Solar Cooking and Drying Handout - Workshops 2010

Solar Cooking and Drying Worskhop

Presented by Julie Nelson and Jonathan Krausert


Why Cook or Dry Food with the Sun

  •  The sun shines everyday and is accessible to everyone!

  • Sun energy is free; no gas/electricity costs

  • Cookers are easy to transport, adjust and use

  • Won’t burn your food

  • Helps you, your family, other people and the planet

  • Solar cookers can be built from everyday materials or purchased ready-made

  • Solar cookers are easily transported to remote locations and used worldwide to help people save time and resources (lessens deforestation, conserves fossil fuels, purifies drinking water & reduces greenhouse gas emissions)

Many ask, how effective are solar cookers? The effectiveness of a solar cooker or dehydrator can vary depending on what materials are used, how well they are crafted, and what type of climate you live in.


Solar Cooking Principles

  • Concentrating sunlight + converting light to heat + trapping heat=successfully cooking food with the sun

  • Cooking may take longer is there are fog, clouds, wind or shadow.

  • Avoid shiny cooking vessels that reflect light—the darker the better.  Pyrex dishes are ok too.

  • Dutch ovens work well if you’ve got one small enough

  • Don’t cover dish with aluminum foil!


Solar Oven Tips

  • Treat like a slow cooker – during the summer, if I’m making a casserole-type dish for dinner I generally have it in the solar oven by 2 pm.  It starts out fairly hot, but cooks more slowly as the sun lowers in the sky.  It stays warm enough to be safe even if we don’t eat until 7 pm.

  • Baking is better done midday between 11 am and 2 pm.

  • Orient your cooker towards the sun; you should see sunlight reflected in the center of the cooker.

  • Tilt up or down during earlier morning and later afternoon times to capture more sunlight.

General Solar Cooker Types
Box Cookers –well insulated box-within-a-box with a glazed top and hinged lid that reflects sun into box.  Cheap to build, widely used.


Panel Cookers – reflective panel that directs sunshine onto a dark-colored cooking pot enclosed in a clear insulating shell such as a plastic high-temperature cooking bag or an inverted bowl.


High Temperature Cooker– typically a parabolic mirror which focuses sunlight on a cooking vessel.  Cooking time with a parabolic cooker is similar to a conventional stove, and a box oven is similar to a conventional oven.


Julie and Jonathan’s solar oven (Sun Oven) is a cross between a panel cooker and a box cooker.  It is quite efficient; during the middle of a sunny day the oven temperature easily reaches 400 degrees F allowing us to bake bread, pizza, cookies, etc.


Whatever type of solar cooker you have it’s important that it reaches a minimum temperature of at least 180 degrees F.


*Note: Water boils in SLC at about 204 degrees F, not 212 degrees


Easy to Cook Foods (1-2 Hours)

Fish, chicken, egg-and-cheese dishes, white rice, fruit, above ground vegetables.

Moderately Hard to Cook Foods (3-4 Hours)

Bread, brown rice, root vegetables, lentils, most meat

Hardest to Cook Foods (5-8 Hours)

Large roasts, soups and stews, most dried beans


Some of Julie’s Recipes

Really, anything you would cook in a crock pot (or casserole cooked in the oven) works great in your solar cooker.  Here are some general recipes that I frequently make in our solar oven.


Late Summer Veggie Casserole

Quantities depend on what you have in your garden and the size of your casserole.  I generally use an oval Le Creuset cast iron dutch oven.


Summer Squash

Peppers (hot or sweet—depending on what you have and your taste for heat)




Herbs (thyme, parsley, oregano, basil—whatever you have, but go light on rosemary)

Olive oil



Slice the veggies.  Salt the eggplant, squash and tomatoes and let sit for about ½ hour.  Press dry.  Lightly oil cooking vessel.  Then layer everything, distributing onion, garlic and herbs fairly evenly.  Pour a little olive oil between each layer.  When ready to eat this is great on couscous.

