Do-it-yourself car refrigerator on Pelte elements
While I was building country house I had a desire to think of another way to use extruded polystyrene foam. Today it is one of the most effective heaters with a huge number of advantages and 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.
It took 160 rubles and half an hour of free time to make such a box. But I decided to go further and refine the design in order to use it as a stand-alone refrigerator.
Let's start making!
So, let's start with the thermos container. We need one sheet of expanded polystyrene with dimensions of 1200x600 mm, a thickness of 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 mounting foam and glue such a container.
Here is the sheet layout. The sheet has sides 20 mm thick, they need to be cut off from all sides except the bottom. Sheets are glued together mounting 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 foam expansion. The main thing is not to leave unattended. Only a small piece of polystyrene foam will remain, marked in gray in the diagram.
Pay attention to the design of the lid, I cut one of the large sheets from the diagram above into 3 parts in place when gluing to ensure a tight fit. After that, the outside of the box can be painted. The paint corrodes the polystyrene foam a little, so it is better to paint in two stages. The resulting container weighs 820 grams and has incredible heat loss performance. In such a box, you can put several kilograms of frozen food and transport them without problems for several hours. The main thing is not to mix frozen and chilled foods. It is possible to supplement the design with a cold accumulator.
Or you can modify the design to get a full-fledged refrigerator. For these purposes, we will use the Peltier element - a thermoelectric converter, the principle of operation of which is based on the occurrence of a temperature difference when an electric current flows. It is these elements that are used in serial car refrigerators, as well as car seats with ventilation.
The cost of one Pelte element with a maximum power of 60 watts on aliexpress is 130-150 rubles. Model TEC1-12706. During operation, one side of the element heats up, the other side cools down. so that the element does not burn out, it is required to intensively remove heat from the hot side. To do this, we need a processor cooler with a heatsink from a computer store, costing 250 rubles. To improve air circulation inside the refrigerator compartment and prevent freezing of the radiator, 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 cord with a connector for a car cigarette lighter for 100 rubles.
So, let's start assembling.
The Peltier element using thermal paste (comes with the cooler) is installed between two aluminum radiators. It is worth noting here that it is possible to increase the temperature gradient of the installation by assembling 2 or 3 Peltier elements installed in series. So that one Peltier element cools the other. In this embodiment, it is realistic to get a negative temperature in the container up to -18 degrees Celsius. Along the perimeter between the element we lay a piece of foamed thermal insulation.
We connect the radiators to each other with standard mounting plates to the motherboard, connecting them with plastic clamps. This also makes it possible to thermally isolate the cold and hot sides from each other. Trial run of the installation. The more intensively we cool the hot side, the lower the temperature on the cold side will be. Here, the fans are directed to the flow of air to the radiators, this is less efficient than if they are turned over to blow out. In an impromptu box, it was possible 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 in the large area of the radiator support pad. And as a heat-insulating gasket, I used a piece of heat-insulation for round pipes.
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 expanded polystyrene). This photo clearly shows the perimeter gasket between the two radiators.
Artistic cutting on polystyrene foam and processing with sandpaper. We paint again. After painting, the outer shell of the expanded polystyrene becomes stronger.
We coat the seams with sealant, turn both fans over to blow. Of the potential improvements, it may be worth lowering the fan speed on the cold side (now both fans are running at maximum speed).
Next to the case, we install the thermostat board and fix the power wire in such an unpretentious way. First, we press the plate with self-tapping screws, then we fix it with sealant.
Container assembled. The weight of the container without a lid is 800 grams, the lid with the assembled thermoelectric converter weighs the same. General expenses - 1000 rubles and a couple of hours of time. Tests with chilled 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's much warmer in the trunk, even when the air conditioner is on) and current consumption - 3 Ampere. I think this is an excellent result.
I plan to make the next container from 3 sequentially installed Peltier elements in order to get a full-fledged freezer.
In 1834, the French physicist Jean Charles Peltier, investigating the effect of electricity on conductors, discovered a very interesting effect. If a current is passed through two dissimilar conductors located in close proximity to each other, then one of these conductors begins to heat up strongly, and the second, on the contrary, cools down strongly. The amount of heat generated and absorbed directly depends on the strength and direction of the electric current. If you change the direction of the current, then the cold and hot sides will change places. A little later, this phenomenon was called the Peltier effect and was safely forgotten due to the practical lack of demand at that time.
And only after more than a hundred years, with the rise of the semiconductor era, there is an urgent need for compact, inexpensive and efficient coolers. So, in the 60s of the 20th century, the first semiconductor thermoelectric modules appeared, which were called Peltier elements.
The basis of any thermoelectric module is the fact that different conductors have different levels of electron energy. In other words, one conductor can be represented as a high-energy region, the second conductor as a low-energy region. When two conductive materials come into contact, during the passage of an electric current through them, an electron from a low-energy region must go to a high-energy region.
This will not happen if the electron does not acquire the required amount of energy. At the moment of absorption of this energy by an electron, the place of contact of two conductors is cooled. If you change the direction of current flow, on the contrary, the effect of heating the contact point will occur.
Any conductors can be used, but this effect becomes physically noticeable and significant only when semiconductors are used. For example, when metals are in contact, the Peltier effect is so insignificant that it is practically invisible against the background of ohmic heating.
TEM - a set of similar thermocouples connected to each other in series. All thermocouples are located between two ceramic plates. Peltier plate. The plates are made of nitride or aluminum oxide. Directly the number of thermocouples in one element can vary within a very wide range, from a few pieces to several hundreds or thousands.
In other words, Peltier elements can be of absolutely any power, from hundredths to several hundreds or thousands of watts. A direct current passes through all thermocouples in series and as a result, the upper ceramic plate is cooled, while the lower one, on the contrary, is heated. If you change the direction of the current, then the plates will change places, the upper one will start to heat up, and the lower one will cool.
