Thesis Microcontroller Based Single Axis Solar Tracker

MICROCONTROLLER BASED SINGLE AXIS SOLAR TRACKER Prepared by

Sl

Name

ID. No.

1

Ms. Rehana Akter

ID: 102-296-511

2

Mir Md Emam Uddin

ID: 102-168-511

3

Md. Jamil Uddin

ID: 102-085-511

4

Md. Mahbub Mehedi

ID: 102-049-511

5

MD. Shariful Amran

ID: 102-102-511

A thesis submitted in partial fulfillment for the degree of B.sc. in

Electrical and Electronics Engineering

Course Code: EEE – 499

Atish Dipankar University of Science & Technology (ADUST) Department of Electrical & Electronic Engineering

MICROCONTROLLER BASED SINGLE AXIS SOLAR TRACKER

An internship report submitted to the department of EEE, Atish Dipankar University of Science and Technology for partial fulfillment of the degree of B.Sc. in Electrical and Electronic Engineering.

Submitted by:

Sl

Name

ID. No.

1

Ms. Rehana Akter

ID: 102-296-511

2

Mir Md Emam Uddin

ID: 102-168-511

3

Md. Jamil Uddin

ID: 102-085-511

4

Md. Mahabub Mehedi

ID: 102-049-511

5

MD. Shariful Amran

ID: 102-102-511

Supervised By:

Marzia Hoque Tania

Signature:

Lecturer

Date:

i

_______________

Department of Electrical & Electronic Engineering

CERTIFICATE This is to certify that the B.Sc. thesis entitled “Microcontroller based single axis solar tracker” submitted by this group (Ms. Rehana Akter, ID No: 102296-511. Mir Imam Uddin, ID No: 102-168-511. Md Jamil Uddin, ID No: 102085-511. Md. Mahbub Mehedi, ID No: 102-049-511. Md Shariful Amran, ID No: 102 102-511) The thesis represents an independent and original work on the part of the candidates. The research work has not previously formed the basis for the award of any degree, diploma, fellowship or any other discipline.

The whole work of this thesis has been planned and carried out by this group under supervision and guidance of the faculty members of Atish Dipankar University of Science & Technology, Dhaka, Bangladesh.

____________________ Marzia Hoque Tania Lecturer Department of EEE

ii

ABSTRACT The work we present is a microcontroller based single axis solar tracking device which enables the solar panel. To face with the sunlight to increase the output of the solar PV systems. It is an automatic tracking device which aims to maximize in harvesting solar power. When the intensity of the light, decries, the system automatically changes its direction to get the maximize intensity of sunlight. Light depended resisters are used as sensor. Data received by the sensors is processed by the microcontroller. Signal from the microcontroller in send to the DC gear motor. The clockwise and anticlockwise rotation of the motor is conducted by the relays. This prototype might be implemented is residential uses. Due to low power consumption this prototype would be very hungry is real life application. Keywords: Solar tracking, solar tracker, microcontroller, DC motor, LDR.

iii

ACKNOWLEDGEMENT

At first we would like to thank our supervisor, Marzia Hoque Tania, Lecturer, ADUST. for giving us the opportunity to work under his supervision, the endless hours of help, suggestions, advice and support to keep us on track during the development of this thesis.

Last, but not least, we would like to thank our parents and family for making it possible for us to study and for their constant help and support.

The Authors Dhaka

iv

DEDICATION

To Almighty ALLAH and Our Respective Parents

v

Table of Contents Abstract ………………………………………………………………………... iii Acknowledgement …………………………………………………………… iv Dedication ……………………………………………………………………..

v

Figure …………………………………………………………………………... x-xii Table ……………………………………………………………………………. xiii Chapter- 1: Introduction and overview ………………………..

