• Thermoelectric Peltier. Peltier element, operating principle

    Thermoelectric Peltier cooler.

    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 move to a higher energy conduction band of another semiconductor. When this energy is absorbed, the contact point between the semiconductors cools. When current flows in the opposite direction, the contact point between the semiconductors heats up, in addition to the usual thermal effect.

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

    Appearance of a Peltier element. When current is passed, heat is transferred from one side to the other. A 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 jumpers 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 serial connection many pairs of semiconductors with different types of conductivity, so that at the top there are one sequence of connections (n->p), and at the bottom opposite (p->n). Electric current flows sequentially through all parallelepipeds. Depending on the direction of the current top contacts cool, and the lower ones heat up - or vice versa. Thus electric current transfers heat from one side of the Peltier element to the opposite and creates a temperature difference.

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

    Description
    The Peltier element is a thermoelectric converter, which, when voltage is applied, is capable of creating a temperature difference across the plates, that is, pumping heat or cold. The presented Peltier element is used for cooling computer boards (subject to effective heat removal), for cooling or heating water. Peltier elements are also used in portable and car refrigerators.

    Peltier element operating on 12 Volts.

    To heat up, you just need to change the polarity.
    Dimensions of the Peltier plate: 40 x 40 x 4 millimeters.
    Operating temperature range: from -30 to +70?..
    Operating voltage: 9-15 Volts.
    Current consumption: 0.5-6 A.
    Maximum power consumption: 60 W.
    A funny little thing, we connect 12v + - it cools, we change the polarity, it warms. It is used in many car refrigerators, at least this is what I have. You can attach a compact circuit to the glove compartment so that the chocolate doesn’t melt in the summer! To use and effectively use it, you need to use a cooling radiator - as a test I used a radiator from a computer processor, possibly with a cooler. The better the cooling, the stronger and more effective the Peltier effect is. When connected to a 12v car battery, the current consumption was 5 amperes. In a word, the element is gluttonous. Since I have not yet assembled the entire circuit, but only carried out trial tests, without instrumented temperature measurements. So, in the cooling mode, light frost appeared within 10 minutes. In heating mode, the water in the metal cup began to boil. 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 is in the photo

    The topic of cooling PC components worries many users. Most of them are limited to standard air coolers; some enthusiasts assemble air coolers. What's next? Surely those who are seriously interested in overclocking have heard about Peltier modules (or thermoelectric modules, hereinafter referred to as TEM; English version - TEC, Thermoelectric Cooler) and their use as heat sinks for very hot computer elements.

    However, often even basic information By correct use These amazing devices are difficult to find, hence the numerous mistakes made by those who encounter them for the first time. By the way, manufacturers of cooling systems are also experimenting with Peltier modules, sometimes presenting very interesting concepts to the public. How TEMs work, whether they are really so necessary in a computer’s system, how to assemble simple coolers yourself and avoid the simplest mistakes that are quite typical for beginners - we will talk about all this in this material.

    A little theory

    What exactly are Peltier modules? In the basic definition, these are thermoelectric converters, the operating principle of which is based on the Peltier effect, discovered back in 1834. The essence this process consists in the occurrence of a temperature difference at the point of contact between materials when an electric current flows through them.

    We will not go into details of the history of the discovery and the scientific basis for the specifics of the TEM operation, since an entire dissertation could be devoted to this topic. However, we will mention general concepts.

    Basic diagram of a TEM device

    Peltier elements consist of two conductive materials (semiconductors) with different electron energy levels in the conduction band. The physics of current flow through such substances is such that in order for electrons to pass through, they require a certain recharge, which is received at the moment the current passes through the junction. In this case, it is possible for particles to move into the high-energy conduction zone from one material to another. The point of contact between the semiconductors cools down at the moment of energy absorption. Changing the direction of the current or moving electrons from a higher energy zone to a less saturated one leads to heating of the contact site. In addition, Peltier modules exhibit a thermal effect, characteristic of any substance through which an electric current is passed. In general, the processes inherent in TEM also manifest themselves at the point of contact between ordinary metals, but it is almost impossible to determine them without complex instruments. Therefore, semiconductors serve as the basis for modules.

