Solar Cooking · Each solar cooker in sunny, arid climates can save one ton of wood per year....
Transcript of Solar Cooking · Each solar cooker in sunny, arid climates can save one ton of wood per year....
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?