01-09

1.1. Renewable energy ………………………………………………………..

01

1.2. Use of Renewable Energy ……………………………………………....

02-03

1.3. Types of renewable energy ……………………………………………… 03 1.3.1 Solar energy ……………………………………………………………..

03

1.3.2 Wind energy ……………………………………………………………..

03

1.3.3 Geothermal energy ……………………………………………………..

04

1.3.4 Bio energy ……………………………………………………………….. 04 1.3.5 Hydropower ……………………………………………………………...

05

1.3.6 Ocean energy ……………………………………………………………

06

1.3.7 Hydrogen energy ………………………………………………………..

06

1.4 Importance of renewable energy ………………………………………..

07

1.4.1 Environmental Benefits ………………………………………………..

07

1.4.2 Energy for our children's ……………………………………………….

07

1.4.3 Jobs and the Economy …………………………………………………

07-08

1.4.4 Energy Security …………………………………………………………

08

1.5 Necessary of solar tracker ……………………………………………….

08

1.6 Global technical potential of solar energy ………………………………

08-09

Chapter-2: Solar photovoltaic (PV) system …………………..

09-16

2.1 Photovoltaic (PV) system ………………………………………………… 10 2.2 Work of solar photovoltaic (PV) system ………………………………... 11-12

vi

2.3 Types of photovoltaic (PV) systems …………………………………….

11-12

2.3.1 Single-crystalline or mono crystalline …………………………………

12

2.3.2 Polycrystalline cells …………………………………………………….

13

2.3.4 Amorphous Silicon ……………………………………………………… 13 2.4 Components of a solar photovoltaic (PV) ………………………………

14

2.4.1 Charge controller ………………………………………………………..

14

2.4.2 Batteries ………………………………………………………………….

15

2.4.3 Inverter …………………………………………………………………… 15 2.5 Advantages of photovoltaic (PV) ………………………………………...

15-16

2.6 Disadvantage of photovoltaic (PV) ………………………………………

16

2.7 Photovoltaic (PV) applications and market ……………………………..

16

Chapter-3: Solar path of the sun ……………………………….

17-25

3.1 Basic of solar radiation ……………………………………………………

17

3.2 Solar Constant and "Sun Value" ……………………………………….

17

3.3 Extraterrestrial and Terrestrial Spectra………………………………….

18

3.3.1 Extraterrestrial Spectra …………………………………………………

18

3.3.2 Terrestrial Spectra ………………………………………………………

18-19

3.4 The Changing Terrestrial Solar Spectrum ……………………………...

19-20

3.5 Standard Spectra ………………………………………………………….

20-23

3.6 Geometry of Solar Radiation …………………………………………….. 23 3.7 Dirunal and Annual Variation ……………………………………………. 24 3.8 Solar Motion ……………………………………………………………….. 25 Chapter-4: Solar tracking system ………………………........... 26-33 4.1 Solar tracker ……………………………………………………………….

27

4.2 Types of solar tracker …………………………………………………….

27

4.2.1 Single axis solar tracker ………………………………………………..

28

4.2.1.1 Types of single axis solar tracker …………………………………...

28

vii

4.2.1.2 Horizontal single axis tracker (HSAT) ……………………….

28-29

4.2.1.3 Vertical single axis tracker (VSAT) …………………………..

29

4.2.1.4 Tilted single axis tracker (TSAT) …………………………….

30

4.2.1.5 Polar aligned single axis trackers (PASAT) …………………

30-31

4.2.2 Dual axis solar tracker …………………………………………………. 4.2.2.1 Types of duel axis solar tracker …………………………………….

4.2.2.2 Tip–tilt dual axis tracker ………………………………………. 4.2.2.3 Azimuth-altitude dual axis tracker (AADAT) ………………...

31 32 32 33

Chapter-5: Construction of microcontroller based single

axis solar tracker ……………………………………………….

