home > Computer > Do-it-yourself thermogenerator based on Peltier elements. How to make your own generator from Peltier elements

Do-it-yourself thermogenerator based on Peltier elements. How to make your own generator from Peltier elements

Well, all the graphs are drawn, all the tables are filled out, now you can dream. In general, if you estimate the energy consumption on a hike to the maximum, you get the following:
GPS navigator - 0.3 W x 10 h = 3 W*h per day;
camera (Canon DSLR) - 8 Wh battery for 4 days = 2 Wh per day;
video camera (video recorder for capturing interesting moments of the trip, about 1 hour of video per day) - 1.6 Wh per day;
cell phone - about 0.2 Wh per day;
led flashlight to illuminate the parking lot in the evening - 2 W*h per day.
Total we get: 3 + 2 + 1.6 + 0.2 + 2 = 8.8 Wh per day. Taking into account the losses when charging the batteries of these devices and unexpected expenses, you can easily round this figure to 10 Wh per day, which is approximately equal to three AA NiMH batteries (3.2 Wh each). We will assume that this is the amount of electricity that allows you to comfortably travel along a previously planned route without limiting your creative urges. This calculation is more or less correct for a solo outing or a group of two people. If there are more people, then an additional consumer is added for each person, be it a cell phone or another camera. I think that for each “extra” participant you can safely add 1 Wh, that is, for a group of 6 people, a comfortable level of energy consumption will be 14 Wh or about 4.5 AA batteries. Let's assume that the hike lasts 10 days, then for a group of 2 people you will need 100 Wh of energy, this is 31 NiMH batteries with a total weight of 31 x 31.5 = 976.5 g. That is, almost 1 kg of batteries. If you take alkaline batteries, the best ones give out 2.2 Wh and you will need 45 of them. I don’t know their weight, but even if they are 25 g each, the total adds up to more than a kilogram. For a group of 6 people, the total amount of electricity is 140 Wh, which is almost 44 batteries weighing 1386 g or 64 batteries weighing even more. If you take with you LiPo batteries, the kind modellers use, then for two people it will be a battery weighing 100 Wh ÷ 160 Wh/kg = 0.625 kg or 625 g. For a group of 6 people the mass LiPo battery will be 875 g.
Now let's figure out how things are going with the thermogenerator. Let’s say we have a TEC1-12709 module (or modules), heat it no higher than 150 °C, cool it in a stream with a temperature of 15 °C, that is, on the cold side it will be 20 °C, the temperature difference is 150 - 20 = 130 °C. For such a value of temperature difference I do not have an efficiency indicator, I will have to count. We take two maximum values on the graph of efficiency versus current for TEC1-12709, for example 13.6 mW/°C for an average temperature difference of 71 °C and 15.7 mW/°C for 87 °C and calculate by what amount the efficiency has increased at increasing the temperature difference by 87 - 71 = 16 °C. It turns out to be 2.1 mW/°C. And then in proportion: if an increase in the difference of 16 °C led to an increase in efficiency by 2.1 mW/°C, then an increase in the difference by 130 - 87 = 43 °C will lead to an increase in efficiency by (43 x 2.1) ÷ 16 = 5.6 mW/°C. This means that the efficiency at a temperature difference of 130 °C will be equal to 15.7 + 5.6 = 21.3 mW/°C. As a result, we get 21.3 x 130 = 2769 mW or 2.8 W. This value is quite close to reality, judging by the fact that in some video experiments two modules produced 4...6 W. In order to obtain 10 Wh of energy using one module, the generator must operate for 10 ÷ 2.8 = 3.57 hours, and for 14 Wh - 5 hours. That is, if you use a thermogenerator consisting of 2 Peltier elements, then generating electricity even for a large group does not take very long.
The only major problem with generating electricity while camping using this method is heat dissipation on the cold side. The best and most optimal is water cooling, since water has a high heat capacity. In this regard, water tourists are luckier than cyclists: their method of transportation is connected specifically with water, and if you think through the design of the generator (it’s very strange why it has not yet been thought out and implemented on an industrial scale), then they can generate electricity while driving. The generator is partially submerged in water and partially floats on the surface. Fuel is loaded into the furnace as it is consumed, and everything is cooled with water from the outside. Fuel is collected and prepared at the rest stop.
If you don’t want to bother with collecting firewood and pine cones, then you can think about the design of a gas stove. It's worth doing a little math here. So we have:
liquefied gas cylinder for gas burners with fuel weighing 450 g;
composition: isobutane - 72%, propane - 22%, butane - 6%, in terms of weight this is 324 g, 99 g and 27 g, respectively;
the calorific values for these gases are 49.22 MJ/kg, 48.34 MJ/kg and 49.34 MJ/kg, respectively.
After multiplication and addition, we have 22.07 MJ in one liquefied gas cylinder. We take the efficiency of our generator to be 1%, therefore we get 220 kJ as electricity, which is 61.3 Wh. What can you compare it to? Well, for example, with 19 NiMH AA batteries. Not a lot and quite expensive, gas is not cheap.
Since using gas is expensive, you can come up with something using liquid fuel, such as gasoline. I scoured the Internet a little for a cheap catalyst for catalytic burners, but I couldn’t find anything other than chromium (VI) oxide obtained from ammonium dichromate. Yes, and not everything is so smooth with it, but if you wish, through a certain amount of experimentation you can achieve stable positive results here too. Catalytic heating pads made in China most likely use trace amounts of platinum group elements. If only there was a catalyst like in this heating pad, but larger for Peltier elements. The result would be a compact and lightweight generator. The calorific value of gasoline is 44.5 MJ/kg, density 0.74 kg/l, from one liter of gasoline we have 33 MJ of energy, at 1% efficiency this is 330 kJ or 91.6 Wh of electricity (28 AA batteries). More a budget option, but still collect and prepare what is available in nature free fuel is naturally more profitable, and it does not have one very unpleasant feature inherent in those supplies that are bought in the store - it does not run out at the most inopportune moment.

