Do-it-yourself solar oven: manufacturing features, useful tips. DIY solar oven How to make a solar oven with your own hands

There are actually several similar structures in the world. Let's start with Solar Furnace in France, that is, from France.

The Solar Furnace in France is designed to generate and concentrate the high temperatures required for various processes.

This is done by capturing the sun's rays and concentrating their energy in one place. The structure is covered with curved mirrors, their radiance is so great that it can be impossible to look at them, to the point of pain in the eyes. This structure was erected in 1970, with the Eastern Pyrenees chosen as the most suitable location. And to this day the Furnace remains the largest in the world.

The array of mirrors functions as a parabolic reflector, and the high temperature regime at the focus itself can reach up to 3500 degrees. Moreover, you can regulate the temperature by changing the angles of the mirrors.

Solar Furnace, using natural resource such as sunlight, is considered an indispensable method for obtaining high temperatures. And they, in turn, are used for a variety of processes. Thus, the production of hydrogen requires a temperature of 1400 degrees. Test modes for materials carried out in high-temperature conditions include a temperature of 2500 degrees. This is how spacecraft and nuclear reactors are tested.

So the Solar Oven is not just an amazing building, but also vital and efficient, while it is considered an environmentally friendly and relatively cheap way to achieve high temperatures.

The mirror array acts as a parabolic reflector. The light is focused at one center. And the temperature there can reach temperatures at which steel can be melted.

But the temperature can be adjusted by installing mirrors at different angles.

For example, temperatures around 1400 degrees are used to produce hydrogen. Temperature 2500 degrees - for testing materials in extreme conditions. For example, this is how nuclear reactors and spacecraft are checked. But temperatures up to 3500 degrees are used for the production of nanomaterials.

Solar Oven is an inexpensive, efficient and environmentally friendly way to obtain high temperatures.

In the southwest of France, grapes thrive and all kinds of fruits ripen - it's hot! Among other things, the sun shines here almost 300 days a year, and in terms of the number of clear days these places are second, perhaps, only to the Cote d'Azur. If we characterize the valley near Odeyo from the point of view of physics, then the power of light radiation here is 800 watts per 1 square meter. Eight powerful incandescent light bulbs. A little? It’s enough for a piece of basalt to spread into a puddle!

— The solar oven in Odeyo has a capacity of 1 megawatt, and for this it requires almost 3 thousand meters of mirror surface,- says Serge Chauvin, curator of the local solar energy museum. — Moreover, you need to collect light from such a large surface into a focal point with a diameter of a dinner plate.

Opposite the parabolic mirror, heliostats are installed - special mirror plates. There are 63 of them with 180 sections. Each heliostat has its own “point of responsibility” - a sector of the parabola onto which the collected light is reflected. Already on the concave mirror, the rays of the sun are concentrated at the focal point - that same oven. Depending on the intensity of radiation (read: clarity of the sky, time of day and time of year), very different temperatures can be achieved. In theory - up to 3800 degrees Celsius, in reality it turned out to be up to 3600.

— Along with the movement of the sun, heliostats also move across the sky,- Serge Chauvin begins his tour. — Each has an engine at the rear, and together they are controlled centrally. It is not necessary to install them in an ideal position - depending on the tasks of the laboratory, the degree at the focal point can be varied.

The solar oven in Odeyo began to be built in the early 60s, and was put into operation already in the 70s. For a long time it remained the only one of its kind on the planet, but in 1987 a copy was erected near Tashkent. Serge Chauvin smiles: “Yes, yes, exactly a copy.”

The Soviet stove, by the way, also remains operational. However, not only experiments are carried out on it, but also some practical tasks are performed. True, the location of the furnace does not allow achieving the same high temperatures as in France - at the focal point, Uzbek scientists manage to obtain less than 3000 degrees.

The parabolic mirror consists of 9000 plates - facets. Each is polished, aluminum coated and slightly concave for better focusing. After the furnace building was built, all the bevels were installed and calibrated by hand - this took three years!

Serge Chauvin leads us to a site not far from the furnace building. Together with us - a group of tourists who arrived in Odeyo by bus - the flow of lovers of scientific exoticism does not dry out. A museum curator set out to demonstrate the hidden potential of solar energy.

- Madame and Monsieur, your attention!— Although Serge looks more like a scientist, he looks more like an actor. — The light emitted by our star allows materials to be instantly heated, ignited and melted.

A solar oven employee lifts an ordinary branch and places it in a large vat with a mirror-like interior. It takes Serge Chauvin a few seconds to find the point of focus, and the stick instantly bursts into flames. Miracles!

While the French grandparents ooh and ahh, the museum worker moves to a free-standing heliostat and moves it just enough so that the reflected rays hit a smaller copy of a parabolic mirror installed right there. This is another visual experiment showing the capabilities of the sun.

- Madame and Monsieur, now we will melt the metal!

Serge Chauvin places a piece of iron in the holder, moves the vice in search of the focal point and, having found it, moves away a short distance.

The sun quickly does its job.

A piece of iron instantly heats up, begins to smoke and even spark, succumbing to the hot rays. In just 10-15 seconds, a hole the size of a 10-cent coin is burned in it.

- Voila!- Serge rejoices.

As we return to the museum building, and French tourists are seated in the cinema hall to watch a scientific film about the work of the solar furnace and laboratory, the caretaker tells us interesting things.

— Most often people ask why all this is needed,- Serge Chauvin throws up his hands. — From a scientific point of view, the possibilities of solar energy have been studied and applied where possible in everyday life. But there are tasks that, due to their scale and complexity of execution, require installations similar to this one. For example, how do we model the effect of the sun on the skin of a spacecraft? Or the heating of the descent capsule returning from orbit to Earth?

In a special refractory container installed at the focal point of the solar oven, it is possible to recreate such, without exaggeration, unearthly conditions. It has been calculated, for example, that a cladding element must withstand temperatures of 2500 degrees Celsius - and this can be verified experimentally here at Odeio.

The caretaker leads us around the museum, where various exhibits are installed - participants in numerous experiments carried out in the furnace. The carbon brake disc catches our attention...

- Oh, this thing is from a Formula 1 car wheel,- Serge nods. — Its heating under some conditions is comparable to what we can reproduce in the laboratory.

As mentioned above, the temperature at the focal point can be controlled using heliostats. Depending on the experiments performed, it varies from 1400 to 3500 degrees. The lower limit is necessary for producing hydrogen in the laboratory, the range from 2200 to 3000 is for testing various materials under extreme heat conditions. Finally, above 3000 is the area of ​​work with nanomaterials, ceramics and the creation of new materials.

