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Solar Cooker Cum Water Heater

INTRODUCTION

ON SURYA, THE SUN GOD

With bold might that spread all around, rises that sun. Who is Adiya, the origin of

life stretching golden rays like this hands, Savita the creative solar energy, heating objects to

shed fouluapours, moves on between Heaven & the Earth, removes away diseases projects,

heat and rays of light, holding mid-region and the Heaven by his gravitational pull makes

sunshine reach these.

With the golden eye - Savita, the Sun-God, has come there over the stay, holding

jewels of choicest splendour for one who distributes wealth to others. Yoked with wind

forces. He holds together towards Himself for their security, the creatures world and

features, and nourishing them, shines supreme over the various worlds

The sources of most of our energy has been our renewable positive fuels, oil, coal,

and natural gas. This is unfortunate from a long term point of view as these precious

resources that took millions of years for nature to produce are being depleted in a few

hundred years.

Our present overdependence on non-renewable natural resources could lead to

catastriphic consequences. There is real evidence that human being have outstripped the

capacity of this planet to sustain present life styles.

Until now the world is using the possible fuels, nuclear fuels for the power

generations, but the stocks of these fuels is limited on the contrary consumption is large.

The improved life standard of the man in this science age, seek over increasing power

demand and to face with it, has become the serious problems. Again the monopoly of one or

another nation in the possession of certain type of fuels has set international stresses. The

energy crises cannot be solved over night in a few years or even by the end of this century. It

is a long term problem, not only for this but for coming generation also. The two most

significant source are nuclear and solar energy.

Nuclear energy required advanced technology and costly means for it and reliable

utilization and may have undesirable side-effects, solar energy on the other hand shows

promise of becoming dependable energy source with the new requirement of highly

N.P.T.N. Achalpur 1


technical & specialized nature for its widespread utilization. In addition, it appears to have

no significant polluting effects from its use and it is also abundant

This is freely available sources of energy & can meet small localized needs. It is

becoming increasingly evident that solar energy could provide the only solution to supplying

energy to the village with an approximate population of 500.

Among the alternative sources of energy that deserves extensive exploitation, solar

energy is the most promising one, particularly in India, which lies in between latitude –

800 N & 370 N. Solar energy is virtually inexhaustible. The typical in solution reaching the

earth on the sunny day is about JKW/m2 at the equator.

The sum gives out 3.7 x 1026 watts of energy into space, out of which earth intercepts only

5x10-10th part of solar energy output. The energy emitted by the sun within 3 minutes is

equivalent to world's energy consumption during a year. Solar radiation is reduced in

intensity in the atmosphere by clouds, haze, dust, smog, and fog. Intensity of solar energy on

a sunny day in India is approximately 1.12KW/m2.

SUN STRUCTURE

The surface of inner sun as appears as a massaic of uniform background with bright

granules, it is also called "Photosphere" and is source of our heat and light.

CHROMOSPHERE - It is a 10000 Km this transparent layer of rarified gas, it is so called

because of its red colour. The third and last layer is called as "Carona" It is made of

highly ionised gases and extends for millions of kilometers in to space

• Mass, M = (1.991+0.002 )x 10 36 kg

• Radius, R = (60960 + 0.001) x l08 km

• Average density = 10410 + 0.002 gm/cm3 ( about 100 limes that of water )

• Distance from earth = 1.5 10 8 km

• Average surface temp, T = 5762 + 50 0 k

• Temp of core = 1.5 x107 0 k

N.P.T.N. Achalpur 2


CAUSE OF SOLAR EFFECT

The sun’s great energy releases is the result of an elaborate chemical process in the

sun's cores, A process of thermo nuclear fission will the reaction in hydrogen bomb At the

tremendous heat of more than 45 million degree of farenhite in the sun's interior, hydrogen

atoms fuse with helium atoms to produce the energy that powers our planets, so that

energy can only be released in the from of radiation rays of heat energy.

SUN EARTH RELATIONSHIP

The eccentricity of our earth's orbit is such that the distance between the sun and the

Earth varies by 3.4%. The angle subtended by the sun at mean earth varies distance of one

astronomical unit is 320. The characteristic of sun and its special relationships to earth result

in a nearly fixed intensity of solar radiation on the earths atmosphere.

SOLAR CONSTANTS

The sun, which is also known as " The Furnace In The Sky" shoots into our

atmosphere at a fairly consistent rate. Thus the energy received by the Earth which is

supplied by the Sun, per unit time, per unit area of surface perpendicular to radiation in the

space called the 'Solar Constant' and it can be measured first on sq. foot of the outside of the

Earth's protective layers gets a whopping average of 108.36 kcal/hr

SOLAR RADIATION

"Photons" are the tiny solar energy units contained by each of the sunlight waves.

And these units are being fired at earth by the sun. They arrive in shorter wavelength, means

more photons and thus more power.

Most of the solar radiations reach the Earth in the form of electromagnetic wave, of

about 0.2523 microns wavelength. About half of this radiation is visible light and rest is

infrared which accounts for heat. The sun that actually reaches us is about 80% of visible

light, 4°/o of ultraviolet light and 16% infrared. A very high percentage of this great energy

can be captured if we have right equipment.

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GLOBAL, DIRECT & DIFFUSED RADIATION :

There are three different forms in which sunrays come to us. They are

1) Direct parallel rays.

2) Diffuse radiation

3) Global radiation

Some part of solar radiation entering the atmosphere is absorbed in atmosphere some

is scattered and the rest penetrates the atmosphere. The penetrated rays are called “DIRECT

RADIATION”

Due to presence of “OZONE LAYER” most of the solar radiation are screened out,

making life on earth possible. A lot of solar energy is reflected off, or absorbed, by our

atmosphere and bounced back into outer space by clouds. When there is haze, cloud-cover,

smoke or dust in the air, the parallel pattern is broken and rays are reflected off in many

different direction by those particles of water or heat & light often seem to come at us from

all parts of the sky. “DIFFUSE RADIATION” as this is called is still very strong and is

useful to us if we have the right kind of solar collector. The term, diffused radiations means

the relatively short wavelength radiation.

Global solar radiation includes all the radiation, direct & diffuse incident on a

horizontal plane. It also includes “REFLECTED RADIATIONS” which has been bounded

straight of some surface.

ABSORPTION OF ENERGY BY THE EARTH

Only a small fraction of solar energy emitted by the sun is intercepted by the earth,

here is what happens to the solar constant. Once solar rays heat our atmosphere -

(A) 5% is reflected of clouds,

(B) 20% is reflected of the haze,

(C) 23"/o reaches the ground as diffuse sunlight,

(D) 25% is absorbed in the atmosphere and

(E) Only 27% actually reaches us as direct parallel rays i.e. Beam radiation.

N.P.T.N. Achalpur 4


After most of the strongest and most harmful rays have been filtered out, and a large

share of the sun's energy has been dissipated. The average solar intensity on the ground is

still 565 Kcal / hr. m2.

BASIC EARTH SUN ANGLES

In order to understand what follows for the calculation of solar radiations the

definition of some of the basic terms are given.

(i) LATITUDE

It is the angle between the line joining the earth centres to the location and the

rejection of line on the equatorial plan OR it may be defined as angular distance north or

south of the equator measured from centre of earth.

(ii) LONGITUDE

The longitude is the angular distance of location, measured east or west of the prime

meridian & from the prime meridian itself.

(iii) HOUR ANGLE

It is the angle through which the earth must turn to bring the meridian of a point

directly in the line with the sun's rays. At solar noon the hour angle is 00 and it expresses the

time of a day with respect to solar noon. It is measured positively westward from the

observer and it may be expressed in hours, minutes and seconds, degrees minute, radians.

(iv) SUN'S DECLINATION

It is the angular distance of the sun's rays north ( on 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 propagation of this line upon the earth's equatorial plane.

N.P.T.N. Achalpur 5


(v) ORIENTATION AND TILT

Sunlight is to be collected in between 15 to 30 degree either north or south of the

equator, because most of the radiation is quite direct and there are few clouds. Its accident

that this is where the world's greatest deserts are one if we got beyond 35 degrees north or

south there is a strong effect on insolation caused by changes in the seasons.

When we move further north ( or South ) we have to plan carefully on orienting a

solar collectors in relation to the sun. The rays must hit the collector at close to right angles

as much of the time as possible As latitude gets higher, solar collectors have to tilted more

and more towards vertical.

The collector are oriented north south and normally recommended angle for a fixed

solar collector is the latitude of the place plus 10 to 15 degrees. The energy absorbed by

straight of some surface.

