1

A Project Report on

SOLAR TRACKER FOR SOLAR PANEL

Submitted By

Mukesh Choudhary[T120223066]

Neeraj Bani [T120223067]

Prashant Kumar [T120223077]

A Seminar report submitted as a partial fulfilment towards term VI of

T.E (Electronics & Telecommunication)

Savitribai Phule Pune University

Guide

Mrs. Sushma Wadar

Department of E&TC Engineering

Army Institute of Technology, Dighi , Pune – 411015

2014-2015

2

C E R T I F I C A T E

This is to certify that

Prashant Kumar

Neeraj Bani

Mukesh Choudhary

Of Army Institute of Technology, Dighi, Pune

Have submitted Project Seminar report on

SOLAR TRACKER FOR SOLAR PANEL

As a partial fulfilment of Term-VI for award of degree of Bachelor of

E&TC from Savitribai Phule Pune University during the

Academic Year 2014-2015

Project Guide H.O.D

Mrs. Sushma Wadar Mrs.Surekha K.S

3

ACKNOWLEDGEMENT

We would like to express our heartfelt gratitude to Mrs. Shusma Wadar , who is

our supervisor, for her constant guidance in the implementation of this project.

We must particularly thank her for commitment and unrelenting effort to see

us do all the assignments appertaining to this project and finally we can say we

had done.

Again, special thanks to providing us with MSP430 microcontroller together

with the Launchpad which was the very core of my project embedded software

Section.

We would also like to thank H.O.D and all the staff members’ and our colleagues

for their cooperation and support during the collection of materials and also

during our Project. All of your sup

Port has motivated us in many instances. All of the experience has been

educating, humbling and very nostalgic

Thank you all.

4

ABSTRACT

The project involves design and implementation of an automatic microcontroller

based solar tracker system expected to be used in photovoltaic conversion

panels. The proposed single axis solar tracker device functions to ensure the

optimization of the photovoltaic panel in accordance with the real position of

the sun. The operation of experimental model of the device is based on a DC

motor which is intelligently controlled by a dedicated drive unit that moves a

mini PV panel according to the signals received by a microcontroller from two

simple but efficient light sensors. The performance and characteristics of the

solar tracker device are experimentally analyzed.

5

Index

Abstract

CHAPTER TITILE PAGENO.

1. INTRODUCTION …………………………………….....[6-7]

1.1 General Background

1.2 Problem Statement

1.3 Project Justification

1.4 Objectives

2. LITERATURE REVIEW……………………………….[8-15]

2.1 Introduction

2.1.1 Types of Solar Trackers and Solar Tracking Techniques

2.1.2 Single Axis Solar Tracking System

2.1.3 Dual Axis Solar Tracking System

2.1.4 Active Solar Tracking

2.1.5 Passive Solar Tracking

2.1.6 Review of Solar Tracking Methods

2.2 A Review of Solar Tracking Methods

2.2.1 Introduction

2.2.2 Solar Tracking in Relation to Rotation and Revolution of the Earth

2.2.3 Nature of Solar Irradiation and the Solar Constant

2.2.4 Sunlight

2.2.5 The Solar Constant

2.2.6 Fixed and Tracking Collectors

2.2.7 Fixed Collectors

2.2.8 Tracking Collectors: Improved Efficiency

3. BLOCK DIAGRAM / FLOW CHART ………………[16-23] 3.1 Light Sensor Theory and Circuit of Sensor Used

3.2 Block Diagram

3.3 Graphical user interface

3.4 Flow chart

3.5 Algorithm

4. METHODOLOGY ……………………………………[ 24 ]

5. ADVANTAGES AND DISADVANATES……………[ 25 ]

6

6. SCOPE OF IMPROVEMENT………………………..[ 26 ]

7. CONCLUSION ………………………………………..[ 27 ]

REFERENCES……………………………………………..[ 27 ]

ABBREVIATIONS AND ACRONYMS…………………[27-28]

APPENDIX………………………………………………..[28-31]

7

Chapter 1

INTRODUCTION

1.1 General Background

Today’s world has increasing demands for energy by the day, which is against

the continuous reduction in existing resources of fossil fuels and ever growing

concern regarding environmental pollution. It’s therefore needless to say that

this has pushed mankind to explore new technologies for production of

electrical energy, using clean, renewable sources such as solar and wind power.