— The oven in Odeyo does not perform practical tasks,- Serge Chauvin continues. — Unlike our Uzbek colleagues, we do not depend on our own economic activities and are engaged exclusively in science. Among our customers are not only scientists, but also a variety of departments, such as defense.

We just stop at a ceramic capsule, which turns out to be the hull of a drone ship.

— The War Ministry built a solar furnace of a smaller diameter for its own practical needs here, in the valley near Odeyo,- says Serge. — It can be seen from some sections of the mountain road. But they still turn to us for scientific experiments.

The caretaker explains the advantages of solar energy over any other energy in carrying out scientific tasks.

- First of all, the sun shines for free,- he bends his fingers. — Secondly, mountain air facilitates experiments in a “pure” form - without impurities. Thirdly, sunlight allows materials to be heated much faster than any other installation - for some experiments this is extremely important.

Interestingly, the stove can operate almost all year round. According to Serge Chauvin, the optimal month for conducting experiments is April.

- But if necessary, the sun will melt a piece of metal for tourists even in January,- the caretaker smiles. — The main thing is that the sky is clear and cloudless.

One of the undeniable advantages of the very existence of this unique laboratory is its complete openness to tourists. Up to 80 thousand people come here every year, and this does much more to popularize science among adults and children than a school or university.

Font-Romeu-Odeillot is a typical pastoral French town. Its main difference from thousands of the same is the coexistence of the mystery of everyday life and science. Against the background of a 54-meter mirror parabola are mountain dairy cows. And the constant hot sun.

Now let's move on to another building.

Forty-five kilometers from Tashkent, in the Parkent district, in the foothills of the Tien Shan at an altitude of 1050 meters above sea level, there is a unique structure - the so-called Big Solar Furnace (BSP) with a capacity of one thousand kilowatts. It is located on the territory of the Institute of Materials Science NPO "Physics-Sun" of the Academy of Sciences of the Republic of Uzbekistan. There are only two such ovens in the world, the second is in France.

The BSP was put into operation under the Soviet Union in 1987,” says Mirzasultan Mamatkasymov, scientific secretary of the Institute of Materials Science NPO Physics-Sun, Candidate of Technical Sciences. — Sufficient funds are allocated from the state budget to preserve this unique object. Two laboratories of the institute are located here, four are in Tashkent, where the main scientific base is located, where the chemical and physical properties of new materials are studied. We carry out the process of their synthesis. We experiment with these materials by observing the melting process at different temperatures.

The BSP is a complex optical-mechanical complex with automatic control systems. The complex consists of a heliostat field located on the mountainside that directs the sun's rays into a paraboloid concentrator, which is a giant concave mirror. At the focus of this mirror, the highest temperature is created - 3000 degrees Celsius!

The heliostat field consists of sixty-two heliostats arranged in a checkerboard pattern. They provide the mirror surface of the concentrator with luminous flux in the mode of continuous tracking of the Sun throughout the day. Each heliostat, measuring seven and a half by six and a half meters, consists of 195 flat mirror elements called "facets". The reflective area of ​​the heliostat field is 3022 square meters.

The concentrator, to which the heliostats direct the sun's rays, is a cyclopean structure forty-five meters high and fifty-four meters wide.

It should be noted that the advantage of solar furnaces, compared to other types of furnaces, is the instantaneous achievement of high temperatures, which makes it possible to obtain pure materials without impurities (thanks also to the purity of the mountain air). They are used for oil and gas, textile and a number of other industries.

Mirrors have a certain service life and sooner or later fail. In our workshops we produce new mirrors, which we install to replace the old ones. There are 10,700 of them in the concentrator alone, and 12,090 in the heliostats. The process of making mirrors takes place in vacuum installations, where aluminum is sprayed onto the surface of used mirrors.

Fergana.Ru:- How do you solve the problem of finding specialists, since after the collapse of the Union there was an outflow of them abroad?

Mirzasultan Mamatkasymov:- At the time the installation was launched in 1987, specialists from Russia and Ukraine worked here and trained our people. Thanks to our experience, we now have the opportunity to train specialists in this field ourselves. Young people come to us from the Faculty of Physics of the National University of Uzbekistan. After graduating from university, I myself have been working here since 1991.

Fergana.Ru:- When you look at this grandiose structure, at the openwork metal structures, as if floating in the air and at the same time supporting the “armor” of the concentrator, frames from science fiction films come to mind...

Mirzasultan Mamatkasymov:- Well, in my lifetime, no one here has tried to film science fiction using these unique “scenery.” True, Uzbek pop stars came to film their videos.

Mirzasultan Mamatkasymov:- Today we will melt briquettes pressed from powdered aluminum oxide, the melting point of which is 2500 degrees Celsius. During the melting process, the material flows down an inclined plane and drips into a special tray, where granules are formed. They are sent to a ceramic workshop located near the BSP, where they are crushed and used to make various ceramic products, ranging from small thread feeders for the textile industry to hollow ceramic balls that look like billiard balls. Balls are used in the oil and gas industry as floats. At the same time, evaporation from the surface of petroleum products stored in large containers at oil depots is reduced by 15-20 percent. In recent years, we have manufactured about six hundred thousand of these floats.

We produce insulators and other products for the electrical industry. They are characterized by increased wear resistance and strength. In addition to aluminum oxide, we also use a more refractory material - zirconium oxide with a melting point of 2700 degrees Celsius.

The smelting process is monitored by a so-called “technical vision system”, which is equipped with two special television cameras. One of them directly transfers the image to a separate monitor, the other to a computer. The system allows you to both observe the melting process and carry out various measurements.

It should be added that the BSP is also used as a universal astrophysical instrument, opening up the possibility of studying the starry sky at night.

In addition to the above work, the institute pays great attention to the production of medical equipment based on functional ceramics (sterilizers), abrasive instruments, dryers and much more. Such equipment has been successfully introduced into medical institutions in our republic, as well as into similar institutions in Malaysia, Germany, Georgia and Russia.

In parallel, the institute developed low-power solar installations. For example, the institute’s scientists created solar furnaces with a capacity of one and a half kilowatts, which were installed on the territory of the Tabbin Institute of Metallurgy (Egypt) and at the International Metallurgical Center in Hyderabad (India).

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Solar ovens or “solar cookers” are increasingly being used around the world to reduce the use of wood and other fuels. Even if you have electricity, this energy-saving device will always come in handy. To make a lightweight or powerful solar oven, follow these instructions.

Steps

Lightweight solar oven

Place the smaller box inside the larger box. Fill the space between the boxes with torn newspapers. This is an insulating material.

