INTRODUCTION

One of the most promising renewable energy sources characterized by a huge potential of

conversion into electrical power is the solar energy. The conversion of solar radiation into

electrical energy by Photo-Voltaic (PV) effect is a very promising technology, being clean,

silent and reliable, with very small maintenance costs and small ecological impact. The

interest in the Photo Voltaic conversion systems is visibly reflected by the exponential

increase of sales in this market segment with a strong growth projection for the next

decades. According to recent market research reports carried out by European Photovoltaic

Industry Association (EPIA), the total installed power of PV conversion equipment

increased from about 1 GW in 2001up to nearly 23 GW in 2009.

The continuous evolution of the technology determined a sustained increase of the

conversion efficiency of PV panels, but nonetheless the most part of the commercial panels

have efficiencies no more than 20%. A constant research preoccupation of the technical

community involved in the solar energy harnessing technology refers to various solutions to

increase the PV panel’s conversion efficiency. Among PV efficiency improving solutions we

can mention: solar tracking, optimization of solar cells geometry, enhancement of light

trapping capability, use of new materials, etc. The output power produced by the PV panels

depends strongly on the incident light radiation.

The continuous modification of the sun-earth relative position determines a continuously

changing of incident radiation on a fixed PV panel. The point of maximum received energy

is reached when the direction of solar radiation is perpendicular on the panel surface. Thus

an increase of the output energy of a given PV panel can be obtained by mounting the panel

on a solar tracking device that follows the sun trajectory. Unlike the classical fixed PV

panels, the mobile ones driven by solar trackers are kept under optimum insolation for all

positions of the Sun, boosting thus the PV conversion efficiency of the system. The output

energy of PV panels equipped with solar trackers may increase with tens of percents,

especially during the summer when the energy harnessed from the sun is more important.

Photo-Voltaic or PV cells, known commonly as solar cells, convert the energy from sunlight

into DC electricity. PVs offer added advantages over other renewable energy sources in

that they give off no noise and require practically no maintenance. A tracking system must

be able to follow the sun with a certain degree of accuracy, return the collector to its

original position at the end of the day and also track during periods of cloud over.

The major components of this system are as follows.

Light dependent resistor

Microcontroller.

Output mechanical transducer (stepper motor)

Background:

A Solar Tracker is a device onto which solar panels are fitted which tracks the motion of the

sun across the sky ensuring that the maximum amount of sunlight strikes the panels

throughout the day. The Solar Tracker will attempt to navigate to the best angle of exposure

of light from the sun. This report aims to let the reader understand the project work which I

have done. A brief introduction to Solar Panel and Solar Tracker is explained in the

Literature Research section. Basically the Solar Tracker is divided into two main

categories, hardware and software. It is further subdivided into six main functionalities:

Method of Tracker Mount, Drives, Sensors, RTC, Motors, and Power Supply of the Solar

Tracker is also explained and explored. The reader would then be brief with some analysis

and perceptions of the information.

By using solar arrays, a series of solar cells electrically connected, a DC voltage is

generated which can be physically used on a load. Solar arrays or panels are being used

increasingly as efficiencies reach higher levels, and are especially popular in remote areas

where placement of electricity lines is not economically viable. This alternative power

source is continuously achieving greater popularity especially since the realisation of fossil

fuels shortcomings. Renewable energy in the form of electricity has been in use to some

degree as long as 75 or 100 years ago. Sources such as Solar, Wind, Hydro and

Geothermal have all been utilised with varying levels of success. The most widely used are

hydro and wind power, with solar power being moderately used worldwide. This can be

attributed to the relatively high cost of solar cells and their low conversion efficiency. Solar

power is being heavily researched, and solar energy costs have now reached within a few

cents per kW/h of other forms of electricity generation, and will drop further with new

technologies such as titanium oxide cells. With a peak laboratory efficiency of 32% and

average efficiency of 15-20%, it is necessary to recover as much energy as possible from a

solar power system. This includes reducing inverter losses, storage losses, and light

gathering losses. Light gathering is dependent on the angle of incidence of the light source

providing power (i.e. the sun) to the solar cell’s surface, and the closer to perpendicular,

the greater the power. If a flat solar panel is mounted on level ground, it is obvious that

over the course of the day the sunlight will have an angle of incidence close to 90° in the

morning and the evening. At such an angle, the light gathering ability of the cell is

essentially zero, resulting in no output. As the day progresses to midday, the angle of

incidence approaches 0°, causing a steady increase in power until at the point where the

light incident on the panel is completely perpendicular, and maximum power is achieved. As

the day continues toward dusk, the reverse happens, and the increasing angle causes the

power to decrease again toward minimum again. From this background, we see the need to

maintain the maximum power output from the panel by maintaining an angle of incidence as

close to 0° as possible. By tilting the solar panel to continuously face the sun, this can be

achieved. This process of sensing and following the position of the sun is known as Solar

Tracking. It was resolved that real-time tracking would be necessary to follow the sun

effectively, so that no external data would be required in operation.

