Solar cooker NKS 1 Solar Cookers Update Dr N K Srinivasan Bangalore, India.

Solar cooker NKSSolar cooker NKS 11

Solar Cookers Solar Cookers UpdateUpdateDr N K SrinivasanDr N K SrinivasanBangalore , IndiaBangalore , India


Why use solar cookers?Why use solar cookers?

You save fire wood, charcoal or cooking gasYou save fire wood, charcoal or cooking gas You cook slowly at low heat…retaining many nutrientsYou cook slowly at low heat…retaining many nutrients Food would taste betterFood would taste better Very little capital investment-- inexpensive Very little capital investment-- inexpensive Easy -portableEasy -portable No smoke, no pollution—avoid lung problems due to smokeNo smoke, no pollution—avoid lung problems due to smoke Safe to useSafe to use Enough reasons to try this!Enough reasons to try this! Note that 2 billions of world population[6.5 billion ] use Note that 2 billions of world population[6.5 billion ] use

fire-wood/charcoal /bio-mass only for cooking, especially in thickly fire-wood/charcoal /bio-mass only for cooking, especially in thickly populated countries…populated countries…

think harder and promote solar cookers!!think harder and promote solar cookers!! Solar cookers are easy to make, easy to use.Solar cookers are easy to make, easy to use.


Basic PrinciplesBasic Principles

Two types of designTwo types of design are used for solar cookers are used for solar cookers Box type: an insulated box with glass cover---a kind of mini-glass houseBox type: an insulated box with glass cover---a kind of mini-glass house Mirror type: with flat mirrors to reflect sunlight or parabolic or focusing Mirror type: with flat mirrors to reflect sunlight or parabolic or focusing

(trough-like) mirrors(trough-like) mirrors You can combine these in ingenious ways,called ‘HYBRID DESIGNS’.: You can combine these in ingenious ways,called ‘HYBRID DESIGNS’.:

add flat mirrors to box or in mirror type ,keep the cooking pot in a box.add flat mirrors to box or in mirror type ,keep the cooking pot in a box. One elegant design is the “panel “ type.One elegant design is the “panel “ type. Both have been popular and cost/usage variesBoth have been popular and cost/usage varies You can cook between 9 AM to 3PM in most tropical and semi-You can cook between 9 AM to 3PM in most tropical and semi-

tropical countries for nearly 10 months—leaving the rainy daystropical countries for nearly 10 months—leaving the rainy days For quick reference:For quick reference: See Beth Halacy & Dan Halacy “Cooking with the Sun”, also D See Beth Halacy & Dan Halacy “Cooking with the Sun”, also D

S Halacy: “Fun with the sun” (1959)S Halacy: “Fun with the sun” (1959)


Direct and diffuse sun Direct and diffuse sun lightlight

Sunlight comes to us in two forms:Sunlight comes to us in two forms: Direct light that casts sharp shadowsDirect light that casts sharp shadows Diffuse light ,mainly scattered by clouds and Diffuse light ,mainly scattered by clouds and

the sky…or reflected by nearby wallsthe sky…or reflected by nearby walls Box type cookers absorb bothBox type cookers absorb both Mirror type cookers use only direct lightMirror type cookers use only direct light Box type would gather some energy even on Box type would gather some energy even on

cloudy days!cloudy days! Box cookers gather energy even with passing Box cookers gather energy even with passing

clouds and retain heat longer, after sun set.clouds and retain heat longer, after sun set.


Box type cookersBox type cookers

Make a wooden/plastic/metal/cardboard boxMake a wooden/plastic/metal/cardboard box Paint inside with black paint to absorb sun light energy—keep a metal tray Paint inside with black paint to absorb sun light energy—keep a metal tray

painted black-use poster paintpainted black-use poster paint Have a cover glass/plastic to insulate—the hot pot gives out infra-red rays Have a cover glass/plastic to insulate—the hot pot gives out infra-red rays

which cannot pass through the glass ….thus trapping heat…which cannot pass through the glass ….thus trapping heat… Keep insulator [coir, peanut shells, newspaper, insulating tiles ] below Keep insulator [coir, peanut shells, newspaper, insulating tiles ] below

tray and box and at the sides of the box.tray and box and at the sides of the box. Simple –right!Simple –right! You can keep a flat mirror hinged on the cover---to throw additional light You can keep a flat mirror hinged on the cover---to throw additional light

into the boxinto the box It can be slow cooking –1 to 3 hoursIt can be slow cooking –1 to 3 hours Barbara Kerr made an oven on the Kitchen wall, used from inside the Barbara Kerr made an oven on the Kitchen wall, used from inside the

kitchen!!!kitchen!!!


