Mobile Main Report Doc

8/10/2019 Mobile Main Report Doc

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INTRODUCTION

Mobiles play an important role in peoples everyday life and lots of

communications are relayed through a mobile. The mobile charger is important

accessory for its trouble free and efficient usage of various mobile activities.

General problem that arises in mobile is quick discharge. While browsing the

features in mobile continuously, battery gets discharged quickly and in such cases

solar powered mobile chargers can be a better alternative to electrical mobile

chargers.

The solar charger can be powered via sun with a USB cable or directly to

the wall.

The utility of this development is mainly aimed at convenience of the user at

following limitations.

Not having charging adaptor

Not having electrical connections.

Not having sufficient sunlight.

The various advantages of using solar energy over electrical energy in chargingthe mobile are

It saves electrical energy.

It is pollution free, natural and free of cost.

Solar energy is renewable.

Solar energy is also abundant and

It prevents global warming.

The project outlines the manufacturing of solar charger to charge the mobile

using solar energy instead of electrical energy.


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1.PHOTOVOLTAIC CELL

1.1 INTRODUCTION

The early development of solar technologies started in the year 1860s was driven

by an expectation that coal would soon become scarce. However development of solar

technologies stagnated in the early 20th century in the face of the increasing availability,

economy, and utility of coal and petroleum.

The term "photovoltaic" comes from the Greek (photo) meaning "light", and

"voltaic", meaning electric, from the name of the Italian physicist VOLTAafter whom

a unit of electro-motive force, the volt is named. The term "photo-voltaic" has been in usein English since 1849.

In 1839, nineteen-year-old Edmund Becquerel, while experimenting with an

electrolytic cell made up of two metal electrodes found that certain materials would

produce small amounts of electric current when exposed to light. The photovoltaic cell

was developed in 1954 at Bell Laboratories.

The highly efficient solar cell was first developed by Daryl Chapin,

Calvin Souther Fuller and Gerald Pearson in 1954 using diffused silicon

p-n junction.

The sun is 150 million km from the earth and is 5 billion years old. The

temperature of the sun ranges from 6000 degrees Celsius at its surface to 10 million

degrees Celsius at its centre. It takes about 8 minutes for the light energy to touch the

earth.

The sun is a star made up of hydrogen and helium gas and it radiates an

enormous amount of energy every second and it is clean. Solar poweris the conversion

of sunlight into electricity either directly using photovoltaic (PV), or indirectly using

concentrated solar power (CSP). CSP systems use lenses or mirrors and tracking systemsto focus a large area of sunlight into a small beam. PV converts light into electric current

using the photoelectric effect.

Most commercially available solar cells are capable of producing electricity for at

least twenty years without a significant decrease in efficiency. The typical warranty given

by panel manufacturers is for a period of 25 30 years, wherein the output shall not fall

below a specified percentage (around 80%) of the rated capacity.


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1.2 PRINCIPLE OF PV CELL

Solar cell works on the principle of photovoltaic effect. Sunlight is composed of

photons, or "packets" of energy. These photons contain various amounts of energy

corresponding to the different wavelengths of light. When photons strike a solar cell, they

may be reflected or absorbed, or they may pass right through. When a photon is absorbed,

the energy of the photon is transferred to an electron in an atom of the cell (which is

actually a semiconductor). With its new found energy, the electron is able to escape from

its normal position associated with that atom to become part of the current in an electrical

circuit.

Each cell is made of two layers with a barrier in between them. The first layer(Layer A) contains electrons that are free to move to the second layer (Layer B). The

Layer B wants these electrons more than the first layer.

Layer A electrons will migrate to

Layer B automatically, no sunlight

needed. Layer B now has the extra

electrons. However, while layer B has a

better grip on these electrons that Layer

A, it can still lose them. This is due to

the pull of the nucleus on theelectrons. So when sunlight hits Layer

B the electrons are dislodged. Their

natural response is to try to go back to

the positively charged Layer A; they do

this because they can now move.

This is where the barrier layer

comes in. This is a one-way gate for the

electrons to go from Layer A to Layer

B but NOT the other way. The only way for the electrons to get back to Layer A isthrough the wire joining the two. So a photovoltaic solar cell or panel of cells will only

generate electricity if it is connected to a circuit; otherwise it will just heat up in the sun.

Once the electrons have done some work, they will have lost the energy that the

sunlight provided them with and they will return, exhausted, to Layer A where they go

back to their parent metal atoms. As soon as they get there they feel the pull of Layer B

and off they go again, for another round.


