an alternating current (AC) power.

Hence, any shading on a Photo-voltaic cell will reduce the energy output considerably.

According to [2], even a small amount of shade on a PV module can significantly reduce the

module output current. It is thus of paramount importance to select a site for a PV system

where the PV array will remain unshaded for as much of the day as possible.

Solar trackers help to minimize the angle of incidence (the angle a ray of light makes with a

line perpendicular to the surface) between the incoming light and panel, increasing the

amount of energy that the installation produces.

2.3 Tracking the Sun

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As mentioned in [2], in order to completely specify the position of the sun, it is necessary to

specify three co-ordinates. If one assumes that the distance from the sun to the earth as

constant, then the position of the sun can be specified using two angles

1. The solar altitude, α- which refers to the angle between the horizon and the incident solar

beam in a plane determined by the zenith and the sun.

2. The Azimuth angle, ψ- This describes the angular deviation of the sun directly south.

This measures the sun’s angular position east or west of south. The Azimuth angle is zero

at solar noon and increases towards the east.

Another useful, though redundant, angle in describing the position of the sun is the angular

displacement of the sun from solar noon in the plane of apparent travel of the sun. The hour

angle is the difference between noon and the desired time of day in terms of a 360 degree

rotation in 24 hours.

These three angles are shown in the figure below,

Figure 2: Sun angles showing altitude, azimuth and hour angle, from [2]

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According to [6], a typical solar tracking photo-voltaic system generally must be equipped

with the following two essential features

Azimuth tracking- for adjusting the tilt angle of the surface of the PV array during the

changing seasons.

Daily solar tracking for maximum solar radiation incident to the PV array.

Figure 3: Tilt angle of the PV array, from [5]

Solar tracking is best achieved when the tilt angle of the tracking system is synchronized

with the seasonal changes of the geographical insolation level for optimized solar tracking

during the day.

Solar tracking allows more energy to be produced because the solar array is able to remain

aligned with the sun.

2.4 Types of Solar Tracking Mechanisms

According to [5], solar tracking systems may be classified into two

1. Active solar tracking

2. Chronological solar tracking

Active solar tracking involves monitoring the sun’s position constantly and continuously

throughout the year

Chronological solar tracking is a timer based tracking system that involves adjusting the solar

PV panel in a pre-defined sequence whether the sun shines or not. The purpose of a

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chronological tracker is to counteract the rotation of the earth by turning at the same speed as

the earth relative to the sun around an axis that is parallel to the earth’s axis.

In order to achieve this, a simple rotation mechanism is devised which enables the system to

rotate throughout the day in a predefined manner without considering whether the sun is

there or not

Figure 4: types of solar tracking platforms, from [6]

Figure 3 above illustrates the types of solar tracking platforms designs under consideration,

this is according to [7]

In a single axis tracker design, the tracking system drives the collector about a fixed axis of

rotation until the sun central ray and the aperture normal coplanar

This method is usually effective in tropical areas (preferably areas along the equator). This

is because, within the tropics, there are no significant changes in the apparent position of the

sun during the various seasons.

As mentioned in [5], single axis tracking entails monitoring the angle of altitude (angle of

tilt) of the sun along a single axis.

According to [7], there are typically three types of single axis sun tracking designs. These

include:

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1. Horizontal axis tracker – the tracking axis I set to remain parallel to the surface of the

earth, oriented along the East-West or North-South direction.

2. Tilted axis tracker- the tracking axis is tilted from the horizon by an angle oriented along

the North-South direction. For example, latitude – tilted axis sun tracker.

3. Vertical axis tracker- in this type of tracking , the tracking axis is collinear with the

Zenith axis, also known as Azimuth sun tracker

Also from [7], two-axis or dual-axis sun trackers follow the sun in both the horizontal and the

vertical plane. Examples include, the Azimuth-elevation and the tilt- roll sun tracking

systems.

In the azimuth elevation sun tracking system, the solar collector must be free to rotate about

the azimuth and deviation axes. In these systems, the tracking angle about the azimuth axis is

referred to as the solar azimuth angle while the tracking about the elevation axis is referred to

as the solar elevation angle.

Such dual-axis tracker systems track the sun on two axes such that the sun vector is normal to

the aperture in order to attain close to 100% energy collection efficiency. This is according to

[8].

