Self Reliance Handout #5- Solar Ovens

It is important to have food stored in case of emergencies, but it is just as important to have a plan for how to cook that food in the same emergencies. Even if some of us have a way to cook food in a short term emergency such as a Propane Grill, Coleman Stove or perhaps an indoor wood burning fireplace, those are not realistic long term strategies. Solar Ovens can be a long term solution that uses the heat from the sun to cook food similar to a crock-pot; lower temperatures for a longer time. It is free, safe, healthy, it won’t burn the food so you can leave it in the morning and your food will be cooked by the afternoon while you have other chores to attend to.

What is a Solar Oven?
A solar oven uses the heat of the sun much like the inside of a car with the sun shining thru the windows. The sunshine is reflected inside a trapped container that cannot let the heat back out, even on a cold day, just as the interior of a car can heat up quickly even in winter. A solar oven requires a reflective surface that is focused on a blackened pan or cooking container. The container is enclosed inside something to keep the air that is heated trapped; it can be a plastic bag or a clear Pyrex bowl with a lid. It can be used to cook food, or to boil water for pasteurization. How hot it can get inside the oven dependends on the number of reflectors, the sun’s intensity and it’s duration.

When and why did solar cooking start?
People have probably used the sun in some format to heat or cook foods since the beginning. Solar Cooking actually has some early recorded beginnings with the documented efforts of French-Swiss Physicist Horace de Saussure in 1767. In the last 30 years, it has resurfaced as a way to help people in developing countries cook their food.
“The burden for gathering the fuel wood and cooking falls mainly on women and children. Joseph Kiai reports from Dadaab, Kenya: "Women who can't afford to buy wood start at 4 am to go collecting and return about noon... They do this twice a week to get fuel for cooking... The rapes are averaging one per week." From Belize: "Many times the women have to go into the forest dragging their small children when they go to look for wood. It is a special hardship for pregnant and nursing mothers to chop and drag trees back to the village... they are exposed to venomous snakes and clouds of mosquitoes." (Anna K.) (Quoted in newsletters by Solar Cookers International.)”
“And the forests are dwindling in many areas. Edwin Dobbs noted in Audubon Magazine, Nov. 1992, "The world can choose sunlight or further deforestation, solar cooking or widespread starvation..."
“Americans should be prepared for emergencies, incident to power failures. A Mormon pioneer noted in her journal: "We were now following in their trail traveling up the Platte River. Timber was sometimes very scarce and hard to get. We managed to do our cooking with what little we could gather up..." (Eliza R. Snow) quoted from http://www.solarcooking.org/plans/funnel.htm retrieved June 23, 2009
These same reasons to use Solar Cooking can apply to us:
Safety from danger when trying to gather wood
Better health from not inhaling fumes and smoke on a daily basis
Not having to spend limited financial or time resources on wood if that becomes required.
Easy to start meals and leave them safely while other chores are completed- no danger from unattended fires.

What types of Solar Ovens are there and how much do they cost?
There are many solar ovens that can be purchased and cost from $60 to over $400. The advantages to these manufactured ovens are that they are much more durable, can get wet, can travel easily and many of these fold up into a box, and the results are more consistent. The generally reach a higher internal cooking temperature, though any dish with water will not get above boiling temperature no matter how high the reflected temperature gets.

The greatest disadvantage of course is the cost.

But the good news is that is is easy to make your own solar Oven from materials most of us have or have access to. There are many different patterns that can be used to make your own solar Oven and can be found at this website: http://solarcooking.org/plans/