Mirror type cookerMirror type cooker

You can use a curve sheet of polished aluminum or stainless steel You can use a curve sheet of polished aluminum or stainless steel or aluminum foilor aluminum foil

The solar energy is focused on the cooking pot kept in a frame…The solar energy is focused on the cooking pot kept in a frame…blacken the outside of the potblacken the outside of the pot

Simple---yes but one additional work …You have to keep turning Simple---yes but one additional work …You have to keep turning the mirror and tilting to focus the lightthe mirror and tilting to focus the light

You have to keep standing near the cooker…You have to keep standing near the cooker… You can also keep an automatic tracker, but that will cost more.You can also keep an automatic tracker, but that will cost more. Cooking is done fast with mirror type cooker, typically in one hourCooking is done fast with mirror type cooker, typically in one hour Be carerful..dont look at the focal spot..You can hurt your eyes…Be carerful..dont look at the focal spot..You can hurt your eyes…

wear sun-glasses wear sun-glasses


Various types of mirror-cookersVarious types of mirror-cookers

Now we consider different types of cookersNow we consider different types of cookers Sun-basket was made in the early70’s---use paper-Sun-basket was made in the early70’s---use paper-

mache shell like a parabolic mirror like a basket and mache shell like a parabolic mirror like a basket and stick small flat mirror on the inside surface as reflectorstick small flat mirror on the inside surface as reflector

Keep a metallic curved sheet like a cylindrical mirror Keep a metallic curved sheet like a cylindrical mirror

and keepand keep the cooking pot in the focusing area.the cooking pot in the focusing area. You can use a simpleYou can use a simple Umbrella too.Umbrella too.


Umbrella CookersUmbrella Cookers Many solar designers have built simple,cheap Many solar designers have built simple,cheap

near-parabolic cookers using umbrellas.near-parabolic cookers using umbrellas. Paste the inner cloth of umbrella with aluminum foil Paste the inner cloth of umbrella with aluminum foil

or mylar coated with aluminum sheetsor mylar coated with aluminum sheets Fix a grate like plate to keep the pot at the focusFix a grate like plate to keep the pot at the focus Keep it in the sun—what could be simpler than Keep it in the sun—what could be simpler than

this?this? Umbrella cooker is just fun on the beach---while Umbrella cooker is just fun on the beach---while

you tan,the umbrella gives cooked food!you tan,the umbrella gives cooked food!


Energy balanceEnergy balance

How much solar energy you can collect in these cookers?How much solar energy you can collect in these cookers? You collect more energy with more area covered by the glass cover or mirrors.You collect more energy with more area covered by the glass cover or mirrors. What is the amount of energy per square meter?What is the amount of energy per square meter? Solar energy is typically 200 watts/square meter, though it could vary Solar energy is typically 200 watts/square meter, though it could vary

from100W/sqm to 900 W/sqmfrom100W/sqm to 900 W/sqm [This will vary with your location, cloud cover, dust/smoke in the air…It would be [This will vary with your location, cloud cover, dust/smoke in the air…It would be

zero at night! Or very cloudy day!zero at night! Or very cloudy day! In practice take the energy received as 150 watts per square meter.In practice take the energy received as 150 watts per square meter. Suppose you use 1 sq.meter area…You get energy of 150 watt-hour in one hour. Suppose you use 1 sq.meter area…You get energy of 150 watt-hour in one hour.