Line the inside of the smaller box with black construction paper. It will absorb heat. When you secure the construction paper to the walls of the box, make sure that the width of the tapered end of the square is the same as the width of the side on which you secure the square; the width of the flared end should be several centimeters larger than the width of the narrowed end.

Cover all areas of the cardboard with reflective foil-type material. The reflective material should fit snugly, so smooth out all wrinkles and folds. Secure the material with rubber cement or tape to the side of each reflector.

Attach all the reflectors to the top of the box. You can use glue, a stapler or thread and let the reflectors hang for now.

Prop each reflector at a 45 degree angle. The easiest way to do this is to connect the reflectors at the flared top corners (eg by piercing adjacent corners and tying them with string, then untying them for disassembly). However, it is possible to insert rods into the ground below the reflectors or something else that can hold them in place. If it's windy outside, secure the poles tightly to prevent them from blowing away.

• If you take the rods, secure them with glue for greater reliability.

1. Place the oven in the open sun and cook. Place food in a small cooking box. Best cooked in jars or on a small, dark baking tray. Experiment with cooking times and where you place the box. You may have to change the position of the box several times during the cooking process to catch the sun's rays.

   Powerful solar oven

   1. Use a power jigsaw to cut the metal can vertically. A can for petroleum products will do. Take a metal cutting saw. When you are finished, half of the can should look like a cradle. For the stove you only need one half of the can.

      Wash the inside of the can thoroughly with degreasing soap. Use a scrub brush, paying attention to nooks and crannies.

      Measure and cut pieces of sheet metal to cover the inside of the can. You will need one large rectangle for the arced side and two half circles for the other sides.

      • To cut a large rectangle, measure one side equal to the inside height of half the can and the other equal to the arcuate length of the side, which you can measure with a flexible tape measure (eg seamstress' tape).
      • To cut two semicircles, measure the radius (half the diameter) of the semicircular sides; Holding the end of the tape in the middle, draw a perfect circle on the sheet metal with a marker, cut it out and cut it in half.

   2. Attach the sheet metal to the inside of the can. To attach sheet metal pieces with blind rivets, drill holes through the sheet metal and can with a 3mm drill bit, then insert 3mm rivets. You can also drill holes and then attach the sheet metal to the can with screws to secure the sheet metal together. The screws will now be sticking out of the back of the oven, but later they will be covered with insulation.

      Paint the inside of the can with reflective BBQ paint. It will increase the temperature inside the oven.

      Cover three of the four top edges of the oven with a continuous metal opening. This will secure the glass top (which you will slide in and out through the fourth open side) in place. The easiest way to make it is from six pieces of a metal apron:

      • Measure the short top edge of the stove and cut two lengths to that length. Then measure the long top edge of the stove, subtract the width of the apron from the resulting length, and cut the remaining four lengths; Attach the apron to the sides, making room for a piece at the end.
      • Place the apron piece on the last edge so that the curved metal “folds” of the vertical outside edge are over the horizontal top edge. Place the second piece of apron on top of the first so that the vertical sides are at the same level, but there is a wide enough hole left for the passage of the glass tabletop. Place a strip of material (eg thick cardboard) between two pieces of apron to leave an open gap, then drill through the double layer of apron and can and rivet them together. Pull out the cardboard and do the same with the remaining two edges.
        • An apron “sandwich” (as opposed to a single-layer opening along the top) will protect the glass from staining on the uneven edges of the can that you cut by hand.

   3. Turn half the can upside down and spray the insulation on the outside walls. The layer should be thin because it will expand later. Look at the canister for further instructions.

      Secure the bottom of the oven to the base. Simply drill and secure the can onto a base that is most convenient for your location (eg wooden or rectangular aluminum frame on wheels, etc.), making sure the base is wide enough to prevent the can from tipping over. Depending on your location, you may need to tilt the stove slightly to get better sunlight (for example, in the northern hemisphere, the stove should be tilted towards the south, while at the equator, it should be pointed straight up).

      Drill drainage holes in the bottom of the oven. Simply drill small holes every few inches in a straight line through the bottom, drilling into the insulation. Thanks to these holes, accumulated and cooled steam will flow down from the oven.

      Insert the appropriately sized tempered glass into the metal opening. Tempered glass is not only stronger than regular glass, but it also comes with ground edges so you can use it right away. Since you will be moving the glass regularly, choose a thicker sheet (eg 5mm) for extra strength. Order one from a hardware store, specifying the size of your solar oven.

      Install a magnetic thermometer. For example, wood stove thermometers have a magnetic backing that allows the thermometer to withstand constant high temperatures.

      Place a thin aluminum grill along the bottom (optional). Just add one or two aluminum grills for convenient food placement.

      Test the heat capacity of your stove on a hot sunny day. It is reasonable to assume that the maximum temperature for a given oven is between 250 and 350 degrees Fahrenheit (90-175 degrees Celsius). The heat capacity of a particular oven model is determined by the size, materials from which it is made, and insulation. Use this temperature to stretch out the cooking of the meat over several hours, as if you were cooking it in a slow cooker. Cooking roast beef or chicken will take about 5 hours, and ribs will take only 3 (plus 5-10 minutes of roasting at the end). Check the internal temperature of your meat with a thermometer when you close the oven.

   • Scrap material can be used to make a lightweight stove for a school project.
   • You should use the oven in an area exposed to the sun. Thermal energy comes from the sun.
   • To make a light oven more efficient and cook at a very high temperature, trap the sun's rays (without a cover, hot air will constantly rise and cool air will remain). Oven bags are cheap and easy to use. Just put the pan in which you cook something in such a bag. A glass panel, preferably double, is an alternative solution. The glass should be slightly larger than the smaller box, but not so much that it will not fit into the larger box.
   • Positioning the rods that support the reflectors will be much easier if you have a partner to hold the reflectors at the correct angle while you install the rods and secure the result with glue.
   • As a last resort, reheat pre-cooked foods like canned food by stashing them in two ovenproof bags: put the food in a small bag, and the larger bag, zip them up for a great heat trap. Place the food on a reflective surface, such as a bag of chips or a reflector on your car windshield.

   Warnings

   • Be careful when removing food or utensils from the oven or removing glass (if present). The oven may become very hot. Use oven mitts or tongs when handling ovens or stovetops.
   • A light stove is not protected from wild animals. Therefore, hide it in a protected place.
   • Never wash the glass of a high-power oven in cold water while it is still hot. The glass will burst due to a sudden change in temperature.
   • Never put your hands into a hot oven without any protection - you will get burned.
   • A light oven is effective almost anywhere you can capture sunlight, but you won't be able to set the temperature and determine the cooking time like you can with a conventional oven. Make sure food is cooked to the recommended temperature by using a meat thermometer.