34-52

5.1 Single axis solar trackers ………………………………………………...

34

5.2 Mechanical System ……………………………………………………….

35

5.3 Methodology ……………………………………………………………….

35-38

5.4 Working principle ………………………………………………………….

39

5.5 Description of the component ……………………………………………

39

5.5.1 Microcontroller …………………………………………………………..

39

5.5.1.1 Use of microcontroller ………………………………………………..

39-40

5.5.2 Gear-motor ………………………………………………………………

44

5.5.2.1 Gear-motor Benefits ………………………………………………….

44

5.5.2.2 Application of Gear-motor …………………………………………...

44

5.5.3 Voltage regulator ………………………………………………………..

45

5.5.4 Definition of relay ………………………………………………………

45

5.5.4.1 Types of relay …………………………………………………………

46

5.5.4.2 Application of relay …………………………………………………...

46

5.5.5 Resistor ……………………………………………………………….…

46-47

5.5.6 Capacitor ………………………………………………………………...

48

5.5.7 Transistor ………………………………………………………………..

48

5.5.7.1 Types of Transistor ……………………………………………..……

49

viii

5.5.8 Push button switch …………………………………………..…………

49

5.5.9 Oscillator …………………………………………………………………

50

5.5.9.1 Application of oscillators ……………………………………………..

50

5.5.10 Light depended resistor (LDR) ………………………………………

51

5.5.10.1 Operation of LDR

51-52

Chapter-6: Conclusion ……………………………………………

53-55

6.1 Accuracy requirements.…………………………………………………..

53

6.2 Advantages of solar tracker ……………………………………………...

54-55

6.3 Scope of future work of solar trackers ………………………………….

55

Summary …………………………………………………………

56

Reference ………………………………………………………...

57

ix

Figure Figure 1.1 solar energy ……………………………………………………….

03

Figure 1.2 wind energy ……………………………………………………….

04

Figure 1.3 Geothermal energy ……………………………………………….

04

Figure 1.4 Bio-energy …………………………………………………………

05

Figure 1.5 Hydropower energy ………………………………………………

05

Figure 1.6 Ocean energy ……………………………………………………..

06

Figure 1.7 Hydrogen energy …………………………………………………

07

Figure 2.1 Solar photovoltaic (V) system …………………………………...

11

Figure 2.2 Single-crystalline or mono crystalline …………………………..

12

Figure 2.3 Multi- or poly-crystalline ………………………………………….

13

Figure 2.4 Amorphous silicon ………………………………………………..

13

Figure 2.5 Block diagram of a typical solar PV system ……………………

14

Figure: 3.1 Spectrum of the radiation outside the earth’s atmosphere compared to spectrum of a 5800 K blackbody…………………………….

17

Figure: 3.2 The total global radiation on the ground has direct, scattered and reflective components……………………………………………………

19

Figure: 3.3 Normally incident solar spectrum at sea level on a clear day. The dotted curve shows the extrarrestrial spectrum………………………

19

Figure: 3.4 The path length in units of Air Mass, changes with the zenith Angle …………………………………………………………………………..

20

Figure: 3.5 Standard spectra …………………………………………………

21

Figure: 3.6 Actual scan of a simulator with resolute on under 2 nm; high resolution doesn’t enhance these Doppler broadened lines. Middle: Scan of same simulator with 10 nm resolution. Bottom: Smoothed

x

version of top curve. We used repeated Savitsky-Golay smoothing …….

22

Figure: 3.7 Comparison of the UV portion of the WMO measured solar spectrum and the modeled CIE AM 1 direct spectrum. All the modeled spectra, CIE or ASTM, used as standards, omit the fine details seen in measured spectrum……………………………………………………………

23

Figure: 3.8 The solar disk subtends a 1/2° angle at the earth ……………

23

Figure: 3.9 Diurnal variations of global solar radiative flux on a sunny day………………………………………………………………………………

24

Figure: 3.10 Diurnal variations of global solar radiative flux on a cloudy day……………………………………………………………………………….. 24 Figure: 3.11 The global solar irradiance at solar noon measured in Arizona, showing the annual variation……………………………………….

25

Figure: 3.12 Solar Motion …………………………………………………….