IN modern world a large number of household appliances and other devices run on electricity. At the same time, while traveling, you have to carry with you chemical current sources capable of generating electricity. But you can also make a thermogenerator with your own hands. This will require some materials, equipment and certain knowledge.

Types of devices

In a circuit of dissimilar conductors at variable temperatures, thermal emf may arise at the points of contact. Based on this, the so-called “Peltier” module was developed and created. It consists of 2 ceramic plates, between which a bimetal is installed. On admission electric current one of the plates gradually begins to heat up, while the other simultaneously cools. This ability allows you to make refrigerators from such elements.

But the reverse process can also be observed, when a temperature difference is maintained at the contact points. In this case, the plates will begin to generate electric current. Such a module can be used to generate a small amount of electrical energy.

Module operation

Electricity thermogenerators operate according to a certain principle. Thus, depending on the direction of the current, absorption or release of heat is observed in the contact of dissimilar conductors. It depends on the direction of the electricity. In this case, the current density is the same, but the energy is different.

Heating of the crystal lattice is observed if the energy flowing out is less than that entering into contact. When the direction of the current changes, the reverse process occurs. The energy in the crystal lattice decreases, so the device cools.

The most popular thermoelectric module, consisting of conductors of types p and n, which are connected to each other through copper analogues. In each of the elements there are 4 transitions that are cooled and heated. Due to the temperature difference, it is possible to create a thermoelectric generator.

Advantages and disadvantages

Regardless of whether it is purchased or made by hand, a thermoelectric generator has a number of advantages. So, the most significant of them include:

Small dimensions.
Ability to work in both heating and cooling devices.
When the polarity changes, the process is reversible.
There are no moving elements that wear out quickly enough.

Despite the significant advantages, such a device has some disadvantages:

Insignificant efficiency (only 2−3%).
The need to create a source responsible for the temperature difference.
Significant energy consumption.
High cost.

Based on the above negative and positive qualities, we can say that such a device is advisable to use if it is necessary to recharge a mobile phone, tablet computer or ignition LED light bulb.