The main components of the micro-controller based solar-tracking system are

1. Photo sensors (light-sensing) elements

2. motors

3. Micro-controller

2.5 Light Sensor Theory

As defined in [9], light sensors are devices that can be used to detect the ambient light level.

Light sensors are devices which exhibit electrical characteristics that change according to the

intensity of light in the surrounding.

A light dependent resistor is a component that has a resistance that changes depending on the

light intensity falling upon it. The diagram below shows a typical LDR and the

corresponding circuit symbol.

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Figure 5: A typical Light Dependent Resistor (LDR), from [9] Figure 6: LDR Circuit symbol

The common type of LDR has an electrical resistance that decreases with an increase in the

light intensity falling upon the device. The graph below shows the typical resistance vs. light

intensity characteristic of the Light dependent resistor.

Figure 7: Typical resistance vs. light intensity characteristic of a LDR, from [9]

According to [5], light sensors are among the most common sensor type. The simplest optical

sensor is a photo-resistor which may be a cadmium sulfide (CdS) type or a gallium arsenide

(GaAs) type [2]. The next step up in complexity is the photodiode followed by the

phototransistor

The solar tracker uses a cadmium sulfide (CdS) photocell for light sensing. This is the least

expensive and least complex type of light sensor according to [2].

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The Light sensor is a passive component which possesses the characteristic that resistance is

inversely proportional to the amount of light intensity directed toward it.

To utilize the LDR, it is placed in series with a resistor as shown in the figure below

Figure 8 : utilizing the photo-cell to get a voltage input, from [5]

From figure 3 above, it is clear that a voltage divider is formed and the output at the junction

is determined by the two resistances.

If it is desired for the output voltage to increase as the light intensity increases, the photocell

was placed in the top position while if it is desired that the output voltage is desired to

decrease as the light intensity increases, then the photocell is placed in the lower position.

This is because the value of the output voltage is given by= 11 + 2 × 5Where Vo is the output voltage.

From the above equation, it is clear that if R1 is the resistance of the photocell, which

decreases as the light intensity decreases, then the output voltage will decrease as the light

intensity increases. On the other hand, if R2 is the resistance of the photocell then as light

intensity increases, this resistance reduces causing the output voltage to increase.

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2.6 Servo- Motor Theory

According to [10], Servomotors are motors that use feedback for closed-loop control of

systems in which work is the variable. Servos are small mechanical devices whose sole

purpose is to rotate a tiny shaft extending from the top of the servo housing.

Servo motors find their application in radio controlled (R/C) airplanes, cars, and boats.

Servo-motors are increasingly becoming popular in the field of robotics.

The servo circuitry is built inside the motor unit and comes with a shaft that is fitted with a

gear. The motor is controlled with an electric signal that determines the amount of shaft

movement.

The servo contains three main components;

Small DC motor

Potentiometer

Control circuit.

Gears are used to attach the motor to the control wheel.

Figure 9: Components of the servo-motor unit, from [11]

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As mentioned in [11], the servo-motor has various advantages which make it suitable for

various applications

1. If a heavy load is placed on the motor, the driver will increase the current to the motor

coil as it attempts to rotate the motor. Basically, there is no out-of-step condition.

(However, too heavy a load may cause an error.)

2. High-speed operation is possible.

3. They are usually smaller in size

4. They tend to be very efficient

However, also according to [12], the servo-motor has various limitations

1. Since the servomotor tries to rotate according to the command pulses, but lags behind, it

is not suitable for precision control of rotation.

2. They tend to be costly.

3. When stopped, the motor’s rotor continues to move back and forth one pulse, so that it is

not suitable if you need to prevent vibration

According to [12] , servo-motors are controlled by sending pulses of variable width to them

through the control wire. There are three parameters of these pulses

1. Minimum Pulse

2. Maximum pulse

3. Repetition Rate

Given the rotational constraints of the servo, the neutral can be defined as the position

whereby the servo is as equally likely to rotate in the clockwise direction as it is to rotate in

the anti-clockwise direction. It is worth to note that although different servos will have

different constraints on their rotation, they will always have a neutral position, and that

position is always around 1.5 milliseconds.

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The angle is determined by the duration of the pulse applied to the control wire. This is

known as Pulse width modulation. The length of the pulse determines how far the motor

runs, for example, a 1.5 ms pulse will make the motor turn to the 90 degree (neutral)

position.

