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Re: Solar Ovens - Dehydrating foods

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

This won't add detail to the description, but I bought a book years ago 
(copyright 1977) put out by Rodale Press called Build It Better 
Yourself.  There is a plan in there for a solar dryer.  Also, I have a 
copy of a plan put out by Sunset Magazine in their August 1976 edition 
that has a plastic-topped collector, compartment with tiers for trays, 
and a chimney to exhaust both heat and moisture.

I have no idea if such old references would now be available in some 
archive.

Barbara Davis       zone 7/8       southwest of Fort Worth, TX


> 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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