CHAPTER -1 INTRODUCTION

What is Solar Energy?

Every day, the sun radiates (sends out) an enormous amount of energy—called solar

energy. It radiates more energy in one second than the world has used since time began. This

energy comes from within the sun itself.

Like most stars, the sun is a big gas ball made up mostly of hydrogen and helium gas.

The sun makes energy in its inner core in a process called nuclear fusion.

It takes the sun’s energy just a little over eight minutes to travel the 93 million miles

to Earth. Solar energy travels at a speed of 186,000 miles per second, the speed of light.

Only a small part of the radiant energy that the sun emits into space ever reaches the

Earth, but that is more than enough to supply all our energy needs. Every day enough solar

energy reaches the Earth to supply our nation’s energy needs for a year! Solar energy is

considered a renewable energy source.

Today, people use solar energy to heat buildings and water and to generate electricity.

Solar radiation is format among the promising new source of energy. India receives

annually over 60 x 1000 MWH of solar insulation with a span of 3000 – 3200 hrs in

Rajasthan, Gujarat, West of Madhya Pradesh and North of Maharashtra; and 2600 – 2800

hours in the rest of the country excepting Kerala, Assam and Kashmir.

Energy from the sun can be utilized in multi various ways. It can be tapped directly

from solar radiation in the form of thermal, thermodynamic and photovoltaic energy and

indirectly through the production of phytoman and other related energy sources such as wind,

hydropower and ocean energy all of which are the result of solar addition on the planet Earth.

The contribution of these sources in the total consumption of energy in the world is about

15%.

Traditionally, the utilization of solar energy has been confined to drying of

agricultural products such as grain, maize, paddy, grinder, cashew, pepper, tobacco curing,

fish and food drying. Its commercial application has been limited to production of common

salt and other marine chemicals like potash, cromide and magnesium salts.

The scope for the application of solar energy now stands greatly enhanced through

intensive research and development carried out all over world. The major areas that manifest

great potential out all over world.

The major areas that manifest great potential for immediate applications are:

a) Solar radiation can directly be utilized for purpose of heating and drying. By the same

taken, it can also be used for cooling and refrigeration.

b) Solar energy can be converted into electricity by exploiting the thermodynamic nature of

direct radiation for fuelling convention electricity generation plants.

c) Energy from the sun can also be captured by increasing the production of phytomass

through extensive energy plantations.

d) Architecture can build in both passive and active systems of solar energy utilization. In

the passive and active systems of solar energy utilization. In the passive system design of

buildings – domestic and industrial is optimized to make the best use of solar radiation to

protect the interior from extremes of weather that necessitate cooling and heating.

Architectural design can also incorporate the use of sunlight to avoid artificial lighting. An

active system of design can be developed by incorporating solar devices for cropping solar

radiation for heating, cooling, generating power for lighting and other uses.

THE CONCEPT

In 1968 Dr. Peter Glaser in the U.S. published an idea that centered on the fact that in

orbit close to earth, 1.43kw of solar energy illuminates any one square meter which is

considerably greater and one more continuous than on 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 geo stationery

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.

NEED FOR NON-CONVENTIONAL ENERGY:

Fuel deposit in the will soon deplete by the end of 2020. Fuel scarcity will be

maximum. Country like India may not have the chance to use petroleum products. Keeping

this dangerous situation in mind we tried to make use of non-pollutant natural resource of

petrol energy.

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. We have only about 25 years of oil

reserves and 75 – 100 years of coal reserves.

Resort to measure beginning of coal in thermal electric stations to serve the population would

result in global elemental change in leading to worldwide drought and decertification. The

buzzards of nuclear electric-stations are only too will. Now electric power beamed directly

by micro-wave for orbiting satellite. Solar power stations (s.p.s) provide a cost-effective

solution even though work on solar photo voltaic and solar thermo electric energy sources

has been extensively pursued by many countries. Earth based solar stations suffer certain

basic limitations. It is not possible to consider such systems and meeting continuous

uninterrupted concentrated base load electric power requirements. The non- conventional

resources are

1) Wind energy. 4) Ocean thermal energy.

2) Tidal energy . 5) Geo thermal energy.

3) Wave energy. 6) Solar energy.