Figure 10: Pulse Width modulation, from [12]

As mentioned in [11], when these servos are commanded to move, they will move to the

position and hold that position. If an external force pushes against the servo while the servo

is holding a position, the servo will resist from moving out of that position.

The servo motor is commanded to rotate either clockwise or anti-clockwise by applying

pulses of width greater than or less than that corresponding to the neutral position. According

to [12], when a pulse of width less than 1.5ms is sent to a servo, the servo rotates to a

position and holds its output shaft some degrees anti-clockwise from the neutral position.

On the other hand, when a pulse wider than 1.5ms is applied to the servo, the opposite

occurs. The servo rotates some degrees clockwise from the neutral position and holds its

output shaft.

The minimum and maximum width of a pulse that will command the servo are functions of

each servo depending on the brand. That is, each brand will have a different maximum and

minimum. However, generally, the minimum pulse is seen to be around 1ms wide and the

maximum pulse is 2ms wide corresponding to 0degrees and 180 degrees angle of rotation as

shown in the figure below

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Figure 11: Pulse width and corresponding angle of rotation of the servo, from [12]

The turn rate is another parameter unique to each servo. As defined in [12], the turn rate is

the time it takes each servo to change from one position to another. The worst case turning

time is the time it takes the servo to move from the minimum rotation position to the

maximum rotation position when commanded.

The maximum amount of force that the servo motor can exert is known as the torque rating

of the servo. Servos do not hold the position for an infinite amount of time, the position pulse

must be repeated to instruct the servo to stay in the position.

2.7 Micro-controller Theory

According to [13], micro-controllers are LSI/VLSI systems which are a complete micro-

computer on a single chip. Micro-controllers are designed to control an application.

A micro-controller is a highly integrated chip, including on a single chip, all or most of the

parts needed for a controller. A controller is a device used to control some process.

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Also as mentioned in [14], the Micro-controller typically includes the following components

Central Processing Unit (CPU)

Random Access Memory(RAM)

EPROM/ PROM/ ROM- Read only memory (Erasable/Programmable)

I/O(Input/Output)-Serial and parallel

Timers

Interrupt controller

Analog to Digital Converters (ADC) and Digital to Analog converters (DAC)

Oscillator Circuit

All of the above components are included in a single chip as shown in the block diagram

below

Figure 12: General block diagram of a Micro-controller, from [14]

A Central Processing Unit (CPU) built in a single chip is called a micro-processor. The CPU

is the brain of the computer system. It administers all of the activity of the system and

performs all the operations on the data. The CPU continuously performs two activities, which

are fetching and executing instructions.

As mentioned in [15], the Central processing unti contains the following key components

The Arithmetic Logic Unit (ALU) which performs computation

20

Registers needed for the basic operation of the CPU, such as Program Counter (PC),

stack pointer (SP) and status Register (SR).

Further registers to hold temporary results

Instruction decoder and other logic to control the CPU and to handle resets and

interrupts and so on

According to [13], the CPU understands and executes instructions based on a set of binary

codes called the instruction set.

Aside from the CPU, the other key components of the micro-controller have their functions

briefly described below

Memory for the program: This is non-volatile type of memory also known as read-only

memory (ROM), meaning that it retains its contents even when the power is unavailable (it is

not powered).

Memory for data: This is volatile type of memory also known as random-access memory

(RAM). It holds the temporary data for the program

Input and output ports: These provide communication with the outside world

Clock: These serve to keep the whole system synchronized. It may be generated internally or

obtained from an external source.

Timers: most microcontrollers incorporate at least one timers. This is because timers serve

the following functions

1. Recording the time at which transitions occur in an input

2. Enabling driving on and off outputs at a specified frequency. This is used in

pulse width modulation , for instance, to control the speed of a motor

3. Enable the scheduling of tasks in a program.

Watch-dog timer: This is a safety feature that resets the processor if the program becomes

stuck in an infinite loop.

Communication interfaces: These are important as they serve as a way to exchange

information with another IC or system. They include serial peripheral interface (SPI). Inter-

integrated circuit (IIC), asynchronous (such as RS232), universal serial bus (USB),

Controller area network (CAN), Ethernet, etc.

21

Non-volatile memory for data: this is used to store data whose value must be retained even

when power is removed. Such data include serial numbers for identification and network

addresses.

Flash Memory: This can be both programmed and erased electrically and is now the most

common type of memory used in microcontrollers. It has largely superseded the electrically

erasable programmable ROM (EEPROM). Most MSP430 devices use flash memory.

