Square Foot Solar Cooker DIY - Mother Earth News

Square Foot Solar Cooker DIY – Mother Earth News

Make this DIY project for the portable solar cooker that also doubles as a solar lamp! DIY solar panel cookers can be built to fold and go where you want them.

There are four styles of solar-powered stoves: box ovens, parabolic ovens, vacuum heat pipes, and plate ovens. Good commercial chest ovens are the best all-round choice. Equivalent stoves and Fresnel lenses will heat up very quickly, but they can hurt your eyes and start fires if left unattended. Heat pipes are interesting, but they often need an additional reflector, in addition, they are fragile and expensive. On the other hand, plate stoves are the easiest to build, portable, lightweight and multifunctional. Here’s how to build my own 2-foot- or “square-foot” cooktops, and some common uses for these off-grid appliances.

Tools and materials

  • A piece of corrugated plastic measures 18″ x 24″
  • tape measure
  • Marker
  • multi-use knife
  • upholstery nails
  • 18″ x 24″ piece of Mylar
  • Glue
  • 8-by-9-inch mirror
  • Adhesive tape
  • Wide mouth canning jar with lid and ring
  • Half liter wide mouth canning jar with lid and ring

DIY solar cooker project assembly

Corrugated plastic is ideal for building small-panel solar fireplaces. It is lightweight, waterproof, reasonably easy to cut and fairly inexpensive. In fact, an 18″ x 24″ piece, like the one used for campaign and other yard signs, is perfect for making travel-sized cooks. Just be sure to ask before you take a cue from someone’s yard. For a larger stationary cooker, use a sturdy wooden backing.

You can get two portable stovetops from one piece of 18″ x 24″ corrugated plastic. Using a tape measure and marker, divide the plastic into six 8″ by 9″ sections. Next, cut the plastic into two equal parts of three boards each. (Follow the cutting guide above.) I use a single edge razor blade, but you can use sturdy scissors, a table saw, a saw blade, or a knife.

Next, carefully cut half of the plastic only along each base line, so the sides can fold up.

Corrugated plastic, like cardboard, is made of rows of inner channels to give it strength. Cutting along channels requires more pressure than cutting along channels. Many of the cuts for this project are made only halfway through the material, just enough to allow it to bend. It is easy to make such half cuts through the channels with moderate pressure; The ribs in the plastic will prevent the blade from completely cracking.

Plastic mold divided into two parts

It is more difficult to make half cuts along the channels. If you use too much pressure, you’ll go all the way down. Also, the tip of the blade can stick to the edge of the channel and get rid of the blade line. To prevent this from happening, place the plastic on a lighted table or light it from behind, allowing you to see exactly where the channels are. Alternatively, push a small metal rod or wooden dowel into the channel, which will act as a guide for the blade and allow for a quick cut.

Once you separate the two boards and make half-cuts along the base lines, mark another line (the “final cut”) and cut in half about 1/8 inch inside both edges of the base lines. (It is easiest to push a dowel through the channel adjacent to this cut.) This will allow the final cut of the cooker to bend well for transfer.

Plastic mold showing cutting lines

To secure the sides of the board while not folding it, I use brass upholstery nails, but small nails or screws work just as well. (For wood boards, use glue and nails or screws to attach the sides.) Mark the holes for the staples on your board before adding mylar in the next step.

plastic cooker assembly

Mylar works well to provide the reflective surface needed for a solar cooker. You can also use mirrors that work well for a larger stationary unit.

Once the plate template is cut out, use it to create a template for mylar. Lay the mylar shiny side down, then place the mold tightly over the mylar. Mark around the template, then cut out the mylar. Attach mylar to the plastic using glue, contact cement (use a roller to ensure a wrinkle-free application), tape, or staples. Because mylar stains are easy to spot, it’s a good idea to use a mirror for the stove base instead. You should always return glass mirrors with duct tape or clear packing tape to prevent them from shattering if broken. (Mirrors break over time. Some consider it a sign of good use.)

Once completed, the stoves can be folded up to 8″ x 9″””” x 1/2″ wide. It’s perfect for a large purse or small backpack.

After building the inverter, the next project is to assemble the cooking pot. I like to use glass canning jars. The wide mouth and 1/2 quart canning jar is the perfect combination for a small cook. It won’t save much food, but it will make 8 ounces of rice in less than 80 minutes, completely unattended. With six hours of good sunlight, you can easily get a full 32 ounces of food.

