what's cooking with solar ovens?

Energy in Hawai'i
In our studies relating to climate change, my students have been researching Hawai'i's energy production and consumption. We are very fortunate to have multiple renewable energy sources, such as solar, wind, biomass, hydroelectric, and geothermal, but renewables only account for about 8% of our total energy consumption. Over 85% of our energy comes from domestic and international petroleum imports. That's right, most of our electricity comes from the burning of oil. 

One energy source that really interests my students is solar energy. Despite the intensity and duration of our sunlight here in the tropics, students were surprised to learn that less than 2% of our energy consumption comes from solar energy. Yet progress toward a more energy-independent Hawai'i is being made, and solar energy is increasingly popular. In fact, right now, photovoltaic panels are being installed on the roofs of our school that will convert solar energy into electricity to power Star of the Sea. 

Engineering Solar Ovens
But how about harnessing solar energy to cook food? Solar ovens, also called solar cookers, convert sunlight into heat energy, which gets trapped in the oven and raises its temperature. My students were challenged to design and build a solar oven that would maximize solar heat gain and retain the heat for cooking. To construct their ovens, the students used common household materials, including many reused and recycled items such as chip bags, newspaper, and shoe boxes.  

Constructing the solar ovens

Solar ovens should be covered with reflective material, such as aluminum foil, in order to catch as much sunlight as possible. Used chip bags, cleaned and turned inside out work well for this purpose. There needs to be a window-like opening on the top of the oven covered with clear plastic. Most students left the flap when they cut the opening which was then engineered so the angle could be adjusted. Sunlight, both direct and reflected, enters the oven through this clear opening and gets trapped. Crumpled newspaper is a good insulator to line the inside of the box. Black construction paper works well as a cooking surface on the bottom of the box because it absorbs a lot of heat. If you've ever worn a black shirt on a hot day, you understand this concept!

Our Solar-Oven Cook-Off!

A beautiful sunny day for solar oven cooking!

A popular solar oven entree was nachos. Chips were placed on aluminum foil and sprinkled with grated cheese that melted as the solar oven heated up. Students enjoyed the nachos with fresh salsa later. And what about a s'mores cup for dessert? Chocolate chips and mini-marshmallows were placed in a foil muffin liner, and they melted into a gooey dip for graham crackers. Our dishes took awhile to cook, about four hours on average. Some of our ovens reached high temperatures over 180 degrees F. 

Cooking nachos and s'more treats!

Solar ovens can be helpful tools in regions where there is no or limited electricity, as a more sustainable alternative to wood-burning fires. These solar ovens vary in design and size, but they work on the same basic principles of radiant energy. These ovens are incredibly useful not only for cooking food but also for pasteurizing drinking water. Even in areas with other options, solar ovens can be used to conserve electricity and cook delicious meals with clean (free) energy!