They fall into 3 basic styles: Panel, Parabolic and Box and each has its own advantages and disadvantages. The Instructions below are from a modification of a panel style created by BYU Professor Dr Stephen Jones. But another popular and easy to make style is a box oven which is just like it sounds. Instructions for that plan are all given at the above website.
How to Build Your Own Solar Funnel Cooker
What You will Need for the Funnel Cooker:
1. A piece of flat cardboard, about 2 feet wide by 4 feet long. (The length should be just twice the width. The bigger, the better.)
2. Ordinary aluminum foil. (I prefer the Heavy Duty so it lasts longer- RL)
3. A glue such as white glue (like Elmer's glue), and water to mix with it 50-50.( I have found that is too thin, I use more like 25% water- RL) Also, a brush to apply the glue to the cardboard (or a cloth or paper towel will do). Or, some may wish to use a cheap "spray adhesive" available in spray cans. You can also use wheat paste.
4. Three wire brads-- or small nuts and bolts, or string to hold the funnel together.
5. For a cooking vessel, I recommend a canning jar ("Ball" wide-mouth quart jars work fine for me; the rubber ring on the lid is less likely to melt than for other jars I've found. A two-quart canning jar is available and works fine for larger quantities of food, although the cooking is somewhat slower.).
6. The cooking jar (or vessel) should be spray-painted black on the outside. I find that a cheap flat-black spray paint works just fine. Scrape off a vertical stripe so that you have a clear glass "window" to look into the vessel, to check the food or water for boiling. (I have placed Scotch tape and then pulled it off after the paint dries works just as well- RL)
7. Dr Jones originally had used a block of wood on the bottom, but in more recent versions, a rack, trivet or small Pyrex 8x8 turned upside down allows even more reflection on the bottom of the pan- RL
8. A plastic bag is used to go around the cooking-jar, to provide a green-house effect. Suggestions:
• Reynolds™ Oven Bag, Regular Size works great: transparent and won't melt. (Cost about 25 cents each in U.S. grocery stores.)
• Any nearly-transparent HDPE bag (High-density Polyethylene). Look for "HDPE" stamped on the bag. I've tested HDPE bags which I picked up for free at my grocery store, used for holding vegetables and fruits. These are thin, but very inexpensive. Tested side-by-side with an oven bag in two solar funnels, the HDPE bag worked just as well! (Caution: we have found that some HDPE bags will melt should they contact the hot cooking vessel. For this reason, we recommend using the oven-safe plastic bag wherever possible.)
• An idea attributed to Roger Bernard and applied now to the BYU Funnel Cooker: place a pot (having a blackened bottom and sides) in a glass bowl, and cover with a lid. Try for a tight fit around the bottom to keep hot air trapped inside. The metal pot or bowl should be supported around the rim only, with an air space all around the bottom (where the sunlight strikes it). Put a blackened lid on top of the pot. Then simply place this pot-in-bowl down in the bottom of the funnel - no plastic bag is needed! This clever method also allows the cook to simply remove the lid to check the food and to stir. I like this idea - it makes the solar cooker a lot like cooking over a fire. See Photographs for further details. (The thinner plastic bags tend to melt on the cooking pan, but you can build a small wire frame around the pan that holds the plastic bag away from the pan so that he bag can be reused many times- RL
Construction Steps
#1 Cut a Half-circle out of the Cardboard
Cut a half circle out of the cardboard, along the bottom as shown below. When the funnel is formed, this becomes a full-circle and should be wide enough to go around your cooking pot. So for a 7" diameter cooking pot, the radius of the half-circle is 7". For a quart canning jar such as I use, I cut a 5" radius half-circle out of the cardboard. ( I have cut a 10 inch circle for our demonstration model-it is easier to fold RL)

#2 Form the Funnel
To form the funnel, you will bring side A towards side B, as shown in the figure. The aluminum foil must go on the INSIDE of the funnel. Do this slowly, helping the cardboard to the shape of a funnel by using one hand to form creases that radiate out from the half-circle. Work your way around the funnel, bending it in stages to form the funnel shape, until the two sides overlap and the half-circle forms a complete circle. The aluminum foil will go on the INSIDE of funnel. Open the funnel and lay it flat, "inside up", in preparation for the next step.

#3 Glue Foil to Cardboard
Apply glue or adhesive to the top (inner) surface of the cardboard, then quickly apply the aluminum foil on top of the glue, to affix the foil to the cardboard. Make sure the shiniest side of the foil is on top, since this becomes your reflective surface in the Funnel. I like to put just enough glue for one width of foil, so that the glue stays moist while the foil is applied. I also overlap strips of foil by about 1" ( or 2 cm). Try to smooth out the aluminum foil as much as you reasonably can, but small wrinkles won't make much difference. (If even cardboard is not available, one can simply dig a funnel-shaped hole in the ground and line it with a reflector, to make a fixed solar cooker for use at mid-day.)