S O LAR P O WER IN INDIA:

In July 2009, India unveiled a US$19 billion plan to produce 20 GW

(20,000MW) of solar power by 2020. Under the plan, the use of solar-powered

equipment and applications would be made compulsory in all government buildings, as

well as hospitals and hotels. On November 18, 2009, it was reported that India was

ready to launch its National Solar Mission under the National Action Plan on Climate

Change, with plans to generate 1,000 MW of power by

2013.

India's l argest p hotovol taic (PV) p ower pla nts

1. Reliance Power Pokaran Solar PV Plant, Rajasthan, 40MW 02011-06

June 2011 Commissioning in March 2012

2. AdaniBitta Solar Plant, Gujarat, 40MW 02011-06 June 2011 To be

Completed December 2011

3. Moser Baer - Patan, Gujarat,30MW 02011-06 June 2011 Commissioned

July 2011

4. Azure Power - Sabarkantha, Gujarat, 10MW 02011-06 June

2011 Commissioned June 2011

Technology of Solar Panel:

Solar panels are devices that convert light into electricity. They are called solar after the

sun because the sun is the most powerful source of the light available for use. They are

sometimes called photovoltaic which means "light-electricity". Solar cells or PV cells rely

on the photovoltaic effect to absorb the energy of the sun and cause current to flow between

two oppositely charge layers. A solar panel is a collection of solar cells. Although each

solar cell provides a relatively small amount of power, many solar cells spread over a large

area can provide enough power to be useful. To get the most power, solar panels have to be

pointed directly at the Sun. The development of solar cell technology begins with 1839

research of French physicist Antoine-Cesar Becquerel. He observed the photovoltaic effect

while experimenting with a solid electrode in an electrolyte solution. After that he saw a

voltage developed when light fell upon the electrode.

According to Encyclopaedia Britannica the first genuine for solar panel was built around

1883 by Charles Fritts. He used junctions formed by coating selenium (a semiconductor)

with an extremely thin layer of gold. Crystalline silicon and gallium arsenide are typical

choices of materials for solar panels. Gallium arsenide crystals are grown especially for

photovoltaic use, but silicon crystals are available in less-expensive standard ingots, which

are produced mainly for consumption in the microelectronics industry. Norway’s

Renewable Energy Corporation has confirmed that it will build a solar manufacturing plant

in Singapore by 2010 - the largest in the world. This plant will be able to produce products

that can generate up to 1.5 Giga watts of energy every year. That is enough to power

several million households at any one time. Last year the world as a whole produced

products that could generate just 2 GW in total.

Evolution of Solar Tracker:

Since the sun moves across the sky

throughout the day, in order to receive the

best angle of exposure to sunlight for

collection energy. A tracking mechanism is

often incorporated into the solar arrays to

keep the array pointed towards the sun. A solar tracker is a device onto which solar panels

are fitted which tracks the motion of the sun across the sky ensuring that the maximum

amount of sunlight strikes the panels throughout the day. When compare to the price of the

PV solar panels, the cost of a solar tracker is relatively low. Most photovoltaic solar panels

are fitted in a fixed location- for example on the sloping roof of a house, or on framework

fixed to the ground. Since the sun moves across the sky though the day, this is far from an

ideal solution. Solar panels are usually set up to be in full direct sunshine at the middle of

the day facing South in the Northern Hemisphere, or North in the Southern Hemisphere.

Therefore morning and evening sunlight hits the panels at an acute angle reducing the total

amount of electricity which can be generated each day.

Fig 2.1 Sun’s apparent motion

During the day the sun appears to move across the sky from left to right and up and down

above the horizon from sunrise to noon to sunset. Figure 2.1 shows the schematic above of

the Sun's apparent motion as seen from the Northern Hemisphere. To keep up with other

green energies, the solar cell market has to be as efficient as possible in order not to lose

market shares on the global energy marketplace. The end-user will prefer the tracking

solution rather than a fixed ground system to increase their earnings because:

The efficiency increases by 30-40%.

