Solar Cooking A Design and Technology project for Key Stage 2

Project Sheet pg. 1

Objectives• To learn about the problems which come with cooking in the developing world and how solar power

can help.• To learn about the basic principles of solar cooking.• To build a solar cooker.

Information notesThebuildingofthesolarcookerscouldtakeuptohalfaday.ThetestingandcookingneedstobedoneonaverysunnydayandwouldbewellsuitedtodemonstrationataschoolfeteorGreenDay.Cookingworksbestinthehoursleadinguptomiddayandimmediatelyafter.

Moreinformation: http://tiny.cc/6qc4r

Solar PowerThere are two types of solar power; • Photovoltaicsolarpower:theenergycreatedbyconvertingsolarpowerintoelectricityusing

photovoltaic solar cells. • Solarthermalenergy,ordirectsolarpower:theenergycreatedbyconvertingsolarenergyintoheat.

Solarcookingdoesnotrequireanyelectricitybutusessolarthermalenergytocookthefood.Thismeansthat you can use a solar oven anywhere that has lots of sun.

Solar CookersSolar cookers are used to cook food and pasteurise water for safe drinking. They use a free, renewable energysourceanddonotpollutetheenvironment.Therearemanybenefitstosolarcooking,explainedlaterinthepack.Theyareparticularlyusefulwhenothersourcesoffuelareunavailable.

Therearedifferenttypesandvariationsofsolarcookersbutthebasicprinciplesofallsolarcookersare:

1. Concentrating sunlight: Amirror,orreflectivemetal,isusedtoreflectthesunlightsothatitisconcentrated and the energy is stronger.

2. Converting light to heat: Parts of the inside of the cooker are painted black. Black surfaces absorb and retain heat which is important for keeping the cooker hot.

3. Trapping heat: Isolatingtheairinsidethecookerfromtheairoutsidethecookermakesanimportantdifference.Aplasticorglasscovercreatesagreenhouseeffectwithintheoventomakesurethattheheat is allowed in but can’t escape out.

Safety!• The contents of solar cookers can get very hot.• Donotputfullysealedjarsorbottlesinsideacookeraspressurewillbuildupinsideit.• Takeextremecarecuttingwithcraftknives.• If working outdoors, remember sun cream, hats and sunglasses.

Project Sheet pg. 2

Why Solar Cooking?

Cooking in the developing world.Morethanhalfoftheworld’spopulationrelyondung,wood,cropwasteorcoaltomeettheirmostbasicenergy needs1.However,accordingtotheUnitedNations,aboutonethirdoftheworld–twobillionpeople–nowsufferfuelwoodshortages,whichmeansitishardertofindandmoreexpensive.Women,andsometimeschildren,mustwalkfurtherdistancestofindfuelforthefamily.Someurbanfamiliesspend 30-50% of their income on cooking fuel or must barter away food for fuel to cook the remainder. Asaresult,familiesdropthenutritiousfoodsthatrequirelengthycooking–suchasvegetables–fromtheirdiet,contributingtomalnutrition.

Solar cookers prevent deforestation. Cookingisthemainsourceofdemandforwoodfuelandcanbeamajorcauseofdeforestation.Deforestationcontributestoclimatechange,floodsandsoilerosion,increasingenvironmentaldegradation,andincreasingpovertyandhunger.

Each solar cooker in sunny, arid climates can save one ton of wood per year. Meanwhile, with solar cookersfamiliesoftenreducefuelwoodneedsbyhalf.

Solar cookers prevent pollution.Burning fuels such as wood and gas pollutes the air and contributes to climate change. Solar cookers provideapollution-freealternative.

Cookingandheatingonopenfiresorstoveswithoutchimneysleadstoindoorairpollution.Everyyear,indoorairpollutionisresponsibleforthedeathof1.6millionpeople2. Because most of the cooking in developingcountriesisdonebywomen,andtheylookafterthechildren,56%ofallindoorairpollution-attributabledeathsoccurinchildrenunderfiveyearsofage.

