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7/27/2019 Solar tracker project
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INTRODUCTION
1.1 HISTORY
Sun is the primary source of Energy. The earth receives 16 x 1018
units of energy
from the sun annually, which is 20,000 times the requirement of mankind on the Earth. Some
of the Solar Energy causes evaporation of water, leading to rains and creation of rivers etc.
Some of it is utilized in photosynthesis which is essential for sustenance of life on earth. Man
has tried from time immemorial to harness this infinite source of energy. But has been able to
tap only a negligibly fraction of this energy till today.
In the year 1767 a Swiss scientist named Horace-Benedict de Saussure created the
first solar collector an insulated box covered with three layers of glass to absorb heat
energy. Saussures box became widely known as the first solar oven, reaching temperatures
of 230 degrees fahrenheit.
In 1839 a major milestone in the evolution of solar energy happened with the defining
of the photovoltaic effect. A French scientist by the name Edmond Becquerel discovered this
using two electrodes placed in an electrolyte. After exposing it to the light, electricity
increased.
In 1873, Willoughby Smith discovered photoconductivity of a material known as
selenium. The discovery was to be further extended in 1876 when the same man discovered
that selenium produces solar energy. In 1977 the US government embraced the use of solar
energy by launching the Solar Energy Research Institute. Other governments across the
world soon followed.
In 1981, Paul Macready produced the first solar powered aircraft. The aircraft used
more than 1600 cells, placed on its wings. The aircraft flew from France to England. In the
year 1982 there was the development of the first solar powered cars in Australia.
The past few years have seen enormous investment in utility-scale solar plants, with
records for the largest frequently being broken. As of 2012, the historys largest solar energy
plant is the Golmud Solar Park in China, with an installed capacity of 200 megawatts. This is
arguably surpassed by Indias Gujarat Solar Park, a collection of solar farms scattered around
the Gujarat region, boasting a combined installed capacity of 605 megawatts.
The broad categories of possible large scale applications of solar power are the heating
and cooling of residential and commercial buildings.
A. The chemical and Biological conversion of organic material to liquid, solid and
gaseous fuels.
B. Conversion of solar energy to Electricity.
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In this project we use the solar energy for the generation of electrical energy, by using solar
cells.
The solar cell receives the solar energy. The solar cells operate on the principle of
photovoltaic effect, by using solar cells. Basically the cells are placed in an open and fixed
manner.
1.2 ENERGY SCENERIO
Drastic changes in energy conversion system are anticipated due to shortage of
conventional fuels. Fuel deposit in the world will soon deplete by the end of 2020. Fossil fuel
scarcity will be maximum. The main reasons for the above are due to increasing demand for
electricity, rising population, rapid advance in technology.
It is worthwhile to mention here that indiscriminate use of commercial energy has led
to serious environment problems like air and water pollutions. Man, when he is embarking on
use of alternate sources of energy should bear in mind, his environment. The creation of new
source of perennial environmentally acceptable, low cost electrical energy as a replacement
for energy from rapidly depleting resources of fossil fuels is the fundamental need for the
survival of mankind.
1.3 SOLAR ENERGY OPTIONS
Solar energy has the greatest potential of all the sources of renewable energy and it
will be one of the most important sources of energy especially when other sources in the
country have depleted. Solar energy could supply all the present and future energy needs of
the world on a connecting basis. This makes it one of the most promising of the
nonconventional energy sources.
Solar Energy can be a major source of power. Its potential is 178 billion MW which
is about 20,000 times the worlds demand. The energy radiated by the sun on a bright sunny
day is approximately 1kw/m2. The problem associated with the use of solar energy is that its
availability varies widely with time. The variations in availability occur daily, because of the
day-night cycle and also seasonally because of Earths orbit around the sun. In addition
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variations occur at a specific location because of local weather conditions. Consequently the
energy collected with the sun is shining must be stored for use during periods when it is not
available. Attempts have been made to make use of this energy in raising steam which may
be used in driving the prime movers for the purpose of generation of electrical energy.
However due to large space requirement and uncertainty of availability in constant rate this
method becomes ineffective.
Photovoltaic cell is an alternate device used for power generation which converts suns
radiation directly into electrical power. Thus power generated can be stored and utilized.
1.4 GENERAL CONCEPT
In 1968 Dr. Peter Glaser in the U.S. Published an idea that centered on the fact that in
orbit close to earth, 1.43 KW of solar energy illuminates may one square meter which is
considerably greater and one more continuous than an anyone square meter on the Earth
which, even when perpendicular to the sun can receive only a maximum of 1 kw. His idea
was, converting sunlight to electricity to convert to a radio frequency signal and beamed
down to the earth carrying significant levels of energy. This electricity is by establishing a
very large array of solar cells in geostationary orbit. A receiving antenna station on the earth
would convert this radio frequency back into an alternate current which would be fed into a
local grid.
The applications of solar energy which are enjoying most success today are:
1) heating and cooling of residential buildings
2) Solar water heating
3) Solar drying of agriculture and animal products
4) Solar distillation on a small community scale
5)
Salt production by evaporation of seawater or inland brines6) Solar cookers
7) Solar engines for water pumping
8) Food refrigeration
9) Bio conversion and wind energy, which are indirect source of solar energy
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10) Solar furnaces
1.5 ENVIRONMENTAL IMPACT OF SOLAR POWER
1.5.1 AIR POLLUTION
This can be caused by chemical reactants used in storage or organic fluids for heat
transport. The release of CO, SO2, SO3, hydrocarbon vapors and other toxic gases should be
accounted, though their magnitude is not high. The fire hazard associated with overheated
organic working fluids exists. Human tissues when exposed would be destroyed because of
high energy flux densities.
1.5.2 LAND USES
Solar plants require large land and the collection field produce shading not normally
present over large areas. This may cause disturbance in local ecosystem.
1.5.3 NOISE AND THERMAL EFFECT
The thermal effects of solar plants are minimal. Actually these systems eliminate
local thermal pollution associated with fossil fuel combustion. Some reduction in local
environmental heat budget or balance will occur if electricity produced is exported
elsewhere. Solar systems do not add any new noise to that already existing in the present
industrial or utility areas.
1.6 MAJOR ADVANTAGES OF SOLAR CELL
1) Solar cells directly convert the solar radiation into electricity using photovoltaic effect
without going through a thermal process.
2) Solar cells are reliable, modular, durable and generally maintenance free and
therefore, suitable even in isolated and remote areas.
3) Solar cells are compatible with almost all environments, respond instantaneously with
solar radiation and have an expected life time of 20 or more years.
Solar cells can be located at the place of use and hence no distribution network is required.
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1.7 LIMITATIONS OF USING SOLAR ENERGY
1. Solar energy can only be harnessed when it is daytime and sunny.
2.Solar collectors, panels and cells are relatively expensive to manufacture although prices
are falling rapidly.