According to [15], the two types of memories just reviewed, volatile and non-volatile, can be

treated as either having

Harvard architecture

Von-Neumann architecture

Harvard Architecture

In this architecture. The volatile (data) and non-volatile (program) memories are treated as

separate systems each with its own address and data bus. This is as illustrated in the figure

below

Figure 13: illustration of the Harvard architecture, from [15]

As mentioned in [14], many microcontrollers use this architecture including Microchip PICs,

Intel 8051 and descendants, ARM9

The Harvard architecture has the following advantages

1. It allows simultaneous access to program and data memories. Hence the CPU can

access the program memory and the data memory at the same time.

2. The two systems can be separately optimized

However, the architecture has the limitation that constant data (often lookup tables) must be

stored in the program memory because it is non-volatile, hence, constant cannot be read the

same way as volatile values from the data memory.

22

Von- Neumann Architecture

In this architecture, there is only one single memory and hence one set of addresses covers

both the volatile and non-volatile memories.

This is as illustrated in the figure below

Figure 14: Von-Neumann architecture, from [15]

Microcontrollers with a Von-Neumann architecture include the MSP430, the Freescale

HC508 and the ARM7

The architecture offers various advantages:

The system is simpler

There is no difference between access to a constant and variable data

However, the architecture suffers from the limitation that it is intrinsically less efficient

because several memory cycles may be needed to extract a full instruction from memory.

Micro controllers provide great benefits in automation of processes because of the following

reasons

1. Since all of the functional blocks of the micro-controller are contained within a single

Integrated Circuit (IC), this results in a reduced size of the control board.

2. Micro-controllers tend to have low power consumption

23

3. They tend to provide more flexibility and ease of integration within an application

design

4. The micro-controller not only reduces the cost of automation, but also provides the

designer with more flexibility

5. The designer is relieved from the complex interfacing of external peripherals like

ADC/DAC etc. and can concentrate on applications and development aspects.

24

Chapter 3: Design and Implementation

3.1 Flowchart for the Motor Control

START

Initialize the System

Read LDR

values

Convert data from

analog to digital

(S1-S2)>e

Compute the differencebetween the two values

(S2-S1)>e

STOP

Generate drive signalfor the motor

Y

NO

YE

NO

25

3.2 Algorithm for the motor control

The readings of the two Light Dependent Resistors (LDRs) are taken as input by the micro-

controller.

The inputs are analog, they are converted to digital value in the range between 0-1023. The

larger of the two values corresponds to the direction with more light intensity.

The two digital values are compared and the difference between them is obtained. This

difference is the error that is proportional to the angle of the rotation of the servo motor.

The servo motor rotates until the difference becomes zero. That is, the two LDR voltages are

the same. The PV panel is now facing the direction with the greatest light intensity.

3.3 Hardware Block Diagram

DC Power

SupplyMicrocontroller

Photo Sensors

Servo Motor

26

3.4 Light Sensor Design

The input stage of the solar tracker was designed keeping in mind that the MSP430G2553

microcontroller has a low supply voltage range of 1.8V to 3.6 Volts. A voltage divider circuit

was used with the Light Dependent resistor connected to a voltage Vcc of 3.6V.

Figure 15: Light Sensor Design

The output voltage was taken from the middle of the voltage divider, it is given by the

equations 1 = 11 + 1Where Vo1 stands for output voltage from sensor1 and Rldr1 is the resistance of LDR1

27

Also, 2 = 21 + 2Where Vo1 stands for output voltage from sensor2 and Rldr2 is the resistance of LDR2

3.5 The Choice of Microcontroller

The micro-controller chosen for the project was the MSP430G2553 from Texas Instruments.

According to [16], the MSP430G2553 is an ultra-low-power mixed signal microcontrollers

with built-in 16-bit timers, up to 24 I/O capacitive-touch enabled pins, a versatile analog

comparator, and built-in communication capability using the universal serial communication

interface. In addition the MSP430G2x53 family members have a 10-bit analog-to-digital

(A/D) converter.

These capabilities made the MSP430G2553 a suitable choice of microcontroller for use in

the project.

The pin configuration for the microcontroller is as shown below

Figure 16: Msp430G2553 pinout, from [16]

The Texas Instruments Launchpad was used to program the micro-controller through Energia

software version 0101E0017. This software tool proved very useful in programming the

28

micro-controller as it was simple to use and enabled programming of the Msp430 micro-

controller via USB.