or 0.15 KWH or 0.15 unitor 0.15 KWH or 0.15 unit You may need 1 to 3 hours to cook your meal!--be patient—depends on the food You may need 1 to 3 hours to cook your meal!--be patient—depends on the food

stuff, quantity and of course, the solar flux.stuff, quantity and of course, the solar flux. Temperatures reached in solar cookers: 80 to 120 degrees C .It could be as high Temperatures reached in solar cookers: 80 to 120 degrees C .It could be as high

as 170 deg C .IF IT REACHES 120 deg C[250F] it is a good design.as 170 deg C .IF IT REACHES 120 deg C[250F] it is a good design. Most cooking is done between 80 and 110 deg CMost cooking is done between 80 and 110 deg C Thermal efficiency of cookers---40 to 60% For baking and frying, you will need Thermal efficiency of cookers---40 to 60% For baking and frying, you will need

higher temperatures.higher temperatures. Effective insulation & absorption by blackened surface inside,enables higher tempEffective insulation & absorption by blackened surface inside,enables higher temp


What is the ‘Oven temperature’ What is the ‘Oven temperature’ ??

What do we measure as the oven temperature?What do we measure as the oven temperature? If the oven thermometer is kept in the oven space, it If the oven thermometer is kept in the oven space, it

measures the temperature of the measures the temperature of the air air in the ovenin the oven You can measure the temperature inside the cooking You can measure the temperature inside the cooking

pot by drilling a hole on the lid and inserting the pot by drilling a hole on the lid and inserting the themometerthemometer

Or else, measure the outside temp of the cooking pot Or else, measure the outside temp of the cooking pot or the metallic tray kept at the bottom by contact or the metallic tray kept at the bottom by contact thermometer ,say ,using a thermo-couplethermometer ,say ,using a thermo-couple

The cooking pot lid always shows higher temp ,due to The cooking pot lid always shows higher temp ,due to direct heating from sun’s rays.direct heating from sun’s rays.


Box vs Concentrator Box vs Concentrator CookersCookers

BOXBOX Easy to make and costs lessEasy to make and costs less Slower cooking –takes 2 to 3 hoursSlower cooking –takes 2 to 3 hours Requires no attention—leave the pots Requires no attention—leave the pots

inside cooker and attend to other workinside cooker and attend to other work Safe and easy to useSafe and easy to use

Bulky and heavy to carry;use caster Bulky and heavy to carry;use caster wheelswheels

Uses both direct and diffuse or Uses both direct and diffuse or scattered light from the sun; can scattered light from the sun; can operate on cloudy days or with operate on cloudy days or with passing cloudspassing clouds

Can be modified as a food Can be modified as a food dryer ,water pasteurizer,nut roaster dryer ,water pasteurizer,nut roaster and so onand so on

Easy to maintain, repairEasy to maintain, repair Box cookers can reach 120 to 150 Box cookers can reach 120 to 150

deg Cdeg C

CONCENTRATORCONCENTRATOR Needs tools and higher skills ,cost lot Needs tools and higher skills ,cost lot

moremore Faster cooking—30mins to one hourFaster cooking—30mins to one hour Needs attention and often Needs attention and often

adjustments or tracking the sunadjustments or tracking the sun Protect your eyes; bright spot can Protect your eyes; bright spot can

irritate eyes or cause blindnessirritate eyes or cause blindness Can be lightCan be light Uses only direct light; useless on Uses only direct light; useless on

cloudy dayscloudy days

Cannot be modified for food drying Cannot be modified for food drying and other usesand other uses

Difficult to maintain; needs care of Difficult to maintain; needs care of reflecting surfacereflecting surface

Can reach much higher temp,140 Can reach much higher temp,140 deg C and above.deg C and above.