1. WIND ENERGY:

Wind power is renewable and produces no greenhouse gases during operation, such

as carbon dioxide and methane. Airflow can be used to run wind turbines. Modern wind

turbines range from around 600KW to up to 5MWof rated power, although turbines, with

rated output of 1.5-3MW, have become the most common for commercial use; the power

output of a turbine is a function of the cube of the wind speed, so as wind speed increases

power output increases dramatically. Areas where winds are stronger and more constant,

such as offshore and high altitude sites are preferred location for wind farms.

Wind power is the fastest growing of the renewable energy technologies, though it

currently provides less than 0.5 percent of global energy. Over the past decade, global

installed maximum capacity increased from 2,500 MW in 1992 to just over 40,000 MW at

the end of 2003, at an annual growth rate of near 30 percent. The difficulties associate with

the wind energy are its availability is dilute and fluctuating in nature, requires storage devices

because of its irregularities and requires large areas for installation. The speeds of the

seasonal wind imply high cost of exploitation of wind energy.

1.2TIDAL ENERGY:

Tidal power captures energy from the tides in a vertical direction. Tides come in, raise

water levels in a basin, and tides rollout. Around low tide, the water in the basin is discharged

through a turbine. The power can be obtained by turbines from both in-out flows of water.

The amount of energy is very large but only in a few parts of world. The total power of tides

is estimated at (2 to 5) x10 MW, but difficulties associated with finding suitable locations,

high construction costs and non-uniform availability of power have hindered the progress of

harnessing the tidal energy. Development work is going on in different countries like U.S.A,

U.K, CANADA to harness this energy.

1.3 WAVE ENERGY:

Ocean waves are caused by the wind, which in turn is caused by uneven solar heating

and subsequent cooling of earth’s crust and the rotation of the earth. The main advantage of

power from waves, like most alternative energy sources, is free and renewable. The

harnessing of wave energy requires development of special power conversion devices. Like

other alternative sources, waves lack dependability, and there is relative scarcity of accessible

sites of large wave activity. Economic factors like capital investment, costs of maintenance,

repair and replacement are hindering the development.

1.4 OCEAN THERMAL ENERGY:

This also an indirect method of utilizing solar energy. A large amount of solar energy

is collected and stored in tropical oceans. The surface of water acts as the collector for solar

heat, while the upper layer of the sea constitute infinite heat storage reservoir. Thus the heat

contained in the oceans, could be converted into electricity by utilizing the fact that the

temperature difference between the warm surface waters of the tropical oceans and the colder

water in the depth is about 22 to 25 K. The temperature difference is small, even in the

tropics, OTEC systems have very low efficiency and consequently have very high capital

cost.

1.5 GEO THERMAL ENERGY:

Geothermal energy is energy obtained by tapping the heat of the earth itself, usually

from kilometers deep into the Earth’s crust. It is expensive to build a power station but

operating costs are low resulting in low energy costs for suitable sites. Ultimately, this energy

drives from heat in the Earth’s core. This geothermal power is renewable. These types of

power plants are used to generate power from geothermal energy. Dry steam, flash, and

binary. Dry steam plants take steam out of fractures in the ground and use it to directly drive

a turbine that spins a generator. Flash plants hot water, usually at temperature over 200 C, out

of the ground, and allows it to boil as it rises to the surface then separates the steam phase in

steam/water separators and then runs the steam through a turbine. In binary plants, the hot

water flows through heat exchangers, boiling an organic fluid that spins the turbine. The

condensed steam and remaining geo thermal fluid from all three types of plants are injected

back into the hot rock to pick up more heat. It is seen that while geothermal energy is not

sought after sole and long range solution to our energy problems, it never the less represents

a hot insignificant factor, if its resources are developed in a careful and an efficient manner.

1.6 SOLAR ENERGY:

Solar energy is very large, inexhaustible source of energy. The power from the sun

interrupted by earth is approximately 1.8/10MW, which are many thousands of times larger

than the present consumption rate on the earth of all energy sources. The quantum of energy

India’s land area receive from sun is equivalent to 15,000 time sits consumption requirement

(500 billion kWh) as projected for 2004. In addition to its size, solar energy has two other

factors in its favour. Firstly, unlike fossil fuels and nuclear power, it is an environmentally

clean source of energy. Secondly, it is free and available in adequate quantities in almost all

parts of the world people live. But there are some problems associated with its. The real

challenge in utilizing solar energy is of and economic concern. One has to strive for the

development of cheaper methods of collection and storage so that large initial investments

required at preset in most applications are reduced.

