A Project Report On
“SOLAR TRACKING SYSTEM & HYBRID POWER GENERATION”
INDEX Sr. No.
Chapter/Sub-chapter
Page No.
LIST OF FIGURES LIST OF TABLES 1.
INTRODUCTION 1.1
2.
Introduction 1.1.1
Earth sun geometry
1.1.2
Energy from the sun
1.1.3
Photovoltaic energy
1.2
Necessity
1.3
Objectives
LITERATURE SURVEY 2.1
Global Energy Resources
2.2
Sun as the source of radiation
2.3
solar radiation basics
2.4
Types of solar photovoltaic
2.5
Solar trackers 2.5.1
Introduction to solar trackers
2.5.2
Maintenance
2.5.3
Tracker mounts types
2.6
basic PV cell constructions 2.6.1
2.7
Cell Module and Array OPEN CIRCUIT VOLTAGE AND SHORT CIRCUIT CURRENT
2.8
2.7.1
I-V Curve
2.7.2
P-V Curve solar tracers
2.8.1 Sun Tracking System
2.9
Tracker Types 2.9.1
Single Axis Trackers a) Horizontal Single Axis Tracker (HSAT) b) Vertical Single Axis Tracker (VSAT) c) Tilted Single Axis Tracker (TSAT) d) Polar Aligned Single Axis Trackers (PASAT)
2.9.2 Dual Axis Trackers a)Tip – Tilt Dual Axis Tracker (TTDAT) b) Azimuth-Altitude Dual Axis Tracker (AADAT) 2.10
Tracker Type Selection
2.11
Drive types 2.11.1 Active tracker 2.11.2 Passive tracker 2.11.3 Chronological tracker
3. SYSTEM DEVELOPMENT
3.1
Block Diagram
3.2
Microcontroller Atmega8
3.3
Overall circuit design
3.4
Software design
3.5
Algorithm/flowcharts
3.6
Descriptions
3.7
Some mathematical treatment or related information is required
4. PERFORMANCE ANALYSIS 4.1
System Operation
4.2
Experimental setup with photographs
4.3
Results at various stages may be compared with various inputs
4.4
Output at various stages with same waveforms
4.5
4.4.1
Comparison with fixed panel system
4.4.2
Comparison with plc based solar tracking system
Comparison of above results by at least two methods Justification for the differences or error
5.
HYBRID POWER GENERATION [WIND AND SOLAR] 5.1
Block diagram
5.2
Wind power generation
5.3
Anemometer
5.4
Observation Table For Variable Wind Speed
5.5
Observation table for output of wind mill 5.5.1
Wind speed Vs current
5.5.2
Voltage Vs speed of generator
5.6
Calculation for efficiency
5.7
Tariff calculation
6. CONCLUSIONS 6.1
Conclusions
6.2
Future Scope
6.3
Applications
6.4
Advantages
LIST OF FIGURES Figures
Description
Page No
01
Earth sun geometry
13
02
Structure of solar cell
15
03
Monocrystalline cell
16
04
polycrystalline or multicrystalline cell
16
05
Amorphous cells
17
06
PV cell structure and operation schematic
18
07
Basic PV cell construction
19
08
Actual construction of a module in a frame
20
09
Current versus voltage (i-v) characteristics of the PV module in sunlight and in dark Power versus voltage (p-v) characteristics of the PV module in sunlight
22
11
Horizontal Single Axis Tracker (HSAT)
26
12
Tilted Single Axis Tracker (TSAT)
27
13
Azimuth-Altitude Dual Axis
28
14
Passive trackers
30
15
Tracking system of typical solar system
32
16
LCD Display Panel 2 Line 16 Character
33
17
Solar panel specifications
34
18
Stepper motor specifications
35
19
Working of stepper motor
36
10
22
20
Coil magnetization of stepper motor
37
21
Gear system
40
22
Pin Configurations of Atmega8
42
23
Block diagram of microcontroller Atmega8
45
24
Flow chart of solar tracking program
46
25
ULN 2003
48
26
Logic diagram of ULN 2003
49
27
Connection of stepper motor with driver IC-ULN 2003
50
28
Stepper Motor Connections
51
29
Positive voltage regulators
55
30
Negative voltage regulators
55
31
Variable voltage regulators
56
32
Overall circuit design of solar tracker system
57
33
Experimental setup with photographs
58
34
Wind power generation
59
35
Block diagram of hybrid power generation
62
36
Observation taken on Anemometer
64
37
Graph for wind speed Vs current
65
List Of Graph Graph NO. 1
Description Current versus voltage (i-v) characteristics of the pv module in sunlight and in dark.
2
Power versus voltage (p-v) characteristics of the PV modue in sunlight
3
wind speed Vs current
Page NO
List Of Table Table No. 1.
Description
Page No
Technical performance of stepper motor
2.
Results at various stages compared with various inputs
3.
Comparison with fixed panel system
4.
Comparison with plc based solar tracking system
5.
Justification for the differences or error
6.
Variable wind speed
7.
wind speed vs current
8.
Voltage Vs speed of generator
1. INTRODUCTION 1.1
Introduction
In today‟s climate growing energy needs and increasing environmental concern, alternatives to the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative is solar energy. Solar energy is quite simply the energy produced by directly by the sun and collected elsewhere, normally the earth. The sun creates its energy throw a thermonuclear process that converts about 650, 000,000 tons of hydrogen to helium every second process creates heat and electromagnetic radiation. The heat remains in sun and is instrumental in maintaining the thermonuclear reaction. the electromagnetic radiation (including visible light, infrared-red light and ultraviolet radiation) streams out in to space in all directions. Only a very small fraction of the total radiation produced reaches the earth. The radiation that does reach the earth is the indirect source of nearly every type of 0energy used today. The exceptions are geothermal energy, and nuclear fission and fusion. Even fossil fuels owe their origins to the sun; they were once living plants and animals whose life was dependant up on the sun. Much of worlds required energy can be supplied directly by solar power. More still can be provided indirectly. The practicality of doing so will be examined as well as the benefits and drawbacks. In addition, the uses solar energy is currently applied to will be noted. Due to the nature of solar energy, two components are required to haw a fictional solar energy generator. These two components are collector and storage unit. The collector simply collects radiation that falls on it and converts fraction of it in to other forms of energy (either electricity and heat or heat alone). The storage unit is required because of the non-constant nature of solar energy; at a certain times only a very small amount of radiation will be received. At a night or during heavy cloud cover eg, the amount energy produced by the collector will be quite small. The storage unit can hold the excess energy produced during the period of maximum productivity, and reels it when the productivity drops. In practice, backup power supply is usually added, too, for the situation when the amount of energy required is greater than both what is being produced and what is soared in the container. Methods of collecting and solar energy vary depending on the uses planed for the solar generator. In general, there are three types of collectors and many forms of storage units. The three types of collectors are flat plate, focusing and passive collectors. Flat plate collectors are more commonly used type of collector today. They are arrays of solar panels arranged in simple plane. They can be of nearly any size, and have output that is directly related to a few variables including size, facing and cleanliness. These variables all affect the amount of radiation that falls on the collector. Often these collector panels have automated machinery that keeps the facing the sun. The additional energy they take in due to the correction of facing more than compensates for the energy needed to drive the extra machinery. Focusing collectors are essentially flat-plate collectors with optical devices arranged to maximize the radiation falling on focus of the collector. These are currently used only in a few scattered areas. Solar furnaces are examples of this types of collector.
Although they can produce far greater amounts of energy at single point than the flatplane collectors can, they lose some of the radiation that the flat plane panels do not. Radiation reflected off the ground will be used by flat-plane panels but usually will be ignored by focusing collectors (in snow covered regions, this reflected radiation can be significant). One other problem with focusing collectors in general is due to temperature. The fragile silicon components that absorb the incoming radiation lose efficiency at high temperatures, and if they get too hot they can even be permanently damaged. The focusing collectors by their very nature can create much higher temperatures and need more safe guards to protect their silicon components. Passive collectors are completely different from the other two types of collectors. The passive collectors absorb radiation and convert it to heat naturally, without being designed and built to do so. All objects have this property to some extent, but only some objects (like walls) will be able to produce enough heat to make it worthwhile. Often their natural ability to convert radiation to heat enhanced in some way or another (by being painted black, for example) and a system for transferring the heat to a different location is generally added.
