Peltier semiconductor refrigerators

The operation of modern high-performance electronic components that form the basis of computers is accompanied by significant heat generation, especially when operating in forced overclocking modes. The efficient operation of such components requires adequate cooling means to provide the required temperature conditions for their operation. As a rule, such means of maintaining optimal temperature conditions are coolers, which are based on traditional radiators and fans.

The reliability and performance of such tools are continuously improving due to the improvement of their design, the use of the latest technologies and the use of a variety of sensors and control devices in their composition. This makes it possible to integrate such tools into the composition of computer systems, providing diagnostics and control of their work in order to achieve the highest efficiency while ensuring optimal temperature conditions for the operation of computer elements, which increases reliability and lengthens the time of their trouble-free operation.

The parameters of traditional coolers are constantly improving, however, recently such specific means of cooling electronic elements as Peltier semiconductor refrigerators have 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 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 means 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 small household refrigerators, the work of which was based on the Peltier effect. However, the imperfection of existing technologies, low values ​​of the efficiency and high prices did not allow such devices to leave research laboratories and test benches at that time.

But the Peltier effect and thermoelectric modules did not remain the lot of scientists only. In the process of improving technologies, many negative phenomena were significantly weakened. These efforts have resulted in highly efficient and reliable semiconductor modules.

In recent years, these modules, whose work is based on the Peltier effect, have been actively used to cool various electronic components of computers. They, in particular, began to be used to cool modern powerful processors, the operation of which is accompanied by a high level of heat release.

Due to their unique thermal and operational properties, devices based on thermoelectric modules - Peltier modules, allow achieving the required level of cooling of computer elements without any special technical difficulties and financial costs. As coolers of electronic components, these means of maintaining the required temperature regimes for their operation are extremely promising. They are compact, convenient, reliable and very efficient.

Semiconductor refrigerators are of particular interest as a means of providing intensive cooling in computer systems, the elements of which are installed and operated in severe 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, of the entire computer system. However, the operation of computer components in such modes is characterized by significant heat release 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 release, are not only high-performance processors, but also elements of modern high-performance video adapters, and in some cases also microcircuits of memory modules. Such powerful elements require intensive cooling for their correct operation, even in standard modes, and even more so in overclocking modes.

Peltier modules

In Peltier refrigerators, a conventional so-called thermoelectric refrigerator is used, the action 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).

Lenz placed a drop of water in a depression at the junction of two rods made of bismuth and antimony. When an electric current was passed in one direction, a drop of water froze. When the current was passed in the opposite direction, the formed ice melted. Thus, it was found that when two conductors of electric current pass through the contact, depending on the direction of the latter, in addition to Joule heat, additional heat is released or absorbed, which is called Peltier heat. This phenomenon is called the Peltier phenomenon (Peltier effect). Thus, it is the opposite of the Seebeck phenomenon.

If in a closed circuit consisting of several metals or semiconductors, the temperatures at the places of contacts of 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 strength (Q = R · I · I · t), the Peltier heat is proportional to the first degree of the current strength and changes sign when the direction of the latter changes. Peltier heat, as shown by experimental studies, can be expressed by the formula:

Qп = П 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 on their temperature.

Peltier heat Qp is considered positive if it is released, and negative if it is absorbed.

Rice. 1. Scheme of the experiment for measuring Peltier heat, Cu - copper, Bi - bismuth.

In the presented scheme of the experiment for measuring Peltier heat, with the same resistance of wires R (Cu + Bi), lowered into the calorimeters, the same Joule heat will be released in each calorimeter, namely Q = R I I t. The Peltier heat, on the other hand, will be positive in one calorimeter and negative in the other. In accordance with this scheme, you can 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 significantly 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 characteristic of materials, is usually not measured, but calculated through the Thomson coefficient:

P = a T

where P is the Peltier coefficient, a is the Thomson coefficient, and 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 different materials, depending on its direction, in addition to Joule heat, additional heat is released or absorbed, which is called 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 decelerated under the action of an internal contact potential difference between the metals. In the first case, the kinetic energy of electrons increases and then is released in the form of heat. In the second case, the kinetic energy of the electrons decreases, and this decrease in energy is replenished due to the thermal vibrations of the atoms of the second conductor. As a result, cooling occurs. A more complete theory takes into account the change not in the potential energy during the transfer of an electron from one metal to another, but the change in the total energy.

