1. Cooking with the Sun Creating a solar cooker
Judy Vondruska
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Engineering Design for Physical Science July 27, 2016

2. Addressing SD Physical Science Standards
Middle School Physical Science
Design, construct, and test a device that either minimizes or maximizes thermal energy transfer.* (SEP: 6; DCI: PS3.A, PS3.B, ETS1.A, ETS1.B, ; CCC: Energy/Matter)
Develop and use a model to describe how waves are reflected, absorbed, or transmitted through various materials. (SEP: 2; DCI: PS4.A, PS4.B; CCC: Structure)
High School Physical Science
HS-PS3-1: Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known. (SEP: 5; DCI: PS3.A, PS3.B ; CCC: Systems)
HS-PS3-4: Plan and carry out an investigation to provide evidence that the transfer of thermal energy when 29 two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system (Second Law of Thermodynamics). (SEP: 3; DCI: PS3.B, PS3.D; CCC: Systems)

3. Addressing SD Engineering Standards

4. 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.
solarcooking.org

5. “I’d put my money on the sun and solar energy. What a source of power
“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
solarcooking.org

6. Benefits of Solar Cooking
Consumes no fuels/wood
No loss of trees & habitat
Trees sequester carbon
Generates no air pollution
Generates no greenhouse gases
Produces no smoke
Cooking smoke kills over 1.6 million people each year, mostly women & children, according to a recent report
Eliminates fire dangers
solarcooking.org

7. More Benefits of Solar Cooking
Eliminates work
No daily search for firewood
2 Billion people rely on wood for cooking fuel!
No risks to women and children
Frees time for other activities
No need to stir food
Helps to liberate women
solarcooking.org

8. More Benefits of Solar Cooking
Cooks foods slowly and thoroughly
Preserves nutrients
Foods will not burn
Pots are easy to clean; less clean water is needed
Use for canning vegetables
Use for dried fruit
Kill insects in dry grains
solarcooking.org

9. Solar Cooking How Long Does it Take?
Vegetables: 1.5 hrs
Rice/wheat: hrs
Beans: 2-3 hrs
Meats: 1-3 hrs
Bread: hrs
solarcooking.org

10. The Challenge Part 1 – Assemble and test potential solar cooker models Part 2 – Redesign for simplicity and efficiency
An earthquake has devastated a rural area in northern Afghanistan. Roads are impassable leaving only the ability to airlift in supplies. There is no electricity and no potable water for the victims.
Design a solar cooker that can be dropped by airlift as a kit, assembled by local inhabitants and used to pasteurize water (at least 65-70°C for 20 minutes)

11. Science Concepts Absorbance/Reflectance Law of Reflection
Methods of Heat Transfer
Conduction
Convection
Radiation
Absorbance/Reflectance

12. Science and Engineering Practices
Asking Questions and Defining Problems
Developing and Using Models
Planning and Carrying Out Investigations
Analyzing and Interpreting Data
Using Mathematics and Computational Thinking
Constructing Explanations and Designing Solutions
Engaging in Argument from Evidence
Obtaining, Evaluating, and Communicating Information
Chapter 3: page 41 of Framework

13. http://www. sciencebuddies

14. Engineering Design Process

15. The Challenge Part 1 – Assemble and test potential solar cooker models Part 2 – Redesign for simplicity and efficiency
An earthquake has devastated a rural area in northern Afghanistan. Roads are impassable leaving only the ability to airlift in supplies. There is no electricity and no potable water for the victims.
Design a solar cooker that can be dropped by airlift as a kit, assembled by local inhabitants and used to pasteurize water (at least 65-70°C for 20 minutes)

16. Additional Info

17. Types of solar ovens Box Cooker Panel Cooker Solar Funnel Cooker
Parabolic Cooker
solarcooking.org

18. 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
solarcooking.org

19. 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
solarcooking.org

20. Solar Funnel Cooker 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
solarcooking.org

21. 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
solarcooking.org

22. The basic principles - C.A.R.E.S.
Collect the light
Absorb the light
Retain the heat
Ease and Efficiency
Safety
solarcooking.org

23. 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)
solarcooking.org

24. 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
solarcooking.org

25. 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
solarcooking.org

26. R: Retain the Heat
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
solarcooking.org

27. 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)
solarcooking.org

28. S: 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
solarcooking.org

29. Remember - C.A.R.E.S. Collect the light Absorb the light
Retain the heat
Ease and Efficiency
Safety
solarcooking.org

30. 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
solarcooking.org

31. Temperatures Sunny Day: heats from 130-145°C (265-300°F)
Cloudy Day: heats from °C ( °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
solarcooking.org

32. Resources Solar Cookers International (solar cooking in the classroom)
Solar Cookers International (how solar cookers work)
Solarcooking.org (solar cooker plans)
PBSKids – Solar Cookers
Basics of Solar Cooker (video)
NASA Climate Kids (“Make Sun S’mores!”)
Solar Cookers (adapted PPT)