Peltier module: specifications

The thermocouple (Peltier module) operates on the principle opposite to the effect of a thermocouple, the appearance of a temperature difference when an electric current flows.

How does the Peltier element work?

It is quite simple to use the Peltier module, the principle of which is to extract or absorb heat at the moment of contact of different materials when a current passes through it . The density of the energy flow of electrons before and after contact is different. If the output is less, then there is heat. When electrons in contact are decelerated by an electric field, they transfer kinetic energy to the crystal lattice, heating it up. If they are accelerated, the heat is absorbed. This is due to the fact that part of the energy is taken from the crystal lattice and its cooling takes place.

To a large extent, this phenomenon is inherent in semiconductors, which is explained by the large difference in charge.

The Peltier module, the application of which is the subject of our review, is used in the development of thermoelectric cooling devices (TEM). The simplest of them consists of two semiconductors of p and n types, connected in series through copper contacts.

If electrons move from semiconductor "p" to "n", on the first transition with a metal bridge they recombine with the release of energy. The next transition from semiconductor "p" to a copper conductor is accompanied by "pulling" electrons through a contact by an electric field. This process results in energy absorption and cooling of the area around the contact. Similarly, processes occur on the following transitions.

With the arrangement of heated and cooled contacts in different parallel planes, a practical realization of the method will be obtained. Semiconductors are made of selenium, bismuth, antimony or tellurium. The Peltier module accommodates a large number of thermocouples placed between ceramic nitride or alumina plates.

Factors affecting the efficiency of TEM

• Current strength.
• Number of thermocouples (up to several hundred).
• Types of semiconductors.
• Cooling speed.

Great values have not yet been achieved due to low efficiency (5-8%) and high cost. In order for TEM to work successfully, it is necessary to ensure efficient heat removal from the heated side. This creates difficulties in the practical embodiment of the method. If you change the polarity, the cold and hot sides change with each other.

Advantages and disadvantages of modules

The need for TEM appeared with the advent of electronic devices that require miniature cooling systems. The advantages of the modules are:

• Compactness;
• Absence of mobile connections;
• The Peltier module has a reversible principle when the polarity is reversed;
• Simplicity of cascading connections for increasing power.

The main disadvantage of the module is low efficiency. This is manifested in a large amount of power when the required cooling effect is achieved. In addition, it has a high cost.

TEM application

Peltier module is used primarily for cooling chips and small parts. The beginning was laid for cooling elements of military equipment:

• Microcircuits;
• Infrared detectors;
• Elements of lasers;
• Quartz generators.

The Peltier thermoelectric module gradually began to be used in household appliances: for the creation of refrigerators, air conditioners, generators, thermostats. Its main purpose is to cool small objects.

CPU cooling

The main components of computers are constantly being improved, which leads to an increase in heat dissipation. Together with them, cooling systems are developed with the use of innovative technologies, with modern means of control. Peltier module application in this area found primarily in the cooling of microcircuits and other radio components. With the forced modes of overclocking of microprocessors traditional coolers can not cope anymore. And increasing the frequency of the processors makes it possible to increase their speed.

Increasing the fan speed results in significant noise. It is eliminated by using the Peltier module in a combined cooling system. In this way, leading companies quickly mastered the production of efficient cooling systems, which became very popular.

With processors, heat is usually given off by coolers. The air flow can be sucked from outside or from inside the system unit. The main problem is that the air temperature is sometimes insufficient for the heat sink. Therefore, TEMs were used to cool the air flow entering the system unit, thereby increasing the efficiency of heat exchange. Thus, the built-in air conditioner is an assistant to the traditional computer cooling system.

On both sides of the module are mounted aluminum radiators. On the side of the cold plate, air is pumped to the processor for cooling. After he takes away heat, another blower blows it through the heat sink of the hot plate of the module.

Modern TEM is controlled by an electronic device with a temperature sensor, where the degree of cooling is proportional to the heating of the processor.

The activation of processor cooling also creates some problems.

1. Simple Peltier cooling modules are designed for continuous operation. With reduced power consumption, heat dissipation also decreases, which can cause crystal overcooling and subsequent CPU hanging.
2. If the work of the cooler and the refrigerator is not properly coordinated, the latter can go into heating mode instead of cooling. The source of additional heat will cause the processor to overheat.

Thus, modern processors need advanced cooling technologies with control of the modules themselves. Similar changes in operating modes do not occur with video cards, which also require intensive cooling. Therefore, TEM is ideal for them.

Auto-refrigerator with own hands

In the middle of the last century, domestic industry tried to master the production of small refrigerators based on the Peltier effect. The existing technologies of that time did not allow this. Now the deterrent is mainly a high price, but attempts are continuing, and success has already been achieved.

The wide production of thermoelectric devices allows you to create with your own hands a small refrigerator, convenient for use in cars. Its basis is the "sandwich", which is done as follows.