The Peltier effect is most strongly observed in the case of using p- and n-type semiconductors. Depending on the direction of the electric current through the contact of semiconductors of different types - p-n- and n-p-junctions 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 p- and n-type semiconductors 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 makes it possible to create cooling elements - Peltier modules of relatively high power. The structure of the semiconductor thermoelectric Peltier module is shown in Fig. 3.

Rice. 3. The 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 junctions 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 as a refrigerator, the other radiator heats up and serves to remove heat. In fig. 4 shows the appearance of a typical Peltier module.

Rice. 4. Appearance of the 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 - refrigerator, allows reaching negative temperatures. To increase the temperature difference, it is possible to cascade Peltier thermoelectric modules while ensuring their adequate cooling. This makes it possible, by relatively simple means, to obtain a significant temperature difference and to ensure effective cooling of the protected elements. In fig. 5 shows an example of cascading typical Peltier modules.

Rice. 5. Example of cascading Peltier modules

Cooling devices based on Peltier modules are often called active Peltier coolers or simply Peltier coolers.

The use of Peltier modules in active coolers makes them much more efficient compared to standard types of coolers based on traditional radiators 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 principle of operation, the architecture of modern computer hardware and the functionality of the system and application software.

The power of the Peltier module is of great importance, which, as a rule, depends on its size. A low-power module does not provide the required level of cooling, which can lead to malfunction of the protected electronic element, for example, a processor, due to its overheating. However, the use of modules of too large capacity can cause the temperature of the cooling radiator to drop to the level of moisture condensation from the air, which is dangerous for the electronic circuits. This is due to the fact that water, continuously obtained as a result of condensation, can lead to short circuits in the electronic circuits of the computer. It is appropriate to recall here that the distance between conductive conductors on modern printed circuit boards is often fractions of a millimeter. Nevertheless, in spite of everything, it was the powerful Peltier modules in high-performance coolers and the corresponding additional cooling and ventilation systems that allowed KryoTech and AMD in their 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 in comparison with the standard mode of their operation. And it should be emphasized that this level of performance was achieved in the 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 architecture and the 80x86 instruction set. And the company KryoTech has made good money, offering its cooling units on the market. Equipped with the appropriate electronic stuffing, they have proven to be in demand as platforms for high-performance servers and workstations. And AMD has received confirmation of the high level of its products and a wealth of experimental material to further improve the architecture of its processors. By the way, similar studies were carried out with Intel Celeron, Pentium II, Pentium III processors, as a result of which a significant increase in performance was also obtained.

It should be noted that Peltier modules generate a relatively large amount of heat in the course of 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 the rest of the computer components. For this, it is advisable to use additional fans in the construction of the computer case to provide better heat exchange with the environment outside the case.

In fig. 6 shows the appearance of an active cooler, which includes a semiconductor Peltier module.

Rice. 6. Appearance of a cooler with a 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 to cool 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 use, can be found on sites on the Internet, for example, at the following addresses:

Features of operation

Peltier modules used as a part of means for cooling electronic elements are distinguished by a relatively high reliability, and unlike refrigerators created using traditional technology, they do not have moving parts. And, as noted above, to increase the efficiency of their work, they allow for cascade use, which makes it possible to bring the temperature of the enclosures of the 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 in the composition 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 operating features:

