What we are trying to do with the Solar Oven

An advocate for the devil should challenge us with these questions:

• Why are you researching such fully understood technology?
• Why are you building something so small that it can't even cook a hot dog?
• Why are you using such a long, narrow collector?
• What can you hope to contribute to technology of solar cooking?

The theory of compound parabolic collectors is mostly understood.  It was initiated by Roland Winston (and perhaps others simultaneously) in the 70s, I think. We are not in much of a position to improve upon this theory. However, we can improve on the practice.  For example, I don't think very many actual example of 3-d parabolic compound collectors have been created and analyzed.  Certainly Elliot and I have found constructing our box-shaped collector challenging to make, and we have access to computers, a laser cutters, and most of the tools that we might need.  Constructing a revolved surface or an approximation to one is even harder to make.  We are in now in a position to build and test a surface of revolution, although we have no immediate plans to do so.

Along the same lines, one can construct an oven out of mirrors, unpolished aluminum, polished aluminum, and aluminum foil (we have tried all of these!)  but I have not found a resource that actually compares these reflectors from a practical point of view. I hope at least we can contribute to this kind of practical knowledge. I did not go to graduate school for seven years to do such practical engineering, which almost descends to "craft" rather than engineering---but I am not ashamed to contribute it.

We are intentionally attempting to apply Agile Software Methodology to this development.  That is why we are presently collecting one sqare foot (or 100 watts) or solar energy rather than one square meter (or 600 watts, approximately the power of microwave oven.)  If we cannot build an effective oven that conveniently allows one to cook a very small portion of food, we have no business investing in a larger oven that would be have more potential.

We are currently building a long, narrow CPC because we believe that to build a cooker more convenient for the grill master or chef than those previously developed, we need to achieve higher temperatures.  Existing solar cookery tends to fail because it forces a culturally unappealing change in cooking style. Although I personally am fruitarian(ish) and don't often eat barbecue or hot dogs, that is what Americans cook as a social food at the park.  These foods can be made edible with long, slow cooking typical of solar cookers---but not palatable. The culturally preference is for slighty-charred food what is hot to warm at the center.  To make this experience as similar to what it is with charcoal, we need to produce the same food, and we must produce it in about the same amount of time.  This implies that we must inject heat into the food about as fast as being a few inches above a charcoal fire. Therefore the high concentrations offered by non-imaging optics seems like a reasonable approach.

It is possible that a broader CPC, involute, or other design would be better.  However, "long" CPC seems to be a good compromise in that it allows input into an insulated chamber with a relatively small port, which presumably will allow a higher overall temperature, and the ability to perform "grilling" style cooking in which the heat is primarily radiated rather than conducted into the food.

There are several worthy goals that we can accomplish, though none of them would be considered a theoretic advance of optics:

• We can document our experience trying to make good reflectors.
• We can develop approaches to build complex curves out of widely available tools and materials.
• We can attempt to measure an actual instance of a CPC and compare it to the easily calculated theoretical potential.
• We can develop aiming and positioning technology that is broadly applicable.
  
  But personally, I just think it would be a powerful artifact to build even a single device, at whatever expense, that is as convenient to use a charcoal grill that requires no fuel at all.