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Fig 1: Principle of PV Cell

If n- and p-silicon are combined, the differently charged free charge carriers

are attracted to each other, move into the respective neighbouring area and so charge it

with electricity. A strong, inner electric field is created at the boundary layer, theP-n crossover. When illuminated, this field will separate the created charge carriers and a

voltage of approx. 0.5 V is created at the outer contacts. The p-n-crossover ensures that

the charge carriers created by the light do not join up again, but can be used as current.

Silicon solar cells are differentiated from untreated, extremely clean semiconductor

material by two main stages: doping and p-n-crossover.

If small quantities of foreign atoms are introduced into the silicon: ("doping"),

free moving charge carriers are created according to the type of atoms. Phosphorus atoms

lead to free electrons (n-silicon), boron to free holes (p-silicon). Doping thereforeprovides free charge carriers in otherwise isolated silicon.


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Fig 2: Principle of PV Cell

1.3 ELECTRIC MODEL OF PHOTOVOLTAIC CELL

Thus the simplest equivalent circuit of a solar cell is a current source in parallel with a

diode. The output of the current source is directly proportional to the light falling on the cell

(photocurrent Iph). During darkness, the solar cell is not an active device; it works as a

diode, i.e. a p-n junction. It produces neither a current nor a voltage. However, if it is

connected to an external supply (large voltage) it generates a current ID, called diode (D)

current or dark current. The diode determines the I-V characteristics of the cell.


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Fig 3: Electrical model of PV Cell

Semiconductors, characterized as being perfect insulators at absolute zero,

become increasingly conductive as temperature is increased. As temperature becomes

greater, sufficient energy is transferred to a small fraction of electrons, causing them to

move from the valence band to the conduction band and holes to move from the

conduction band to the valence band. The increase in temperature responsible for this

entire process is a direct result of external energy in the case of PV systems, it is incident

photons due to illumination.

Under the photoelectric effect, because photons incident upon a p-n diode can

create electron-hole pairs at a cross material junction, an electric potential difference

across this junction can be established. Under no illumination, electrons and holes are

separated at n and p regions respectively due to the diode characteristic unidirectional

current path. When illuminated, PV cells are impacted by incident photons which

bombard cell electrons creating electron hole pairs. These electron hole pairs then

separate in response to the electric field created by the cell junction, causing electrons to

drift back into the n region, and holes into the p region. A bidirectional current path is

created and energy can be harnessed.


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Fig 4. Graphs


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1.4 MANUFACTURING OF SOLAR CELLS

Properties of silicon:

Atomic number 14

Atomic mass 28.0855 g.mol-1

Electronegativity according to Pauling 1.8

Density 2.33 g.cm-3

at 20 C

Melting point 1410 C

Boiling point 3265 C

Vanderwaals radius 0.132 nm

Ionic radius 0.271 (-4) nm ; 0.041(+4)

Isotopes 5

There are two main reasons why silicon is used for manufacturing solar cells.One is

that silicon is an elemental semiconductor with good stability and a well balanced set of

electronic ,physical and chemical properties,the same set of strengths that have made

silicon the preferred material for microelectronics. The molecular structure of single-

crystal silicon is uniform. This uniformity is ideal for the transfer of electrons efficiently

through the material. However, in order to make an effective photovoltaic cell, silicon

needs to be "doped" with other elements.

Raw Materials

The basic component of a solar cell is pure silicon, which is not pure in its

natural state.


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Fig 5: Raw Materials

To make solar cells, the raw materialssilicon dioxide of either quartzite

gravel or crushed quartzare first placed into an electric arc furnace, where a carbon arcis applied to release the oxygen. The products are carbon dioxide and molten silicon. At

this point, the silicon is still not pure enough to be used for solar cells and requires further

purification.

Pure silicon is derived from such silicon dioxides as quartzite gravel (the

purest silica) or crushed quartz. The resulting pure silicon is then doped (treated with)

with phosphorous and boron to produce an excess of electrons and a deficiency of

electrons respectively to make a semiconductor capable of conducting electricity. The

silicon disks are shiny and require an anti-reflective coating, usually titanium dioxide.