Time to Cook in Box cookersTime to Cook in Box cookers

Easy to cook--Easy to cook--Rice,egg,fruit,vegetables, Rice,egg,fruit,vegetables, chicken,fish—1 to 2 hourschicken,fish—1 to 2 hours

ModerateModerate--Root --Root vegetables,potatoes, vegetables,potatoes, beans,lentils,dhal,most beans,lentils,dhal,most meat,bread—3 to 4 hoursmeat,bread—3 to 4 hours

HardHard---Soup,dried ---Soup,dried beans,large meat—5 to 8 beans,large meat—5 to 8 hours hours

Cooking is mostly Cooking is mostly done in the range 80 done in the range 80 to 120 deg Cto 120 deg C

‘‘minimum’ solar cookerminimum’ solar cooker


Simple cookers for developing Simple cookers for developing countriescountries

There is a great need for solar cookers in There is a great need for solar cookers in hot ,underdeveloped or developing nations of hot ,underdeveloped or developing nations of the world, mainly to save fire wood and also to the world, mainly to save fire wood and also to save time spent in gathering fire wood.. to save time spent in gathering fire wood.. to reduce deforestationreduce deforestation

Think about the rural folk in very poor nationsThink about the rural folk in very poor nations Also places like refugee campsAlso places like refugee camps In Gaza strip, one inventor has built a solar oven with In Gaza strip, one inventor has built a solar oven with

bricks, mud plaster and two glass windows. bricks, mud plaster and two glass windows.


New designs at low costNew designs at low cost

Several cookers have emerged ---tried in various Several cookers have emerged ---tried in various countries and readily availablecountries and readily available

Use cardboard panels, with aluminum foil glued to Use cardboard panels, with aluminum foil glued to themthem

Shape several panels –stick them together ---to form Shape several panels –stick them together ---to form roughly a focusing basket.roughly a focusing basket.

Keep a black cooking pot ,enclosed in a plastic bag!Keep a black cooking pot ,enclosed in a plastic bag! That is it! You have a simple solar cooker for the That is it! You have a simple solar cooker for the

masses---in underdeveloped countries.masses---in underdeveloped countries. This simple design –Panel type-is due to Roger This simple design –Panel type-is due to Roger

Bernard of Univ of Lyons,France.Bernard of Univ of Lyons,France. These panel type cookers have been widely used due These panel type cookers have been widely used due

to the efforts of SCIto the efforts of SCI


CooKitCooKit Here is a simple kit with cardboard panels made out of Here is a simple kit with cardboard panels made out of

cardboard sheet [3feetx4feet]cardboard sheet [3feetx4feet] Aluminum foil [‘Reynolds’ Kitchen foil] is pasted on this Aluminum foil [‘Reynolds’ Kitchen foil] is pasted on this

to form reflectorsto form reflectors A black pot is wrapped in a plastic bag and kept on the A black pot is wrapped in a plastic bag and kept on the

cooker.cooker. Simple and elegant ---the CooKit is widely used in Simple and elegant ---the CooKit is widely used in

many countries due to the efforts of Solar Cooking many countries due to the efforts of Solar Cooking International [SCI]—including in refugee camps in International [SCI]—including in refugee camps in Africa.See their website: Africa.See their website: www.solarcookerwww.solarcooker .org .org

May be, you can build your own similar cooker to suit May be, you can build your own similar cooker to suit your needs.your needs.


Low cost DIY- Solar Box CookerLow cost DIY- Solar Box Cooker

Two cardboard boxes, one inner and the other outer ,can be usedTwo cardboard boxes, one inner and the other outer ,can be used Insulate the space between the boxes with dry insulators like dried Insulate the space between the boxes with dry insulators like dried

peanut shell, newspaper , coir [coconut fibre] ….peanut shell, newspaper , coir [coconut fibre] …. Cover with glass or plastic sheetCover with glass or plastic sheet Use cardboard +aluminum foil pasted panel as reflector..some Use cardboard +aluminum foil pasted panel as reflector..some

use lithogaph aluminum printing sheet…use lithogaph aluminum printing sheet… Keep a matt-black steel plate as absorber at the bottom---this is Keep a matt-black steel plate as absorber at the bottom---this is

important to absorb all the heat and transfer it to the potsimportant to absorb all the heat and transfer it to the pots Use a black cooking pot--use poster paint to color blackUse a black cooking pot--use poster paint to color black You can use glass jars for cooking-paint outside with black paint…You can use glass jars for cooking-paint outside with black paint…

also for drying grains/fruits/veggiesalso for drying grains/fruits/veggies Barbara Kerr is the pioneer in these cardboard box cookersBarbara Kerr is the pioneer in these cardboard box cookers Box solar cookers are more widely used than mirror type --- easy Box solar cookers are more widely used than mirror type --- easy

to make and use !to make and use !