3.Solar power stations can be built but they do not match the power output of similar sized
conventional power stations. They are also very expensive.
4.In countries such as the UK, the unreliable climate means that solar energy is also
unreliable as a source of energy. Cloudy skies reduce its effectiveness.
5.Large areas of land are required to capture the suns energy. Collectors are usually arranged
together especially when electricity is to be produced and used in the same location.
6.Solar power is used to charge batteries so that solar powered devices can be used at night.
However, the batteries are large and heavy and need storage space. They also need replacing
from time to time.
1.8 PRINCIPLES OF OPERATION SOLAR PHOTOVOLTAICS
The solar energy can be directly converted into electrical energy by means of
photovoltaic effect, i.e. conversion of light into electricity. Generation of an electromotive
force due to absorption of ionizing radiation is known as photovoltaic effect.
The energy conversion devices which are used to convert sunlight to electricity by use
of the photovoltaic effect are called solar cells.
Photo voltaic energy conversion is one of the most popular nonconventional energy
sources. The photovoltaic cell offers an existing potential for capturing solar energy in a way
that will provide clean, versatile, renewable energy. This simple device has no moving parts,
negligible maintenance costs, produces no pollution and has a lifetime equal to that of a
conventional fossil fuel.
Photovoltaic cells capture solar energy and convert it directly to electrical current by
separating electrons from their parent atoms and accelerating them across a one way
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electrostatic barrier formed by the junction between two different types of semiconductor
material.
1.8.1 PHOTOVOLTAIC EFFCT ON SEMICONDUCTOR
Semiconductors are materials which are neither conductors nor insulators. The photo
voltaic effect can be observed in nature in a variety of materials but semiconductors has
shown best performance.
When photons from the sun are absorbed in a semiconductor they create for electrons
with higher energies than the electrons which provide the boarding in the base crystal.
Once these electrons are created, there must be an electric field to induce these higher
energy electrons to flow out of the semiconductor to do useful work. The electric field in
most solar cells is provided by a junction of materials which have different electrical
properties.
To understand more about the functioning and properties of semiconductors, let us
briefly discuss. Semiconductors are classified into 1) Extrinsic semiconductor 2) Intrinsic
semiconductor. Semiconductors in its purest form are called intrinsic and when impurities are
added it is called extrinsic. Further extrinsic semiconductors are divided into p type and N
type semiconductor.
1.8.2 P-TYPE SEMICONDUCTOR
When a small amount of pentavalent impurities (e.g. Gallium, Indium, Aluminum,
and Boron) are added to intrinsic semiconductor, it is called as p type semiconductor.
In p type semiconductor, when an electric potential is applied externally, the holes are
directed towards the negative electrode. Hence current is produced.
1.8.3 N- TYPE SEMICONDUCTOR
When a small amount of pentavalent impurities (e.g. Antimony, Arsenic, Bismuth,
Phosphorus) are added to intrinsic semiconductors it is called N type semiconductor.
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When an external electrical field is applied the free electrons are directed towards
positive electrode. Hence current is produced.
1.8.4 PN JUNCTION SILICON SOLAR CELL
A PN junction is formed from a piece of semiconductor by diffusing p type materials
to one half side and N type materials to other half side.
It consists of both types of semiconductor materials. The N type layer is situated
towards the sunlight. As N type layer is thin, light can penetrate through it.
The energy of the sunlight will create free electron in the N type material and holes in
the p type material. This condition built up the voltage with in the crystal. Because the
electrons will travel to the +ve region and the holes will travel to the ve region. This
conduction ability is one of the main technical goals in fabricating solar cells.
1.9 PURIFICATION AND REFORMATION INTO WAFERS
The purification process basically entails high temperature melting of the sand and
simultaneous reduction in the presence of hydrogen. This results in a very pure
polycrystalline form of silicon.
The next step is to reform this silicon into a single crystal and then cut the crystal into
a single crystal and then cut the crystal into individual wafers. There are two methods namely
czochralski growth method and film fed growth. The former method produces single,
cylindrical crystals and later produces continuous ribbon of silicon crystals.
Then this cylindrical crystal and ribbon crystal is transformed into disc shaped cells
and rectangular cells by slicing. After that one side is doped by exposure to high temperature
phosphorus, forming a thin layer of N type material. Similarly p type is made. Electrical
contacts are applied to the two surfaces, an anti-reflection coating is added to the entire
surface and the entire cell is then sealed with protective skin.
1.10 ANTIREFLECTIVE COATING
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Antireflective coating (arc) is an important part of a solar cell since the bare silicon
has a reflection coefficient of 0.33 to 0.54 in the spectral range of 0.35 to 1.1 cm. The arc not
only reduces the reflection losses but also lowers the surface recombination velocity. A
single optimal layer of ARC can reduce the reflection to 10 percent and two layers can
reduce the reflection up to 3 percent in desired range of wavelengths.
Fig 1.1 A Typical n-on-p-photovoltaic
Generally, Arcs are produced on the solar cell by vacuum evaporation process and the
coatings which are tried are SiO2, SiO, Al2O3, TiO2, Ta2O5 and Si3N4. Other methods of
deposition are sputtering, spin-on, spray-on or screen printing. Only the vacuum evaporation
sputtering give good results but are expensive. The average reflection can be further reduced
by using two antireflective coatings instead of one where the outside (exposed side) coating
has an index of refraction 1.3 to 1.6 and the second layer between silicon and the first layer
has an index of refraction 2.2 to 2.6. This two layer ARC gives a better impedance match
between the index of silicon and the index of air.
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Fig1.2 Reflective coating
SOLAR TRACKER
A solar trackeris a device that orients a payload toward the sun. Payloads can
bephotovoltaic panels,reflectors, lenses or other optical devices.
In flat-panelphotovoltaic (PV) applications, trackers are used to minimize theangle
of incidencebetween the incoming sunlight 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 was predicted in 2008-2009 that trackers could be used
in at least 85% of commercial installations greater than 1MW from 2009 to 2012. However,
as of April 2014, there is no any data support these predictions.
Inconcentrated photovoltaic (CPV) andconcentrated 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. Trackingsystems are found in all concentrator applications because such systems do not produce
energy unless pointed at the sun.
Sunlight has two components, the "direct beam" that carries about 90% of the solar
energy, and the "diffuse sunlight" that carries the remainder - the diffuse portion is the bluesky on a clear day and increases proportionately on cloudy days. As the majority of the
energy is in the direct beam, maximizing collection requires the sun to be visible to the
panels as long as possible.
The energy contributed by the direct beam drops off with thecosine of the angle
between the incoming light and the panel. In addition, the reflectance (averaged acrossallpolarizations)is approximately constant for angles of incidence up to around 50, beyond
which reflectance degrades rapidly.
