Solar ovens heat using the same principles like the hotness of an interior of a car in the sun. The reflectors concentrate the sun's rays through the back and forth heating. Once the oven thermometer indicates the oven is hot, food is placed in the oven. Food takes longer to cook at low temperatures, but the slow cooking makes it easier for more tasty meals.
The solar oven is an excellent tool to demonstrate physical science concepts to many people. It contains Newton’s Law of Heating and the following principles of heat gain, heat loss and heat storage before they experiment with the solar box oven.
Our blueprint created by me:
Photos:
Here are some clips of the work we did to prove to you, we handmade it!
Project:
Madi and I started to find measurements for the whole solar oven. We then cut pieces out and put them all together(reflectors,base,etc.). Soon we started to cover the whole box with insulation to trap the heat, and tapped it down with duck tape. Then, we covered it all in tin foil, and tapped it again to trap heat.
The hottest temp it got to was 114 degrees fahrenheit
Physics:
Newton’s Law of Heating. Food placed in a 250 degree oven will take longer to cook than the same food placed in a 350 degree oven. 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.
The greatest amount of heat loss is through convection, when warm air rises and pushes its way out through the spaces between the inner box lid and the glass. Strips of adhesive-backed foam weatherstripping added to the edges of the glass slow the heat loss due to convection considerably.
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. The section on “Using the Solar Cooker” has ideas for using bricks to experiment with this idea.
Reflection:
This project was probably one of my favorites because i had a ton of freedom, and i enjoyed how much fun i had with it. I think the most difficult part about this project was building the structure and how much time it took to build and cover. We needed precise measurements and also the right type of insulation and foil so it would work properly. The day we tried the oven out was on the hottest day we had in the time frame of our project, it got to 114 degrees! It was awesome. Our project was very hot, but i thought it wasn't going to work well enough because we had no cover! But it still was hot enough and the reflectors worked very nicely! We also painted the whole thing black to absorb the heat more. The main purpose for our project was to melt butter for our "waffle party" for kids to have butter on their waffles melted! I will never foget all the amazing memories in my STEM class freshman year, and it was truly amazing!