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Cal Poly Scheffler Reflector

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Last updated: September 12, 2013      

A research team at Cal Poly State University, San Luis Obispo is working to design a reliable Scheffler reflector. We aim to simplify the designs of the original Scheffler reflector for ease of construction and use.

SolarScheffler

Cal Poly Scheffler Reflector

DesignEdit

The Cal Poly Scheffler Reflector was built from the design on http://www.solare-bruecke.org/ of a 2m2 aluminium reflector.1

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 DishEdit

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
Photo 1

The mold in its final stages of sanding

4 ounce fiberglass cloth.
Cal Poly Solar mold with fiberglass

Our first fiberglass dish, still on the mold

Solar Tracking DeviceEdit

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 UnitEdit

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

Audio and videoEdit

Cal Poly San Luis Obispo Solar Cooker Research05:04

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 alsoEdit

External LinksEdit

ContactEdit

Cal Poly Solar Project
San Luis Obispo, California USA

Email: cpsolar@googlegroups.com

Like us on Facebook: https://www.facebook.com/cpscheffler

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