I Lost = 1 -cos(i) i Hours Lost
http://en.wikipedia.org/wiki/Solar_panelhttp://en.wikipedia.org/wiki/Photovoltaicshttp://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Concentrated_photovoltaicshttp://en.wikipedia.org/wiki/Concentrated_solar_powerhttp://en.wikipedia.org/wiki/Concentrated_solar_powerhttp://en.wikipedia.org/wiki/Solar_irradiationhttp://en.wikipedia.org/wiki/Lambert%27s_cosine_lawhttp://en.wikipedia.org/wiki/Reflectancehttp://en.wikipedia.org/wiki/Polarization_(waves)http://en.wikipedia.org/wiki/Cosinehttp://en.wikipedia.org/wiki/Cosinehttp://en.wikipedia.org/wiki/Polarization_(waves)http://en.wikipedia.org/wiki/Reflectancehttp://en.wikipedia.org/wiki/Lambert%27s_cosine_lawhttp://en.wikipedia.org/wiki/Solar_irradiationhttp://en.wikipedia.org/wiki/Concentrated_solar_powerhttp://en.wikipedia.org/wiki/Concentrated_solar_powerhttp://en.wikipedia.org/wiki/Concentrated_photovoltaicshttp://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Angle_of_incidencehttp://en.wikipedia.org/wiki/Photovoltaicshttp://en.wikipedia.org/wiki/Solar_panel7/27/2019 Solar tracker project
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0 0% 15 1 3.4%
1 0.015% 30 2 13.4%
3 0.14% 45 3 30%
8 1% 60 4 >50%
23.4[8]
8.3% 75 5 >75%
TRACKERS
Even though a fixed flat-panel can be set to collect a high proportion of availablenoon-time energy, significant power is also available in the early mornings and late
afternoonswhen the misalignment with a fixed panel becomes excessive to collect a
reasonable proportion of the available energy. For example, even when the Sun is only 10
above the horizon the available energy can be around half the noon-time energy levels (oreven greater depending on latitude, season, and atmospheric conditions).
Thus the primary benefit of a tracking system is to collect solar energy for the longest
period of the day, and with the most accurate alignment as the Sun's position shifts with the
seasons.
In addition, the greater the level of concentration employed, the more important
accurate tracking becomes, because the proportion of energy derived from direct radiation is
higher, and the region where that concentrated energy is focused becomes smaller.
DISADVANTAGES
Trackers add cost and maintenance to the system - if they add 25% to the cost, andimprove the output by 25%, the same performance can be obtained by making the system25% larger, eliminating the additional maintenance.
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ANGLES AFFECTING SOLAR ENERGY COLLECTION
In solar radiation analysis, the following angles are useful:
l= latitude of location
= declination
= hour angle
s = solar azimuth angle
s = slope
= altitude angle
z= zenith angle
INCIDENT ANGLE
If is the angle between an incident beam radiation I and the normal to the plane
surface, then the equivalent flux or radiation intensity falling normal to the surface is given by
Icos, where is called incident angle.
LATITUDE OF LOCATION
The altitude1 of a point or location is the angle made by the radial line joining the
location to the centre of the earth with the projection of the line on the equatorial plane.it isthe angular distance north or south of the equator measured from centre of the earth.
DECLINATION ANGLE
The declination is the angular distance of the suns rays north (or south) of the
equator. It is the angle between a line extending from the centre of the sun to the centre of the
earth and the projection of this line upon the earths equatorial plane.
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( in degrees) = 23.45
..(1)
where n is the day of the year
HOUR ANGLE
The hour angle is the angle through which the earth must turn to bring the meridian
of a point directly in line with the suns rays. The hour angle is equivalent to 15per hour.
It is measured from noon based on the local solar time (LST) or local apparent time, being
positive in the morning and negative in the afternoon.
ALTITUDE ANGLE (SOLAR ALTITUDE)
It is a vertical angle between the projection of the suns rays on the horizontal plane
and the direction of suns rays.
ZENITH ANGLE (Z)
It is complimentary angle of suns altitude angle. It is a vertical angle between the
suns rays and a line perpendicular to the horizontal plane through the point i.e. the angle
between the beam from the sun and the vertical
z = /2
SOLAR AZIMUTH ANGLE (s): It is the solar angle in degrees along the horizon
east or west of north or it is a horizontal angle measured from north to the horizontal
projection of the suns rays. This angle is positive when measured west wise.
Altitude angle , zenith angle z, and solar azimuth angle s, can be expressed in
terms of 1 (latitude angle), (declination), and (hour angle), which are also called basic
angles. The expressions are:
Cos z =cos cos cos +sin sin ..(2)
Cos s=sec (cos sin - cos sin cos ) ..(3)
And
sin s= sec cos sin ..(4)
These equations allow calculation of the suns zenith altitude and azimuth angles,
if the declination, hour angles and latitude are known. In applying these equations, attention
must be given to correct signs for the latitude and declination and angle. If north latitudes are
considered positive and south latitudes negative, the declination will be positive for the
summer period between the vernal equinox and autumnal equinox ( march 22 to September
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22 approximately ) and negative at other times. For non-horizontal surfaces, the other angles,
such as incident angle, slope angle, surface azimuth angle, etc. are important angles.
THE SLOPE(s)
It is the angle made by the plane surface with the horizontal. It is taken to be positivefor surfaces slopping towards the south and negative for surface slopping towards the north.
SURFACE AZIMUTH ANGLE()
It is the angle of deviation of the normal to the surface from the local meridian, the
zero point being south, east positive and west negative.
INCIDENT ANGLE()
It is the angle being measured between the beam of rays and normal to the plane.
From spherical geometry the relation between and other angles is given by theequation
Cos = sin 1 (sin cos s + cos cos cos sin s )
+cos 1 (cos cos cos s - sin cos sin s )
+ cos sin sin sin s ..(5)
Where 1 = latitude (north positive)
= declination (north positive)
= hour angle, it is positive between solar mid-night and noon, otherwise negative.
At solar noon being zero and each hour angles equating 15 of longitude with
morning positive and afternoon negative (e.g. =+ 15for 11:00and = -37.5 for 14:30) hour
angle can be expressed mathematically as :
= 15(12 LST)
Simpler versions of equation (5) are normally required. Some of these are as follows :
For vertical surfaces, s =90,equation (5) becomes
Cos = sin cos cos cos - cos sin cos +cos sin sin ..(6)
For horizontal surfacess=0, = z zenith angle
Cos z = sin sin + cos cos cos ..(7)
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= sin
i.e. cos = cosz =sin ..(8)
for surface facing due south = 0,
Cos T= sin (sin cos s+ cos cos sin s)
= cos (cos cos cos s sin sin s)
(incident angle is expressed as T, denoting the surface as tilted one)
= sin sin( - s) + cos cos cos( -s) ..(9)
Vertical surfaces facing due south (s=90, =0)
Cos z =sin cos cos cos sin ..(10)
Day length at the timeof sun rise or sun set, the zenith angle, z = 90, substituting this in
equation(2), we obtain sun rise hour angle (s)
Coss = -
= - tan tan
s = .(11)
since 15 of the hour angle are equivalent to 1 hour, the day length (in hours)
td =
=
..(12)
Therefore, the length of the day (td) is a function of latitude and solar declination.