There is one feature in the operation of the element that is actively used to enhance the cooling efficiency of this device. As you know, when current is passed through a Peltier element, a temperature difference arises between the surface that is heated and the surface that is cooling. So, if the surface that is actively heated is subjected to forced cooling. For example, with the help of a special cooler, this will lead to even stronger cooling of the surface, that is, the one that is being cooled. In this case, the temperature difference with the surrounding air can reach several tens of degrees.
Advantages and disadvantages
Like anyone technical device, for thermoelectric module has its advantages and disadvantages:
Problem increase efficiency for TEMs it runs into an unsolvable yet technical puzzle. Free electrons have, in fact, a dual nature, which manifests itself in practice and they are simultaneously carriers of both electric current and thermal energy. As a consequence, a highly efficient Peltier element must be made from a material that simultaneously has two mutually exclusive properties. This material should conduct electricity well and conduct heat poorly. So far, such material does not exist in nature, but scientists are actively working in this direction.
All thermoelectric modules have the corresponding technical characteristics:
Application of TEMs
Despite a serious drawback inherent in all Peltier elements without exception, namely, a very low efficiency, these devices have found quite a wide application both in science and technology, and in everyday life.
Thermoelectric modules are important design elements of such devices as:
Peltier element in the hands of a home master
It is necessary to make a reservation right away, independent manufacturing of a thermoelectric element is at least a meaningless and useless task. Unless the manufacturer is a student of the seventh grade and does not consolidate the knowledge gained in physics lessons in this way.
Much easier to buy new thermoelectric element in the respective store. Fortunately, they are inexpensive and there is no shortage in choosing a specific model. And besides that there is nothing to break or wear out in them, any thermoelement removed from an old computer or car air conditioner will not differ in its technical characteristics from a new one.
The thermocouple model is the most popular: TEC1-12706. The dimensions of this device are 40 by 40 millimeters. It consists of 127 thermocouples connected in series. Designed for a current of 5 A, with a circuit voltage of 12 V. Such an element costs an average of 200 to 300 rubles. But you can find it for a hundred, or, in general, for so much, if you remove it from an old computer or some other unnecessary device.
With the help of such an element, you can make at least two very interesting and useful devices in the household.
How to make a refrigerator with your own hands
The production of portable refrigerators, in particular for cars, is entirely based on the Peltier effect. To make such a device at home, you will need:
- Thermoelement brand TEC1-12706. It costs 200 rubles in the nearest store (specialized).
- Radiator and fan. They are taken from an old computer that has served its purpose.
- Container. Any unnecessary container made of plastic, metal or wood. Outside and inside, such a container is pasted over with heat-saving plates made of polystyrene foam or expanded polystyrene.
The thermoelectric module is built into the container lid. In this case, the flow of cold will occur from top to bottom, which will lead to uniform cooling of the container. From the inside of the container, a radiator is attached to its lid with the help of thermal paste and fixing bolts.
In order to increase the power of the future refrigeration device, it is possible to increase the number of thermoelements, up to two or three or more. In this case, the modules are glued to each other, observing the polarity. In other words, the hot side of the underlying element is in contact with the cold side of the overlying element.
Outside, another radiator is attached to the lid along with a computer cooler. In the place where the radiators are fastened, there must be good thermal insulation between the cold - internal and hot - external parties. It is necessary to very carefully tighten the upper and lower radiators with fixing bolts so that the ceramic plates of the thermoelements located between them do not crack.
Electricity is connected using a power supply, which can be taken from an old computer.
Portable thermoelectric generator
Such a mini-power plant can really help out a tourist or a hunter when the batteries of all electronic gadgets run out in the forest. It is very romantic in this situation to take a few dry chips and cones, build a small fire and use it to charge the discharged batteries, and at the same time cook food. This is what makes it possible to make a portable thermogenerator built on a thermoelement.
To build this miracle device, you need a portable camping stove that runs on any type of fuel. IN last resort even a small candle or a tablet of dry alcohol will do.
A fire is made in the stove, and a thermoelectric module is attached to it from the outside with the help of thermal paste. By means of wires, it is connected to a voltage converter.
The value of the received current will directly depend on the temperature difference between the cold and hot sides of the thermoelement. For effective operation, a difference between the cold and hot surface of at least 100 degrees is required.
In this case, it must be understood that the maximum temperature is limited by the melting temperature of the solder with which the module itself is made. Therefore, for such devices, special thermal modules are used, which are made using a special refractory solder. In conventional modules, the melting temperature of solder is 150 degrees. In refractory modules, the solder begins to melt at a temperature of 300 degrees.
While I was engaged in the construction of a country house, the desire to think of another way to use extruded polystyrene foam did not leave me. Today it is one of the most effective heaters 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. It took 160 rubles and half an hour of free time to make such a box. But I decided to go further and refine 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 need one sheet of expanded polystyrene with dimensions of 1200x600 mm, a thickness of 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 mounting foam and glue such a container.
3. Here is a sheet cutting scheme. The sheet has sides 20 mm thick, they need to be cut off from all sides except the bottom. Between themselves, the sheets are glued together with mounting 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 foam expansion. The main thing is not to leave unattended. Only a small piece of polystyrene foam will remain, marked in gray in the diagram.
4. Pay attention to the design of the lid, I cut one of the large sheets from the diagram above into 3 parts in place when gluing to ensure tight fixation. After that, the outside of the box can be painted. The paint corrodes the polystyrene foam a little, so it is better to paint in two stages. The resulting container weighs 820 grams and has incredible heat loss performance. In such a box, you can put several kilograms of frozen food and transport them without problems for several hours. The main thing is not to mix frozen and chilled foods. It is possible to 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 the Peltier element - a thermoelectric converter, the principle of operation of which is based on the occurrence of a temperature difference when an electric current flows. It is these elements that are used in serial car refrigerators, as well as car seats with ventilation.
