This article by Jamila Kyari is a free download from the Autumn 2018 Green Teacher magazine. It begins:
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.