The solar module consists of the silicon semiconductor surrounded by protective

material in a metal frame. The protective material consists of an encapsulant of

transparent silicon rubber or butyryl plastic (commonly used in automobile windshields)

bonded around the cells, which are then embedded in ethylene vinyl acetate. A polyester

film (such as Mylar or tedlar) makes up the backing. A glass cover is found on terrestrial

arrays, a lightweight plastic cover on satellite arrays.

Purifying the silicon

The silicon dioxide of either quartzite gravel or crushed quartz is placed into an

electric arc furnace. A carbon arc is then applied to release the oxygen. The


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products are carbon dioxide and molten silicon. This simple process yields silicon

with one percent impurity, useful in many industries but not the solar cell industry.

The 99 percent pure silicon is purified even further using the floating zone

technique. A rod of impure silicon is passed through a heated zone several times in

the same direction. This procedure "drags" the impurities toward one end with

each pass. At a specific point, the silicon is deemed pure, and the impure end is

removed.

Making single crystal silicon

Solar cells are made from silicon boules, polycrystalline structures that have the

atomic structure of a single crystal. The most commonly used process for creating

the boule is called the Czochralski method. In this process, a seed crystal of silicon

is dipped into melted polycrystalline silicon. As the seed crystal is withdrawn and

rotated, a cylindrical ingot or "boule" of silicon is formed. The ingot withdrawn is

unusually pure, because impurities tend to remain in the liquid.

Making silicon wafers

From the boule, silicon wafers are sliced one at a time using a circular saw whose

inner diameter cuts into the rod, or many at once with a multiwire saw. (Adiamond saw produces cuts that are as wide as the wafer. 5 millimeter thick.)

Only about one-half of the silicon is lost from the boule to the finished circular

wafermore if the wafer is then cut to be rectangular or hexagonal. Rectangular

or hexagonal wafers are sometimes used in solar cells because they can be fitted

together perfectly, thereby utilizing all available space on the front surface of the

solar cell.


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After the initial purification, the silicon is further refined in a floating zone

process. In this process, a silicon rod is passed through a heated zone several times,which serves to 'drag" the impurities toward one end of the rod. The impure end can

then be removed.


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Next, a silicon seed crystal is put into a Czochralski growth apparatus, where

it is dipped into melted polycrystalline silicon. The seed crystal rotates as it is

withdrawn, forming a cylindrical ingot of very pure silicon. Wafers are then sliced out

of the ingot.

The wafers are then polished to remove saw marks. (It has recently been found

that rougher cells absorb light more effectively, therefore some manufacturers have

chosen not to polish the wafer.)

Doping

The traditional way of doping (adding impurities to) silicon wafers with boron and

phosphorous is to introduce a small amount of boron during the Czochralski process.

Properties of Boron:

Atomic number

Atomic mass

Density

Melting point

Boiling point

Vanderwaals radius

Ionic radius

5

10.81 g.mol-1

2.3 g.cm-3

at 20C

2076 C

3927 C

0.098 nm

0.027 nm

Isotopes 2


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The wafers are then sealed back to back and placed in a furnace to be heated to

slightly below the melting point of silicon (2,570 degrees Fahrenheit or 1,410

degrees Celsius) in the presence of phosphorous gas. The phosphorous atoms

"burrow" into the silicon, which is more porous because it is close to becoming a

liquid. The temperature and time given to the process is carefully controlled to

ensure a uniform junction of proper depth. A more recent way of doping silicon

with phosphorous is to use a small particle accelerator to shoot phosphorous ions

into the ingot. By controlling the speed of the ions, it is possible to control their

penetrating depth. This new process, however, has generally not been accepted by

commercial manufacturers.

Properties of Phosphorous:

Atomic number 15

Atomic mass 30,9738 g.mol-1

Density 1,82 g/ml at 20C

Melting point 44,2 C

Boiling point 280 C

Placing electrical contacts

Electrical contacts connect each solar cell to another and to the receiver of

produced current. The contacts must be very thin (at least in the front) so as not toblock sunlight to the cell. Metals such as palladium/silver, nickel, or copper are

vacuum-evaporated.


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Fig 6: Makeup of a typical solar cell

This illustration shows the makeup of a typical solar cell. The cells are

encapsulated in ethylene vinyl acetate and placed in a metal frame that has a Mylar

back sheet and glass cover through a photo resist, silk screened, or merely

deposited on the exposed portion of cells that have been partially covered with

wax. All three methods involve a system in which the part of the cell on which a

contact is not desired is protected, while the rest of the cell is exposed to the metal.


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After the contacts are in place, thin strips ("fingers") are placed between

cells. The most commonly used strips are tin-coated copper.