Solar energy can be used directly or indirectly. The direct means include thermal

and photovoltaic conversions while the indirect means include the water power, the winds

biomass and the temperature differences in the ocean.

SOLAR ENERGY OPTION:

Solar energy is very large, inexhaustible sources of energy. The power from the sun

intercepted by the Earth approximately 1.8 X 10 mw, which is many thousands of times

larger than the present consumption rate on the Earth of all commercial energy sources.

Though in principle, 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 unconventional

energy sources.

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 Earth’s orbit around the sun. In addition 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.

SOLAR PANEL:

Photovoltaic principles:

The photo- voltaic effect can be observed in nature in a variety of materials that have

shown that the best performance in sunlight is the semiconductors as stated above. When

photons from the sun are absorbed in a semiconductor, that create free electrons with higher

energies than the created there must be an electric field to induce these higher energy

electrons to flow out of the semi-conductor to do useful work. A junction of materials, which

have different electrical properties, provides the electric field in most solar cells for the

photon interaction in a semiconductor. A solar cell consists of

(a) Semi-conductor in which electron hole pairs are created by the absorption of incident

solar radiation.

(b) Region contacting a drift field for charge separation

(c) Charge collecting fronts and back electrodes.

Fig.: 2.1.1 photovoltaic effect

The photo-voltaic effect can be described easily for p-n junction in a semi-conductor.

In an intrinsic semi-conductor such as silicon, each one of the four valence electrons of the

material atom is tied in a chemical bond, and there are no free electrons at absolute zero. If a

piece of such a material is doped on one side by a five valance electron material, such as

arsenic or phosphorus, there will be an excess of electrons in that side, becoming an n-type

semi-conductor.

The excess electrons will be practically free to move in the semi-conductor

lattice. When a three valance electron material, such as boron dopes the other side of the

same piece, there will be deficiency of electrons leading to a p-type semi-conductor. This

deficiency is expressed in terms of excess of holes free to move in the lattice. Such a piece of

semi-conductor with one side of the p-type and the other, of the n-type is called p-n junction.

In this junction after the protons are absorbed, the free electrons of the n-side will tends to

flow to the p-side, and the holes of the p-side will tend to flow to the n-region to compensate

for their respective deficiencies. This diffusion will create an electric field from the n-region

to the p-region. This field will increase until it reaches equilibrium for voltage, the sum of the

diffusion potentials for holes and electrons. If electrical contacts the connected through an

external electrical conductor, the free electrons will flow from the n-type material through the

conductor to the p-type material as shown in the figure. Here the free electrons will enter the

holes and become bound electrons thus both free electrons and holes will be removed. The

flow of electrons through the external conductor constitutes an electric current, which will

continue as long as move free electrons and holes are being formed by the solar radiation.

This is the basis of photo-voltaic conversion that is the conversion of solar energy into

electrical energy. The combination of n-type and p-type semiconductors thus constitutes a

photo-voltaic cell or solar cell. All such cells some rate direct current that can be converted

into alternating current it desired.

The photo-voltaic effect can be observed in almost any junction of material that have

different electrical characteristics, but the best performance to date has been from cells using

semiconductor material especially all of the solar cells used for both space and terrestrial

applications have been made of the semiconductor silicon. Future cells may use such

materials as the semiconductors like Gallium arsenate, copper sulphate cad sulphide etc. The

device used to utilize the PHOTOVOLTAIC EFFECT is SOLAR CELL.

SPECFICATIONS:

Array size : 12×6

Size of panel : 16*14’’

No of modules: 1

Output voltage: 12v (Normal Condition)

Output voltage: 22v (peak hours)

Type : D.C Voltage

Material : silicon

Watts : 10w

Per Hour : 500 ma

8 hour Ampere: 4 Amps

Solar panel

CONSTRUCTION AND WORKING OF PHOTO-VOLTAIC CELL:

Electromagnetic energy can be converted directly to electrical energy in the photo

voltaic cell, commonly called the solar cell. Like the fuel cell the maximum conversion

efficiency of the system is not limited. By the efficiency of an externally reversible heat

engine cycle. Despite this, however the conversion of solar energy into electrical energy is

limited to relatively low conversion efficiencies.