The cost of one Pelte element with a maximum power of 60 watts on aliexpress is 130-150 rubles. Model TEC1-12706. During operation, one side of the element heats up, the other side cools down. so that the element does not burn out, it is required to intensively remove heat from the hot side. To do this, we need a processor cooler with a heatsink from a computer store, costing 250 rubles. To improve air circulation inside the refrigerator compartment and prevent freezing of the radiator, 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 cord with a connector for a car cigarette lighter for 100 rubles.
So, let's start assembling.
6. Install the Peltier element using thermal paste (included with the cooler) between two aluminum radiators. It is worth noting here that it is possible to increase the temperature gradient of the installation by assembling 2 or 3 Peltier elements installed in series. So that one Peltier element cools the other. In this embodiment, it is realistic to get a negative temperature in the container up to -18 degrees Celsius. Along the perimeter between the element we lay a piece of foamed thermal insulation.
7. We connect the radiators to each other with standard mounting plates to the motherboard, connecting them with plastic clamps. This also makes it possible to thermally isolate the cold and hot sides from each other. Trial run of the installation. The more intensively we cool the hot side, the lower the temperature on the cold side will be. Here, the fans are directed to the flow of air to the radiators, this is less efficient than if they are turned over to blow out. In an impromptu box, it was possible 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 in the large area of the radiator support pad. And as a heat-insulating gasket, I used a piece of heat-insulation for round pipes.
8. Now let's integrate the thermoelectric converter into the new lid for the container. For the convenience of placing the entire structure, we will increase the thickness of the cover to 100 mm (2 sheets of expanded polystyrene). This photo clearly shows the perimeter gasket between the two radiators.
9. Artistic cutting on polystyrene foam and sanding. We paint again. After painting, the outer shell of the expanded polystyrene becomes stronger.
10. We coat the seams with sealant, turn both fans over for blowing. Of the potential improvements - it may be worth reducing the fan speed on the cold side (now both fans are running at maximum speed).
11. Next to the case, we install the thermostat board and fix the power wire in such an unpretentious way. First, we press the plate with self-tapping screws, then we fix it with sealant.
12. Container assembly. The weight of the container without the lid is 800 grams, the lid with the assembled thermoelectric converter weighs the same. General expenses - 1000 rubles and a couple of hours of time. Tests with refrigerated 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's much warmer in the trunk, even when the air conditioner is on) and current consumption - 3 Ampere. I think this is an excellent result.
I plan to make the next container from 3 sequentially installed Peltier elements in order to get a full-fledged freezer.
Do car refrigerator do-it-yourself is best on Peltier elements. The device of such a refrigerator is much simpler than the unit we are used to with a compressor and freon as a refrigerant. Despite the fact that the compressor refrigerator has a higher efficiency than the one based on the Peltier effect, the latter is preferable to use in cars. Since it has other important advantages: smaller dimensions and silent operation.
Compressor climate 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 passenger compartment further than the design of the Peltier element allows. If you got an old home air conditioner, do not rush to rejoice, as you are unlikely to be able to make a car refrigerator out of it.
Refrigeration without compressor
The Peltier effect lies in the fact 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 another.
If you place the Peltier element so that one p-n junction is inside a container with good thermal insulation, and the other is outside, you get a small refrigerator that has enough power from a car cigarette lighter. Another refrigerator that works without a compressor is an absorption refrigerator. You can make a refrigerator in the 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
For the manufacture of 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 case larger than 40×40×30 cm.
To cut hardboard, use an electric jigsaw or circular saw, if they are not in your arsenal, an ordinary hacksaw with a small tooth will do. From MDF sheets, using corners and rivets, assemble a box that will be the body of your mini-refrigerator. Place the corners on the inside so that the rivets are held more securely. Fill all cavities in the joints between structural parts with sealant. After the sealant dries, glue the inner surface of the resulting box with a heater. Use "liquid nails" for this.
Stick a foam seal on the upper ends of the walls. MDF is very hygroscopic, so it must be primed before pasting the body. Instead of a primer, dilute a little PVA with water (add 2 parts liquid to 1 part glue). Prime the case, let it dry and cover it with oilcloth. Do not paste over the door, as it is a radiator, and pasting will impair 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 be part-time refrigerator door. With external dimensions of the case 40x40x30 cm, the upper radiator should be 40x40 cm, as it will cover the box, and the lower one 38x38 cm, because it must go inside. Cut a 38×38 cm square from the insulation sheet, cut a hole in its center according to 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 (you need to apply “+” to the red output, and “ground” to the black one).
Attach the resulting door to the hinges, and them to the case in such a way that when it closes, the smaller radiator enters the inside of the case. To bring the wires out of the housing, put a piece of rubber tube of a suitable diameter on them. 
Drill a hole slightly smaller than the outside diameter of the tube in the top plate next to the cooler's power connection pins. Pull 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, facing it, and connect it to the same pair of wires. It remains to attach the latch and some kind of handle for carrying the device and the cold generator is ready.
Wire section selection
To find out the current that the built air conditioner consumes, add the rated current of the fan with the same parameter of the cooling element. After that, it remains only to select from the directory the wire section corresponding to this current. A fragment of the reference book sufficient for making a decision in this case is given below. 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 squares;
- I nom - 7.5 A, cross section - 2.3 mm 2;
- I nom - 10 A, cross section - 3.2 squares.