The anti-reflective coating

Because pure silicon is shiny, it can reflect up to 35 percent of the sunlight. To

reduce the amount of sunlight lost, an anti-reflective coating is put on the silicon wafer.

The most commonly used coatings are titanium dioxide and silicon oxide, though

others are used. The material used for coating is either heated until its molecules boil off

and travel to the silicon and condense, or the material undergoes sputtering. In this

process, a high voltage knocks molecules off the material and deposits them onto the

silicon at the opposite electrode.Yet another method is to allow the silicon itself to react

with oxygen- or nitrogen-containing gases to form silicon dioxide or silicon nitride.

Commercial solar cell manufacturers use silicon nitride.

Encapsulating the cell

The finished solar cells are then encapsulated; that is, sealed into silicon rubber or

ethylene vinyl acetate. The encapsulated solar cells are then placed into an aluminum

frame that has a Mylar or tedlar back sheet and a glass or plastic cover.

Types of Solar cells

Monocrystalline silicon(c-Si):often made using the Czochralski process. Single-

crystal wafer cells tend to be expensive, and because they are cut from cylindrical

ingots, do not completely cover a square solar cell module without a substantial

waste of refined silicon. Hence most c-Si panels have uncovered gaps at the four

corners of the cells.

Poly- or multicrystalline silicon (poly-Si or mc-Si): made from cast square

ingots large blocks of molten silicon carefully cooled and solidified. Poly-Si cells

are less expensive to produce than single crystal silicon cells, but are less efficient.

Ribbon silicon is a type of multicrystalline silicon: it is formed by drawing flat

thin films from molten silicon and results in a multicrystalline structure. These

cells have lower efficiencies than poly-Si, but save on production costs due to a

great reduction in silicon waste, as this approach does not require sawing from

ingots.
http://en.wikipedia.org/wiki/Monocrystalline_siliconhttp://en.wikipedia.org/wiki/Czochralski_processhttp://en.wikipedia.org/wiki/Multicrystalline_siliconhttp://en.wikipedia.org/wiki/Ribbon_siliconhttp://en.wikipedia.org/wiki/Moltenhttp://en.wikipedia.org/wiki/Multicrystallinehttp://en.wikipedia.org/w/index.php?title=Silicon_waste&action=edit&redlink=1http://en.wikipedia.org/wiki/Sawhttp://en.wikipedia.org/wiki/Ingothttp://en.wikipedia.org/wiki/Ingothttp://en.wikipedia.org/wiki/Sawhttp://en.wikipedia.org/w/index.php?title=Silicon_waste&action=edit&redlink=1http://en.wikipedia.org/wiki/Multicrystallinehttp://en.wikipedia.org/wiki/Moltenhttp://en.wikipedia.org/wiki/Ribbon_siliconhttp://en.wikipedia.org/wiki/Multicrystalline_siliconhttp://en.wikipedia.org/wiki/Czochralski_processhttp://en.wikipedia.org/wiki/Monocrystalline_silicon


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Fig 7: Types of solar cells

1.5 PV CELL SPECIFICATIONS

MULTICRYSTALLINE SOLAR CELL

NEGATIVE POSITIVE


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MECHANICAL SPECIFICATION

Product Multicrystalline cell

Format 156 mm 156 mm 0.5 mmDiameter:220 0.5 mm

Average thickness (Si) 160 m 30 m / 180 m 30 m /200 m 30 m

Front contacts () Three 1.5 mm wide bus bars(silver)Alkaline texturized surfaceDarkblue anti-reflecting coating (siliconnitride)

Back contacts (+) Three 3 mm wide bus bars (silver /aluminum)Aluminum backsidemetallization


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1.6 APPLICATIONS

For low-power portable electronics, like calculators or small fans, a

photovoltaic array may be a reasonable energy source rather than a battery.

Although using photovoltaics lowers the cost (over time) of the device to the user-

who will never need to buy batteries-the cost of manufacturing devices with

photovoltaic arrays is generally higher than the cost of manufacturing devices to

which batteries must be added. Therefore, the initial cost of photovoltaic devices is

often higher than battery-operated devices.

In other situations, such as solarbattery chargers, watches, and flashlights, the

photovoltaic array is used to generate electricitythat is then stored in batteries foruse later.