THE ENERGY CRISIS

Quality of human life has undergone a significant change over the last four hundred

years. Though today, the people of some countries are more affluent than those in others,

the dispirely was much less in primitive times. Man had then to provide for all his needs on

his own, using wood for his requirement of cooking and for keeping warm. The major

economic inequality cause about the industrial revolution of the seventeenth century in

Britain and to the other countries in west later. The process of mechanization started with the

development of steam engine, which increased the demand for fuel and precipitated the first

energy exists in Britain in the form of an acute shortage of trees resulting in large shortfalls

in the supply of iron. The situation, however, improved when coal replaced wood as fuel

and replaced charcoal as the reducing assent in the furnace. The industrial revolution created

new techniques, which increased productivity and could support more people.

Towards the end of nineteenth century, coal & steam based industries had reached

their peaks and novel sources of energy were at their threshold.

The emergence of oil as a primary fuel and the discovery of electric dynamo brought

about a dramatize change in the pattern of life. In life of European countries,

simultaneously, the IC engines were progressively coming into greater use of transportation

and other industrial and form machinery. After the second world war, oil was much cheaper

N.P.T.N. Achalpur 6


than coal and most industries changed from coal to oil increasing the demand of oil very

sharply. This changing pattern of fuel utilization with heavy industrialization and machine

dependence of western society in particular has led to the shortage of fuel supplies

commonly referred to as "Energy crisis". It is interesting to look into present day pattern of

world in relation to the energy sources and option for the further. The oil embargo in

autumn of 1973 followed by fourfold increase in the oil has had major international

repercussions, prior to the embargo, the major industrialized countries of Western

Europe and North - America as well as Japan had become increasingly dependent on low oil

as a major energy source. This was also true for developing countries, which depended on

petroleum products, not only for their energy needs but also as a source for modern

fertilizers so necessary for increased agriculture productivity to meet the needs of their

growing population. This has further added oil to the so called 'Energy Crises'.

AN INQUEST OVER ENERGY CRISIS

Because of present energy supplies are both final and non-renewable, our energy

storage appears to be coming to an end. Warning signs in the from of oil shortage &

blackouts have been given.

There are also factors affecting energy production that have more to do with political

and environmental decisions than with dividing natural resources. Antipollution measures

have curbed the used of high sulphur coal. Construction of new nuclear power plants has

been opposed on ground such as safety and radioactive disposal waste; offshore exploration

for oil and gas has also been solved by environmental concerns.

Solar Energy - Solution On Energy Crisis

Solution for the energy crisis are strongly dependent on the technology of how well

energy is provided and used To make a physical change in the world it is necessary to use

tour resources-energy, matter, space and time. How well a task has been performed can be

measured in terms of fuel consumed, the mass of material used the space occupied, the

house of labour is accomplish and the ingenality with which these resources are used.

Squandering of irreplaceable energy sources, waste of material or large expenditure of space

and time can't be tolerated if the necessities of life are to be provided for all.

N.P.T.N. Achalpur 7


Renewed interest in the solar energy has manifested itself in a variety of ways.

Research and development projects sponsored by different countries and private

agencies, seminars , symposis and work-shop at national and international levels, efforts by

industries to implant solar technology in its programme etc. This interest in the outcome of

the recognition of the potential of solar energy as a viable supplementary source of energy

and it should be sustained by a systematic and concerned efforts. Solar power seems to hold

much promise for the future, as apart from its non-polluting qualities. The amount of

energy which is available for conversion is several orders of magnitude greater than all

present world requirements Moreover solar technology can be developed in less

sophisticated laboratories with less expensive equipment's. The economic probability of

solar energy utilization depends upon efficient collection, conversion and storage.

Applications of Solar Energy

The sources of all energy on Earth is the Sun and the energy flow from the sun to

main consumption permit as shown –

N.P.T.N. Achalpur 8


THE SOLAR OPTION

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

interrupted is approximately 1.8 x 10 MW, which is many times larger than the present

consumption rate on the Earth of all commercial energy sources. Thus, in principle, solar

energy could supply all the present and future needs of the world on a continuing basis.

This makes it one of the promising of the unconventional energy sources In addition

to its SI/A solar energy has two factors, first unlike fossil fuels and nuclear power, it is an

environmentally clean source of energy secondly it is free and available in adequate quantity

in almost all parts of the world where people live The main problem is that is attitude source

of energy. Consequently large collecting areas are read in many applications and these result

in excessive initial cost. A broad classification of various methods of solar energy utilization

is given in table below.

Solar Energy Utilization

Direct Method Indirect Method

Thermal Photovoltaic Water Wind Biomass Wave Ocean Power Energy Temp Difference

Some of the practical solar energy applications are as follows -

1) Water heating

2) Air heating

3) Power generation

4) Cooking

5) Distillation

6) Refrigeration

7) Drying

8) Solar pond

9) In Space Vehicles.

N.P.T.N. Achalpur 9


A DECADE OF SERVICE

Energy forms the Basis and a deciding factor in a country's development because if

not only affects the economic but also affect the social, environmental and other sectors

related to it. Concerning about these, science and industries dept. established a research

center CASE in India, which would take responsibility of policies for development of

infinite energy.

Admiring the important work (research) of NRSE over broad work technology in

1982, of India established (founded) Non-constraint energy sources dept. DNHS which

was then converted (transformed as) complete dividing Non-Conventional energy sources

ministry and NES in 1992. At present the of MNES has 9 divisional offices and 27 state

model agencies spread all over India

It has been known since a long provide that solar energy will render energy to few

limited sectors Therefore there will be limited contribution, on the other hand it is said that,

it will be more costly than conventional energy sources.

Sr. No.

Sources/ Technologies UNIT ACHIEVEMENTS(UP TO 31/3/1997)

A POWER GENERATION

1. Wind Power MW 900

2. Small Hydro Power (up to 3 MW) MW 144

3. Biomass Power MW 834. Solar Photovoltaic Power MW/Sq. Km 285. Urban and Municipal Wastes MW 3.75

a) Installed MW 90.00b) Being taken up

B THERMAL APPLICATIONS

6 Solar Thermal Systems MW/Sq.Km400000

a) Solar Water Heating Sq. Mtr. Collector

b) Solar CookersArea.Nos. 430000

7. Biogas Plants No. in Millions 2.5

8.Improved Biomass Stoves(Chulha)

Nos. in Millions 23.7

N.P.T.N. Achalpur 10


Solar Electricity Production capacities (M.W.)

No. Tax, No. Govt. Help

1995 2005 2015 2025 2035

Biomass 0.04 2.28 4.23 6.57 8.87

Solar P.V. 0.00 0.15 0.34 0.64 2.90

Solar Hybrid 0.00 0.08 0.25 0.72 2.08

Geothermal 0.00 0.02 0.06 0.12 0.19

Wind 0.45 0.88 1.59 2.46 3.46

Small 0.25 0.62 1.35 1.97 2.5

Hydroelectric

co-production

0.02 0.22 0.54 0.96 1.44

TOTAL 0.76 4.24 8.36 13.44 21.62

Extra Govt. help

Biomass 0.04 3.78 7.52 11.27 15.00

Solar P.V. 0.00 0.25 1.36 4.71 10.72

Solar Hybrid 0.00 2.48 5.02 7.66 10.32

Geothermal 0.00 0.09 0.24 0.41 0.50

Wind 0.45 5.32 8.17 10.26 12.34

Small 0.25 1.45 3.44 4.31 5.00

Hydroelectric

co-production

0.02 0.71 1.66 2.49 3.50

TOTAL 0.76 14.08 27.41 41.11 57.36

Constant Tax.

Biomass 0.04 2.81 7.87 11.27 15.00

Solar P.V. 0.00 1.03 4.71 15.80

Solar Hybrid 0.00 0.68 2.11 5.99 12.23

Geothermal 0.00 0.06 0.20 0.39 0.50

Wind 0.45 1.66 3.76 8.41 16.86

Small 0.25 1.25 2.90 5.54 10.10

Hydroelectric

co-production

0.02 0.41 1.01 1.95 3.50

TOTAL 0.76 7.12 18.88 35.26 73.99



WATER HEATING

Water heating is one of the solar energy application Water at ambient temp is sent

through tubes contained in the collector. The tubes are generally made of copper or

aluminium. For continuous flow of hot water, mass flow rate of water is maintained low

The solar radiations passing through the glass cover and strikes over the tubes which are

coated, with dull black colour and whose absorptivity is high. The tubes containing water

heats up and conveys, their heat to water inside it ( convection) . The water inside the

tubes get heated and we can get hot water at outlet at temp. about 700 C to 800 C .