Chicken Enchiladas

Half a chicken breast or a couple of thighs

6 to 8 tomatillos, depending on size

a small onion, cut into chunks

2-3 jalapenos (any small hot pepper) in chunks, with or without seeds

1-2 anaheim or poblano peppers (any large sweet pepper), seeded and chunked

2-3 cloves garlic

1 –2 teaspoons ground cumin

fresh or dried oregano to taste

salt to taste

chopped cilantro (add after cooking chicken and sauce)


Place all of the above in large saucepan.  Add water just to cover and simmer until chicken is cooked – about 20 minutes.  Remove chicken.  Puree the veggies with a handful of chopped cilantro and return to pot.  Taste for seasoning.  If not thick, cook down to thicken.


Shred chicken.  Add cooked beans, corn, chopped onions/green onions, more cilantro, shredded cheese, chopped greens (whatever you’ve got, but spinach is good) and some of the green sauce.  Heat corn tortillas to soften, then dip in sauce. Roll up filling or layer like lasagne.  Pour over rest of sauce and cover with more shredded cheese.  (I use an 8/10 pyrex dish for these)  Bake it all afternoon in your solar oven and enjoy your enchiladas with a big salad after the sun goes down!


Tip:  I freeze my tomatillos.  Just remove husk, rinse well and dry.  Put in freezer bag and freeze.  No need to blanch.  To use, just toss them in—no need to thaw.


Another Tip:  I also freeze Anaheims and Poblanos.  Roast them on grill or gas flame until blackened.  Place on tray and freeze.  Once frozen, just place in freezer bag—then you can remove what you need easily.  Once frozen the black skin comes off very easily without rinsing.


Honey Zucchini Bread

1 egg

3/4 cup honey

3 Tablespoons vegetable oil

1 teaspoon vanilla

2-1/2 cups all-purpose flour (can use ½ whole wheat flour)

1-1/2 teaspoons baking powder

1 teaspoon grated orange or lemon peel

1/2 teaspoon baking soda

1/2 teaspoon ground ginger

1/4 teaspoon salt

1-1/2 cups zucchini, grated

1/2 cup sunflower seeds, or any nut you have on hand.


Set up your solar oven to preheat while you mix bread.  You should bake this bread between 11 am and 2 pm on a sunny day.


Beat egg slightly in large bowl. Add honey, oil and vanilla; mix well. Combine flour, baking powder, orange peel, baking soda, ginger and salt in medium bowl. Add flour mixture, zucchini and sunflower seeds to honey mixture; mix until well blended. Spoon batter into well greased 9x5x3-inch dark loaf pan. Bake at 325°F about 1 hour or until wooden pick inserted near center comes out clean. (Probably will take about 2 hours, depending on efficiency oven.  Cool 10 minutes in pan; remove from pan and cool completely.


Honey Banana Bread

1/2 cup of honey 

1/3 cup butter or margarine

1 teaspoon vanilla

2 eggs

1/2 cup all-purpose flour

3/4 cup whole wheat flour

1/2 cup quick-cooking oats

1 teaspoon baking powder

1/2 teaspoon salt

1 teaspoon ground nutmeg


Cream honey and butter in large bowl with electric mixer until fluffy.  Beat in vanilla.  Add eggs, one at a time, beating well after each addition.  Combine dry ingredients in small bowl; add to honey mixture alternately with bananas, blending well.  Stir in walnuts.  Spoon batter into greased and floured 9x5x3-inch loaf pan.  Bake in preheated 325 degree oven 50 to 55 minutes or until a wooden toothpick inserted near center comes out clean.  Cool in pan on a wire rack 15 minutes.  Remove from pan; cool completely on a wire rack.


Solar Drying

Many years ago, we were given an electric food dryer as a wedding present.  We used for a few years, making raisins, dried tomatoes, etc.  It took days for the food to dr and probably used as much power as a hair dryer.  We finally tossed it.  Then we tried a hanging, screened dryer.  This took a long time too, but at least it wasn’t making the power meter whirl!  Finally, Jonathan built a solar dryer.  It is faster, which translates into better quality.

Complete instructions for building a good solar food dryer can be found in The Solar Food Dryer, by Eben Fodor.


Tips from "The Solar Food Dryer"

  •  Always start with the freshest, highest quality foods possible.  Your dried food will only be as good as what you start with.