Fig 8: Application of PV Cell
http://science.jrank.org/pages/2385/Electronics.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/779/Battery.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/779/Battery.htmlhttp://science.jrank.org/pages/5204/Photovoltaic-Cell-Applications.htmlhttp://science.jrank.org/pages/2385/Electronics.html


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1.7 MAKING OF SOLAR CELL MODULE

FLOW CHART

Solar Cell

Manufacturing

Solar cell

Soldering

machine.

Komex 1

Pick &Place

Robot 1

Panel layout

EVA &Glass

Semi

Automatic

Bus Bay

soldering

Manual Manual

layout

Lamination

thermal &

vacuum

Panel

TestingPick & Place

Robo

Panel layout

EVA &GlassPick &PlaceRobot 2

Solar cell

Soldering

machine.

Komex 2

Bus Bay

soldering

Lamination

thermal &

vacuum

Bus Bay

solderingLamination

thermal &

vacuum

PANEL

ASSEMBLY


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PANEL

ASSEMBLY

Fork lift

Manual

Distributi

on box

fixing

Soldering

Pressing

machine

Panel cell

side

frame fix

Gate outLoadingin trucksPacking

MANUFACTURING PROCESS

Solar Semiconductor employs equipment that can handle 160 micron cells, 2Busbar and 3 Busbar cells. The Tabber is used to interconnect cells in a

string, uses vacuum suction cups to pick cells and an IR camera to check for

any cell breakages.

The advanced automation unit at Solar Semiconductor comes with Twin

Robot System. These Robotic systems speed up the manufacturing processand enhance efficiency. It also helps in increasing productivity, minimizing

errors and life cycle costs.


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The encapsulation process involves vacuum pressing the array sandwich(glass EVA array EVA backsheet). The pressing melts the fast cure

0.33mm EVA, which then acts as an adhesive and bonds the backsheet andthe glass sheet with the cell array to make it weather and dust proof.

The laminate is trimmed and then taped with a double sided adhesive foamtape. The temperature is maintained at 140 degree centigrade for lamination.

This trimmed laminate is then framed using an in-house developed

automatic frame-fitter. This is followed by junction box fitting, which is

done manually.

The testing for electrical parameters is done by using the most advancedclass AAA - pulsed type Sun Simulators.

The Reliability Testing Lab has been set up for in-house testing of prototypemodules and new materials. It enables self-certification of products and

speeds up new process qualification and certification process.

Quality control at Solar Semiconductor is done through checks on incomingraw material and on the manufacturing process. In order to enhance the

effectiveness and ensure total quality control, various quality concepts likeQuality circles and Kaizen are being practiced.


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2. SOLAR MOBILE CHARGER UNIT

Portable Solar Mobile Charger for mobile phone can be charged with Sun

light, and electrical power. It stores power from the sun and lets you charge mobilephone, iPod, etc at your convenience.

PV cell converts light into electric current using the photo electric effect.

In photo electric effect electrons emitted from the matter (metals and nonmetals,

liquids and gases)as a consequence of their absorption of energy 4m

electromagnetic radiation of very short wavelength such as ultraviolet or visible

light.

The photons of light beam have a characteristic energy determined by the

(frequency of light).In the photon emission process if an electron with in some

material absorbs the energy the energy of 1 photon and thus has more energy than

the work function (the electron binding energy) of the material is ejected. If photon

energy is low the electron is unable to escape 4m the material.

Increasing the intensity of the light beam increases the number of photons

in the light beam and thus increase the number of electrons emitted but doesnt

increase the energy that each electron possesses.

The energy of the emitted electron doesnt depend on the light intensity

of the incoming light but only on the energy or frequency of the individual

photons. It is an interaction between the incident photon and the outermost

electron.


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2.1 MATERIALS REQUIRED

SOLAR CELLS

12 pieces each generating 0.5 V.

Fig 9: Solar cells

ACRYLIC SHEET

Cast acrylic sheet is a material with unique physical properties and performance

characteristics. It weighs half as much as the finest optical glass yet is equal to it in clarity

and is up to 17 times more impact resistant.

Fig 10: Acrylic sheet


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ETHYLENE VINYL ACETATE

Ethylene vinyl acetate(also known as EVA) is the copolymerof ethyleneand vinyl

acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with theremainder being ethylene.

It is a polymerthat approaches elastomericmaterials in softness and flexibility, yet

can be processed like other thermoplastics. The material has good clarity and barrier

properties, low-temperature toughness, stress-crack resistance, hot-melt adhesive water

proof properties, and resistance to UV radiation. EVA has little or no odor and is

competitive with rubberand vinylproducts in many electrical applications.