    A Peltier element consists of one or more pairs of semiconductor parallelepipeds different types(as in diodes or transistors, n- and p-type). Modern industry most often chooses silicon germanide and bismuth telluride for these purposes. Semiconductors are connected in pairs by metal bridges made of fusible substances. The latter act as thermal contacts and are in direct contact with the ceramic plate or stand. Pairs of semiconductors are connected in series, different types conductivities are in contact with each other. On one side of the module there are only n->p junctions, on the other - p->n. The flow of current causes cooling and heating of the opposite groups of contacts. Therefore, we can talk about the transfer of thermal energy by a current from one side of the Peltier module to the other and, as a consequence, the appearance of a temperature difference on the plate. Correct use of modules allows you to extract some benefits for industrial systems, including computer systems. By the way, the elements can also be used as electric generators - based on the same operating principles, the physics of the processes occurring inside is explained by the Seebeck effect (relatively speaking, the same Peltier effect with the “opposite sign”).

    Pros and cons of using TEM

    Often, the advantages of Peltier modules include:

    • relatively small dimensions;
    • the ability to work both for cooling and heating the system;
    • no moving parts or mechanical components subject to wear.

    At the same time, TEMs have a number of disadvantages that significantly hinder their widespread practical use. Among them are the following:

    • low module efficiency;
    • the need for a current source for their operation;
    • large power consumption to achieve a noticeable temperature difference and, as a consequence, significant heat release;
    • limited dimensions and useful characteristics.

    However, despite the negative characteristics of Peltier modules, they have found their application in a number of products. TEMs are primarily beneficial where the energy efficiency of the cooler is not critical, the lower the better. The elements are used to cool charge-coupled devices in digital cameras, allowing for a noticeable reduction in thermal noise during long exposures. Peltier modules are often used for cooling and temperature control of diode lasers in order to stabilize the wavelength of their radiation. It is possible to use several TEMs arranged sequentially in the form of cascades (the cold side of one cools the hot side of the other), thanks to which it is possible to achieve very low temperatures for devices with low heat generation. Peltier elements are the basis of compact refrigerators, primarily automobile ones. They are used both in miniature souvenirs from the field of computer peripherals, and in productive COs as main or auxiliary components. It is the latter option that we will talk about in more detail.

    Peltier modules in PC: practice

    When moving to the practical implementation of CO based on TEM, it is necessary to make several reservations that will allow you to correctly select the parameters of the final structures. Often, the experiments of beginners end in failure: either the temperatures on the “cold” side of the modules during operation are higher than on the hot side, or the systems demonstrate frankly weak results even in comparison with stock coolers without Peltier elements. The reasons often lie in incorrect calculations (or construction of the CO at random). The fact is that any TEM has its own standard characteristics; two values ​​are usually distinguished (let’s consider them using the example of the TEC1-12709 module with a declared maximum power of 136 W), for example, they write that ΔTmax Qcmax=0(°C) 66 and Qcmax ΔTmax =0(W) 89.2. To paraphrase this expression: the module is capable of providing a maximum temperature difference between the sides equal to 89.2 ºС in the absence of a thermal load and 0 ºС in the presence of one on the “cold” side of 66 W. Thus, the payload of the module lies in the range from 0 to 66 W, ideally, the less, the better and the greater the temperature difference the TEM will provide. At the same time, any module has another characteristic - maximum power consumption, which also needs to be removed from it using a cooling system. For the TEC1-12709 under consideration, Umax (V) is equal to 15.2 V, I max is 9 A. Therefore, when specified parameters we have a power consumption of 136.8 W, which, you see, is quite a lot.

    The cooling system must successfully remove heat directly from the module (ensuring the lowest possible temperature of the “hot” side) and PC components. You can calculate the approximate efficiency of such a system yourself - with a useful component of 150-200 W (approximately what modern overclocked CPUs produce), to obtain at least some visible results you will have to spend at least 600-800 W of electrical power and remove at least a kilowatt of thermal power. That is why high-performance COs based on Peltier modules are not widely used. However, precedents are comparatively successful implementation hybrid coolers are known, and we will try to create our own - low-power and optimal. To avoid limitations in the form of insufficient heat removal, we will place productive water blocks connected to the CBO circuit on the “hot” side of the TEM. By the way, Peltier modules cannot be installed directly on the core/heat distribution cover of the chips - the thin ceramic lining is not capable of maintaining effective heat transfer to all semiconductor pairs that make up the TEM. For this purpose, an intermediate “buffer” is best suited - a copper plate 5-7 mm thick, completely covering the surface of the module. By the way, the optimal operating mode of Peltier elements is ensured at reduced voltage and current consumption. Approaching these parameters to the maximum significantly increases the thermal output of the plate, but the useful component is not so noticeable.

