Cooking with the Sun Creating a solar cooker Judy Vondruska Image: http://www.grit.com/~/media/Images/GRT/Editorial/Blogs/Dave%20L/Solar%20Oven%20Homemade%20Granola%20Baked%20by%20the%20Sun/solargranola680.jpg?la=en Engineering Design for Physical Science July 27, 2016

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)

Addressing SD Engineering Standards

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

“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

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

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

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

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

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)

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

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

http://www. sciencebuddies http://www.sciencebuddies.org/blog/graphics/2013-blog-scientific-method-engineering-design-charts-750px.png

Engineering Design Process

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)

Additional Info

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 solarcooking.org

Resources Solar Cookers International (solar cooking in the classroom) http://www.solarcookers.org/involved/teachers-and-students/ Solar Cookers International (how solar cookers work) http://www.solarcookers.org/basics/how.html Solarcooking.org (solar cooker plans) PBSKids – Solar Cookers http://pbskids.org/zoom/activities/sci/solarcookers.html Basics of Solar Cooker (video) https://www.youtube.com/watch?v=v5CdNH3sQT0 NASA Climate Kids (“Make Sun S’mores!”) http://climatekids.nasa.gov/smores/ Solar Cookers (adapted PPT) http://solarcooking.org/introduction-to-solar-cooking.ppt