The potential of solar heat can be used not only to generate electricity at large power plants or for heating residential complexes, but also in ordinary everyday life, for example, for cooking. The very idea of ​​​​creating a stove that runs exclusively on solar energy is so relevant that folk craftsmen have long been able to put it into practice. This article will help you make a solar oven with your own hands, without much effort, so that you can provide yourself and your friends with a delicious hot lunch. The very forces of nature will assist you in this. It is clear that cooking time in a solar oven will be much longer,than in a conventional oven or electric stove. However, such a structure can be placed next to a barbecue or grill, thereby adding novelty to your area.

Inexpensive and publicly available materials are used to make a solar oven:

Bars;
- plywood 6-10 mm;
- roofing iron 0.5mm (galvanized);
- glass 3-4 mm;
- insulation (mineral wool).
- mirror.

First of all, we make the frame of the solar oven from 40x40 beams and plywood. The thicker the plywood, the stronger the structure will be.

We make a glass frame that is attached to the body using hinges.

From roofing iron 0.5 mm. cut out the inside of the oven (casing). At the same time, we cut the sheet according to the drawing.

After the casing is ready, we nail it inside the casing using nails. Then we sand the edges so that there are no burrs.

We install the glass in the frame using transparent silicone sealant and secure it with glazing beads.

We mount the reflective panel on hinges.

Don’t forget to attach handles for carrying the solar oven and for opening the glass door.

We carefully insulate the sides, between the metal casing and the body, and the bottom of the stove with mineral wool. Then we sew up the bottom with plywood.

We paint the metal casing with heat-resistant, matte black paint.

Glue a mirror (mirror tile) onto the reflective panel

The solar oven is ready for use. The first use of the solar oven must be done without food. Because the paint may emit an unpleasant odor in the first days.

Don’t forget to treat the stove body with paint and antiseptic to prevent weathering.

The oven must be placed in direct sunlight. If the sun is low, use a reflector for best results.

For faster cooking, use black cookware, preferably thin aluminum.

Second manufacturing method. Unfortunately, no photos.

So, to build a solar stove we will need the following materials:

1. wooden or metal box
2. a piece of dark cardboard, preferably black
3. several pieces of small, black-painted stones
4. glass according to the size of the box
5. four pieces of tin as reflectors.

Let's start with the construction of the main frame. It can be welded from metal corners, but it is best to knock it down from bars and boards. Select the size and shape of the box to your taste, depending on the type and quantity of food being prepared. It should not be a strictly square or rectangular stove. The design can be given any shape, such as hexagonal, round, or even elliptical. Here, perhaps, everything depends on your imagination and desire to do something unusual and original.

When the box is made, you need to cover the bottom and inner walls with black cardboard or thick paper. The color of the cladding must be black, as it absorbs the sun's rays more effectively. The paper must be secured to the box using nails with a large head or self-tapping screws with a washer.

Now cut the tin reflectors to fit the box, sand all sides with sandpaper or a file to remove any burrs, and attach the four reflectors to the top of the box. This can be done using metal or plastic corners, or simply screw the tin with screws and bend it at the required angle to the Sun. It would be more correct to install reflectors on window hinges, which can be bought on the market or at any hardware store. Using the hinges, you can easily adjust the reflectors depending on the position of the Sun in the sky.

Tin reflectors concentrate and redirect the sun's rays into a wooden box, thereby ensuring high-quality and fast cooking.

The last step in making a solar oven is cutting and installing glass, which will perform the main function of absorbing sunlight, which will be converted into thermal energy to heat food. Additionally, the glass acts as a cover for your solar oven.

Now all that remains is to find a few medium-sized dark stones on your site or elsewhere and place them on the bottom of the box. If you come across stones that are too light, try painting them black and letting them dry completely. What are the stones for? They will be a kind of solar heat storage device. With their help, you can regulate the temperature in the stove by removing or, conversely, adding new stones. Hot stones will allow you to start cooking dinner even at a time when the Sun will not be so bright and warm.

If you want to know exactly what the temperature is inside your “solar oven”, take the time to install a small food thermometer, which can be purchased at any grocery supermarket.

The heating time of the solar stove is about 20-30 minutes, depending on the time of day and the amount of solar activity.

That's all, your stove is ready. Enjoy only clean and healthy food!

The simplest design of solar ovens made from cardboard boxes

And now a master class on how to make the solar battery itself.

So what is it solar battery, panel (SB)? It is essentially a container containing an array of solar cells. Solar cells are the things that actually do all the work of converting solar energy into electricity. Unfortunately, to obtain enough power for practical use, you need quite a lot of solar cells. Also, solar cells are VERY fragile. That is why they are united in the Security Council. The battery contains enough cells to produce high power and protects the cells from damage. Doesn't sound too difficult. I'm sure I can do it myself.

I started my project, as usual, by searching the Internet for information on homemade security systems and was shocked at how little there was. The fact that few people made their own solar panels made me think it must be very difficult. The idea was shelved, but I never stopped thinking about it.

After some time, I came to the following conclusions:
- the main obstacle in building a solar system is purchasing solar cells at a reasonable price
- new solar cells are very expensive and difficult to find in normal quantities for any money
- defective and damaged solar cells are available on eBay and other places for much cheaper
- “second grade” solar cells can possibly be used to make a solar battery

When it dawned on me that I could use defective elements to make my own SB, I got to work. I started by purchasing items on eBay.

I bought several blocks of monocrystalline solar cells measuring 3x6 inches. To make a SB, you need to connect 36 such elements in series. Each element generates about 0.5V. 36 cells connected in series will give us about 18V, which will be sufficient to charge 12V batteries. (Yes, this high voltage is indeed necessary to effectively charge 12V batteries). This type of solar cell is paper thin, brittle and brittle like glass. They are very easy to damage.

The seller of these items dipped sets of 18 pieces. in wax for stabilization and delivery without damage. Wax is a headache to remove. If you have the opportunity, look for items that are not coated with wax. But remember that they may suffer more damage during transportation. Note that my elements already have soldered wires. Look for elements with already soldered conductors. Even with these elements, you need to be prepared to do a lot of work with the soldering iron. If you buy elements without conductors, get ready to work 2-3 times more with a soldering iron. In short, it is better to overpay for already soldered wires.

I also bought a couple of sets of elements without waxing from another seller. These items came packaged in a plastic box. They were hanging around in the box and chipped a little on the sides and corners. Minor chips don't matter much. They won't be able to reduce the power of the element enough to need to worry about it. The elements I purchased should be enough to assemble two SBs. I know I'll probably break a few when putting them together, so I bought a little more.