Four reflectors--- slant faced Solar Four reflectors--- slant faced Solar OvenOven

One of the efficient box cooker design is to add four flat reflectors on four One of the efficient box cooker design is to add four flat reflectors on four sides of the window..this becomes an oven!sides of the window..this becomes an oven!

The window is slanted to face the sun [towards south for northern The window is slanted to face the sun [towards south for northern hemisphere]hemisphere]

Or you tilt the oven Or you tilt the oven This design due to Maria Telkes [formerly a Prof at MIT] had been most This design due to Maria Telkes [formerly a Prof at MIT] had been most

efficient and popularefficient and popular Several variations have been made---three reflectors, horizontal Several variations have been made---three reflectors, horizontal

tray/cradle inside and others.tray/cradle inside and others. Keep a cradle inside to position the tray level.Keep a cradle inside to position the tray level. If heavy, fit wheels or castors to move If heavy, fit wheels or castors to move Big ones have been made for village/community level cooking.Big ones have been made for village/community level cooking.


DIY-Home made solar cookersDIY-Home made solar cookers

Excellent designs are available for making your Excellent designs are available for making your own cookersown cookers

Cardboard,aluminum foil,trays,transparent Cardboard,aluminum foil,trays,transparent plastic glazing—these are required for your plastic glazing—these are required for your cookercooker

A detailed video presentation: A detailed video presentation: www.williamgbecker.com/makesolaroven.htmlwww.williamgbecker.com/makesolaroven.html

A few technical pointers are given in the next A few technical pointers are given in the next slideslide


Technical points for Box cookersTechnical points for Box cookers Use simple insulation material—crumpled newspaper is okay—but you need 25 to 50 Use simple insulation material—crumpled newspaper is okay—but you need 25 to 50

mm thickness for effective heat trapmm thickness for effective heat trap Much heat loss occurs thru glass cover and the sidesMuch heat loss occurs thru glass cover and the sides A shallow tray with less depth is better than a box with great depth in your box—this A shallow tray with less depth is better than a box with great depth in your box—this

reduces side wall area.reduces side wall area. Use aluminum or steel tray—Al tray may have less mass but has greater specific Use aluminum or steel tray—Al tray may have less mass but has greater specific

heat…so both are Okayheat…so both are Okay Good sealing is required to avoid leak of hot air.Good sealing is required to avoid leak of hot air. Tilting the box or slant face is needed for latitude greater than 15 deg---that is Tilting the box or slant face is needed for latitude greater than 15 deg---that is

subtropical…subtropical… For a family of three or four persons, you need a box cooker of at least 4 square feet For a family of three or four persons, you need a box cooker of at least 4 square feet

collector area.collector area. Box cookers collect both direct and diffuse solar rays and therefore better for cloudy Box cookers collect both direct and diffuse solar rays and therefore better for cloudy

skies.skies. Preheat box cookers by keeping in the sun from 9AM before placing the pots.Preheat box cookers by keeping in the sun from 9AM before placing the pots. You can use Al foil to keep in the air gap to improve the insulation.You can use Al foil to keep in the air gap to improve the insulation.Test the cooker with actual cooking conditions with food stuff weighed, noting time and Test the cooker with actual cooking conditions with food stuff weighed, noting time and

temperature.temperature.For very hot regions,reflectors may not be needed.For very hot regions,reflectors may not be needed.Keep your cooker protected from the wind,adjacent to a wall or cover.Keep your cooker protected from the wind,adjacent to a wall or cover.


Minimal insulation box cookersMinimal insulation box cookers

Standard cookers ,including commercial ones have 1 to 2 inches of insuation---Standard cookers ,including commercial ones have 1 to 2 inches of insuation---glass fibre,wool,foam material,crumpled newspaper and so on.glass fibre,wool,foam material,crumpled newspaper and so on.