A prominent non-conventional renewable energy source is solar energy which

provides great prospect for conversion into electrical power, which in turn

ensures an important part of the electrical energy needs of the planet.

Photovoltaic (PV for short) is the conversion principle employed in conversion

of solar light into electricity. Using solar tracking technique, yield from solar

panel can be increased by 30%-60% unlike in stationary or fixed installations

which if we assume silicon is the material used to build the PV panels, then the

system is only about 24.5% efficient .

1.2 Problem Statement

A solar tracker device has a wide range of applications to improve harnessing of

solar isolation. The problem posed thus is to implement a system that is capable

of improving solar power production by 30-40%. A microcontroller is used to

implement the control circuit which in turn positions a motor used to orient the

solar panel optimally.

1.3 Project Justification

The aim of this project is ensure that sunlight rays are falling perpendicularly on

the solar panel to give the maximum solar energy which is harnessed into

electrical power with the maximum energy being between the period of

1200Hrs to 1400Hrs with the peak around midday when the sun is almost

directly above the solar panel and so minimum energy is used to move the solar

panel, further increasing the efficiency of the tracker. This project seeks to

address the challenge of accurate, low power as well as economical

8

microcontroller based solar tracking system that can be implemented using the

allocated time and resources so as to track the relative motion of the sun in the

sky during daylight and to save the much needed power, sleep at night. An

algorithm is implemented to solve the problem of motor control which is then

written into C.

2 program on Code Composer Studio IDE for MSP430G2553 microcontroller.

Readily available and economical tools will be used to implement the project.

1.4 Objectives The project seeks to satisfy the following objectives I. Design a system to track solar UV light for solar panels II. Accurately identify and measure the altitude angle from sunrise to

sunset for Pune. III. Commonly called the Green City under the Sun.

9

CHAPTER: - 2

LITERATURE REVIEW

2.1 Introduction Among the renewable energy sources is electrical solar energy from the Sun can be harnessed using solar panels or solar cells to convert solar irradiation into electrical current. Most photovoltaic cells employ photoelectric effect. This is a process by which electrons are emitted from some materials, such as a metal, as a result of being struck by photons. Some substances, such as selenium, are particularly susceptible to this effect and if used in solar cells, they can generate some electric potential through photoemission. Sun rays come in form of UV-light, a form of electromagnetic radiation and once they fall of solar panel surface made of materials such as silicon, the irradiation is absorbed and converted into electrical energy through photo emission. Maximum absorption occurs when the solar panels and solar cells directly face the Sun, so that the sun’s rays fall perpendicularly on the absorption surface. This absorption and conversion may not be optimal given that the solar panels and solar cells are mounted in fixed positions usually on rooftops with slants. For viable solar energy generation using single installation, its efficiency has to be improved and therefore various solar tracking methods are devised to closely track sun movement during the day. 2.2 Types of Solar Trackers and Solar Tracking Techniques Modern solar tracking methods can be classified into the following categories: 2.2.1: Single Axis Solar Tracking System This is method is usually used for solar trackers aimed to be used in the tropics where the focus is to track the angle of altitude (angle of tilt) of the sun along a single axis. A single linear actuator is used, such as a motor to drive the panel according to sun movements. A set of two LDRs on opposite sides of the solar panel may be used to measure the intensity of the solar irradiation by measuring the voltage drop across them which is then compared by a drive circuit until the two LDR voltages are equal and the motion of the panel is stopped. This way, the solar panel is always oriented, normally to sun irradiation

10

2.2.2: Dual Axis Solar Tracking System This method is mainly designed for localities outside the tropics or areas beyond 10°N and 10°S of Equator. In this technique, both angle of azimuth and angle of Tilt of the solar tracker are used to track the sun movements throughout the year. Consequently, a set of two actuators, usually motors is used to move the solar panel accordingly by receiving voltage control signals from a set of four LDRs (two on opposite sides of solar panel) and when the voltage drop on all the four LDRs is equal then the panel is experiencing the maximum solar irradiation and therefore the motion stops. This ensures the solar panel is at right angles with sunlight at all times

Figure 1 Single Axis Solar Tracking System

Figure 2 Dual Axis Solar Tracking System

11

2.2.3: Active Solar Tracking

This technique involves the continuous and constant monitoring of the sun’s position throughout daytime and when tracker is subjected to darkness it stops or sleeps according to its design. This can be done using of light sensitive sensors, such as photo resistors(LDRs) whose voltage output are input into a microcontroller which then drive actuators (motors) to adjust the solar panels position.