The space requirement for a solar park is reduced, and they keep the same

output.

The return of the investment timeline is reduced.

The tracking system amortizes itself within 4 years.

In terms of cost per Watt of the completed solar system, it is usually cheaper

to use a solar tracker and less solar panels where space and planning

permit.

A good solar tracker can typically lead to an increase in electricity

generation capacity of 30-50%.

Project Description:

Schematic Diagram:

TYPES OF SOLAR TRACKERS

PASSIVE TRACKING SYSTEMS:

The passive tracking system realizes the movement of the system by utilizing a low boiling point liquid. This liquid is vaporized by the added heat of the sun and the center of mass is shifted leading to that the system finds the new equilibrium position.

ACTIVE TRACKING SYSTEMS:

The two basic types of active solar tracker are single-axis and double-axis

Si ngl e a xis trackers:

The single axis tracking systems realizes the movement of either elevation or azimuth for a

solar power system. Which one of these movements is desired, depends on the technology used

on the tracker as well as the space that it is mounted on. For example the parabolic through

systems utilize the azimuthally tracking whereas the many rooftop PV-systems utilize elevation

tracking because of the lack of space. A single-axis tracker can only pivot in one plane –

either horizontally or vertically. This makes it less complicated and generally cheaper than a

two-axis tracker, but also less effective at harvesting the total solar energy available at a site.

Trackers use motors and gear trains to direct the tracker as commanded by a controller

responding to the solar direction. Since the motors consume energy, one wants to use them

only as necessary.

Single axis trackers have one degree of freedom that acts as an axis of rotation. There are several common implementations of single axis trackers. These include horizontal single axis trackers (HSAT) and vertical single axis trackers (VSAT).

A horizontal-axis tracker consists of a long horizontal tube to which solar modules are attached. The tube is aligned in a north-south direction, is supported on bearings mounted on pylons or frames, and rotates slowly on its axis to follow the sun's motion across the sky. This kind of tracker is most effective at equatorial latitudes where the sun is more or less overhead at noon. In general, it is effective wherever the solar path is high in the sky for substantial parts of the year, but for this very reason, does not perform well at higher latitudes. For higher latitude, a vertical-axis tracker is better suited. This works well wherever the sun is typically lower in the sky and, at least in the summer months, the days are long.

Dua l Axis Trackers:

Dual axis trackers as shown in the figure 2.6 have two degrees of freedom that act as axes of rotation. Double-axis solar trackers, as the same suggest, can rotate simultaneously in horizontal and vertical directions, and so are able to point exactly at the sun at all times in any location.

Dual axis tracking systems realize movement both along the elevation- and azimuthally axes. These tracking systems naturally provide the best performance, given that the components have high enough accuracy as well.

Fig2.6 Dual axis solar tracker

TRACKER DESIGN:

A solar tracker is a device that orient photovoltaic array toward the sun. In flat-panel photovoltaic (PV) applications trackers are used to minimize the angle of incidence between the incoming light and a photovoltaic panel. This increases the amount of energy produced by the photovoltaic array.

Here we can use azimuth-altitude dual axis trackers (AADAT). Dual axis trackers extract the maximum solar energy levels due to their ability to follow the sun vertically and horizontally. No matter where the sun is in the sky, dual axis trackers are able to angle themselves to be in direction toward the sun.

The Fig. 3.1 shows a setup of a squared solar panel with two degrees of freedom. Here Two DC motors are used to drive the two rotational degrees of freedom. The motors can mounted directly on the rotation pins of the rotational joints to reduce losses caused by linkages and joints and to avoid using more linkages and mechanisms.

DC MOTOR AND MOTOR DRIVER THEORY:

Introduction: The tracking systems would need to consist of two motors, which control the position of the array, and a control circuit (either analog or digital) to direct these motors. The following sections discuss some possible types of motors that could be used for this type of application.

DC Motors:

Inner Workings of a DC Motor

Figure shows the inner workings of a basic DC motor. The outside section of the motor is the stator (stationary part), while the inside section is the rotor (rotating part).The stator is comprised of two (or more) permanent magnet pole pairs, while the rotor is comprised of windings that are connected to a mechanical commutator. The opposite polarities of the energized winding and the stator magnet attract each other. When this occurs the rotor will rotate until perfect alignment with the stator is achieved. When the rotor reaches alignment, the brushes move across the commutator contacts (middle section of rotor) and energies the next winding.