    We decided to cool it down as much as possible. graphics chip Radeon video cards HD 4350 and CPU Core 2 Duo E8500, trying to overclock these components. To remove heat from the GPU, the already mentioned TEC1-12709 (maximum power consumption - 136 W) and a homemade copper water block were used; TEC1-12726 (395 W) and one of the best industrial water blocks, Swiftech Apogee GT, were paired with the processor. The modules were connected directly to the computer power supply in a 12-volt circuit. Application of kilowatt be quiet! Dark Power PRO BQT P6PRO-1000W gave every reason not to worry about the lack of power to power the PC and cooling system elements. The air cooler circuit employed two “double” radiators for 120 mm fans and a Hydor Seltz L30 pump (with a capacity of 1200 l/h at idle).

    If components are cooled to temperatures below room temperature (in particular, below the “dew point”), condensation should be expected to appear on supercooled surfaces. It is clear that water in this form is the main enemy of the user, and its release must be prevented. This is done by thoroughly thermally insulating any surfaces (parts of the RSV, the near-socket space on both sides of the board, the TEM itself, the heat spreader of the processor and GPU) with materials that do not allow air to pass through. The best materials for these purposes are standard thermal insulation material for water supply pipes (based on foam rubber), special putties, certain types of foam rubber supplied with PC components, and, at worst, thermal paste and paper napkins. In the latter case, it is permissible to use the PC only for short-term benching sessions. Thermal insulation will increase the overall efficiency of the installation.

    The resulting temperatures obtained in various operating modes of the components, their comparison with the indicators provided solely by the water cooling system, are shown in the diagram. As you can see, Peltier modules made it possible to lower the temperature of the components significantly below room temperature (depending on the load). Under such conditions, it was not difficult to overclock the processor to a frequency of 4.3 GHz by increasing the supply voltage to 1.35 V, and force the GPU to operate at 800 MHz (standard value - 600 MHz). At the same time, we experienced noticeable heating of the CO of the test bench (in the case the situation would have worsened more significantly) and a sharp increase in the level of power consumption of the PC (in fact, the entire design consumes more than a separate computer based on the components of the test bench). Similar solution It will definitely come in handy in the winter, but in the summer it is unlikely to please most users.

    Are you ready to make such sacrifices in order to achieve relatively low temperatures on PC components? Decide for yourself, but remember the basic tips given in this part of the material - they will help you correctly apply Peltier modules in practice. The use of TEM-based cooling systems is reasonable and justified in the case of low-power components (chipsets motherboards, GPU of low- and mid-level video cards). Do not forget about the thermal insulation of the cooled elements - after all, condensation is the main enemy of the system during experiments with TEM.

    Conclusions

    Summarizing the above regarding the operating features of Peltier modules and their feasibility practical application, let us repeat: TEMs have the mentioned advantages and disadvantages, which do not allow us to give an unambiguous answer to the question: “Is it worth...?” Their use is justified for removing minor thermal loads (this includes compact refrigerators, thermostated lasers; CO for low-power PC components - chipsets and individual GPUs).

    Based on Peltier elements, you can create various homemade cooling and heating devices; there are examples of successful implementation of low-power generators. But before you engage in the manufacture of such structures, familiarize yourself with the theoretical component - preliminary preparation will eliminate errors and save time during the practical implementation of projects.

    When talking about the use of Peltier modules in PCs, one should be quite careful: after reading about obtaining low temperatures on cooled elements, beginners often forget about the significant consumed and released power of such COs, and do not take into account the parameters and “safety margin” of a particular design. TEMs will be of interest primarily to overclockers, for whom every winning degree and every megahertz are important. The elements under consideration are an intermediate link between classical water cooling systems and chillers or freons operating on the principle of phase transition. However, the use of TEM cannot be called simple, so before embarking on serious experiments, carefully weigh the pros and cons.

    Ready-made RMs based on TEM

    Peltier modules are used by manufacturers of PC cooling systems as the main and auxiliary components of coolers. Sometimes this makes for spectacular efficient devices, sometimes things don’t work out as smoothly as originally planned. We decided to recall the main SOs using TEM, who were assigned the role of revolutionaries of their time.

    One of the first coolers with a Peltier element, which caused quite a lot of noise in the field CPU cooling(2003). However, a low safety margin, significant energy consumption for those times, cumbersome design and noisy operation did not allow it to gain a foothold in the market. If this model had appeared a year or two earlier, perhaps everything would have turned out differently.