The hot water obtained at outlet may be stored in a insulated storagetank and used

for further purpose.

TYPES OF CONCENTRATING COLLECTORS

A no. of concentrater collector are possible to increase the solar radiation flux on

absorber. These can be cylindrical to focus on a line or circular to focus on a point. The

absorber can be concave, flat or convex. Hence concentrating or focusing collectors may be

considered in two general categories:-

1) Line focusing and

2) Point focusing types.

As per the number of concentrating collectors geometries, the main types of

concentrating collectors are:

1) Flat plate collector type.

2) Compound parabolic concentrator type.

3) Cylindrical parabolic trough collector type.

4) Mirror strip reflector type.

5) Fresnel lens collector type.

1} FLAT PLATE COLLECTOR TYPE

A flat plate collector as shown in fig. 1 with adjustable mirror at the edge to reflect

the radiation on to the absorber plate is known as plane reflector or plane receiver

concentrating. These are simple in design having concentrating ratio slightly above the

unity. Lengths between two to four meters and are useful for attaining temp. to 1200 C to




Fig 1

Fig 2

Fig 3


1400 C which are slightly above the temp. of flat plate collector. The inclination angle of the

reflector is given by

= (A-B-ad + as ) / 3 Where, B = slope of the collectors.

The surface of the absorber plate may be, a black paint with an appropriate primer or

coating the selective material by electroplating. The primer coat should preferably be thin,

since a thick under- coat of paint would increase the resistance to heat transfer. The primer

should be of self etching type.

2) COMPOUND PARABOLIC CONCENTRATOR TYPE

The CPC concentrator is as shown in fig. 3 It is also known as winston’s collector.

CPC is a trough like arrangement, of two facing parabolic mirrors. The CPC is non-

focusing, but solar radiation from many direction is reflected towards the bottom of

the trough. Because of this characteristic, a large proportion of solar radiation, including

diffused ( scattered ) radiation, entering through the opening is collected on a small area. In

addition to collecting both direct and diffused radiation. An advantage of the CPC is that the

it provide moderately good concentration, although less than a focusing collector is an East

-West direction without adjustment for sun tracking, it is possible to concentrate solar

radiation by factor of 10th without directional tracking. Using this type of collector temp.

range obtained is up to 400°C.

3) CYLINDRICAL PARABOLIC TROUGH COLLECTOR TYPE

The cylindrical parabolic collector as shown in fig is also referred to as a parabolic

trough or a linear parabolic collector. The basic element making up a conventional collector

are:

1) The absorber tube located at the focal axis trough which the liquid to be heated flows.

2) The concentric transparent cover.

3) The parabolic concentrator.

The aperture areas of commercially available collector ranges from l to 5m2 with the

length being larger than the aperture width concentration ratio range from 5 to 30, & rim

angles from 800 C to 1200 C the temp. range obtained in between 3000 C to 6000 C.

The absorber tube of usually made of mild steel or copper & has a dia. of 2/5 to 5

cm. It is coated with heat resistant black paint as it is generally surrounded by a concentric



glass cover with an annular gap of 1 to 2 cm. In the case of high performance collectors, the

absorber tube is coated with a selective surface like black-chrome and the space between the

tube and the glass cover is evacuated.


Fig 4

Fig 5 Fig 6


The reflected surface is often made from anodized aluminum sheet. Aluminized

miler or aluminized acrylic fixed or a parabolic contour & curved black silvered glass a new

absorbed .All these materials have good secular reflectivity.

4) MIRROR STRIP COLLECTOR

This collector receiver has a fixed concentrator and moving receiver. The

concentrator is an array of tiny, narrow, flat mirror strips fixed along a cylindrical surface.

The mirror strips produce a narrow like emerge which follows a circular path as the sun

moves. This path is on the same circle on which the mirror strips are fixed. Thus the receiver

has to be moved along the circular path. The concentrator ratio for such lies between 10 to

30 and temp. achieved is up to the range of 5000 C .

5) FRESNEL LENS CONCENTRATING COLLECTORS

The fresnel lens concentrating collector has been developed utilized the focusing

effect of a fresnel lens. For a trough type of collector the leans in rectangle about 4 -7m. in

overall length and 0.95 m. in width. The fresnel lens is a thin sheet, flat an one side with fine

longitudinal grooves on the other. The angles of these grooves are such that radiation is

brought at a line focus. The lens is usually made of entrusted acrylic plastic sheets-line

focusing collector usually have concentration ratio between 10 to 30 and yield temp.

between 150° C to 3000 C .

TYPES OF SOLAR COOKER



"Food cooked by Solar heat is lovely in appearance, aroma,

flavors and taste. It is the ultimate medicine for manly

vigour and glorious skin complexion"

India is consider to be land a land of villages and in villages the major portion of

energy i.e. 95% is consumed for cooking. The conventional fuel like coal, kerosene cooking

gas, firewood, fire woods cattle during cakes and agricultural wastes, which are in user

getting depleted. The conventional fuel which are in used are now reducing day by day as

the population is increasing, increasing consumption of fuels. These conventional fuel

creating an havoc to the health of a man by polluting the environment. So it seems

necessary to developed a cooking system which is non-polluting and the fuel used for

cooking on the system should be available in abundant and therefore the birth of solar

cooker using sun's radiation which are available in abundant and are non-polluting made the

solar cooker to gain its popularity through out the world.

In India the first solar cooker is made by Adam way-back in 1876 using plate mirror

arranged in the light sided paramedical structure. Up till now several cookers have been

developed by various institution working in the field of non-conventional energy sources. In

India there are basically three design of solar cookers developed.

They are,

1) Flute plate box type solar cooker, single or multi reflector type.

2) Multi reflector type solar oven cooker

3) Parabolic concentrator type solar cooker

VARIOUS TYPES OF SOLAR COOKERS

1. ADAM'S SOLAR COOKER

Adam, an Englishman, was the first man in India who started investigating the

various solar devices. He was the man responsible for introducing the solar cooking

technique in India. He may be called as an inventor of solar cooker in India. He used plate

mirror arranged in an eight sided paramedical structure for his solar cooker. It was about 2

ft. 4 inches in diameter at the longer end. The food box was placed in cylindrical copper

container enveloped by a glass cover.



2. ABBOT’S SOLAR COOKER

The other man, who worked in field of using solar energy for cooking was ABBOT.

He made is a solar cooker in 1939. The cooker was an indirect type, in which there was an

parabolic fluid coil was heated to a high temp. (Up to 6000 F) using solar radiation's and then

was circulated through a sort of an exchanger, which in task heated the cooking over.


Fig 7


For this, 60 gallons of oil was used for heat transfer and storage. The size of

concentrator used for heating the fluid was 4 ft. X 8 ft.

3. BOX TYPE COOKERS

i) SINGLE REFLECTOR TYPE

This is of the simplest solar cooker being developed in India. The maximum no load

temp. Attained in this type of cooker was 1600 C. It is developed for convenient and

efficient performance. The cooker requires the adjustment after every 30 minutes towards

the sun. The food like rice, potatoes, vegetables and dal was satisfactorily cooked in this

cooker simultaneously. The food remains warm at the time of dinner.

ii) PARABOLIC REFLECTOR TYPE SOLAR COOKER

This type of cooker is being developed at physical laboratory in New Delhi and at

central Arid Zone Research Institute, Jodhpur. The cooker consists of a parabolic reflector

and the cooking box is placed at the focus of the parabolic. The reflector is made either of

small pieces of round glasses pasted on a sheet which is curved in parabolic shape or of this

Aluminum sheet. When this cooker was experimented it was observe that when the bottom

of the pot is blackened one litre of water boils within 25 to 30 minutes. Under the clear sky

condition and wind speed up to 3 to 4 km/hr. While when a wind speed is about 10 to 15

km/hr. The water never reached the boiling point and the maximum temperature record

under such conditions was 700 C to 800.

The performance of cooker is very much by the wind speed and the dusty

atmosphere. There are always chances of dust falling in the cooking pot and this cooker

cannot withstand the pressure. This requires frequent adjustment towards the sun after every

10 to 15 minutes and continuous stirring to prevent scorching of food.

iii) SOLAR OVEN

These cooker are used for cooking purpose. The insulated over has glass windows to

admit the solar radiation. Dr. Telka developed an oven which is an insulated box with a

cooking vessels of 10 sq. inch fitted towards the sun and adjusted every half an hour as

the sun moves during the day. Four slanting reflector of bright aluminum at the sides of the

oven reflect the light down through the windows into the oven temperature about 2000 C and

higher more obtained.