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. 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 by the formula - S \u003d π * (d / 2) 2. To determine the cross section of a stranded wire, you need to count the number of veins under the insulation, calculate the cross section of one and multiply by their number.
If you do not have a caliper, you can determine the diameter of a solid wire using a regular ruler. To do this, wind 10 turns of wire round to round on a screwdriver and measure the length of the resulting winding with a ruler. Divide the result by 10 to get the diameter of the wire.
Power requirements
The power supply of the device must be a direct current voltage of no more than 15 V. Small ripples do not interfere with operation. This means that a home-made air conditioner does not need special conditions and it can simply be connected to the on-board network of a car with 12 volt electrical equipment. For owners of vehicles with an on-board network voltage of 24 V, it is recommended to connect two cooling elements in series.
Advantages and disadvantages of thermoelectric cooling devices
The thermoelectric refrigeration air conditioner based on the Peltier effect has the following advantages: 
- High specific cooling capacity. With dimensions of 40×40×3.8 mm, one element can remove heat energy up to 57 watts.
- Quiet operation.
- Low cost. One item 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 a relatively large amount of power. The current consumed by one element reaches 6 A.
- Part of the power consumed is spent on heating the radiator, which gives off heat to the atmosphere.
A self-made refrigerator, of course, will not notice the air conditioning or climate control, but in any case it will make it easier to travel in hot weather.
Peltier semiconductor refrigerators
The operation of modern high-performance electronic components that form the basis of computers is accompanied by significant heat dissipation, especially when they are operated in forced overclocking modes. Efficient operation of such components requires adequate cooling means to ensure the necessary temperature conditions for their operation. As a rule, such means of supporting optimal temperature conditions are coolers based on traditional heatsinks and fans.
The reliability and performance of such tools are continuously increasing due to the improvement of their design, use the latest technologies and the use of various sensors and controls in their composition. This makes it possible to integrate such tools into computer systems, providing diagnostics and control of their operation in order to achieve the greatest efficiency while ensuring optimal temperature conditions for the operation of computer elements, which increases reliability and extends their trouble-free operation.
The parameters of traditional coolers are constantly improving, however, in Lately such specific means of cooling electronic elements as Peltier semiconductor refrigerators appeared on the computer market and soon became popular (although the word cooler is often used, but the correct term in the case of Peltier elements is precisely the refrigerator).
Peltier refrigerators, containing special semiconductor thermoelectric modules, whose operation is based on the Peltier effect, discovered back in 1834, are extremely promising cooling devices. Such tools have been successfully used for many years in various fields of science and technology.
In the sixties and seventies, the domestic industry made repeated attempts to produce household small-sized refrigerators, the operation of which was based on the Peltier effect. However, the imperfection of existing technologies, low values of the coefficient useful action and high prices did not allow such devices to leave the research laboratories and test benches at that time.
But the Peltier effect and thermoelectric modules did not remain the lot of scientists alone. In the process of improving technologies, many negative phenomena have been significantly reduced. As a result of these efforts, highly efficient and reliable semiconductor modules have been created.
In recent years, these modules, whose operation is based on the Peltier effect, have been actively used to cool various electronic components of computers. In particular, they began to be used to cool modern powerful processors, the operation of which is accompanied by a high level of heat dissipation.
Thanks to its unique thermal and operational properties devices created on the basis of thermoelectric modules - Peltier modules, make it possible to achieve the required level of cooling of computer elements without special technical difficulties and financial costs. As coolers of electronic components, these means of maintaining the necessary temperature conditions for their operation are extremely promising. They are compact, convenient, reliable and have a very high work efficiency.
Especially big interest semiconductor refrigerators are presented as a means of providing intensive cooling in computer systems, the elements of which are installed and operated in hard forced modes. The use of such modes - overclocking (overclocking) often provides a significant increase in the performance of the electronic components used, and, consequently, as a rule, the entire computer system. However, the operation of computer components in such modes is characterized by significant heat dissipation and is often at the limit of the capabilities of computer architectures, as well as existing and used microelectronic technologies. Such computer components, the operation of which is accompanied by high heat dissipation, are not only high-performance processors, but also elements of modern high-performance video adapters, and in some cases, memory module chips. Such powerful elements require intensive cooling for their correct operation even in normal modes and even more so in overclocking modes.
Peltier modules
Peltier refrigerators use a conventional, so-called thermoelectric refrigerator, the operation of which is based on the Peltier effect. This effect is named after the French watchmaker Peltier (1785-1845), who made his discovery more than a century and a half ago - in 1834.
Peltier himself did not quite understand the essence of the phenomenon he discovered. The true meaning of the phenomenon was established a few years later in 1838 by Lenz (1804-1865).
In the recess at the junction of two rods of bismuth and antimony, Lenz placed a drop of water. When an electric current is passed in one direction, a drop of water freezes. When current was passed in the opposite direction, the resulting ice melted. Thus, it was found that when passing through the contact of two conductors of electric current, depending on the direction of the latter, in addition to the Joule heat, it is released or absorbed additional heat, which is called the Peltier heat. This phenomenon is called the Peltier phenomenon (Peltier effect). Thus, it is the reverse of the Seebeck phenomenon.
If in a closed circuit consisting of several metals or semiconductors, the temperatures at the contact points of the metals or semiconductors are different, then an electric current appears in the circuit. This phenomenon of thermoelectric current was discovered in 1821 by the German physicist Seebeck (1770-1831).
Unlike the Joule-Lenz heat, which is proportional to the square of the current (Q=R·I·I·t), the Peltier heat is proportional to the first power of the current and changes sign when the direction of the latter changes. The Peltier heat, as experimental studies have shown, can be expressed by the formula:
Qp = P q
where q is the amount of electricity passed (q=I t), P is the so-called Peltier coefficient, the value of which depends on the nature of the contacting materials and their temperature.