The hour angle at sun rise or sun set on an inclined surface will be lesser than the
value obtained by equation (12), if the corresponding incidence angle comes out to be more
than 90. Under this condition, by putting = 90, in equation (5) or one of its simple
versions. Thus for an inclined surface facing south substituting = 90, in equation (9), we
obtain
st = ..(13)
the corresponding day length ( in hours) is then given by
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td =
..(14)
EQUIPMENT
FRAME:
Frame is the supporting structure for the solar panel. Also it is useful for orienting
the panel in any angle. The frame is made up of cast iron and I-section is used.
There are two standard I-beam forms:
Rolled I-beam, formed by hot rolling, cold rolling or extrusion (depending on
material).
Plate girder, formed bywelding (or occasionallybolting orriveting)plates.
I-beams are commonly made ofstructural steelbut may also be formed fromaluminum
or other materials.
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DESIGN
Fig 3.1 Isection
I-beams are widely used in theconstruction industry and are available in a variety of
standard sizes. Tables are available to allow easy selection of a suitable steel I-beam size for
a given applied load. I-beams may be used both as beams and ascolumns.
I-beams may be used both on their own, or actingcompositely with another material,
typicallyconcrete.Design may be governed by any of the following criteria:
deflection:thestiffness of the I-beam will be chosen to minimize deformation
vibration: the stiffness and mass are chosen to prevent unacceptable vibrations,
particularly in settings sensitive to vibrations, such as offices and libraries
bending failure by yielding:where the stress in the cross section exceeds the yield
stress
bending failure bylateral tensional buckling:where a flange in compression tends to
buckle sideways or the entire cross-section buckles torsionally
bending failure bylocal buckling:where the flange or web is so slender as to buckle
locally
local yield: caused by concentrated loads, such as at the beam's point of support
shear failure:where the web fails. Slender webs will fail by buckling, rippling in a
phenomenon termed tension field action, but shear failure is also resisted by the
stiffness of the flanges
http://en.wikipedia.org/wiki/Construction_industryhttp://en.wikipedia.org/wiki/Columnhttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Deflection_%28engineering%29http://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Masshttp://en.wikipedia.org/wiki/Yield_%28engineering%29http://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Yield_stresshttp://en.wikipedia.org/wiki/Yield_stresshttp://en.wikipedia.org/wiki/Buckling#Lateral-torsional_bucklinghttp://en.wikipedia.org/wiki/Buckling#Local_bucklinghttp://en.wikipedia.org/w/index.php?title=Shear_failure&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Shear_failure&action=edit&redlink=1http://en.wikipedia.org/wiki/Buckling#Local_bucklinghttp://en.wikipedia.org/wiki/Buckling#Lateral-torsional_bucklinghttp://en.wikipedia.org/wiki/Yield_stresshttp://en.wikipedia.org/wiki/Yield_stresshttp://en.wikipedia.org/wiki/Stress_%28physics%29http://en.wikipedia.org/wiki/Yield_%28engineering%29http://en.wikipedia.org/wiki/Masshttp://en.wikipedia.org/wiki/Vibrationhttp://en.wikipedia.org/wiki/Stiffnesshttp://en.wikipedia.org/wiki/Deflection_%28engineering%29http://en.wikipedia.org/wiki/Concretehttp://en.wikipedia.org/wiki/Composite_materialhttp://en.wikipedia.org/wiki/Columnhttp://en.wikipedia.org/wiki/Construction_industry7/27/2019 Solar tracker project
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buckling or yielding of components: for example, of stiffeners used to provide
stability to the I-beams web.
In this instrument I-section is used to support the solar panel
2.1 MOTOR
Dc motors tend to spin too quickly and do not have enough torque to drive directly,
so some kind of gear reduction will have to be used. The gears both slow down the speed and
increase the torque of the output shaft. This gearbox can be created out of individual gears or
it can be part of the motor. By knowing the output shaft's speed (RPM) and the diameter of
the wheel you will be using, you can get an idea of how fast your mouse will be traveling
through the maze.
Fig 2.1 Stepper motor
Specifications:
Speed = 1000 rpm
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2.4.3.3 SOLAR PANEL
Photovoltaic cells are devices that absorb sunlight and convert that solar energy into
electrical energy. Solar cells are commonly made of silicon, one of the most abundant
elements on Earth. Pure silicon, an actual poor conductor of electricity, has four outer
valence electrons that form tetrahedral crystal lattices.
Fig 2.10Solar panel
When photons (sunlight) hit a solar cell, its energy frees electron-holes pairs. The
electric field will send the free electron to the N side and holes to the P side. This causes
further disruption of electrical neutrality, and if an external current path is provided, electrons
will flow through the path to their original side (the P side) to unite with holes that the
electric field sent there, doing work for us along the way. The electron flow provides the
current, and the cell's electric field causes a voltage. With both current and voltage, we have
power, which is the product of the two. By wiring solar cells in series, the voltage can be
increased; or in parallel, the current. Solar cells are wired together to form a solar
panel. Solar panels can be joined to create a solar array
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Fig 2.12 Working
The performance of a photovoltaic array is dependent upon sunlight. Climate
conditions (e.g., clouds, 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.
In our project, we used a solar panel of
Dimensions:
Surface area:
The characteristics of the solar cell array are as below:
Type of semi-conductor used for cell : silicon
Number of arrays : 2
Power : 36 watt x 2 = 72 watt Open circuit voltage : 21V
Short circuit current : 3.6 ampere
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2.2 INVERTER
So how can an inverter give us a high voltage alternating current from a low voltage
direct current? Let's first consider how an alternator produces an alternating current. In its
simplest form, an alternator would have a coil of wire with a rotating magnet close to it. As
one pole of the magnet approaches the coil, a current will be produced in the coil. This
current will grow to a maximum as the magnet passes close to the coil, dying down as the
magnetic pole moves further away. However when the opposite pole of the magnet
approaches the coil, the current induced in the coil will flow in the opposite direction.
Fig 2.3INVERTER
As this process is repeated by the continual rotation of the magnet, an alternating
current is produced. Now letsconsider what a transformer does. A transformer also causes
an electric current to be induced in a coil, but this time, the changing magnetic field is
produced by another coil having an alternating current flowing through it. Any coil with an
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electric current flowing through it will act like a magnet and produce a magnetic field .If the
direction of the current changes then the polarity of the field changes.