Fig 8


Another design was made at central Arid Zone Research institute Jodhpur, installed

in villages for demonstration cum test purpose.


Fig 9


This is multi reflector type. The reflector of this type of solar cooker is made of

Aluminum sheet shaped inform of octagon (Four of square shape and four of triangular

shape) and on which silvered painted mirrors are placed. The box portion of this cooker is

made up of wood and is parabolic in shape. It is rather a complicated type cooker which has

got many parts also needed precision fitting.

iv) REFLECTOR TYPE COOKER

This cooker consist of reflectors which are inclined at 600 to 700 is the most suitable

angle for concentrating most of the reflector rays at the centre of the box. Construction of

this cooker is simple and easy. The temperature of 950 C – 1000 C was obtained in this

cooker. In summer the time is required to reach the above temp. is 45 minute to I hour and

in winter it is one and half hours.

v) FOLDING - TWO STEP ASYMMETRIC REFLECTOR SOLAR COOKER

The design of this type of solar cooker retain most of the desirable feature of the

single reflector box cooker . It differ from the box cooker in the following ways.

A new reflector system named as folding two step a symmetric reflector has been

used in place of single reflector used in box type std. Solar cooker. This new reflector

system enhances the solar input into the hot box appreciably as compare to single reflector

cooker. The concentration of this cooker is 2.

It is rectangular in shape and of size 40 x 85 cm. It consist of a hot box and reflector

assembly. Performance of this cooker was studied in Ludhiana. The maximum temp

obtained was 1720 C (tracking mode) 1670 C (fixed mode) was obtained.

vi) KISAN COOKER

This is one of the simplest cooker being developed in India. These cookers use

mainly prepared in villages. A hole of size 12 ft x 12 ft is digged in the ground. The hole

digged in the ground is exposed to sun rays throughout the day. A blacked tray is placed

inside the hole after packing the sides of pit by straw paddy, husk of ash or glass wool. The




Fig 10


farmer can place the utensil with food inside the blackened tray cover the tray with the glass

cover and leaves it for his work. After 3 to 4 hours according to weather food is ready.

4) LEN"S TYPE COOKER


Fig 11


In this type of cooker the utensils are placed at the focus, where the sunrays are

concentrated through convex lenses. Up till now solar cooker based on this principle of

deflection grating have been developed which is reported to be quite effective.

The various centres working in the field of unconventional energy sources are

researching on developing a new type of lens cooker in which water is placed inside curved

plastics sheets. Some successes have been achieved in this field and it has given good results

but a lot more it to be done in this field of solar cooker development.

5) PLASTIC REFLECTOR SOLAR COOKER

In this type of solar cooker plastic sheets were used Reflector shape is parabolic

cooking unit comprising such reflectors in combustion, with suitable supports of food

holders used in the solar cookers were fabricated by plastics. Recent model used in drape

formed high impact polystyrene shell of a thickness of 0.6 stiffened at the sun with a ring of

thin wall aluminum tubing of about one half inch diameter. These shell are light in weight

are sufficiently stiff and use resistant to damage by bending and are readily formed in

compound curvatures required by simple forming technique. A reflective lining of

aluminum polyester film is Applied to the shells with adhesive so that the clear films forms a

protective covering over the secular surface. The secular reflectivity of this material when

new is in the range of 70 to 80 percentage.

6 ) SOLAR STEAM COOKER

This cooker is first developed at Brace Research Institute, Canada by R Award and

then modified in India by C. L. Gupta at Aero Solar International, Pandicherry and H.P.Garg

at CAZRI , Jodhpur.

This cooker is consist of a tube in flat plate collector and a well insulated steam

cooker. The collector plate, having an absorbing area of 0.75 m2 is made of sheet aluminum

with a copper pipe welded on it. The pipe is 3.5 m long and wound three fold. The copper

outlet of the pipe is connected to the bottom of the steam cooker. The blackened absorber

plate is placed in a wooden tray with double glass cover and 10 cm thick fibre



glass insulation. The inclination of the collector can be adjusted according to the geo-

graphical latitude.

In this cooker water starts boiling with in 30 to 45 minutes of sunrise and continue to

boil till the sun shines on the collector. This is very slow cooker and can be used for boiling


Fig 12


of cereals, rice, potatoes, dal, vegetables etc. The only advantage of this type of cooker is

that it does not required any adjustment towards the sun.

7) HAND REFLECTING SOLAR COOKER

Hand Reflecting Solar Cooker developed by Roger Bernord. In this the cooking pot

is kept in double wall glass case, it serves the purpose of hot box. The reflector surface is

consist of several small mirror fixed to focus on glass case. The system can be attained

temperature of 2500 C – 3000 C in a short time. To maintain constant temp. Inside box some

times iron chips are used which stores the energy and increase during low sun shine hours.

If solar intensity of 900 - 1200 watt per sq. meter for rice, omelets and roasting,

45, 15, 90 min. Respectively wats per sq. meter the cooking time for rice. omelets and

roasting ,45,15,90,min. respectively.

SOLAR COOKER CUM WATER HEATER

As the technology grows, more and more attention is paid to increase the

performance of any technology. The efforts are made to increase the output of the product.


Fig 13


The research and developments are continuously going on to achieve the flexibility in any

machine or equipment. The result is that multipurpose products are

coming into market which has more number of uses as compare to the old one.

The idea of solar cooker cum water heater is a step in the same direction. There is lot

of solar cookers and solar water heaters are developed in India. But if we go under the

analysis of cooking and water heating-then we find that water heating is generally required

during morning hours and cooking is required at noon. To achieve these goals by solar

applications, requires separate cooker and water heater, which is consumable one.

Hence the idea of solar cooker cum water heater came into picture.. There is a lot of

space available inside the solar cooker. If we fit a copper tubing inside it. Then our duel

purpose can be solved satisfactorily. This arrangement of the Copper tube do not consume

large space and can be fitted easily without disturbing the cooker mechanism.

In our project the inside box of cooker has semicircular portion ( 35) at bottom

height of 32.5 cm and width 35 cm. We can easily place a copper tubing in the plane of

bottom semi-circular portion. To increase the volume of Copper tube inside the box so that

it capture large amount of heat the tube is bended in U shape proper lengths. Then this

bending increases the length of tube in less space. The bending is done accurately and

proper care is taken so that, the tube should not damage during bending. Then this folded

tube is given a curvature as that of curvature of the bottom surface of inside the box. An inlet

and outlet is provided at proper positions. The inlet is connected to water supply tank. Thus

the solar cooker cum water heater is ready for operation.

SELECTIVE SURFACE

Such surfaces lire desirable because they maximize the absorption of solar energy

and minimizes the emission of radioactive loss. Thus they help in increasing the collector

efficiency.



Metal oxidized by heating give rise to spectrally selective surfaces from the

Antireflection oxide Films. These films may be rough, porous, non-homogeneous and

absorbing as well. However, it is found that spectral and directional characteristics of

oxidized titanium has sufficient interference effects.

The desirable material for selective absorber should have the following Properties.

1. Low reflectance.


Fig 14


2. A resistance to atmospheric attack or vaporization in space.

3. A sufficiently low absorption co-efficient in infrared region and high absorption

coefficient in the visible region.

4 Its properties should not change with its use.

5. It cost should be reasonable.

PROPERTIES OF SELECTIVE COATINGS

An efficient utilization of solar energy requires collector surface with the following

optical and physical properties.

Absorption over the solar spectrum (0.3 - 2.0 micro meter) must be high.

Emissivity for wavelength greater than (0.2 micro meter) must be low.

The spectral transition between the region of high absorption and low emittance

should be as short as possible.

The optical and physical properties of the coating must remain stable under long

term

Operation at elevated temps repeated thermal cycling, air exposure, ultraviolet,

Radiation, etc.

Adherence of the coating to the substrate must be good.

Coating should easily applied to collectors of desired size and shape.

Coating must be economical.

PROPERTIES OF SOME SELECTIVE SURFACES

S.N. SURFACES ∝ E1. “Nickel Black” Containing oxides and sulphides of

Ni and Zn, on polished Ni

0.91-0.94 0.11

2. “Nickel Black” on galvanized iron 0.89 0.123. “Nick Black” 2 layers on electroplated Ni on mild 0.94 0.07



steel4. CuO on Ni, made by electrodeposition of Cu and

subsequent oxidation.