    A super cooler for video cards, built on the same principle as the Titan Amanda: one half of the radiator works directly to remove heat from the GPU, the other cools the hot side of the TEM. At one time it turned out to be one of the best when testing CO for graphics adapters. (We wrote about it in Home PC in 2007.)

    Most powerful modern solution for cooling the CPU using a Peltier element. It is a productive water block that removes heat from the TEM (about 400 W of consumed electrical power), which, in turn, creates optimal temperature regime processor. This system is capable of operating the Core i7 at a frequency of about 4 GHz at a temperature of about 0 ºС (idle mode) and 20-30 ºС at maximum load.

    Similar to the processor solution, it is a high-performance water block for graphics adapter, supplemented by a Peltier module. Depending on the TDP of the video chip, it can keep its temperature at room temperature or lower.

    The Peltier elements of this CO cool part of the heat pipes. The approach is quite interesting and correct; the use of modules allows you to knock down a couple of degrees on the processor. However, the economic feasibility of such a move is a big question, due to the fact that the V10, at a significant price, is not able to overtake the best air supercoolers. Most likely, design features and insufficient power TEM.

    A series of fairly modern processor supercoolers on heat pipes using a thermoelectric module (2007-2008). Part of the radiator removed heat directly from the TEM, while the other half cooled the heating component. This approach to design makes it possible to avoid a sudden overload of the CO due to exceeding the heat release limits of the Peltier module. Coolers from the Amanda line demonstrated excellent results with processors with a relatively low TDP.

    XtremeLabs.org MONSTER T.E.C. Project

    Owners of SVO and those who are planning to acquire liquid systems, you may be interested in so-called chillers based on Peltier elements. Depending on the type of connection of the TEM to the circuit, they will allow you to slightly lower the temperature of the coolant, and when creating powerful COs, they will even ensure a coolant temperature close to zero.

    The Wehr-Wolf enthusiast, known to our readers, has long been interested in the topic of effective cooling of PC components and their further extreme overclocking. It all started back in 2005 with theoretical sketches, reasoning and one of the main components of the system - a massive “sandwich” consisting of large water blocks. However, abandoned on long time the ideas were realized only together with the author of this material, in the middle of this year by launching the enthusiastic project XtremeLabs.org MONSTER T.E.C. Project.

    First start-up of TEM chiller in field conditions

    The operating principle of the system is quite simple: Peltier modules (8 TEMs with a maximum power consumption of 136 W each) cool a large copper water block on both sides, and they themselves, in turn, are cooled by similar water blocks. The “cold” and “hot” circuits of the air cooler are completely separated from each other. To power such a number of TEMs during the first launch, two computer power supplies with a total declared power of 1200 W were used; the cooler of the “hot” circuit was a liquid coolant with two radiators for two 120 mm fans each, pumped by a powerful pump. However, even such a cooling system turned out to be insufficient, and the radiators had to be purged with high-performance industrial fans. A Hydor L20 II pump and a Swiftech Apogee GT water block were connected to the “cold” circuit; the cooler was a large water block in contact with the “cold” side of the TEM. As a result of the first experiment, it was possible to achieve a water temperature in the circuit of about 5-7 ºС, while a Core i7 965 processor was used as a load for the system Extreme Edition, overclocked to 4 GHz.

    On the one hand, the results obtained are truly impressive - only chillers based on phase transition systems can provide such temperatures at such loads; on the other hand, is the game worth the candle? The monstrous power consumption of the system, the bulky CO of the “hot” circuit, and the high overall cost are justified only by the conceptual status of XtremeLabs.org MONSTER T.E.C. Project, on at the moment currently being finalized.

    Greetings, banggood reader, astrologers have announced Peltier Week, so this review will talk about one interesting application of this thing. You are welcome under CUT.

    Let's start with an educational program

    As Wikipedia says, “A Peltier element is a thermoelectric converter, the operating principle of which is based on the Peltier effect - the occurrence of a temperature difference when an electric current flows.” I’m sure that after this phrase it didn’t become any clearer).

