Sun-Powered Lunch Hours

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Originally appears in the Fall 2018 issue.

FROM MAKING MINI pizzas and hotdogs to s’mores and chocolate chip cookies, building and cooking with a solar oven does more than make school lunches interesting. It also offers fun opportunities to introduce students to the power and versatility of the sun’s heat. Amidst changes in attitudes towards a clean energy economy, students can learn about the sun’s role as the ultimate source of renewable energy. Hence, it is necessary to educate youth about renewable energy technologies, especially those that use the power of the sun. An activity like building a solar oven is a hands-on way to facilitate positive learning outcomes around sustainable, energy-efficient methods of cooking.

A solar oven is a contraption that absorbs the sun’s heat, which is transferred through radiation into an insulated container. Inside the solar oven, the trapped heat from the sun’s rays accumulates and is used to cook food. The sun emits radiation, consisting of electromagnetic rays, including ultraviolet A (UVA) and ultraviolet B (UVB) rays. A solar oven usually collects these UV light rays inside it, which then get converted into longer infrared light rays that heat food molecules. If you have ever left your car out under the sun on a hot day with the windows shut, you might have experienced this type of scenario, often called the greenhouse effect: sunlight enters the car through the windows and becomes trapped inside, thus heating the whole interior. This concept is the same with solar ovens. An effective solar oven will use the energy of the sun to heat a cooking vessel and efficiently retain the energy (heat) for maximum cooking effectiveness.

There are three main types of solar ovens: solar box ovens, parabolic ovens, and panel ovens. They all require maximum exposure or tilting towards the sun, and each can cook food at a high temperature. A high-performance solar oven can convert more than eighty per cent of the incoming sunlight into heat. On a windy day, when a solar oven’s temperature is not high enough, the food might need to be left under the sun for many hours in order to cook fully. Therefore, it is important to be very careful when cooking food items such as meats or dairy products that might pose health hazards if not fully cooked within a short period of time.

At the most basic level, a solar oven demonstrates the differences between cooking food with renewable and non-renewable energy. Solar energy is abundant, clean, and has no negative environmental impacts, whereas fossil fuels are unsustainable and emit large amounts of greenhouse gases and pollution. Teachers, then, can use the activity of building a solar oven to show students how other important solar inventions work. Using products like solar cells, solar hot water heaters, and skylights reduces our dependency on fossil fuels and cuts our energy costs.

     Building a solar oven that really cooks can teach youth about transforming the power of the sun to meet our energy needs, and it also helps students to build 21st century skills in the process. To develop these skills, students are encouraged to work in groups to foster collaboration and communication. While constructing their solar ovens, youth can be inspired to showcase their creativity and innovation as they take ownership of the activity and think of ways that their solar ovens can stand out. They are also encouraged to participate in global citizenship as they envision how a solar oven might benefit people in parts of the world where food is cooked with wood fires and fossil fuels, and where electricity is not reliable or readily available for cooking. Finally, students use their critical thinking and problem-solving skills to test concepts such as heat transfer and insulation in order to determine the best solar oven design.

As a fun science or STEM activity that is well-suited to students from grades 3 and up, building a solar oven can be done in an informal or outdoor setting. It can also be linked to culinary arts as students are tasked with the challenge of brainstorming different types of delicious recipes that can be made. It works equally well as an after-school program or summer camp activity.

The Solar Oven Challenge
Since 2005, youth from schools across Canada have been participating in the annual Re-Energy Solar Oven Challenge: a science construction and cooking activity with delectable results. The challenge was designed to teach students about solar heat, solar electricity, and other clean energy technologies, but it can be modified to incorporate culinary arts, food safety, and culture. During the challenge, students are first invited to use detailed construction plans to build working models of a solar oven. Participants then cook tasty treats under solar heat for a chance to win a class prize.

In 2013, St. Mark’s Separate School’s grade 5/6 class in Mississauga, Ontario built a variety of solar ovens. They used their math skills to create blueprint designs, using metre sticks and protractors to accurately measure angles. One of the solar ovens was called the Vulcanator, named after the Roman god Vulcan, god of fire. In their design, a concave mirror was used to focus the sun’s rays on the black heating chamber to warm the food. Another of their designs was called the HIVE, which followed a hexagon design with classic reflectors built at the top. The reflectors were made out of cardboard panels covered in tinfoil, which was cut into thin trapezoids and placed shiny-side-up. Students used the HIVE to roast veggie kabobs and cookies. In the past, class recipes have featured salsa hotdogs, casseroles, bannock, and more. A wide range of recipes can be cooked in a solar oven, provided it is able to heat up to the right temperature. A solar oven at 250 degrees Celsius is hot enough to boil rice if it is left to cook for over one hour.

Participating schools have used various approaches to the Solar Oven Challenge. For example, in the same year, student groups from King Edward Public School in Toronto, Ontario, were asked by their teacher to submit a detailed written proposal prior to building their devices. Each proposal needed to include a technical drawing of their device, their test method(s), and a design description with a focus on the science involved in the planning and building of their chosen device. The students built the cookers during class time and later each group also created an infomercial to promote their final product.

     Building a solar oven is one thing and then testing it is another, but practice does make perfect. For testing days, it is important to watch the weather forecast, then select a day that is clear, bright, and sunny with high temperatures so that the solar oven can heat up to bake tasty treats. At Scott Central Public School. in Sandford, Ontario, the grade 7 science class faced many challenges with weather conditions in the testing phase. It was overcast and rainy and they could not cook their recipe as a result. However, all the students were still able to learn about the principles of solar heat as they had to first design, then build, and finally test their ovens. Fast forward to 2018 and the school emerged as the winner of this year’s Solar Oven Challenge by coming in first place in the competition.

Educators who participate in building a solar oven have consistently provided positive feedback. One teacher at the Consort School in Alberta offered the following:

“Students were highly engaged when building their solar ovens. The level of cooperation was outstanding as they worked together to lay down lengths of tinfoil as flat as possible. Everyone was really excited when the ovens heated up so quickly during testing. They were proud when all the grade 5s and 6s were so curious about how the cookies and brownies were baking. The cookies were delicious. Many students saved a cookie to share with someone special at home or in another class.”

     Building a solar oven also encourages real-world learning. A teacher at Magnetawan Public School in Magnetawan, Ontario said, “From the overwhelming success of this Solar Oven Challenge, we will offer a mini barbecue at the end of the year where the solar ovens will be used to feed the school. This will be the ultimate test if their designs were effective and if they can be used in real-world applications.”
There is no better way to put the solar power in your lunch hour than to host a school-wide cookout using solar ovens built by students.

Solar Cooking Websites:

• American Solar Challenge: http://americansolarchallenge.org/the-competition/american-solar-challenge-2018
• Outdoor Cook: http://www.outdoorcook.com/solar.php
• Solar Oven Challenge: http://www.re-energy.ca/solar-oven-challenge
• Solar Cookers International: http://solarcooking.wikia.com/wiki/Introduction
• Solar Oven Society: https://www.solarovens.org/recipes/
• Video tutorial by Scovan Engineering in partnership with GreenLearning https://www.youtube.com/watch?v=jV-Zq_DI8Ps&t=24s

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Jamila Kyari is a Communications Manager with GreenLearning, based in Kitchener, Ontario. She works with teachers and students on a variety of environmental education programs in the areas of energy, climate change, and green economy. She would welcome feedback at jamila@greenlearning.ca.