For our final project of freshman year we were assigned to engineer a science fair project. My partner Annabel and I decided we were going to design our own solar oven. It took a few days to make the blueprint, but once we figured it out we were ready to start constructing our oven. We completed the project in a week and we had a super fun time doing it. We got inspiration for the shape of the solar oven from the cold frame. We did this because the cold frame wants to bring in as much sunlight as possible and that's what we wanted our solar oven to do. We lined the whole box with reflective insulation and then covered the insulation in tin foil. We also painted the oven black to help absorb some heat.
Photos
Presentation
Physics concepts
Newton’s Law of Heating. Newton’s Law of Heating provides a more precise description of how the rate at which items cook is affected by the starting temperature of the food and the temperature of the oven. The rate at which food cooks is proportional to the difference between the temperature of the food to be cooked and the temperature of the oven. In equation form, the law relates [Rate at which food cooks] = k (Oven temperature - Food temperature). The same law demonstrates that the rate at which the oven heats is better on a hot day than a cold day.
Heat gain. The heat gain inside a solar box cooker is due to “the greenhouse effect.” Sunlight passes easily into glass covered enclosures. Once light is absorbed by materials within the enclosure, it is transformed into longer wavelength heat energy. Dark materials placed in the bottom of the oven will absorb more sunlight and generate more heat. If the heat energy builds up faster than it is lost, the oven will become hotter. A poorly insulated oven will lose heat too fast to attain temperatures hot enough to cook. The solar box cooker has a dark cookie sheet in the bottom and is wrapped with good quality insulation to allow for adequate heat gain and retention.
Heat Loss. The loss of heat from a solar oven is described by the Second Law of Thermodynamics, which explains how heat travels from hot to cold. Heat loss is a combination of conduction, radiation, and convection. Heat is lost from the solar oven by conduction, when the heat travels through the molecules of the physical box to the outside air. Radiation is also a factor in heat loss, when hot air radiates through the glass lid. The aluminum foil and foil tape used throughout the construction slow the heat loss due to conduction and radiation.
Heat storage. The capacity of a solar box cooker to hold heat increases when more mass is placed inside the oven. The oven takes longer to heat with heavy materials inside, but will hold heat longer through periods when the sun is covered with clouds.
Heat gain. The heat gain inside a solar box cooker is due to “the greenhouse effect.” Sunlight passes easily into glass covered enclosures. Once light is absorbed by materials within the enclosure, it is transformed into longer wavelength heat energy. Dark materials placed in the bottom of the oven will absorb more sunlight and generate more heat. If the heat energy builds up faster than it is lost, the oven will become hotter. A poorly insulated oven will lose heat too fast to attain temperatures hot enough to cook. The solar box cooker has a dark cookie sheet in the bottom and is wrapped with good quality insulation to allow for adequate heat gain and retention.
Heat Loss. The loss of heat from a solar oven is described by the Second Law of Thermodynamics, which explains how heat travels from hot to cold. Heat loss is a combination of conduction, radiation, and convection. Heat is lost from the solar oven by conduction, when the heat travels through the molecules of the physical box to the outside air. Radiation is also a factor in heat loss, when hot air radiates through the glass lid. The aluminum foil and foil tape used throughout the construction slow the heat loss due to conduction and radiation.
Heat storage. The capacity of a solar box cooker to hold heat increases when more mass is placed inside the oven. The oven takes longer to heat with heavy materials inside, but will hold heat longer through periods when the sun is covered with clouds.
Reflection
This was by far my favorite project because we got to have a lot of freedom and we could really use our imagination. I loved being able to work with Annabel. We work very well as a team. I really don't have any "lows" for this project. I wish we maybe came up with the blueprint sooner so then we could have started building sooner, but everything worked out very well. I really loved freshman year of S.T.E.M. and I can't wait for next year!