DIY making

You can make a thermoelectric generator with your own hands. For this purpose you will need some elements:

The wires passing between the converter and the module must be insulated with a heat-resistant compound or conventional sealant. The device must be assembled in the following sequence:

All that remains of the power supply is the housing.
With the cold side, you need to glue the Peltier module to the radiator.
Having previously cleaned and polished the surface, you need to glue the element on the other side.
It is necessary to solder wires from the input of the voltage converter to the outputs of the plate.

In this case, for correct operation, the thermal generator must be endowed with the following characteristics: output voltage - 5 volts, type of output for connecting the device - USB (or any other depending on preference), minimum load power must be 0.5 A. In this case, you can use any Type of fuel.

Checking the mechanism is quite simple. You can put several dry and thin twigs inside. Set them on fire, and after a few minutes connect some device, for example, a phone to recharge. Assembling a thermogenerator is not difficult. If everything is done correctly, it will last for many years on trips and hikes.

A huge number of electronic devices absorb electrical energy, which must be constantly renewed. While on the road, you have to carry chemical current sources with you or generate electricity from mechanical energy using complex and bulky devices.

Type of thermoelectric generator

Even earlier, Seebeck discovered the occurrence of thermo-EMF in a circuit of dissimilar conductors when maintaining different temperatures at the point of contact. Based on thermoelectric effects, a so-called Peltier element or module was created, which consists of 2 ceramic plates with a bimetal located between them. When electric current is applied through them, one side of the plate heats up and the other cools, which makes it possible to create refrigerators from them. The figure below shows the modules different sizes, used in technology.

Peltier modules of different sizes

The process is reversible: if you maintain a temperature difference across the elements on both sides, they will generate an electric current, which allows the device to be used as a thermoelectric generator to generate a small amount of electricity.

The Peltier effect is the release of heat at the point of contact of dissimilar conductors when electric current flows through them.

Operating principle of modules

At the contact of dissimilar conductors, heat is released or absorbed depending on the direction of the electric current. The flow of electrons has potential and kinetic energy. The current density in the contacting conductors is the same, but the energy flux densities are different.

If the energy flowing into the contact is greater than the energy flowing out of it, this means that electrons are slowed down at the point of transition from one region to another and heat up the crystal lattice (the electric field slows down their movement). When the direction of the current changes, the reverse process of electron acceleration occurs, when energy is taken from the crystal lattice and its cooling occurs (the directions of the electric field and the movement of electrons coincide).

The energy difference of charges at the boundary of semiconductors is the highest and the effect manifests itself most strongly there.

Peltier module

The most common is the thermoelectric module (TEM), which is p- and n-type semiconductors connected to each other through copper conductors.

Diagram of the operating principle of the module

In one element there are 4 transitions between metal and semiconductors. At closed circuit The flow of electrons moves from the negative pole of the battery to the positive, sequentially passing through each transition.

Near the first copper-p-type semiconductor transition, heat is released in the semiconductor zone as electrons move to a state with lower energy.

Near the next boundary with the metal in the semiconductor, heat is absorbed due to the “sucking out” of electrons from the p-conductivity zone under the influence of an electric field.

In the third transition, electrons enter the n-type semiconductor, where they have higher energy than in the metal. In this case, energy is absorbed and the semiconductor is cooled near the transition boundary.

The last transition is accompanied by a reverse process of heat release in the n-semiconductor due to the transition of electrons to a zone with lower energy.

Since the heating and cooling transitions are in different planes, the Peltier element will be cooled from above and heated from below.

In practice, each element contains a large number of heating and cooling transitions, which leads to the formation of a noticeable temperature difference, which makes it possible to create a thermoelectric generator.

What does the module structure look like?

The Peltier element contains a large number of p- and n-type semiconductor parallelepipeds, connected in series with metal jumpers - thermal contacts, the other side in contact with the ceramic plate.

Bismuth telluride and silicon germanide are used as semiconductors.

Advantages and disadvantages of TEM

The advantages of a thermoelectric module (TEM) include:

small sizes;
the ability to operate both coolers and heaters;
reversibility of the process when changing polarity, allowing you to maintain an exact temperature value;
absence of moving elements that usually wear out.

Disadvantages of modules:

low efficiency (2-3%);
the need to create a source that provides a temperature difference;
significant energy consumption;
high price.