1. A layer of heat conductive paste of the KPT-8 type is applied to the upper radiator and a Peltier module is adhered on one side of the ceramic surface.
2. Similarly, another radiator is attached to it from the lower side, intended for placement in the refrigerator compartment.
3. The whole device is tightly compressed and dried for 4-5 hours.
4. On both radiators coolers are installed: the upper one will remove heat, and the lower one - equalize the temperature in the refrigerator compartment.

The refrigerator body is made with a heat-insulating liner inside. It is important that it is tightly closed. To do this, you can use a conventional plastic tool box.

The 12 V supply is supplied from the vehicle system. It can be made from a 220 V AC mains, with a power supply. The scheme for converting AC to DC is the simplest one. It contains a rectifier bridge and a pulsation-smoothing capacitor. It is important that they do not exceed 5% of the nominal value at the output, otherwise the efficiency of the device is reduced. The module has two terminals of colored wires. To red is always connected "plus", to black - "minus".

The power of the TEM should correspond to the volume of the box. The first 3 digits of the marking mean the number of pairs of semiconductor trace elements inside the module (49-127 and more). The current strength is expressed by the last two digits of the marking (from 3 to 15 A). If the power is not enough, you need to glue another module on the radiators.

Note! If the current exceeds the power of the element, it will heat up on both sides and quickly fail.

Peltier module: generator of electrical energy

TEM can be used to generate electricity. To do this, create a temperature difference between the plates, and the thermocouples located between them will produce an electric current.

For practical use, you need a TEM of at least 5 V. Then it can be used to charge a mobile phone. Due to the low efficiency of the Peltier module, a DC-to-DC converter is required. To build the generator you will need:

• 2 modules Peltier TES1-12705 with the size of plates 40x40 mm;
• Converter EK-1674;
• Aluminum plates with a thickness of 3 mm;
• A pan for water;
• Heat-resistant adhesive.

Between the plates are placed two modules on the glue, and then the entire structure is fixed on the bottom of the pan. If it is filled with water and put on fire, you will get the necessary temperature difference, generating an EMF of about 1.5 V. By connecting the modules to the boost converter, it is possible to increase the voltage to 5 V necessary for charging the phone's battery.

The greater the temperature difference between the water and the lower heated plate, the more efficient the generator is. Therefore, we must try to reduce the heating of water in various ways: to make it flowing, to replace often with fresh, etc. An effective means of increasing the temperature difference is cascading the modules when they are superimposed one upon another. Increasing the overall dimensions of the device allows you to place more plates between the plates and thereby increase the total power.

The generator capacity will be enough to charge small batteries, work of LED lamps or a radio receiver. Note! To create thermal generators you need modules that can work at 300-400 ⁰ C! The rest are suitable only for trial tests.

Unlike other means of alternative power generation, they can work while driving, if you create something like a catalytic heater.

Domestic Peltier modules

TEM of its production appeared in our market not so long ago. They are highly reliable and have good characteristics. The Peltier module, which is in high demand, measures 40x40 mm. It is designed for a maximum current of 6 A and a voltage of up to 15 V.

Domestic Peltier module can be bought for a small price. With a power consumption of 85 watts, it creates a temperature drop of 60 ^° C. Together with the cooler it is able to protect from overheating a processor with a dissipated power of 40 watts.

Characteristics of modules of leading companies

Foreign devices are represented on the market in a greater variety. To protect the processors of leading companies, the Peltier module is used as a refrigerator RAX56V, the price of which is $ 35 with the fan.

With a size of 30x30 mm, it maintains a processor temperature of no higher than 63 ^° C with a power output of 25 watts. To supply enough voltage 5 V, and the current does not exceed 1.5 A.

The Peltier PA6EXV module, which provides a normal temperature regime with a power dissipation of 40 W, is well suited for cooling the processor. The area of its module is 40x40 mm, and the current consumption is up to 8 A. In addition to its impressive dimensions - 60x60x52.5 mm (together with the fan) - the device requires free space around it. Its price is $ 65.

When a Peltier module is used, the technical characteristics of the Peltier module should be consistent with the needs of the cooled devices. It is unacceptable that they have too low a temperature. This can lead to condensation of moisture, which has a harmful effect on electronics.

Modules for the manufacture of generators, such as TES1-12706, TES1-12709, are characterized by a higher power - 72 W and 108 W respectively. They are distinguished by the marking, always applied to the hot side. The maximum allowable temperature of the hot side is 150-160 ^° C. The greater the temperature difference between the plates, the higher the output voltage. The device operates at a maximum temperature difference of 600 ^° C.

The Peltier module can be bought inexpensively - about $ 10 or less per piece, if it's good to look. Quite often, sellers significantly overstate prices, but you can find several times cheaper, if you buy at a sale.

Conclusion

The Peltier effect has found application at present in the creation of small refrigerators required by modern technology. Reversibility of the process makes it possible to manufacture microelectrode plants, which are in demand for charging electronic devices.

Unlike other means of alternative power generation, they can work while driving, if a catalytic heater is installed.