• Peltier modules, which generate a large amount of heat during their operation, require the presence of appropriate heatsinks and fans in the cooler, capable of effectively removing excess heat from the cooling modules. It should be noted that thermoelectric modules are characterized by a relatively low efficiency (efficiency) and, performing the functions of a heat pump, they themselves are powerful sources of heat. The use of these modules as part of cooling means for electronic components of a computer 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 operation 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 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 value of the computer power supply must be at least 250 W. All this leads to the advisability of choosing motherboards and ATX cases with sufficient power supplies. The use of this construct makes it easier for the computer components to organize optimal thermal and electrical conditions. It should be noted that there are Peltier refrigerators with their own power supply.
• The Peltier module, in case of 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 quick failure from subsequent overheating.
• Low temperatures that occur during the operation of Peltier refrigerators with excess capacity contribute to the condensation of moisture from the air. This poses a danger to electronic components, as condensation can cause short circuits between the components. To eliminate this danger, it is advisable to use Peltier refrigerators of optimal power. Whether or not condensation occurs depends on several parameters. The most important are: ambient temperature (in this case, the air temperature inside the case), the temperature of the cooled object and air humidity. The warmer the air inside the case and the higher 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 the cooled object depending on the humidity and ambient temperature. Using this table, you can easily determine whether there is a risk of moisture condensation or not. For example, if the outside 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.

Moisture condensation temperature

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 them to optimize their energy consumption. By the way, this is also stipulated by the energy saving standards supported by some functions built into the hardware and software of modern computers. Under normal conditions, optimization of the processor's operation and its power consumption has a beneficial effect both on the thermal mode of the processor itself and on the overall thermal balance. However, it should be noted that modes with periodic changes in power consumption can be poorly 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 Windows NT / 2000 or Linux operating systems.

If the processor goes into a low power consumption mode and, accordingly, heat dissipation, a significant decrease in the temperature of the case and the crystal of the processor is possible. Overcooling of the processor core can in some cases cause a temporary cessation of its performance, and, as a result, permanent freeze of the computer. It should be remembered that according to the Intel documentation, the minimum temperature at which the correct operation of serial Pentium II and Pentium III processors is usually guaranteed is +5 ° C, although, as practice shows, they work perfectly well at lower temperatures.

Some problems can also arise as a result of the work of a number of built-in functions, for example, those that control the fans of coolers. Specifically, the processor power management modes in some computer systems involve changing the rotational speed of the cooling fans through the built-in motherboard hardware. Under normal conditions, this significantly improves the thermal performance 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 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 processors, 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 release and is usually not subject to sharp changes in their operating modes.

In order to eliminate problems with variable power consumption modes that cause moisture condensation from the air and possible hypothermia, and in some cases even overheating of protected elements, such as computer processors, you should abandon the use of such modes and a number of built-in functions. Alternatively, however, refrigeration systems with intelligent Peltier refrigerator controls can be used. Such means can control not only the operation of the fans, but also change the operating modes of the thermoelectric modules themselves, which are used as part of active coolers.

There have been reports of experiments on embedding miniature Peltier modules directly into processor microcircuits to cool their most critical structures. This solution contributes to better cooling by reducing thermal resistance and can significantly increase the operating frequency and performance of the processors.

Many research laboratories are working to improve systems for ensuring optimal temperature conditions for electronic elements. And cooling systems involving the use of Peltier thermoelectric modules are considered extremely promising.

Examples of Peltier refrigerators

More recently, domestically produced Peltier modules have appeared on the computer market. They are simple, reliable and relatively cheap ($ 7- $ 15) devices. Typically, a cooling fan is not included. Nevertheless, such modules make it possible not only to get acquainted with promising cooling means, but also to use them for their intended purpose in the protection systems of computer components. Here are the brief parameters 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. By providing a powerful fan, the module is able to protect the processor with up to 40W of power dissipation.

Rice. 7. External view of the PAP2X3B refrigerator

There are both less and more powerful versions 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.