Solar cells are sold in a wide range of shapes and sizes. You can use larger or smaller ones than my 3x6 inches. Just remember:
- Elements of the same type produce the same voltage regardless of their size. Therefore, to obtain a given voltage, the same number of elements will always be required.
- Larger elements can generate more current, and smaller elements can generate less current.
- The total power of your battery is determined by its voltage multiplied by the current generated.

Using larger cells will allow you to get more power at the same voltage, but the battery will be larger and heavier. Using smaller cells will make the battery smaller and lighter, but will not provide the same power. It is also worth noting that using cells of different sizes in one battery is a bad idea. The reason is that the maximum current generated by your battery will be limited by the current of the smallest cell, and larger cells will not operate at their full capacity.

The solar cells I chose are 3 x 6 inches in size and are capable of generating approximately 3 amps of current. I plan to connect 36 of these cells in series to get a voltage of just over 18 volts. The result should be a battery capable of delivering about 60 watts of power in bright sunlight. It doesn't sound very impressive, but it's still better than nothing. Moreover, this is 60W every day when the sun is shining. This energy will be used to charge the battery, which will be used to power lights and small equipment just a few hours after dark. It's just that when I go to bed, my energy needs are reduced to zero. In short, 60 W is quite enough, especially considering that I have a wind generator that also produces energy when the wind blows.

After you buy your solar cells, store them in a safe place where they won't break, be played with by children, or be eaten by your dog until you are ready to install them in your solar cell. The elements are very fragile. Rough handling will turn your expensive solar cells into little blue, shiny, useless shards.

So, a solar panel is just a shallow box. I started by building such a box. I made it shallow so the sides don't shade the solar cells when the sun shines at an angle. It is made from 3/8" thick plywood with 3/4" thick batten sides. The sides are glued and screwed into place. The battery will contain 36 cells measuring 3x6 inches. I decided to divide them into two groups of 18 pieces. just to make them easier to solder in the future. Hence the central bar in the middle of the drawer.

Here's a little sketch showing the dimensions of my SB. All measurements are in inches (sorry, metric fans). The 3/4-inch thick beads go around the entire sheet of plywood. The same side goes in the center and divides the battery into two parts. In general, I decided to do this. But in principle, the dimensions and overall design are not critical. You can freely vary everything in your sketch. I give the dimensions here for those people who constantly whine that I include them in my sketches. I always encourage people to experiment and invent something of their own rather than blindly following instructions written by me (or someone else). Perhaps you can do better.

View of one of the halves of my future battery. This half will house the first group of 18 elements. Note the small holes in the sides. This will be the bottom of the battery (the top is at the bottom in the photo). These are ventilation holes designed to equalize the air pressure inside and outside the SB and serve to remove moisture. These holes should only be at the bottom of the battery, otherwise rain and dew will get inside. The same ventilation holes should be made in the central dividing strip.

Next, I cut out two pieces of fiberboard that were the right size. They will serve as substrates on which solar cells will be assembled. They should fit freely between the sides. It is not necessary to use perforated fiberboard sheets, I just happened to have some on hand. Any thin, hard and non-conductive material will do.

To protect the battery from weather troubles, we cover the front side with plexiglass. These two pieces of plexiglass were cut to completely cover the entire battery. I didn't have one piece big enough. Glass can also be used, but glass breaks. Hail, rocks and flying debris can break the glass and simply bounce off the plexiglass. As you can see, a picture is beginning to emerge of what the solar battery will look like in the end.

Oops! The photo shows two sheets of plexiglass connected on the central partition. I drilled holes around the edge to seat the plexiglass onto the screws. Be careful when drilling holes near the edge of the plexiglass. If you press too hard, it will break, which is what happened to me. In the end, I simply glued the broken piece and drilled a new hole nearby.

After that, I painted all the wooden parts of the solar panel with several layers of paint to protect them from moisture and environmental influences. I painted the box inside and out. A scientific approach was used to select the type of paint and its color. I whipped up all the leftover paint I had in my garage and picked out a can that had enough paint to do the job.

The substrates were also painted in several layers on both sides. Make sure you stain everything well, otherwise the wood may warp from moisture. And this can damage solar cells that will be glued to the substrates.

Now that I have the basis for the solar system, it's time to prepare the solar cells.

As I said before, removing wax from solar cells is a real pain. After some trial and error, I finally found a good way. But I still recommend buying the elements from someone who doesn't wax them.

The first step is to "bathe" in hot water to melt the wax and separate the elements from each other. Do not let the water boil, otherwise the steam bubbles will violently hit the elements against each other. Boiling water can also be too hot and electrical contacts in the elements may be broken. I also recommend immersing the elements in cold water and then heating them slowly to prevent uneven heating. Plastic tongs and a spatula will help separate the elements as the wax melts. Try not to pull too hard on the metal conductors - they may break. I discovered this when I tried to split my elements. It's good that I bought them with a reserve.

Here is the final version of the "setup" I used. My friend asked what I was cooking. Imagine her surprise when I answered, “Solar cells.” The first "hot bath" for melting the wax is in the background on the right. In the foreground on the left is hot soapy water, and on the right is clean hot water. The temperatures in all pans are below the boiling point of water. First, melt the wax in a distant pan, transfer the elements one by one into soapy water to remove any remaining wax, and then rinse in clean water. Place the elements on a towel to dry. You can change the soap and rinse water more often. Just do not pour used water down the drain, because... the wax will harden and clog the drain. This process removed virtually all the wax from the solar cells. Only some have thin films left on them, but this will not interfere with soldering and operation of the elements. Washing with solvent will probably remove any remaining wax, but it can be dangerous and smelly.

Several separated and cleaned solar cells are dried on a towel. Once separated and the protective wax removed, their fragility made them surprisingly difficult to handle and store. I recommend leaving them in the wax until you are ready to install them in your SB. This will prevent you from breaking them before you can use them. So build the base for the battery first. It's time for me to install them.

I started by drawing a grid on each base to make it easier to install each element. Then I laid out the elements on this grid, back side up, so they can be soldered together. All 18 cells for each half of the battery must be connected in series, after which both halves must also be connected in series to obtain the required voltage.

Soldering the elements together is difficult at first, but I quickly got the hang of it. Start with only two elements. Place the connecting wires of one of them so that they intersect the solder points on the back of the other. You also need to make sure that the distance between the elements corresponds to the markings.

I used a low power soldering iron and a solder rod with a rosin core. Also, before soldering, I lubricated the soldering points on the elements with flux using a special pencil. Do not press on the soldering iron! The elements are thin and fragile; if you press hard, they will break. I was sloppy a couple of times and had to throw out a few items.