0.81 0.17

5. Co3O4 on silver, by deposition and oxidation. 0.90 0.276. CuO on Al, by spraying dilute Cu(NO3)2 solution on

hot Al plate and baking -

0.93 0.11

7. “Copper Black” on Cu, by heating Cu with

solution of NaOH and NaClO2

0.89 0.17

8. CuO on anodized Al, treat Al with hot Cu

(No3)2 – KmnO4 solution and bake

0.85 0.11

9. Black chrome on Aluminium, steel 0.87 0.8810. Lead sulphite crystals on Aluminium 0.89 0.20

DESIGN AND CONSTRUCTIONAL DETAILS

DESIGN OF REFLECTOR

In any design of solar equipment the first requirement is to decide the area

through which the solar radiation enters. The efficient working of solar equipment can be

achieved only when the required amount of solar radiation enters in the equipment. For our

project it is necessary to determine the aperture area through which solar radiation enters.

a) Aperture area from heat requirement point of view.



The present equipment is designed to fulfill the requirement of a family of four

members. The requirement of a family is about 250 gm of rice. Similarly the family requires

hot water for different needs like bathing, cleaning etc. throughout the day.

I) The heat required to cook

250 gm of rice = The latent heat of 300 gm. Of water + Sensible heat of water and rice +

heat of reaction between water and rice for water to penetrate into rice.

Total heat required to cook the rice = Heat required for vaporization of water +

sensible heat of water and rice + Reaction heat

II) Latent heat of water for vaporization = 2257.2 KJ/Kg

Heat required for 300 gm. Of water = 1000

2.2257300 ×

= 677.16

III) Sensible heat of rice = 41.8 KJ

IV) Sensible heat of water = mw Cpw Tw

=0.3 x 4.186 x (95-30)

=81.627KJ

V) Assuming the reaction heat i.e. heat required to remove the resistance of rice to absorb

the water as 836 KJ/Kg (from standard data book of food)

Reaction heat required for 250 gm. Of rice = 1000

250836 ×

= 209 0 KJ

Total heat required to cook the rice = 677.16+ 41.84+ 81.63+ 209

= 1008.63 KJ

The amount of solar radiation 's falling on the earth surface in Vidarbha region is generally

5016 KJ/m2 hr.

Considering the collector efficiency as 50 %

Required surface area for collection is, S= η×× 1

t

1

q

qt

Where, qt = Heat required

q = Amount of heat available

t = Time required for above operation



= 55 min. of efficiency of collector.

S= ( ) 50

1

60/55

1

5016

63.1008

S = 0.4387 m2

II) Considering the water heating process

Generally the water required for bathing and cleaning is should have temperature of

about 500 C.

Considering the flow of 150 ml/min, then the heat absorbed by the water can be as,

Q = mw Cpw Tw

= 0.15x4.186 x (50-25)

= 15.6975KJ/min

Hence heat absorbed in I hr = 941.85 KJ/hr

Hence the required collector area,

S= η×× 1

t

1

q

qt

= ( ) 5.0

1

6060

1

5016

85.941 ××

S= 0.3755 m2

We assume the maximum collector area required i.e 0.4387 m2 for further design.



b) APERTURE AREA FROM MATHEMATICAL CALCULATIONS-

We have chosen the multireflector type solar reflector, which has collector angle of

60° so as to reduce the reflection losses of glazing rays and to avoid the losses due to

shadowing. If we take collector angle to 90 then the purpose of use of reflector is totally get

diverted as the area on the top of the reflector will be same up to bottom, more over it also

disturb the entry of diffuse radiations. On the other hand if we have collector angle less than

30 then the reflected rays will not fall inside the box and may go outside. Hence the



collector angle is fixed as 60 due to which, the solar radiations get concentrated inside the

box.

From the ∆ OAB, we can calculate the length AB,

AB = Cos 60 x 0.35

= 1.75m

Now projected area of aperture = A(�PQRS) - 4 [A ( ∆ LMS)]

= (0.71 x0.71)-4(l/2x0.175x0.175)

= 0.44285m2

The designed aperture area is nearly equal to the fabricated one. Hence our design is

safe and we do further fabrication regarding to these design parameters.

2. DESIGN OF INNER BOX -

The inner box is so designed that a pot of capacity 1.5 liter can be kept easily inside

it. The bottom of the box is specially prepared semicircular for the arrangement of tubing for

water heating. A provision for fixing main absorber plate is also made so that the absorber

plate can swing freely about the point of pivots. An opening of sufficient and maintenance of

the equipment. After considering all factors it is finalized to have dimensions of box as

height of 32.5 cm with semi cylindrical bottom. The upper cylindrical surface area is of 35

cm x 35 cm.

3. DESIGN OF COPPER TUBING -

The Copper tubing is properly fixed on the bottom surface of the inner box. Taking

the area available for tube fitting and flow requirement a Copper tube of ½ inch (1 .27 cm)

outside diameter is selected. The width of inner box is 35 cm, hence we can easily fit a tube

in 5 rows having spacing of 7 cm in between two successive rows. The spacing between

rows is designed such that it gives freedom in bending process and bending can be done

easily with destroying the shape of the tube. To increase the more collective surface the tube



is given a round inside the box shown. The sufficient Copper tube is kept outside the

equipment for inlet and outlet attachments.

CONSTRUCTIONAL DETAILS

1) DESCRIPTION

The box type solar cooker cum water heater is a concentrated type collector system.

The solar oven is made of inner M.S. sheet box and outer wooden box, with a top cover

having a opening in which two plain glasses are fitted with sufficient gap (2 cm) in between

them. The inner box and main absorber plate is painted black with a selective material, so

that they can absorb maximum solar radiation’s. A multi reflector frame with mirrors is



mounted on the top. Provision is made to adjust the whole unit at different angles by

mounting the equipment in a frame.

2) MATERIAL REQUIREMENT

The material required for construction of solar cooker cum water heater is readily

available in market and the requirement is as under –

MATERIAL QUANTITY NOSWood (Kitply) 1m2

MS sheet 8 KgMS square pipe 410 cm

Glass wool 5 kgPlain glass mirrors (37.5 x 37.5 x 3 mm) 2 no

Reflector glass (35 cm x 35 cm x 3 mm) 4 no

Reflector glass(35 cm x 25 cm x 22 cm x 3

mm)4 no

Copper tube½ inch diameter, 16 BWG

gauge4 m

MiscellaneousNails, Nut & bolts, Handle, Rubber sealing, Roller wheels, favicol, fasteners, screws, Black & Colour paints, ms flat

wing nut etc.

3 CONSTRUCTION

The location of Achalpur 770 35 East latitude and 2005. North latitude. The

dimensions of solar cooker cum water heater are selected on the available solar intensity

basis so that maximum radiation’s reaching to earth surface can be utilized for cooking and

water heating. The overall dimensions of the unit are 85 cm x 60 cm x 54 cm and its weight

is about 35 kg.

A) OUTER WOODEN BOX

The outer semi-cylindrical wooden box is fabricated such that is has height 40 cm

and bottom radius 25 cm. The material used for fabrication is thick kitply. The box is

designed such that it will be suited for all climate conditions. The top cover of box has



center hole of dimension 35 cm x 35 cm. On this cover two plain glasses mounted with a

gap of 2 cm is between them. The rubber gasket is provided at all the edges of these glasses

to make it fix and shock proof. Both the glasses are fitted exactly over each other. On the

one side of box a window is cut of size 30 cm x 20 cm for easy placing and removal of

cooking pot. This window door is provided with handle for easy operation.

B) INNER MS SHEET BOX AND MAIN ABSORBER PLATE

The MS sheet of 22 gauge is used for fabrication of inner box. The

dimensions of inner box are height 32.5 cm, width 35 cm and length 35 cm. The bottom

surface is made semi-circular one with radius 17.5 cm. A window is cut on the same side as

that of outer box of same dimension. The box is fabricated by riveting and folding. A main

absorber plate is also fabricated of length 34 cm and height 15 cm. The aligned holes are

drilled in both ears of the tray, so that the tray can be hanged with nut and bolts are drilled in

both ears of the tray, so that the tray can be hanged with nut and bolts inside the box. Both

tray and inside box are painted with black paint (selective one) so that they could absorb

maximum solar radiations.

C) GLASS WOOL INSULATION

The glass wool which has low thermal conductivity (0.038 w/mk) is selected as a

insulating material. The glass wool is filled in between the spacing of inner and outer boxes.

The insulation is provided to minimize the conductional heat losses from the inner box.