3.6 Hardware Schematic Diagram

Figure below shows the hardware schematic diagram of the system, simulated using the Proteus

8 software. Because the MSP430G2553 was not available in the software, a close alternative was

chosen, as shown on the schematic.

The input into the system is two LDR voltages into pins P1_1 and P1_2 of MSP430

microcontroller. The analog voltages are then converted to digital equivalents in the range 0-

1023 microcontroller ADC. The microcontroller then compares the two digital values and

generates a Pulse Width Modulated (PWM) wave to drive the servo motor accordingly. The

servo motor is connected to pin of the micro-controller.

Figure 17: Hardware Schematic

29

3.7 PCB Schematic of the circuit design

30

Chapter 4: Results and Analysis

4.1 RESULTS

The results for this project were obtained from a 5watt solar panel which was connected to a

4.7ohm load, while the panel attached to the moving (tracking) panel and the secondly, when

attached to a fixed (non-tracking) panel.

These results were taken over a period of two moderately sunny days 11th May 2016 and 14th

May 2016, although the cloud cover produced a bit of challenge. Regardless, results were

obtained satisfactorily, and were as shown in the tables below

Table 1: Results for Morning and Afternoon of 14th May 2016 (Sunny with partial cloud cover)

Time of Day Voltage across the Load Current through load Power

Fixed Panel(volts)

Tracking Panel(volts)

Fixed Panel(miliAmps)

Tracking Panel(miliAmps)

Fixed Panel (Watts)

TrackingPanel (Watts)8:00 AM 0.6 1.204 117 258 0.0702 0.310632

9:00AM 0.67 1.29 144 268 0.09648 0.3457210:00AM 0.974 1.31 178 270 0.173372 0.353711:00AM 1.498 1.601 314 328 0.470372 0.52512812:00PM 1.58 1.67 335 347 0.5293 0.579491:00PM 1.67 1.76 350 358 0.5845 0.630082:00PM 1.41 1.58 288 330 0.40608 0.52143:00PM 0.92 1.31 200 280 0.184 0.36684:00PM 0.6 0.91 131 190 0.0786 0.17295:00PM 0.36 0.84 78 175 0.02808 0.1476:00PM 0.108 0.402 6 84 0.000648 0.033768

31

00.20.40.60.8

11.21.41.61.8

2

8:00 AM 9:00AM 10:00AM 11:00AM 12:00PM 1:00PM 2:00PM 3:00PM 4:00PM 5:00PM 6:00PM

Volta

ge (v

olts

)

Time of Day

Comparison of load Voltage for Fixed Panel andTracking Panel

Fixed Panel Tracking Panel

0

50

100

150

200

250

300

350

400

8:00 AM 9:00AM 10:00AM11:00AM12:00PM 1:00PM 2:00PM 3:00PM 4:00PM 5:00PM 6:00PM

Curr

ent (

Mili

amps

)

Time of Day

Comparison of load current when using fixed andtracking panel


32

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


Pow

er (W

atts

)

Time of Day

Comparison of power output of fixed panel andtracking panel


33

Table 2: Results for 11th May 2016 (Sunny Day)

Time of Day Voltage across the LoadCurrent through load Power

Fixed Panel(volts)

TrackingPanel(volts)

Fixed Panel(miliAmps)

TrackingPanel(miliAmps)

FixedPanel (Watts)

TrackingPanel (Watts)

8:00 AM 0.588 1.224 107 242 0.062916 0.2962089:00AM 0.612 1.258 142 288 0.086904 0.36230410:00AM 1.004 1.281 178 265 0.178712 0.33946511:00AM 1.469 1.598 306 338 0.449514 0.54012412:00PM 1.568 1.702 328 357 0.514304 0.6076141:00PM 1.72 1.76 355 361 0.6106 0.635362:00PM 1.52 1.59 288 320 0.43776 0.50883:00PM 1.02 1.41 208 288 0.21216 0.406084:00PM 0.88 1.04 141 188 0.12408 0.195525:00PM 0.358 0.88 78 172 0.027924 0.151366:00PM 0.102 0.442 12 102 0.001224 0.045084

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2


Volta

ge (V

olts

)

Time of Day

Comparison of load voltages of fixed and trackingpanel


34

4.2 ANALYSIS

.