25

Figure 4.1 PV array fixed tilt ………………………………………………….

26

Figure 4.2 Single axis tracking system ……………………………………...

27

Figure 4.3 Dual axis tracking system ………………………………………..

27

Figure 4.4 Single axis solar tracker ………………………………………….

28

Figure: 4.5 Horizontal single axis trackers ……………………………

29

Figure: 4.6 Vertical single axis trackers ………………………………. Figure: 4.7 Tilted single axis trackers ………………………………….

30

Figure: 4.8 Polar aligned single axis trackers ………………………...

31

Figure 4.9 Dual axis solar trackers ………………………………………….

31

Figure: 4.10 Tip–tilt dual axis trackers …………………………………

33

Figure: 4.11 Azimuth-altitude dual axis trackers ……………………..

33

Figure: 5.1 Final solar tracker prototypes …………………………………. Figure: 5.2 Block diagram of the project (single axis solar tracker)………

xi

30

34 36

Figure: 5.3 Flow chart of the project (single axis solar tracker)…………..

37

Figure: 5.4 Circuit diagram of the project (single axis solar tracker)……..

38

Figure: 5.5 Pin Diagram of Microcontroller (PIC 16F84A)…………………

40

Figure: 5.6 Block Diagram of microcontroller (PIC 16F84A)………………

42

Figure: 5.7 Gear-motor ……………………………………………………….

45

Figure: 5.8 Voltage regulator …………………………………………………

45

Figure: 5.9 Relay ………………………………………………………………

46

Figure: 5.10 Symbol of resistor ………………………………………………

47

Figure: 5.11 Picture of resistor ……………………………………………….

47

Figure: 5.12 Symble of capacitor …………………………………………….

48

Figure: 5.13 Picture of Capacitor …………………………………………….

48

Figure: 5.14 Symble of Transistor …………………………………………...

49

Figure: 5.15 Push button switch ……………………………………………..

50

Figure: 5.16 Circuit diagram of Oscillator …………………………………..

51

Figure: 5.17 Picture of LDR …………………………………………………..

52

xii

Table Table 2.1 Efficiency of different types of solar cell …………………………

14

Table: 3.1 Power Densities of Published Standards……………………….

21

Table: 5.1 Specification of solar tracking system …………………………..

35

Table: 5.2 List of Equipments ………………………………………………...

36

Table: 5.3 Description of pin number of Microcontroller (PIC 16F84A)…..

41

Table: 6.1 Accuracy direct powers lost ……………………………………...

54

xiii

Chapter-1

Introduction and overview Solar energy is being used as an alternative energy source years. But the efficiency of solar panel, battery and the overall system efficiency are point of concerns to use the solar PV system as means of power generation. The sunlight is sufficient enough to overcome the power crisis of the world but is till date it is not possible to capture and utilized the full range of the sun energy of the sunlight. This thesis book presents a solar tracking system to enhance the output power of a solar PV system. This project helps to increases the power generation by setting the equipment to get maximum sunlight automatically. This system is tracking the sunlight. When there is a decrease in the intensity of light, this system automatically changes its direction of the solar panel to get maximum intensity of sunlight. We are using three sensors in three directions to sense the direction of maximum intensity of sunlight. The difference between the outputs of the sensors is given to the microcontroller unit. Here we are using the microcontroller for tracking the sunlight. It will process the input voltage from the oscillator circuit and control the direction in which the motor has to be rotated so that it will receive maximum intensity of light from the sun. 1.1 Renewable Energy: Renewable energy uses energy sources that are continually replenished by nature—the sun, the wind, water, the Earth’s heat, and plants. Renewable Page 1 of 57