1.1.2 Earth-Sun Geometry Our project is based on microcontroller system for solar tracking system. The major disadvantages of solar energy are the amount of sun light that arrives at the earth surface is not constant. It depends on location, time of day, time of year, and weather conditions. Because the sun does not deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate. We use solar panels to track the power from sun rays. Maximum power can get when sun is at 90 to panel. But this is not always possible because of earth rotation. The term earth rotation refers to the spinning of our planet on its axis. Because of rotation the earth‟s surface moves at the equator at a seed of about 467m per second. The ecliptic plane can be defined as two-dimensional flat surface that geometrically intersects the earth‟s orbital path around the sun. On this plane, the earth‟s axis is not right angles to this surface, but inclined at an angle of about 23.5 from the perpendicular.
1.1.2 Energy from the Sun The sun has produced energy for billions of years. Solar energy is the sun‟s rays (solar radiation) that reach the earth. Solar energy can be converted into other forms of energy, such as heat and electricity. In 1830s, the British astronomer John Herschel used a solar thermal collector box (a device that absorbs the sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun energy for lost things. Solar energy can be converted in to thermal (or heat) energy and used to. 1) Heat water –for use in home, buildings, swimming pools. 2) Heat space- inside greenhouses, homes, and other buildings. Solar energy can be converted to electrical in two ways: Photovoltaic (PV device) or solar cells change sunlight directly in to electricity. PV systems are often used in remote locations that are not connected to the electric grid. they are also used to power watches, calculator, and lighted road solar power plant indirectly generate electricity when the heat from solar thermal collector s is used to heat a fluid which produces steam that is used to power generator. Out of the 15 known solar electric generating units operating in the United States at the end of 2006, 10 of these are in California and 5 in Arizona. No statistics are being collector on solar plants that produce less than 1 megawatt of electricity, so there may be smaller solar plants in a number of other states.
1.1.3 Photovoltaic energy Photovoltaic energy is the conservation of sunlight into electricity. A photovoltaic cell, commonly called a solar cell or PV cell, is the technology used to convert solar energy directly into electrical energy. A photovoltaic cell is non-mechanical device usually made from silicon alloys. Sunlight is composed of photons, or particles of solar energy. These photon contain various amount of energy corresponding to the different wave length of the solar spectrum. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from materials atoms. Special treatment of the material surface during manufacturing make the front surface of the cell more respective to free electrons, so the electrons naturally migrate to the surface. Structure of photovoltaic frame electron leave their positions, holes are formed. When many electrons each carrying a negative charge, travel towards the surface of the cell, the resulting imbalance of charge between the cells front and back surface create a voltage potential like negative and positive terminals of a battery. When the two surfaces are connected through an external load, electricity flows. The photovoltaic cell is the basic building block of a photovoltaic system. Individual cell can vary in size from about 1 centimetre (1/2 inches) to about 10 centimetres (4 inches) across. However, one cell only
produces 1 or 2 watts which isn‟t enough power for most applications. To increase power output, cells are electrically connected into a package weather-tight module. Modules can be further connected to from an array. The term array refers to the entire generating plant, whether it is made up of one or several thousand modules. The number of modules connected together in an array depends on the amount of power output needed. The performance of a photovoltaic array is dependent upon sunlight. Climate condition (e.g. could, fog) have a significant effect on the amount of solar energy received by a photovoltaic array and, in turn its performance. Most current technology photovoltaic modules are about 10 percent efficient in converting sunlight. Further research is being conducted to raise this efficiency to 20 percent. The photovoltaic effect is the electrical potential developed between two dissimilar materials when their common junction is illuminated with radiation of photons. The photovoltaic cell, thus, converts light directly into electricity. The PV effect was discovered in 1839 by French physicist Becquerel. It remained in the laboratory until 1954, when Bell Laboratories produced the first silicon solar cell. It soon found application in the U.S. space programs for its high power capacity per unit weight. Since then it has been an important source of power for satellites. Having developed maturity in the space applications, the PV technology is now spreading into the terrestrial applications ranging from powering remote sites to feeding the utility lines. Some advantages of photovoltaic system are: 1) Conversion of sunlight to electricity is direct, so bulky mechanical generator systems are unnecessary. 2) PV array environmental impact is minimal, requiring no water for system cooling and generating no by-products. Photovoltaic cell, like batteries, generates direct current (DC) which is generally used for small loads (electronic equipment). When DC from photovoltaic cells is used for commercial applications or sold to electric using the electric grid, it must be converted to alternating current (AC) using inverters, solid state devices that convert DC power in to AC. Historically; PV has been used at remote sites to provide electricity. In the future PV arrays may be located at sites that are also connected to the electrical grid enhancing the efficiency of photovoltaic (PV) arrays, and are essential for concentration PV system. The project discusses a light tracking servo model which has been built to simulate the movement of a pv array
1.2 Necessity In today's climate of growing energy needs and increasing environmental concern, alternatives to the use of non-renewable and polluting fossil fuels is solar energy Solar energy is quite simply the energy produced directly by the sun and collected elsewhere, normally the Earth. The sun creates its energy through a thermonuclear process that converts about 650,000,000 tons of hydrogen to helium every second. The process creates heat and electromagnetic radiation. The heat remains in the sun and is instrumental in maintaining the thermonuclear reaction. The electromagnetic radiation (including visible light, infra-red light, and ultra-violet radiation) streams out into space in all directions. Only a very small fraction of the total radiation produced reaches the Earth. The radiation that does reach the Earth is the indirect source of nearly every type of energy used today.
1.3 About the project This project is designed to improve existing solar collection system to provide higher efficiency for lower cost. The existing system receives sun energy only for new hours, which is really not economical when compare the cost, which we are spending. Here the proposed system is designed to observe the sun light for the available maximum hours, for example – 12 hours a day. This project operates a solar panel to constantly face sun at 90 degrees to produce maximum voltage. It will move the solar panel from east to west to correct for the durational movement of the Sun in the sky. The set of Light Intensify Sensors give the input to the and it operates Stepper motors with mechanism
1.4 Objectives This project operates a solar panel to constantly face sun at 90 degrees to produce maximum voltage. It can move the solar panel from east to west also to correct for the durational movement of the Sun in the sky. The microcontroller give the input to the Stepper motor and operate with gear mechanism.
1.5 About the solar tracking The solar tracker is a device, which points a solar panel at the brightest part of the sky in order to achieve maximum power output from the solar panel. The solar panel will move as per the sun movement to collect maximum possible light energy from Morning 6.00 AM to Evening 6.00 PM
4. LITERATURE SURVEY
2.1 Global Energy resources Current global energy consumption is 4.1*1020J annually, which is equivalent to an instantaneous yearly-averaged consumption rate of 13*1012 W (13 trillion watts, or 13 terawatts TW). Projected population and economic growth will more than double this global energy consumption rate by the mid -21st century and more than triple rate by 2100, even with aggressive conservation efforts. Hence to contribute significantly to global primary energy supply, a prospective resource has to be capable of providing at least 1-10TW of power for an extended period of time. The threat of climate change imposes a second requirement on prospective energy resource. They must produce energy without the emission of additional greenhouse gases. Stabilization of atmospheric CO2 level at even twice their preanthropogenic value will require amounts of carbon-neutral energy by mid-century. The needed levels are in excess of 10 TW, increasing after 2050 to support economic growth for an expanding population. The three prominent options to meet this demand for carbon-neutral energy are fossil fuel use in conjunction with carbon sequestration, nuclear power, and solar power. The challenge for carbon sequestration is finding secure storage for the 25 billion metric tons of CO2 produced annually on earth. At atmospheric pressure, this yearly global emission of CO2 would occupy 12500 km3, equal to the volume of lake superior, it is 600 times the amount of CO2 injected every year into oil wells to super productions, 100 times amount of natural gas the industry draws in and out of geologic storage in the united states each year to smooth seasonal demand, and 20,000 times the amount of CO2 stored annually in Norway„s sleipner reservoir. Beyond finding storage volume carbon sequestration also must prevent leakage. A 1%leak rate would nullified the sequestration effort in a century, far too short a time to have lasting impact on climate change. Although many scientists are optimistic, the success of carbon sequestration on the required scale for sufficiently long time has not yet been demonstrated. Nuclear power is a second conceptually viable option. Producing 10TW of nuclear power would required construction of a new 1 giga-wattelectric nuclear fission plant somewhere in the world every other day for the next 50 year. Once that level of deployment was reached, the terrestrial uranium resource base would be exhausted in 10 years. The required fuel would the have to be mined from sea water or else breeder reactor technology would have to be developed and disseminated to countries wishing to meet their additional demand in this way. The third option is to exploit renewable energy sources, of which solar energy is by far the most prominent. The remaining global practically exploitable hydroelectric sources is less than 0.5TW. the cumulative energy in all the tides and ocean current in the world amounts to less than 2TW. The total geothermal energy at the surface of earth,
integrated over all the land area of the continents, is 12TW, of which only a small fraction could be practically extracted. the amount of globally extractable wind power has been estimated by the IPCC and others to be 2-4TWe.for comparison the solar constant at the top of the atmosphere is 170,000TW, of which on average, 120,000TW strikes the earth. It is clear that solar energy can be exploited on the needed scale to meet global energy demand in a carbon- neutral fashion without significantly affecting the solar resource. Solar energy storage and distribution are critical to match demand. The amount of produced by covering 0.16% of the earth‟s land area with 10% efficient solar cell is equal to that produced by 20000 1-GWe nuclear fission plants.