The Peltier heat Qp is considered positive if it is released and negative if it is absorbed.
Rice. 1. Scheme of the experiment for measuring the Peltier heat, Cu - copper, Bi - bismuth.
In the presented scheme of the Peltier heat measurement experiment, with the same resistance of the wires R (Cu + Bi) lowered into the calorimeters, the same Joule heat will be released in each calorimeter, namely, Q = R I I I t. Peltier heat, on the other hand, will be positive in one calorimeter and negative in another. In accordance with this scheme, it is possible to measure the Peltier heat and calculate the values of the Peltier coefficients for different pairs of conductors.
It should be noted that the Peltier coefficient is strongly dependent on temperature. Some values of the Peltier coefficient for various pairs of metals are presented in the table.
| Peltier coefficient values for various metal pairs | |||||
|---|---|---|---|---|---|
| iron constantan | Copper-nickel | Lead-constantan | |||
| T, K | P, mV | T, K | P, mV | T, K | P, mV |
| 273 | 13,0 | 292 | 8,0 | 293 | 8,7 |
| 299 | 15,0 | 328 | 9,0 | 383 | 11,8 |
| 403 | 19,0 | 478 | 10,3 | 508 | 16,0 |
| 513 | 26,0 | 563 | 8,6 | 578 | 18,7 |
| 593 | 34,0 | 613 | 8,0 | 633 | 20,6 |
| 833 | 52,0 | 718 | 10,0 | 713 | 23,4 |
The Peltier coefficient, which is an important technical specification materials, as a rule, is not measured, but calculated through the Thomson coefficient:
P = a T
where P is the Peltier coefficient, a is the Thomson coefficient, T is the absolute temperature.
The discovery of the Peltier effect had a great influence on the subsequent development of physics, and later on various fields of technology.
So, the essence of the open effect is as follows: when an electric current passes through the contact of two conductors made of various materials, depending on its direction, in addition to the Joule heat, additional heat is released or absorbed, which is called the Peltier heat. The degree of manifestation of this effect largely depends on the materials of the selected conductors and the electrical modes used.
The classical theory explains the Peltier phenomenon by the fact that electrons carried by current from one metal to another are accelerated or slowed down by the internal contact potential difference between the metals. In the first case, the kinetic energy of the electrons increases and then is released in the form of heat. In the second case, the kinetic energy of the electrons decreases, and this loss of energy is replenished due to thermal vibrations of the atoms of the second conductor. The result is cooling. A more complete theory does not take into account the change in potential energy during the transfer of an electron from one metal to another, but the change in total energy.
The Peltier effect is most strongly observed in the case of p- and n-type semiconductors. Depending on the direction of the electric current through the semiconductor contact different type- p-n- and n-p-transitions due to the interaction of charges represented by electrons (n) and holes (p), and their recombination energy is either absorbed or released. As a result of these interactions and generated energy processes, heat is either absorbed or released. The use of semiconductors of p- and n-type conductivity in thermoelectric refrigerators is illustrated in fig. 2.
Rice. 2. Use of p- and n-type semiconductors in thermoelectric refrigerators.
Combining a large number of pairs of p- and n-type semiconductors allows you to create cooling elements - Peltier modules of relatively high power. The structure of a semiconductor thermoelectric Peltier module is shown in fig. 3.
Rice. 3. Structure of the Peltier module
The Peltier module is a thermoelectric refrigerator consisting of p- and n-type semiconductors connected in series, forming p-n- and n-p-junctions. Each of these transitions has thermal contact with one of the two radiators. As a result of the passage of an electric current of a certain polarity, a temperature difference is formed between the radiators of the Peltier module: one radiator works like a refrigerator, the other radiator heats up and serves to remove heat. On fig. 4 shows the appearance of a typical Peltier module.
Rice. 4. Appearance Peltier module
A typical module provides a significant temperature difference, which is several tens of degrees. With appropriate forced cooling of the heating radiator, the second radiator, the refrigerator, makes it possible to achieve negative temperatures. To increase the temperature difference, cascade connection of Peltier thermoelectric modules is possible, provided that they are adequately cooled. This allows relatively simple means obtain a significant temperature difference and ensure effective cooling of the protected elements. On fig. 5 shows an example of a cascade connection of typical Peltier modules.
Rice. 5. An example of cascade connection of Peltier modules
Cooling devices based on Peltier modules are often referred to as active Peltier coolers or simply Peltier coolers.
The use of Peltier modules in active coolers makes them significantly more efficient than standard types of coolers based on traditional heatsinks and fans. However, in the process of designing and using coolers with Peltier modules, it is necessary to take into account a number of specific features arising from the design of the modules, their operating principle, the architecture of modern computer hardware, and the functionality of system and application software.
Of great importance is the power of the Peltier module, which, as a rule, depends on its size. A low power module does not provide the required level of cooling, which can lead to a malfunction of the protected electronic element, for example, a processor due to its overheating. However, using too large modules can cause the temperature of the cooling radiator to drop to the level of moisture condensation from the air, which is dangerous for electronic circuits. This is due to the fact that water continuously produced as a result of condensation can lead to short circuits in the electronic circuits of the computer. Here it is appropriate to recall that the distance between conductive conductors on modern printed circuit boards is often a fraction of a millimeter. Nevertheless, in spite of everything, it was the powerful Peltier modules as part of high-performance coolers and the corresponding additional cooling and ventilation systems that once allowed KryoTech and AMD in joint research to overclock AMD processors created using traditional technology to a frequency exceeding 1 GHz , that is, to increase their frequency of operation by almost 2 times compared to the normal mode of their operation. And it must be emphasized that this level of performance was achieved in conditions of ensuring the necessary stability and reliability of the processors in forced modes. Well, the result of such extreme overclocking was a performance record among processors of the 80x86 architecture and instruction set. And KryoTech has made good money by offering its cooling units to the market. Equipped with the appropriate electronics, they proved to be in demand as platforms for high-performance servers and workstations. And AMD received confirmation of the high level of its products and rich experimental material for further improvement of the architecture of its processors. By the way, similar studies were carried out with Intel processors Celeron, Pentium II, Pentium III, which also resulted in a significant increase in performance.