Fig 11: EVA

TEFLON:

Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylenethat finds numerous applications. PTFE is most well-known by the DuPont brand name

Teflon.

PTFE is a fluorocarbon solid, as it is a high-molecular-weight compound consisting

wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing

substances wet PTFE, as fluorocarbons demonstrate mitigated London dispersion forces
http://en.wikipedia.org/wiki/Heteropolymerhttp://en.wikipedia.org/wiki/Ethylenehttp://en.wikipedia.org/wiki/Vinyl_acetatehttp://en.wikipedia.org/wiki/Vinyl_acetatehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Elastomerhttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/UV_radiationhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Vinylhttp://en.wikipedia.org/wiki/Rubberhttp://en.wikipedia.org/wiki/UV_radiationhttp://en.wikipedia.org/wiki/Adhesivehttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Thermoplastichttp://en.wikipedia.org/wiki/Elastomerhttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Vinyl_acetatehttp://en.wikipedia.org/wiki/Vinyl_acetatehttp://en.wikipedia.org/wiki/Ethylenehttp://en.wikipedia.org/wiki/Heteropolymer


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due to the high electronegativity of fluorine. PTFE has one of the lowest coefficients of

friction against any solid.

Fig 12: Teflon

TABBING WIRE

Tabbing wire is used by solar panel manufacturers to connect individual solar cells

together in serial connections. It is copper wire coated with solder

Typical characteristics of tabbing wire are

GAUGE: 0.1MM

WIDTH: 2.0 MM

98-99% of the material weight is Copper Ribbon which serves as the base center of

the tabbing wire. The tin coating is made from either lead based material 62 SN% (tin) /

36 PB% (lead) / 2 AG% (silver) or 96.5% SN / 3.5% Ag (Silver) or other variations of

lead free solder.

Fig 13: Tabbing Wire


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7805 REGULATOR

It converts a varying DC input voltage into a constant 5 DC output voltage.

Fig 15 : 7805 regulator

MULTIPIN CABLE


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2.2 SPECIFICATIONS OF CHARGER

Uses high-efficiency monocrystalline silicon Solar panel: 5.5V/1000mA

Output voltage: 5.5V

Output current: 300-550 mA

Time taken to charge mobile phone using the charger: about 60 for typical mobile

Time to fully charge the built-in battery using computer or AC adapter: ~ 2 hours

Time to fully charge the built-in battery with solar energy: ~ 8 hours

2.3 DESIGN OF CHARGER

A multicrystalline solar cell is taken and its cut into 12 parts.

By taking tabbing wire and applying flux, paste soldering is done on the bus bars.

Fig 16 : Initial Arrangement of Solar cells in Series


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This is done from top of one cell to bottom of the other cell. They are connected in

series. The above process is continued for remaining cells.

A wire comes from positive side of cell and another wire comes from the negative

side. The whole arrangement is then placed on top of an acrylic sheet, Teflon, EVA.

On top these panels EVA is again placed and are attached with a feviquick.

Fig 17: Cells in Series

Thee wires are connected to the terminals of a regulator. Using multimeter we verify the voltage is brought down to 5 V.

Regular terminals are further connected to multipin cable.

The pin is then connected to mobile to charge it.


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Fig 18 :Final Work

2.4 EXPERIMENTAL WORK


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Using Sun light:

LIGHTAND

HEAT

HEAT/TEMP

NUMBER

OF

CELLS

AREAOF

CELL

SERIES/

PARELLEL

CONNECTIO

N

VOLTAGE CURRENTS.NO LIGHT

INTENSITY POWER

SOURCE

1 SUNLIGHT

NOON OPENSPACE

1

2

3

4

5

6

7

8

9

10

11

SERIES0.55

1.10

1.65

2.20

2.78

3.34

3.87

4.42

4.94

5.14

6.06

1 0.55

1.10

1.65

2.20

2.78

3.34

3.87

4.42

4.94

5.14

6.06


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Using 60 watts bulb:

