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 conductivity, so that at the top there are one sequence of connections (n->p), and at the bottom the 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 use it effectively, you need to use a cooling radiator - I used a radiator from computer processor, maybe with a cooler. How better 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

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 maximum difference temperatures between the hot and cold sides are 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

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

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 made a measly 9 degrees of difference.

Roll out the heavy artillery

Conclusions and video for dessert

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.

The Peltier element has been known to the world for a long time. Back in the 18th century, the French watchmaker Jean-Charles Peltier quite by accident discovered a new effect at the boundary of two metals: bismuth and antimony. It consisted of a sharp change in the temperature of a drop of water placed between the contacts, which turned into ice when current was applied. This property became new for the watchmaker, because until that moment no scientist in the world had ever presented such information in his materials.

Although the effect was interesting, it did not find practical application at that time, which was due to the small amount of electronic equipment that would require intensive cooling. After 2 centuries The scientist’s discovery was remembered because there was an urgent need to manufacture a device that could provide high-quality cooling of the heating microprocessor crystal.

As a result of numerous studies in this area and a huge number of practical experiments, scientists have found that a thermoelectric couple can produce enough cold to normal operation almost any microprocessor. And thanks to their small size, they have learned to integrate them into microcircuit housings, thus providing their own internal cold generator.

The discovery of Jean-Charles Pelte was a huge impetus for the entire mobile phone industry. refrigeration units. Today the property of a thermoelectric element used in the following techniques:

• portable refrigerators;
• car air conditioners;
• portable coolers;
• cameras, telescopes and much more.

They are actively used for cooling microprocessors and other electronic components. In addition to the direct cooling effect, many began to use the Peltier element as a generator. An example of what could be flashlight with 3 elements.

Few people know that in order to carry out radio communication with the command, soldiers put a special pot on the fire and brewed tea, prepared porridge and other household items, and at the same time carried out the transmission necessary information via portable radio.

How to make a Peltier element with your own hands?

Many people are interested in the question, what is a Peltier element with their own hands, how to make it at home? This will require highly precise dosed addition of various substances and materials. Make at home similar device impossible, because it requires technology and the necessary metal processing methods. Also, especially pure materials are required in the same laboratories, which is impossible to achieve at home. Therefore, to the question of how to do thermoelectric module Peltier, the answer can be unequivocal. No way. But to build an effective cooling system, existing skills are quite enough.

Making a Peltier element from diodes

There is an opinion about what can be done diode thermoelectric module. The fact is that each pair of dissimilar semiconductors is two materials with p and n conductivities. And a diode is just that. To detect changes in conductivity when heated, it is necessary to select certain elements. But no diodes will help to obtain a low temperature on the surface of the device. When submitting high current You can only achieve warming up.

Radio amateurs use low-power diodes in a glass case as a temperature sensor. When they are connected in the opposite direction and warmed up, the junction begins to open and pass current in the opposite direction. But it will not generate electricity.

How does the Pelte element work?

A Peltier thermoelectric module in a simplified form is a pair of plates made of different metals, which can be bismuth, antimony, tellurium or selenium. Between them there is a pair of n- and p-type semiconductors with different conductivities. All formed by different metals thermoelectric couples connected in series into a single circuit. As a result, a kind of matrix is ​​formed from large quantity separate thermocouples located between two ceramic plates.

The thermoelectric module formed by thermocouples is manufactured in a single small-sized housing. When they are sequential or parallel connection it is possible to achieve an enhanced cooling or production effect electrical energy. In cooler mode, the positive terminal of the matrix is ​​connected to the first pair with an n-type conductor, the negative contact is connected to p-type conductors. Special ceramics based on aluminum oxide and nitride are used as external linings. This ensures the best heat transfer performance on both sides at both high and low temperatures.

Number of thermocouples in the module is not limited by anything and can be up to several hundred. The more there are, the better the cooling effect is felt. To increase the efficiency of the Peltier element, a radiator with the largest heat transfer area is attached to its cold side. The difference in temperature between the plates should be at least two tens of degrees.

When voltage is applied to the plates, one side becomes hot and the other cold. When the polarity of the supply voltage changes, the temperature of the plates changes places.

Considering the complexity and manufacturability, do it yourself thermoelectric element not possible. But still there are craftsmen who offer their developments. The effect is observed, but it is impossible to achieve an increase in efficiency without a special research laboratory. You can even find a video on this topic with step-by-step guidance.

Features of the Peltier element

To the features element based on bimetallic pairs should include:

Formula display

The Peltier effect involves the flow of current through the contact of two metals with different conductivities. As a result, heat or cold is released, which depends on the direction of current flow.

In formulaic expression, the Peltier effect can be depicted:

Q p=P12 j, where P12 is the Peltier coefficient. The indicator depends on the type of metal used and its thermoelectric properties.

In addition to the advantages, the device also has some disadvantages, which include:

Low efficiency. In order to obtain a significant temperature difference, it is necessary to supply a sufficiently large current to the plates.

To effectively remove thermal energy, it is necessary to provide a radiator.

Generator mode of the Peltier element

The discovery of Jacques-Charles Peltier literally turned the world upside down, since the device can be used as a universal generator of heat and cold. In addition to these functions, another important effect was noted - the generator mode. If the warm side of the device is heated and the cold side is cooled, then a potential difference occurs at the terminals, and when the circuit is closed, current begins to flow.

Generator based on a Peltier element You can do it yourself and it doesn’t require any special skills. But you should understand that the material used by Chinese developers does not have ideal characteristics allowing you to obtain maximum energy. Available thermoelectric modules on sale are sufficient for:

• charging mobile devices;
• power supply for LED lighting;
• manufacturing an autonomous radio receiver and other purposes.

You can find a lot of videos on this topic from detailed description all stages. Therefore, if you want to make a thermoelectric module to generate energy, then this is quite possible.

The first step is to order the required number of Peltier elements, taking into account their characteristics. A device with a power of 10 W on the same e-Bay costs $15. And this will be quite enough to charge smartphones. Next, it is necessary to ensure effective heat removal. For these purposes, a system can be designed liquid cooling with natural circulation. And heat the hot side with any heat source, including open fire. As a result any radio amateur can make an excellent thermoelectric generator himself, which you can take with you on a hike, fishing or to the country house.

One standard cell produces 5 V and 1 W of power, which is enough for small lighting. For example, for making a flashlight heated by the heat of your hands. Ready-made elements with output voltages up to 12 V are also available for sale.

Portable thermoelectric stove with generator mode

Today you can find a lot of ways to make a fairly efficient thermoelectric generator based on a Peltier element with your own hands. As one of them - portable stove with firebox from old computer unit nutrition. The Peltier thermoelectric element itself is attached to one of the sides of the case through thermal paste with an impressively sized radiator. This installation will allow you to get heat in any convenient place, cook food and charge your phone.