Classroom slow cooker

1. The ProblemThe Problem
• Half the world’s people must burn wood or dried dungHalf the world’s people must burn wood or dried dung
to cook their food.to cook their food.
• Nearly 1.2 billion people, a fifth of the world’sNearly 1.2 billion people, a fifth of the world’s
population, do not have access to clean drinking water.population, do not have access to clean drinking water.
• Over 1 million children die yearly because of un-boiledOver 1 million children die yearly because of un-boiled
drinking water.drinking water.
• Wood cut for cooking purposes contributes to the 16Wood cut for cooking purposes contributes to the 16
million hectares of forest destroyed annually.million hectares of forest destroyed annually.
• Half the world’s population is exposed to indoor airHalf the world’s population is exposed to indoor air
pollution, mainly the result of burning solid fuels forpollution, mainly the result of burning solid fuels for
cooking and heating.cooking and heating.

2. OverviewOverview
• Types of cookersTypes of cookers
• Principles of solar cooker designPrinciples of solar cooker design
• Retained heat cookingRetained heat cooking
• Cooking guidelinesCooking guidelines
• Teaching ideasTeaching ideas
• ExamplesExamples
• Additional information and resourcesAdditional information and resources

3. Types of solar ovensTypes of solar ovens
• Box CookerBox Cooker
• Panel CookerPanel Cooker
• Solar Funnel CookerSolar Funnel Cooker
• Parabolic CookerParabolic Cooker - not recommended- not recommended

4. Box cookerBox cooker
• Among easiest and most popular to build and useAmong easiest and most popular to build and use
• Lid of a cardboard box reflects light onto pots under glassLid of a cardboard box reflects light onto pots under glass
• Advantage of slow, even cooking of large quantities ofAdvantage of slow, even cooking of large quantities of
foodfood

5. Panel CookerPanel Cooker
• Sunlight is reflected off of multiple panels onto a potSunlight is reflected off of multiple panels onto a pot
under a glass lid or in a bagunder a glass lid or in a bag
• Can be built quickly and at low costCan be built quickly and at low cost
• Many different varietiesMany different varieties

6. Solar Funnel CookerSolar Funnel Cooker
• Safe, inexpensive and easy to useSafe, inexpensive and easy to use
• Concentrates sunlight into a dark pot in a plastic bagConcentrates sunlight into a dark pot in a plastic bag
• Combines best of parabolic and box cookersCombines best of parabolic and box cookers
• Anyone can make oneAnyone can make one

7. Parabolic CookerParabolic Cooker
• Highly focused light and high temperaturesHighly focused light and high temperatures
• Cooks nearly as fast as a conventional ovenCooks nearly as fast as a conventional oven
• Costly and complicated to make and use – have to turnCostly and complicated to make and use – have to turn
frequently to follow the sunfrequently to follow the sun
• Potentially hazardous-not recommendedPotentially hazardous-not recommended

8. The basic principles - C.A.R.E.S.The basic principles - C.A.R.E.S.
• CCollect the lightollect the light
• AAbsorb the lightbsorb the light
• RRetain the heatetain the heat
• EEase and Efficiencyase and Efficiency
• SSafetyafety

9. C: Collect the LightC: Collect the Light
• Collect the sunlight using reflectors with anCollect the sunlight using reflectors with an
approximately 400 square inch opening (20x20)approximately 400 square inch opening (20x20)
• Easy way to measure: the minimum opening ofEasy way to measure: the minimum opening of
the cooker needs to be the diameter of an adult’sthe cooker needs to be the diameter of an adult’s
armarm
• Reflective surface materials include: aluminum,Reflective surface materials include: aluminum,
Mylar, aluminized Mylar of any thickness,Mylar, aluminized Mylar of any thickness,
aluminum or chromium paint (Note: mirror likealuminum or chromium paint (Note: mirror like
reflectors can lead to eye damage)reflectors can lead to eye damage)