energy technologies turn these fuels into usable forms of energy—most often electricity, but also heat, chemicals, or mechanical power. 1.2 Use of Renewable Energy: Today we primarily use fossil fuels to heat and power our homes and fuel our cars. It’s convenient to use coal, oil, and natural gas for meeting our energy needs, but we have a limited supply of these fuels on the Earth. We’re using them much more rapidly than they are being created. Eventually, they will run out. And because of safety concerns and waste disposal problems, the United States will retire much of its nuclear capacity by 2020. In the meantime, the nation’s energy needs are expected to grow by 33 percent during the next 20 years. Renewable energy can help fill the gap. Even if we had an unlimited supply of fossil fuels, using renewable energy is better for the environment. We often call renewable energy technologies “clean” or “green” because they produce few if any pollutants. Burning fossil fuels, however, sends greenhouse gases into the atmosphere, trapping the sun’s heat and contributing to global warming. Climate scientists generally agree that the Earth’s average temperature has risen in the past century. If this trend continues, sea levels will rise, and scientists predict that floods, heat waves, droughts, and other extreme weather conditions could occur more often. Other pollutants are released into the air, soil, and water when fossil fuels are burned. These pollutants take a dramatic toll on the environment—and on humans. Air pollution contributes to diseases like asthma. Acid rain from sulfur dioxide and nitrogen oxides harms plants and fish. Nitrogen oxides also contribute to smog. Renewable energy will also help us develop energy independence and security. The United States imports more than 50 percent of its oil, up from 34 percent in 1973. Replacing some of our petroleum with fuels made from plant matter, for example, could save money and strengthen our energy security. Renewable energy is plentiful, and the technologies are improving all the time. There are Page 2 of 57

many ways to use renewable energy. Most of us already use renewable energy in our daily lives.

1.3 Types of renewable energy: 1.3.1 Solar energy: Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses.

Figure 1.1 Solar energy

1.3.2 Wind energy: We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent - a wind turbine - can use the wind's energy to generate electricity.

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Figure 1.2 Wind energy 1.3.3 Geothermal Energy: Geothermal energy is the heat from the Earth. It's clean and sustainable. Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.

Figure 1.3 Geothermal energy 1.3.4 Bio-energy: We have used biomass energy or bio-energy - the energy from organic matter for thousands of years, ever since people started burning wood to cook food or to keep warm. Even the fumes from landfills can be used as a biomass energy source. Page 4 of 57

Figure 1.4 Bio-energy 1.3.5 Hydropower: Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Some hydroelectric power plants just use a small canal to channel the river water through a turbine.

Figure 1.5 Hydropower energy

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1.3.6 Ocean energy: The Ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves. Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped in the ocean could power the world.

Figure 1.6 Ocean energy

1.3.7 Hydrogen energy: Hydrogen is the simplest element. An atom of hydrogen consists of only one proton and one electron. It's also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn't occur naturally as a gas on the Earth - it's always combined with other elements. Water, for example, is a combination of hydrogen and oxygen (H2O).

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Figure 1.7 Hydrogen energy

1.4 Importance of renewable energy: Renewable energy is important because of the benefits it provides. The key benefits are: 1.4.1 Environmental Benefits Renewable energy technologies are clean sources of energy that have a much lower environmental impact than conventional energy technologies. 1.4.2 Energy for our children's Renewable energy will not run out Ever. Other sources of energy are finite and will someday be depleted. 1.4.3 Jobs and the Economy Most renewable energy investments are spent on materials and workmanship to build and maintain the facilities, rather than on costly energy imports. Renewable energy investments are usually spent within the United States, frequently in the same state, and often in the same town. Meanwhile, renewable