Now, the handy thing about a transformer is that, the voltage produced in the
secondary coil is not necessarily the same as that applied to the primary coil. If the secondary
coil is twice the size (has twice the number of turns) of the primary coil, the secondary
voltage will be twice that of the voltage applied to the primary coil. We can effectively
produce whatever voltage we want by varying the size of the coils.
Fig 2.4 Step up transformer
If we connected a direct current from a battery to the primary coil it would not induce
a current in the secondary as the magnetic field would not be changing. However, if we can
make that direct current effectively change direction repeatedly, then we have a very basic
inverter. This inverter would produce a square wave output as the current would be changingdirection suddenly.
Fig 2.5 Inverter
This type of inverter might have been used in early car radios that needed to take 12
volts available in the car and produce the higher voltages required to run radio valves (known
as tubes in America) in the days before transistors were widely used.
A more sophisticated inverter would use transistors to switch the current. The switching
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transistors are likely to be switching a small current which is then amplified by further
transistor circuitry. This will still be a square wave inverter
2.3 MICROCONTROLLER
Microcontroller is a complete microprocessor system built on a single IC.
Microcontrollers were developed to meet a need for microprocessors to be put into low cost
products. Building a complete microprocessor system on a single chip substantially reduces
the cost of building simple products, which use the microprocessor's power to implement
their function, because the microprocessor is a natural way to implement many products.
This means the idea of using a microprocessor for low cost products comes up often. But the
typical 8-bit microprocessor based system, such as one using a Z80 and 8085 is expensive.
Both 8085 and Z80 system need some additional circuits to make a microprocessor system.
Each part carries costs of money. Even though a product design may require only very simple
system, the parts needed to make this system as a low cost product.
Fig 2.6Microconroller
2.3.1 APPLICATION OFMICROCONTROLLER
Microcontrollers are designed for use in sophisticated real time applications such as
1. Industrial Control
2. Instrumentation and
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3. Intelligent computer peripherals
They are used in industrial applications to control
Motor
Robotics
Discrete and continuous process control
In missile guidance and control
In medical instrumentation
Oscilloscopes
Telecommunication
Automobiles
For scanning a keyboard
Driving an LCD
For Frequency measurements
Period Measurements
2.3.2 PIC16F877 MICROCONTROLLER FEATUTRE
1. High performance RISC CPU
2. Only 35 single word instructions to learn
3. All single cycle instructions except for program branches which are two cycle
4.
Up to 8K x 14 words of FLASH Program Memory, Up to 368 x 8 bytes ofData Memory (RAM) up to 256 x 8 bytes of EEPROM Data Memory
5. Interrupt capability (up to 14 sources)
6. Direct, indirect and relative addressing modes
7. Power-on Reset (POR)
8. Power-up Timer (PWRT) and Oscillator Start-up Timer (OST)
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9. Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation
10.Programmable code protection
11.Power saving SLEEP mode
12.Selectable oscillator options
13.Low power, high speed CMOS FLASH/EEPROM technology
14.Fully static design
15.In-
16.Single 5V In-Circuit Serial Programming capability
17.In-Circuit Debugging via two pins
18.Processor read/write access to program memory
19.Wide operating voltage range: 2.0V to 5.5V
20.
High Sink/Source Current: 25 mA
21.Commercial, Industrial and Extended temperature ranges
2.3.3 PIN DIAGRAM
Fig2.7 Microcontroller block diagram
2.4 BATTERY
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In most alone PV power systems, storage batteries with charge regulators have to be
incorporated to provide a backup power source during periods of low solar irradiance and
night. Several types of accumulator are available in the market for use in PV power systems.
The main requirements to be met by an accumulator for solar power system are,
Ability to withstand several charge/discharge cycle.
A low self-discharge rate
Little or no need for maintenance
Fig 2.8 Battery
The capacity of a battery is the total amount of electricity that can be drawn from afully charged battery at a fixed discharge rate and electrolyte temperature until the voltage
falls to a specified minimum. It is expressed in ampere hour. The capacity of the battery also
depends upon the temperature and age of battery.
The batteries in most PV systems are of lead acid type consisting of one or more 2v
cells. Each cell has a positive plate of lead peroxide and a negative plate of sponge lead. The
electrolyte is dilute sulphuric acid. During discharging when current is drawn from it, the
material of both plates changes to lead sulphate and water content in the electrolyteincreases thereby reducing its specific gravity.
When the battery is charged by passing electric current through it in the opposite
direction, the reverse chemical reaction takes place. The cell voltages are typically 2.4v and
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1.9v for fully charged and deeply discharged battery respectively. Lead acid batteries self-
discharge slowly when not in use.
The characteristics of the battery are as below:
Type : Lead acid tubular battery
Ampere hour efficiency : 90 to 95%
Watt hour efficiency : 70 to 80%
Capacity: 7 AH, 12V.
2.4.1 CHARGE CONTROLLER
Overcharging of some batteries results in loss of electrolytic, corrosion, plate growth
and loss of active material from the plates, causing reduction in battery life. Also, therepeated failure to reach full charge also leads to stratification of electrolyte.
Thus, there is a need of charge regulators to optimize the battery life. Most charge
regulators start the charging process with a high current and reduce it to a very low level
when a certain battery voltage is reached. A digital based charge regulator monitors the
battery current, and voltage computes the level of charge and regulates the input and output
currents so as to avoid both overcharging and excessive discharge. LOAD For continuous
operation, we use solar cells for charging DC LAMP.
The characteristics of controller are as below:
Low voltage cut off
Over charge disconnect
Operating current : 10 ampere
High copper rich 10amp wire for minimum power loss is used for connections in the circuit.
2.4.3.1ADVANTAGES OF CHARGING/DISCHARGING
(1) Protect unit from reverse connection of battery
(2) Solar cell Polarity reversal
(3) Battery short circuit Protection (Electronic Fuse)
(4) Color all overload Protection
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(5) Battery charge level maintenance
(6) Battery discharge limit
2.4.3.2 ABSENCE OF CHARGING/DISCHARGING UNIT CAUSE
1)
Solar cell may get affected due to over loading.