10. A: Absorb the lightA: Absorb the light
• Absorb the light – paint the pot matte black orAbsorb the light – paint the pot matte black or
another dark color to absorb the heatanother dark color to absorb the heat
• Pots can also be elevated by a wire base or posts,Pots can also be elevated by a wire base or posts,
allowing the bottom of the pots to collectallowing the bottom of the pots to collect
sunlightsunlight

11. R: Retain the HeatR: Retain the Heat
• Retain the heat – hot vessels lose their heat toRetain the heat – hot vessels lose their heat to
the air quickly so they need to be coveredthe air quickly so they need to be covered
• Cover with plastic, glass, Plexiglas, or temperedCover with plastic, glass, Plexiglas, or tempered
glassglass
• A tight lid will trap steam and speed up cookingA tight lid will trap steam and speed up cooking
Ex: Canning jars work like inexpensive pressureEx: Canning jars work like inexpensive pressure
cookerscookers

12. E: Ease and EfficiencyE: Ease and Efficiency
EaseEase – simplicity of everyday use– simplicity of everyday use
• Funnel and box cookers are the easiest to use – theyFunnel and box cookers are the easiest to use – they
don’t have to be turned to follow the sundon’t have to be turned to follow the sun
EfficiencyEfficiency - how fast the cooker heats food- how fast the cooker heats food
• Parabolic cookers focus light to a point (most efficient)Parabolic cookers focus light to a point (most efficient)
causing dangerous conditionscausing dangerous conditions
• Funnel cookers focus light across a broader area downFunnel cookers focus light across a broader area down
the center of the cooker (efficient but not dangerous)the center of the cooker (efficient but not dangerous)

13. S: SafetyS: Safety
• SSafety – Avoid highly focused light such as thatafety – Avoid highly focused light such as that
in the parabolic cooker. It can damage eyes andin the parabolic cooker. It can damage eyes and
start firesstart fires
• Always exercise caution with cookers. SunglassesAlways exercise caution with cookers. Sunglasses
are useful when looking into a cookerare useful when looking into a cooker
• Cooking pots are hot and should be treated asCooking pots are hot and should be treated as
though they were on a stove-topthough they were on a stove-top

14. Remember - C.A.R.E.S.Remember - C.A.R.E.S.
• CCollect the lightollect the light
• AAbsorb the lightbsorb the light
• RRetain the heatetain the heat
• EEase and Efficiencyase and Efficiency
• SSafetyafety

15. Retained Heat CookingRetained Heat Cooking
• If sunlight is lost or multiple items need to beIf sunlight is lost or multiple items need to be
cooked, there is a solutioncooked, there is a solution
• Once the food is heated, quickly transfer toOnce the food is heated, quickly transfer to
either:either:
- an insulated box or set of towels,- an insulated box or set of towels,
- or an insulated hole in the ground covered- or an insulated hole in the ground covered
with more insulationwith more insulation
• The food will continue to cook for hoursThe food will continue to cook for hours

16. TemperaturesTemperatures
• Sunny Day: heats from 130-145°C (265-300°F)Sunny Day: heats from 130-145°C (265-300°F)
• Cloudy Day: heats from 95-105°C (200-220°F)Cloudy Day: heats from 95-105°C (200-220°F)
• Hot enough to pasteurize water (at least 65-70°CHot enough to pasteurize water (at least 65-70°C
for 20 minutes)for 20 minutes)
• Hot enough to fully cook meats, breads, grains,Hot enough to fully cook meats, breads, grains,
vegetables, etc.vegetables, etc.
• Kills disease-causing bacteriaKills disease-causing bacteria

17. BE CREATIVE andBE CREATIVE and
HAVE FUN!HAVE FUN!
• You can improvise with most of the techniquesYou can improvise with most of the techniques
and materialsand materials
• Remember the basic principles (CARES) andRemember the basic principles (CARES) and
you can adjust for the skills and resources ofyou can adjust for the skills and resources of
those who will make and use the ovensthose who will make and use the ovens

18. ExamplesExamples

19. ExamplesExamples

20. ExamplesExamples