From the reading of voltage and current across the 5W 4.7 ohm load, the values of power were

calculated using the following formula

Power= Voltage x Current

Pload=VI

The values calculated using this formula are as shown in table 1 and table 2 in section 4.2

previously

Thre value of efficiency of both the tracking panel and the fixed panel was calculated with

respect to the Maximum rated output power of the solar PV panel, which was 5W= ∗ 100%For 14th May 2016 at 8AM the Tracking PV panel had an output Power of 0.361W and the Fixed

PV panel had an output power of 0.072W therefore, giving efficiency of( ) = 0.3615 ∗ 100% = 7.22%( ) = . ∗ 100%= 1.44%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7


POw

er O

utpu

t (W

atts

)

Time of Day

Comparison of Load Power for different time of day


35

Other values of efficiency were calculated using Microsoft excel and are as shown below

Table 3: Values of Efficiency of the tracked and fixed panels

From the above, it is clear that improvement of efficiency when using the solar tracking system

was more pronounced in the morning and evening hours with the biggest improvement in

efficiency being around 5%.

Time of Day Power EfficiencyFixed Panel (Watts)

TrackingPanel (Watts)

FixedPanel

TrackingPanel

Improvement in Efficiency

8:00 AM 0.0702 0.3106 1.40% 6.21% 4.81%9:00AM 0.09648 0.3457 1.93% 6.91% 4.98%10:00AM 0.1734 0.3537 3.47% 7.07% 3.61%11:00AM 0.4704 0.5251 9.41% 10.50% 1.09%12:00PM 0.5293 0.5795 10.59% 11.59% 1.00%1:00PM 0.5845 0.6301 11.69% 12.60% 0.91%2:00PM 0.4061 0.5214 8.12% 10.43% 2.31%3:00PM 0.184 0.3668 3.68% 7.34% 3.66%4:00PM 0.0786 0.1729 1.57% 3.46% 1.89%5:00PM 0.0281 0.147 0.56% 2.94% 2.38%6:00PM 0.0006 0.0338 0.01% 0.68% 0.66%

36

0

1

2

3

4

5

6

8:00 AM 9:00AM 10:00AM 11:00AM 12:00PM 1:00PM 2:00PM 3:00PM 4:00PM 5:00PM

Effic

ienc

y Im

prov

emen

t

Time of Day

Improvement in efficiency

37

Chapter 5: Discussion, Conclusion and Recommendations

5.1 Discussion

From the curves of voltage, current and power output of the tracking and fixed panel, it can be

seen that the maximum power occurs at around 1PM. At this time it was seen that both the

tracking panel and fixed panel were receiving almost the same power because the azimuth angle

of the sun is approximately zero and the sun rays were striking the panel perpendicularly.

In the morning and late evening, the intensity of sunlight continually decreasing and the values

obtained are less than those obtained during the middle of the day

From the experimental results and analysis it can be seen that In terms of the power output of the

solar panels for tracking and fixed systems, it is evident that the tracking system has increased

power output when compared to the fixed panel, this is because the power generated by solar PV

panels is directly proportional to the intensity of light. The panel on the solar tracking system is

continuously facing the sun and therefore has relatively more sunlight falling on it, this means

increased power output, hence increased efficiency.

It was also noted that the greatest improvement of efficiency was evident in the morning and

evening hours where the fixed panel was receiving its least power. During hours around midday,

both the fixed and the tracking panels were receiving almost the same amount of intensity and

therefore the improvement in efficiency was small in the hours between 11-2 PM since the

power output was seen to be almost same for both panels.

The main aim of this project was to improve the efficiency of solar panels by use of a

microcontroller-based solar tracking system. The implemented solar tracking system was seen to

achieve this objective satisfactorily.

Design and implementation of the solar tracking system was achieved through the use of light

sensors (light dependent resistors), micro-controller, and a servo motor. The resistance property

of the LDRs varied depending on the amount of sunlight falling on it, this was then converted to

an analog voltage by using a voltage-divider circuit and a dc source, this analog voltage when

fed to the microcontroller (incorporated with an analog-to-digital converter) enabled the

38

microcontroller to know the direction of the sun, and thereby send control signals to the motor

moving in that direction.

The servo only stops when the two LDRs have the same reading, meaning that they receive the

same amount of light intensity and the panel is directly facing the sun. As long as the micro-

controller and the servo-motor are powered, the sun tracking is constantly done.

