Solar Cooking Ovens
Solar ovens can come in handy if there is a disaster of sorts that
your electricity is been severed off and your oven isn't working any more
or maybe you have been forced to leave your home and wouldn't have
sources for fuel to cook. Having a solar oven would come very handy for your
emergency preparedness. Many poorer countries in the world use
solar cookers for cooking and have benefited from them greatly.
Especially when lacking other fuel resources.
There are many types of solar ovens that can be purchased or made
depending on your finances or ambition to have one made. There are
many sites online with free plans in making solar ovens or if you just
want to purchase one, there are sites also available to do so.
There are three common solar ovens that are made and used:
Box Cookers These are great
for cooking large amounts of food being that they cook more slow and
evenly. Many differ in making of the slanting the face toward the
sun and the number of reflectors they have. You can figure that food in a
single-reflector box cooker will take about twice as long as in a
conventional oven . However, since you can't really burn your food, you
don't have to watch the cooker or stir any food as it cooks. You can just
put in a few pots with different foods and then come back later in the
day and each pot will cook to perfection and then stay hot until you take
Panel Cookers It is made with
various flat panels concentrate the sun's rays onto a pot inside a
plastic bag or under a glass bowl. The advantage of one of these is that
they can be built in an hour or so for very little. Panel cookers cook
smaller portions, usually only in a single pot, but often they cook
slightly faster. Some people have reported the need to stir food every
once in a while when using this kind of cooker to assure that the food
heats evenly. In Kenya, these are being manufactured for the Kakuma
Refugee Camp for very little.
Parabolic Cookers These ovens
usually made having a concave disks that focus the light onto
the bottom of a pot. They cook foods about as fast as on a conventional
stove. Since the concentrated sunlight shines directly on the bottom of a
pot, the pot heats up and cooks very quickly. The food will burn though,
so you have to stir it and watch it carefully. The disadvantage is that
they are quite complex to make and you have to constantly follow the sun
to keep a good focus. They will cause burns and eye injury if not
Here are some useful information to keep in mind when building or using solar
1. The temperature reached by box cookers and panel cookers depends
primarily on the number and size of the reflectors used. A single-reflector
box cooker usually tops out at around 150E° C
(300E° F) as the food approaches being done.
High temperatures, however, are not needed for cooking. Your oven will cook
just fine as long as it gets up to about 90E°
C (200E° F) or so. Higher temperatures cook
larger quantities, cook faster, and allow for cooking on marginal days;
However, many people prefer to cook at lower temperatures, since then they
can leave the food to cook while they go about their business. With a
single-reflector box cooker, once the food is cooked, it just stays warm
and doesn't scorch. It's good to keep in mind that no food can go above 100E°
C (212E° F) at sea level anyway, unless a
pressurized cooking vessel is used. The high temperatures you see in
cookbooks for conventional ovens are just for convenience and for special
effects such as quick browning.
2. As far as having the cookers face the sun the box cookers with one back
reflector don't need to be turned unless you are cooking beans which take
up to 5 hours. Panel cookers need to be turned more often than box cookers,
since they have side reflectors that can shade the pot. Parabolic cookers
are the most difficult to keep in focus. These need to be turned every 10
to 30 minutes, depending on the focal length.
4. Building a box cooker out of plywood or glass works great unless you
need a cooker that can stay outside even in the rain, you'll do just fine
with a cardboard cooker. Cardboard is much easier to work with and holds
heat just as well. Some people have used the same cardboard box cooker for
over 10 years.
5. Using mirrors are more reflective than simpler materials such as
aluminum foil, but the added reflectiveness is probably not worth the
increased cost and fragility involved with using mirrors.
6. Some people prefer to paint the walls black thinking that the oven will
get hotter. It seems, however, that the walls will get hotter, but the food
won't necessarily get hotter. Its more preferable to cover the inner walls
with aluminum foil to keep the light bouncing until it hits either the dark
pot or the dark bottom tray. Since the bottom tray is in contact with the
pot, the heat the tray collects will move into the pot easily. You can buy
flat-black spray paint that says "non-toxic when dry" on the label but
otherwise, black tempera paint works, but you have to be careful not to
wash it off when you wash the pot.
7. The best kind of pot to use are dark, light-weight, shallow pot that is
slightly larger than the food you will cook in it. Metal pans seem to cook
best. Hardware stores in the US usually carry dark, speckled, metal pans
called Graniteware. Shiny aluminum pots--so common in developing
countries--can be painted black or can be blackened in a fire. Cast iron
pots will work, but extra solar energy is used to heat up the pot as well
as the food, so they will not work in marginal conditions.
8. For insulating the walls of a box cooker, fiberglass or Styrofoam is
usually not recommended since they give off ill-smelling gases as they heat
up. Natural substances such as cotton, wool, feathers, or even crumpled
newspapers work well. Many people, however, leave the walls empty of any
stuffing, preferring instead to place a piece of foiled cardboard as a
baffle inside the wall airspace. This makes a lighter cooker and seems to
be adequate. Most of the heat loss in a box cooker is through the glass or
plastic, not through the walls. This is why a few percentage points of
efficiency here or there in the walls doesn't effect the overall
temperature and cooking power that much.
9. All three types, water can be brought to a boil. A little-known fact,
however, is that to make water safe to drink, it only has to be
pasteurized, not sterilized. Pasteurization takes place at 65E°
C (150E° F) in only 20 minutes. This treatment
kills all human disease pathogens, but doesn't waste the energy needed to
bring the water to a boil. One reason that people are told to boil their
water is that thermometers are not readily available in many places and the
boiling action serves as the temperature indicator
10. If wanting to use the solar box for canning
it's best to only can fruit. Vegetables or meats need to be canned
11. You can cook pasta in a solar box cooker but
use two separate pans to keep the pasta from getting pasty. Heat the
dry pasta with oil in one pan; heat the liquid with herbs in another.
Fifteen to 20 minutes before eating, combine the two. If you are going to
use a sauce, heat that in a third container.
12. Building or using a box cooker out of
cardboard works fine and won't catch fire. Paper burns at 451E° F (233E°
C) so your cooker won't get hot enough to burn.
13. Depending on where you live will depend when
you can cook. In tropical regions and in the southern US you can cook
all year depending on the weather. In areas as far north as Canada you can
cook whenever it is clear except during the three coldest months of the
14. You have a lot of different items you can cook
with the cooker and a good first food to try is a small quantity of rice, since it is fairly
easy to cook and looks very different cooked than it does raw.
Chicken or fish is also very easy to cook.
15. If your cooker gets only up somewhere around 250E°
F (121E° C) and your recipe calls for 350E°F (177E°
C) or even 450E° F (232E°
C) you will still be able to cook. A temperature of 250E° F (121E°
C) is plenty hot enough for all kinds of cooking. Remember that water cannot get
hotter than 212E° F (100E°
C). Thus if you are cooking food that contains water, it cannot get hotter
than this either. Conventional cookbooks call for high temperatures to
shorten the cooking time and for browning. Food just takes longer in most
solar cookers, but since the sun is shining directly on the lid of the pot,
the food browns just about as well as in a conventional oven.
16. If the sun
goes in front of the clouds while I'm cooking
your food will continue to cook as long as you have 20 minutes of
sun an hour (using a box cooker). It is not recommended that you cook meats
unattended when there is a possibility of substantial cloudiness. If you can be sure that the sky will stay
clear though, you can put in any type of food in the morning, face the oven
to the south, and the food will be cooked when you get home at the end of