Page 7 of 57

energy technologies developed and built in the United States are being sold overseas, providing a boost to the U.S. trade deficit. 1.4.4 Energy Security After the oil supply disruptions of the early 1970s, our nation has increased its dependence on foreign oil supplies instead of decreasing it. This increased dependence impacts more than just our national energy policy. 1.5 Necessary of solar tracker: Many standard PV systems in residential areas do not have solar trackers. For their purposes, having the stand-alone system is sufficient and meets the needs and goals of the customer. Whether solar trackers are beneficial and recommended is dependent on various factors, including weather, location, obstruction, and cost. In some cases, solar trackers can potentially make solar panels 25-35% more efficient, which means that more power can be generated with less space and less panels. However, if the location of the installation does not allow the trackers to work effectively, then the cost of purchasing the solar trackers can lead to money wasted. So, it’s important to discuss your goals with your installer and have them give you a full on-site analysis of your particular project. 1.6 Global technical potential of solar energy: The amount of solar energy that could be put to human use depends significantly on local factors such as land availability and meteorological conditions and demands for energy services. The technical potential varies over the different regions of the Earth, as do the assessment methodologies. As described in a comparative literature study (Krewitt et al.,2009) for the German Environment Agency, the solar electricity technical potential of PV and CSP depends on the available solar irradiance, land use exclusion factors and the future development of technology improvements. Note that this study used different assumptions for the land use factors for PV and CSP. For PV, it assumed that 98% of the technical potential comes from centralized PV power plants and that the suitable land area in the world for PV deployment averages 1.67% of total land area. For CSP, all land areas with high direct-normal irradiance (DNI)—a minimum DNI of 2,000 kWh/m2/yr (7,200 MJ/m/yr)—were Page 8 of 57

defined as suitable, and just 20% of that land was excluded for other uses. The resulting technical potentials for 2050 are 1,689 EJ/yr for PV and 8,043 EJ/yr for CSP. Analyzing the PV studies (Hofman et al., 2002; Hoogwijk, 2004; de Vries et al., 2007) and the CSP studies (Hofman et al., 2002; Trieb, 2005; Trieb et al., 2009a) assessed by Krewitt et al. (2009), the technical potential varies signifi cantly between these studies, ranging from 1,338 to 14,778 EJ/yr for PV and 248 and 10,791 EJ/yr for CSP. The main difference between the studies arises from the allocated land area availabilities and, to some extent, on differences in the power conversion efficiency used. The technical potential of solar energy for heating purposes is vast and difficult to assess. The deployment potential is mainly limited by the demand for heat. Because of this, the technical potential is not assessed in the literature except for REN21 (Hoogwijk and Graus, 2008) to which Krewitt et al. (2009) refer. In order to provide a reference, REN21 has made a rough assessment of the technical potential of solar water heating by taking the assumed available rooftop area for solar PV applications from Hoogwijk (2004) and the irradiation for each of the regions. Therefore, the range given by REN21 is a lower bound only.

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Chapter-2

Solar photovoltaic (PV) system 2.1 Photovoltaic (PV) system The increasing demand for energy, the continuous reduction in existing sources of fossil fuels and the growing concern regarding environment pollution, have pushed mankind to explore new technologies for the production of electrical energy using clean, renewable sources, such as solar energy, wind energy, etc. Among the non-conventional, renewable energy sources, solar energy affords great potential for conversion into electric power, able to ensure an important part of the electrical energy needs of the planet. The conversion of solar light into electrical energy represents one of the most promising and challenging energetic technologies, in continuous development, being clean, silent and reliable, with very low maintenance costs and minimal ecological impact. Solar energy is free, practically inexhaustible, and involves no polluting residues or greenhouse gases emissions. The conversion principle of solar light into electricity, called Photo-Voltaic or PV conversion, is not very new, but the efficiency improvement of the PV conversion equipment is still one of top priorities for many academic and/or industrial research groups all over the world.

2.2 Work of solar photovoltaic (PV) system: The sun delivers its energy to us in two main forms: heat and light. There are two main types of solar power systems, namely, solar thermal systems that trap heat to warm up water, and solar PV systems that convert sunlight directly into electricity.

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When the PV modules are exposed to sunlight, they generate direct current (“DC”) electricity. An inverter then converts the DC into alternating current (“AC”) electricity, so that it can feed into one of the building’s AC distribution boards (“ACDB”) without affecting the quality of power supply.

