Last edited: 24 April 2020      

The Cal Poly Solar Cooking team at California Polytechnic State University, San Luis Obispo is working to design a reliable Scheffler reflector. They aim to simplify the designs of the original Scheffler reflector for ease of construction and use. They are also doing research on photovoltaic cooker designs that makes us of a photovoltaic panel to generate electricity, which is then used to cook with.

Cal Poly Scheffler Reflector

Design[edit | edit source]

The Cal Poly Scheffler Reflector was built from the design on http://www.solare-bruecke.org/ of a 2 m2 aluminium reflector.

Work is currently being done on a new design using a fiberglass dish based on the principles of a deformable dish that tracks the sun with a fixed focus. Deformation of the dish will be accomplished using tensioned strings that run vertically and horizontally accross the sun-gathering side.

Parabolic Dish[edit | edit source]

Typically, a parabolic dish is constructed with metal crossbars bent to their proper radii of curvature individually and then mounted on an elliptical frame. This must be done carefully and with high attention to detail because the dish will not focus correctly if the crossbars are not exact.

The team at Cal Poly is exploring alternative ways of constructing the parabolic dish. They have made a mold to make fiberglass dishes, and one dish has been made out of two layers of 2

The mold in its final stages of sanding

4 ounce fiberglass cloth.

Our first fiberglass dish, still on the mold

Solar Tracking Device[edit | edit source]

A solar tracking device was successfully built by the Cal Poly team and implemented with the reflector. A circuit was set up to compare the light hitting two photoresistors separated by a divider, and to deliver voltage accordingly to a motor connected to the rotational chain of the reflector. The device is battery-operated.

Main article: Solar tracking

Thermal Storage Unit[edit | edit source]

A thermal storage unit was designed and built in conjunction with the reflector in 2010. Materials used were concrete, rebar, and a square metal plate as cooking surface. Eleven wired thermistors were embedded into the poured concrete and labeled according to location. Eight are still connected externally. Although we were unable to know exactly where these thermistors were located due to concrete settling, they still allowed us to test the heat retention of the unit. They also gave us an idea of the temperatures reached.

Testing of the unit is ongoing, but it is clear that our current unit is not reliable enough to integrate with the existing reflector. Designing a useful thermal storage unit is currently a secondary priority.

Main article: Thermal storage

Publications[edit | edit source]

  1. Insulated Solar Electric Cooking – Tomorrow's healthy affordable stoves? - T. Watkins, P. Arroyo, R. Perry, R. Wang, O. Arriaga, M. Fleming, C. O’Day, I. Stone, J. Sekerak, D. Mast, N. Hayes, P. Keller, P. Schwartz - Development Engineering 2 (2017) 47–52. See the associated video.
  2. Hot Diodes!: Dirt Cheap Cooking and Electricity for the Global Poor? - Grace Gius, Matthew Walker, Andre Li, Nicholas Adams, R. Van Buskirk, P. Schwartz - Development Engineering, 4 (2019) 100044
  3. Redirecting Sunlight with Polar Tracking in Developing Countries and Elsewhere (in an online library a design for a polar tracking concentrator)

Articles in the media[edit | edit source]

Audio and video[edit | edit source]

  • August 2019: 
Solar_Electric_Cooking_in_Ghana_With_Phase_Change_Thermal_Storage,_Pete_Schwartz,_Cal_Poly_Physics

Solar Electric Cooking in Ghana With Phase Change Thermal Storage, Pete Schwartz, Cal Poly Physics

August, 2019, we spent 3 weeks in Ghana. We made Solar Electric Cookers with Phase Change Thermal Storage with our newly made friends and colleagues. We introduced this cooking method in a small village without electricity

  • February 2017:
Insulated_Solar-Electric_Cooking_Technology_and_Uganda,_Pete_Schwartz,_Cal_Poly_Physics

Insulated Solar-Electric Cooking Technology and Uganda, Pete Schwartz, Cal Poly Physics

  • September 2014: 
Cal_Poly_San_Luis_Obispo_Solar_Cooker_Research

Cal Poly San Luis Obispo Solar Cooker Research

Under the direction of physics professor Dr. Peter Schwartz, a team of physics and engineering students at Cal Poly San Luis Obispo in California are conducting research on a simplified Scheffler reflector design that could be used by people in developing countries to heat water and cook food. They are also researching hybrid technologies that combine the use of a solar reflector and a Rocket Stove for uninterrupted cooking.

See also[edit | edit source]

External Links[edit | edit source]

Contact[edit | edit source]

Cal Poly Solar Project
San Luis Obispo, California USA

Email: cpsolar@googlegroups.com
Facebook: https://www.facebook.com/cpscheffler

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