First, paint the outside of the pint jar with flat black paint and let it dry for a day or so in the solar burner. Next, place the ring right side up half a pint inside the pint cap. Next, put the half-pint lid on top of the pint ring, so they make a platform for holding the pint jar. Place the half-pint jar (with the food contents) on top of the pint lid and ring, then place the jar upside down on top of it so you can attach it to the pint lid and ring. Once assembled, it is a shock-resistant, clutter-free system. Other sized jars work as well, so give them a try.

The jars and food contents will heat up, so handle them with care.

Also, always wear eye protection when working around bright and reflective lighting.

Water sterilization in solar cookers

These solar cookers can also pasteurize water. Most microorganisms will not survive in water that has been heated to 160 degrees Fahrenheit for at least 45 seconds, or 145 degrees for 30 minutes. This will not sterilize the water, which requires a much higher temperature, but is sufficient to kill most germs and can be used in emergency situations when other methods of disinfecting water are not available. (For more information, visit Centers for Disease Control and Prevention And read “Make Water Safe in an Emergency,” as well World Health Organization Boiling water search site.)

The recycled brown quadruple glass bottle is ideal for water pasteurization. My last test showed that a quart of water heated in a solar cooker rose from 80 degrees to 162 degrees in just under 1 hour and 45 minutes. Of course, this was in perfect sunny conditions. after the bottle has reached temperature, twist the top and remove it from the cooker; The bottle will form a vacuum. It is possible to make 4 or 5 liters on a sunny day. This method will not remove chemical contamination from the water.

Solar still DIY

Solar stoves also work well as a still solar-powered setup for distilling aromatics and hydrates.

You can make a simple distiller using the “BIJUJ” method (“a bottle in a jar under a jar”). Fill a 12-ounce brown or green bottle (source) with water and aromatic herbs, and place in a large canning jar (combined). Next, cover the top with a small inverted pot or quart jar (condensate), and set everything in the solar cooker. As the liquid heats up, it will create vapors that condense, eventually forming droplets that fall into the collector jar. To increase yield, use a fan to blow over the top jar, or cover the jar with some type of reflective material to help cool it.

You can smear a small amount of valve grinding compound where the two jars meet, and with a little work and rotation, it will grind the imperfections in the glass for a better seal. This process makes a loud and noisy noise, and you will need to wash the jars well afterwards.

It is also possible to make essential oils and other distillates using this technique. (Although it is illegal to distill spirits at home without a federal license.) I’ve made some excellent hydrosols using sage, rosemary, jasmine, and other herbs.

Instead of the bottle, you can use a wide-mouthed 8-ounce jar as a source, and if you place the plate at a slight inclination, the drips will fall to the side rather than back into the jar. This makes an excellent dryer.

Solar cooker for melting wax

You can use a DIY solar cooker setup to melt the wax for candles and coat your homemade jams with paraffin. 12 ounce aluminum can do well in melting wax. For faster thawing in cold weather, cover the can with a clear outer container. After it’s melted, you can pour the wax into candle molds or drop a wick or two directly into the can and let the wax cool. If the wick is too thin, the candle will die and will not burn completely. If it forms a wide range of wax, then the wick is just right.

One great use of melted wax is to make emergency candles. Works well for lighting, heating and cooking. Cut a tin can to one inch. Roll a 1-inch-wide piece of cardboard into a spiral shape, like a cinnamon roll. Put it in a tin can, then fill the can with wax. (Leave the center of the cardboard roll a little longer to act as the start of the wick.) This will result in a small candle about 3 ounces. My last test showed a burn time of over 1 hour per candle. One candle brought a cup of water to boil a liter of water, with probably enough burn time to boil a second quart.

These candles produce a smoky fire and will smoke a lot when blown out, so don’t use them to heat a nice pan, and only use them in a well-ventilated area.

Do not use these candles with a plastic Mylar cooker, as they will get very hot.

Resources for solar cooker designs

Some great designs for cooking ovens have been done by Jim La Joie, Roger Haines, Sharon Clausson, Matteo Muccioli and others.

For a more in-depth look at solar-powered stoves, check out Luther Krueger’s “Big Blue Sun Museum of Solar Cooking” YouTube channel. Contains more than 60 interviews with designers.

A comprehensive source of information can be found by featured Wiki global for solar cookers. This painstaking project, updated by Paul Hedrick and Tom Sponheim, is the go-to solar cooking.

Craig Bergland is the operator of the Secret Solar Institute of Northern Nevada Facebook page. All material there is available for free publication. Credit is nice, but not necessary. This and other similar projects were undertaken with help, tools, and encouragement from his home region of industry, Bridgewire, in Reno, Nevada.

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