#4 Join side A to side B to keep the funnel together.
The easiest way to do this is to punch three holes in the cardboard that line up on side A and side B (see figure). Then put a metal brad through each hole and fasten by pulling apart the metal tines. Or you can use a nut-and-bolt to secure the two sides (A & B) together.
Be creative here with what you have available. For example, by putting two holes about a thumb-width apart, you can put a string, twine, small rope, wire or twist-tie in one hole and out the other, and tie together.
When A and B are connected together, you will have a "funnel with two wings". The wings could be cut off, but these help to gather more sunlight, so I leave them on.
Tape or glue a piece of aluminum foil across the hole at the bottom of the funnel, with shiny side in. (I have placed a heavy slat stone on mine covered with foil to weight down the oven so it doesn’t blow away!-RL)
This completes assembly of your solar funnel cooker.
For stability, place the Funnel inside a cardboard or other box to provide support. For long-term applications, one may wish to dig a hole in the ground to hold the Funnel against strong winds.




Final Steps
At this stage, you are ready to put food items or water into the cooking vessel or jar, and put the lid on securely. (See instructions on food cooking times, to follow.) (Remember this shows a piece of wood as the base- you can do this but a clear Pryex 8x8 holds the pan up and allows reflection to go on below-RL)
Next, gather the top of the bag in your fingers and blow ai
r into the bag, to inflate it. This will form a small "greenhouse"
around the cooking vessel, to trap much of the heat inside.
Close off the bag with a tight twist tie or wire. Important: the
bag should not touch the sides or lid of the cooking vessel.
The bag may be called a "convection shield," slowing
convection-cooling due to air currents. Place the entire bag
and its contents inside the funnel near the bottom as shown
in the Photographs.