We had to repeat the soldering until we got a chain of 6 elements. I soldered the connecting bars from the broken elements to the back of the last element of the chain. I made three such chains, repeating the procedure twice more. There are 18 cells in total for the first half of the battery.

Three chains of elements must be connected in series. Therefore, we rotate the middle chain 180 degrees relative to the other two. The orientation of the chains turned out to be correct (the elements are still lying backside up on the substrate). The next step is gluing the elements in place.

Gluing the elements will require some skill. Apply a small drop of silicone sealant in the center of each of the six elements of one chain. After this, we turn the chain face up and place the elements according to the markings that we made earlier. Press the pieces lightly, pressing down the center to adhere them to the base. Difficulties arise mainly when turning over a flexible chain of elements. A second pair of hands won't hurt here.

Do not apply too much glue and do not glue the elements anywhere other than the center. The elements and the substrate on which they are mounted will expand, contract, bend and deform with changes in temperature and humidity. If you glue an element over the entire area, it will break over time. Gluing only in the center gives the elements the opportunity to freely deform separately from the base. The elements and the base can be deformed in different ways and the elements will not break.

Here is the fully assembled half of the battery. I used copper braid from the cable to connect the first and second chain of elements.

You can use special buses or even ordinary wires. I just had copper braided cable on hand. We make the same connection on the reverse side between the second and third chain of elements. I attached the wire to the base with a drop of sealant so that it would not “walk” or bend.

Test of the first half of the solar battery in the sun. In weak sun and haze, this half generates 9.31V. Hooray! Works! Now I need to make another half of the battery like this.

Once both bases with elements are ready, I can place them in place in the prepared box and connect them.

Each half is placed in its place. I used 4 small screws to secure the base with the cells inside the battery.

I ran the wire to connect the battery halves through one of the ventilation holes in the central side. Here, too, a couple of drops of sealant will help secure the wire in one place and prevent it from dangling inside the battery.

Each solar panel in the system must be equipped with a blocking diode connected in series with the battery. The diode is needed to prevent the batteries from discharging through the battery at night and in cloudy weather. I used a 3.3A Schottky diode. Schottky diodes have a much lower voltage drop than conventional diodes. Accordingly, there will be less power loss on the diode. I bought a set of 25 31DQ03 brand diodes on eBay for just a couple of bucks. I will still have a lot of diodes left for my future SBs.

At first I planned to attach the diode to the outside of the battery. But after looking at the technical characteristics of the diodes, I decided to place them inside the battery. For these diodes, the voltage drop decreases with increasing temperature. The temperature inside my battery will be high, the diode will work more efficiently. We use a little more silicone sealant to secure the diode.

I drilled a hole in the bottom of the battery near the top to bring the wires out. The wires are tied in a knot to prevent them from being pulled out of the battery, and are secured with the same sealant.

It is important to let the sealant dry before we secure the plexiglass in place. I advise based on previous experience. Silicone fumes can form a film on the inside surface of the plexiglass and elements if you do not allow the silicone to dry in the open air.

And some more sealant to seal the outlet.

I screwed a two-pin connector onto the output wire. The socket of this connector will be attached to the battery charge controller that I use for my wind generator. Thus, the solar battery can work in parallel with it.

This is what a completed SB looks like with a plexiglass screen attached. The plexiglass is not yet sealed. I didn't seal the joints at first. I did some testing first. Based on the test results, I needed access to the insides of the battery, and a problem was discovered there. The contact on one of my elements has come loose. This may have happened due to temperature changes or due to careless handling of the battery. Who knows? I disassembled the battery and replaced this damaged element. Since then there have been no problems. In the future, I may seal the joints under the plexiglass with caulk or cover them with an aluminum frame.

Here are the results of testing the voltage of the completed battery in bright winter sun. The voltmeter shows 18.88V without load. This is exactly as I expected.

And here is a current test under the same conditions (bright winter sun). The ammeter shows 3.05A - short circuit current. This is just close to the calculated current of the elements. The solar battery works great!

Solar battery in operation. I move it a couple of times a day to maintain orientation to the sun, but it's not that big of a deal. Perhaps someday I will build an automatic sun tracking system.

I have already written an article about how to make a parabolic solar oven based on a satellite dish. Such a stove showed excellent characteristics and efficiency. However, not everyone has an unnecessary satellite dish, and buying one specifically for the manufacture of a solar oven is very expensive. Therefore, this article will talk about the manufacture of a parabolic solar oven based on foil and cardboard.

Materials that the author used to create this solar oven model:
1) corrugated cardboard
2) stationery knife
3) glue
4) polished foil
5) bolts m4 20 mm
6) wide washers
7) fabric
8) wire

Let us consider in as much detail as possible the plan for creating a parabolic solar oven, as well as the main distinctive features of this model.

And so, the author decided to make a solar oven in the shape of a satellite dish, using cardboard as the main material.
To be more precise, corrugated cardboard from ordinary cardboard boxes was used. Therefore, in order for all the elements to be sufficiently even and strong, the author fastened two such sheets with glue so that the corrugated cardboard waves of each sheet were perpendicular to each other.

To simplify the manufacture of a solar oven, the author made several diagrams, according to which construction proceeded.
The author decided to create a parabola from 12 parts of the same size. According to the dimensions shown in the diagrams, the future solar oven will have an area of ​​about 0.8 square meters. However, you can increase the scale of the elements thus giving a larger surface area of ​​the parabolic solar furnace, which in turn will increase the maximum temperature that this furnace can produce.

In order to speed up the process of cutting out elements of a solar oven from sheets of cardboard, the author drew out one element and made it a template. Next, this template segment was simply applied to the cardboard and all other segments were cut out using a stationery knife.

To protect and strengthen the elements of the solar oven, the author made their edging. To do this, a 5 cm wide strip of thick paper was glued to each element along the edges. The elements were also connected to each other using a glued strip of fabric, which will act as a hinge joint. This connection will allow the solar oven to be folded if necessary for storage or movement.

Since the author preferred to use the “accordion” folding of the stove, the strips of fabric between the segments were attached alternately from the front side to the back. At the same time, the author left a gap of 2-3 mm wide between each element, so the edges of the elements will not experience additional load when folding the solar oven.

After all the elements were connected together, the author received the necessary parabola. The next step was to glue foil to its inner surface. The author used polished foil, since it has a fairly large reflective effect. Stores sell self-adhesive wallpaper with a mirror surface, which is also perfect for gluing the inner surface of a solar oven.