Active Peltier refrigerators from Computernerd

Name	Manufacturer / supplier	Fan parameters	CPU
PAX56B	Computernerd	ball-bearing	Pentium / MMX up to 200 MHz, 25 W
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 bearing	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 refrigerator to keep the processor temperature below 63 ° C with a power dissipation of 25 W and an external temperature of 25 ° C. Due to the fact that most processors dissipate less power, this refrigerator allows you to keep the processor temperature much lower than many alternative coolers based on heatsinks and fans. The PAX56B Peltier module is powered by a 5 V supply capable of supplying 1.5 A maximum. The fan of this refrigerator requires a voltage of 12 V and a current of 0.1 A (maximum). The parameters of the fan of the PAX56B refrigerator: ball-bearing, 47.5 mm, 65000 hours, 26 dB. The overall size of this refrigerator is 25 x 25 x 28.7mm. The approximate 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 the more powerful Pentium-MMX processors that dissipate power 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 (usually 3 A) at a voltage of 5 B with connection through a standard computer power connector. The total size of PA6EXB refrigerator is 60 × 60 × 52.5mm. When installing this refrigerator, for good heat exchange of the radiator with 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 refrigerator provides a CPU temperature of 62.7 ° C with a power dissipation of 40 W and an external temperature of 45 ° C. Taking into account the principle of operation of the thermoelectric module, which is part of 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 for a long time. The approximate 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.

The DT-P54A (also known as Computernerd PA5B) is designed for Pentium processors. However, some companies offering these refrigerators on the market recommend it to Cyrix / IBM 6x86 and AMD K6 users. The radiator included in the refrigerator is small enough. Its dimensions are 29 × 29 mm. The refrigerator has a built-in thermal sensor, which, if necessary, will notify about overheating. He 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 unit will generate an alarm if the Peltier element or fan is out of order, if the fan is spinning less than 70% of the required speed (4500 RPM), or if the processor temperature rises above 145 ° F (63 ° C). If the processor temperature rises above 100 ° F (38 ° C), then the Peltier element is automatically turned on, otherwise it is in shutdown mode. The latter feature eliminates moisture condensation problems. Unfortunately, the element itself is glued to the radiator 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 powerful enough and useful for overclocking. However, in some cases of overclocking the processor, you should just 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 companies for the middle of 2000.

The AC-P2 refrigerator is designed for Pentium II processors. The kit includes a 60 mm cooler, a radiator and a 40 mm Peltier element. Poorly suited to Pentium II 400 MHz and higher processors, since SRAM memory chips are practically not cooled. Estimated mid-2000 price - $ 59.

Refrigerator PAP2X3B (fig. 8) is similar to AOC AC-P2. It includes two 60mm coolers. SRAM cooling issues remained 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, as moisture condensation on the processor is likely. Estimated mid-2000 price - $ 79.

Rice. 8. Appearance of the refrigerator PAP2X3B

The STEP-UP-53X2 refrigerator is equipped with two fans that circulate a large amount of air through the radiator. Estimated mid-2000 price - $ 79 (Pentium II), $ 69 (Celeron).

Computernerd 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 characteristics, which are presented in following table.

Refrigerators 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 (12V, 120mA)
Central fan size		60x60x10 mm
External fan type		Ball-bearing	Ball-Bearing, tachometer							Ball-Bearing, thermistor
External fan size		60x60x10 mm	60x60x25 mm
Voltage, current		12V, 90mA	12V, 130mA							12V, 80-225mA
Total area covered by fans		84.9 cm 2
Total current for fans (power)		300 mA (3.6W)	380 mA (4.56 W)							280-570 mA (3.36-6.84W)
Number of pins on the heatsink (center)		63 long and 72 short
Number of pins on the heatsink (on each edge)		45 long and 18 short
The total number of pins on the heatsink		153 long and 108 short
Radiator dimensions (center)		57x59x27 mm (including thermoelectric module)
Radiator dimensions (at each end)		41x59x32 mm
Overall radiator dimensions		145x59x38 mm (including thermoelectric module)
Overall dimensions of the refrigerator		145x60x50 mm	145x60x65 mm
Refrigerator weight		357 gram	416 gram							422 gram
Guarantee		5 years
Estimated price (2000)		$74.95	$79.95							$84.95

It should be noted that the BCool group of refrigerators also includes devices that have similar characteristics, but which lack Peltier elements. Such refrigerators are naturally cheaper, but also less effective as a means of cooling computer components.