There are two other types of DC motors: series wound and shunt wound. These motors also use a similar rotor with brushes and a commutator. However, the stator uses windings instead of permanent magnets. The basic principle is still the same. A series wound DC motor has the stator windings in series with the rotor. A shunt wound DC motor has the stator windings in parallel with the rotor winding.

DC Servomotors:

By itself the standard DC motor is not an acceptable method of controlling a sun tracking array. This is due to the fact that DC motors are free spinning and subsequently difficult to position accurately. Even if the timing for starting and

stopping the motor is correctly achieved, the armature does not stop immediately. DC motors have a very gradual acceleration and deceleration curves, therefore stabilization is slow. Adding gearing to the motor will help to reduce this problem, but overshoot is still present and will throw off the anticipated stop position.

The only way to effectively use a DC motor for precise positioning is to use a servo.

The servomotor is actually an assembly of four things: a normal DC motor, a gear reduction unit, a position-sensing device (usually a potentiometer), and a control circuit. The function of the servo is to receive a control signal that represents a

desired output position of the servo shaft, and apply power to its DC motor until its shaft turns to that position. It uses the position-sensing device to determine the rotational position of the shaft, so it knows which way the motor must turn to move the shaft to the command position. The solar panel that attached to the motor will be reacted according to the direction of the motor.

SENSORS:

We are using Five Light Dependent Resistor’s as a sensor. They sense the higher density area of sun light. The solar panel moves to the high light density area through servo motors.

Each LDR is connected to power supply forming a potential devider. Thus any change in light density is proportional to the change in voltage across the LDR’s.

LDR is a passive transducer hence we will use potential divider circuit to obtain corresponding voltage value from the resistance of LDR.

LDRs resistance is inversely proportional to the intensity of light falling on it i.e. Higher the intensity or brightness of light the Lower the resistance and vice versa. Interfaces.

Input(ADC):

Arduino has an inbuilt 10-bit Analog to Digital converter(ADC), hence it can provide Digital values from 0-1023.(since 2^10=1024). We can also set the ADC reference voltage in arduino, but here we’ll let it use default value. LDR’s has two pins, and to get voltage value from it we use potential divider circuit. In potential divider we get Vout corresponding to resistance of LDR which in turn is a function of Light falling on LDR. The higher the intensity of light, lower the LDR resistance and hence lower the Output voltage (Vout) And lower the light intensity, higher the LDR resistance and hence higher the Vout.

Output(PWM):

Arduino has a 8-bit PWM generator, so we can get up to 256 distinct PWM signal. To drive a servo we need to get a PWM signal from the board, this is usually accomplished using timer function of the microcontroller but arduino makes it very easy. Arduino provides a servo library in which we have to only assign servo angle (0-1800) and the servo rotates by that angle, all the PWM calculations are handled by the servo library and we get a neat

M ICRO C O NT R O L L ER:

The ATMEGA-168 is a modified Harvard architecture 8-bit RISC single chip

microcontroller which was developed by Atmel. It uses on-chip flash memory for program

storage, as opposed to one-time programmable ROM, EPROM, or EEPROM used

by other microcontrollers at the time.

Feature s : - Flash : 16KB

EEPROM : 1024B

SRAM : 512B

Clock freq. : upto 20MHz

Supply voltage : 2.8-5.5v

Ext. Interrupt : 24

PWM : 6

Pin desc riptions:

VCC

Digital supply voltage

GND

Ground

Port B (PB7:0) XTAL1/XTAL2/TOSC1/TOSC2

Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,even if the clock is not running. Depending on the clock selection fuse settings, PB6 can be used as input to the inverting Oscillator amplifier and input to the internal clock operating circuit. Depending on the clock selection fuse settings, PB7 can be used as output from the inverting Oscillator amplifier. If the Internal Calibrated RC Oscillator is used as chip clock source, PB7.6 is used as TOSC2.1 input for the Asynchronous Timer/Counter2 if the AS2 bit in ASSR is set.

Port C (PC5:0)

Port C is a 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The PC5..0 output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running.

