Between February and October 2021, I created three different prototypes of the solar cooker.
FEBRURARY 17, 2021
The first prototype was created using household materials (an old shoebox, packaging tape, cling wrap, tinfoil, a food-grade thermometer, and a dark-colored paper shopping bag.) Using a ruler and marker, I sketched out a rectangle on the top of the lid (approximately 1 inch away from the edges on the front and the left and right side) before using scissors to cut it to create a flap. Next, I wrapped the tinfoil around the bottom part of the flap and taped it on from the top. I continued by measuring the inside dimensions of the box before cutting out the dark-colored shopping bag and gluing it to the inner walls and bottom of the box. The dark paper was added on the inside to help insulate the oven. Since the shoebox I used was old, I stuck tape around the sides where the lid meets the box. I did this to prevent heat from escaping the cooker from the small gaps. I cut a small hole into the front of the shoebox (at the very middle) that was just big enough for to insert the food-grade thermometer. Lastly, I put cling wrap over the part of the lid underneath the flap, with the flap standing upwards.
For the model to be eligible for experimentation, it needed to be able to reach 60Cº. Unfortunately, upon leaving the prototype out in the sun, it could only reach the 30-40Cº range. This is likely because the shoebox was very old and had many small rips and tears, which may have let the heat out.
APRIL 29, 2021:
Despite this minor speed-bump, I created another prototype using better materials (small cooler, food-grade thermometer, reflective tape, black tape, and a clear plastic book holder) to have better insulation. I used a small rectangular cooler as the base for the oven. I wrapped the reflective tape around the bottom part of the lid to act as the reflective surface while the black tape was put inside the box, covering the walls and bottom. Next, I needed to cut a small hole for the thermometer to fit inside the box. Not to mention, I also needed to cut a flat rectangular piece of plastic from the plastic book holder to use as the cover. I was able to get in touch with a technician, Mr. Yung, who works at the Hong Kong University of Science and Technology to operate the machinery in the design lab. The technician used a drill to cut a small hole in the middle of the box’s front side for the thermometer to go through. Next, he utilized a machine with a moving blade to cut out the plastic sheet. Lastly, I stuck the thermometer through the box and slid the plastic sheet on the opening of the box (with the lid open.) This prototype was much more durable and reached a much higher temperature (70Cº) than the original mockup.
OCTOBER 12, 2021:
Although the second prototype was able to reach 60Cº, I found that there were still some issues with it. For one, the plastic sheet that covered the opening of the oven was not big enough to cover the entire opening. There was a small gap near one of the edges where heat could escape. As a result, the box was not insulated very well and it took much longer for the oven to heat up. Not to mention, the box was only big enough to fit one mask at a time. I decided to create a third mockup in an attempt to address these issues. The newest model used a slightly bigger cooler. Despite the larger size, the newest prototype shared most of the same elements as the second mockup. However, upon taking the materials to the technician to construct the oven, he was kind enough to offer his own sheet of plastic from the design lab. He used a lazer cutter to cut the plastic with the exact dimensions to fit the box. In doing this, the plastic sheet fit perfectly over the opening of the oven and left no gaps where heat could escape.