Some pundits use only thin insualtion,about 1 in ,with aluminum foil,cardboard Some pundits use only thin insualtion,about 1 in ,with aluminum foil,cardboard barriers,dividers to reduce the convection in air space…after all air itself isa good barriers,dividers to reduce the convection in air space…after all air itself isa good insulator and small pockets of air spaces help…Al foil reflect the heat back into the insulator and small pockets of air spaces help…Al foil reflect the heat back into the inner box…[called ‘reflective barriers’]inner box…[called ‘reflective barriers’]

It is possible to have thin insulation with aluminum foil and cardboard pieces for It is possible to have thin insulation with aluminum foil and cardboard pieces for cookers operating in very bright sun light, most probably in tropical regions.cookers operating in very bright sun light, most probably in tropical regions.

Thin insulation reduces the weight and size of the box cookers---an advantage for Thin insulation reduces the weight and size of the box cookers---an advantage for senior citizens and balcony userssenior citizens and balcony users

I would prefer thick insulation about 2 inches—for using even less bright days and I would prefer thick insulation about 2 inches—for using even less bright days and for quick heating and slow cooling.for quick heating and slow cooling.

Note that radiation is less important mode of heat loss ,compared to convection or Note that radiation is less important mode of heat loss ,compared to convection or conduction losses in box cookers,because of low temperatures….Amount of heat conduction losses in box cookers,because of low temperatures….Amount of heat by radiation goes by T^4, where T is the temperature in Kelvin…For low temp,this by radiation goes by T^4, where T is the temperature in Kelvin…For low temp,this factor would be less.[Stefan-Boltzmann law]factor would be less.[Stefan-Boltzmann law]

Note ,however, the radiation loss is almost double for a cooking pot at 100 Note ,however, the radiation loss is almost double for a cooking pot at 100 degC,compared to the same pot at 50deg C…therefore radiation losses affect the degC,compared to the same pot at 50deg C…therefore radiation losses affect the max temp attained.max temp attained.


My “Box-pan” hybrid cookerMy “Box-pan” hybrid cooker

Box cookers are simple to make, easy to us---,hence popular.Box cookers are simple to make, easy to us---,hence popular. Panel cookers throw more energy,faster to cook but needs orientationPanel cookers throw more energy,faster to cook but needs orientation Box cookers are bulky and often heavy; panels are light weight, foldable..Box cookers are bulky and often heavy; panels are light weight, foldable.. I made hybrid called “Box-Pan “ cooker, easy to use,light weight and smallI made hybrid called “Box-Pan “ cooker, easy to use,light weight and small Use a box,with slant face,keep back reflector.Use a box,with slant face,keep back reflector. The box is not glazed as a whole…The box is not glazed as a whole… Keep a large metal tray, blackened at the bottom.Keep a large metal tray, blackened at the bottom. The bottom insulation below the tray is a wad of newspaper.The bottom insulation below the tray is a wad of newspaper. Cover this tray with oven bag or plastic coverCover this tray with oven bag or plastic cover Keep blackened pots inside the bag…Keep blackened pots inside the bag… Orient the box as you do for box cookers!Orient the box as you do for box cookers! You have a simple, light weight box cooker with quick heating of panel cookers…!You have a simple, light weight box cooker with quick heating of panel cookers…! Try this and you will love itTry this and you will love it…”Box-pan…”Box-pan” will be your constant companion.!!” will be your constant companion.!! Give me your feedback on “BOX_PAN” please!!Give me your feedback on “BOX_PAN” please!!