2.2 Sun as the source of radiation The sun is a sphere of intensely hot gaseous matter with a diameter of 1.39*109 m & is about 1.5*1011 m away from the earth. As seen from the earth the sun rotate on its axis once about every four weeks . However it does not rotate as a solid body, the equator takes about 27 days & the polar regions takes about 30 days for each rotation. The sun has an effective black body temperature of 5762 K. the temperature of innermost region, the core estimated between 8*106 to 40*106 K & the density about 100 times of that of water. The sun, in effect is a continuous fusion reactor with its constituents gases as the –containing vessel retained by the gravitational forces. several fusion reactor have been suggested to be source of energy radiated by the sun, the one to be considered the most important is the process in which four hydrogen atoms combined to form one helium atom, the mass of the helium nucleus is less than that of the four protons, some mass have been lost in the reaction & converted in to energy this energy is produced in the interior of the solar sphere, at the temperature of many million degrees. A schematic representation of the structure of sun is shown in figure. It is estimated that 90% of the energy is generated in the region 0 to 0.23R (where R is the radius of the sun), which contains 40% of the mass of the sun. At a distance 0.7R from the centre, the temperature drops to about 130000K & the density to 70 kg /m3, here convection process begin to become important. The zone from 0.7 to 1.0R is known as convective zone. Within this zone the temperature drops to about 5000K & the density to about 10-5 kg/m3
Fig-Earth sun geometry The sun surface appears to be composed of granules with the dimension of the cell varying from 1000 to 3000 m, & the lifetime of few minutes. Other features of the solar surface are small dark areas called sun pores, which are of same order of magnitude as the convective cells, & larger dark areas called sun spots which vary in size. The outer layer of convective zone is called photosphere. The age of the photosphere is sharply defined, even though it is of low density. It is essentially opaque as the gaseous of which it is composed of strongly ionised & able to absorb & emit a continuous spectrum of radiation. The photosphere is the source of the most of the solar radiation. 2.3 Solar Radiation Basics Solar radiation is a general term for the electromagnetic radiation emitted by the sun. We can capture and convert solar radiation into useful forms of energy, such as heat and electricity, using a variety of technologies. The technical feasibility and economical operation of these technologies at a specific location depends on the available solar radiation or solar resource. 2.3.1 Basic Principles Every location on Earth receives sunlight at least part of the year. The amount of solar radiation that reaches any one "spot" on the Earth's surface varies according to these factors:
Geographic location Time of day Season Local landscape Local weather.
Because the Earth is round, the sun strikes the surface at different angles ranging from 0º (just above the horizon) to 90º (directly overhead). When the sun's rays are vertical, the Earth's surface gets all the energy possible. The more slanted the sun's rays are, the longer they travel through the atmosphere, becoming more scattered and diffuse. Because the Earth is round, the frigid Polar Regions never get a high sun, and because of the tilted axis of rotation, these areas receive no sun at all during part of the year. The Earth revolves around the sun in an elliptical orbit and is closer to the sun during part of the year. When the sun is nearer the Earth, the Earth's surface receives a little more solar energy. The Earth is nearer the sun when it's summer in the southern hemisphere and winter in the northern hemisphere. However the presence of vast oceans moderates the hotter summers and colder winters one would expect to see in the southern hemisphere as a result of this difference. The 23.5º tilt in the Earth's axis of rotation is a more significant factor in determining the amount of sunlight striking the Earth at a particular location. Tilting results in longer days in the northern hemisphere from the spring (vernal) equinox to the fall (autumnal) equinox and longer days in the southern hemisphere during the other six months. Days and nights are both exactly 12 hours long on the equinoxes, which occur each year on or around March 23 and September 22. Countries like the United States, which lie in the middle latitudes, receive more solar energy in the summer not only because days are longer, but also because the sun is nearly overhead. The sun's rays are far more slanted during the shorter days of the winter months. Cities like Denver, Colorado, (near 40º latitude) receive nearly three times more solar energy in June than they do in December. The rotation of the Earth is responsible for hourly variations in sunlight. In the early morning and late afternoon, the sun is low in the sky. Its rays travel further through the atmosphere than at noon when the sun is at its highest point. On a clear day, the greatest amount of solar energy reaches a solar collector around solar noon. 2.3.2 Diffuse and Direct Solar Radiation As sunlight passes through the atmosphere, some of it is absorbed, scattered, and reflected by the following:
Air molecules Water vapour Clouds Dust Pollutants Forest fires Volcanoes.
This is called diffuse solar radiation. The solar radiation that reaches the Earth's surface without being diffused is called direct beam solar radiation. The sum of the diffuse and direct solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam radiation by 10% on clear, dry days and by 100% during thick, cloudy days. Scientists measure the amount of sunlight falling on specific locations at different times of the year. They then estimate the amount of sunlight falling on regions at the same latitude with similar climates. Measurements of solar energy are typically expressed as total radiation on a horizontal surface, or as total radiation on a surface tracking the sun. Radiation data for solar electric (photovoltaic) systems are often represented as kilowatt-hours per square meter (kWh/m2). Direct estimates of solar energy may also be expressed as watts per square meter (W/m2). Radiation data for solar water heating and space heating systems are usually represented in British thermal units per square foot (Btu/ft2).
Working of PV cells When light hits a surface, it may be reflected, transmitted, or absorbed. Absorption of light is simply the conversion of the energy contained in the incident photon to some other form of energy. Typically, this energy is in the form of heat; however, some absorbing materials such as photovoltaic (PV) cells convert the incident photons into electrical energy. A PV panel has one or more PV modules, which consist of connected PV cells. Figure 3 shows the schematic structure and operation of a PV cell.
Fig-PV cell structure and operation schematic Typically, a silicon PV cell contains two layers. The top layer consists of a thin sheet of phosphorus-doped (negatively charged or n-type) silicon. Underneath this sheet is a thicker
layer of boron-doped (positively charged or p-type) silicon. A unique characteristic of these two layers is that a positive-negative (pn) junction is created when these two materials are in contact. A pn junction is actually an electric field that is capable of creating an electrical potential when sunlight shines on the PV cell. When sunlight hits the PV cell, some of the electrons in the p-type silicon layer will be stimulated to move across the pn junction to the ntype silicon layer, causing the p-type layer to have a higher voltage potential than the n-type layer. This creates an electric current flow when the PV cell is connected to a load. The voltage potential created by a typical silicon PV cell is about 0.5 to 0.6 volts dc under opencircuit, no-load conditions. The power of a PV cell depends on the intensity of the solar radiation, the surface area of the PV cell, and its overall efficiency (FSEC 2005). The efficiency of each individual PV cell directly determines the efficiency of the PV panel. PV cells can be categorized into different types according to their component materials and structural features. Efficiency of commercially available PV panels is typically 7-17% (Green et al. 2005).
2.4 Photovoltaic Panels There are 3 basic types of construction of PV panels though all use silicon 2.4.1. Monocrystalline 2.4.2. Polycrystalline (or Multicrystalline) 2.4.3. Amorphous 2.4.1. Monocrystalline
Fig-Monocrystalline cell Monocrystalline cells are cut from a single crystal of silicon- they are effectively a slice from a crystal. In appearance, it will have a smooth texture and you will be able to see the thickness of the slice. These are the most efficient and the most expensive to produce. They are also rigid and must be mounted in a rigid frame to protect them.
2.4.2
Polycrystalline (or Multicrystalline)
Fig-polycrystalline or multicrystalline cell
Polycrystalline (or Multicrystalline) cells are effectively a slice cut from a block of silicon, consisting of a large number of crystals. They have a speckled reflective appearance and again you can you see the thickness of the slice.These cells are slightly less efficient and slightly less expensive than monocrystalline cells and again need to be mounted in a rigid frame. 2.4.3
Amorphous
Fig-Amorphous cells Amorphous cells are munufactured by placing a thin film of amorphous (non crystalline) silicon onto a wide choice of surfaces. These are the least effient and least expensive to produce of the three types. Due to the amorphous nature of the thin layer, it is flexible, and if manufactured on a flexible surface, the whole solar panel can be flexible.