Figure: 2.1 solar photovoltaic (PV) systems

In the summary, the PV solar system consists of three parts: i) Solar panels or solar arrays, ii) Balance of system, iii) Load. 2.3 Types of photovoltaic (PV) systems: PV systems can provide clean power for small or large applications. They are already installed and generating energy around the world on individual homes, housing developments, offices and public buildings. Today, fully functioning solar PV installations operate in both built environments and remote areas where it is difficult to connect to the grid or where there is no energy Page 11 of 57

infrastructure. PV installations that operate in isolated locations are known as standalone systems. In built areas, PV systems can be mounted on top of roofs (known as Building Adapted PV systems – or BAPV) or can be integrated into the roof or building facade (known as Building Integrated PV systems – or BIPV). Modern PV systems are not restricted to square and flat panel arrays. They can be curved, flexible and shaped to the building’s design. Innovative architects and engineers are constantly finding new ways to integrate PV into their designs, creating buildings that are dynamic, beautiful and provide free, clean energy throughout their life. With the growing demand of solar power new technologies are being introduced and existing technologies are developing. There are three main types of solar PV cells: 

Single crystalline or mono crystalline



Multi- or poly-crystalline



Amorphous silicon

2.3.1 Single-crystalline or mono crystalline:

It is widely available and the most efficient cells materials among all. They produce the most power per square foot of module. Each cell is cut from a single crystal. The wafers then further cut into the shape of rectangular cells to maximize the number of cells in the solar panel.

Figure: 2.2 Single crystalline or mono crystalline Page 12 of 57

2.3.2 Polycrystalline cells:

They are made from similar silicon material except that instead of being grown into a single crystal, they are melted and poured into a mold. This forms a square block that can be cut into square wafers with less waste of space or material than round single-crystal wafers.

Figure: 2.3 Multi- or poly-crystalline

2.3.3 Amorphous Silicon: Amorphous silicon is newest in the thin film technology. In this technology amorphous silicon vapor is deposited on a couple of micro meter thick amorphous films on stainless steel rolls. Compared to the crystalline silicon, this technology uses only 1% of the material.

Figure: 2.4 Amorphous silicon Page 13 of 57

Table 2.1 Efficiency of different types of solar cells

Cell type

Efficiency, %

Mono crystalline

12 – 18

Polycrystalline

12 – 18

Amorphous Silicon

6–8

2.4 Components of a solar photovoltaic (PV) system:

A typical solar PV system consists of solar panel, charge controller, batteries, inverter and the load. Shows the block diagram of such a photovoltaic (PV) system

Solar panel

Charge controller

Battery System

Inverter

AC power

DC power

Figure 2.5 Block diagram of a typical solar PV system 2.4.1 Charge controller:

When battery is included in a system, the necessity of charge controller comes forward. A charge controller controls the uncertain voltage build up. In a bright sunny day the solar cells produce more voltage that can lead to battery damage. A charge controller helps to maintain the balance in charging the battery. Page 14 of 57

2.4.2 Batteries:

To store charges batteries are used. There are many types of batteries available in the market. But all of them are not suitable for solar PV technologies. Mostly used batteries are nickel/cadmium batteries. There are some other types of high energy density batteries such as- sodium/sulphur, zinc/bromine flow batteries. But for the medium term batteries nickel/metal hydride battery has the best cycling performance. For the long term option iron/chromium redox and zinc/manganese batteries are best. Absorbed Glass Mat (AGM) batteries are also one of the best available potions for solar PV use.