Other uses for Solar Box CookersOther uses for Solar Box Cookers

Pasteurize water---heat to 65deg C and coolPasteurize water---heat to 65deg C and cool Roast nuts and seeds—I use regularly to roast Roast nuts and seeds—I use regularly to roast

peanuts !peanuts ! Make pickles in glass jars kept in the boxMake pickles in glass jars kept in the box Toast bread to the degree of browning Toast bread to the degree of browning Dry fruits/veggies by keeping the lid partially Dry fruits/veggies by keeping the lid partially

open or providing vents at the sidesopen or providing vents at the sides Making candies with nuts addedMaking candies with nuts added


Solar Cooking HistorySolar Cooking History Early pioneers: Horace de Saussure cooked fruits in 1767Early pioneers: Horace de Saussure cooked fruits in 1767 John Herschel and Langley (USA) cooked food with box type cookerJohn Herschel and Langley (USA) cooked food with box type cooker Mouchot did cooking with concentrating mirrors & wrote a bookMouchot did cooking with concentrating mirrors & wrote a book Charles Abbot of Smithsonian Inst made a concentrating cooker with mirror Charles Abbot of Smithsonian Inst made a concentrating cooker with mirror

heating oil and cooking later in the evenings.heating oil and cooking later in the evenings. M K Ghosh, an Indian, made a box cooker in 1945M K Ghosh, an Indian, made a box cooker in 1945 Maria Telkes made cookers of different designs using four mirrors attached to a Maria Telkes made cookers of different designs using four mirrors attached to a

box type oven at MIT[1950’s]box type oven at MIT[1950’s] Renewed interests after 1980Renewed interests after 1980 Barbara Kerr developed a simple low cost box-type cookerBarbara Kerr developed a simple low cost box-type cooker Robert Metcalf developed Robert Metcalf developed water pasteurizationwater pasteurization using a solar cooker using a solar cooker 1987 marked the founding of Solar Cooker International [SCI] by Kerr-Cole-1987 marked the founding of Solar Cooker International [SCI] by Kerr-Cole-

Metcalf team in Sacramento, California Metcalf team in Sacramento, California Univ of Chile popularized solar cookers in a village in ChileUniv of Chile popularized solar cookers in a village in Chile In 1990, SCI developed the CooKit from the earlier design of Roger Barnard of In 1990, SCI developed the CooKit from the earlier design of Roger Barnard of

France.France. CooKit has been used by more than 30000 refugees in Africa & CooKit has been used by more than 30000 refugees in Africa & elsewhere .elsewhere . Since 2005, commercial solar cooker sales has gone up 5 times….Since 2005, commercial solar cooker sales has gone up 5 times….


Countries using Solar Countries using Solar cookingcooking

African nationsAfrican nations ChinaChina IndiaIndia Sri LankaSri Lanka NepalNepal Chile/Peru/Mexico…..Chile/Peru/Mexico….. Israel/PalestineIsrael/Palestine & others& others


Home-made vs commercial Home-made vs commercial cookerscookers

Home –madeHome –made Easy to makeEasy to make Very low costVery low cost Lot of funLot of fun Learn basic principles of Learn basic principles of

energy devices and teach to energy devices and teach to others…you learn energy others…you learn energy sciencescience

Use local materials and skillsUse local materials and skills Can change design and adopt Can change design and adopt

to local requirementsto local requirements Can start your own small Can start your own small

business!business!

CommercialCommercial Expensive [$100 to $300]Expensive [$100 to $300] Built to last [some say 20 Built to last [some say 20

years]years] More efficient/Easy to use More efficient/Easy to use Standard Standard

designs/Performance designs/Performance specifiedspecified

No learning experienceNo learning experience Mass produced in thousandsMass produced in thousands Can be locally manufactured Can be locally manufactured

in a small unit/generates in a small unit/generates employmentemployment


Some commercial Box cookersSome commercial Box cookers

Global Sun Oven---with four large reflectors, largest selling onesGlobal Sun Oven---with four large reflectors, largest selling ones—14inx14in area…—14inx14in area…

Sport-SOS---light weight,with or without reflectors,large cooking Sport-SOS---light weight,with or without reflectors,large cooking area, developed by Solar Oven Society as non-profit venture, area, developed by Solar Oven Society as non-profit venture, acrylic glazingacrylic glazing

Hot Pot-with several reflectors--single ,cooking pot kept in a glass Hot Pot-with several reflectors--single ,cooking pot kept in a glass bowl—developed and tested by Florida Solar energy bowl—developed and tested by Florida Solar energy center…,made in Mexico,less expensivecenter…,made in Mexico,less expensive

Sun Stove --used in south Africa, India and elsewhere—low cost, Sun Stove --used in south Africa, India and elsewhere—low cost, uses litho printing plates ,no reflectorsuses litho printing plates ,no reflectors

See the websites for details ,comparison and pricingSee the websites for details ,comparison and pricing Tulsi solar oven—original Indian design—hybrid ,that is ,has Tulsi solar oven—original Indian design—hybrid ,that is ,has

electrical heating too, comes like a small suitcase.electrical heating too, comes like a small suitcase.