It should be noted that the Peltier modules emit a relatively large amount of heat during their operation. For this reason, you should use not only a powerful fan as part of the cooler, but also measures to reduce the temperature inside the computer case to prevent overheating of other computer components. To do this, it is advisable to use additional fans in the design of the computer case to ensure better heat exchange with the environment outside the case.
On fig. 6 shows the appearance of an active cooler, which includes a Peltier semiconductor module.
Rice. 6. Appearance of the cooler with the Peltier module
It should be noted that cooling systems based on Peltier modules are used not only in electronic systems such as computers. Such modules are used for cooling various high-precision devices. Peltier modules are of great importance for science. First of all, this concerns experimental research carried out in physics, chemistry, and biology.
Information about Peltier modules and refrigerators, as well as the features and results of their application, can be found on Internet sites, for example, at the following addresses:
Operation features
Peltier modules used as part of electronic cooling means are characterized by relatively high reliability and, unlike traditional refrigerators, do not have moving parts. And, as noted above, in order to increase the efficiency of their work, they allow cascade use, which makes it possible to bring the temperature of the cases of protected electronic elements to negative values even with their significant dissipation power.
However, in addition to the obvious advantages, Peltier modules also have a number of specific properties and characteristics that must be taken into account when using them as part of coolants. Some of them have already been noted, but for the correct application of the Peltier modules, they require more detailed consideration. The most important characteristics include the following features of operation:
- Peltier modules, which generate a large amount of heat during their operation, require the presence of appropriate heatsinks and fans in the cooler that can effectively remove excess heat from the cooling modules. It should be noted that thermoelectric modules are characterized by a relatively low coefficient of performance (COP) and, performing the functions of a heat pump, they themselves are powerful heat sources. The use of these modules as part of cooling means for computer electronic components causes a significant increase in temperature inside the system unit, which often requires additional measures and means to reduce the temperature inside the computer case. Otherwise, the increased temperature inside the case creates difficulties for work not only for the protected elements and their cooling systems, but also for the rest of the computer components. It should also be emphasized that the Peltier modules are a relatively powerful additional load for the power supply. Taking into account the value of the current consumption of the Peltier modules, the power of the computer power supply must be at least 250 W. All this leads to the expediency of choosing ATX motherboards and cases with power supplies of sufficient power. The use of this construct makes it easier for computer components to organize optimal thermal and electrical modes. It should be noted that there are Peltier refrigerators with their own power supply.
- The Peltier module, in case of its failure, isolates the cooled element from the cooler radiator. This leads to a very rapid violation of the thermal regime of the protected element and its early failure from subsequent overheating.
- The low temperatures that occur during the operation of Peltier refrigerators with excess power contribute to the condensation of moisture from the air. This poses a danger to electronic components, as condensation can cause short circuits between elements. To eliminate this danger, it is advisable to use Peltier refrigerators of optimal power. Whether condensation occurs or not depends on several parameters. The most important are: the ambient temperature (in this case, the temperature of the air inside the case), the temperature of the cooled object and the humidity of the air. The warmer the air inside the case and the greater the humidity, the more likely moisture condensation will occur and the subsequent failure of the electronic components of the computer. Below is a table illustrating the dependence of the moisture condensation temperature on a cooled object depending on the humidity and ambient temperature. Using this table, you can easily determine whether there is a danger of moisture condensation or not. For example, if the external temperature is 25°C and the humidity is 65%, then moisture condensation on the cooled object occurs when its surface temperature is below 18°C.
Dew point
| Humidity, % | |||||||||
| Temperature environment, °C |
30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 |
| 30 | 11 | 13 | 15 | 17 | 18 | 20 | 21 | 23 | 24 |
| 29 | 10 | 12 | 14 | 16 | 18 | 19 | 20 | 22 | 23 |
| 28 | 9 | 11 | 13 | 15 | 17 | 18 | 20 | 21 | 22 |
| 27 | 8 | 10 | 12 | 14 | 16 | 17 | 19 | 20 | 21 |
| 26 | 7 | 9 | 11 | 13 | 15 | 16 | 18 | 19 | 20 |
| 25 | 6 | 9 | 11 | 12 | 14 | 15 | 17 | 18 | 19 |
| 24 | 5 | 8 | 10 | 11 | 13 | 14 | 16 | 17 | 18 |
| 23 | 5 | 7 | 9 | 10 | 12 | 14 | 15 | 16 | 17 |
| 22 | 4 | 6 | 8 | 10 | 11 | 13 | 14 | 15 | 16 |
| 21 | 3 | 5 | 7 | 9 | 10 | 12 | 13 | 14 | 15 |
| 20 | 2 | 4 | 6 | 8 | 9 | 11 | 12 | 13 | 14 |
In addition to these features, it is necessary to take into account a number of specific circumstances associated with the use of Peltier thermoelectric modules as part of coolers used to cool high-performance central processors of powerful computers.