2.4.3 Inverter:

Solar panel generates dc electricity but most of the household and industrial appliances need ac current. Inverter converts the dc current of panel or battery to the ac current. We can divide the inverter into two categories. They are

Stand alone and



Line-tied or utility-interactive

2.5 Advantages of photovoltaic (PV): •

Environmentally friendly

•

No noise, no moving parts

•

No emissions

•

No use of fuels and water

•

Minimal maintenance requirements

•

Long lifetime, up to 30 years Page 15 of 57

•

Electricity is generated wherever there is light, solar or artificial

•

PV operates even in cloudy weather conditions

•

Modular or “custom-made” energy, can be designed for any application from watch to a multi-megawatt power plant

2.6 Disadvantage of photovoltaic (PV): •

PV cannot operate without light

•

High initial costs that overshadow the low maintenance costs and lack of fuel costs

•

Large area needed for large scale applications

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PV generates direct current: special DC appliances or inverters are needed in off-grid applications energy storage is needed, such as batteries.

2.7 Photovoltaic (PV) applications and market: An overview of the different solar cell technologies that are used or being developed for two main solar cell applications, namely space and terrestrial applications. The conversion efficiency of solar cells used in space applications is the initial efficiency measured before the solar cells are launched into the space. This conversion efficiency is also referred to as the begin-of-life efficiency. Today's commercial PV systems in terrestrial applications convert sunlight into electricity with efficiency ranging from 7% to 17%. They are highly reliable and most producers give at least 20 years guarantee on module performance. In case of the thin-film solar cells the best conversion efficiency that has been achieved in laboratory is shown together with the conversion efficiency that is typical for commercial solar cells. Page 16 of 57

CHAPTER-3

SOLAR PATH OF THE SUN

3.1 Basics of Solar Radiation: Radiation from the sun sustains life on earth and determines climate. The energy flow within the sun results in a surface temperature of around 5800 K, so the spectrum of the radiation from the sun is similar to that of a 5800 K blackbody with fine structure due to absorption in the cool peripheral solar gas. 3.2 Solar Constant and "Sun Value": The irradiance of the sun on the outer atmosphere when the sun and earth are spaced at 1 AU - the mean earth/sun distance of 149,597,890 km - is called the solar constant. Currently accepted values are about 1360 W m -2 (the NASA value given in ASTM E 490-73a is 1353 ±21 W m-2). The World Metrological Organization (WMO) promotes a value of 1367 W m-2. The solar constant is the total integrated irradiance over the entire spectrum (the area under the curve in Fig. 1 plus the 3.7% at shorter and longer wavelengths. The irradiance falling on the earth's atmosphere changes over a year by about 6.6% due to the variation in the earth/sun distance. Solar activity variations cause irradiance changes of up to 1%. For Solar Simulators, it is convenient to describe the irradiance of the simulator in “suns.” One “sun” is equivalent to irradiance of one solar constant.

Figure: 3.1 Spectrum of the radiation outside the earth’s atmosphere compared to spectrum of a 5800 K blackbody. Page 17 of 57

3.3 Extraterrestrial and Terrestrial Spectra: 3.3.1 Extraterrestrial Spectra: Fig. 1 shows the spectrum of the solar radiation outside the earth's atmosphere. The range shown, 200 - 2500 nm, includes 96.3% of the total irradiance with most of the remaining 3.7% at longer wavelengths. Many applications involve only a selected region of the entire spectrum. In such a case, a "3 sun unit" has three times the actual solar irradiance in the spectral range of interest and a reasonable spectral match in this range. Example The model 91160 Solar Simulator has a similar spectrum to the extraterrestrial spectrum and has an output of 2680 W m -2. This is equivalent to 1.96 times 1367 W m-2 so the simulator is a 1.96 sun unit.

3.3.2 Terrestrial Spectra The spectrum of the solar radiation at the earth's surface has several components (see Fig. 2). Direct radiation comes straight from the sun, diffuse radiation is scattered from the sky and from the surroundings. Additional radiation reflected from the surroundings (ground or sea) depends on the local "albedo." The total ground radiation is called the global radiation. The direction of the target surface must be defined for global irradiance. For direct radiation the target surface faces the incoming beam. All the radiation that reaches the ground passes through the atmosphere, which modifies the spectrum by absorption and scattering. Atomic and molecular oxygen and nitrogen absorb very short wave radiation, effectively blocking radiation with wavelengths