1. Efficient Solar Cooker
Presented by:
Viraj Trivedi
CEPT MTM-AM3411

2. The Problem
Half the world’s people must burn wood or dried dung to cook their food.
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.
Conventional Solar Cooker don’t work in evening and cloudy weather.

3. “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

4. Overview Types of cookers Principles of solar cooker design
Temperature
Cooking time
Impact
Energy storing materials

5. Types of solar ovens Box Cooker Panel Cooker Solar Funnel Cooker
Parabolic Cooker - not recommended

6. 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

7. 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

8. 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

9. 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

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

11. 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)

12. 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

13. 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

14. R: Retain the Heat 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

15. 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)

16. 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

17. 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

18. Impact Expect solar ovens to replace 60% of fuel needs in most places
The other 40% of the time, due to rough weather or special types of food, traditional methods can still be used
Doesn’t replace fire as a way to heat homes

19. Approximate Cooking Times
Vegetables: 1.5 hrs
Rice/wheat: hrs
Beans: 2-3 hrs
Meats: 1-3 hrs
Bread: hrs

20. Solar Energy Storing Materials
Thermal mass system-  materials with high specific heat capacities such as water, earth and stone.
Phase change materials- paraffin wax and Glauber's salt
Molten salts
Pumped-storage hydroelectricity
Natural zeolites
Modified Carbon Nanotubes

21. Thank You