S.NO LIGHT

AND

HEAT

SOURCE

LIGHT

INTENSITY

HEAT/

TEMP

AREA

OF

CELL

SERIES/NUMBE

R

OF

CELLS

CURRENTPARELLEL

VOLTAG

E

POWER

()CONNECTION

260

WATTSBULB

ROOMTEMPERATURE

ROOMTEMP

1

2

3

4

5

6

7

8

9

10

11

1 0.42

0.94

1.40

1.85

2.20

2.71

3.24

3.53

3.84

SERIES 0.42

0.94

1.40

1.85

2.20

2.71

3.24

3.53

3.84

4.26 4.26

4.50 4.50


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Using 100 watts bulb:

S.NO LIGHT

AND

HEAT

SOURCE

LIGHT

INTENSITYHEAT/

TEMPNUMBE

R

OF

CELLS

AREA

OF

CELL

SERIES/

PARELLEL VOLTAG

E

CURREN

TPOWER

CONNECTIO

N ()

3 100WATTSBULB

INSIDEROOM

ROOMTEMP

1

2

3

4

5

6

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8

9

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SERIES 0.48

0.98

1.40

1.88

2.35

2.91

3.36

3.75

4.30

1 0.48

0.98

1.40

1.88

2.35

2.91

3.36

3.75

4.30

4.814.81

5.38 5.38


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Fig 19:Charging Nokia mobile using solar cells


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Fig 20:Charging Samsung mobile using solar cells


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3. MOBILE BATTERY

A lithium-ion battery(Li-ion batteryor LIB) is a family of rechargeable battery

types in which lithiumions move from the negative electrodeto the positive electrode

during discharge, and back when charging. Chemistry, performance, cost, and safety

characteristics vary across LIB types. Unlike lithium primary batteries (which are

disposable), lithium-ion electrochemical cells use an intercalated lithium compound as

the electrode material instead of metallic lithium.

Fig 21: Nokia Li-ion battery for powering a mobile phone

3.1 ELECTRICAL MODEL FOR LI-ION BATTERY

Safety circuits inside a Li-Ion battery pack:

Inside a Li-Ion pack there is always a safety circuit that consists of four main sections:

The controller IC that monitors each cell (or parallel cells) voltage and preventsthe cells to overcharge or over discharge controlling accordingly the cutoff

switches. Also the voltage across the switches is monitors in order to prevent over

current.

The control switches that usually comprises FET structures that cutoff the chargeor discharge depending on the control signals of the controller IC.
http://en.wikipedia.org/wiki/Rechargeable_batteryhttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Primary_batteryhttp://en.wikipedia.org/wiki/Electrochemical_cellhttp://en.wikipedia.org/wiki/Intercalation_%28chemistry%29http://en.wikipedia.org/wiki/Intercalation_%28chemistry%29http://en.wikipedia.org/wiki/Electrochemical_cellhttp://en.wikipedia.org/wiki/Primary_batteryhttp://en.wikipedia.org/wiki/Electrodehttp://en.wikipedia.org/wiki/Lithiumhttp://en.wikipedia.org/wiki/Rechargeable_battery


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The temperature fuse that cutoff the current if the control switches experienceabnormal heating. This fuse is not recoverable.

The thermistor (usually PTC) that measure the battery temperature inside the pack.It's terminals are connected to the charger so it can sense the temperature of the

pack and control the charge current until the battery it's full charged.

3.2 SPECIFICATIONS OF BATTERY

Type : RH-105

Make : Nokia Make: Samsung

Model : 1208 Model: GT-B5310

Voltage : Max-5V Voltage : Max-5V

Min-3.7V Min-3.7V

Capacity: 1020mahr Capacity: 960maph


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3.3 STRUCTURE

Li-Ion cell has a tree layer structure. A positive electrode plate (made with LithiumCobalt oxide - cathode), a negative electrode plate (made with specialty carbon - anode)

and a separator layer.

Inside the battery also exists a electrolyte which is a lithium salt in an organic

solvent. I-Ion is also equipped with a variety of safety measures and protective

electronics and/or fuses to prevent reverse polarity, over voltage and over heating and

also have a pressure release valve and a safety vent to prevent battery from burst.

Fig 22: Structure


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3.4 WORKING PRINCIPLE

Lithium battery uses lithium cobalt oxide as positive electrode - cathode - and a

high crystallized special carbon as negative electrode - anode. Also an organic solvent

specialized to be used with the specific carbon works like electrolytic fluid.

The chemical reaction that takes place inside the battery is as follows, during charge

and discharge operation:

The main principle behind the chemical reaction is one where lithium in

positive electrode material is ionized during charge and moves from layer to layer in the

negative electrode.