Despite the disadvantages, TEMs are used where high energy costs are not important:

cooling of chips, parts of digital cameras, diode lasers, quartz oscillators, infrared detectors;
the use of TEM cascades to achieve low temperatures;
creation of compact refrigerators, for example, for cars;
thermoelectric generator for charging mobile devices.

If the productivity of TEG is low, it is advisable to use it in field conditions, where it is necessary to obtain electricity for charging. cell phone or LED light bulb. The simplicity of the design allows you to make an electric generator with your own hands.

Alternative sources are also solar panels or a wind generator. The former require special conditions - the presence of sunlight, which may not always be available. Another source is large and requires wind. Another disadvantage is the presence of moving parts that reduce reliability and are heavy.

Industrial thermogenerators

BioLite has developed a new model for hiking that allows you to cook food in a compact, portable wood-burning stove and at the same time charge your mobile device from the built-in TEG.

Compact portable wood stove

The device will come in handy everywhere: fishing, hiking, at the dacha. Anything that burns can be used as fuel.

When fuel is burned in the furnace, heat is transferred through the wall to the module, which generates electricity. At a voltage of 5V, the output power is 2-4 W, which is enough to charge many types of mobile devices and operate LED lighting. The red arrow shows the direction of movement of heat, the blue arrow shows cold air into the furnace, the yellow arrow shows the supply of electricity to rotate the air intake fan and to the generator output via USB.

Scheme of operation of BioLite TEG on wood

The Indigirka generator furnace, developed by the St. Petersburg company Kryotherm, has the following characteristics:

thermal power – 6 kW;
weight – 56 kg;
dimensions – 500x530x650 mm;
email power at voltage 5V – 60 W.

The stove is a conventional heating and cooking stove, with thermoelectric generators attached on both sides.

What does the Indigirka thermoelectric generator furnace look like?

The device is quite convenient, but the price is impressive - 50 thousand rubles. Although the stove is intended for camping conditions, it will clearly not be affordable for ordinary hunters and fishermen. As a heating system, it is no better than conventional and cheaper models.

If you attach a TEG to a simple stove, the homemade device will work perfectly.

DIY TEG

To assemble a thermoelectric generator with your own hands, you need the following elements:

Module. To generate electric current, not all modules can be used, but only those that can withstand heating up to 300-400 0 C. Having a heating reserve is necessary, since even with slight overheating the element fails. The most common models are the TEC1-12712 type in the form of square plates with a side size of 40, 50 or 60 mm.

If you take maximum size, it is enough to use one element in a DIY design. The first 3 digits of the marking - 127 - mean how many elements are contained in 1 plate. The last numbers show the maximum permissible current, which is 12 A.

Boost converter. It is required to receive DC voltage 5V. The generator may produce less voltage, which needs to be increased. The devices are produced foreign (types 5V NCP1402 and MAX 756) and domestic (3.3V/5V EK-1674). To charge your mobile phone, you should choose a device with a USB connector.
Heater. The simplest options are a fire, a candle, a homemade lamp or a miniature stove.
Cooler. The easiest way is to use water or, in winter, snow.
Connecting elements. Equipment is needed to create the maximum possible temperature difference between the two sides of the plate. Here the choice is up to the craftsmen; they most often use 2 mugs or pans of different sizes, the handles of which are sawed off and where one is inserted inside the other. A module is placed between them and secured with thermal paste. 2 wires are soldered to it and connected to a voltage converter.

To increase the efficiency of the generator, the bottoms of the metal surfaces of mugs or pans in contact with the generator plate should be polished. In addition, heat-resistant sealant is applied to the spaces between the bottoms of the smaller and larger mugs. Then the heat from heating will be localized at the location of the module.

The wires between the module and the converter are protected with heat-resistant insulation and sealant.

Water is poured into the inner mug, and the entire structure is put on fire. After a few minutes, you can check the output voltage with a multimeter.

In order to assemble a thermoelectric generator yourself, you will need the following materials:

Peltier element";
a housing from an old computer power supply for making a mini-firebox;
voltage converter with USB output to 5V with input 1-5V;
radiator with processor cooler;
thermal paste.

