Around the world, solar ovens are increasingly used to reduce dependence on burning wood or other fuels. Even if you have electricity, a solar oven can be a useful and economical tool to add to your kitchen tools. Follow the instructions in this article to build a small oven or one of greater consistency.
Materials - a large box - a small box - newspaper - aluminum foil - cardboard - 16 skewers - black cardboard - ruler - scissors
Steps
Method 1 of 2: Lightweight Solar Oven
Step 1. Put the small box inside the larger one
Make sure the small box is twice as wide after you put in the newspaper. This will act as an insulator.
Step 2. Cover the inside of the small box with black cardboard
This will serve to support some cardboard cut out in the shape of a trapezoid, almost like a square, but with the base wider than the top side. The top side must have the same length as the side of the box where it will be attached; consequently, the base will have to measure several centimeters more than the top side.
Step 3. Cover each piece of card stock with reflective material
Make sure the reflective material is flat on the card, and remove any creases. Adhere well using cementite or tape each side.
Step 4. Attach the reflective cards to the top four sides of the box
You can glue, staple or insert them as you please, leaving them free to move for the moment.
Step 5. Orient each reflector board at an angle of approximately 45 °
To do this, the easiest and safest way is to connect the cardboard boxes to each other at the level of the upper corners (for example, by making a hole at the height of these corners, through which a wire can pass that you can remove when you need to disassemble. everything). Alternatively, you can also use sticks to plant in the ground, which support the cartons in the correct position. If the day is windy, be careful that the cartons are not carried away.
If you use sticks, use some glue to secure them well to the cartons
Step 6. Place the oven in full sun and cook
Arrange the food in the smaller box and cook it. It is best to place the food in containers or in a small non-stick pan. Experiment with the most appropriate cooking times and how and where to place the oven. You may have to move the oven during cooking to follow the sun.
Method 2 of 2: Heavy Solar Oven
Step 1. Cut a metal bin in half vertically with a jigsaw
A can of oil will be perfect. Make sure you use a blade suitable for metal; when you are done, the half bin should look like a cradle. To make the oven, you will only need one of the two halves.
Step 2. Clean the inside of the half bin using a good detergent
Use an abrasive sponge and pay close attention to corners and crevices.
Step 3. Measure and cut out three pieces of sheet metal to line the inside surfaces of the half bin
You will need a large rectangle for the curved surface and two semicircles for the ends.
- To cut out the rectangular piece, one side must be equal to the length of the half bin; the other side, on the other hand, must be equal to the length of the curved surface, which you can measure with a flexible meter.
- To obtain the two semicircles: measure the radius of the semicircular ends; tie a marker to the end of a rope, then cut the free end to the length of the radius; holding this end in the middle, use the marker to draw a perfect circle on the sheet; cut out the circle you drew, then cut it into two identical halves.
Step 4. Attach the sheet metal inside the bin
If you want to use a riveter, you need to drill both the sheet metal and the bin with a drill, using a 3mm iron bit, then put the 3mm rivets in. Alternatively, you can join the sheet metal to the bin using screws; by doing so, the screw heads will protrude from the rear of the oven, but will then be incorporated into the insulation.
Step 5. Paint the inside of the oven with a reflective paint suitable for barbecues
This will maximize the amount of heat that will be developed inside the oven.
Step 6. Create a metal rail on three of the four top sides of the oven
It will be used to hold the lid of the oven (which you can put on and take off, handling it from the fourth side, which is left free). The easiest way to do this is to use six shaped sheets:
- Measure the shorter top edge of the oven and cut two pieces of sheet metal that length. Then, measure the longest edges, at this measurement subtract the width of the sheet and cut the remaining four sheets to the value you obtained; this will allow you to apply the sheets to the sides to support the piece at the end
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Place a piece of sheet metal on the trailing edge so that it fits from the outer vertical side towards the top horizontal edge. Arrange a second sheet on the first so that the vertical sides are level, but the horizontal ends leave enough space to accommodate the thickness of a sheet of glass. Put a shim (for example thick cardboard) between the two sheets to keep this space, then drill a hole to puncture the two sheets and the bin, then put a rivet to block everything. Remove the cardboard and repeat the operation for the other two edges.
By making this structure with overlapping sheets (instead of putting a single sheet along the entire edge) you will prevent the glass from getting stuck along the irregularities of the edges of the bin you cut by hand
Step 7. Turn the half bin over and apply spray sealer to the outer wall
Make sure you spray the right amount, considering that this tends to dilate a bit. Read the instructions on the can to find out more.
Step 8. Attach a stand to serve as a base for the oven
Drill holes in the half bin and screw it to the support you prefer (a piece of wood, a square of aluminum to which you have applied wheels, etc.), making sure that the support is wide enough to prevent the oven from tipping over. Depending on your geographical location, you can decide the optimal position of the oven to have the maximum solar exposure (for example in the northern hemisphere it is convenient to place it towards the south, while if you are at the equator it is sufficient to point the oven upwards).
Step 9. Drill drain holes in the bottom of the oven
Make small holes at a distance of a few centimeters, following a straight line, making sure to drill the insulation; this will allow the condensed steam to drip out of the oven.
Step 10. Slide a sheet of tempered glass cut to size into the metal rim
Tempered glass is not only thicker than normal glass, but it tolerates the rough edges on which it must slide well, so you can use it as it is. Since you will slide this glass up and down regularly, choose a 5mm thick glass for more stability. Order this item from a trusted glassmaker, indicating the exact dimensions of your solar oven.
Step 11. Insert a magnetic thermometer
Wood stove thermometers, for example, have magnetic support and withstand high temperatures well for extended periods.
Step 12. Put a thin aluminum grill on the bottom (optional)
Quietly place one or two racks on the bottom of the oven, so you can arrange food comfortably.
Step 13. Check the heat capacity of your oven on a sunny day
Although you can expect a temperature between 90 and 175 ° C, the size, materials and insulation of your oven are factors that determine the maximum temperature it can reach. Use this temperature to simmer the meat for several hours, as if you were using a slow cooker. Roast beef and chicken can take 5 hours to cook, while ribs may be ready in 3 hours (plus 5-10 minutes of barbecue grilling at the end). Measure the core temperature of the meat with a food thermometer, just like you would using an ordinary kitchen oven.