Solar cookers take longer to cook food but are easy to run.Solarcookingcansavetimeandwork.Mealsinsolarcookerscantakeonetotwohourslongertocookthaninwood-burningcookersbuttheyrequirelessattention.Fooddoesnotneedstirringandthereisnoworryabouttheflamesfromthefire.

Fuelcollectioncanimposeaserioustimeburdenonwomenandchildren.Alleviatingthisworkcanfreewomen’stimeformoreproductiveendeavoursandchildcare,andcanboostchildren’sschoolattendanceandtimeforhomework.

1.,2.WHOFactsheetNo292June2005

Facts• Thereareover100,000solarcookersbeingusedinbothIndiaandChina• Morethan5000familiesinKenyaareusingsolarcookersbecauseofSolarCookersInternational• Developing countries are fuel poor but sun rich • IntheTouloumRefugeeCampinChad,Africa,5,000womenhavebeentrainedtousesolarcookers

andabout16,000havebeendistributed.

VideosVideoofthesolarcookersinTouloum:http://tiny.cc/vmumyw

Making popcorn on a solar cooker http://tiny.cc/aqumyw

Project Sheet pg. 3

Solar Cookers around the world. Although there are some people in the UK who do solar cooking as a hobby, it is rarely used as a method ofcookingbecausetheweatherisunpredictable.Cookingfoodusingsolarenergywilltakeonaveragetwo hours longer than in a normal oven so they need to be used in an area with a near constant supply of sunshine. The food will cook as long as the cooker is in an area with 20 minutes of sunshine per hour. In countries like Kenya or India, where they have more sun, solar cooking is more widely used.

SolarcookingconferenceinDinguyare,Guinea

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Project Sheet pg. 4

Photos

SolarcookingworkshopinStreatham,London,demonstratingarangeofdifferentsolarcookershttp://tiny.cc/grumywhttp://tiny.cc/fsumyw

Project Sheet pg. 5

Teacher Notes: Making a Solar OvenInthefollowingpagesthereareinstructionsfortwosimplesolarovens,onetobemadeusingapizzaboxandoneusingaPringlestube.Thesecookersaresuitableforsimplecooking,suchasmeltingchocolate,reheatingpizzaorbakingsmallcookies,buttheyarenotsuitableforcookingmeals.

ThetestingandcookingneedstobedoneonaverysunnydayandwouldbewellsuitedtodemonstrationataschoolfeteorGreenDay.Cookingworksbestinthehoursleadinguptomiddayandimmediatelyafter.

Thebuildingofthesolarcookerscouldtakeuptohalfadayandwillneedadultsupport,particularlycuttingwithcraftknives.

Formoreadvancedsolarcookers,seethefollowingwebsites.

http://www.solarcooking.org/plans/funnel.htm(Scrolldownforinstructions)

http://tiny.cc/vtumyw

These cookers will need larger materials and will take several sessions to design and build.

Evaluating the solar cookers

Thelastpageofthepackisasimpleevaluationtooltohelpthepupilstoevaluatetheirwork.

Extension

Toextendthisactivityintoascienceactivity,usetwothermometerstomeasurethetemperatureinsideand outside the solar cooker. Pupils can take regular readings and record in tables. These can then be plottedongraphscomparingthetemperatures:

Project Sheet pg. 6

Pizza Box Solar OvenYou will need:• Alargepizzabox• Black paper• Tinfoil or crisp packets • Clingfilmoroven-roastingbags• Newspaper• Stickytapeandwhiteglue

Tools• 30cm ruler• Craftknifeorsharpscissors• Marker pen

Method:1. Onthetopflapofthepizzaboxuseamarkertodrawasquarewithedgesspaced3cmfromthesides

ofthebox.2. Useacraftknifeorsharpscissorstocutaflapinthelidofthepizzabox.Cutalongthreesidesand

scorethefourth.Foldtheflapupgently.3. Covertheundersideoftheflapwithtinfoilorcrisppacketswiththeshinysidefacingupsothatthe

raysfromthesunwillbereflectedoff.Becarefultomakeasfewwrinklesaspossible.Thiswillreflectthesolarradiationintothebox.