Place the Solar Funnel Cooker so that it Faces the Sun
Remember: Sunlight can hurt the eyes: Please wear sunglasses when using a Solar Cooker! The Funnel Cooker is designed so that the hot region is deep down inside the funnel, out of harm's way.
Put the Solar Funnel Cooker in the sun pointing towards the sun, so that it captures as much sunlight as possible. The design of the funnel allows it to collect solar energy for about an hour without needing to be re-positioned. For longer cooking times, readjust the position of the funnel to follow the sun's path.
It helps to put the Solar Funnel Cooker in front of a south-facing wall or window (in the Northern Hemisphere) to reflect additional sunlight into the funnel. A reflective wall is most important in locations farther from the equator and in winter. In the Southern Hemisphere, put the Solar Funnel Cooker in front of a North-facing wall or window to reflect additional sunlight into your cooker.
After Cooking
Remember that the cooking vessel will be very hot: Use cooking pads or gloves when handling! If you are heating water in a canning jar, you may notice that the water is boiling when the lid is first removed - it gets very hot!
Open the plastic cooking bag by removing the twist-tie. Using gloves or a thick cloth, lift the vessel out of the bag and place it on the ground or table. Carefully open the vessel and check the food, to make sure it has finished cooking. Let the hot food cool before eating.
Helpful Hints
1. Avoid leaving fingerprints and smudges on the inside surface of the cooker. Keep the inner surface clean and shiny by wiping occasionally with a wet towel. This will keep the Solar Funnel Cooker working at its best.
2. If your funnel gets out-of-round, it can be put back into a circular shape by attaching a rope or string between opposite sides which need to be brought closer together.
3. For long-term applications, a hole in the ground will hold the Funnel Cooker securely against winds. Bring the funnel inside or cover it during rain storms.
4. The lids can be used over and over. We have had some trouble with the rubber on some new canning-jar lids becoming soft and "sticky." "Ball canning lids" do not usually have this problem. Running new lids through very hot water before the first use seems to help. The lids can be used over and over if they are not bent too badly when opened (pry off lid carefully).
5. The jar can be suspended near the bottom of the funnel using fishing line or string (etc.), instead of placing the jar on a block of wood. A plastic bag is placed around the jar with air puffed inside, as usual, to trap the heat. The suspension method allows sunlight to strike all surfaces of the jar, all around, so that heats faster and more evenly. This suspension method is crucial for use in winter months. (or as previously mentioned, use a trivet, a rack or a clear dish to support it underneath- RL)
6. Adjust the funnel to put as much sunlight onto the cooking jar as possible. Look at the jar to check where the sunlight is hitting, and to be sure the bottom is not in the shadows. For long cooking times (over about an hour), readjust the position of the funnel to follow the sun's path. During winter months, when the sun is low on the horizon (e.g., in North America), it is helpful to lay the funnel on its side, facing the sun.
7. Vegetables (Potatoes, carrots, squash, beets, asparagus, etc.)
Preparation: No need to add water if fresh. Cut into slices or "logs" to ensure uniform cooking. Corn will cook fine with or without the cob.
Cooking Time: About 1.5 hours
8. Cereals and Grains (Rice, wheat, barley, oats, millet, etc.)
Preparation: Mix 2 parts water to every 1 part grain. Amount may vary according to individual taste. Let soak for a few hours for faster cooking. To ensure uniform cooking, shake jar after 50 minutes. CAUTION: Jar will be hot. Use gloves or cooking pads.
Cooking Time: 1.5-2 hours
9. Pasta and Dehydrated Soups
Preparation: First heat water to near boiling (50-70 minutes). Then add the pasta or soup mix. Stir or shake, and cook 15 additional minutes.
Cooking Time: 65-85 minutes
10. Beans
Preparation: Let tough or dry beans soak overnight. Place in cooking jar with water.
Cooking Time: 2-3 hours
11. Eggs
Preparation: No need to add water. Note: If cooked too long, egg whites may darken, but taste remains the same.
Cooking Time: 1-1.5 hours, depending on desired yolk firmness.
12. Meats (Chicken, beef, and fish)
Preparation: No need to add water. Longer cooking makes the meat more tender.
Cooking Time: Chicken: 1.5 hours cut up or 2.5 hours whole; Beef: 1.5 hours cut up or 2.5-3 hours for larger cuts; Fish: 1-1.5 hours
13. Baking
Preparation: Times vary based on amount of dough.
Cooking Times: Breads: 1-1.5 hours; Biscuits: 1-1.5 hours; Cookies: 1 hour
14. Roasted Nuts (Peanuts, almonds, pumpkin seed, etc.)
Preparation: Place in jar. A little vegetable oil may be added if desired.
Cooking Time: About 1.5 hours
15. MRE's and prepackaged foods
Preparation: For foods in dark containers, simply place the container in the cooking bag in place of the black cooking jar.
Cooking Times: Cooking time varies with the amount of food and darkness of package.



Basic tips to for success:
 Dark colored, thin metal pots ( On days that are cloudy, a cast iron pan as in a Dutch oven style may work better as it holds the heat longer, though it is slower to warm up)
 Any pan can work if it is dark and can fit in the size of solar oven you are using. You can use black flat spray paint if you find a pan with a tight fitting lid but it is too shiny
 There are several ways to trap the heated air around the pan: an oven bag, a clear plastic bag as the type bread comes in though it will melt eventually, a clear Pyrex bowl with lid that encases the cooking pan, or find a way to cover your oven tightly with a glass or Plexiglas cover. This works well with the box style solar ovens.
 Something to rest the cooking pan on that allows reflective rays to reach the bottom of the pan
 Keeping the reflective surface unsmudged. Wrinkles don’t mater, but glue residue or dirt, or finger prints eventually lessen the effectiveness of the foil
 We live in an area that has sudden windstorms. It is a good idea to plan for ways to weigh down the funnel and bucket if that is the style of solar Oven you are using
 In order to keep the costs as low as possible, look thru your own things to see what you can adapt to use for this. You can also try thrift shops or garage sales to limit the cost of cooking pans in you don’t have anything that will work- be creative.