D) COPPER TUBING

As per the design a copper tube is bend at suitable length so that it form a compact

structure with 5 rows. The bending process is done very preciously. First the sand is filled

inside the tue which provides a strong back-up support from inside and also allows smooth

bending. Then the tube is marked at regular intervals and then bending is done. The each

bending has ‘U’ shape. Then all the rows are bender with the same curvature as that of

bottom curvature of inside box. After the complete bending process the sand is taken out

from tube. Then the complete compact structure is fitted inside the inner box and inlet and

outlet connections are taken out by drilling holes at proper location. As the Cu tube is

ductile and any laziness can cause clogging of tube, proper care is taken during the process.



E) GLASS COVER

The glass has high reflectivity and as the solar radiation’s enters through it cannot

escape out easily. To avoid such reflections from inside two glass covers are fitted above the

box with a spacing of 2 cm in between them. If any radiations are reflected back from inside

then it strikes to glass cover and reflected again inside and thus, efficiency of unit is

increased.

F) MULTI-REFLECTOR

A multi reflector is having square shape at bottom and octagonal at the top. The

multi reflector is made up ms sheet. It consist of 4 square plates of 35 cm x 35 cm and 4

triangular plates of 35 cm x 25 cm x 22 cm. Then these plates are joined by welding to form

a reflector. Then mirrors are fastened to these ms sheets from the inside. Then this reflector

is mounted on the top of the outer box so that hole of reflector matches with the hole of

wooden box.

G) STAND

A stand is made from MS square pipe. The dimensions of stand are 60 cm x 45 cm x

45 cm. The stand has two triangular structures by the sides. Guide is also provided on one

side of stand, to make provision for adjusting the unit at required angle. The guide is very

important because tracking is required for all day so that the reflector face is always keep

facing towards sun. Then the assembled unit is fixed in the frame with the help of nut &

bolt at the centre of box.

COST OF FABRICATION

Material Specification Quantity Cost

(Rs.)1. Kitply 19 mm 1 m2 4502. MS Sheet 22 Gauge 8 Kg. 7753. MS Square - 410 624. Plain Glass 37.5 cm x 37.5cm x 3 mm 2 No 805. Mirror 35 cm x 35 cm x 3 mm 4 No 310

35 cm x 25 cm x 22 cm x 3 mm 4 No 2506. Glass Wool - 5 Kg. 2007. Copper Tube ½ inch F, 16 BWG 4 m 5208. Seal 100 gm 5 No 100



9. Rollers - 4 No 6010. Black paint - 750 ml 4711. Nails, Rivets, MS flat,

Wheel handle, wing next colour

etc.

- - 250

TOTAL 3104

TESTING AND PERFORMANCE

1. TESTING

The cooking and water heating trials of solar cooker cum water heater were

conducted on dates 02/03/03, 03/03/03, 10/03/03, 11/03/03 & 13/03/03.

And temperature was recorded on hously basis for ambient and inside of the solar

oven on the above dates.

For trial of water heater we heated water at different times throughout the day, at

different flow rates and tabulated the day, at different flow rates and tabulated the readings

obtained. We had cooked rice, pulse and had also boiled eggs for trial of the cooker.

The tests were carried out separately for water heater and cooker.

2. SAMPLE CALCULATION FOR SOLAR RADIATIONS.

The calculation for 20th March 2003 are as follows.

The PAGE suggested the relation,

+=

)S(

S)ba(

Ho

Hg

max

Where, Hg = average daily global radiations.

According to Klein,

Ho = )n365

360Cos 033.01(

Pi

Isc 24 +

x ( W8 sin θ sin δ + cosθcosδ ) sin W8



- a and b are the constant for location is equal to 0.27 & 0.5 respectively for Nagpur.

Date 20th March 2003

φ = 220 (latitude for Achalpur)

n = 41 ( no of day of year )

β = 0.9 = 0.9 x 22 = 200

Declination (δ) = 23.45 sin {360 (284 + n)/365}

= 23.45 sin {360 (284 + 41)/365}

= -14.90

Sunrise hour angle, W, = cos-1 (-tan (ϕ - β) tan δ)

= cos-1 (-tan (22-20) tan ( - 14.9 )

= 74.560 or 1.301 radiation

Day length, Smax = 15

)Ws2( ×

= ( 2 x 74.56 ) / 15

= 9.94 hours

Now,

Ho = ( 24/3.14) x 4871 { 1 + 0.33 x cos ( 360 + 41 )/365 }

x { ( 1.301 x sin 220 x sin ( - 14-9 ) }

+ ( cos 220 x cos ( - 14.9 ) x sin 74.560 }

= 28163 KJ/m2 – day.

Hg = { 0.27 + 0.5 (8.9/9.94) } x 28163

= 20212.19 KJ/m2 – day

= 2271.011 KJ/m2 – hr.

Heat required to cook rice = 1025 KJ

We require 1025 KJ of heat to cook rice and we are getting heat from sun per meter

squence of earth and per hour 2271.011.

The Solar instability measured by the pyranometer was found and recorded as below

Time Solar Intensity



Date – 15/03/03

(Reading with Pyranometer ) - 1 :10 5.12.0 5.23.0 5.3

Constant of measuring instrument = 5.2 mV / Cal /cm2 /hr

CALCULATION

S.1 = 5.2/5.2 mV/ Cal/cm2/min.

= (5.2/5.2) x 4.187 x 10-3 KJ/cm2/min.

= 4.187 x 10-3 x 104 KJ/m2/min.

= (41.87/60) KJ/m2/sec.

= 0.6978 KW/m2

= 697.8 W/m2

DESCRIPTION OF VARIOUS TABLES

Successful fabrication of this multi-reflector type solar cooker cum water heater was

done in workshop of our college.

The performance test were carried out on difficult dates it on 02/03/03, 03/03/03,

10/03/03, 11/03/03 & 13/03/03

VARIATION OF TEMPERATURE WITH TIME

Date of Test : 02/03/03 Atmosphere condition – Normal

Loading conditions – No load Starting Time – 10.00 A. M.

Duration of Test = 10.00 A.M. to 5.00 P.M.

Time

No load conditionAmbient Temp.

Inside Tem.

9.00 a.m. 220C 250C



10.00 a.m. 280C 450C11.00 a.m. 300C 820C12.00 p.m. 310C 1040C1.00 p.m. 310C 1140C2.00 p.m. 310C 1220C3.00 p.m. 310C 1180C4.00 p.m. 290C 1080C5.00 p.m. 280C 900C6.00 p.m. 260C 700C

Date : 03/03/03 With water heater (flow of water = 100ml/min.)Time Ambient Temp. Inside Temp. Water inlet Temp. Water inlet Temp.

9.00 a.m. 190C 220C 250C 250C10.00 a.m. 250C 320C 250C 290C11.00 a.m. 280C 500C 260C 320C12.00 noon 300C 800C 260C 340C1.00 p.m. 300C 840C 280C 380C2.00 p.m. 300C 850C 300C 420C3.00 p.m. 310C 950C

(with out water)

270C 420C

4.00 p.m 300C 800C

(with water)

260C 380C

5.00 p.m. 280C 650C 250C 320C6.00 p.m. 260C 600C 250C 290C

Weather – Little Cloudy

Date :10/3/03 With water heater

TimeAmbientTemp.

InsideTemp.

Water inlet Temp.

Water outlet Temp.

Flow of water

(ml/min.)10.00 am. 320C 750C 300C 700C 10012.45 a.m. 360C 870C 300C 500C 1502.00 p.m. 360C 850C 360C 500C 1003.00 p.m. 360C 840C 360C 470C 1504.00 p.m. 320C 840C 360C 420C 755.00 p.m. 280C 750C 340C 400C 150



Date :10/3/03 With water heating

Time

Ambient

Temp.

Inside Temp. Water inlet

Temp.

Water outlet

Temp.

Flow of

water

(ml./min.)10.30 a.m. 280C 700C 270C 390C 10011.30 a.m. 310C 850C 310C 450C 10012.30 p.m. 310C 850C 350C 480C 1001.30 p.m. 310C 900C 360C 550C 1003.30 p.m. 310C 800C 360C 550C 1004.30 p.m. 300C 700C 360C 510C 100

Date Dishes Quantity Starting time Time of

withdrawing

Time taken

to cook11/3/03 RICE 200gm rice

+300 ml water

2.45 p.m. 3.40 p.m. 55 min.

13/3/03 RICE 200gm rice

+300ml water

10.30 p.m. 11.30 p.m. 60 min.

14/3/03 PULSE 200gm pulse

+ 400ml water

2.00 p.m. 3.50 p.m. 110

15/3/03 EGG 1 No. Egg

+200ml water

1.30 p.m. 2.20 p.m. 50 min.