2) Battery life shortened
2.4.4PROGRAM OF MICROCONTROLLER
#include
#include
#include
#include"lcd.h"
#include"delay.h"
#include"adc.h"
#define G1 RB1
#define B1 RB2
#define M1 RB7
#define M2 RB6
#define SW2 RB5
#define SW3 RB4
#define _LEGACY_HEADERS
__CONFIG(FOSC_HS & PWRTE_OFF & CPD_OFF & CP_OFF& BOREN_OFF &
DEBUG_OFF & WDTE_OFF & LVP_OFF);
unsigned char Temp _dat=0,count_num=0,Temp_Arr[6];
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unsigned char x,d1,d2,d3,count=0,time=0;
void rf_tx(unsigned char a);
void convert(unsigned char binbyte)
{
x =binbyte/10;
d1=(binbyte%10)+48;
d2=(x%10)+48;
d3=(x/10)+48;
}
void main()
{
unsigned char adc_value=0,adc_value2=0;
static unsigned char q,f;
TRISB = 0b00011111;
PORTB = 0xFF;
TRISC = 0b10010000;
PORTC = 0xff;
lcd_init();
DelayMs(50);
init_adc();
// serial_setup();
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lcdcmd(0x80);
lcd_puts("Monitoring . . .");
while(1)
{
lcd_clear();
lcdcmd(0x80);
lcd_puts("Monitoring . . .");
adc_value = adc_read(0);
adc_value = (adc_value /10);
convert(adc_value);
lcdcmd(0xC0);
lcd_puts("V:");
lcddata(d3);
lcddata(d2);
lcddata(d1);
lcddata(' ');
DelayMs(50);
do
{
M1 = 1;
M2 = 0;
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adc_value = adc_read(0);
adc_value = (adc_value /10);
convert(adc_value);
lcdcmd(0xC0);
lcd_puts("V:");
lcddata(d3);
lcddata(d2);
lcddata(d1);
lcdcmd(0xCF);
lcddata('F');
DelayS(1);
if(adc_value>=9)
{
M1 = 0;
M2 = 0;
DelayMs(250);
break;
}
}
while(G1!=0);
count=0;
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DelayS(1);
do
{
M1 = 0;
M2 = 1;
adc_value = adc_read(0);
adc_value = (adc_value /10);
convert(adc_value);
lcdcmd(0xC0);
lcd_puts("V:");
lcddata(d3);
lcddata(d2);
lcddata(d1);
lcdcmd(0xCF);
lcddata('R');
DelayS(1);
if(adc_value>=9)
{ // motor stop
M1 = 0;
M2 = 0;
DelayMs(250);
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break;
}
}while(B1!=0);
while(adc_value>=6)
{
M1 = 0;
M2 = 0;
DelayMs(250);
adc_value = adc_read(0);
adc_value = (adc_value /10);
convert(adc_value);
lcdcmd(0xC0);
lcd_puts("V:");
lcddata(d3);
lcddata(d2);
lcddata(d1);
lcd_clear();
lcdcmd(0x80);
lcd_puts("PANEL STOPPED ");
lcdcmd(0xC0);
lcd_puts("ABOVE 9V ");
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}
while(adc_value
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}
}
3.3 BALL BEARING
Ball bearing are extremely common because they can handle both radial and thrust
loads, but can only handle a small amount of weight. They are found in a wide array of
applications, such as roller blades and even hard drives, but are prone to deforming if they
are overloaded.
These are used for the free rotation of the components
Fig 3.4Ball bearing
TRACKING ALTERNATIVES
The movement of most modern heliostats employs a two-axis motorized system,
controlled by computer as outlined at the start of this article. Almost always, the primaryrotation axis is vertical and the secondary horizontal, so the mirror is on analt-azimuth
mount.
One simple alternative is for the mirror to rotate around apolar alignedprimary axis,driven by a mechanical, often clockwork, mechanism at 15 degrees per hour, compensating
for the earth's rotation relative to the sun. The mirror is aligned to reflect sunlight along the
same polar axis in the direction of one of thecelestial poles. There is a perpendicularsecondary axis allowing occasional manual adjustment of the mirror (daily or less often as
necessary) to compensate for the shift in the sun'sdeclination with the seasons. The setting of
the drive clock can also be occasionally adjusted to compensate for changes in theEquation
of Time.The target can be located on the same polar axis that is the mirror's primary rotationaxis, or a second, stationary mirror can be used to reflect light from the polar axis toward the
target, wherever that might be. This kind of mirror mount and drive is often used withsolar
cookers,such asScheffler reflectors.[11][12][13]
For this application, the mirror can beconcave,
so as to concentrate sunlight onto the cooking vessel.
The alt-azimuthand polar-axisalignments are two of the three orientations for two-
axis mounts that are, or have been, commonly used for heliostat mirrors. The third is
thetarget-axisarrangement in which the primary axis points toward the target at which
http://en.wikipedia.org/wiki/Altazimuth_mounthttp://en.wikipedia.org/wiki/Altazimuth_mounthttp://en.wikipedia.org/wiki/Polar_alignmenthttp://en.wikipedia.org/wiki/Celestial_polehttp://en.wikipedia.org/wiki/Declinationhttp://en.wikipedia.org/wiki/Equation_of_Timehttp://en.wikipedia.org/wiki/Equation_of_Timehttp://en.wikipedia.org/wiki/Solar_cookerhttp://en.wikipedia.org/wiki/Solar_cookerhttp://en.wikipedia.org/wiki/Solar_energy#Cookinghttp://en.wikipedia.org/wiki/Heliostat#cite_note-11http://en.wikipedia.org/wiki/Heliostat#cite_note-11http://en.wikipedia.org/wiki/Heliostat#cite_note-13http://en.wikipedia.org/wiki/Heliostat#cite_note-13http://en.wikipedia.org/wiki/Curved_mirror#Concave_mirrorshttp://en.wikipedia.org/wiki/Curved_mirror#Concave_mirrorshttp://en.wikipedia.org/wiki/Heliostat#cite_note-13http://en.wikipedia.org/wiki/Heliostat#cite_note-11http://en.wikipedia.org/wiki/Heliostat#cite_note-11http://en.wikipedia.org/wiki/Solar_energy#Cookinghttp://en.wikipedia.org/wiki/Solar_cookerhttp://en.wikipedia.org/wiki/Solar_cookerhttp://en.wikipedia.org/wiki/Equation_of_Timehttp://en.wikipedia.org/wiki/Equation_of_Timehttp://en.wikipedia.org/wiki/Declinationhttp://en.wikipedia.org/wiki/Celestial_polehttp://en.wikipedia.org/wiki/Polar_alignmenthttp://en.wikipedia.org/wiki/Altazimuth_mounthttp://en.wikipedia.org/wiki/Altazimuth_mount7/27/2019 Solar tracker project
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sunlight is to be reflected. The secondary axis is perpendicular to the primary one. Heliostats
controlled by light-sensors have used this orientation. A small arm carries sensors that
control motors that turn the arm around the two axes, so it points toward the sun. (Thus thisdesign incorporates a solar tracker.) A simple mechanical arrangement bisects the angle
between the primary axis, pointing to the target, and the arm, pointing to the sun. The mirror
is mounted so its reflective surface is perpendicular to this bisector. This type of heliostat wasused fordaylightingprior to the availability of cheap computers, but after the initialavailability of sensor control hardware.