The principle of operation of the photo voltaic cell was discovered by Adams and day

in 1876, using selenium in 1919, Cob Lenz discovered that a voltage is induced between the

illuminated and dark regions of semi conductivity crystals. However, photo electric

conversion was essentially a laboratory phenomenon until 1941. The owl discovered the

photo voltaic effect at the P-N junction of 2 semi-conductors.

Primary interest in these systems concerns the possible conversion of the

electromagnetic energy from the sun directly into electricity. Using the solar constant of

1395 w/sq. m it can be shown that the effective radiating temperature at the surface of the sun

is around 6000 k (10800 R), according to the wines displacement law for thermal radiation,

the most probable energy of the solar radiation is about 2.8 EV, while this value is very small

compared to the energies encounters is nuclear reactions, it is more than sufficient to strip the

valence electrons from many materials.

The successful operation of a solar cell release on the action of the P-N junction.

When a P-N junction is first formed, there is a transient charging process that establishes an

electric field in the vicinity of junction. Although both the N type and P type semiconductors

are naturally charged by themselves. The electron concentration in the N type material is so

high that when it is combined with P type semiconductor some of electrons from the N

material “spill over” into the holes of p material. This essentially makes the N material

positively charged and the P material negatively charged in the vicinity of the junction. This

charging process is continuous until the electric field or junction potential inhibits further net

flow and the electron and hole flow is the same in both directions as indicated.

The photons react with the valence electrons near p-n junctions to produce an effect

similar to that produced by the forward bias voltage. In this case V1 is the external voltage

that is generated by the photons.

Table1: COMPARISION

Sl. No SOLAR SYSTEM FUEL SYSTEM

01 Totally free from pollution Pollution is a great factor

02 No fuel consumption Fuel is the important need

03 No. of reciprocating parts are less No. of reciprocating parts are

more

04 Friction is greatly reduced Frictions between the parts are

high.

05 Low cost and maintenance Maintenance is difficult &

costly

06 Load carrying capacity is low Load carrying capacity is high

07 Continuous ride for hours together is

not possible

Continuous ride is possible

08 Ratio of speed reduction more when

weight increases

Speed reduction ratio is less and

it does not vary much

SCHEMATIC REPRESENTATION :

OTHER COMPONENTS:

CHEMICAL TANK:

The capacity of chemical tank even though it is more than 15 liters. Liquid

chemical should be placed into it only 15 liters. Remove the cup from the filler hole.

A strainer cup is placed in the filler hole. A Rubber tube connected with the bottom

of the tank is attached to the filter cup from under it, which brings in a jet of air from

the pump for correcting air cushion over the liquid chemical for creating air cushion.

The liquid chemical for ensuring free flow of the liquid to the nozzle. One end of the

Rubber tube is fitted with a socket which should be inserted tight into the cavity at the

bottom of the chemical tank.

DC MOTOR:

An electric motor is a machine which converts electrical energy to mechanical

energy. Its action is based on the principal that when a current- carrying conductor is placed

in a magnetic field, it experiences a magnetic force whose direction is given by Fleming’s

left hand rule (Keep the fore finger, middle finger and thumb of the left hand mutually

perpendicular to one another. If the fore finger indicates the direction of magnetic field and

middle finger indicates direction of current in the conductor, then the thumb indicates the

direction of the motion of conductor). When a motor is in operation, it develops torque. This

torque can produce mechanical rotation. The operation DC motor is as shown in the figure.

The speed of a DC motor may be changed by using resistors to vary the field current and,

therefore, the field strength. A simple motor has 6 parts, as shown in the diagram below.

1. An armature or rotor

2. A commutator

3. Brushes

4. An axel

5. Afield magnet

BATTERY:

INTRODUCTION:

In isolated systems away from the grid, batteries are used for storage of excess solar

energy converted into electrical energy. The only exceptions are isolated sunshine load such

as irrigation pumps or drinking water supplies for storage. In fact for small units with output

less than one kilowatt. Batteries seem to be the only technically and economically available

storage means. Since both the photo-voltaic system and batteries are high in capital costs. It

is necessary that the overall system be optimized with respect to available energy and local

demand pattern. To be economically attractive the storage of solar electricity requires a

battery with a particular combination of properties:

(1) Low cost

(2) Long life

(3) High reliability

(4) High overall efficiency

(5) Low discharge

(6) Minimum maintenance

(A) Ampere hour efficiency

(B) Watt hour efficiency

We use lead acid battery for storing the electrical energy from the solar panel for

lighting the street and so about the lead acid cells are explained below.