4. Opentheboxandlinetheinsidewithblackpaper.Thiswillhelptoabsorbtheheat.5. Cuttwopiecesofclingfilmlargerthanthewindowinthelid,orsticktogetherzip-lockfoodbagsbig

enoughtocoverthewindow.Withthelidopen,tapethefirstpiecetotheundersideofthewindow.Makesureitiscompletelysealedandstretchedtight.

6. Next,closethelidbutkeeptheflapopenandtapethesecondpieceofclingfilmtothewindow,tapingallfoursidesdowntocreateaseal.Thiswillcreateagreenhouseeffectinsidethebox,allowingtheheatinbutnotlettingitout.

7. Finally,rollupsomenewspaperintotubesapproximately2cmthick.Coverallfoursidesoftheoutsideoftheboxandtapethenewspapertothebottomtosecureit.Thiswillinsulateitandhelptostopheat escaping.

4.

Get Cooking!

blackpaper

3.foil

7.

newspaper

6.

cling film

5. cling film

2.

cut here

score and foldhere

1.

Project Sheet pg. 7

How to Test your Solar OvenTakeitoutsidetoasunnyspot(ifthegroundiscold,placeonatowelorblanket).Openthelid,placeapieceofpizzaorcheeseontoastontoapaperplateandputitinthecentreofthebox.Ifyouhaveathermometer,placeitinsidealso,notingdownthetemperatureatthestart.Closethelidandopentheflap,directingtheboxsothefoilflapisfacingthesun.Experimentwiththeangleoftheflapuntilthemostsunlightpossibleisreflectingintothebox.Useastickorrulertoproptheflapupatthecorrectangle.Whilstitiscooking,regularlychecktheangleoftheboxandtheflap,adjustingasneededtomakesureitispointingfullytowardsthesun.Allow30minutesfortheoventopre-heat,thendoubletheusualcookingtime.

Othersolarovenrecipeideas:• Melt marshmallows• Bake simple cookies or fairy cakes• Boilanegg–withoutanywater!

Formoreinformation,watch‘HowtoTurnaPizzaBoxintoaSolarOven’:http://tiny.cc/uuumyw

Your recipe ideas:

Project Sheet pg. 8

Pringles Tube Solar OvenYou will need:• AnemptyPringlestubewiththelidstillon• Clingfilm• A long skewer• Marshmallows• Stickytape

Tools• Craftknife• Ruler

Method:1. Ensure that the inside of the Pringles tube is clean and dry.2. Withacraftknife,cutdownthemiddleofthetubelengthways,leavingabout5cmateitherend.

Then,cutabout5cmeithersideofthelinesateachend,perpendiculartothefirstcut.Thiswillcreatetwoflaps;foldthemout.

3. Coverthenewholethatyouhavecreatedwithclingfilm.Pullthefilmacrosstightlyandtapeitdownto ensure that no air can get in.

4. TakeoffthelidofthePringlescanandpushtheskewerallthewaythroughthemiddleofit,leavingonly enough to hold on to.

5. Place three marshmallows on the skewer and put it inside the Pringles tube, securing the lid shut, so the marshmallows are now inside your solar oven.

6. PlacethePringlestubeoutsidesothatthesunisshiningintotheclingfilmcoveredholeandontothemarshmallows. You may need to turn them halfway through.

7. Thesunwillheatupthesolarovenandyouwillhavegooeymarshmallows!

Forademonstration,watch‘CookingwithPringles:howtomakeasolaroven’:http://tiny.cc/f1umyw

Project Sheet pg. 9

EvaluationHow

successful was your solar cooker?

Why do you think this was?

For the pizza box oven, what angle should the flap be pointing at 11am?

2pm? 4pm?

How can you improve

the design of your cooker?

What else could

be cooked in the Pringles tube

oven?

Which countries are

most suited to using solar cookers?

Why?

What types of solar cooker

are there? What are the advantages and disadvantages of the different designs?

Why is the inside of

the oven painted black?

How is the greenhouse effect

created in a solar cooker?

What is the

purpose of having insulation?