Concentrated Cooker Subteam

This semester the concentrated cooker sub-team will look into methods for focusing more light into the cookers than the cooker glazing intercepts on its own.   We are especially interested in using fresnel lenses.

Our objective is to optimize the capability and efficiency of existing solar ovens, specifically by harnessing even more sunlight than the solar ovens can inherently absorb. Solar cookers are designed to utilize primarily direct sunlight; however, in this group, we strive to find ways of using lenses and reflectors to redirect that which wouldn't normally reach the cooker.  Ideally, we want to be able to use the lenses to access more sunlight overall so it can be more efficient and reach higher temperatures. In accordance with our target community's local culture, reaching frying temperatures could be a significant breakthrough, as it would allow for staples such as tortillas to be prepared. Since glass lenses are cumbersome and brittle, as well as expensive, this group will be looking into a more durable, more easily manufactured, and cheaper lens--the Fresnel lens. 

Traditional methods of concentrating light with Fresnel lenses involve only concentrating light to a single point. With this method, temperatures high enough to melt metals are attainable. However, as stated above, our goal is to work with the already existing solar ovens in order to enhance their performance. Concentrating light to a single point alone would not achieve this goal. Due to the limited research on using Fresnel lenses without solely concentrating light to a single point (or line), we will need to do preliminary research to understand the properties of the lenses before creating a design to use them to supplement the solar ovens. Our research will focus chiefly on their ability to redirect light and concentrate light to the areas right after and right before the focal point of the lens.  

Our first set of tests will be conducted using lasers, as the lens' behavior is dependent on the presence of parallel beams of light. After understanding the basic mechanism for concentrating and redirecting light using the lenses, we will come up with a working design to supplement the solar ovens. Depending on the properties of the lenses, our design might incorporate reflectors to take full advantage of their properties. Currently, we plan on using the reflective material available in the lab to design reflectors.

Pending the results of our preliminary testing, our end goal is to use the lenses and reflectors to reach higher temperatures inside the ovens, ideally high enough to fry food. In addition, we need to consider the cost, the accessibility and the practicality of daily use of the lenses. We aim to refine design practices until these goals are met.   

For More Information:

• Final Report Spring 2011
• Fresnel Lenses and Non-imaging Optics Articles