In preparing the article, materials from the book "PC: tuning, optimization and overclocking" were used. 2nd ed., Rev. and additional, - SPb .: BHV - Petersburg. 2000 .-- 336 p.

An excellent 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, at home, etc. It's a great little thing to chill drinks on a hot summer day.

It will take

Making a miniature refrigerator based on the Peltier element

The body was custom-sized to accommodate 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 case. Mark out a piece of hardboard with a pencil and a ruler.

We cut out all the elements with a hacksaw.

All parts of the body are ready.

Cut out a window for a radiator with a Peltier module from the middle part dividing the refrigerator into two parts.

We apply the cooling block 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 taking heat and exit through the holes on the other side.

We paint all the parts of the refrigerator body with aerosol paint from a can.

Let's start assembling.

We glue the dividing part of the cooling unit with hot glue.

We glue all parts of the case, on both sides.

The cooling unit rests on a piece of wood that is glued to the base.

For backlighting, you need two sections of 12 V LED strip. One color is white, the other is colored.

We screw on the small fan.

We divide the technical part of the refrigerator into two parts. The top will house the power supply. The dividing wall is placed on the square pieces of wooden lath glued to the sides.

Install the back wall.

We will make the door from a piece of acrylic glass. We mark it with a ruler and a pencil.

You can buy miniature loops or make yourself. We glue them on with a second glue.

Cover the sides of the acrylic glass with black self-adhesive tape.

We glue the handle to the door.

We will organize the lighting. We solder the contacts to the mini limit switch.

We solder the wires to the pieces of the LED strip. We glue the pieces themselves on a mini shelf made of the same acrylic.

We connect lighting, fans, Peltier element.

Install the switch on the side.

We isolate all open twists.

We close the compartment with the cooling unit. This must be done so that hot air does not rise up and heat the power supply.

We drill a hole for the 220 V power cable.

To prevent the refrigerator door from opening, we will install small neodymium magnets from the broken sidirom on the side.

We close the top cover, but before that we cut in the power switch, solder the wires. Now the refrigerator can be turned off with the button on top.

Close with a lid and fix with glue.

For proper thermal insulation, we glue the inside of the refrigerator with thin foam. We put 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 have cooled to 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 one, but it also has its advantages, one of which is a low-voltage power supply, which can be not only 12 V but also 5 V! Naturally, it is quite possible to power it from the USB port of a computer, although the return will be lower than when powered from a voltage of 12V.
The total power consumption when powered from a 220 V network is about 100 W. More detailed assembly instructions are in the video below.

Thermoelectric cooler Peltier.

The principle of operation was borrowed from the net: The operation of Peltier elements is based on the contact of two conductive materials with different levels of electron energy in the conduction band. When current flows through the contact of such materials, the electron must acquire energy in order to pass into the higher-energy conduction band of another semiconductor. When this energy is absorbed, the semiconductor contact point is cooled. When the current flows in the opposite direction, the semiconductor contact point heats up, in addition to the usual thermal effect.

When metals are in contact, the Peltier effect is so small that it is invisible against the background of ohmic heating and thermal conductivity phenomena. Therefore, in practical applications, the contact of two semiconductors is used.

The appearance of the Peltier element. When current is passed, heat is transferred from one side to the other. The Peltier element consists of one or more pairs of small semiconductor parallelepipeds - one n-type and one p-type in a pair (usually bismuth telluride, Bi2Te3 and silicon germanide), which are connected in pairs using metal jumpers. Metal bridges simultaneously serve as thermal contacts and are insulated with a non-conductive film or ceramic plate. Pairs of parallelepipeds are connected in such a way that a series connection of many pairs of semiconductors with different types of conductivity is formed, so that at the top there are one sequence of connections (n-> p), and opposite ones below (p-> n). Electric current flows sequentially through all parallelepipeds. Depending on the direction of the current, the upper contacts are cooled, and the lower ones are heated - or vice versa. Thus, the electric current transfers heat from one side of the Peltier element to the opposite side and creates a temperature difference.