The costs here are small and the device is quite capable of charging mobile phone. The self-assembled generator is an analogue of the foreign model from BioLite. If assembled carefully, the device will work reliably for a long time, because there is nothing to break here. It is only important not to overheat the Peltier element, which could cause it to fail.

When using a cooler to cool a radiator, it should be connected to a generator, after which part of the generated energy will be spent on cooling.

Despite the additional energy consumption, the efficiency of the installation will increase. If the radiator gets very hot during operation, it is necessary to take measures to cool it. Otherwise, the generator's operating efficiency will be low.

The characteristics of the generator are as follows:

output voltage – 5V;
load power – 0.5A;
output type – USB;
fuel - any.

The device is manufactured as follows:

disassemble the power supply, leaving the case;
glue the Peltier module to the radiator with thermal paste. It is necessary to glue with the cold side where the marking is applied;
clean and polish the outer side surface of the power supply housing and glue the element to it with the other side (together with the radiator);
Solder the wires from the input of the voltage converter to the terminals of the plate.

You can check the TEG by placing thin branches inside the firebox and setting them on fire. After a few minutes, you can connect your phone, which requires a temperature difference of 100 0 C between the sides of the module to recharge. The figure below shows the assembled generator.

DIY assembled thermoelectric generator

When using TEG, it is necessary to observe the polarity of connecting the modules.

Video. Thermoelectric generator

The Peltier effect makes it possible to create small generators and refrigerators that operate without moving parts. Improving the quality of modules and reducing the energy consumption of mobile devices allows you to create a thermoelectric generator with your own hands for charging batteries and supplying power. big amount energy various devices, where efficiency is not particularly important.

Refrigeration equipment has become so firmly established in our lives that it is even difficult to imagine how we could manage 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 it is?

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 cooling of the metal from which the second conductor is made.

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 power polarity 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 reach 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 it 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:

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.
The number of thermocouples in the module shown in the photo is 127.
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's give detailed examples use of thermoelectric modules.

Refrigerator using Peltier elements

Thermoelectric refrigeration units are significantly inferior in performance to compressor and absorption analogues. 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. The greater the temperature difference 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 of 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 heat source with a power of 100-170 W (corresponding to most modern CPU models), you will need to spend 400-680 W, which requires installation powerful block nutrition.

The second pitfall is that 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 power of the module 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 service.

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 of employees;
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 using thermoelectric elements is 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 this case the efficiency of the device is quite satisfactory.

How to connect?

There will be no problems connecting the module; a constant voltage must be applied to the output wires; 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:

connect the probes to the module terminals;
bring the lit lighter to one of the sides;
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?

It is almost impossible to make a homemade module at home, especially since there is no point in doing so, 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.

The input of such a converter is supplied with a voltage in the range of 0.8-5.5 V, and 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.

> Generators > Thermoelectric generator

Type of thermoelectric generator

Even earlier, Seebeck discovered the occurrence of thermo-EMF in a circuit of dissimilar conductors when maintaining different temperatures at the point of contact.

Based on thermoelectric effects, a so-called Peltier element or module was created, which consists of 2 ceramic plates with a bimetal located between them.

When electric current is applied through them, one side of the plate heats up and the other cools, which makes it possible to create refrigerators from them. The figure below shows modules of different sizes used in technology.

Peltier modules of different sizes

The Peltier effect is the release of heat at the point of contact of dissimilar conductors when electric current flows through them.

Operating principle of modules

The energy difference of charges at the boundary of semiconductors is the highest and the effect manifests itself most strongly there.

Peltier module

The most common is the thermoelectric module (TEM), which is p- and n-type semiconductors connected to each other through copper conductors.

Diagram of the operating principle of the module

In one element there are 4 transitions between metal and semiconductors. In a closed circuit, the flow of electrons moves from the negative pole of the battery to the positive, sequentially passing through each transition.

Near the first copper-p-type semiconductor transition, heat is released in the semiconductor zone as electrons move to a state with lower energy.

Near the next boundary with the metal in the semiconductor, heat is absorbed due to the “sucking out” of electrons from the p-conductivity zone under the influence of an electric field.