Recipes:
*As a general rule, any crock pot recipe will work in a solar oven
*If cooking meat, additional water is not required as this is a high humidity type of cooking
*You can cook breads, rolls, cakes, biscuits and cookies, as they will brown. You will have to check for
doneness as each oven and each day can vary the amount of time required
*A thermometer helps to determine how fast the food is cooking.


Easy French Bread
1 package yeast
2 cups water
4 1/2 cups white flour
1 tablespoon sugar
2 teaspoons salt
Dissolve yeast in one cup lukewarm water. Sift flour with sugar and salt into a large bowl. Stir in dissolved yeast. Add just enough of the second cup of water to hold dough together. Mix until dough is sticky. Cover with a cloth and let rise until doubled. Butter or grease a round roaster and add dough to dark pan. Let rise another half hour. Cover. Bake in solar oven until golden
brown, about 2 hours.


Foolproof Whole Wheat Bread
2 tablespoons dry yeast
5 cups hot water
2/3 cup oil
12 cups whole wheat flour (or 7 cups whole wheat flour & 5 cups white flour)
1/2 cup warm water
2 tablespoons salt
2/3 cup honey or sugar

Sprinkle yeast into 1/2 cup warm water. Let stand 10-15 minutes. Add 1 tablespoon sugar. Combine the


remaining 4 1/2 cups hot water with 7 cups whole wheat flour in a large bowl. Add salt, oil and honey or sugar. Continue mixing until well blended. Add 1 cup flour to mixture. Add prepared yeast to mixture and blend thoroughly. Add 3 to 4 more cups of flour. Knead for 10 minutes or until there is a consistency like cookie dough. A stickier dough will result in moister bread. Oil hands and divide dough into 4 parts. Mold into loaves on oiled counter. Place in oiled pans. Oil top of loaves if soft crust is desired. Cover loaves with damp cloth and let rise 1/3 in bulk. Place loaf pans in dark pans with lids, or insert an empty loaf pan on top of each loaf of dough. Cover. Place in solar oven by 11 a.m. Cook 2 1/2 hours.






Links
http://www.youtube.com/watch?v=qZzUfPcEQMg shows cooking in a solar oven in 9 degree temperatures in Minnesota in January
http://www.solarcooking.org/plans/funnel.htm Dr Stephen Jones from BYU- with directions for funnel cooker

Windshield Shade Solar Funnel Cooker


Materials needed:
 A reflective accordion-folding car sunshade (abt $5-6)
 A Cake rack (or wire frame or grill)
 12 cm. (4 ½ in.) of Velcro
 Black pot
 Bucket or plastic wastebasket
 plastic baking bag
1. Lay the sunshade out with the notched side toward you, as above.
2. Cut the Velcro into three pieces, each about 4 cm. or 1 ½ inches long.
3. Hand sew one half of each piece, evenly spaced, onto the edge to the left of the notch; sew the matching half of each piece onto the underneath size to the right of the notch, so that they fit together when the two sides are brought together to form a funnel. (see below) Note: I first tried sewing these on a sewing machine, but found it cut through the reflective material.
4. Press the Velcro pieces together, and set the funnel on top of a bucket or a round or rectangular plastic wastebasket.
5. Place a black pot on top of a square cake rack, placed inside a plastic baking bag. A standard size rack in the U.S. is 25 cm. (10 in.). This is placed inside the funnel, so that the rack rests on the top edges of the bucket or wastebasket. Since the sunshade material is soft and flexible, the rack is necessary to support the pot. It also allows the suns rays to shine down under the pot and reflect on all sides. If such a rack is not available, a wire frame could be made to work as well. Note: the flexible material will squash down around the sides of the rack.
The funnel can be tilted in the direction of the sun. A stick placed across
from one side of the funnel to the other helps to stabilize it in windy
weather. (see below) After cooking, simply fold up your “oven” and slip the
elastic bands in place for easy travel or storage. This totally simple solar
oven is extremely practical, as it is so lightweight and easy to carry along
anywhere. But in addition, it has reached a higher temperature in a shorter time than all the other models the creator experimented with so far - a little above 350 degrees Fit has been used to cook black beans in about the same amount of time as on a gas stove; It has been used it to bake breads, granola, brownies, lasagna, all sorts of vegetables, and to purify water.