  • Use fruit and vegetables that are fully ripe, but not overripe.  Drying will lock in the prime flavor of foods at their peak.  But it is not for salvaging expired foods.

  •  Skip all blanching and pre-treating of foods.  Do not soak or rinse fresh foods once they have been sliced, to avoid leaching nutrients into the rinse water.

  • Put fruits and vegetables into your dryer as soon as they are processed (washed and sliced to even thickness of ¼ inch).  They should be drying within ten minutes of slicing.  (While you wouldn’t slice grapes, be sure to cut skins to speed drying.)

  • Make sure that the dryer is powered up with plenty of sunshine so that your foods will start drying right away.  This may mean waiting until 9:00 or 10:00 in the morning when the sun is a little higher in the sky.  Getting off to a quick start with your drying will yield the best flavor and appearance in the end.


Peel, core and slice about ¼ inch.  An old-fashioned peeler/corer works really well.


Cut in half and pit.


Peel, core and slice.


Pit—we use cherry pitter.  Dry until leathery, like raisins


Cut skin to speed drying—use only seedless


Slice ¼ inch – or halve small ones.  Can dry until leathery or crisp.  I like leathery, packed in olive oil.


Shred or slice ¼ inch


Chop fairly fine

Note:  “If you have a wet food like tomatoes or pears, you need to make significant drying progress on the first day of drying.  If you get the food at least half dry the first day, it will survive the night with little problem.  Once the drying process starts, it automatically begins preserving and stabilizing the food.  However, if the food is started late in the day, or clouds come by, the food will still be fairly wet and the overnight stay will cause some degradation.” P. 86


After drying, place food in sealed container and leave on counter for 2-3 days to allow dryness to equalize.  Store in airtight containers in a cool dry place.


Recipes from "The Solar Food Dryer"

Solar-Dried Tomato Pesto

2 cups dried tomatoes

1 cup walnuts

¾ cup olive oil

1/3 cup grated parmesan

5 cloves garlic

2 tablespoons red wine vinegar

1 tablespoon water

½ teaspoon salt

Process in food processor until thick, but fairly smooth.


Zucchini Bread

½ cup dried zucchini – finely chopped or shredded

2 ½ cup whole wheat flour

½ cup chopped walnuts

1 cup chopped dried fruit – whatever you have!

1 ½ teaspoons baking powder

1 teaspoons baking soda

1 teaspoon cinnamon

½ teaspoon nutmeg

½ teaspoon salt

Mix dry ingredients.

3 eggs

¾ cup vegetable oil

¾ cup honey

½ cup milk – soy or regular

2 teaspoons vanilla

Mix above wet ingredients and add to dry.  Mix until just blended.  Place in oiled loaf pan.  Bake in 350 degree oven for one hour—or longer if using your solar oven!


Fun Sun Facts

  • People have been using the sun’s energy since ancient times when people used passive solar design in their homes and began to use glass to trap solar heat.

  • The use of curved mirrors to concentrate the sun's rays was developed by the Aztecs, Greeks, Romans, and Chinese; they sometimes used reflectors as powerful weapons in warfare.

  • In the 18th century, people began using glass to trap solar heat and the first "hot box" was invented by Horace de Saussure.

  • During the Industrial Revolution, various devices like solar pumps, solar cookers, solar heat engines, and solar stills were designed.

  • In the 19th century, French mathematics professor Augustin Mouchot invented the earliest solar-powered engine, converting solar energy into mechanical steam power.

  • In the 1950's solar cookers began to evolve into the products we see today. The United Nations and other agencies began designing solar cookers particularly to help people in developing nations address problems of deforestation and water sanitation.


Solar References


Internships Announcement: Community Gardens Network Intern & Garden Development Intern...
Community Gardens
Green City Growers Applications Now Being Accepted! The Green City Growers Program is a partnership...
You can help WCG raise up to $10,000 this year! All you have to do is link your Smith's Rewards...
Growing Community Gardens
Join us for the Growing Community Gardens Leadership Training Series December 1 Application...
Community Gardens
Salt Lake County Expands Sites Eligible for New Community Gardens The Parks for Produce Program...