A great craft for the summer is to make a miniature refrigerator with low-voltage power. A variety of supply voltages (220 V, 12 V, 5 V) makes it possible to use such a refrigerator almost anywhere: in the car, office, home, etc. This is a great thing to cool drinks on a hot summer day.
Will need
Manufacturing a miniature refrigerator using a Peltier element
The case was made of arbitrary dimensions, taking into account the placement of the cooling unit, power supply and beverage chamber. It will consist of two sections: one for the technical part, the other for cooling products.We make the body. We mark a piece of hardboard using a pencil and ruler.
We cut out all the elements with a hacksaw.
All body parts are ready.
From the middle part dividing the refrigerator into two parts, we cut out a window for a radiator with a Peltier module.
We apply the cooling unit to the side of the case.
And we drill a lot of holes on both sides. That is, the air flow will enter from one side through the holes in the side. Pass through the radiator, picking up heat and exiting through the holes on the other side.
We paint all parts of the refrigerator body with aerosol paint from a can.
Let's start assembling.
Glue the separating part of the cooling block with hot glue.
We glue all parts of the body on both sides.
The cooling unit rests on a piece of wood that is glued to the base.
For illumination you will need two sections of 12 V LED strip. One color is white, the other is colored.
Screw on the small fan.
We divide the technical part of the refrigerator into two parts. The power source will be located at the top. The dividing wall is placed on square pieces of wooden slats glued to the sides.
Installing the back wall.
We will make the door from a piece of acrylic glass. Mark with a ruler and pencil.
You can buy miniature loops or make your own. Glue them on with instant glue.
We cover the sides of the acrylic glass with black self-adhesive tape.
Glue the handle to the door.
We will organize lighting. Solder the contacts to the mini limit switch.
Solder the wires to the pieces of LED strip. We glue the pieces themselves onto a mini shelf made from the same acrylic.
We connect the backlight, fans, Peltier element.
Install the switch on the side.
We isolate all open twists.
Close the compartment with the cooling unit. This must be done to prevent hot air from rising and heating the power source.
Drill a hole for the 220 V power cable.
To prevent the refrigerator door from opening, we will install small neodymium magnets from a broken sidir on the side.
We close the top cover, but before that we cut in the power switch and solder the wires. Now the refrigerator can be turned off with the button on top.
Close the lid and secure with glue.
For proper thermal insulation, we cover the inside of the refrigerator with thin foam plastic. We place the cut out foam panels on hot glue.
And finally, the result of the work is such that in thirty minutes the temperature inside the chamber dropped from 42 to 16 degrees Celsius. The drinks were cooled to a temperature of 20 degrees Celsius. And all this in 30 minutes!
Of course, the efficiency of such a refrigerator is much lower than that of a compressor, but it also has its advantages, one of which is low-voltage power supply, which can be not only 12 V but also 5 V! Naturally, it is quite possible to power it from a computer’s USB port, although the output will be lower than when powered by a voltage of 12 V.
The total power consumption when powered from a 220 V network is about 100 W. More detailed assembly instructions are in the video below.
It is best to make a car refrigerator with your own hands using Peltier elements. The design of such a refrigerator is much simpler than the usual unit with a compressor and freon as a refrigerant. Despite the fact that a compressor refrigerator has a higher efficiency than one operating based on the Peltier effect, the latter is preferable for use in cars. Since it has other important advantages: smaller dimensions and silent operation.
Compressor climate control technology is still used in cars, for example, air conditioning. This is explained by the fact that the air conditioner cools a large volume and cannot be made based on the Peltier effect. In addition, the air conditioner must remove heat from the car interior further than the design of the Peltier element allows. If you received an old home air conditioner, do not rush to rejoice, since it is unlikely that you will be able to turn it into a car refrigerator.
Cooling without compressor
The Peltier effect is that when an electric current flows through the contact of two semiconductors with different types of conductivity (p-n junction), depending on the direction of the current, it either cools or heats up. This is explained by the interaction of electrons with thermal vibrations of the atoms of the crystal lattice. And when current passes through series-connected junctions, the thermal energy absorbed by one p-n junction is released on the other.
If you arrange the Peltier element so that one p-n junction is inside a container with good thermal insulation, and the other outside, you will get a small refrigerator that is sufficiently powered by a car cigarette lighter. Another refrigerator that operates without a compressor is absorption. You can make a refrigerator for your car from such an old unit. But in this case, the design will depend on what you got, so you will definitely need to change the heaters and thermostats to 12 volt ones.