LEAD-ACID WET CELL:

Where high values of load current are necessary, the lead-acid cell is the type most

commonly used. The electrolyte is a dilute solution of sulfuric acid (H₂SO₄). In the

application of battery power to start the engine in an auto mobile, for example, the load

current to the starter motor is typically 200 to 400A. One cell has a nominal output of 2.1V,

but lead-acid cells are often used in a series combination of three for a 6-V battery and six for

a 12-V battery.

The lead acid cell type is a secondary cell or storage cell, which can be recharged.

The charge and discharge cycle can be repeated many times to restore the output voltage, as

long as the cell is in good physical condition. However, heat with excessive charge and

discharge currents short ends the useful life to about 3 to 5 years for an automobile battery.

Of the different types of secondary cells, the lead-acid type has the highest output voltage,

which allows fewer cells for a specified battery voltage.

CONSTRUCTION:

Inside a lead-acid battery, the positive and negative electrodes consist of a group of

plates welded to a connecting strap. The plates are immersed in the electrolyte, consisting of

8 parts of water to 3 parts of concentrated sulfuric acid. Each plate is a grid or framework,

made of a lead-antimony alloy. This construction enables the active material, which is lead

oxide, to be pasted into the grid. In manufacture of the cell, a forming charge produces the

positive and negative electrodes. In the forming process, the active material in the positive

plate is changed to lead peroxide (pbo₂). The negative electrode is spongy lead (pb).

Automobile batteries are usually shipped dry from the manufacturer. The electrolyte

is put in at the time of installation, and then the battery is charged to from the plates. With

maintenance-free batteries, little or no water need be added in normal service. Some types

are sealed, except for a pressure vent, without provision for adding water.

CHEMICAL ACTION:

Sulfuric acid is a combination of hydrogen and sulfate ions. When the cell discharges,

lead peroxide from the positive electrode combines with hydrogen ions to form water and

with sulfate ions to form lead sulfate. Combining lead on the negative plate with sulfate ions

also produces he sulfate. There fore, the net result of discharge is to produce more water,

which dilutes the electrolyte, and to form lead sulfate on the plates.

As the discharge continues, the sulfate fills the pores of the grids, retarding

circulation of acid in the active material. Lead sulfate is the powder often seen on the outside

terminals of old batteries. When the combination of weak electrolyte and sulfating on the

plate lowers the output of the battery, charging is necessary.

On charge, the external D.C. source reverses the current in the battery. The reversed

direction of ions flows in the electrolyte result in a reversal of the chemical reactions. Now

the lead sulfates on the positive plate reactive with the water and sulfate ions to produce lead

peroxide and sulfuric acid. This action re-forms the positive plates and makes the electrolyte

stronger by adding sulfuric acid.

At the same time, charging enables the lead sulfate on the negative plate to react with

hydrogen ions; this also forms sulfuric acid while reforming lead on the negative plate to

react with hydrogen ions; this also forms currents can restore the cell to full output, with lead

peroxide on the positive plates, spongy lead on the negative plate, and the required

concentration of sulfuric acid in the electrolyte.

The chemical equation for the lead-acid cell is

Charge

Pb + pbO₂ + 2H₂SO₄ 2pbSO₄ + 2H₂O

Discharge

On discharge, the pb and pbo₂ combine with the SO₄ ions at the left side of the

equation to form lead sulfate (pbSO₄) and water (H₂O) at the right side of the equation.

One battery consists of 6 cell, each have an output voltage of 2.1V, which are

connected in series to get an voltage of 12V and the same 12V battery is connected in series,

to get an 24 V battery. They are placed in the water proof iron casing box.

CARING FOR LEAD-ACID BATTERIES:

Always use extreme caution when handling batteries and electrolyte. Wear gloves,

goggles and old clothes. “Battery acid” will burn skin and eyes and destroy cotton and wool

clothing.

The quickest way of ruin lead-acid batteries is to discharge them deeply and leave

them stand “dead” for an extended period of time. When they discharge, there is a chemical

change in the positive plates of the battery. They change from lead oxide when charge out

lead sulfate when discharged. If they remain in the lead Sulfate State for a few days, some

part of the plate dose not returns to lead oxide when the battery is recharged. If the battery

remains discharge longer, a greater amount of the positive plate will remain lead sulfate. The

parts of the plates that become “sulfate” no longer store energy. Batteries that are deeply

discharged, and then charged partially on a regular basis can fail in less then one year.