PC6/RESET

If the RSTDISBL Fuse is programmed, PC6 is used as an I/O pin. Note that the electrical characteristics of PC6 differ from those of the other pins of Port C. If the RSTDISBL Fuse is unprogrammed, PC6 is used as a Reset input. A low level on this pin for longer than the minimum pulse length will generate a Reset, even if the clock is not running.

Port D (PD7:0)

Port D is an 8-bit bi-directional I/O port with internal pull-up resistors(selected for each bit). The Port D output buffers have symmetrical drive characteristics with both high sink and source capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up resistors are activated. The Port D pins are tri-stated when a reset condition becomes active, even if the clock is not running.

AVCCAVCC is the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6. It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter. Note that PC6.4 use digital supply voltage, VCC.

AREFAREF is the analog reference pin for the A/D Converter.

ADC7:6 (TQFP and QFN/MLF package only)

In the TQFP and QFN/MLF package, ADC7.6 serve as analog inputs to the

A/D converter. These pins are powered from the analog supply and serve as

10-bit ADC channels.

CONCLUSION

From the design of experimental set up with Micro Controller Based Solar

Tracking System Using Stepper Motor If we compare Tracking by the use of

LDR with Fixed Solar Panel System we found that the efficiency of Micro

Controller Based Solar Tracking System is improved by 30-45% and it was

found that all the parts of the experimental setup are giving good results. The

required Power is used to run the motor by using Step-Down T/F by using

220V AC. Moreover, this tracking system does track the sun in a continuous

manner. And this system is more efficient and cost effective in long run. From

the results it is found that, by automatic tracking system, there is 30 % gain in

increase of efficiency when compared with non-tracking system. The solar

tracker can be still enhanced additional features like rain protection and wind

protection which can be done as future work.

REFERENCES

[1] Rizk J. and Chaiko Y. “Solar Tracking System: More Efficient Use of Solar

Panels”, World Academy of Science, Engineering and Technology 41

2008.

[2] Filfil Ahmed Nasir, Mohussen Deia Halboot, Dr. Zidan Khamis A.

“Microcontroller-Based Sun Path Tracking System”, Eng. & Tech. Journal,

Vol. 29, No.7, 2011.

[3] Alimazidi Mohammad, Gillispie J, Mazidi, Rolin D. McKinlay, “The 8051

Microcontroller and Embedded Systems”, An imprint of Pearson Education.

[4] Mehta V K, Mehta Rohit, “Principles of Electronics”, S. Chand &

Company Ltd.

[5] Balagurusamy E, “Programming in ANSI C”, Tata McGraw-Hill

Publishing Company Limited.

[6] Damm, J. Issue #17, June/July 1990. An active solar tracking system,

Home Brew Magazine.

[7] Koyuncu B and Balasubramanian K, “A microprocessor controlled

automatic sun tracker,” IEEE Trans. Consumer Electron., vol. 37, no. 4,pp.

913-917, 1991.

[8] Konar A and Mandal A K, “Microprocessor based automatic sun tracker,”

IEE Proc. Sci., Meas. Technol., vol. 138, no. 4, pp. 237-241,1991.

SOLAR TRACKING SYSTEM USING A UNIQUE CONTROL UNIT

A project Report Submitted

in Partial Fulfilment of the Requirements

for the Degree of

Bachelor of Technology

in

Electrical Engineering

by

Ashutosh Mohanty(120101022) Subham Hazra(120101077) Sourav Kumar Dey(120101074) Joydeep Sarkar(120101034) Suprakash Ghosh Anasua Das(120101009) Puja Roy(120101050) Neha Das(120101044)

Under the Supervision of

Assist. Prof. Suparna Pal

JIS COLLEGE OF ENGINEERING

to theFaculty of Electrical Engineering

ACKNOWLEDGEMENT

I would like to express my gratitude to Mrs. Suparna Pal, Asstt. Prof.

EE, JISCE for guidance and support throughout this project work. She has

been a constant source of inspiration to me throughout the period of

this work. We consider ourselves extremely fortunate for having the

opportunity to learn and work under her supervision over the entire period.

ABSTRACT

Solar energy is rapidly gaining notoriety as an important means of

expanding renewable energy resources. As such, it is vital that those

in engineering fields understand the technologies associated with this

area. Our project will include the design and construction of a

microcontroller-based solar panel tracking system. Solar tracking allows

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

aligned to the sun. This system builds upon topics learned in this course.

A working system will ultimately be demonstrated to validate the design.

Problems and possible improvements will also be presented.