To fix the parabola-shaped elements, the author screwed several bolts to the first and twelfth segments of the solar oven. The author used M4 20 mm bolts and wide washers to securely fix them, since they will be screwed into the cardboard.

At the point of convergence of the elements of the solar oven, the author made a round plane of plywood. This plane acts as a plug, as well as a retainer for the narrow part of the solar oven elements. To do this, the author used a wire that will attach the elements to this plug.

All this is perfectly shown in the schematic pictures below:

As can be seen from this diagram, the wire is inserted into the hole in each segment one at a time, after which all segments at the base are wrapped with rope and securely fixed.

In order to make a stand on which the pan will be installed, the author used a wooden block and a metal grate.

In this way, you can easily adjust the angle of inclination of the solar oven itself and the location of the pan in it, which directly depends on the position of the sun at horizon level.

Since the solar oven is primarily made of cardboard and foil, it is quite lightweight, so it needs to be secured during installation to prevent it from being blown away by the wind. The solar oven is fixed using guy ropes, and in order to ensure that the geometry of the oven does not suffer from these guy wires, the author tightens the parabola with a rope.

Surprisingly, in clear weather, the speed of cooking, according to the author, is twice as fast as when using a gas stove. Other advantages of this stove are that it is very cheap to manufacture, as it does not require expensive materials. Thanks to its folding design, this solar oven is very easy to transport and store, and it is also very lightweight since its main component is cardboard.

Ecology of consumption. Science and technology: The successful use of solar ovens (stoves) was noted in Europe and India already in the 18th century. Solar cookers and ovens absorb solar energy, turning it into heat, which accumulates inside an enclosed space.

The successful use of solar ovens (stoves) was noted in Europe and India as early as the 18th century. Solar cookers and ovens absorb solar energy, turning it into heat, which accumulates inside an enclosed space. The absorbed heat is used for cooking, frying and baking. The temperature in a solar oven can reach 200 degrees Celsius.

Box solar ovens

Box solar ovens consist of a well-insulated box, painted black inside, into which black pots of food are placed. The box is covered with a two-layer “window”, which allows solar radiation into the box and retains heat inside. In addition, a lid with a mirror on the inside is attached to it, which, when folded, enhances the incident radiation, and when closed improves the thermal insulation of the oven.

Main advantages of solar box ovens:

• Both direct and diffuse solar radiation are used.
• They can heat several pans at the same time.
• They are lightweight, portable and easy to handle.
• They do not need to turn after the Sun.
• Moderate temperatures make stirring unnecessary.
• Food stays warm all day.
• They are easy to make and repair using local materials.
• They are relatively inexpensive (compared to other types of solar ovens).

Of course, they also have some disadvantages:

• You can only cook with them during the daytime.
• Due to the moderate temperature, food takes a long time to cook.
• The glass lid leads to significant heat loss.
• Such ovens “can’t” fry.

Due to their advantages, solar box ovens are the most common type of solar ovens. They come in different types: industrial production, artisanal and homemade; the shape may resemble a flat suitcase or a wide, low box. There are also stationary ovens made of clay, with a horizontal lid (in tropical and subtropical regions) or inclined (in temperate climates). For a family of five, standard models with an aperture area (entrance area) of about 0.25 m2 are recommended. There are also larger versions of stoves on sale - 1 m2 or more.

Since the heat absorbed by the inner surface of the box must be transferred to the pans, the best material for the box is aluminum, which has high thermal conductivity. In addition, aluminum is not subject to corrosion. For example, a steel box, even with a galvanized coating, cannot withstand the hot and humid environment inside the oven for long during the cooking process. Sheet copper is too expensive.

Metal parts that could create thermal bridges must not be attached to the outside of the box. The thermal insulation material can be glass, synthetic wool or some natural material (husks of peanuts, coconuts, rice, corn, etc.). Whatever material is used, it must remain dry.

The furnace lid may consist of one or two glasses with an air gap. The distance between two layers of glass is usually 10-20 mm. Research has shown that using a transparent honeycomb material that divides the interior space into small vertical cells can significantly reduce the heat loss of a stove, thereby increasing its efficiency. The inner glass is exposed to heat, so tempered glass is often used; or both layers can consist of ordinary glass with a thickness of about 3 mm.

The outer cover of the solar oven is a reflector that amplifies the incident radiation. The reflective surface can be a regular glass mirror, a plastic sheet with a reflective coating, or an unbreakable metal mirror. As a last resort, you can use foil from cigarette packs.

The outer box of the solar oven can be made of wood, fiberglass, or metal. Fiberglass is lightweight, inexpensive, and water-resistant, but not very durable under continuous use. Wood is stronger, but heavier and more susceptible to deterioration due to moisture. Aluminum sheets in combination with wooden fasteners form the highest quality surface, resistant to mechanical stress, temperature changes and humidity. An aluminum-reinforced wooden box is the most durable, but it is more expensive and quite heavy, and its production also takes time.

The productivity of a standard solar oven with an aperture area of ​​0.25 m2 reaches about 4 kg of food per day, i.e. sufficient for a family of five.

Peak temperatures inside a solar oven can reach over 150°C on a sunny day in the tropics; this is approximately 120 °C higher than the ambient temperature. Since the water contained in food does not heat above 100 °C, the temperature inside a filled oven will always be correspondingly lower.

The temperature in the solar oven drops sharply when food containers are placed in it. It is also important that the temperature remains well below 100°C for most of the cooking time. But a boiling point of 100 °C is not needed for cooking most vegetables and cereals.

The average cooking time in a solar oven is 1-3 hours in good sunny conditions and moderate load. Using thin-walled aluminum pans significantly reduces cooking time compared to stainless steel cookware. In addition, the following factors also influence:

• Cooking time is reduced in high light conditions, and vice versa.
• High ambient temperatures shorten cooking times and vice versa.
• A small amount of food per preparation reduces cooking time - and vice versa.

Mirror stoves (with reflector)

The simplest mirror oven consists of a parabolic reflector and a pan stand located at the focal point of the oven. If the stove is exposed to the Sun, then sunlight is reflected from all the reflectors to the central point (focus), heating the pan. The reflector may be a paraboloid made, for example, of sheet steel or reflective foil. The reflecting surface is usually made of polished aluminum, mirror metal or plastic, but may also consist of a number of small flat mirrors attached to the inner surface of the paraboloid. Depending on the desired focal length, the reflector can take the form of a deep bowl into which the pan of food is completely immersed (short focal length, the dishes are protected from the wind) or a shallow plate if the pan is installed at a focal point at a certain distance from the reflector.