There are heliostat designs which do not require the rotation axes to have any exact
orientation. For example, there may be light-sensors close to the target which send signals to
motors so that they correct the alignment of the mirror whenever the beam of reflected lightdrifts away from the target. The directions of the axes need be only approximately known,
since the system is intrinsically self-correcting. However, there are disadvantages, such as
that the mirror has to be manually realigned every morning and after any prolonged cloudy
spell, since the reflected beam, when it reappears, misses the sensors, so the system cannotcorrect the orientation of the mirror. There are also geometrical problems which limit the
functioning of the heliostat when the directions of the sun and the target, as seen from themirror, are very different. Because of the disadvantages, this design has never beencommonly used, but some people do experiment with it.
2/3rd motion heliostat:
In general, in heliostats, the bisector angular motion of the mirror moves at a rate that
is 1/2 the angular motion of the sun. There is another arrangement that satisfies the definition
of a heliostat yet has a mirror motion that is 2/3rd of the motion of the sun. For want of abetter term, I have called this a 2/3rd motion heliostat.
Many other types of heliostat have also occasionally been used. In the very earliest
heliostats, for example, which were used for daylighting in ancient Egypt, servants or slaves
kept the mirrors aligned manually, without using any kind of mechanism. (There are placesin Egypt where this is done today, for the benefit of tourists.) Elaborate clockwork heliostats
were made during the 19th Century which could reflect sunlight to a target in any direction
using only a single mirror, minimizing light losses, and which automatically compensated forthe sun's seasonal movements. Some of these devices are still to be seen in museums, but
they are not used for practical purposes today. Amateurs sometimes come up with ad
hocdesigns which work approximately, in some particular location, without any theoretical
justification. An essentially limitless number of such designs are possible.
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OPERATION
The main aim of our project is to maximize the power output generated by the solar
panel using microcontroller
Firstly we have to switch on the microcontroller by using the power stored in the
battery
This microcontroller samples the output of the solar cell to detect maximum power
Stepper motor is having rotating motion which converts into oscillating motion by
means of beam engine principle
This stepper motor gets power from battery which stored previously in it
The oscillating motion provides to solar panel to absorb the solar energy from the sun
The output power generates from the solar panel will displayed on the LCD display
Microcontroller test the output using the program given to it
The microcontroller is programmed based on embedded C
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The instructions given to it based on maximum cut-off range of power generation
If the radiation of the light is below 9 volts then the solar panel will rotate
continuously to track the maximum solar energy under the sun light
If the LCD display shows 9volts then the solar panel stops rotating and fixed in that
position
The power generated by means of photovoltaic process
Photovoltaic is the direct conversion of light into electricity at the atomic level.
Sunlight is composed of photons are particles of solar energy
When these photons strike a photovoltaic cell they may be reflected, pass light
through or be absorbed
Only the absorbed photons provide energy to generate power
This generated power is stored in the battery bank which is used for several purposes
PERFORMANCE CALCULATION
for example,
in Kavali, latitude angle,
on may 10th
, day of the year, n = 31+28+31+30+10 = 130
at 10:30 AM, hour angle, = +22.5
declination angle, = 23.45
= 23.45
= 17.5164
For horizontal surfacess=0, = z zenith angle
Cos z = sin sin + cos cos cos
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= sinsin 17.5164 + cos 17.5164 cos cos 22.5
= 0.9288
z=
= 21.75
Also day length, td =
=
= 12.64 hours
= 12 hrs 38min 24 sec
In case of microcontroller
The amount of electricity developed per hour = 6watts
The amount of electricity developed Per day = 612.64
= 75.84 W
The amount of electricity developed Per month = 75.8430
= 2275.2 W
The 18 watts bulb is works =75.84/18
= 4.21 hrs
By convention, solar cell efficiencies are measured under standard test conditions
(STC).. STC specifies a temperature of 25 C and an irradiance of 1000 W/m2with an
air mass 1.5 (AM1.5) spectrum. These conditions correspond to a clear day with
sunlight incident upon a sun-facing 37-tilted surface with the sun at an angle of
41.81 above the horizon.[2][3]
This represents solar noon near the spring and autumn
equinoxes in the continental United States with surface of the cell aimed directly at
the sun. Under these test conditions a solar cell of 20% efficiency with a
100 cm2(0.01 m
2) surface area would produce 2.0W.
The microcontroller used power =320 mA
Motor required power = 12 volts
Totals power required for controller and motor = 120.320
http://en.wikipedia.org/wiki/Solar_cell_efficiency#cite_note-2http://en.wikipedia.org/wiki/Solar_cell_efficiency#cite_note-2http://en.wikipedia.org/wiki/Solar_cell_efficiency#cite_note-2http://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Solar_cell_efficiency#cite_note-2http://en.wikipedia.org/wiki/Solar_cell_efficiency#cite_note-27/27/2019 Solar tracker project
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= 3.84 watts
Then total power developed in solar panel = 75.84-3.84
= 72 W/day
Appliance Watts Appliance Watts Appliance Watts
Central Air Conditioner
NA5,000 Electric blanket 200 Hedge trimmer 450
Electric Clothes Dryer NA 3,400 Shaver 15 Weed eater 500
Oven 3,000 Waterpik 100 1/4 drill 250
Hair Dryer 1,538 Well Pump (1/3-1
HP)
480-
12001/2 drill 750
Dishwasher1200-
1500Laptop
60-
2501 drill 1000
Coffee Machine 1,500 Plasma TV 339 9 disc sander 1200
Microwave 1,500 LCD TV 213 3 belt sander 1000
Popcorn Popper 1,400 25 color TV 150 12 chain saw 1100
Toaster oven 1,200 19 color TV 70 14 band saw 1100
Hot Plate 120012 black and
white TV20
7-1/4 circular
saw900
Iron 1,100 Stereo 10-308-1/4 circular
saw1400
Toaster 1,100 Satellite dish 30 Refrigerator/Freezer**
Microwave500-
1500
Radiotelephone
Receive5 20 cu. ft. (AC)
1411 watt-
hours/day*
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Room Air Conditioner NA 1,100Radiotelephone -
Transmit
40-
15016 cu. ft. (AC)
1200 watt-
hours /day*
Vacuum Cleaner 500 Lights Freezer
Water heater 479100 watt
incandescent bulb100
15 cu. ft.
(Upright)
1240 watt-
hours /day*
Sink Waste Disposal 45025 watt compact
fluor. bulb28 15 cu. ft. (Chest)
1080 watt-
hours /day*
Espresso Machine 36050 watt DC
incandescent50
Cell Phone
recharge2-4 watts
Dehumidifier 350 40 watt DChalogen
40 MP3 Player recharge
.25-.40watts
Blender 30020 watt DC
compact fluor.22
* TVs,VCRs and other
devices left plugged in, but not
turned on, still draw power.
