The Sustainability Workshop, as part of the Big Box Waste Re-Manufacture Project, collects cardboard and radiant barrier materials from local stores. These materials are processed into affordable solar cookers based on the Cookit model. Going even beyond the Cookit design, The Sustainability Workshop uses more complex geometry to optimize the performance of the diffuse reflector material, and also reduce the need to reposition the cooker, when made with more refined reflective surfaces.
Other work on solar cookers around the world has shown that the most cost-effective solar cookers use a cardboard backing material, an affordable specular liner, and a black pot in the center of relatively low mass, enclosed in a clear plastic bag to facilitate secondary greenhouse heating of the pot and food.
In winter on January 23, 2010, the 2nd and 3rd generation cookers were tested in 40 degree winter weather. Each was "cooking" a can of soup, enclosed in a clear plastic container with sealed lid. The 3rd generation cooker also had a secondary plastic enclosure and the addition of an aluminum pan for added thermal mass. After about 3-3.5 hours of peak daytime sunlight (with a few solar obstructions), the latest cooker had generated an internal temperature in the can of 160 degrees.
While the cooker worked, an extensive list of modifications were created for inclusion into the 4th generation design. Like the 3rd, the 4th will also be made from waste materials and available for a modest $20-$30.
Template for 3rd Generation Cooker
Construction of the backing for the 3rd Generation Cooker
First Generation Cookit Competitor
The first draft of the idea was a homegrown attempt without the use of CAD. As a result, it was a very rough prototype. However, the success of the design was found in the love the workshop cat found for the reflector. She was smart enough to know that when in the focal point, she reflected enough radiant heat energy from her body back towards her, such that she could be extremely comfortable.
The design at the top of the page represents the current design produced by the workshop. The modified Dodecahedron offers the best mix between cost-effective manufacture from waste materials, with also the benefit of a design that begins to optimize the common 3-4 hour cook time without the need for repositioning.