Help with Solar Oven article by sci

 

The Solar Cookers International has an article (in pdf), "Solar Baking
Under the Sonoran Sun" by Laurie Stone, in which describes the building
of a big solar oven. As the article was written in 1997 I have some
questions about the construction of the oven.

1. I do not think the high temperature for the oven was given and I
would like to know if the solar oven reached 400 degrees or above. If
the solar oven does not reach 400 degrees what could be done in it's
construction so that it would reach the 400 degrees.

2. The article mentions using Everbrite for the reflectors. Are glass
mirrors better for reflectors than the Everbrite. Since 1997 are there
newer materials that would make better reflectors than the Everbrite?

3. The article says that 3/4 inch plywood was used in constructing the
solar oven's frame. Would a higher cooking temperature be obtained if
the frame was built more like a box solar cooker in that one frame
construction is constructed and then another one constructed about 2 or
3 inches bigger than the first one which would sit inside the second
one which is about 2 or 3 inches bigger?

4. The article mentions using PV fans (I think these are solar cells to
run the fans) -"The fans are run by a 6 Volt, 5 Amp module." - if these
are solar cell powered fans information on the types of solar cells to
use and the type of fans. And do you run the fans on all the different
types of meals or just the cookies and pasteries - how about bread

A few questions about cooking with the solar oven described in the
article.

1. Can a 16 inch pizza be cooked with the solar oven?

2. Can frozen foods be cooked with the solar oven such as: frozen pot
pies - like Banquet and other type brands. Frozen TV type dinners.
frozen fish breaded portions - like Gorton's and other types of brands.
Frozen pizzas. Frozen egg rolls. Frozen Boritoes. Frozen fries like
oreda fries.

3. Breads - sence the sun comes in through the glass do you move the
bread after it has cooked for so long so the backside of the bread gets
some sun

Thanks

 

sgotr wrote:

You might do better to direct your questions to Solar Cookers
International. info@solarcookers.org or http://solarcookers.org/

That said, I think I can offer some insight.


I think it's unlikely that the oven reached 400F. It's more likely
that their design would run between 250F to 300F. This is, I assure you,
quite hot enough to bake. It just takes a little longer than at higher
temperatures.


Glass is heavy and prone to breakage, not to mention being rather
expensive. I've used reflective mylar to good success (much better
than aluminum foil) but it does degrade over time and needs to be
replaced every year or so.

This article describes using Anocoil Aluminum sheeting.
http://www.sunspot.org.uk/Prototypes.htm


The article says that they used 3/4 plywood and ductboard insulation
on the inside surface. This insulation is a fiberglass board type that
is used to insulate air ducts in HVAC systems and typically runs around
R6. This is more than enough for a solar oven with an R1 glass cover.

If you want to make it slightly better then you can double pane the
glass cover. Adding a tracker to keep it pointed at the sun will help
a lot as well. Adding more insulation could help but not a huge amount.
Ductboard is pretty cheap though so it's not a major expense.

This fellow has some good ideas on trackers.
http://www.redrok.com/main.htm


Hmm, 6 Volts at 5 amps is a 30 watt solar PV panel. Seems rather
excessive for a simple circulating fan. Either that's a typo or
they're circulating one heck of a lot of air. You can probably
do quite well with a 2 or 3 watt 12V solar PV panel running a couple
computer style muffin fans. Any 12V PV panel would suffice to run
12V DC fans. You might want to find fans that don't produce toxic
smoke when baked and that don't mind the temperatures inside an
oven. I haven't tried baking any DC fans so I can't say how well
they work.

The idea with the fans is that they circulate the air inside the
oven so the temperature is even throughout. This means that parts
of the oven that don't actually have something sitting absorbing
the sunlight are still contributing by heating the air. I would
think it would improve the performance of the cooker for most any
cooking.

You can, of course, use mains power or rechargeable batteries to
run the fans.


Yes, assuming you have a 16 inch (or larger) solar oven that you
can physically fit the 16 inch pizza inside.


Yes. Typically it takes roughly twice as long to cook things in a
solar oven than an ordinary oven due to the solar oven having a
lower temperature.


The entire inside of the oven is at roughly the same temperature,
even more so with circulating fans, so spinning the food isn't
required.

You might find the following links of use.
http://www.solarcooking.org/
http://www.solarcooking.org/plans.htm
http://www.solarcooking.org/docs.htm

Solar cookers, How to make, use and enjoy.
http://www.solarcooking.org/Plans.pdf

Anthony

 



Qualifier - You'll probably find that thin crust and regular crust
pizza will be unacceptably soggy unless the crust was pre-baked, and
that the cheese will not brown.  It'll be edible, but not much more.

Some of the best pizzas are cooked at above 400 degrees F. to give the
outer layer of the crust a distinct crispness.  Many foods benefit
from slower cooking.  Pizza isn't one of them.

I did see one design for a solar oven that focused the light on the
bottom of the oven, allowing good insulation where it counts.  An oven
like that, with a flat cooking stone inside to provide thermal mass,
might do a decent job at cooking a pizza, but as I recall the oven had
to be constantly moved to track the sun.

 ï