The architecture of modern processors and some system programs provide for a change in power consumption depending on the load of the processors. This allows you to optimize their energy consumption. By the way, this is also provided for by energy saving standards supported by some functions built into the hardware and software. modern computers. Under normal conditions, optimization of the processor and its power consumption has a beneficial effect both on the thermal regime of the processor itself and on the general thermal balance. However, it should be noted that modes with a periodic change in power consumption may not be well combined with the means of cooling processors using Peltier modules. This is due to the fact that existing Peltier refrigerators are usually designed for continuous operation. In this regard, the simplest Peltier refrigerators that do not have controls are not recommended to be used together with cooling programs such as, for example, CpuIdle, as well as with operating systems Windows NT/2000 or Linux.
If the processor switches to low power mode and, accordingly, heat dissipation, a significant decrease in the temperature of the case and processor chip is possible. Overcooling of the processor core can in some cases cause a temporary cessation of its performance, and as a result, a permanent freeze of the computer. It should be recalled that according to the Intel documentation, the minimum temperature at which the correct operation of mass-produced Pentium II and Pentium III processors is guaranteed is usually +5 °C, although, as practice shows, they work fine even at lower temperatures.
Some problems can also arise as a result of the operation of a number of built-in functions, for example, those that control cooler fans. In particular, the processor power management modes in some computer systems provide for changing the speed of the cooling fans through the motherboard's built-in hardware. Under normal conditions, this greatly improves the thermal behavior of the computer processor. However, in the case of using the simplest Peltier refrigerators, a decrease in the rotation speed can lead to a deterioration in the thermal regime with a fatal result for the processor already due to its overheating by the operating Peltier module, which, in addition to performing the functions of a heat pump, is a powerful source of additional heat.
It should be noted that, as in the case of computer central processing units, Peltier refrigerators can be a good alternative to traditional means of cooling video chipsets used in modern high-performance video adapters. The operation of such video chipsets is accompanied by significant heat dissipation and is usually not subject to sudden changes in their operating modes.
In order to eliminate problems with variable power modes that cause condensation of moisture from the air and possible hypothermia, and in some cases even overheating of protected elements, such as computer processors, you should refuse to use such modes and a number of built-in functions. However, as an alternative, you can use cooling systems that provide intelligent controls for Peltier refrigerators. Such tools can control not only the operation of fans, but also change the operating modes of the thermoelectric modules themselves used in active coolers.
There have been reports of experiments on embedding miniature Peltier modules directly into processor chips to cool their most critical structures. This solution contributes to better cooling by reducing thermal resistance and can significantly increase operating frequency and processor performance.
Work in the direction of improving systems for ensuring optimal temperature conditions for electronic elements is being carried out by many research laboratories. And cooling systems involving the use of Peltier thermoelectric modules are considered extremely promising.
Examples of Peltier refrigerators
Relatively recently, Peltier modules of domestic production appeared on the computer market. These are simple, reliable and relatively cheap ($7-$15) devices. Generally, a cooling fan is not included. Nevertheless, such modules allow not only to get acquainted with promising means of cooling, but also to use them for their intended purpose in computer component protection systems. Here is a summary of one of the samples.
Module size (Fig. 7) - 40×40 mm, maximum current - 6 A, maximum voltage - 15 V, power consumption - up to 85 W, temperature difference - more than 60 °C. When providing powerful fan the module is able to protect the processor with power dissipation up to 40 watts.
Rice. 7. Appearance of the refrigerator PAP2X3B
There are both less and more powerful variants of domestic Peltier modules on the market.
The range of foreign devices is much wider. Below are examples of refrigerators, in the design of which Peltier thermoelectric modules are used.
Peltier active refrigerators from Computernerd
| Name | Manufacturer / supplier | Fan parameters | CPU |
| PAX56B | Computernerd | ball-bearing | Pentium/MMX up to 200MHz, 25W |
| PA6EXB | Computernerd | dual ball-bearing, tachometer | Pentium MMX up to 40W |
| DT-P54A | DesTech Solutions | dual ball bearing | Pentium |
| AC-P2 | AOC Cooler | ball bearing | Pentium II |
| PAP2X3B | Computernerd | 3 ball bearing | Pentium II |
| STEP-UP-53X2 | Step Thermodynamics | 2 ball bearings | Pentium II, Celeron |
| PAP2CX3B-10 BCool PC-Peltier |
Computernerd | 3 ball-bearing, tachometer | Pentium II, Celeron |
| PAP2CX3B-25 BCool-ER PC-Peltier |
Computernerd | 3 ball-bearing, tachometer | Pentium II, Celeron |
| PAP2CX3B-10S BCool-EST PC-Peltier | Computernerd | 3 ball-bearing, tachometer | Pentium II, Celeron |
The PAX56B refrigerator is designed to cool Intel, Cyrix and AMD Pentium and Pentium-MMX processors operating at frequencies up to 200 MHz. The 30x30mm thermoelectric module allows the cooler to keep the CPU temperature below 63°C with 25W power dissipation and outside temperature equal to 25 °C. Due to the fact that most processors dissipate less power, this cooler allows you to keep the processor temperature much lower than many alternative coolers based on heatsinks and fans. The Peltier module included in the PAX56B refrigerator is powered by a 5 V supply capable of providing a current of 1.5 A (maximum). The fan of this refrigerator requires a voltage of 12 V and a current of 0.1 A (maximum). PAX56B refrigerator fan parameters: ball-bearing, 47.5 mm, 65,000 hours, 26 dB. The overall size of this refrigerator is 25×25×28.7 mm. The estimated price of the PAX56B refrigerator is $35. The indicated price is given in accordance with the price list of the company for the middle of 2000.