Making the body
To make the case you will need materials:
One Peltier element will not be able to significantly cool a large volume, so for one thermoelectric element do not make the housing larger than 40x40x30 cm.
To cut hardboard, use an electric jigsaw or circular saw; if you don’t have them in your arsenal, a regular hacksaw with a fine tooth will do. From MDF sheets, using corners and blind rivets, assemble a box that will be the body of your mini-fridge. Place the corners from the inside so that the rivets are held more securely. Fill all cavities in the joints between structural parts with sealant. After the sealant has dried, cover the inside surface of the resulting box with insulation. Use “liquid nails” for this.
Apply foam rubber seal to the upper ends of the walls. MDF is very hygroscopic, so it must be primed before gluing the body. Instead of a primer, dilute a little PVA with water (add 2 parts liquid to 1 part glue). Prime the body, let it dry and cover it with oilcloth. Do not tape the door, as it is a radiator, and tape will worsen its heat transfer.
Cooler installation
For this you will need:
First you need to make two radiators from aluminum, mount a cooling element between them and separate them from each other with a sheet of thermal insulation. This design will double as the refrigerator door. With the outer dimensions of the case being 40x40x30 cm, the top radiator should be 40x40 cm, since it will cover the box, and the bottom one should be 38x38 cm, because it should go inside. Cut a 38x38 cm square from a sheet of insulation, cut a hole in its center the size of the cooling element and glue it to the smaller radiator using “liquid nails”. Solder the power wires to the terminals of the element (the red terminal should be “+”, and the black terminal should be “ground”).
Attach the resulting door to the hinges, and them to the body so that when it closes, the smaller radiator fits inside the body. To remove the wires from the housing, place a piece of rubber tube of suitable diameter on them. 
In the top plate, next to the cooler power connection contacts, drill a hole slightly smaller than the outer diameter of the tube. Route the wires through it, leaving the tube in the hole so that the wire does not rub against its edges. Attach the fan to the door so that it points towards it and connect it to the same pair of wires. All that remains is to attach a latch and some kind of handle for carrying the device and the cold generator is ready.
Selecting wire cross-section
To find out the current consumed by the built air conditioner, add the rated current of the fan with the same parameter of the cooling element. After this, all that remains is to select from the directory the wire cross-section corresponding to this current. We provide below a fragment of the reference book sufficient to make a decision in this case. For connection lengths up to 2 m:
- current up to 1.5 A, wire cross-section - 0.3 mm 2;
- current - 2.5 A, cross-section - 0.5 mm 2;
- current – 3.5 A, wire – 0.7 squares;
- current - 7.5 A, wire 1.5 square;
- current – 10 A, wire – 2 mm 2.
With a connection length of 3 m:
- I nom up to 1.5 A, wire – 0.4 mm 2;
- I nom – 2.5 A, wire – 0.8 mm 2;
- I nom – 3.5 A, wire – 1.1 square;
- I nom - 7.5 A, cross-section - 2.3 mm 2;
- I nom – 10 A, cross-section – 3.2 square.
If your air conditioner draws more current than the cigarette lighter fuse is designed for, you will have to connect it to the battery terminals through its own fuse link. But you will save on the connector for connecting to the cigarette lighter socket.
The cross-section of a single-core wire S after measuring its diameter d can be calculated using the formula - S=π * (d/2) 2. To determine the cross-section of a stranded wire, you need to count the number of strands under the insulation, calculate the cross-section of one and multiply by their number.
If you don't have a caliper, you can determine the diameter of a single-core wire using a regular ruler. To do this, wind 10 turns of wire around a screwdriver, turn to turn, and measure the length of the resulting winding with a ruler. Divide the result by 10 to get the wire diameter.
Power Requirements
The device must be powered by a direct current voltage of no more than 15 V. Small ripples do not interfere with operation. This means that in special conditions a homemade air conditioner is not needed and can simply be connected to the on-board network of a car with 12 volt electrical equipment. For owners of cars with a 24 V on-board voltage, it is recommended to connect two cooling elements in series.
Advantages and disadvantages of thermoelectric cooling devices
Thermoelectric cooling air conditioner based on the Peltier effect has the following advantages: 
- High specific cooling power. With dimensions of 40x40x3.8 mm, one element can remove thermal energy with a power of up to 57 W.
- Quiet operation.
- Low cost. One element costs no more than $3.
- High reliability. The time of continuous operation before failure reaches 200 thousand hours.
Disadvantages of Peltier coolers:
- Low efficiency. Therefore, with a large cooled volume, it is difficult to achieve a significant temperature difference between opposite surfaces.