2.2.4: Passive Solar Tracking

This method involves trackers that determine the Sun’s position by means of a pressure imbalance created at two ends of the tracker. This imbalance is caused by solar heat creating gas pressure on a low boiling point compressed gas fluid that is driven to one side or the other which then moves the structure.

2.3 A Review of Solar Tracking Methods

2.3.1: Introduction

As stated above, there is an urgent need for better solar tracking technologies

to be developed to harness vast amounts of electrical solar energy in large scale

to cater for the ever growing power demand. Of concern too is the reduction in

the environmental pollution due to use of fossil based fuels. To construct a cost

effective, efficient and effective solar tracking system, it is necessary to

understand the rotation and revolution of the Earth with respect to the locality

in question so as to know the specification of the solar tracker to be constructed.

Since any solar tracker follows the motion of the sun in the sky, it is very

necessary to understand rotation & revolution of the. Earth, solar irradiation

and efficiency of tracking systems which will be shown in later in this project.

2.3.2: Solar Tracking in Relation to Rotation and Revolution of the Earth

The Earth rotates about its own axis taking 24 hours to complete one rotation of

360 degrees and at the same time it revolves around the sun in a year of 365¼ days

or 366 in a leap year. Revolution takes place in an elliptical orbit called the ecliptic.

In addition to the revolution of the. Earth, it is observed that the relative position of

the midday Sun at different times of the year varies. The inclination of the sun from

the earth is referred to as the solar altitude angle.

This is the vertical angle between the projection of Sun’s rays on the horizontal plane

and direction of sun’s rays passing through the point. Usually this is estimated to

be a decline of 23½ degrees northwards and southwards, in one complete

revolution about the Sun. The Earth also has an axial tilt of about

23.4°.The altitude of the sun can also be explained by use of solar zenith angle (θz)

which is a vertical angle between Sun’s rays and a line perpendicular to the

horizontal plane through the point (θ z =90 - α). Solar azimuth angle (γs) is the

horizontal angle measured from south (in the northern hemisphere) to the

horizontal projection of the Sun’s rays.

12

2.4 Nature of Solar Irradiation and the Solar Constant

Sunlight contains UV light which is a solar radiation in form of an electromagnetic

radiation given off by the Sun. Resulting from the intense temperature and

pressure at the core of the Sun, solar fusion takes place. Protons are converted into

helium atoms at a rate of 600 million tons per second. Since the output of this

process has lower energy than the protons that began, the fusion gives off a

tremendous amount of energy in the form of gamma rays. These gamma rays are

absorbed by particles in the Sun, and then re-emitted. Over the course of 200,000

years, photons of light make their journey through the radiation zone of the Sun.

Solar irradiation is the measure of the total incident solar radiation transmitted to

the surface of the Earth’s atmosphere in a given unit of time. Solar radiation from

the. Sun can be direct, diffuse nor reflected. Direct radiation, also called beam

radiation, is the solar radiation travelling on a straight line from the sun down to

the surface of the Earth. Diffuse radiation refers to the sunlight that has been

scattered by molecules and particles in the atmosphere but that has still made it

down to the surface of the earth. Unlike direct radiation, diffuse radiation doesn’t

have a definite direction. Reflected radiation describes the Sunlight that has been

reflected off of non-atmospheric surfaces such as the ground. The solar radiation

data are usually given in the form of global radiation on a horizontal surface and

solar and PV panels are usually positioned at an angle to the horizontal plane.

2.4.1: Sunlight

Photometry enables us determine the amount of light given off by the Sun in

terms of brightness perceived by the human eye. In photometry, a luminosity

function is used for the radiant power at each wavelength to give a different

weight to a particular wavelength that models human brightness sensitivity.