18/3/03 RICE 200gm rice

+300 ml water

10.00 p.m. 11.15 p.m. 75 min.

26/3/03 PULSE 200gm pulse

+ 400 ml water

2.45 p.m. 4.45 p.m. 120 min.

Date : 26/3/03 With water hearing

Time

Ambient

Temp.

( 0C )

Inside

Temp.

( 0C )

Water inlet

Temp.

( 0C )

Water outlet

Temp.

( 0C )

Flow of

water

(ml/min.)1.00 p.m. 34 76 30 45 100



2.15 p.m. 35 76 36 47 1003.15 p.m. 33 78 37 48 1004.15 p.m. 33 77 36 46 1005.15 p.m. 32 75 35 44 100Food Cooked 250gms of rice + 100gms Dal + 500 ml of water

Utensils made of thin metal with tight lids and painted dull black from outside are

best suited for the cooking. But it is possible to cook even with ordinary stainless steel

vessels but it requires more time. Use of tight vessel increases the pressure & temp. Inside

the vessed and lowers the cooking time lesser will be the depth of food faster will be the

cooking. For this the vessels with large bottom area are generally used. The maximum

height of food material, which can be used is 60 mm. If more amounts are required to cook

then use two separate vessels. Proper water quantity must be added with the food material

so that it facilitates the cooking in optimum time.

Cooking techniques with solar cooker can be classified as under –

1. As the supply of heat is from the top, convection current are set up hence slow process

of boiling of food. The hard foods like pulses are hard to cook and require more time.

Hence it is useful to soak these materials in water for 2 to 3 hours prior to putting in

solar cooker. Due to this the food will absorb same amount of water & becomes soft.

Then add less amount of water with it when it is placed for cooking.

2. Bread, Cake, Biscuits are prepared by baking process. Some vegetables like pumpkin,

Brinjals, tomatoes etc. requires some high temp. (1000C). Hence these have to cook

during peak intensity hours of the day, when sun is at zenith.

3. Some foods are better cooked with gradual rise of temp. such as milk preparations like

‘khir’, pudding and all root vegetables. They cook very delicious if they are cooked at

800C to 900C for longer time. Solar cooker is most suitable such applications during late

hours i.e. 3-6 p.m.

4. Food items prepared by process of roasting are also well cooked in the solar cooker. All

the roots like potato, sweet potatoes, groundnut etc. can be easily roasted in cooker



without any water. Eggs can also be cooked without water. For this the food items must

kept in open utensils or even directly on the absorber plate.

COOKING TIME AND TEMPERATURES

The optimum temperature necessary to start cooking and time for cooking after

reaching optimum temperature for different types of food are tabulated as under –

Sr.No.

Type of food

Optimum temperature

necessary to start cooking.

Time for cooking after reaching the

optimum temp.

1. Very easily cooked food such as

cabbage, carrots and leafy vegetables.700C 45 minutes

2 Easily cooked food such as root

vegetables, mug and rice750C 55 minutes

3. Harder to cook food like bread, cake

some vegetable etc.800C 90 minutes

4. Very hard to cook food like hard

unbroken pulses, meat, special dishes

etc.

850C 120 minutes

WATER HEATING

For water heating it is essential to adjust the flow of water as per requirement for

normal operation. The temperature of water can be raised from 250C to 550C with flow of

150 ml/min. on a clear shiny day. The temperature of water can be increased by decreasing

the flow rate. Low flow rate will allow the water to remain inside the box for more time and

consequently the temperature of water coming out of the equipment will be higher.

The maximum temperature of water is achieved during the period of 11 p.m. to 3

p.m. The collected data with different flow of water heater is as under.

Sr. Water flow Water inlet temperature Water outlet temperature



No. (ml/min.) ( 0C ) ( 0C )1 50 25 922. 100 25 773. 150 25 554. 200 25 47

ECONOMICS OF SOLAR COOKER CUM WATER HEATER

COMPARISON WITH TRADITIONAL METHODS :-

In traditional cooking and water heating some mean is used to produce fire and then

cooking material or water filled in some utensil is kept on this fire. The material of utensils

may be Brass, Steel, Copper or Aluminum. Thus the heat from fire is transferred to the

bottom of the utensil and then to the food or water through conduction & convection.

But in case of solar applications the heat in the form of solar radiations is enter from

the top of utensils and then this heat is used for cooking or water heating purpose.

1. In traditional methods flame temperature is very high hence cooking or water heating is

achieved in less time. But in solar appliances temperature is raised slowly hence the

cooking or water heating requires some more time. In other words the heat supply rate



in traditional methods is high about 1.0 to 1.5 kw. Whereas the heat supply rate of solar

applications is less i.e. 0.5 Kw. But the research and developments are growing so fastly

that we can a achieve application of solar appliances with less time, shortly.

2. The initial cost of solar applications is high as compared to others but its operating cost is

negligible. Hence the Customer can get his money back in short payback period.

Moreover the Govt. is giving about 40% subsidies on solar appliances.

3. Experimently it is provided that the food or water heated using solar radiations has

medicinal properties and is effective for good health.

4. Solar applications also has no pollution problem & hence eco-friendly.

We have carried out comparative study of solar cooking & water heating with some

traditional resources. In India conventional sources used for cooking & water heating are.

i) L. P. G. ii) Kerosene Oil

iii) Coal iv) Wood

v) Cattle dung cake vi) Electricity

The following analysis clearly indicates the effectiveness of solar cooking & water

heating over traditional methods.

1) LPG

Liquid petroleum Gas is the most widely used fuel in Urban areas, and its use is

growing rapidly day by day.

Assuming that 35 kg.of water is heated in a day and cooking is done for 2 time a day.

The total energy consumed in cooking –

a) Energy to cook 200 gms of rice = 840 KJ

b) Energy to cook 200 gms of Dal = 1000 KJ

c) Energy to cook 2 vegetable = 1500 KJ

Energy saved = ( mwcpw∇Tw) +2 (Energy saved in cooking)

= 35 x 4.18 x (50-25) + 2 x 3340

= 10337.5 KJ



Calorific value of LPG = 50000 KJ/kg

Amount of LPG saved per day = 50000

5.10337

= 0.2068 kg/day

Assuming that the equipment is used for 220 days in a year,

Hence the total LPG saved = 0.2068 x 220

= 45.5 Kg

Net amount saved per year = 45.5 x 10

= 455 Rs/year

The cost of LPG unit is 2000 Rs.

Pay back period = year per saved Amount

unit LPG of Costheater water cumkercoo Solar of Cost( −

= 455

20002400 −

= 0.879 years

2) KEROSENE

Kerosene is widely used for poor peoples and its calorific Value is 30000 KJ/kh

Amount of Kerosene saved per day =Kerosene of.V.C

saved energy Total

=30000

5.10337

= 0.3445 lit/day

Amount of Kerosene saved in 220 days = 0.3445 x 220

= 75.8 lit.

The total money saved = 75.8 x 4

= 303.2 Rs/year



=2.303

5002400 −

= 6.26 years

The cost of Kerosene stove is 500 Rs. Which is much less than solar equipment.

Payback period = year per saved Amount

stove osenekerof Costheater water cumkercoo solar of Cost −

3) WOOD

Wood is the most promising source of energy for the peoples living in ruler areas.

But use of wood has destroying effect is using of trees which results in environmental

imbalance. Hence use of solar appliances in rural area is the best.

calorific Value of wood = 16000KJ/Kg

Total amount of wood saved/day = wood of CV

saved energy of Amount

= 16000

5.10337

= 0.646 Kg/day

Total amount of wood saved in a year = 0.646 x 220

( assuming 220 days of working in a year) = 142.14 Kg/Year

Total money saved per year assuming = 142.1 x 2

= 284.28 Rs.

As cost of 1 kg of wood as Rs.2 as the cost of wood ‘Chulla’s is very small it can be

negelect.

Pay back period =saved Amount

heater water cumkercoo solar of Cost

=28.284

2400

= 8.44 years

4) CATTLE DUNG CAKE –



Cattle dung cake is the most cheapest (Free of cost) and popular energy source for

villagers.

The calorific value of cattle dung = 11500KJ/Kg

Amount of cattle dung saved =cake dung cattle of CV

saved energy of Amount

=11500

5.10337

= 0.8989 kg

Though the use of this fuel costs no money but it may be more effective if used as

agricultural fertilizer. As the cattle dung has more nutritious value then artificial fertilizers

and it also not contain any harmful chemical it is best as agricultural fertilizer instead of

fuel. Moreover the use of solar cooker cum water heater also saves the time, which will

consume in preparation of cattle dung cake.