Check your batteries on a regular basis to be sure they are getting charged. Use a

hydrometer to check the specific gravity of your lead acid batteries. If batteries are cycled

very deeply and then recharged quickly, the specific gravity reading will be lower than it

should because the electrolyte at the top of the battery may not have mixed with the

“charged” electrolyte.

Check the electrolyte level in the wet-cell batteries at the least four times a year and

top each cell of with distilled water. Do not add water to discharged batteries. Electrolyte is

absorbed when batteries are very discharged. If you add water at this time, and then recharge

the battery, electrolyte will overflow and make a mess.

Keep the top of your batteries clean and check that cables are tight. Do not tighten or

remove cables while charging or discharging. Any spark around batteries can cause a

hydrogen explosion inside, and ruin one of the cells, and you.

On charge, with reverse current through the electrolyte, the chemical action is

reversed. Then the pb ions from the lead sulfate on the right side of the equation re-form the

lead and lead peroxide electrodes. Also the SO₄ ions combine with H₂ ions from the water to

produce more sulfuric acid at the left side of the equation.

CURRENT RATINGS:

Lead-acid batteries are generally rated in terms of how much discharge currents they

can supply for a specified period of time; the output voltage must be maintained above a

minimum level, which is 1.5 to 1.8V per cell. A common rating is ampere-hours (A.h.)

based on a specific discharge time, which is often 8h. Typical values for automobile

batteries are 100 to 300 Ah.

As an example, a 200 Ah battery can supply a load current of 200/8 or 25A, used on

8h discharge. The battery can supply less current for a longer time or more current for a

shorter time. Automobile batteries may be rated for “cold cranking power”, which is related

to the job of starting the engine. A typical rating is 450A for 30s at a temperature of 0oF.

Note that the ampere-hour unit specifies coulombs of charge. For instance, 200 Ah.

corresponds to 200A*3600s (1h=3600s). the equals 720,000 A.S, or coulombs. One

ampere-second is equal to one coulomb. Then the charge equals 720,000 or 7.2*10^5ºC. To

put this much charge back into the battery would require 20 hours with a charging current of

10A.

The ratings for lead-acid batteries are given for a temperature range of 77 to 80ºF.

Higher temperature increase the chemical reaction, but operation above 110ºF shortens the

battery life.

Low temperatures reduce the current capacity and voltage output. The ampere-hour

capacity is reduced approximately 0.75% for each decreases of 1º F below normal

temperature rating. At 0ºF the available output is only 60 % of the ampere-hour battery

rating.

In cold weather, therefore, it is very important to have an automobile battery unto full

charge. In addition, the electrolyte freezes more easily when diluted by water in the

discharged condition.

SPECIFIC GRAVITY:

Measuring the specific gravity of the electrolyte generally checks the state of

discharge for a lead-acid cell. Specific gravity is a ratio comparing the weight of a substance

with the weight of a substance with the weight of water. For instance, concentrated sulfuric

acid is 1.835 times as heavy as water for the same volume. Therefore, its specific gravity

equals 1.835. The specific gravity of water is 1, since it is the reference.

In a fully charged automotive cell, mixture of sulfuric acid and water results in a

specific gravity of 1.280 at room temperatures of 70 to 80ºF. as the cell discharges, more

water is formed, lowering the specific gravity. When it is down to about 1.150, the cell is

completely discharged.

Specific-gravity readings are taken with a battery hydrometer, such as one in figure

Note that the calibrated float with the specific gravity marks will rest higher in an electrolyte

of higher specific gravity.

The decimal point is often omitted for convenience. For example, the value of 1.220

in figure is simply read “twelve twenty”. A hydrometer reading of 1260 to 1280 indicates

full charge, approximately 12.50 are half charge, and 1150 to 1200 indicates complete

discharge.

The importance of the specific gravity can be seen from the fact that the open-circuit

voltage of the lead-acid cell is approximately equal to

V=Specific gravity + 0.84

For the specific gravity of 1.280, the voltage is 1.280 = 0.84 = 2.12V, as an example.

These values are for a fully charged battery.

CHARGING THE LEAD-ACID BATERY:

The requirements are illustrated in figure. An external D.C. voltage source is

necessary to produce current in one direction. Also, the charging voltage must be more than

the battery e.m.f. Approximately 2.5 per cell are enough to over the cell e.m.f. so that the

charging voltage can produce current opposite to the direction of discharge current.