Photometric measurements began as early as the end of the 18th century

resulting in many different units of measurement, some of which cannot even

be converted owing to the relative meaning of brightness. However, the

luminous flux (or lux) is commonly used and is the measure of the perceived

power of light. Its unit, the lumen, is concisely defined as the luminous flux of

light produced by a light source that emits one candela of luminous intensity

over a solid angle of one steradian. The candela is the SI unit of luminous

intensity and it is the power emitted by a light source in a particular direction,

weighted by a luminosity function whereas a steradian is the SI unit for a solid

angle; the two-dimensional angle in three dimensional space that an object

subtends at a point.

13

2.4.2: The Solar Constant

The is defined as the amount of solar energy received upon a unit surface by the

Earth’s atmosphere, perpendicular to the Sun’s direction and is usually

expressed in calories per square centimeter per minute, and in these units,

common values are in the range 1.89 to 1.9cm/minute. The determination of

the solar constant is facilitated by solar spectral-irradiance curves. These are

obtained with a recording spectrobolometer (a combined spectroscope and

bolometer for determining the wavelength distribution of radiant energy

emitted by a source) and referenced to a measurement obtained from a

pyrheliometer that determines the total radiation at the same time.

2.5. Fixed and Tracking Collectors

2.5.1 Fixed Collectors

Harnessing of solar energy can be done using either fixed or movable collectors.

Fixed collectors are mostly mounted on the places with maximum sunlight and at

relatively good angle in relation to the sun such as rooftops. The aim is to expose

The panel for maximum hours in a day without necessarily involving tracking

technologies and therefore a considerable reduction in installation and

maintenance cost is realized. As such, majority of the collectors are fixed type.

For fixed solar collectors therefore is very necessary to know the position of the

sun at various seasons and time s of the year so as to give the optimum orientation

of the collector during installation to give the maximum solar energy

14

All year round. Since the focus of this project was to design a solar tracker device

To be used in Nairobi, the sun chart diagram of this locality is

By using this chart, we can almost definitively ascertain the position of the sun

during different time and seasons of the year such that we are able to fix the

payload, in this case a fixed solar panel or photovoltaic cell to give us the maximum

energy output. As previously discussed, it should be noted that fixed solar trackers

are cheaper and therefore more preferred around countries in the tropics region,

Kenya being no exception. In fact in chapter 3, the results will be

recorded and analyzed for both fixed and tracking solar panel to point out the

differences in efficiency. However, for countries beyond +10degrees North and -

10degrees South of Equator, there is serious need for solar tracking since the

Figure 2.1 Sun path in Pune

15

number of sunshine hour’s maybe less and/or the position of the midday sun may

vary significantly. As is evident from this chart, the position of the sun in the sky is

highest in the period between the hours of 1200h and 1400h. For hours outside

this range, the solar collectors are obliquely oriented to the Sun and as a result,

only a fraction reaches the absorption surface of the solar collector since the

payload cannot track sun movements.

2.5.2: Tracking Collectors: Improved Efficiency For a tracking collector, the theoretical extracted energy is calculated assuming that the maximum radiation intensity I = 1100 W/m2is falling on the area which is oriented perpendicularly to the direction of radiation. Taking the length of day t = 12h = 43200s, the intensity on the tracking collector which is always optimally oriented facing the Sun is compared to that of a fixed collector which is oriented perpendicularly to the direction of radiation only at noon. The collector area is marked as So.

16

CHAPTER: - 3

BLOCK DIAGRAM/FLOW CHART/ALGORITHM

3.1: Light Sensor Theory and Circuit of Sensor Used

Light detecting sensor that maybe used to build solar tracker include;

phototransistors, photodiodes, LDR and LLS05. A suitable, inexpensive, simple

and easy to interface photo sensor is analog LDR which amongst the light

sensors is the most common in electronics. It is usually in form of a photo

resistor made of cadmium sulfide (CdS) or gallium arsenide (GaAs).

Next in complexity is the photodiode followed by the phototransistor.

The solar tracker in this project uses a cadmium sulfide (CdS) photocell for light

sensing. This is the least expensive and least complex type of light sensor.

The CdS photocell is a passive component whose resistance in inversely

proportional to the amount of light intensity falling on it. To utilize the

photocell, it is placed in series with a resistor (B10K potentiometer in this

case). A voltage divider is thus formed and the output at the junction is

determined by the two resistances. Figure 1 illustrates the photocell circuit. In

this project, it was desired for the output voltage to increase as the light

intensity increases, so the photocell was placed in the top position as shown

below.