One characteristic of amorphous solar cels is that their power output reduces over time, particularly during the first few months, after which time they are basically stable. The quoted output of an amorphous panel should be that produced after this stabilisation.
2.5 Types of solar photovoltaic cells PV cells can be divided in to three categories 1. Inorganic cells, based on solid-state inorganic semiconductors; 2. Organic cells , based on organic semiconductors;& 3. PEC cells, based on interfaces between semiconductors & molecules
Fig-Structure of solar cell The figure shows the structure of an inorganic solar cells based on the sandwich structure of two types of semiconductor material, one type has mobile free negative electrons (called an n type semiconductor ) & the second type mobile free positive holes (called a p type semiconductor). The sandwich, called a p-n junction, allows the photo-generated electrons & holes to be separated. & transferred to external wires for electrical power production. PV cells have no moving parts & are silent.
2.6 Basic PV cell construction
Fig-Basic PV cell construction figure shows the basic cell construction. For collecting the photocurrent, the metallic contacts are provided on both sides of the junction to collect electrical current induced by the impinging photons on one side. Conducting foil (solder) contact is provided over the bottom (dark) surface and on one edge of the top (illuminated) surface. Thin conducting mesh on the remaining top surface collects the current and lets the light through. The spacing of the conducting fibres in the mesh is a matter of compromise between maximizing the electrical conductance and minimizing the blockage of the light. In addition to the basic elements, several enhancement features are also included in the construction. For example, the front face of the cell has anti-reflective coating to absorb as much light as possible by minimizing the reflection. The mechanical protection is provided by the cover glass applied with a transparent adhesive.
2.6.1 Cell Module and Array
Fig-Actual construction of a module in a frame The solar cell described above is the basic building block of the pv power system. Typically, it is a few square inches in size and produces about one watt of power. For obtaining high power, numerous such cells are connected in series and parallel circuits on a panel (module) area of several square feet The solar array or panel is defined as a group of several modules electrically connected in series-parallel combinations to generate the required current and voltage. Figure shows the actual construction of a module in a frame that can be mounted on a structure. Mounting of the modules can be in various configurations as seen in Figure . In the roof mounting, the modules are in the form that can be laid directly on the roof. In the newly developed amorphous silicon technology, the pv sheets are made in shingles that can replace the traditional roof shingles on one-to-one basis, providing a better economy in the material and labour.
2.7 OPEN CIRCUIT VOLTAGE AND SHORT CIRCUIT CURRENT The two most important parameters widely used for describing the cell electrical performance is the open-circuit voltage Voc and the short-circuit current Isc. The short-circuit current is measured by shorting the output terminals, and measuring the terminal current under full illumination. Ignoring the small diode and the ground-leakage currents under zeroterminal voltage, the short-circuit current under this condition is the photocurrent IL. The maximum photo voltage is produced under the open-circuit voltage. Again, by ignoring the ground-leakage current, the open-circuit voltage as the following:
The constant KT/Q is the absolute temperature expressed in voltage (300°K = 0.026 volt). In practical photocells, the photocurrent is several orders of magnitude greater than the reverse saturation current. Therefore, the open-circuit voltage is many times the KT/Q value. Under condition of constant illumination, IL/ID is a sufficiently strong function of the cell temperature, and the solar cell ordinarily shows a negative temperature coefficient of the open-circuit voltage.
2.7.1 I-V Curve: The electrical characteristic of the PV cell is generally represented by the current versus voltage (I, V) curve. Figure shows the I-V characteristic of a PV module under two conditions, in sunlight and in dark. In the first quadrant, the top left of the I-V curve at zero voltage is called the short circuit current. This is the current we would measure with the output terminals shorted (zero voltage). The bottom right of the curve at zero current is called the open-circuit voltage. This is the voltage we would measure with the output terminals open (zero current). In the left shaded region, the cell works like a constant current source, generating voltage to match with the load resistance. In the shaded region on the right, the current drops rapidly with a small rise in voltage. In this region, the cell works like a constant voltage source with an internal resistance. Somewhere in the middle of the two shaded regions, the curve has a knee point.
Graph -Current versus voltage (i-v) characteristics of the pv module in sunlight and in dark.
If the voltage is externally applied in the reverse direction, say during a system fault transient, the current remains flat and the power is absorbed by the cell. However, beyond a certain negative voltage, the junction breaks down as in a diode and the current rises to a high value. In the dark, the current is zero for voltage up to the breakdown voltage which is the same as in the illuminated condition.
2.7.2 P-V Curve:
Graph -Power versus voltage (p-v) characteristics of the PV module in sunlight.
The power output of the panel is the product of the voltage and the current outputs. In Figure, the power is plotted against the voltage. Notice that the cell produces no power at zero voltage or zero current, and produces the maximum power at voltage corresponding to the knee point of the i-v curve. This is why PV power circuits are designed such that the modules operate closed to the knee point, slightly on the left hand side. The PV modules are modelled approximately as a constant current source in the electrical analysis of the system.
The photo conversion efficiency of the PV cell is defined as the following:
Obviously, the higher the efficiency, the higher the output power we get under a given illumination.
2.8 Solar trackers A solar tracker is a generic term used to describe devices that orient various payloads toward the sun. Payloads can be photovoltaic panels, reflectors, lenses or other optical devices. In standard 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 from a fixed amount of installed power generating capacity. In standard photovoltaic applications, it is estimated that trackers are used in at least 85% of commercial installations greater than 1MW from 2009 to 2012. In concentrated photovoltaic (CPV) and concentrated solar thermal (CSP) applications trackers are used to enable the optical components in the CPV and CSP systems. The optics in concentrated solar applications accept the direct component of sunlight light and therefore must be oriented appropriately to collect energy. Tracking systems are found in all concentrator applications because such systems do not produce energy unless oriented closely toward the sun.
2.8.1 Sun Tracking System From the various Electric Energy sources the solar now becoming more and more important for the human life. We can generate the solar energy from the sunlight by using solar panels which is becoming the individual energy generator with less resources and more useful.
Currently the solar panels are fixed on the roof of the building, which collects the sunlight and generates the electric energy. But from sunrise to sunset the position of the sun is not fixed and therefore the generated solar energy varies with sunlight collected by the panel. Sun Tracking System is mainly designed to find out the actual position on sun at daytime. The system detects the ultimate position at which the maximum solar energy will be generated by the panel. As the system is a closed loop system, it keeps the track of the percentage of energy generation at various positions. The solar panel alignment to the maximum power generation is controlled by the means of stepper motor.
2.9 Tracker Types
2.9.1Single Axis Trackers a) Horizontal Single Axis Tracker (HSAT) b) Vertical Single Axis Tracker (VSAT) c) Tilted Single Axis Tracker (TSAT) d) Polar Aligned Single Axis Trackers (PASAT) 2.9.2 Dual Axis Trackers a)Tip – Tilt Dual Axis Tracker (TTDAT) b) Azimuth-Altitude Dual Axis Tracker (AADAT) 2.10 Tracker Type Selection 2.11 Drive types 2.11.1 Active tracker 2.11.2 Passive tracker 2.11.3 Chronological tracker
2.9 Tracker Types Photovoltaic trackers can be grouped into classes by the number and orientation of the tracker‟s axes. Compared to a fixed mount, a single axis tracker increases annual output by approximately 30%, and a dual axis tracker an additional 6%. 2.9.1 Single Axis Trackers Single axis trackers have one degree of freedom that acts as an axis of rotation. The axis of rotation of single axis trackers is typically aligned along a true North meridian. It is possible to align them in any cardinal direction with advanced tracking algorithms. There are several common implementations of single axis trackers. These include Horizontal Single Axis Trackers, Vertical Single Axis Trackers, and Tilted Single Axis Trackers. The orientation of the module with respect to the tracker axis is important when modeling performance.
a) Horizontal Single Axis Tracker (HSAT)
Fig-Horizontal Single Axis Tracker (HSAT) Ray Tracker GC200 Horizontal Single Axis Tracker in California Wattsun HZ-Series Linear Axis Tracker in South Korea. These trackers use a horizontal axis. The axis of rotation for Horizontal Single Axis Tracker is horizontal with respect to the ground. The posts at either end of the axis of rotation of a Horizontal Single Axis Tracker can be shared between trackers to lower the installation cost. Field layouts with Horizontal Single Axis Trackers are very flexible. The simple geometry means that keeping all of the axis of rotation parallel to one another is all that is required for appropriately positioning the trackers with respect to one another. Appropriate spacing can maximize the ratio of energy production to cost, this being dependent upon local terrain and shading conditions and the time-of-day value of the energy produced. Backtracking is one means of computing the disposition of panels. Horizontal Trackers typically have the face of the module oriented parallel to the axis of rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation. Several manufacturers can deliver single axis horizontal trackers. In these, a long horizontal tube is supported on bearings mounted upon pylons or frames. The axis of the tube is on a North-South line. Panels are mounted upon the tube, and the tube will rotate on its axis to track the apparent motion of the sun through the day. Manufacturers include Array Technologies, Patriot Solar Group, Ray Tracker, Sun Power. b) Vertical Single Axis Tracker (VSAT) The axis of rotation for Vertical Single Axis Trackers is vertical with respect to the ground. These trackers rotate from East to West over the course of the day. Such trackers are more effective at high latitudes than are horizontal axis trackers. Field layouts must consider shading to avoid unnecessary energy losses and to optimize land utilization. Also optimization for dense packing is limited due to the nature of the shading over the course of a year.