**To estimate the number of
hours that a refrigeratoractually operates at its
maximum wattage, divide the
total time the refrigerator is
plugged in by three.
Refrigerators, although turned
"on" all the time, actually
cycle on and off as needed to
maintain interior temperatures.
Humidifier300-
1000
CFL Bulb (60-
watt equivalent)18
Video Game Player 195
CFL Bulb (40-
watt equivalent) 11
Standard TV 188CFL Bulb (75-
watt equivalent)20
Monitor 150CFL Bulb (100-
watt equivalent)30
Computer 120 Heaters***
Portable Fan 100Engine Block
Heater NA
150-
1000
Ceiling Fan 100Portable Heater
NA1500
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Can Opener 100Waterbed Heater
NA400
Curling Iron 90Stock Tank
Heater NA
100
Stereo 60 Furnace Blower300-
1000
Cable Box 20Clothes Dryer -
Gas Heated
300-
400
Clock Radio 7Well Pump (1/3-
1HP)
480-
1200
Table 5.1
WELDING
7.1 ARC WELDING
Arc welding is one of several fusion processes for joining metals. By applying intense
heat, metal at the joint between two parts is melted and caused to intermix - directly, or more
commonly, with an intermediate molten filler metal. Upon cooling and solidification, a
metallurgical bond is created. Since the joining is an intermixture of metals, the final
weldment potentially has the same strength properties as the metal of the parts. This is in
sharp contrast to non-fusion processes of joining (i.e. soldering, brazing etc.) in which the
mechanical and physical properties of the base materials cannot be duplicated at the joint.
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7.1 The basic arc-welding circuit
In arc welding, the intense heat needed to melt metal is produced by an electric arc.
The arc is formed between the actual work and an electrode (stick or wire) that is manually
or mechanically guided along the joint. The electrode can either be a rod with the purpose of
simply carrying the current between the tip and the work. Or, it may be a specially prepared
rod or wire that not only conducts the current but also melts and supplies filler metal to the
joint. Most welding in the manufacture of steel products uses the second type of electrode.
7.1.1BasicWeldingCircuit
The basic arc-welding circuit is illustrated in Fig. An AC or DC power source, fitted
with whatever controls may be needed, is connected by a work cable to the work piece and
by a "hot" cable to an electrode holder of some type, which makes an electrical contact with
the welding electrode.
An arc is created across the gap when the energized circuit and the electrode tip
touches the work piece and is withdrawn, yet still with in close contact.
The arc produces a temperature of about 6500F at the tip. This heat melts both the
base metal and the electrode, producing a pool of molten metal sometimes called a "crater."
The crater solidifies behind the electrode as it is moved along the joint. The result is a fusion
bond.
7.1.2ArcShielding
However, joining metals requires more than moving an electrode along a joint. Metals
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at high temperatures tend to react chemically with elements in the air - oxygen and nitrogen.
When metal in the molten pool comes into contact with air, oxides and nitrides form which
destroy the strength and toughness of the weld joint. Therefore, many arc-welding processes
provide some means of covering the arc and the molten pool with a protective shield of gas,
vapor, or slag. This is called arc shielding. This shielding prevents or minimizes contact of
the molten metal with air. Shielding also may improve the weld. An example is a granular
flux, which actually adds deoxidizers to the weld.
7.1.2 This shows how the coating on a coated (stick) electrode
provides a gaseous shield around the arc and a slag covering on the
hot weld deposit.
Figure illustrates the shielding of the welding arc and molten pool with a Stick
electrode. The extruded covering on the filler metal rod, provides a shielding gas at the pointof contact while the slag protects the fresh weld from the air.
The arc itself is a very complex phenomenon. In-depth understanding of the physics
of the arc is of little value to the welder, but some knowledge of its general characteristics
can be useful.
7.2 SOLDERING
Solder is an alloy of tin and lead used for using metals relatively low temperature
about 260-315k the point where two metal conductors are to be fused is heated and then
solder is applied so that it can melt and cover the connection. The reason for soldering
connection is that it makes a good blend between the joined metals.
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Covering the joint completely is to prevent oxidation. The coating of solder provides
protection for practically an in definitive period of time. The trick in soldering is to heat the
joint, not the solder. When the joint is not enough to melt the solder the cracks, forming a
shifty cover without until the solder has set, which takes only a few seconds. Either a
soldering gun can be used, rated at 25-10,000. The gun is convenient for the intermittent
operation, since it heats almost instantaneously when for press the trigger. The small pencil
iron of 25-4,000 is helpful or small connections where excessive heat can cause damage.
This precaution is particularly important when working on PCB boards, where too much heat
can soften the plastic form and loosen the printed writing, a soldering iron for F&T devices
should have the tip ground to eliminate static charge. The three grades of solder, generally
used for electronics work are 40-60, 50-50, 60-40 solder. The 60-40 solders costs more but it
melts at the lowest temperature flows more freely takes less time to harder, and generally
makes it easier to do a soldering job. In addition to the solder there must be flux to move any
oxide film on the metals being joined otherwise they cannot fuse. The flux enables the
molten solder to wet the metals so that the solder can stick. The two types are acid flux and
rosin flux. Acid flux is more active in cleaning metals but is corrosive. Rosin flux is always
used for the light soldering work in making wire connection.
ADVANTAGES AND APPLICATIONS
1. Pollution free atmospheric condition due to the absence of smokes and fumes.
2. They have a long effective life.
3. They are highly reliable
4. They are working with freely available solar energy, hence fuel cost is zero.
5. Operating cost, maintenance costs are minimum as compared to the other type
of power generation systems.
6. They have wide power handling capability from Microwatts to Kilowatts or
even Megawatts. When modules are combined into large arrays. Solar cells
can be used in combination with power handling circuitry to feed power into
utility grid.
7. They have high power to weight ratio, this characteristic is more important for
space applications than terrestrial. For example the roof loading (or a house
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roof is covered with Solar cells), would be significantly lower than the
comparable loading for a conventional liquid solar water heater.
8. They can be installed easily in the required site without any power loss due to
transmission and costs of transmission lines are eliminated.
RESULTS
Solar cell produces electricity under the sunlight during the day
CONCLUSION
The project aids the conservation of the conventional fuel by partially using
the solar energy as described in the project work.
The main objective, to increase the usage of renewable energy source forpower generation is perfectly implemented. Taking into consideration the
future energy scenario in the world, solar energy would be a major energy
source.
REFERENCES
Non-conventional sources of Energy
By G.D. Rai
Solar Power Engineering
- By B.S. Magal
Solar EnergyThe Infinite source
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- By G.K.Ghosh
Direct Solar production of Electricity
- By Dr.L.W. Davies
Solar Energy
- HP. Garg
J. Prakash
Solar Engineering
- Duffee and Beckman