The last transition is accompanied by a reverse process of heat release in the n-semiconductor due to the transition of electrons to a zone with lower energy.

Since the heating and cooling transitions are in different planes, the Peltier element will be cooled from above and heated from below.

What does the module structure look like?

Bismuth telluride and silicon germanide are used as semiconductors.

Advantages and disadvantages of TEM

The advantages of a thermoelectric module (TEM) include:

small sizes;
the ability to operate both coolers and heaters;
reversibility of the process when changing polarity, allowing you to maintain an exact temperature value;
absence of moving elements that usually wear out.

Disadvantages of modules:

low efficiency (2-3%);
the need to create a source that provides a temperature difference;
significant energy consumption;
high price.

Despite the disadvantages, TEMs are used where high energy costs are not important:

cooling of chips, parts of digital cameras, diode lasers, quartz oscillators, infrared detectors;
the use of TEM cascades to achieve low temperatures;
creation of compact refrigerators, for example, for cars;
thermoelectric generator for charging mobile devices.

With low productivity, it is advisable to use TEGs in camping conditions, where it is necessary to obtain electricity to charge a cell phone or LED light bulb. The simplicity of the design allows you to make an electric generator with your own hands.

Industrial thermogenerators

BioLite has developed a new model for hiking that allows you to cook food in a compact, portable wood-burning stove and at the same time charge your mobile device from the built-in TEG.

Compact portable wood stove

The device will come in handy everywhere: fishing, hiking, at the dacha. Anything that burns can be used as fuel.

When fuel is burned in the furnace, heat is transferred through the wall to the module, which generates electricity.

At a voltage of 5V, the output power is 2-4 W, which is enough to charge many types of mobile devices and operate LED lighting.

The red arrow shows the direction of movement of heat, the blue arrow shows cold air into the furnace, the yellow arrow shows the supply of electricity to rotate the air intake fan and to the generator output via USB.

Scheme of operation of BioLite TEG on wood

The Indigirka generator furnace, developed by the St. Petersburg company Kryotherm, has the following characteristics:

thermal power – 6 kW;
weight – 56 kg;
dimensions – 500x530x650 mm;
email power at voltage 5V – 60 W.

The stove is a conventional heating and cooking stove, with thermoelectric generators attached on both sides.

What does the Indigirka thermoelectric generator furnace look like?

If you attach a TEG to a simple stove, the homemade device will work perfectly.

DIY TEG

To assemble a thermoelectric generator with your own hands, you need the following elements:

Module. Not all modules can be used to generate electric current, but only those that can withstand heating up to 300-4000C. Having a heating reserve is necessary, since even with slight overheating the element fails. The most common models are the TEC1-12712 type in the form of square plates with a side size of 40, 50 or 60 mm.

If we take the maximum size, it is enough to use one element in a DIY design. The first 3 digits of the marking - 127 - mean how many elements are contained in 1 plate. The last numbers show the maximum permissible current, which is 12 A.

Boost converter. It is necessary to obtain a constant voltage of 5V. The generator may produce less voltage, which needs to be increased. The devices are produced foreign (types 5V NCP1402 and MAX 756) and domestic (3.3V/5V EK-1674). To charge your mobile phone, you should choose a device with a USB connector.
Heater. The simplest options are a fire, a candle, a homemade lamp or a miniature stove.
Cooler. The easiest way is to use water or, in winter, snow.
Connecting elements. Equipment is needed to create the maximum possible temperature difference between the two sides of the plate. Here the choice is up to the craftsmen; they most often use 2 mugs or pans of different sizes, the handles of which are sawed off and where one is inserted inside the other. A module is placed between them and secured with thermal paste. 2 wires are soldered to it and connected to a voltage converter.

The wires between the module and the converter are protected with heat-resistant insulation and sealant.

Water is poured into the inner mug, and the entire structure is put on fire. After a few minutes, you can check the output voltage with a multimeter.

In order to assemble a thermoelectric generator yourself, you will need the following materials:

Peltier element";
a housing from an old computer power supply for making a mini-firebox;
voltage converter with USB output to 5V with input 1-5V;
radiator with processor cooler;
thermal paste.

