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Solar Ovens - Dehydrating foods

Square Foot Gardening List - http://www.flinet.com/~gallus/sqft.html

Earlier I alluded to homemade solar ovens I had recently seen demonstrated
at the "Energy Park" at the Oregon Country Fair. I received requests for
more information. I have tracked down and emailed some contacts for the
information and will share it when/if it arrives. In the meantime let me
explain what I remember about them. They weren't that complicated (at least
it seemed so).

Picture a box, oh about 2 foot square. The top of the box is open and cut
into a slant so that if you face the box to the sun, more light can get in.
This slant is covered by glass. The inside of the box is lined with aluminum
foil. Around the top of the box is a collar, the looks like a squarish
funnel that sits on the top of the box. The funnel does not block the sun,
but rather acts I would assume as a solar collector, and is also lined with
aluminum foil.

The principle I'm sure is to collect as much solar rays as you can and
funnel them into the box. These boxes looked like they were constructed from
plywood and cardboard.

I'm wondering if they can be improved by insulation and using mirrors
instead of aluminum foil?

Inside the box is an ordinary cooking thermometer to monitor the heat. I
don't remember, but I would assume that there was a door in the sides or
that the glass was removeable to allow putting and removing food in/out of
the oven.

Again my recollection is fuzzy but I think that in July I saw them these
ovens were generating heats around + or -300 degrees. I know for a fact I've
seen them at 200+. (I've been to this booth a couple or three years in a
row) and have seen them baking cookies and such

I just sent out an email from the University of Minnesota regarding
dehydrating foods http://www.extension.umn.edu/Documents/D/J/DJ0820.html. It
discusses that sun drying food takes about 3-4 hours and requires a humidity
of less than 20% or the food will mold before drying. Basically you need to
live in Southern California or Arizona, or perhaps just the right summer
months if you don't have high humidity in your area.

(I was talking to a guy in Arizona yesterday that complained the humidity
jumped to 30%, I'd hate to see him at St Louis or New Orleans in July)

I'm curious about the use of a solar oven to dehydrate food. The challenge
would be getting rid of the accumulated moisture without loosing the heat.

Any ideas from our inventor-minded people out there? I've thought about
vents at the top to let the steam escape, but would that be enough? Also
I've thought of a small battery powered, or hand cranked fan, but I'm afraid
that it would blow out to much heat.


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