Vertical Single Axis Trackers typically have the face of the module oriented at an angle with respect to the axis of rotation. As a module tracks, it sweeps a cone that is rotationally symmetric around the axis of rotation. c) Tilted Single Axis Tracker (TSAT)
Fig-Vertical Single Axis Tracker (HSAT) Single axis Sun Power T20 trackers, with roughly 20 degree tilt, at Nellis Air Force Base, in Nevada, USA. The arrays form part of the Nellis Solar Power Plant and was designed and built by Sun Power corporation. Credit: U.S. Air Force photo by Senior Airman Larry E. Reid Jr. All trackers with axes of rotation between horizontal and vertical are considered Tilted Single Axis Trackers. Tracker tilt angles are often limited to reduce the wind profile and decrease the elevated end‟s height off the ground. Field layouts must consider shading to avoid unnecessary losses and to optimize land utilization. With backtracking, they can be packed without shading perpendicular to their axis of rotation at any density. However, the packing parallel to their axis of rotation is limited by the tilt angle and the latitude. Tilted Single Axis Trackers typically have the face of the module oriented parallel to the axis of rotation. As a module tracks, it sweeps a cylinder that is rotationally symmetric around the axis of rotation. d) Polar Aligned Single Axis Trackers (PASAT) One scientifically interesting variation of a Tilted Single Axis Tracker is a Polar Aligned Single Axis Trackers (PASAT). In this particular implementation of a Tilted Single Axis Tracker the tilt angle is equal to the latitude of the installation. This aligns the tracker axis of rotation with the earth‟s axis of rotation. These are rarely deployed because of their high wind profile.
2.9.2 Dual Axis Trackers Dual axis trackers have two degrees of freedom that act as axes of rotation. These axes are typically normal to one another. The axis that is fixed with respect to the ground can be considered a primary axis. The axis that is referenced to the primary axis can be considered a secondary axis. There are several common implementations of dual axis trackers. They are classified by the orientation of their primary axes with respect to the ground. Two common implementations are Tip - Tilt trackers and Azimuth-Altitude trackers. The orientation of the module with respect to the tracker axis is important when modeling performance. Dual Axis Trackers typically have modules oriented parallel to the secondary axis of rotation. a) Tip – Tilt Dual Axis Tracker (TTDAT) A Tip – Tilt Dual Axis Tracker has its primary axis horizontal to the ground. The secondary axis is then typically normal to the primary axis. The posts at either end of the primary axis of rotation of a Tip – Tilt Dual Axis Tracker can be shared between trackers to lower installation costs. Field layouts with Tip – Tilt Dual Axis Trackers are very flexible. The simple geometry means that keeping the axes of rotation parallel to one another is all that is required for appropriately positioning the trackers with respect to one another. The axes of rotation of Tip – Tilt Dual Axis Trackers are typically aligned either along a true North meridian or an east west line of latitude. It is possible to align them in any cardinal direction with advanced tracking algorithms. Manufacturers include Patriot Solar Group.
Azimuth-Altitude Dual Axis Tracker - 2 axis solar tracker, Toledo, Spain
Point focus parabolic dish with Stirling system. The horizontally rotating azimuth table mounts the vertical frames on each side which hold the elevation trunnions for the dish and its integral engine/generator mount. b) Azimuth-Altitude Dual Axis Tracker (AADAT) An Azimuth – Altitude Dual Axis Tracker has its primary axis vertical to the ground. The secondary axis is then typically normal to the primary axis. Field layouts must consider shading to avoid unnecessary energy losses and to optimize land utilization. Also optimization for dense packing is limited due to the nature of the shading over the course of a year. This mount is used as a large telescope mount owing to its structure and dimensions. One axis is a vertical pivot shaft or horizontal ring mount, that allows the device to be swung to a compass point. The second axis is a horizontal elevation pivot mounted upon the azimuth platform. By using combinations of the two axis, any location in the upward hemisphere may be pointed. Such systems may be operated under computer control according to the expected solar orientation, or may use a tracking sensor to control motor drives that orient the panels toward the sun. This type of mount is also used to orient parabolic reflectors that mount a Stirling engine to produce electricity at the device. 2.10 Tracker Type Selection The selection of tracker type is dependent on many factors including installation size, electric rates, government incentives, land constraints, latitude, and local weather. Horizontal single axis trackers are typically used for large distributed generation projects and utility scale projects. The combination of energy improvement and lower product cost and lower installation complexity results in compelling economics in large deployments. In addition the strong afternoon performance is particularly desirable for large grid-tied photovoltaic systems so that production will match the peak demand time. Horizontal single axis trackers also add a substantial amount of productivity during the spring and summer seasons when the sun is high in the sky. The inherent robustness of their supporting structure and the simplicity of the mechanism also result in high reliability which keeps maintenance costs low. Since the panels are horizontal, they can be compactly placed on the axle tube without danger of self-shading and are also readily accessible for cleaning. A vertical axis trackers pivots only about a vertical axle, with the panels either vertical, at a fixed, adjustable, or tracked elevation angle. Such trackers with fixed or (seasonably) adjustable angles are suitable for high latitudes, where the apparent solar path is not especially high, but which leads to long days in summer, with the sun travelling through a long arc. Dual axis trackers are typically used in smaller residential installations and locations with very high government Feed In Tariffs.
2.11 Drive types 2.11.1 Active tracker Active trackers use motors and gear trains to direct the tracker as commanded by a controller responding to the solar direction. Active two-axis trackers are also used to orient heliostats - movable mirrors that reflect sunlight toward the absorber of a central power station. As each mirror in a large field will have an individual orientation these are controlled programmatically through a central computer system, which also allows the system to be shut down when necessary. Light-sensing trackers typically have two photo sensors, such as photodiodes, configured differentially so that they output a null when receiving the same light flux. Mechanically, they should be unidirectional (i.e. flat) and are aimed 90 degrees apart. This will cause the steepest part of their cosine transfer functions to balance at the steepest part, which translates into maximum sensitivity. Since the motors consume energy, one wants to use them only as necessary. So instead of a continuous motion, the heliostat is moved in discrete steps. Also, if the light is below some threshold there would not be enough power generated to warrant reorientation. This is also true when there is not enough difference in light level from one direction to another, such as when clouds are passing overhead. Consideration must be made to keep the tracker from wasting energy during cloudy periods.
2.11.2 Passive tracker
Fig-Passive trackers
Passive trackers use a low boiling point compressed gas fluid that is driven to one side or the other (by solar heat creating gas pressure) to cause the tracker to move in response to an imbalance. As this is a non-precision orientation it is unsuitable for certain types of concentrating photovoltaic collectors but works fine for common PV panel types. These will have viscous dampers to prevent excessive motion in response to wind gusts. Shader/reflectors are used to reflect early morning sunlight to "wake up" the panel and tilt it
toward the sun, which can take nearly an hour. The time to do this can be greatly reduced by adding a self-releasing tie down that positions the panel slightly past the zenith (so that the fluid does not have to overcome gravity) and using the tie down in the evening. (A slackpulling spring will prevent release in windy overnight conditions.) The term "passive tracker" is also used for photovoltaic modules that include a hologram behind stripes of photovoltaic cells. That way, sunlight passes through the transparent part of the module and reflects on the hologram. This allows sunlight to hit the cell from behind, thereby increasing the module's efficiency. Also, the module does not have to move since the hologram always reflects sunlight from the correct angle towards the cells.