    Ok let's try differently. Imagine a specific aquarium consisting of two types of zones. In the first zone of the aquarium, the fish swim quickly, in the second, slowly. Let’s also imagine blades spinning in water at the boundaries of the zones. The rules are as follows: 1) the fish swims to another zone only when its speed matches the speed set for the zone. 2) when crossing the boundaries of the zone, the fish can interact with the blades to increase or decrease its speed. Now let’s imagine several zones located sequentially. (zones with more high speed Let's call it Z+ with low Z-) The fish is in Z+, it wants to move to Z-, it interacts with the blade at the boundary and begins to swim slower, while the blades (at the boundary Z+/W-) begin to spin faster. Next, the fish wants to move to the next zone Z+, it needs to accelerate; it interacts with the blade at the boundary Z-/Z+ and accelerates; at the same time, the blade begins to spin more slowly. Then everything repeats itself. You may notice that some blades will slow down and others will speed up. The Peltier element works on a similar principle. Instead of fish there are electrons instead of the speed of fish, the energy of electrons in semiconductors. When current flows through the contact of 2 semiconductors, an electron must acquire energy in order to move to a higher energy zone of another semiconductor. When this energy is absorbed, the contact point between the semiconductors cools. When current flows in the opposite direction, the contact point of the semiconductors heats up,
    Moreover, the greater the current, the higher the effect of energy transfer; energy is transferred (and not magically lost) from the “cold” side to the “hot” side, therefore the Peltier element is capable of cooling objects to temperatures below room temperature (in other words, it is a semiconductor heat pump). If your task is simply to remove heat from the processor, transistor, etc. The use of a Peltier element is unprofitable because You will need a radiator capable of transferring heat from the cooled object + heat generated during operation of the Peltier element to the environment. I think the theory is over and we can move on.
    Let's see what 13.90 greens looks like according to the sponsor of the review.

    The module is a kind of 5-level sandwich; it consists of a pair of radiators and fans and the Peltier element itself.
    The larger fan is designed to dissipate heat. If you apply force, it can be removed without unscrewing the screws.
    The fan is the most ordinary (Power supply 12V size 90mm) covered with a grille, initially the fan is installed for air exhaust.

    On the opposite side there is a small fan (Power supply 12V size 40mm)
    The baby is screwed on conscience
    Let's look at the radiators
    Large radiator size 100mm*120mm height 20mm
    Small radiator 40mm*40mm height 20mm. The radiators are fastened with two screws; the small radiator has a thread. When removing the radiator, thermal paste was found, which is good, but you can see that there is underpressure.
    The contact with a large radiator is also not ideal.
    The main conclusion is that if you want to get the most out of this module, be sure to look under the radiators. And if you erase the thermal paste, you can see that the element is installed here TEC1-12705(size 40mm*40mm*4mm) although the more powerful TEC1-12706 is declared. Manual for TEC1-12705

    Let's remove the small radiator and try to start the module by measuring the temperatures of the “warm” and “cold” sides.
    The temperature of the “cold” side is -16.1, “hot” 37.5 delta 53.6. current consumption at 12V was 4.2A.
    The Peltier element entered the mode after 90s.

    Now comes the fun part.
    We find a metal and shiny plate and make a hole in it for the thermocouple.
    Place thermal paste and install thermocouple
    Next, we make a narrowly directed photodetector and a photodiode from black paper and conventional components

    We assemble the finished device, remembering the rule “the angle of incidence is equal to the angle of reflection”
    Who guessed what it was? This is a device (well more precisely the model to demonstrate the principle of operation) to determine the dew point temperature/relative humidity. It works as follows: an IR LED shines into a reflective plate, after reflection, the light from the IR LED hits the IR photodiode. A voltage signal is collected from the reverse-biased IR photodiode. When the plate is cooled to the dew point temperature, condensation begins to collect on it, the intensity of the reflected radiation drops, and the signal at the photodiode changes. By recording the temperature of the plate and the surrounding air, the relative humidity can be found. For work I used Brymen BM869 (with homemade cable and software) and Uni-t UT61E
    Below is the result
    Red graph is plate temperature, blue graph is signal from the photodiode. We will consider the moment when the voltage from the photodiode has changed by half of the total voltage change to be the moment of condensation. Based on the set conditions, the measured dew point temperature in the room was +9C. The ambient air temperature was 26.7 (it was not displayed on the graphs because it was unchanged). At the same time, I launched the HTU21 module and observed the readings in the terminal. (a screenshot of the terminal has been added to graphics).Next I used online calculator to convert humidity to dew point temperature
    The result of converting humidity from HTU21 to dew point temperature coincided with the directly measured dew point temperature. This means that if you determine the dew point using the method described above, and then do a recalculation, you can determine the humidity quite accurately (Well, of course, if you do everything like an adult). This method is called the chilled mirror method, and hygrometers built on this principle are called condensation hygrometers. I hope you enjoyed the review and learned something new. Thank you all for your attention.

    The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.