5.2 Conclusion

The main aim of this project was to improve the efficiency of solar PV panels by use of a

microcontroller-based solar tracking system. The designed and implemented single axis solar

tracking system proved to be sufficient and was seen to improve the efficiency sufficiently.

The project was done within the allocated time and using the available resources to produce a

low-cost but effective prototype that solves the problem at hand.

5.3 Recommendations

Although a simple and effective prototype of a solar-tracking system was implemented,

several improvements can be done on it in future works to make it even better.

1. Use of a more powerful servo-motor in order to effectively carry commercial size

solar panels. Since this was a prototype, a small servo was used due to cost

constraints.

2. Incorporating sensors at the back of the panel mounting so as to detect sunlight during

sunrise and sunset. With a few modifications to the algorithm, the solar tracking

system can be made to turn off at sunset and turn-on at sunrise. This can effectively

decrease the power consumption of the solar tracking system making it even more

efficient.

3. Improving the design of the mounting and use steel which is strong enough to support

more weight and can be made smaller, in order to allow more freedom of movement

of the panel. The mounting used in the prototype limited movement to a span less

than 120 degrees instead of the available 180 degrees allowed by the servo motor.

40

References

[1] D. R. P. Stephen W. Fardo, Electrical Power Systems Technology, Lilburn:

Fairmont Press, 2009.

[2] J. V. Roger A. Messenger, Photovoltaic systems Engineering, Third ed., New York:

CRC Press, 2010.

[3] N. O. a. A. Adminstration, "National Weather Service," National oceanic and

atmospheric adminstration, 26 January 2016. [Online]. Available:

http://www.weather.gov/cle/seasons.

[4] S. Roberts, Solar Electricity, A Practical guide to Designing and Installing Small

Photovoltaic Systems, Prentice Hall, 1991.

[5] B. Lane, "Solar Tracker," Cleveland State University, Cleveland Ohio, 2008.

[6] E. O. ,. B. L. W. M. S. Lakeou, "Design of a Low-cost Solar Tracking Photo-Voltaic

(PV) Module and Wind Turbine Combination System," University of Colombia.

[7] N. S. Narayan, "Solar Charging Station for light Electric vehicles, A design and

feasibility study," 2013.

[8] R. D. Gerro Prinsloo, Solar Tracking, Stellenbosch University, 2014.

[9] Handbook of Photoelectric Sensing, Second ed., Minneapolis: Banner Engineering

Corp, 1993.

[10] J. Murphy, Understanding AC induction, permanent magnet and servo-motor

Technologies, Wisconsin: Leeson Electric Co-operation.

[11] "Basics of Servo Motor Control," Nippon Pulse Motor Company Ltd, Radford,

2013.

[12] ServoCity, "servoCity.com," RobotZone, LLC, [Online]. Available:

https://www.servocity.com/html/how_do_servos_work_.html. [Accessed 2 February

2016].

[13] B. W. Gunther Gridling, Introduction to Micro-controllers, Vienna University of

41

Technology, 2007.

[14] A. V. Deshmukh, Microcontrollers- Theory and Applications, New Delhi: McGraw

Hill, 2007.

[15] J. Davies, MSP430 Microcontroller Basics, Oxford: Newnes, 2008.

[16] T. Instruments, "MSP430G2553 Datasheet," Texas, 2013.

42

APPENDIXProject Gantt Chart

The code used in the micro-controller

#include <Servo.h>

Servo myservo; // create servo object to control the servo

int pos = 90; // initialize the motor at an angle of 90 degrees

void setup()

{

//initial setup

pinMode(11,OUTPUT);

myservo.attach(9); // attaches the servo on pin 9 to the servo object

myservo.write(pos); // tell servo to go to position in variable 'pos'

delay(15); // waits 15ms for the servo to reach the position

}

void loop()

{

// main code to run repeatedly

int LDR1=analogRead(A3); // Read the value from LDR1

43

int LDR2=analogRead(A4); // Read the value from LDR2

if (LDR1>LDR2 && LDR1-LDR2>30){

//compare the two LDR values

digitalWrite(11, LOW);

if(pos<135){

pos+=1;

//move the servo



}

}

else if (LDR2>LDR1&& LDR2-LDR1>30){

//compare the two LDR values

digitalWrite(11, LOW);

if(pos>45){

pos-=1;

//move the servo



}

}

else {

digitalWrite(11, HIGH);

}

}

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