2.11.3 Chronological tracker A chronological tracker counteracts the Earth's rotation by turning at an equal rate as the earth, but in the opposite direction. Actually the rates aren't quite equal, because as the earth goes around the sun, the position of the sun changes with respect to the earth by 360° every year or 365.24 days. A chronological tracker is a very simple yet potentially a very accurate solar tracker specifically for use with a polar mount (see above). The drive method may be as simple as a gear motor that rotates at a very slow average rate of one revolution per day (15 degrees per hour). In theory the tracker may rotate completely, assuming there is enough clearance for a complete rotation, and assuming that twisting wires are not an issue.
3. SYSTEM DEVELOPMENT 3.1 BLOCK DIAGRAM
Fir-Tracking system of typical solar system This is a solar tracking system which can be used as a power generating method from sunlight. This method of power generation is simple and is taken from natural resource. This needs only maximum sunlight to generate power. This project helps for power generation by setting the equipment to get maximum sunlight automatically. This system is tracking for maximum intensity of light. When there is decrease in intensity of light, this system automatically changes its direction to get maximum intensity of light. Here we are using the micro-controller for tracking and generating power from sunlight. It will process the input voltage from the Battery and control the direction in which the motor has to be rotated so that it will receive maximum intensity of light from the sun.
Solar panel: Solar cells convert light energy into electrical energy either indirectly (by first converting it into heat) or through a direct process known as the photovoltaic effect.
Fig-Solar panel specifications 20 Watt, 1.25A, 16V Length -63.5 CM Width- 35.56 CM Weight -3.2kg Cell material –silicon crystal
The most common types of solar cells are based on the photovoltaic effect. This happens when light falls on a two-layer semiconductor material and results in a potential difference, or voltage, between the two layers. The voltage produced in the cell is capable of driving a current through an external electrical circuit that can be utilised to power electrical devices. Solar cells are usually made from silicon, which is treated to release electrons-thereby generating an electric current-when light strikes it.
Liquid Crystal Displays (LCD)
Fig-LCD Display Panel 2 Line 16 Character An LCD is a small low cost display. It is easy to interface with a micro-controller because of an embedded controller. This controller is standard across many displays which means many micro-controller have libraries that make displaying messages as easy as a single line of code. LCD Display Panel 2 Line 16 Character Wide Viewing Angle Wide viewing angle of standard 16 character, 2 line LCD displays. Specifications: Number of Characters: 16 characters x 2 lines Module Dimension: 85(W) x 30(H) x 13.2(T)mm Viewing Display Area: 65(W) x 16(H)mm Character Size: 2.78(W) x 4.89(H)mm Other Mechanical Data: Yellow Green, 1/16 Duty, 12 o‟clock Supply Voltage for Logic: VDD-VSS Min 4.5V, Typ: 5.0V, Max: 5.5V.
Stepper motor
Fig-Stepper motor specifications
Input- 12 V , 0.5 A Torque - 2 kg Half step - 0.9 deg Full step - 1.8 deg A bi-polar stepper motor is being used for rotation in both directions. The stepper motor covers an full step angle1.8 degree per step and half step angle 0.9 degree. The output of the microcontroller is given to this motor through motor driver circuit and hence the motor is rotated accordingly, pointing in the direction of maximum intensity of sunlight.
Working of stepper motor The stepping motor is an electromagnetic device which converts digital pulses into discrete mechanical rotational movements. In rotary step motor, the output shaft of motor rotates in equal increments, in response to a train of input pulses.
Fig-Working of stepper motor
Principle of stepper motor. There are many kind of stepper motors. Unipolar type, Bipolar type, Single-phase type, Multi-phase type... Single-phase stepper motor is often used for quartz watch. On this page, I will explain the operation principle of the 2-phase unipolar PM type stepper motor. In the PM type stepper motor, a permanent magnet is used for rotor and coils are put on stator. The stepper motor model which has 4-poles is shown in the figure on the left. In case of this motor, step angle of the rotor is 90 degrees. As for four poles, the top and the bottom and either side are a pair. coil, coil and coil, coil correspond respectively. For example, coil and coil are put to the upper and lower pole. coil and coil are rolled up for the direction of the pole to become opposite when applying an electric current to the coil and applying an electric current to the coil. It is similar about and , too. The turn of the motor is controlled by the electric current which pours into , , and . The rotor rotational speed and the direction of the turn can be controlled by this control.
How stepper motors work Stepper motors consist of a permanent magnet rotating shaft, called the rotor, and electromagnets on the stationary portion that surrounds the motor, called the stator. Figure 1 illustrates one complete rotation of a stepper motor. At position 1, we can see that the rotor is beginning at the upper electromagnet, which is currently active (has voltage applied to it). To move the rotor clockwise (CW), the upper electromagnet is deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees CW, aligning itself with the active magnet. This process is repeated in the same manner at the south and west electromagnets until we once again reach the starting position.
Fig-Coil magnetization of stepper motor In the above example, we used a motor with a resolution of 90 degrees or demonstration purposes. In reality, this would not be a very practical motor for most applications. The average stepper motor's resolution -- the amount of degrees rotated per pulse -- is much higher than this. For example, a motor with a resolution of 5 degrees would move its rotor 5 degrees per step, thereby requiring 72 pulses (steps) to complete a full 360 degree rotation. You may double the resolution of some motors by a process known as "halfstepping". Instead of switching the next electromagnet in the rotation on one at a time, with
half stepping you turn on both electromagnets, causing an equal attraction between, thereby doubling the resolution. As you can see in Figure 2, in the first position only the upper electromagnet is active, and the rotor is drawn completely to it. In position 2, both the top and right electromagnets are active, causing the rotor to position itself between the two active poles. Finally, in position 3, the top magnet is deactivated and the rotor is drawn all the way right. This process can then be repeated for the entire rotation.
There are several types of stepper motors. 4-wire stepper motors contain only two electromagnets, however the operation is more complicated than those with three or four magnets, because the driving circuit must be able to reverse the current after each step. For our purposes, we will be using a 6-wire motor. Unlike our example motors which rotated 90 degrees per step, real-world motors employ a series of mini-poles on the stator and rotor to increase resolution. Although this may seem to add more complexity to the process of driving the motors, the operation is identical to the simple 90 degree motor we used in our example. An example of a multipole motor can be seen in Figure 3. In position 1, the north pole of the rotor's perminant magnet is aligned with the south pole of the stator's electromagnet. Note that multiple positions are alligned at once. In position 2, the upper electromagnet is deactivated and the next one to its immediate left is activated, causing the rotor to rotate a precise amount of degrees. In this example, after eight steps the sequence repeats.
The specific stepper motor we are using for our experiments (ST-02: 5VDC, 5 degrees per step) has 6 wires coming out of the casing. If we follow Figure 5, the electrical equivalent of the stepper motor, we can see that 3 wires go to each half of the coils, and that the coil windings are connected in pairs. This is true for all four-phase stepper motors.
However, if you do not have an equivalent diagram for the motor you want to use, you can make a resistance chart to decipher the mystery connections. There is a 13 ohm reistance between the center-tap wire and each end lead, and 26 ohms between the two end leads. Wires originating from seperate coils are not connected, and therefore would not read on the ohm meter.
Gear system
Fig-Gear system •
Gear ratio - 10:1 G1=10, G2= 100
We are used gear system for the purpose of movement of the solar panel from East to west and vice versa. The gear G1 is fitted on the shaft of the stepper motor. No of teeth‟s of G1 are 10. The gear G2 is fitted on the shaft of the solar panel. No of teeth‟s of G2 are 100.
Microcontroller: This is the heart of the circuit which performs all commanding and controlling operations. Microcontroller now days are becoming more popular because of several advantages over microprocessor. As it reduces the requirement of additional interfacing IC those are needed in microprocessor, the data which has to be read and controlled is directly fed to microcontroller and the software is designed in accordance with the requirement for controlling the circuit and action is taken by proper output device.