The PA6EXB refrigerator is designed to cool more powerful Pentium-MMX processors with power dissipation up to 40W. This refrigerator is suitable for all Intel, Cyrix and AMD processors connected via Socket 5 or Socket 7. The Peltier thermoelectric module included in the PA6EXB refrigerator has a size of 40 × 40 mm and consumes a maximum current of 8 A (typically 3 A) at a voltage of 5 B with connection through a standard computer power connector. The overall size of the PA6EXB refrigerator is 60×60×52.5mm. When installing this refrigerator, for good heat exchange between the radiator and the environment, it is necessary to provide an open space around the refrigerator of at least 10 mm at the top and 2.5 mm at the sides. The PA6EXB cooler achieves a CPU temperature of 62.7°C with a power dissipation of 40W and an ambient temperature of 45°C. Taking into account the principle of operation of the thermoelectric module included in this refrigerator, in order to avoid moisture condensation and short circuit, it is necessary to avoid using programs that put the processor into sleep mode on long time. The estimated price of such a refrigerator is $65. The indicated price is given in accordance with the price list of the company for the middle of 2000.
Refrigerator DT-P54A (also known as PA5B by Computernerd) is designed for Pentium processors. However, some companies that offer these refrigerators on the market recommend it to Cyrix/IBM 6x86 and AMD K6 users as well. The radiator included in the refrigerator is quite small. Its dimensions are 29×29 mm. The refrigerator has a built-in temperature sensor, which, if necessary, will notify you of overheating. It also controls the Peltier element. The kit includes an external control device. It performs the functions of monitoring the voltage and the operation of the Peltier element itself, the operation of the fan, as well as the temperature of the processor. The device will generate an alarm if the Peltier element or fan has failed, if the fan is running at less than 70% of its desired speed (4500 RPM), or if the processor temperature has risen above 145°F (63°C). If the processor temperature rises above 100°F (38°C), then the Peltier element is automatically enabled, otherwise it is in disabled mode. The latter function eliminates problems associated with moisture condensation. Unfortunately, the element itself is glued to the heat sink so strongly that it cannot be separated without destroying its structure. This makes it impossible to install it on another, more powerful radiator. As for the fan, its design is characterized by a high level of reliability and it has high parameters: supply voltage - 12 V, rotation speed - 4500 RPM, air supply speed - 6.0 CFM, power consumption - 1 W, noise characteristics - 30 dB. This refrigerator is quite productive and useful for overclocking. However, in some cases of overclocking the processor, you should simply use a large heatsink and a good cooler. The price of this refrigerator ranges from $39 to $49. The indicated price is given in accordance with the price list of several firms for the middle of 2000.
The AC-P2 refrigerator is designed for Pentium II type processors. The kit includes a 60mm cooler, a heatsink and a 40mm Peltier element. Poorly suited to Pentium II 400 MHz and higher processors, since SRAM memory chips are practically not cooled. The estimated price for mid-2000 is $59.
Refrigerator PAP2X3B (Fig. 8) is similar to AOC AC-P2. Two 60 mm coolers are added to it. SRAM cooling issues remain unresolved. It should be noted that the refrigerator is not recommended to be used together with cooling programs, such as, for example, CpuIdle, as well as under Windows NT or Linux operating systems, since moisture condensation on the processor is likely. The estimated price for mid-2000 is $79.
Rice. 8. Appearance of the refrigerator PAP2X3B
The STEP-UP-53X2 refrigerator is equipped with two fans that pump a large amount of air through the radiator. The estimated price for mid-2000 is $79 (Pentium II), $69 (Celeron).
Computernerd's Bcool series refrigerators (PAP2CX3B-10 BCool PC-Peltier, PAP2CX3B-25 BCool-ER PC-Peltier, PAP2CX3B-10S, BCool-EST PC-Peltier) are designed for Pentium II and Celeron processors and have similar specifications as shown in following table.
Refrigerators of the BCool series
| item | PAP2CX3B-10 BCool PC-Peltier |
PAP2CX3B-25 BCool-ER PC-Peltier |
PAP2CX3B-10S BCool-EST PC-Peltier |
|||||||
| Recommended Processors | Pentium II and Celeron | |||||||||
| Number of fans | 3 | |||||||||
| Central fan type | Ball-Bearing, tachometer (12 V, 120 mA) | |||||||||
| Central fan size | 60x60x10mm | |||||||||
| Type of external fan | Ball Bearing | Ball bearing, tachometer | Ball Bearing, Thermistor | |||||||
| External fan size | 60x60x10mm | 60x60x25mm | ||||||||
| Voltage, current | 12 V, 90 mA | 12 V, 130 mA | 12V, 80-225mA | |||||||
| Total Fan Coverage | 84.9 cm2 | |||||||||
| Total current for fans (power) | 300 mA (3.6W) |
380 mA (4.56W) |
280-570mA (3.36-6.84W) |
|||||||
| Number of pins on the heatsink (center) | 63 long and 72 short | |||||||||
| Number of pins on the heatsink (each end) | 45 long and 18 short | |||||||||
| Total number of pins on the heatsink | 153 long and 108 short | |||||||||
| Radiator dimensions (center) | 57x59x27 mm (including thermoelectric module) | |||||||||
| Radiator Dimensions (each end) | 41x59x32 mm | |||||||||
| Overall Radiator Dimensions | 145x59x38 mm (including thermoelectric module) | |||||||||
| General dimensions of the refrigerator | 145x60x50 mm | 145x60x65 mm | ||||||||
| Refrigerator weight | 357 grams | 416 grams | 422 grams | |||||||
| Warranty | 5 years | |||||||||
| Estimated price (2000) | $74.95 | $79.95 | $84.95 | |||||||
It should be noted that the BCool refrigerator group also includes devices that have similar characteristics, but lack Peltier elements. Such refrigerators are naturally cheaper, but also less effective as a means of cooling computer components.
In preparing the article, the materials of the book "PC: tuning, optimization and overclocking" were used. 2nd ed., revised. and additional, - St. Petersburg: BHV - Petersburg. 2000. - 336 p.