3.1 .1 Construction and Operation of an LDR:-

The cadmium sulfide (CdS) or light dependent resistor (LDR) whose resistance is

inversely dependent on the amount of light falling on it, is known by many names

including the photo resistor, photoresistor, photoconductor, photoconductive cell,

or simply the photocell. A typical structure for a photoresistor uses an active

semiconductor layer that is deposited on an insulating substrate. The

Figure 2.2 LDR

17

semiconductor is normally lightly doped to enable it to have the required level of

conductivity. Contacts are then placed either side of the exposed area. The photo-

resistor, CdS, or LDR finds many uses as a low cost photo sensitive element and was

used for many years in photographic light meters as well as in other applications

such as smoke, flame and burglar detectors, card readers and lighting controls for

street lamps [2]. Since this is

3.1.2 Light Sensor Design

As presented in Chapter above, the sun tracker uses a CdS photocell for light

detection. A complementary resistor value of 10 KΩ was used to construct the

circuit shown in Figure 3. 1 above. In this configuration, the output voltage will

increase as light intensity .The complementary resistor value should be chosen such

as to achieve the widest output range 15 possible. Photocell resistance was

measured under dark conditions, average light conditions, and bright light

conditions. The results are listed in Table below

3.2 Simple DC Motor and Driver Theory

A small simple Dc motor was chosen as the actuator in this project due to the

following advantages:

• Continuous duty operation.

• DC power supply (battery or speed controls)

• Reversibility at rest or during rotation with current limiting

• Relatively constant and adjustable speed

• High starting torque

A 5Volts DC motor was connected to pins 3 and 7 of the H-Bridge circuit and for

reversing and forward movement of the panel according to the signals received

from MSP 430 microcontroller. A small pulley drive was secured into the shaft of

the DC motor to link it with the axle holding the panel. This setup was sufficient to

provide the torque required to move the panel in solar tracking.

3.2.1 L293D H-Bridge

Due to power efficiency requirements of the project, this IC module was preferred

as opposed to H-Bridge using MOSFETS . It was chosen due to the following

features.

1. Wide Supply-Voltage Range: 4.5 V to 36 V

2. Separate Input-Logic Supply

3. Internal ESD Protection 17

4. Thermal Shutdown when very hot and puts itself OFF

5. High-Noise-Immunity Inputs

18

6. Output Current 600mA per channel

7. Output Clamp Diodes for Inductive

Figure 3. 1: Pin out diagram for L293D

Inputs Outputs

A EN Y

H H H

L H L

X L Z

Table 3. 2: Function table for L293D H-Bridge

H=High

L=Low

X=Irrelevant

Z=High Impedance or OFF state

3.3 Microcontroller

Like a computer it has the common parts being central processing unit (CPU), some

RAM and input and output data bus. Principally a microcontroller was chosen to

design the tracker because of the following advantages:

It formed part of embedded software design where a C-Program was loaded into

it

It acted as a dedicated unit by being programmed for one purpose being motor

control.

It had dedicated input device in addition to readily available programmer

Another advantage was the capabilities of programming the microcontroller using

a high level language, C which comes in the form of Code Composer Studio IDE from

Texas Instruments. The main advantage of C is its simplicity.

19

3.3.1 Choice of Microcontroller

Since the project’s focus is on embedded software control, the microcontroller is

the heart of the system. The microcontroller selected for this project had to be able

to convert the analog photocell voltage into digital values and also provide four

output channels to control motor rotation. The MSP430G2553 was selected as it

satisfies these requirements in addition to already being provided with the class lab

kit. Specifically, it possesses the following three features to satisfy the specific

project goals [5].

3.4 Voltage Regulation

The L293D H-Bridge requires a regulated 5 volt supply voltage. The 7805 voltage

regulator was used to provide for that. Again when the MSP430 was used on

breadboard, required regulated 3.3volts which was provided by AMS1117.The

LM7805 voltage regulator the circuits used supply 5volts to the H-bridge is as

shown below.

Figure 3. 5: Voltage Regulator Circuit LM7805

20

Notice functions of the capacitors include:

Reducing the electromagnetic noise

Provide voltage sink and voltage source

The diode prevents unwanted reversal of the current which could damage the chip

when it is powered.