If you cool the heating side of the Peltier element, for example with a radiator and a fan, then the temperature of the cold side becomes even lower. In single-stage cells, depending on the type of cell and the magnitude of the current, the temperature difference can reach approximately 70 K /

Description
A peltier element is a thermoelectric converter, which, when voltage is applied, is able to create a temperature difference on the plates, that is, to pump heat or cold. The presented Peltier element is used for cooling computer boards (subject to efficient heat dissipation), for cooling or heating water. Peltier elements are also used in portable and automotive refrigerators.

Peltier element powered by 12 volts.

For heating, you just need to reverse the polarity.
Peltier plate dimensions: 40 x 40 x 4 millimeters.
Operating temperature range: from -30 to +70? ..
Working voltage: 9-15 Volts.
Power consumption: 0.5-6 A.
Maximum power consumption: 60W.
A funny thing, we connect 12v + - it cools, we change the polarity, it heats. Used in many auto refrigerators, at least I have one. You can attach a compact circuit to the glove compartment so that the chocolate does not melt in the summer! For use and effective use, you need to use a cooling radiator - as a test I used a radiator from a computer processor, it is possible with a cooler. The better the cooling, the stronger and more effective the Peltier effect. When connected to a 12v battery, the current consumption was 5 amperes. In a word, the element is gluttonous. Since I have not yet assembled the entire circuit, but conducted only trial tests, without instrument temperature measurements. So, in the cooling mode, light frost appeared for 10 minutes. In the heating mode, the water in the metal cup boiled. The efficiency of this cooler is, of course, low, but the price of the device and the opportunity to experiment make the purchase justified. The rest in the photo

It is best to make a car refrigerator with your own hands on Peltier elements. The device of such a refrigerator is much simpler than the usual unit for us 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 quiet operation.

Compressor air conditioning 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 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 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 the thermal vibration of the atoms of the crystal lattice. And when current passes through series-connected junctions, the thermal energy absorbed by one pn junction is released on the other.

If you arrange the Peltier element so that one p-n junction is inside the container with good thermal insulation, and the other 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 also make a refrigerator into a car from such an old unit. But in this case, the design will depend on what you got, so you will certainly need to change the heaters and thermostats to 12 volts.

Making the case

To make the case, you will need materials:

One Peltier element cannot significantly cool a large volume, therefore, 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, but if they are not in your arsenal, an ordinary 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-refrigerator. 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 inner surface of the resulting box with insulation. Use "liquid nails" for this.

Stick the foam rubber seal on the upper ends of the walls. MDF is very hygroscopic, so it must be primed before pasting the case. Instead of a primer, dilute a little PVA with water (add 2 parts of liquid to 1 part of glue). Prime the case, let it dry and cover it with oilcloth. Do not paste over the door, as it is a radiator, and the 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 the refrigerator door in combination. With the outer dimensions of the case 40 × 40 × 30 cm, the upper radiator should be 40 × 40 cm, since it will cover the box, and the lower one is 38 × 38 cm, because it must go inside. Cut a 38 × 38 cm square from the insulation sheet, cut a hole in its center to the size of the cooling element and glue it to the smaller radiator with liquid nails. Solder the power wires to the element terminals (“+” should be applied to the red pin, and “ground” to the black one).

Put the large radiator down, and on it, with the thermal insulation up, place the small one so that their centers coincide. Drill a Ø 3 mm hole in two heatsinks one centimeter from each corner of the cutout in the thermal insulation. Lubricate the cooling element on both sides with heat-conducting paste and place the cooling side against the metal on the area free from the insulation of the smaller radiator. Cover it with a large radiator so that the previously made holes match, and tighten the resulting sandwich with screws and nuts until the thermal insulation is compressed and the radiators touch the cooler. Control the compression with a vernier caliper while measuring the distance between the heatsinks. The element thickness is 3.8 mm. After reducing the gap to this value, the contraction of the radiator fins should be stopped.

