The Problem
• Half the world’s people must burn wood or dried dung
to cook their food.
• Nearly 1.2 billion people, a fifth of the world’s
population, do not have access to clean drinking water.
• Over 1 million children die yearly because of un-boiled
drinking water.
• Wood cut for cooking purposes contributes to the 16
million hectares of forest destroyed annually.
• Half the world’s population is exposed to indoor air
pollution, mainly the result of burning solid fuels for
cooking and heating.
“I’d put my money on the sun and solar energy. What
a source of power! I hope we don’t have to wait ‘til
oil and coal run out before we tackle that.”
Thomas Edison
Overview
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Types of cookers
Principles of solar cooker design
Retained heat cooking
Cooking guidelines
Teaching ideas
Examples
Additional information and resources
Types of solar ovens
• Box Cooker
• Panel Cooker
• Solar Funnel Cooker
• Parabolic Cooker - not recommended
Box cooker
• Among easiest and most popular to build and use
• Lid of a cardboard box reflects light onto pots under
glass
• Advantage of slow, even cooking of large quantities of
food
Panel Cooker
• Sunlight is reflected off of multiple panels onto a pot
under a glass lid or in a bag
• Can be built quickly and at low cost
• Many different varieties
Solar Funnel Cooker
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Safe, inexpensive and easy to use
Concentrates sunlight into a dark pot in a plastic bag
Combines best of parabolic and box cookers
Anyone can make one
Parabolic Cooker
• Highly focused light and high temperatures
• Cooks nearly as fast as a conventional oven
• Costly and complicated to make and use – have to turn
frequently to follow the sun
• Potentially hazardous-not recommended
The basic principles - C.A.R.E.S.
• Collect the light
• Absorb the light
• Retain the heat
• Ease and Efficiency
• Safety
C: Collect the Light
• Collect the sunlight using reflectors with an
approximately 400 square inch opening (20x20)
• Easy way to measure: the minimum opening of
the cooker needs to be the diameter of an
adult’s arm
• Reflective surface materials include: aluminum,
Mylar, aluminized Mylar of any thickness,
aluminum or chromium paint (Note: mirror like
reflectors can lead to eye damage)
A: Absorb the light
• Absorb the light – paint the pot matte black or
another dark color to absorb the heat
• Pots can also be elevated by a wire base or posts,
allowing the bottom of the pots to collect
sunlight
R: Retain the Heat
• Retain the heat – hot vessels lose their heat to
the air quickly so they need to be covered
• Cover with plastic, glass, Plexiglas, or tempered
glass
• A tight lid will trap steam and speed up cooking
Ex: Canning jars work like inexpensive pressure
cookers
R: Retain the Heat
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A note on plastics
Oven bags are the best way to retain heat. They are sold
in most large U.S. grocery stores, although they may be
hard to find in other places (Reynolds© bags work well)
If you can’t find oven bags, an alternate solution is
transparent High Density Polyethylene bags (HDPE)
Prevent the HDPE bags from touching the pots or jars,
as they may melt
Avoid polyethylene – it melts too easily
Good plastic may be the most difficult material to find,
and may require extra planning, possibly including
importing the oven bags
E: Ease and Efficiency
Ease – simplicity of everyday use
• Funnel and box cookers are the easiest to use – they
don’t have to be turned to follow the sun
Efficiency - how fast the cooker heats food
• Parabolic cookers focus light to a point (most efficient)
causing dangerous conditions
• Funnel cookers focus light across a broader area down
the center of the cooker (efficient but not dangerous)
S: Safety
• Safety – Avoid highly focused light such as that
in the parabolic cooker. It can damage eyes and
start fires
• Always exercise caution with cookers. Sunglasses
are useful when looking into a cooker
• Cooking pots are hot and should be treated as
though they were on a stove-top
Remember - C.A.R.E.S.
• Collect the light
• Absorb the light
• Retain the heat
• Ease and Efficiency
• Safety
Retained Heat Cooking
• If sunlight is lost or multiple items need to be
cooked, there is a solution
• Once the food is heated, quickly transfer to
either:
- an insulated box or set of towels,
- or an insulated hole in the ground covered
with more insulation
• The food will continue to cook for hours
Temperatures
• Sunny Day: heats from 130-145°C (265-300°F)
• Cloudy Day: heats from 95-105°C (200-220°F)
• Hot enough to pasteurize water (at least 65-70°C
for 20 minutes)
• Hot enough to fully cook meats, breads, grains,
vegetables, etc.
• Kills disease-causing bacteria
Impact
• Expect solar ovens to replace 60% of fuel needs
in most places
• The other 40% of the time, due to inclement
weather or special types of food, traditional
methods can still be used
• Doesn’t replace fire as a way to heat homes
Approximate Cooking Times
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Vegetables: 1.5 hrs
Rice/wheat: 1.5-2 hrs
Beans: 2-3 hrs
Meats: 1-3 hrs
Bread: 1-1.5 hrs
See Recipe File for more
details and cooking ideas
Costs and benefits
• Cost: approximately $2/cooker depending on
location and availability of materials
• Materials include cardboard, aluminum foil,
plastic bag, etc. See Building Instructions for
more details and be creative
• Benefits
– Saves cost of fuel or time spent gathering wood
– Prevents diseases from impure water
– Ecologically friendly
**Teaching Ideas**
• Give construction seminar
• Can accompany current educational programs
such as hygiene, gardening, or English/literacy
• Takes as little as half a day training
• Train a group to teach others--little efforts can
achieve large impacts
• Remember: Focus on training and sustainability
rather than handouts
Real World Examples
• Summer 2003 Fernando
successfully taught solar
cooking classes in
northeast Brazil with
Help International
• Four solar ovens
transform a Chilean
village (see packet)
• Microenterprise case
study in packet
Food for Thought
• Solar cookers can be a used for micro-enterprise
and other business ventures:
– Build and sell cookers
– Cook and sell bread or other foods
– See packet for examples and suggestions
• Adapt to local cultures and customs
BE CREATIVE and
HAVE FUN!
• You can improvise with most of the techniques
and materials
• Remember the basic principles (CARES) and
you can adjust for the skills and resources of
those who will make and use the ovens
Step-by-Step Instructions
– Funnel Cooker Instructions included on this CD
– Box Cooker are at http://solarcooking.org/ in both
the box cooker section and with pictures in the slide
show
– For more construction ideas see Alternative Cookers
PowerPoint also on this CD
Additional Resources
• Recipe File on this CD
• Packet of articles also on this CD including
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Background information
Case-studies
Ideas for micro-enterprise
Frequently Asked Questions
Contact list of NGOs using solar technology
Additional Resources
• Comprehensive Internet Site
www.solarcooking.org
• For questions or feedback contact Dr. Steven
Jones at Brigham Young University
– Email: stevejones@byu.edu
– Phone: (801) 422-2749