Microcontroller Atmega8 Features • High-performance, Low-power , 8-bit Microcontroller • Advanced Architecture – 130 Powerful Instructions – Most Single-clock Cycle Execution – 32 x 8 General Purpose Working Registers – Fully Static Operation – On-chip 2-cycle Multiplier • Nonvolatile Program and Data Memories – 8K Bytes of In-System Self-Programmable Flash In-System Programming by On-chip Boot Program True Read-While-Write Operation – 512 Bytes EPROM – 1K Byte Internal SRAM – Programming Lock for Software Security • Peripheral Features – Two 8-bit Timer/Counters with Separate Prescaler, one Compare Mode – One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode – Real Time Counter with Separate Oscillator – Three PWM Channels – 8-channel ADC Eight Channels 10-bit Accuracy – 6-channel ADC in PDIP package Eight Channels 10-bit Accuracy – Byte-oriented Two-wire Serial Interface – Programmable Serial USART – Master/Slave SPI Serial Interface – Programmable Watchdog Timer with Separate On-chip Oscillator – On-chip Analog Comparator • Special Microcontroller Features – Power-on Reset and Programmable Brown-out Detection – Internal Calibrated RC Oscillator – External and Internal Interrupt Sources – Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and
Standby • I/O and Packages – 23 Programmable I/O Lines – 28-lead PDIP, 32-lead TQFP, and 32-pad QFN/MLF • Operating Voltages – 2.7 - 5.5V (ATmega8L) – 4.5 - 5.5V (ATmega8) • Speed Grades – 0 - 8 MHz (ATmega8L) – 0 - 16 MHz (ATmega8) • Power Consumption at 4 Mhz, 3V, 25°C – Active: 3.6 mA – Idle Mode: 1.0 mA – Power-down Mode: 0.5 μA
Pin Configurations
Fig-Pin Configurations of Atmega8 Pin Descriptions VCC Digital supply voltage. GND Ground. Port B (PB7..PB0) 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..PC0) Port C is an 7-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port C 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. The minimum pulse length is given in Table 15 on page 38. Shorter pulses are not guaranteed to generate a Reset. Port D (PD7..PD0) 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. RESET 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. The minimum pulse length is given in Table 15 on page 38. Shorter pulses are not guaranteed to generate a reset.
ATmega8 2486Q–AVR–10/06 AVCC AVCC is the supply voltage pin for the A/D Converter, Port C (3..0), and ADC (7..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 Port C (5..4) use digital supply oltage, VCC. AREF AREF is the analog reference pin for the A/D Converter. ADC In the serve as inputs to the A/D converter. These pins are powered from the analog supply and serve as 10-bit ADC channels.
Block diagram of microcontroller Atmega8
Fig-Block diagram of microcontroller Atmega8
Flow chart:
Fig-Flow chart of solar tracking program
Algorithm 1) 2) 3) 4) 5)
START Initialization all input, output, peripheral and internal peripheral device Initialize 4 bit LCD Update LCD as pre condition continuously. Check panel voltage is greater than 2 volt or not. a) If „YES‟ then go to 6th step. b) If „NO‟ go to the 9th step. 6) Read the current position of the motor 7) Check it is at home position or not a) If „YES‟ go to the 4th step. b) If „NO‟ go to the 8th step. 8) Move motor to home position and go to 4th step. 9) Check home key pressed or not a) If “YES” go to the 10th step. b) If „NO‟ go to the 11th step. 10) Set current position of motor as home position and go then 4th step. 11) Check forward key is pressed or not. a) If „YES‟ go to next step. b) If „NO‟ go to 13th step. 12) Move motor forward by one step and go to the 4th step. 13) Check reversed key is pressed or not. a) If „YES‟ go to the 14th step. b) If „NO‟ go to the 15th step. 14) Move motor to reverse by one step and go to the 4th step 15) Measure panel vtg and display it. 16) Check time out accords for movement of motor. a) If „YES‟ go to next step b) If „NO‟ go to 4th step. 17) Move motor to forward position by one step. 18) END
ULN 2003
Fig-ULN 2003
DESCRIPTION The ULN2003 is a monolithic high voltage and high current Darlington transistor arrays. It consists of seven NPN darlington pairs that features high-voltage outputs with common-cathode clamp diode for switching inductive loads. The collector-current rating of a single darlington pair is 500mA. The darlington pairs may be parrlleled for higher current capability. Applications include relay drivers,hammer drivers, lampdrivers,display drivers(LED gas discharge),line drivers, and logic buffers. The ULN2003 has a 2.7kW series base resistor for each darlington pair for operation directly with TTL or 5V CMOS devices.
FEATURES * 500mA rated collector current(Single output) * High-voltage outputs: 50V * Inputs compatibale with various types of logic. * Relay driver application
LOGIC DIAGRAM
Fig-Logic diagram of ULN 2003
ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit Vo Output Voltage 50 V Vin Input Voltage (for ULN2002A/D - 2003A/D - 2004A/D) 30 V Ic Continuous Collector Current 500 mA Ib Continuous Base Current 25 mA Tamb Operating Ambient Temperature Range – 20 to 85 °C Tstg Storage Temperature Range – 55 to 150 °C
Connection of stepper motor with driver IC-ULN 2003:-
Fig-Connection of stepper motor with driver IC-ULN 2003
About this Circuit This is an easy to build stepper motor driver that will allow us to precisely control a unipolar stepper motor through our microcontroller parallel port. With a stepper motor we can build a lot of interesting gadgets such as robots, elevator, PCB drilling mill, camera panning system, automatic fish feeder, etc.
Stepper Motor Driver In able to move the rotor we will need a driver. Driver is a circuit that applies a voltage to any of the four stator coils. Driver can be built with IC such as ULN2003 (pictured on the circuit diagram), four darlington transistors or four power transistors such as 2N3055.
Stepper Motor Connections
Fig-Stepper Motor Connections motor should have five or six connections depending on the model. If the motor has six connections like the one pictured above, you have to join pins 1 and 2 (red) together and connect them to a (+) 12-24V voltage supply. The remaining pins; a1 (yellow), b1 (black), a2 (orange), b2 (brown) should be connected to a driver (ULN2003) as shown on the schematic.
Stepping Modes There are several stepping modes that you can use to drive the stepper motor. 1. Single Stepping - the simplest mode turns one coil ON at a time. 48 pulses are needed to complete one revolution. Each pulse moves rotor by 7.5 degrees. The following sequence has to be repeated 12 times for motor to complete one revolution. Pulse 1 2 3 4
Coil a1 Coil b1 Coil a2 Coil b2 ON ON ON ON
2. High Torque Stepping - high power / precision mode turns ON two coils on at a time. 48 pulses are needed to complete one revolution. Each pulse moves rotor by 7.5 degrees.
The following sequence has to be repeated 12 times for motor to complete one revolution. Pulse 1 2 3 4 3. Half Stepping and motor needs complete one pulse moves rotor 3.75 degrees. single stepping green) and high (darker green).
Coil a1 Coil b1 Coil a2 Coil b2 ON ON ON ON ON ON ON ON
Pulse Coil a1 Coil b1 Coil a2 Coil b2 ON 1 ON ON 2 ON 3 ON ON 4 ON 5 ON ON 6 ON 7 ON ON 8
stepping is doubled 96 pulses to revolution. Each by approximately Notice the mix of mode (lighter torque mode
Technical performance of stepper motor
Type STM 601
Torque Kg cm 2
Voltage Volts 6, 12, 24
Current Ampere/Phase
Weight in Kg. (Appro.)
ø mm
L mm
1, 0.5, 0.25
0.6
56.50
59
Component list
Power supply 12 v dc ..............................01 Solar panel 20w, 16v...........................01 Stepper motor ...........................01 Voltage regulators 7805.................................01 Driver IC ULN 2003 Microcontroller At mega 8
voltage regulators(7805) Voltage regulators produce fixed DC output voltage from variable DC. Normally we get fixed output by connecting the voltage regulator at the output of the filtered DC. It can also used in circuits to get a low DC voltage from a high DC voltage (for example we use 7805 to get 5V from 12V). There are two types of voltage regulators 1. fixed voltage regulators(78xx,79xx) 2. variable voltage regulators(LM317) In fixed voltage regulators there is another classification 1. +ve voltage regulators 2. -ve voltage regulators POSITIVE VOLTAGE REGULATORS This include 78xx voltage regulators. The most commonly used ones are 7805 and 7812. 7805 gives fixed 5V DC voltage if input voltage is in (7.5V,20V). Suppose if input is 6V then output may be 5V or 4.8V, but there are some parameters for the voltage regulators like maximum output current capability, line regulation etc.. , that parameters won't be proper. In following figure, we can see the voltage regulator
Fig-Positive voltage regulators
The above diagram show how to use 7805 voltage regulator. In this you can see that coupling capacitors are used for good regulation. But there is no need for it in normal case. But if we are using 7805 in analog circuit you should use capacitor, otherwise the noise in the output voltage will be high.The mainly available 78xx IC's are 7805,7809,7812,7815,7824
NEGATIVE VOLTAGE REGULATORS Mostly available -ve voltage regulators are of 79xx family. You will use -ve voltage if you use IC741. For IC741 +12v and -12v will be enough, even though in most circuits we use +15v and -15v. 7805 gives fixed -5V DC voltage if input voltage is in (-7V,-20V)
Fig-Negative voltage regulators
The mainly available 79xx IC's are 7905,7912 1.5A output current,short circuit protection,ripple rejection are the other features of 79xx and 78xx IC's
VARIABLE VOLTAGE REGULATORS Most commonly variable voltage regulator is LM317 although other variable voltage regulators are available. The advantage of variable voltage regulator is that you can get a variable voltage supply by just varying the resistance only.