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    Refrigeration equipment has become so firmly established in our lives that it is even difficult to imagine how we could live without it. But classic refrigerant designs are not suitable for mobile use, for example, as a traveling cooler bag.

    For this purpose, installations are used in which the operating principle is based on the Peltier effect. Let's briefly talk about this phenomenon.

    What is it?

    This term refers to a thermoelectric phenomenon discovered in 1834 by the French naturalist Jean-Charles Peltier. The essence of the effect is the release or absorption of heat in the area where dissimilar conductors through which electric current passes are in contact.

    In accordance with the classical theory, there is the following explanation of the phenomenon: electric current transfers electrons between metals, which can accelerate or slow down their movement, depending on the contact potential difference in conductors made of different materials. Accordingly, with an increase in kinetic energy, it is converted into thermal energy.

    On the second conductor, a reverse process is observed, requiring replenishment of energy, in accordance with the fundamental law of physics. This occurs due to thermal vibration, which causes the metal from which the second conductor is made to cool.

    Modern technologies make it possible to produce semiconductor elements-modules with maximum thermoelectric effect. It makes sense to briefly talk about their design.

    Design and principle of operation

    Modern modules are a structure consisting of two insulating plates (usually ceramic), with serially connected thermocouples located between them. A simplified diagram of such an element can be found in the figure below.


    Designations:

    • A – contacts for connecting to a power source;
    • B – hot surface of the element;
    • C – cold side;
    • D – copper conductors;
    • E – semiconductor based on p-junction;
    • F – n-type semiconductor.

    The design is made in such a way that each side of the module is in contact either p-n or n-p transitions(depending on polarity). Contacts p-n heat up, n-p – cool down (see Fig. 3). Accordingly, a temperature difference (DT) occurs on the sides of the element. To an observer, this effect will look like a transfer of thermal energy between the sides of the module. It is noteworthy that changing the polarity of the supply leads to a change in hot and cold surfaces.


     Rice. 3. A – hot side of the thermoelement, B – cold side

    Specifications

    The characteristics of thermoelectric modules are described by the following parameters:

    • cooling capacity (Q max), this characteristic is determined based on the maximum permissible current and the temperature difference between the sides of the module, measured in Watts;
    • maximum temperature difference between the sides of the element (DT max), the parameter is given for ideal conditions, the unit of measurement is degrees;
    • permissible current required to ensure maximum temperature difference – I max;
    • the maximum voltage U max required for the current I max to achieve the peak difference DT max ;
    • internal resistance of the module – Resistance, indicated in Ohms;
    • efficiency coefficient - COP (abbreviation from English - coefficient of performance), essentially this is the efficiency of the device, showing the ratio of cooling to power consumption. For inexpensive elements this parameter is in the range of 0.3-0.35, for more expensive models approaches 0.5.

    Marking

    Let's look at how typical module markings are deciphered using the example of Figure 4.


     Figure 4. Peltier module marked TEC1-12706

    The marking is divided into three meaningful groups:

    1. Element designation. The first two letters are always unchanged (TE), indicating that this is a thermoelement. The next one indicates the size, there may be the letters “C” (standard) and “S” (small). The last number indicates how many layers (cascades) there are in the element.
    2. The number of thermocouples in the module shown in the photo is 127.
    3. The rated current is in Amperes, for us it is 6 A.

    The markings of other models of the TEC1 series are read in the same way, for example: 12703, 12705, 12710, etc.

    Application

    Despite the rather low efficiency, thermoelectric elements have found wide application in measuring, computing, and also household appliances. Modules are an important operating element of the following devices:

    • mobile refrigeration units;
    • small generators to generate electricity;
    • cooling systems in personal computers;
    • coolers for cooling and heating water;
    • dehumidifiers, etc.

    Let us give detailed examples of the use of thermoelectric modules.

    Refrigerator using Peltier elements

    Thermoelectric refrigeration units are significantly inferior in performance to their compressor and absorption counterparts. But they have significant advantages, which makes their use advisable under certain conditions. These advantages include:

    • simplicity of design;
    • vibration resistance;
    • absence of moving elements (except for the fan blowing the radiator);
    • low noise level;
    • small dimensions;
    • ability to work in any position;
    • long service life;
    • low energy consumption.

    These characteristics are ideal for mobile installations.

    Peltier element as an electricity generator

    Thermoelectric modules can work as electricity generators if one of their sides is subjected to forced heating. How more difference temperatures between the sides, the higher the current generated by the source. Unfortunately, the maximum temperature for the thermal generator is limited; it cannot be higher than the melting point of the solder used in the module. Violation of this condition will lead to failure of the element.