- The air conditioner consumes relatively more power. The current consumed by one element reaches 6 A.
- Part of the power consumption is spent on heating the radiator, which releases heat to the atmosphere.
A self-made refrigerator, of course, will not notice air conditioning or climate control, but in any case it will make traveling in hot weather easier.
While I was building a country house, I couldn’t help but think of another way to use extruded polystyrene foam. Today this is one of the most effective insulation materials with a huge number of advantages and a very affordable price. The first thing I realized was that for grocery shopping trips to the hypermarket it is very useful to have a thermos container in which you can safely transport frozen food. To make such a box it took 160 rubles and half an hour of free time. But I decided to go further and modify the design in order to use it as a stand-alone refrigerator.
Let's start making!
2. So, let's start with a thermos container. We will need one sheet of polystyrene foam with dimensions 1200x600 mm, thickness 50 mm, a stationery knife and a tape measure. The cost of such a sheet in any hardware store is 160 rubles. We cut the sheet according to the template, take the polyurethane foam and glue together such a container.
3. Here is a diagram for cutting the sheet. The sheet has sides 20 mm thick; they need to be cut off on all sides except the bottom. The sheets are glued together with polyurethane foam. The technology is simple. Apply a little foam to the gluing area, wait 1 minute, press the sheets tightly against each other and then manually control for 5 minutes so that they do not move due to the expansion of the foam. The main thing is not to leave it unattended. Only a small piece of polystyrene foam will be left over, marked in gray in the diagram.
4. Pay attention to the design of the cover; I cut one of the large sheets from the diagram above into 3 parts in place when gluing it together to ensure a tight fit. After this, the outside of the box can be painted. The paint slightly corrodes the polystyrene foam, so it is better to paint in two stages. The resulting container weighs 820 grams and has incredible heat loss performance. You can put several kilograms of frozen food in such a box and transport it for several hours without any problems. The main thing is not to mix frozen and chilled foods. You can supplement the design with a cold accumulator.
5. Or you can modify the design to get a full-fledged refrigerator. For these purposes, we will use a Peltier element - a thermoelectric converter, the operating principle of which is based on the occurrence of a temperature difference when an electric current flows. These are the elements that are used in serial car refrigerators, as well as ventilated car seats.
The cost of one Pelte element with a maximum power of 60 W on aliexpress is 130-150 rubles. Model TEC1-12706. During operation, one side of the element heats up, the other cools. To prevent the element from burning, it is necessary to intensively remove heat from the hot side. To do this, we need a processor cooler with a radiator from a computer store, costing 250 rubles. To improve air circulation inside the refrigerator compartment and prevent the radiator from freezing, I decided to install fans on both sides. We will also need a thermostat with an external temperature sensor and a relay, costing 170 rubles, which will allow us to control the set temperature inside the container. Well, an extension cable with a connector for a car cigarette lighter for 100 rubles.
So, let's start assembling.
6. We install the Peltier element using thermal paste (included with the cooler) between two aluminum radiators. It is worth noting here that the temperature gradient of the installation can be increased by assembling 2 or 3 Peltier elements installed in series. Thus, so that one Peltier element cools the other. In this option, it is possible to get a negative temperature of up to -18 degrees Celsius in the container. We lay a piece of foam thermal insulation along the perimeter between the element.
7. We connect the radiators to each other with standard mounting plates to the motherboard, connecting them using plastic clamps. This also allows the cold and hot sides to be thermally isolated from each other. Test run of installation. The more intensely we cool the hot side, the lower the temperature on the cold side will be. Here the fans are aimed at supplying air to the radiators; this is less efficient than if they are turned over to blow them out. In the improvised box, we managed to achieve a temperature of -3 degrees, at an ambient temperature of +26. The photo clearly shows the model of the coolers; their advantage is the large area of the radiator support area. And as a thermal insulation pad, I used a piece of thermal insulation for round pipes.
8. Now let's integrate the thermoelectric converter into the new container lid. For the convenience of placing the entire structure, we will increase the thickness of the cover to 100 mm (2 sheets of polystyrene foam). This photo clearly shows the perimeter gasket between the two radiators.
9. Artistic cutting on polystyrene foam and sandpaper processing. Let's paint again. After painting, the outer shell of polystyrene foam becomes stronger.
10. Coat the seams with sealant, turn both fans over to blow out. Among the potential improvements, it might be worth reducing the fan speed on the cold side (currently both fans operate at maximum speed).
11. We install the thermostat board next to the case and fix the power wire in this simple way. First we press the plate using self-tapping screws, then fix it with sealant.