Note that the reversal of current is obtained just by connecting the battery VB and

charging source VG with + to + and –to-, as shown in figure. The charging current is

reversed because the battery effectively becomes a load resistance for VG when it higher

than VB. In this example, the net voltage available to produce charging currents is 15-

12=3V.

A commercial charger for automobile batteries is essentially a D.C. power supply,

rectifying input from the AC power line to provide D.C. output for charging batteries.

Float charging refers to a method in which the charger and the battery are always

connected to each other for supplying current to the load. In figure the charger provides

current for the load and the current necessary to keep the battery fully charged. The battery

here is an auxiliary source for D.C. power.

It may be of interest to note that an automobile battery is in a floating-charge circuit.

The battery charger is an AC generator or alternator with rectifier diodes, driver by a belt

from the engine. When you start the car, the battery supplies the cranking power. Once the

engine is running, the alternator charges he battery. It is not necessary for the car to be

moving. A voltage regulator is used in this system to maintain the output at approximately

13 to 15 V.

The constant voltage of 24V comes from the solar panel controlled by the charge

controller so for storing this energy we need a 24V battery so two 12V battery are connected

in series.

It is a good idea to do an equalizing charge when some cells show a variation of 0.05

specific gravity from each other. This is a long steady overcharge, bringing the battery to a

gassing or bubbling state. Do not equalize sealed or gel type batteries.

With proper care, lead-acid batteries will have a long service life and work very well

in almost any power system. Unfortunately, with poor treatment lead-acid battery life will be

very short.

Pump:A pump is a contrivance which provides energy to a fluid in a fluid system; it assists

to increase the pressure energy or kinetic energy, or both of the fluid by converting the

mechanical energy. The basic difference between a turbine and the pump, from the

hydrodynamic point of view, is that in the former flow takes place from the low pressure

towards the high pressure. Thus in turbine there is a axial rated flow, while in a pump, the

flow is decelerated.

CLASSIFICATION OF PUMPS:

on the basis of transfer of mechanical energy the pumps can be broadly classified as follows

1. Rotodynamic pumps

a) Radial flow pumps

b) Axial flow pumps

c) Mixed flow pumps

2. Positive displacement pumps

Reciprocating pump:

The reciprocating pump is a positive displacement pump as it sucks and raises the

liquid by actually displacing it with a piston/plunger that executes a reciprocating motion in a

closely fitting cylinder. The amount of pumped is equal to the volume displaced by the

piston.

The pumps designed with disk pistons create pressures upto 25bar and the plunger

pumps built up still higher pressures. Discharge from these pumps is almost wholly

dependent on the pump speed.

The total efficiency of a reciprocating pump is about 10 to 20% higher than a

comparable centrifugal pump.

Reciprocating pumps for industrial uses have almost become obsolete owing to their

high capital cost as well as maintenance cost as compared to that of centrifugal

pumps.However,small hand-operated pumps such as cycle pumps,football,pumps,kerosene

pumps, village well pumps and pumps used as important parts of hydraulic jack etc.,still find

wide applications. The reciprocating pump is best suited for relatively small capacities and

high heads .This type of pump is very common in oil drilling operations.

The reciprocating pump is generally employed for,

i) Light oil pump

ii) Feeding small boilers condensate return, and

iii) Pneumatic pressure system.

CLASSIFICATION OF RECIPROCATING PUMPS:

Reciprocating pumps are classified as follows:

1. According to the water being in contact with piston:

i) single-acting pump water is in contact with one side of the piston

ii) double-acting pump water is in contact with both sides of the piston.

2. According to number of cylinders:

i) Single cylinder pump

ii) Double cylinder pump (or two throw pump)

iii) Triple cylinder pump (or three throw pump)

iv) Duplex double-acting pump (or four throw pump)

v) Quintuplex pump or (five throw pump)

In general the reciprocating pumps having more than one cylinder are known as multi-

cylinder pumps.

Main components and working of an Reciprocating pump:

The main parts of a Reciprocating pump are:

1. Cylinder

2. Piston

3. Suction valve

4. Delivery valve

5. Suction pipe

6. Delivery pipe

7. Crank and connecting rod mechanism operated by a power source e.g., steam engine,

internal combustion engine or an electric motor.