    For mass production of thermal generators, special modules with refractory solder are used; they can be heated to a temperature of 300°C. In ordinary elements, for example, TEC1 12715, the limit is 150 degrees.

    Since the efficiency of such devices is low, they are used only in cases where it is not possible to use a more efficient source electrical energy. However, 5-10 W thermal generators are in demand among tourists, geologists and residents of remote areas. Large and powerful stationary installations powered by high-temperature fuel are used to power gas distribution units, meteorological station equipment, etc.


    To cool the processor

    Relatively recently, these modules began to be used in CPU cooling systems personal computers. Considering the low efficiency of thermoelements, the benefits of such structures are rather doubtful. For example, to cool a 100-170W heat source (fits most modern models CPU), you will need to spend 400-680 W, which requires installation powerful block nutrition.

    Second pitfall– an unloaded processor will release less thermal energy, and the module can cool it below the dew point. As a result, condensation will begin to form, which is guaranteed to damage the electronics.

    Those who decide to create such a system on their own will need to carry out a series of calculations to select the module power for a specific processor model.

    Based on the above, using these modules as a CPU cooling system is not cost-effective; in addition, they can cause failure computer equipment out of order.

    The situation is completely different with hybrid devices, where thermal modules are used in conjunction with water or air cooling.


    Hybrid cooling systems have proven their effectiveness, but the high cost limits the circle of their admirers.

    Air conditioner based on Peltier elements

    Theoretically, such a device will be structurally much simpler than classic climate control systems, but it all comes down to low performance. It’s one thing to cool a small volume of a refrigerator, another thing to cool a room or the interior of a car. Air conditioners using thermoelectric modules will consume more electricity (3-4 times) than equipment running on refrigerant.

    As for using it as a car climate control system, the power of a standard generator will not be enough to operate such a device. Replacing it with more efficient equipment will lead to significant fuel consumption, which is not cost-effective.

    In thematic forums, discussions on this topic periodically arise and various home-made designs are considered, but a full-fledged working prototype has not yet been created (not counting the air conditioner for a hamster). It is quite possible that the situation will change when modules with more acceptable efficiency become widely available.

    For cooling water

    The thermoelectric element is often used as a coolant for water coolers. The design includes: a cooling module, a thermostat-controlled controller and a heater. This implementation is much simpler and cheaper than a compressor circuit; in addition, it is more reliable and easier to operate. But there are also certain disadvantages:

    • water does not cool below 10-12°C;
    • cooling takes longer than its compressor counterpart, therefore, such a cooler is not suitable for an office with a large number workers;
    • the device is sensitive to external temperature; in a warm room, the water will not cool to the minimum temperature;
    • Installation in dusty rooms is not recommended, as the fan may become clogged and the cooling module may fail.
    Tabletop water cooler using Peltier element

    Air dryer based on Peltier elements

    Unlike an air conditioner, the implementation of a dehumidifier on thermoelectric elements quite possible. The design is quite simple and inexpensive. The cooling module lowers the temperature of the radiator below the dew point, as a result, moisture contained in the air passing through the device settles on it. The settled water is discharged into a special storage tank.


    Despite the low efficiency, in in this case The efficiency of the device is quite satisfactory.

    How to connect?

    There will be no problems with connecting the module; you need to apply power to the output wires. constant voltage, its value is indicated in the datasheet of the element. The red wire must be connected to the positive, the black wire to the negative. Attention! Reversing the polarity reverses the positions of the cooled and heated surfaces.

    How to check the Peltier element for functionality?

    The simplest and reliable way– tactile. It is necessary to connect the module to the appropriate voltage source and touch its different sides. For a working element, one of them will be warmer, the other colder.

    If you don’t have a suitable source at hand, you will need a multimeter and a lighter. The verification process is quite simple:

    1. connect the probes to the module terminals;
    2. bring the lit lighter to one of the sides;
    3. We observe the readings of the device.

    In the working module, when one of the sides is heated, an electric current is generated, which will be displayed on the device display.

    How to make a Peltier element with your own hands?

    Do homemade module at home it is almost impossible, especially since there is no point in this, given their relatively low cost (about $4-$10). But you can assemble a device that will be useful on a hike, for example, a thermoelectric generator.


    To stabilize the voltage, it is necessary to assemble a simple converter on the L6920 IC chip.