12. Container assembled. The weight of the container without a lid is 800 grams; the lid with the assembled thermoelectric converter weighs the same. Total expenses - 1000 rubles and a couple of hours of time. Tests with cooled products in the trunk of a car showed the system’s ability to maintain the temperature at the bottom (!) of the container within +5 degrees Celsius, at an ambient temperature of +29 degrees (yes, it is much warmer in the trunk, even with the air conditioner running) and current consumption - 3 Ampere. I think this is an excellent result.
I plan to make the next container from 3 Peltier elements installed in series to get a full-fledged freezer.
Those who are planning to go to the sea this summer should know that it is better to store food and drinks in a cool place so that they do not spoil. And there is no better place than a refrigerator.
Not everyone wants to buy a car refrigerator for four thousand rubles. Therefore, many people who want to relax by the sea decide to create a new car refrigerator with their own hands, which contains “cold accumulators”, which are frozen one and a half liter bottles with coolant “water”. Even a refrigerator made from packaging cardboard can last a considerable number of trips to southern resorts. You can read about how to make a car refrigerator with your own hands in this article.
To create such a solution, we select refrigerator dimensions in the area of 40x40x30 cm, which, however, can be varied depending on the dimensions of the car trunk. For average cars, this size is better, since a refrigerator that is too large would take up a lot of space, and there would be no place to put things.
Insulation, namely thermal insulation using foam insulation with foil on one side, should have a thickness of ten millimeters. Width 1.2 meter, length 1 meter. The price tag is currently 90 rubles per meter. The body materials used are furniture waste, or, to be more precise, ten-millimeter fiberboard. Buy two aluminum corners 1.5×1.5 mm for 120 rubles. Blind rivets of the 4×16 type are purchased “one hundred pieces for 50 rubles” and a pair of furniture hinges for 30 rubles each. Total expenses can be about 300 rubles.
Tools and other equipment will also be useful in manufacturing.
We cut off the corners in place and without stress we begin to make the frame of the future box.
The result of titanic work should be a quite presentable box. A lock with a latch and a folding wire handle can be placed on the lid of the box. Thus, the finished unit with packaged food can be carried in your hand with peace of mind. Being filled with liquid and food, it becomes very, very weighty!
Now it’s time to start covering the object of the article with insulation. The bottom and lid, as an option, can be pasted over in two layers, and the walls in one layer. To do this, you can resort to liquid nails. Spread the workpiece with this product, stick it to the walls and then press it with a weight. All this should stick without any problems and quite successfully, you can later try to tear off the material a little, but it will be very, very good. As a result, after three days in your free time, a rather nice unit will come out, equipped with a hinged top cover with a latch.
Four 1.5 liters will be attached or placed in the corners or at the bottom. bottles of liquid, or from six to eight 0.5 each, previously stored in the freezer. You can also resort to cool mineral water, including carbonated water, which will come in handy on a hot summer day. Mineral water is best suited for 0.5 liters, such volumes are the most practical. Containers with water are not filled completely, otherwise, after the water freezes, the ice will damage the bottle due to expansion, and the food will have to float in the defrosted water. You can save space in the unit by purchasing branded “cold accumulators” from the store. They come in the form of special bags or flat boxes with water inside, which take the place of bottles. Such boxes can be purchased from 120 rubles.
But in the case of vessels with spring water, everything is much more profitable. Even if the liquid in them thaws “usually after 24 hours,” it can be used to wash your face or simply drink.
Using the cardboard refrigerator described above, all contents not eaten or drunk along the way will reach the resort cold.
This unit can be used even as a stool. You should not rush to paint the unit, because if something happens to the wood fiber board, “for example, it will warp from the liquid.”
The refrigerator is able to fully justify the hours spent on it and the small investment in production. The benefits of such a decision will be very great.
To create another option, you need to buy a box for children's toys for three hundred and fifty rubles. You should also choose a couple of sheets of polystyrene foam for a total of one hundred rubles, a couple of rolls of metallized adhesive tape, universal glue for eighty, you will also have to resort to mounting foam for 120 rubles. All the necessary material is unlikely to exceed the amount of 900 rubles.
The entire work will take two and a half hours of your time.
Any of the elements must be placed on the lid, since installation will proceed much easier and the cold will drop.
Elements - the more there are, the better, since they affect cooling.
Either alligator clips or T-type sockets are used. In this case, the cigarette lighter will not provide the required area. You can use a monoblock radiator.
It is thinner, but at the same time it is characterized by greater width, and in some cases you can take options with copper.