Fig-Variable voltage regulators
Overall circuit design:-
Fig-Overall circuit design of solar tracker system
4. PERFORMANCE ANALYSIS 4.1 System Operation The main theme of our project is hybrid power generation and it is nothing but the combination of wind mill and solar tracker, using this concept we can obtain maximum power. We give high priority to renewable energy sources and then authorized power system. So authorized power supply used as option.
4.2 Experimental setup with photographs
Fig-Solar tracking system
Fig: wind power generation
4.3 Results at various stages compared with various inputs Panel position
Time
Towards East Towards East Towards East Towards East Towards East Towards East In east-west plane In east-west plane Towards west Towards west Towards west Towards west
7.00am 8.00am 9.00am 10.00am 11.00am 12.00pm 13.00pm 14.00pm 15.00pm 16.00pm 17.00pm 18.00pm
Towards west
19.00pm
Voltage output (Volts)
The model was analysed from 7.00am to19.00pm for one day. The result obtained are tabulated in the above table.
4.4 Comparison of above results by at least two methods:A) Comparison with fixed panel system:-
Panel position
Time [Hrs]
In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane In east-west plane
7.00am 8.00am 9.00am 10.00am 11.00am 12.00pm 13.00pm 14.00pm 15.00pm 16.00pm 17.00pm 18.00pm 19.00pm
Voltage output [Volts]
B] Comparison with plc based solar tracking system:-
Panel position
Time [Hrs]
Voltage output [Volts]
Towards east Towards east Towards east Towards east Towards east Towards east In east-west plane In east-west plane Towards west Towards west Towards west Towards west Towards west 4.5] justification for the differences or error:-
Time [Hrs]
Solar tracking system
Fixed position system
7.00am 8.00am 9.00am 10.00am 11.00am 12.00pm 13.00pm 14.00pm 15.00pm 16.00pm 17.00pm 18.00pm 19.00pm
11.2 volts 12.6 volts 13.5 volts 14.0 volts 15.1 volts 16.7 volts 16.8 volts 16.8 volts 16.2 volts 15.9 volts 13.8 volts 10.8 volts 8.1volts
4.0volts 6.5 volts 9.5 volts 12.2 volts 14.7 volts 16.7 volts 16.7 volts 16.3 volts 14.2 volts 12.2 volts 10.5 volts 7.9 volts 3.6 volts
It is clear that output of solar tracking system is more than fixed panel system. So solar tracking system is better as compared to normal system.
5 HYBRID POWER GENERATION [WIND AND SOLAR] :5.1 Block diagram:-
Fig. Hybrid power generation
5.2 Wind power generation It is the one part of power generation in this system we are used gear system to obtaining maximum speed of rotor of alternator. We know that wind is a form of solar energy. Wind is caused by the uneven heating of atmosphere by the sun, the irregularities of the earth surface and rotation of earth. Wind flows patterns are modified by the earth terrain, surface of water and can be used to generate electricity. The terms wind energy or wind power described the process by which the wind is used to generate the mechanical power and it used to generate electricity. Wind turbines converts the kinetic energy in to mechanical power. This mechanical power can be used for specific task (pumping water) or generator can converts mechanical power in to electricity to power houses, businesses, schools. 5.3 Anemometer
This is measuring instrument which is help to measure wind speed in m/s or kmph or kph. Using this meter we can measure wind speed at different location at different time. Using this meter we can take varies reading of wind speed at roof of our college at different location up to the 15 day‟s. 5.4 OBSERVATION TABLE FOE VARIALE WIND SPEED
Sr no
Wind velocity(m/s)
Revolution(rpm)
1)
4m/s
50rpm
2)
4.5m/s
70rpm
3)
5m/s
85rpm
4)
6m/s
100rpm
5)
8m/s
115rpm
Table no. Variable wind speed
Fig-Observation taken on Anemometer
5.5 Observation table for output of wind mill: 5.5.1 Wind speed Vs current Sr. no.
Wind speed (m/s)
Current(A)
1.
2.5
4.2
2.
3.4
5.7
3.
5.0
7.6
4.
5.5
8.4
Table no- wind speed vs current
Graph for wind speed Vs current
Graph-wind speed Vs current 5.5.2 Voltage Vs speed of generator Sr. no
Speed in RPM of generator
Volt(V)
1.
1000
11.5
2.
1296
12.1
3.
1470
12.3
4.
1680
12.8
Table no- Voltage Vs speed of generator
5.6 Calculation for efficiency: Wind power= 1/2*ρ*A*V3*Cp Here, ρ= air density in kg/m3 A=area sweft by rotor in m2 V=velocity of wind in m/s Cp=air coefficient Wind power=1/2*1.125*3.14*1.52*53*.59 =293.08 Actual output = 7.6*12 =91.2 So, % efficiency = (91.2/293 08)*100 =31.11
5.7 Tariff calculation : Observation Per hour wind mill output = 110W Average hours per day =10 hours So total output per day=10*110 =1100W Per hour solar tracking output=20W Average hour per day=10hours So total output per day=200W Total power obtained per day=1100+200 =1300W =1.3unit So if 1 unit =3.50Rs Total cost per day =1.3*3.50 = 4.55Rs So total cost per month=30*4.55 = 136.5Rs Per year cost=136.5*12 =1638Rs
6.CONCLUSIONS 6.1 conclusions To investigate the PV output power for tracking mode and fixed mode an experimental study is done under local climate. Designed simplicity, Low cost and material availability will make the designed tracking system more effective and acceptable in the market. This tracking system is more compact and easier than any other tracking system with minimum cost. This device does not need auxiliary power and may adjust automatically depending on the direction of the sun. With the designed Sun tracker, it is possible to get substantially more power from each PV panel and this increase in power results in lower cost per watt. From the result of the performance test of designed system the following conclusion can be drawn. • The designed solar tracker automatically controlled and follows the sun path preciously; • The efficiency of the tracking solar panel with respect to fixed panel was 23% at average intensity 1100 W/m2; • The use of software outside the mechanical part makes the tracker flexible for future development. The experiments done were implemented during three month. It is necessary to test during other months and The future development of the tracker should include a new case containing the method and all moving parts with electronics circuit, allowing continuous operation under local conditions. Although ASTS is a prototype towards a real system, but still its software and hardware can be used to drive a real and very huge solar panel. A small portable battery can drive its control circuitry. Therefore by just replacing the sensing instrument, its algorithm and control system can be used in RADAR and moveable Dish Antennas. The original purpose of this project is the power generation by setting the equipment to get maximum sunlight automatically. Although due to resources constraints we just accomplished the tracking part of the system.
6.2 Future scope 6.3 Applications
In Remote areas implementing a small power systems units at each home. Using this system to getting hot water. Street lights. Water heater. Home appliances. Solar cars etc. 6.4 Advantages
The advantage of this unit is that to run the system it does not need computer Solar cells directly convert the solar radiation into electricity using photovoltaic effect without going through a thermal process. During the winter the sun has a low position , tracking angle from sunrise to sunset is shortened. Depending on the radiation intensity, it may sinks under a predefined value for instance at dusk , when the sky is cloudy, tracking is interrupted. Max. solar energy saving at reduced cost. External power supply is not required.
References 1. Mukund R. Patel, “wind & solar power systems” 1999 www.crcpress.com 2. http://images.google.co.in/ , access date 29 Jan 2011 3. http://energysavers.gov/renewable_energy/solar, access date 2 Feb 2011 4. http://www.sandia.gov/news/resources/releases/2004/ renew-energybatt/stirling.html; access date: 24 Jan 2011 5. http://www.mstracey.btintrrnet.co.uk/technical /theory ; access date: 29 Jan 2011 6. Basic Research needs of solar energy utilization, report California institute of technology,pp,16 ,6 march 2011 7. http://en.wikipedia.org/wiki/solar_power , access date: 22 Jan 2011 8. http://www.renewableenergyworld.com/rea/partner/conergy-inc,access date: 24 Feb 2011 9. http://www.allenbradely.com, access date:1 March 2011 10. H.P. Garg & J. Prakash – solar energy - fundamentals & application, Tata McGraw hill, pp.2,3
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