Solar Oven Performance Standards

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From Jim Arwood:

My office has been working with various individuals and organizations in Arizona on Solar Oven Performance Standards. Part of the motivation for developing standards in Arizona is that a solar tax credit exists for a variety of solar devices -- solar cookers being the exception. Toby Schneider, chairperson of Citizens for Solar, is a leading advocate for the tax credit being extended to include solar ovens. Toby has put a great deal of time and effort into the development of performance standards, and has submitted a draft to our office for review and input. He has also submitted a copy to the Sunletter (Arizona Solar Energy Association's newsletter -- of which I edit -- for publication). Others having offered input into the development of the draft proposal include Barbara Kerr and Paul Funk.

Below is the Solar Oven Performance Standards (Proposal) that Toby has written. If anybody would like to comment directly to Toby, his address is 4417 N. Pomona. Ave., Tucson, Arizona 85705-1311. Or, you can e-mail Jim Arwood at and I will relay your comments onto Toby.

Solar Oven Performance Standards (Proposal)
Prepared by Toby Schneider
Revised: 1/3/96 and 8/25/96

1.0 -- Statement of Purpose: This paper is meant to be a guide to allow comparisons between different solar oven/cooker designs. These designs provide a wide range of performance versus cost while still cooking food satisfactorily. The only way to compare these designs is to establish a standard set of conditions that can be repeated in a scientific manner.

2.0 -- Definitions of Solar Oven/Solar Cooker: In general, a solar oven can accommodate a wide variety of cooking platforms -- bread pans, cookie sheets, covered bowls and casserole dishes. Solar cookers have a dedicated cooking chamber that typically does not vary with the food being cooked.

3.0 -- Test Conditions: Start on a clear sunny day at 10:00 a.m. Heat one (1) quart of water starting at 77 degrees F (25 degrees C) in an appropriate pan (covered) for the oven or cooker under test. The test should continue as long as required or until the water reaches 185 degrees F (85 degrees C).

Measure the time this change in temperature requires. Temperature shall be measured by an immersion thermometer or a type J thermocouple. Ovens or cookers should be aimed at the sun as expected in normal usage (either not corrected for sun position changes or corrected as required).

3.1 -- Corrections for altitude should not be made. 185 degrees F kills bacteria in all altitudes.

4.0 -- Evaluation Criteria:

Evalutation    Class     Degrees                  Time       Typical  
                                   Usage

                                   
Best      Class I   2 lbs. water to 185 F    1 hr.     Lg  meat
                                   all else


Best           Class II  2 lbs. water to 185 F    2 hrs.       Casseroles
                                   bread
                                   beans
                                   rice


Better         Class III 2lbs. water to 185 F     3 hrs     Breads    
                                   beans
                                   rice


Better         Class IV  2lbs water to 185 F      4 hrs     Beans
                                   rice


Good      Class V   2 lbs. water to 150 F    5 hrs         For
                              or   purifying
                              more water
4.1 -- Loading Factors: If an oven/cooker can heat 4 lbs. of water to 185 degrees F insttead of just 2 lbs., it should be considered in the class above it.

5.0 -- Conclusion: Each class of oven is appropriate for its loaded condition and the weather/solar adjustments made. The correct usage of a solar oven is entirely up to the person using it, just as a gas or electric oven is.

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