All reflective stoves use only direct solar radiation, and therefore must constantly turn towards the Sun. This complicates their operation, as it makes the user dependent on the weather and the control device.

Advantages of mirror stoves:

• The ability to reach high temperatures and, accordingly, fast cooking.
• Relatively inexpensive models.
• Some of them can also be used for baking.

These advantages also come with some disadvantages:

• Depending on the focal length, the oven should rotate behind the Sun approximately every 15 minutes.
• Only direct radiation is used, and diffuse sunlight is lost.
• Even with little cloudiness, large heat losses are possible.
• Handling such a stove requires a certain skill and understanding of the principles of its operation.
• The radiation reflected by the reflector is very bright, blinds the eyes, and can lead to burns upon contact with the focal spot.
• Cooking is limited to daytime hours.
• The cook has to work in the hot sun (except for fixed focus ovens).
• The efficiency of the stove is highly dependent on the changing strength and direction of the wind.
• A dish prepared during the day cools down in the evening.

The difficulty of handling these ovens, coupled with the fact that the cook is forced to stand in the sun, is the main reason for their lack of popularity. But in China, where cooking traditionally requires high heat and power, they are widespread.

Thermal power

The thermal output of a solar oven is determined by the amount of solar radiation, the working absorption surface of the oven (usually between 0.25 m2 and 2 m2) and its thermal efficiency (usually 20-50%). The table compares typical area, efficiency and power values ​​for a box oven and a reflector oven.

Standard values ​​for area, efficiency and productivity of box and reflector ovens

As a rule, reflective ovens have a much larger working surface than box ovens. Consequently, they are much more powerful and can boil more water, cook more food, or process comparable quantities in less time. On the other hand, their thermal efficiency is lower because the cookware is cooled by exposure to the atmosphere.

In tropical and subtropical countries you can count on clear weather and normal daily light almost all year round. Around noon, when the total solar irradiance reaches 1000 W/m2, it is quite realistic to count on a thermal power of 50-350 W, depending on the type and size of the stove. The amount of radiation in the morning and during the daytime hours is naturally lower and cannot be fully compensated by the sun tracking system.

By comparison, burning 1 kg of dry wood produces approximately 5000 watts multiplied by the thermal efficiency of the stove (15% for a primitive fireplace and 25-30% for an improved cookstove used in developing countries). The thermal power actually reaching the cookware is therefore 750-1500 W.

The amount of solar radiation decreases sharply when it is cloudy and during the rainy season. In conditions of lack of direct radiation, a solar oven is unsuitable for anything other than keeping cooked food warm. The weak point of solar ovens (regardless of their type) is that on cloudy and rainy days (2-4 months a year for most developing countries), food must be cooked using conventional means: wood, gas or kerosene burner.

Solar radiation and ovens

The main prerequisite for successful use of a solar oven is adequate lighting with few cloudy days throughout the year. The duration and intensity of solar radiation should allow the solar oven to be used for long periods. While in Central Europe solar cooking is possible on a sunny summer day, a minimum amount of solar energy of 1500 kWh/m2 per year is desirable for a solar oven (corresponding to an average daily insolation of 4 kWh/m2). But annual averages can sometimes be misleading. An essential condition for the suitability of a solar oven is stable summer weather, that is, regular, predictable periods of cloudless days.

Solar energy resources vary significantly from country to country, even within the tropical zone of third world countries. For example, solar radiation in most parts of India is considered very good in terms of solar energy utilization. The average amount of solar energy is between 5 and 7 kWh/m2 per day depending on the region. Over much of the country, light levels are at their lowest during the monsoon season and almost as low during December and January.

Kenya's climate and solar potential are favorable for the use of solar ovens. Kenya is located close to the equator and therefore has a tropical climate. In the capital Nairobi, the amount of solar energy ranges from 3.5 kWh/m2 per day in July to 6.5 kWh/m2 per day in February, and in other areas remains almost unchanged (6.0 - 6.5 kWh/m2 per day in Lodwar province). Solar radiation in Nairobi allows for solar cooking nine months of the year (except June-August). On the other hand, on cloudy or foggy days you have to rely on traditional fuels. However, in Lodwar province, solar ovens can be used all year round.

Solar ovens for developing countries

The purpose of using solar ovens is undoubtedly to save energy in the face of a double energy crisis: the crisis of the poor, which consists of an increasing shortage of firewood, and the crisis of the national energy sector - the increasing pressure on its balance of payments.

Compared to other countries, developing countries consume very little energy. For example, the rate of energy consumption per capita in India in 1982 - 7325 GJ - was one of the lowest in the world. But the country's energy consumption is growing almost twice as fast as its gross national product. The same thing is happening in other developing countries.

Most residents of developing countries obtain the bulk of their energy consumption from non-commercial sources: from traditional local energy resources, through their manual labor. They simply cannot afford to buy the amount of commercially produced energy they need.

The logical consequence of this is a relative shortage of fuel for the poor, whose standard of living is further deteriorated as a result. Solar ovens are a step towards improving their living conditions.

Of all the "poor majority" of third world countries, solar ovens should be primarily used by the rural population.

How much energy does it take to cook food?

The daily fuel requirement depends on the type of food being prepared and the quantity. A resident of a developing country burns, on average, 1 ton of wood per year. A typical Indian family needs 3-7 kg of firewood per day; in cooler regions, the daily amount of firewood for one family is almost 20 kg in winter and 14 kg in summer. In southern Mali, the average family (consisting of 15 people) burns about 15 kg of firewood per day. A study conducted in an Afghan refugee camp in Pakistan found that the daily firewood requirement there was up to 19 kg per family. More than half of the firewood in a typical household is used for baking bread, the rest for cooking other foods. In winter, naturally, more firewood is required.

Although the amount of energy required for cooking varies, solar ovens provide significant energy savings. The primary goal of solar ovens is to reduce the need for wood, which is still the most important fuel for cooking. The problem is that wood is inexpensive compared to kerosene, bottled gas and electricity. Increasing uncontrolled cutting of trees for own use and for sale is the main cause of forest loss, expansion of deserts, soil erosion, decline in groundwater levels, and has long-term adverse effects on the ecological balance. Pakistan's meager forest remnants and rampant deforestation in Kenya are proof that fears are not exaggerated.

Overall, solar ovens are unlikely to contribute much to the national energy mix. However, they can very significantly improve the living conditions of the poor and help them overcome their personal energy crisis.

Solar ovens come in different shapes and sizes. Here are a few examples: oven, concentrator oven, reflector, solar steamer, etc. With all the variety of models, all stoves capture heat and hold it in a thermally insulated chamber. In most models, sunlight directly affects the food.