The MSP-430 works with 3.3v power supply. Which is provided by voltage regulator

IC AMS1117 -3.3 v. The circuit diagram for AMS1117 is shown below

Figure 2PCB layout

Figure 1AMS1117

21

3.5 The Design Tool

3.5.1 Code Compose Studio V5

This tool was chosen to implement software design and editing due to ease of use

and text editing capabilities. Moreover, Texas Instruments Kit was provided

together with the USB which further made loading code into the microcontroller

easier. Proteus Circuit editing Software was 20 used to draw the circuits required

and also for various simulations of various stages. The algorithms are as under: The

flow chart for the algorithm shown next is on the next page

3.5.2 Algorithm for Motor Control

This algorithm describes the general steps undertaken in the project.

1. Input the voltages from two LDRs,

2. Convert the above analog voltage signals into digital values between 0-1023,

3. Compare the two digital values and get the difference between them,

4. Set the difference as the error proportionate angle for simple DC motor rotation,

5. If the LDR voltages are equal stop DC motor.

The flow chart of Fig 3.6 illustrates the implementation of this algorithm. The input

into the system is two LDR voltages into pins 2 and 3 of MSP430 microcontroller.

The analog voltages are then converted to digital equivalents in the range 0-1023

microcontroller ADC. The 2 digital values are then compared and depending on

which is larger a signal is sent to the driver circuit which then drives the DC motor

to the direction with more light intensity. The diagram below shows the block

diagram of the solar tracking device

22

Next, all the components are assembled as seen in the schematic diagram shown

below. However, since MSP430G2553 was not in Proteus, a close substitute was

used for schematic diagram purposes. It can be seen that the input stage comprise

the LDR and the divider circuit, which feeds the voltage outputs to the

microcontroller. The embedded software design entails the C-code loaded into the

MSP430 and the code used is shown at the appendix later in the report.

A simple DC motor is connected to the output pins 3 and 7 of the H-Bridge and the

outputs from the microcontroller are input into the H-Bridge through pins 2 and 6.

The function of the H-bridge id direction reversal of the DC motor Since the MSP is

not available in Proteus circuit maker and simulation software, it was

impossible to simulate the code after loading in the code composer. However, the

LDR inputs were simulated.

3.6. Construction Ultimately the subparts of the project discussed in Chapters 3.1 through 3.5 were consolidated to construct a complete project. Figure 3.7 provides a block diagram of the project while Figure 3.8 provides a complete hardware schematic of the project. Some additional construction details worth mentioning deal with the motor and photocell. The motor was mounted to a wooden frame using a metallic strip to provide a stable base for it. The photocell was mounted on a small wood Platform with a broad base. The axle holding the photocell was connected to the motor shaft using a small pulley drive.Fig3.7

Figure 3.5Simulation Diagram

23

Figure 4MSP430G2553

24

CHAPTER: - 4

METHODOLOGY

This solar tracking system will have three salient components; an input stage with

light sensors and potentiometer, a program in embedded software in

microcontroller and a driving circuit in form of H-bridge. The input stage is two LDRs

which are part of voltage divider circuit. L293D chip forms the driver circuit and a

C-program loaded into MSP430 forms the embedded software. All the parts are

designed independently and then assembled into a solar tracking system. Finally a

wooden frame is used to house the components required to execute the tracker.

5.1: Design and Results Analysis

Hardware and software portions of the project were separated into stages while

developing the overall system. The portions consisted of light detection, motor

driving, software tracking, and software enhancements. Building and testing

smaller Chapters of the system made the project more manageable and increased

efficiency by decreasing debugging time. The project performs the required

functions envisioned at the proposal phase. However, while satisfied with software

operation and simulation, less satisfaction was obtained from two hardware areas.

First, there is a potential for problems with motor/photocell movement due to the

photocell wires creating binding issues. There are two wires attached to the

photocell then connected to control circuit. Once the tracker has moved

approximately 30 to 45 degrees, the wires place a counter torque on the motor and

the motor slips. This creates positioning error. The present workaround for this is

to hold the photocell wires in a way as to keep them close to the wooden frame

which holds the photocell as the tracker moves. This problem will be discussed

further in Chapter 5. The second issue deals with the photocell. It was discovered

that the photocell needs to be shielded such that light can be directed narrowly to

its surface. This was done by placing a black vinyl tube around the photocell to

create a tunnel and help shield it from light that is not directly in its direct path.