Attach the resulting door to the hinges, and them to the body in such a way that when you close it, the smaller radiator goes inside the body. To lead the wires out of the case, put on them a piece of rubber tube of a suitable diameter. Drill a hole slightly smaller than the outer diameter of the tube in the top plate near the contacts for the cooler power supply. Pull the wires through it, leaving a 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. It remains to attach a latch and some kind of handle for carrying the device and the cold generator is ready.

Choice of 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 that, it remains only to select from the directory the wire cross-section corresponding to this current. A fragment of the handbook sufficient for making a decision in this case, we give 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 square;
• I nom - 7.5 A, section - 2.3 mm 2;
• I nom - 10 A, section - 3.2 squares.

If your air conditioner draws more current than the cigarette lighter fuse, 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 = 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 vernier caliper, you can determine the diameter of the solid wire using a regular ruler. To do this, wind 10 turns of wire, turn to turn, on a screwdriver 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 with a constant 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 a 24 V on-board network, we recommend connecting 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:

1. High specific cooling power. With dimensions of 40 × 40 × 3.8 mm, one element can dissipate heat energy up to 57 W.
2. Quiet operation.
3. Low cost. One item costs no more than $ 3.
4. High reliability. The time of continuous operation before failure reaches 200 thousand hours.

Disadvantages of Peltier coolers:

• Low efficiency. Therefore, with a large refrigerated volume, it is difficult to achieve a significant temperature difference between opposite surfaces.
• The air conditioner consumes relatively high power. The current consumed by one element reaches 6 A.
• Part of the power consumption is spent on heating the radiator, which gives off heat to the atmosphere.

A self-made refrigerator, of course, will not notice the air conditioner or climate control, but in any case it will make it easier to travel in hot weather.

While I was building a country house, the desire to come up with how else to use extruded polystyrene foam did not leave me. Today it 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 frozen food can be safely transported. To make such a box, it took 160 rubles and half an hour of free time. 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, 50 mm thick, 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 such a container.

3. Here is a diagram of cutting a sheet. The sheet has sides with a thickness of 20 mm, they must be cut off from all sides, except for the bottom. The sheets are glued together with polyurethane foam. The technology is simple. Apply a little foam to the bonding 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 unattended. Only a small piece of expanded polystyrene, marked in gray on the diagram, will remain superfluous.

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 a tight fix. After that, the outside box can be painted. The paint corrodes the expanded polystyrene 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. The design can be supplemented 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 principle of which is based on the occurrence of a temperature difference during the flow of an electric current. It is these 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 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 radiator from a computer store, which costs 250 rubles. To improve air circulation inside the refrigerator and prevent freezing of the radiator, I decided to install fans on both sides. Also, a thermostat with an external temperature sensor and a relay, costing 170 rubles, will be useful to us, 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. Peltier element using thermal paste (included 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 in series. So that one Peltier element cools the other. In this case, it is possible to get a negative temperature in the container down to -18 degrees Celsius. We lay a piece of foamed thermal insulation around the perimeter between the element.

7. We connect the heatsinks to each other with standard mounting plates to the motherboard, connecting them with plastic clamps. This also allows the cold and hot sides to be thermally insulated from each other. Test 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 supply air to the radiators, which is less efficient than turning them over for blowing out. In an improvised box, it was possible to achieve a temperature of -3 degrees, at an ambient temperature of +26. The photo shows the model of the coolers, their advantage is in 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 start integrating 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 gasket around the perimeter 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 to blow out. Potential improvements - it might be worth lowering 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 a simple way. First, we press the plate using self-tapping screws, then fix it with a sealant.

12. The container is assembled. The weight of the container without the lid is 800 grams, the same is the weight of the lid with the assembled thermoelectric converter. 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 is much warmer in the trunk, even when the air conditioner is running) and current consumption - 3 Ampere. I think this is a great result.

I plan to make the next container from 3 Peltier elements installed in series in order to get a full-fledged freezer.