    A voltage in the range of 0.8-5.5 V is supplied to the input of such a converter; at the output it will produce a stable 5 V, which is quite enough to recharge most mobile devices. If a conventional Peltier element is used, it is necessary to limit the operating temperature range of the heated side to 150 °C. To avoid the hassle of tracking, it is better to use a pot of boiling water as a heat source. In this case, the element is guaranteed not to heat above 100 °C.

    Many have heard about the “magic” Peltier elements - when current passes through them, one side cools and the other heats up. This also works in reverse side- if one side is heated and the other cooled, electricity is generated. The Peltier effect has been known since 1834, but to this day we continue to be pleased with innovative products based on it (we just need to remember that when generating electricity, like solar panels- there is a point maximum power, and if you work far from it, the generation efficiency is greatly reduced).

    IN lately The Chinese have pushed the needle and flooded the Internet with their relatively cheap modules, so experiments with them no longer take too much money. The Chinese promise a maximum temperature difference between the hot and cold sides of 60-67 degrees. Hmmm... What if we take 5 elements and connect them in series, then we should get 20C-67*5 = -315 degrees! But something tells me that everything is not so simple...

    Brief theory

    Classic “Chinese” Peltier elements are 127 elements connected in series and soldered to a ceramic “ printed circuit board"from Al2O3. Accordingly, if the operating voltage is 12V, then each element accounts for only 94mV. There are elements with a different number of consecutive elements, and accordingly a different voltage (for example, 5V).

    We must remember that a Peltier element is not a resistor, its resistance is non-linear, so if we apply 12V - we may not get 6 amperes (for a 6 ampere element) - the current may change depending on the temperature (but not too much ). Also, at 5V (i.e. less than the nominal value), the current will not be 2.5A, but less.

    In addition, the amount of heat transferred is highly dependent on the temperature difference between the surfaces. With a difference of 60-67C, heat transfer tends to 0, and with a zero difference - 51 Watt for a 12*6 = 72-Watt element. Obviously, this no longer makes it possible to so easily connect elements in a series - each next one must be smaller in size than the previous one, otherwise the coldest element will try to give off more heat (72 W) than the element of the next stage can pass through itself at the desired temperature difference (1 -51W).

    Peltier elements are assembled with low-melting solder with a melting point of 138C - so if the element is accidentally left without cooling and overheats, then it will be enough to unsolder one of the 127 * 2 contacts to throw the element into a landfill. Well, the elements are very fragile - both ceramics and the cooling elements themselves - I accidentally tore 2 elements “lengthwise” due to thermal paste that had dried tightly:

    Let's try



    So, a small element is 5V * 2A, a large one is 12 * 9A. Cooler with heat pipes, room temperature. Result: -19 degrees. Strange... 20-67-67 = -114, but it turned out to be a pitiful -19...

    The idea is to take everything out into the frosty air, but there is a problem - a cooler with heat pipes cools well only if the temperature of the “hot” and “cold” sides of the cooler is at different sides gas-liquid phase transition of the tube filler. In our case, this means that the cooler, in principle, is not capable of cooling anything below +20C (since only thin walls of heat pipes work below). We'll have to go back to the basics - to an all-copper cooling system. And so that the limited performance of the cooler does not affect the measurements, we add a kilogram copper plate - a heat accumulator.


    The result is shocking - the same -19 with both one and two stages. Ambient temperature - -10. Those. with zero load we barely squeezed out a measly 9 degrees of difference.

    Roll out the heavy artillery

    It turned out that cold storage plant #7 was not far from me, and I decided to stop by with a cardboard box. He returned with 5 kilograms of dry ice (sublimation temperature -78C). We lower the copper structure there - connect the current - at 12V the temperature immediately begins to rise, at 5V it drops by 1 degree per second, and then quickly increases. All hopes are dashed...

    Conclusions and video for dessert

    The efficiency of conventional Chinese Peltier elements drops quickly at temperatures below zero. And while it is still possible to cool a can of cola with apparent efficiency, temperatures below -20 cannot be achieved. And the problem is not with specific elements - I tried elements different models from 3 different sellers - the behavior is the same. It seems like cryogenic stages require elements from other materials (and perhaps each stage requires a different element material).

    Well, with the remaining dry ice you can do the following:

    PS. And if you mix dry ice with isopropyl alcohol, you get liquid nitrogen for the “poor” - it is also fun to freeze and break flowers, etc. It’s just because alcohol doesn’t boil upon contact with skin that it’s much easier to get frostbite.

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