25

CHAPTER: 5

ADVANTAGES AND DISADVANATES

Solar energy offers many advantages over other forms of energy. Some of those

benefits are listed below:

1. The 89Petawatts of sunlight reaching the earth's surface is plentiful – almost

6,000 times more-compared to the 15 terawatts of average power

consumed by humans. Additionally, solar electric generation has the highest

power density (global mean of 170 W/m²) among renewable energies.

2. Solar power is pollution free during use.

3. Production end wastes and emissions are manageable using existing

pollution controls and end-of-use recycling technologies are also under

development.

4. Facilities can operate with little maintenance or intervention after initial

setup. Solar electric generation is economically superior where grid connection

or fuel transport is difficult, more costly or impossible. Examples include

satellites, island communities, remotely locations such as ocean vessels.

5. When grid-connected, solar electric generation can displace the highest cost

electricity during times of peak demand (in most climatic regions), can reduce

grid loading, and can eliminate the need for local battery power for use in times

of darkness and high local demand; such application is encouraged by net

metering.

6. Grid-connected solar electricity can be used locally thus reducing

transmission/distribution losses (transmission losses are approximately 7.2% in

mostsystems).

7. Once the initial capital cost of building a solar power plant has been spent,

operating costs are extremely low compared to existing power technologies.

Disadvantages of solar electricity

2. Solar electricity is almost always more expensive than electricity generated

by other sources.

3. Solar electricity is not available at night and is less available in cloudy weather

conditions

and therefore, a storage or complementary power system is required.

4. Limited power density: Average daily isolation in the contiguous Kenya is 3-

7kW·h/m² and on average lower in Europe where isolation is lower annually.

5. Solar cells produce DC which must be converted to AC (using a grid tie

inverter) when used in currently existing distribution grids. This incurs an

energy loss of 4-12%.

26

CHAPTER: 6

SCOPE OF IMPROVEMENT

6.1: Future Work and Recommendations

The goals of this project were purposely kept within what was believed to be

attainable within the allotted timeline and resources. As such, many improvements

can be made upon this initial design. That being said, it is felt that this design

represents a functioning miniature scale model which could be replicated to a

much larger scale. The following recommendations are provided

as ideas for future expansion of this project:

Remedy the motor binding problems due to the photo sensor leads. This could be

done with some use of easy to bend cables which don’t necessarily exert any force

on the motor when it is turning the solar panel. Alternatively, a smaller gauge wire,

a larger motor with more torque, or a combination of some or all of these ideas.

Increase the sensitivity and accuracy of tracking by using a different light sensor. A

photo transistor with an amplification circuit would provide improved resolution

and a better tracking accuracy/precision. Use of components used. Utilize a dual-

axis design versus a single-axis to increase tracking accuracy. Future solar project

should use a microcontroller which can be used as a standalone unit in the

fabricated circuit without the use of the programmer kit

27

CHPATER: 7

Conclusion

This project has presented a means of controlling a sun tracking array with an

embedded microcontroller system. Specifically, it demonstrates a working

software solution for maximizing solar cell output by positioning a solar array at the

point of maximum light intensity. This project presents a method of searching for

and tracking the sun and resetting itself for a new day. While the project has

limitations, particularly in hardware areas discussed in Chapter 3 and Chapter 4,

this provides an opportunity for expansion of the current project in future years

REFERENCES

[1] A.K. Saxena and V. Dutta, “A versatile microprocessor based controller for solar

tracking,” in Proc. IEEE, 1990, pp. 1105 – 1109.

[2] T.A. Papalias and M. Wong, “Making sense of light sensors,”

http://www.embedded.com, 2006.

[3] R. Condit and D. W. Jones, “Simple DC motor fundamentals,” Texas Instruments.

Publication AN907, pp. 1 – 22, 2004.

[4] Texas Instruments., “MSP430G2553 Datasheet,” www.ti.com, 2001

[5] “Fabrication of Dual-Axis Solar Tracking Controller Project”, Nader Barsoum,

Curtin

University, Sarawak, Malaysia, Intelligent Control and Automation, 2011, 2, 57-68.