My home-made box cookerMy home-made box cooker

This is small---12in x 10 in glass cover from picture frame,two cardboard This is small---12in x 10 in glass cover from picture frame,two cardboard boxes…boxes…

Outside insulation with styrofoam[thermocole],inner insulation with Outside insulation with styrofoam[thermocole],inner insulation with crumpled paper &al foilcrumpled paper &al foil

Reflectors—cardboard pasted with Al foilReflectors—cardboard pasted with Al foil No tilting No tilting Inside box—lined with Al foil.The bottom with a black enamelled steel trayInside box—lined with Al foil.The bottom with a black enamelled steel tray Important—check for air leaks and seal them.Important—check for air leaks and seal them. Reaches 110 deg C in 30 mins in Bangalore,India in a cloudless dayReaches 110 deg C in 30 mins in Bangalore,India in a cloudless day Can cook with one or two pots, filled with 250 gms of food stuff…Can cook with one or two pots, filled with 250 gms of food stuff… Weight—about 3 Kg onlyWeight—about 3 Kg only Used for roasting peanuts and toasting bread almost daily.Used for roasting peanuts and toasting bread almost daily. Can be placed in a balcony for urban peopleCan be placed in a balcony for urban people Also made a larger one 16inx13in –similar designAlso made a larger one 16inx13in –similar design


General RemarksGeneral Remarks

Solar cookers have not been very popular among the rural people Solar cookers have not been very popular among the rural people of even developing countries—they are too expensive for them, of even developing countries—they are too expensive for them, often inconvenient to use.often inconvenient to use.

In India very small percentage of rural people use these cookersIn India very small percentage of rural people use these cookers—total about 0.6 million cookers.—total about 0.6 million cookers.

Most people do not see the environmental connection of firewood Most people do not see the environmental connection of firewood burning, losing trees and carbon pollution.burning, losing trees and carbon pollution.

Low cost card-board made cookers with aluminum foil and panel Low cost card-board made cookers with aluminum foil and panel cookers like CooKit may change the scenariocookers like CooKit may change the scenario

With card-board made cookers, solar cookers could become very With card-board made cookers, solar cookers could become very popular among the rural people of several countries.—that is the popular among the rural people of several countries.—that is the hope!hope!

There is tremendous interest in solar cookers now---to reduce There is tremendous interest in solar cookers now---to reduce carbon emissions and many African nations are serious about carbon emissions and many African nations are serious about this.this.


Contact & some Contact & some referencesreferences Dr Srinivasan Nenmeli KDr Srinivasan Nenmeli K

[email protected]@hotmail.com www.solardevicesforthirdworld.webs.comwww.solardevicesforthirdworld.webs.com Kerr-Cole Solar Box CookersKerr-Cole Solar Box Cookers

Po Box 576,Taylor,Az 85939 ,USAPo Box 576,Taylor,Az 85939 ,USA

WWW.solarcookers.orgWWW.solarcookers.org Ref: The Expanding world of Solar Box cooker—Barbara Ref: The Expanding world of Solar Box cooker—Barbara

Kerr, 1991Kerr, 1991 www.backwoodshome.comwww.backwoodshome.com [see Joe Radabaugh’s solar [see Joe Radabaugh’s solar

cooker design]cooker design] www.solarcookeratcatinawest.comwww.solarcookeratcatinawest.com Read “Solar Cooking review ‘ from SCI---available online. Read “Solar Cooking review ‘ from SCI---available online.

Solar cooker NKS 1 Solar Cookers Update Dr N K Srinivasan Bangalore, India.

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