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3.5 FEATURES OF LITHIUM ION BATTERIES

High energy density that reaches 400 Wh/L (volumetric energy density) or

160Wh/Kg (mass energy density)

High voltage. Nominal voltage of 3,6V or even 3,7V on newer Li-Ion batteries.


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No memory effect. Can be charged any time, but they are not as durable as NiMH

and NiCd batteries.

High charge currents (0,5-1A) that lead to small charging times (around 2-4

hours).

Flat discharge voltage allowing the device to stable power throughout the

discharge period.

Typical charging Voltage 4,2 0,05V.

Charging method: constant current - constant voltage (CV-CC).

Typical operation voltage 2,8V to 4,2V

Recommended temperature range 0-40

3.6 CHARGING CHARECTERISTICS

Charging method is constant current - constant voltage (CV-CC). This means

charging with constant current until the 4.2V are reached by the cell (or 4,2V x the

number of cells connected in series) and continuing with constant voltage until the

current drops to zero.

The charge time depends on the charge level of the battery and varies from 2-4

hours for full charge. Also Li-Ion cannot fast charge as this will increase their

temperature above limits. Charging time increases at lower temperatures.


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3.7 WORKING PROCESS

A battery charger is basically a DC power supply source. Here a transformer isused to step down the AC mains input voltage to the required level as per the

rating of the transformer.

This transformer is always a high power type and is able to produce a high current

output as required by most lead-acid batteries.

A bridge rectifier configuration is used to rectify the low voltage AC into DC and

is further smoothed by a high value electrolytic capacitor.

This DC is fed to an electronic circuit which regulates the voltage into a constant

level and is applied to the battery under charge, where the energy is stored through

an internal process of chemical reaction.

In automatic battery chargers a voltage sensor circuit is incorporated to sense the

voltage of the battery under charge. The charger is automatically switched OFF

when the battery voltage reaches the required optimum level.

Calculation of Charging or discharging time of a Battery

The rated current capacity of a chargeable battery may vary according to its

applications. Its current holding capacity is expressed in ampere-hour (AH). This

unit of measurement may be defined as the maximum current through which the

particular battery can be fully charged or discharged in one hour.

If for example a 4 AH fully charged battery is discharged at 4 ampere rate, then

ideally it should take an hour for it to get fully discharged (but practically it can be

seen that the back up time is much less than an hour due to the existing

inefficiency in all batteries).

Similarly if the same battery is charged at 4 ampere rate, then it should take an

hour to get it fully charged. But its never a good practice to charge or discharge

batteries at their full current ratings.
http://www.brighthub.com/engineering/electrical/articles/61881.aspxhttp://www.brighthub.com/engineering/electrical/articles/61881.aspx


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Ideally the charging and the discharging process should be carried out gradually

for about 10 hours. So to find out the optimum charging current of a battery, just

divide its AH by 10, the same is true to find its correct continuous discharge rate.

3.8 ADVANTAGE

One great advantage of Li-Ion batteries is their low self-discharge rate of only

approximately 5% per month, compared with over 30% per month and 20% per month in

nickel metal hydride batteries and nickel cadmium batteries respectively.

Comparison table of the most common batteries types

Chemistry Type Ni-Cd Ni-MH Leadacid

Li-ionCylindrical

Li-ionPrismatic

Li-Po

Nominal Voltage (V) 1.2 1.2 2,1 3.6 3.6 / 3.7 3.6

Specific Energy (Wh/Kg) 50 70 30 80 100-160 140

Specific Energy (Wh/L) 150 200 - - 250-360 -

Cycle Life (Times) 500 560 - 1000 1000 -

Environmental hazard low medium medium high high high

Safety High High medium low low low

Cost low medium low high high high

Self-Discharge Rate

(%/month)

25-30 30-35 - 6-9 6-9 -

Memory Effect yes yes yes no no no


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CONCLUSION

In solar mobile charger ripples will not be there as we use DC power

directly to charge the mobile.

Battery life is more as high voltages are not developed.

Versatility of Solar mobile charger is high.

Life of the battery will be high as we use solar mobile charger.

Adaptability is high.


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REFERENCES

Solar semiconductor Industry visit

http://en.wikipedia.org/wiki/Solar_cell

encyclobeamia.solarbotics.net/article...

www.solarbuzz.com/going-solar

www.solarserver.com/knowledge
http://www.solarbuzz.com/going-solahttp://www.solarbuzz.com/going-solahttp://www.solarbuzz.com/going-sola

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