Working of a single-acting reciprocating pump:

A single acting reciprocating pump has one suction pipe and one delivery pipe. It is

usually placed above the liquid level in the sump. When the crank rotates the piston moves

backward and forward inside the cylinder. The pump operates as follows:

-let us suppose that initially the crank is at the inner dead centre (I.D.C) and crank rotates in

the clockwise direction. As the crank rotates, the piston moves towards right and a vacuum is

created on the left side of the piston. This vacuum creates suction valve to open and

consequently the liquid is forced from the sump into the left side of the piston. When the

crank is at the outer dead centre (O.D.C) the suction is completed and the left side of the

cylinder is full of liquid.

-When the crank further turns from O.D.C to I.D.C, the piston moves inwards to the left and

high pressure is built up in the cylinder. The delivery valve opens and the liquid is forced into

the delivery pipe. The liquid is carried to the discharge tank through the delivery pipe. At the

end of the delivery stroke the crank comes to the I.D.C and the piston is at the extreme left

position.

Working of a double acting reciprocating pump:

In a double acting reciprocating pump, suction and delivery strokes occurs

simultaneously.

When the crank rotates from I.D.C in the clock wise direction, a vacuum is created in the left

side of piston and the liquid is sucked in the form the sump through valve (s1).at the same

time, the liquid on the right side of the piston is pressed and a high pressure causes the

delivery valve d2 to open and the liquid is passed on to the discharge tank. This operation

continues till the crank reaches O.D.C

With further rotation of the crank, the liquid is sucked in from the sump through the

suction valves s2 and is delivered to discharge tank through the delivery valve D1.when the

crank reaches I.D.C. The piston is in the extreme left position. Thus one3 cycle is completed

as the crank further rotates cycles are repeated

Because of continuous delivery strokes, a double acting reciprocating pump gives

more uniform discharge(as compared to a single acting pump which pumps the liquid

intermittently).to get a still more uniform feed, in variably a multi cylinder arrangement

having two or more cylinders is employed.

HOSE:

Hose are provided for smooth running of the pesticide from tank with the air enters

the pump unit and it is forced out. The pesticides come out of the nozzle with the help of

hoses from the tank.

NOZZLE :

Nozzles split the pesticides into atomized particles and sprays out. Nozzles

may be in different diameters to make the air mixture more pressurized.

SPECIFICATIONS:

FOR SOLAR SPRAYER

Solar panel : 10W Peak

Voltage - 21V

Amperes - 0.78Ah

Size - 425*265*25

Weight -1.2kg

Battery: 12V, 8Ah

Pump : Mini diaphragm pump

Volts -12v

Amps-2.1A

Flow -0.7GPM (2.6LPM)

Pressure-4.8bar

Tank Capacity : 15 lts

Possible tanks/once charged : 32

15*32=480 lts

Solar Power output/hr : 21v*0.78A

=16.38w

Battery capacity : 12v*8A

=96w

Total time to charge the battery : 7hrs

Nozzle Pressure : 0.32Mpa (3.2bar)

Nozzle Flow rate : 0.8L/min

Pump pressure : 4.8bar

Pump Flow rate : 2.6 L/min

ADVANTAGES AND APPLICATIONS

ADVANTAGES:

The advantages of solar agro sprayer are

It is good alternative for engine sprayer.

The energy alternative for engine sprayer.

Maintenance cost is less.

The use will be most welcomed when the fuel resources are over.

It is noiseless.

It does not create any pollution.

There is no vibration comparing with petrol operated sprayers.

The construction is simple and not so difficult as other sprayers.

Simple to use and easy to manufacture.

Long durability and reliability.

APPLICATION:

The solar Agro sprayer is mainly used for spraying liquified pesticides

CONCLUSION:

Solar sprayer have been designed successfully for the village former who cannot

afford money for fuel and he can make importance of non-conventional energy resources

utilization and quickly depleting petroleum products deposit we took an effort in this regent

and succeeded in our effort.

SCOPE FOR FUTURE WORK:

Our solar powered sprayer operating cost is almost negligible when compared to

existing method of using a petrol engine. Though the initial cost of the project is high, both

central and state government assistance in the form of subsidies for the solar aided projects

make job easy.

Instead of doing modification on existing sprayer body, a separate structure with less

weight and separate motor may be successfully designed for the system to have further more

efficient and more economical and reduce the weight further.