5) ELECTRICITY –

In modern peoples the use of electrical water heater, ovens etc. is increasing rapidly

as it requires less time for cooking and heating and also is pollution free.

The cost of 1 kw-hr of electricity = Rs.1.25

Heat saved per day = 10337.5 KJ

Assuming available voltage = 230 V

And current (for a coil of 1000 watt) = 4.347 Amp.

Time required to produce the required heat =347.4230

10x5.10337 3

×

= 103375 Sec.



= 2.87 hrs.

Amount of saved in a year per day = 2.87 x 1.25

= 3.589 Rs.

Amount saved in a year = 3.589 x 220

(assuming 220 days working) = 790 Rs/Yr.

The cost of electric equipment is about 2000 Rs.

Payback period =790

20002400 −

= 0.51 year

DISCUSSION

COMMERCIALIZATION OF SOLAR COOKERS

Ever since the inception of Department of Non-conventional Energy Sources

[Presently Ministry of Non-conventional Energy Sources (MNES) ], the desire of the

government to popularize and promote solar cookers is evident. But So far, this has been

done without the active involvement of commercial interest. The few manufacturers of solar

cookers are really local entrepreneurs, without much support for manufacturing

infrastructure, R & D, and market development. Vehicles of promotion such as media

advertisement, provision of subsidy, marketing, testing, etc. had so far been in the control of



government agencies, chiefly the nodal agencies. The GEDA experience shows what can be

achieved and what cannot be. It is obvious that commercialization of solar cookers, whose

target market is clearly the urban middle class, is best done by leaders in the appliance

industry such as those making pressure cookers, electric ovens, etc. But the absence of a

similar product in the developed country markets does not enthuse the local manufacturers

to enter into development and production of solar cookers. One way to bring some

enlightened manufacturers into the solar cooker business is to provide incentives for product

development, such as cost sharing, R & D support from reputed institutes/individuals, etc.

The latter aspect is very important because without R & D support, development of a

product (solar cookers) – as special and as complicated in its own way – would not be

feasible. After the laboratory development and testing of a model, or indeed a range of

models, the product can be launched with a brand name, using the existing marketing

network of the manufacturer. As is the case with the growing buyers market in India, the

product is likely to undergo changes in design and appearance, but with consistent support

of the government. Solar cooker can make inroads into the vast and growing market of

domestic appliances in India.

SOLAR HEAT ENERGY PROGRAMME TARGET FOR NINETH PLANE (1997-2002)

I II III IV V TOTAL IX

Upto

1996-

971999-

98

1998-

99

1999-

00

2000-

01

2001-

02PLAN

Solar water heating34000

0

35000

(Target)

25000

0

37500

0

50000

0625000

75000

02500000

Solar cooker(Nos.)41000

0

25000

(Target)

10000

0

15000

0

20000

0250000

30000

01000000

Other Solar Systems 150005000

(Target)5000 5000 5000 5000 5000 25000



Slow-room 8 10 10 10 10 10 10 50Divisional testing

centre W/S in field

of solar thermal

6 50 50 50 50 50 50 250

W/S in field of solar

passive (Nos.)62 30 40 40 40 40 40 200

Broad programmes

Reports (Nos.)18 15 20 30 40 50 60 200

Demonstration(Nos.) 1 10 15 20 25 30 35 12520,00,000 Sq. meter domestic systems

5,00,000 Sq. meter Industrial systems

SALIENT FEATURES & LIMITATIONS

SALIENT FEATURES

1. No need of fuel, maintenance hence saves large amount of money.

2. Simple to use and easy to manufacture.

3. Cooking or water heating is not affected by wind hence more efficient.

4. No change of dust falling in utensils.

5. The food can be kept warm if kept inside the over for hours, even after sunset.

6. Due to multi-reflector type, maximum solar radiations are reflected inside the box and

maximum temperature can be achieved which makes the operation more fast.

7. A crodle like cooking platform is provided to keep the utensile horizontal irrespective of

sun.

8. The maximum inside box temperature can be achieved up to 2000C in summer and 1500C

in winter, on a clean day.



9. All type of nutritive delicious foods can be prepared like cooking, roasting backing etc.

10. The hot water can be collected throughout the day.

11. Under normal flow conditions ( 150 ml/min.) the temperature of water is achieved up to

650C on clear day.

12. The temperature of water can be varied by varying the flow flowing through tube. The

temperature of water can be achieved up to 900C if flow is maintained at 75 ml/min.

13. Easy for transportation as rollers wheels are provided.

14. The solar applications do not produce any pollution and hence Eco-friends.

15. Solar cooker is a domestic appliance. A domestic appliance has:

i) To perform a given task reliably at any time and in any place.

ii) To be convenient to use and

iii) To be aesthetically and economically attractive.

A thorough study of the market, product development, and market development,

which includes promotional campaign, establishment of a dealer network etc. by the

manufacturer are the usual steps involved in the process of launching a new product in the

market.

LIMITATIONS

1. One has to pre-plan the menu and has to cook according to the sun hours.

2. Time required for cooking & water heating is quite more as compare to the traditional

one.

3. The equipment is not effective during night, or during rainy or cloudy days.

4. One has to continuously adjust the equipment in the direction of sun.

5. The equipment should be placed at such place where the sun rays can enter directly

and is available for whole day without any shadow disturbances. Generally it should

be kept on terrace of home.



6. Water poured in food material for cooking utensils and may get condensed on lower

surface of glass. This reduces the transmissivity of the surface and lowers the

efficiency. Hence frequent cleaning of the bottom surface of glass is required.

7. It is too bulky and unwidely to use.

8. The spacing between two glazings can not be cleaned.

With such dire limitations, the question is whether it is possible to commercialize

solar cookers at all. Or, the question can be posed in a different way. Considering

the limitations of using an energy source such as solar which is characterized by a

low energy density and wide fluctuations in intensity, what kind of product could be

developed, that is marketable and user-friendly ? From this point of view, some

basic issues of solar cooking have to be examined closely.

CONCLUSION

The energy requirement is increasing very rapidly day by day. But we know that the

fossile fuel are going to last within a short period of time. As per the survey the present

sources of fossile fuels may lasts upto next 40 years. But the daily demand of energy is

continuously increasing, hence the renewable energy sources can play an important role for

fulfilling our requirement.

Basically India has ruler based economy. But the ruler peoples are still away from

efficient technological energy inputs. They are still using old methods of cooking & water

heating. Hence other foreigners called us as ‘Backward’. But we have a great energy source

available i.e. sun energy. We can efficiently use the solar energy for cooking & water

heating. Because of this a great amount of fuel can be saved and people may get introduced

to new technologies of solar.

Solar energy is only non-exhaustible energy source and its use is clean, safe and

environmentally sound. It has main advantage of no-pollution. Today the world is facing to

a dangerous problem of pollution and which may cause imbalance of nature and may lead to

a huge loss. Hence it is essential to control the pollution. The solar application is the best



solution to this problem as 0% pollution is produced by the solar applications. Hence the

popularization of solar energy is the demand of today.

Government is also working for popularization of solar applications and is providing

40% subsidy on these equipments. Moreover India is a Hot country hence the use of solar

equipment is very effective for this region. Hence the plan must be prepared to have a

countrywide network of solar energy use, and must be actuated in the picture. It is now the

time to plan for society that operates with a frame network for environmental consciousness

as well as social & economical stability.

The solar cooker program in India has been analysed, with special reference to

product development efforts. The program of GEDA to market the existing solar cooker

designs has been studied in detail and it was concluded that the failure of the program was

directly related to the limitations of the product being promoted. Several issues such as

basic R & D needs of cooking at low temperatures, heat transfer processes occurring in the

box type solar cooker, testing and standardization, and applied research for user friendliness

have also been examined.

REFERENCES

1.G. D. RAI.

“ SOLAR ENERGY UTILIZATION’

Text Book

2. N. K. BANSAL , S. B. KESI

“ IREDA NEWS ”

- P. P. 84 – 89 Sept.97

3. H. H. GARG.

“ TREATISE ON SOLAR ENERGY ” Text Book

Vol. 1 P. P. – 50 – 59

4. JUSTIN A. BERENY.

“ SOLAR ENERGY SYSTEM ECONOMICS ”

SURVEY OF THE EMERGING SOLAR ENERGY INDUSTRY

P.P. – 226 – 237



“ DESIGN OF MODIFIED SOLAR WATER HEATER ”

N. C. Proceedings

- P. P. -


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