ABBREVIATIONS AND ACRONYMS

ADC Analog to Digital Converter

EEPROM Electrical Erasable programmable Read Only Memory

D Diode

DC Direct current

GND Ground

I Current

I/O Input/ Output

IDE Integrated Development Environment

LDR Light Dependent Resistor

LED Light Emitting Diode

LUX Luminous Flux

LED Light Emitting Diode

MAX Maximum

28

MCU Microcontroller

MIN Minimum

VCC Supply voltage

UV Ultra Violet Light

PCB Printed Circuit Board

PV Photovoltaic panels

R Resistor

GaAs gallium arsenide

29

APPENDIX: LIST OF COMPONENTS USED AND ESTIMATED COST

COMPONETNTS COST(in Rs) MSP430G2553 200

L293D 50 POTENTIOMETER 20

LM7805 10 AMS1117-3.3V 20

CAPACETOR 10µF 2

RESISTOR 47KΩ 1 DC BATTERY 9V 20

SCREW TERMINAL (mo2) 5 JUMPER WIRES 25

LDR 20

SINGLE STAND WIRES 20 DC MOTER 150

TOTAL

543

30

APPENDIX: code used in the microcontroller

#include "msp430.h"

#define ADC_CHANNELS 2

unsigned int samples[ADC_CHANNELS];

#define LED1 BIT4

#define LED2 BIT6

#define SENSOR_LEFT BIT0

#define SENSOR_GND BIT2

#define SENSOR_RIGHT BIT1

#define SENSOR_GND1 BIT3

#define RED_LED LED1

#define GRN_LED LED2

void ConfigureAdc(void){

ADC10CTL1 = INCH_1 | ADC10DIV_0 | CONSEQ_3 | SHS_0;

ADC10CTL0 = SREF_0 | ADC10SHT_2 | MSC | ADC10ON | ADC10IE;

ADC10AE0 =SENSOR_LEFT + SENSOR_RIGHT ;

ADC10DTC1 = ADC_CHANNELS;

}

void main(void) {

WDTCTL = WDTPW | WDTHOLD;

30

BCSCTL1 = CALBC1_1MHZ;

DCOCTL = CALDCO_1MHZ;

BCSCTL2 &= ~(DIVS_3);

P1DIR = 0; /* set as inputs */

P1SEL = 0; /* set as digital I/Os */

P1OUT = 0; /* set resistors as pull-downs */

P1REN = 0xFF; /* enable pull-down resistors */

P2DIR = 0; /* set as inputs */

P2SEL = 0; /* set as digital I/Os */

P2OUT = 0; /* set resistors as pull-downs */

P2REN = 0xFF; /* enable pull-down resistors */

P1REN &= ~(LED1 | LED2); /* disable pull-up/downs */

P1DIR |= (LED1 | LED2); /* configure as outputs */

31

P1REN &= ~(SENSOR_GND |SENSOR_GND1); /* disable pull-up/down */

P1OUT &= ~(SENSOR_GND|SENSOR_GND); /* SENSOR_GND should be at

GND

*/

P1DIR |= (SENSOR_GND |SENSOR_GND1); /* SENSOR_GND must be an

output

*/

P1REN |= (SENSOR_LEFT|SENSOR_RIGHT); /* enable pull-up on SENSOR */

P1IN |= (SENSOR_LEFT|SENSOR_RIGHT); /* set resistor as pull-up */

ConfigureAdc();

__enable_interrupt();

while (1) {

__delay_cycles(1000);

ADC10CTL0 &= ~ENC;

while (ADC10CTL1 & BUSY);

ADC10SA = (unsigned int)samples;

ADC10CTL0 |= ENC + ADC10SC;

__bis_SR_register(CPUOFF + GIE);

if (samples[0] < samples[1]) {

P1OUT |=RED_LED;

P1OUT &= ~(GRN_LED);

} else if (samples[0] == samples[1]) {

P1OUT &= ~(RED_LED);

P1OUT &= ~(GRN_LED);

} else {

P1OUT |= GRN_LED;

P1OUT &= ~(RED_LED);

}

}

#pragma vector=ADC10_VECTOR

__interrupt void ADC10_ISR (void){

__bic_SR_register_on_exit(CPUOFF);

}