Insulated Solar Electric Cooker with Solid Thermal Storage

This Senior Project report outlines the design for our senior project under the Mechanical Engineering department of California Polytechnic State University. Insulated solar electric cookers (ISEC) are a relatively novel and exciting solution to the ethical, environmental, and medical issues associated with the conventional cooking methods - burning of biomass and charcoal - practiced in nonindustrial countries around the world. ISECs use solar energy input from a solar panel to cook food within an insulated chamber and have been researched and developed by Dr. Peter Schartz and his research group over the past several years. However, our target users expressed the desire not only to cook directly with solar power during the day, but also to be able to cook with ISEC in the evening. Essentially, they wanted a thermal “battery” that could be charged with solar energy during the day and discharged to cook food in the evening. The goal of our senior project was to design, implement, and test a solid thermal battery, which we will refer to as solid thermal storage (STS), into ISEC. After researching existing solutions and performing background research on our users\u27 needs and wants, we began ideating many possible solutions. We refined these solutions using decision matrices to weigh our intended functions and concept prototypes. After converging our ideas to outline a design direction, we began building structural prototypes to conduct specialized tests that helped us iterate the design to better meet our requirements. We realized that our biggest design challenge was creating a heater that could both store energy in our STS and allow that stored energy to transfer ] effectively through the heater to our cookpot. After iterating upon our structural prototypes, we arrived at a verification prototype that includes a heater disk, STS, and an actuation system implemented into an existing ISEC prototype. We then performed a series of design verification tests to validate the effectiveness of our design. We found that the charged STS is capable of cooking without input power, and the fluctuations in solar intensity are dampened by the thermal mass of the heater. We also found that our heater disk was effective at cooking directly with solar energy as opposed to stored energy cooking. Through our testing and analysis, we believe that STS and our heater design should be further pursued by the ISEC team to utilize its benefits in cooking applications