The costs here are small and the device is quite capable of charging a mobile phone. The self-assembled generator is an analogue of the foreign model from BioLite. If you assemble it carefully, the device will work reliably for a long time, since there is nothing to break here. It is only important not to overheat the Peltier element, which could cause it to fail.

When using a cooler to cool a radiator, it should be connected to a generator, after which part of the generated energy will be spent on cooling.

The characteristics of the generator are as follows:

output voltage – 5V;
load power – 0.5A;
output type – USB;
fuel - any.

The device is manufactured as follows:

disassemble the power supply, leaving the case;
glue the Peltier module to the radiator with thermal paste. It is necessary to glue with the cold side where the marking is applied;
clean and polish the outer side surface of the power supply housing and glue the element to it with the other side (together with the radiator);
Solder the wires from the input of the voltage converter to the terminals of the plate.

You can check the TEG by placing thin branches inside the firebox and setting them on fire. After a few minutes, you can connect your phone, which requires a temperature difference of 1000C between the sides of the module to recharge. The figure below shows the assembled generator.

DIY assembled thermoelectric generator

When using TEG, it is necessary to observe the polarity of connecting the modules.

. Thermoelectric generator

The Peltier effect makes it possible to create small generators and refrigerators that operate without moving parts. Improving the quality of modules and reducing the energy consumption of mobile devices allows you to create a thermoelectric generator with your own hands to charge batteries and supply a small amount of energy to various devices where efficiency is not particularly important.

Source: https://elquanta.ru/generatory/termoehlektricheskijj-generator.html

In order to obtain electricity, you need to find a potential difference and a conductor. People have always strived to save money, and in an era of ever-increasing utility bills, this is not at all surprising.

Today there are already ways in which a person can obtain free electricity that is free for him.

As a rule, these are certain do-it-yourself installations, which are based on an electric generator.

A thermoelectric generator is a device that allows you to generate electrical energy from heat. This is an excellent steam source of electricity, although with low efficiency.

Thermoelectric generators, which use the operating principle of conventional thermocouples, are used as a device for directly converting heat into electrical energy.

Essentially, thermoelectricity is direct conversion heat into electricity in liquid or solid conductors, and then the reverse process of heating and cooling the contact of different conductors by means of electric current.

Heat generator device:

The thermal generator has two semiconductors, each consisting of a certain number of electrons;
They are also interconnected by a conductor, above which there is a layer capable of conducting heat;
A thermionic conductor is also attached to it for transmitting contacts;
Next comes the cooling layer, followed by the semiconductor, whose contacts lead to the conductor.

Unfortunately, a heat and power generator is not always able to operate with high power, so it is used mainly in everyday life, and not in production.

Today, the thermoelectric converter is almost never used anywhere. It “requests” a lot of resources, it also takes up space, but the voltage and current that it can generate and convert are very small, which is extremely unprofitable.

Solar thermal generator of electricity and radio waves

Sources of electrical energy can be very different. Today, the production of solar thermoelectric generators has become increasingly popular. Such installations can be used in lighthouses, in space, in cars, and in other areas of life.

Solar thermal generators are a great way to save energy resources

RTG (stands for radionuclide thermoelectric generator) works by converting the energy of isotopes into electrical energy. This is a very economical way that allows you to get practically free electricity and the possibility of lighting in conditions of no electricity.

Features of RTG:

It is easier to obtain a source of energy from the decay of isotopes than, for example, doing the same thing by heating a burner or kerosene lamp;
The generation of electricity and the decay of particles is possible with the presence of special isotopes, because the process of their decay can last for decades.

When using such an installation, you need to understand that when working with old models of equipment, there is a risk of receiving a dose of radiation, and it is very difficult to dispose of such a device. If destroyed incorrectly, it can act as a radiation bomb.

When choosing an installation manufacturer, it is better to choose companies that have already proven themselves. Such as Global, Altec, Tgm, Kryotherm, Termiona.

By the way, another good way to get electricity for free is a generator that collects radio waves. It consists of pairs of film and electrolytic capacitors, as well as low-power diodes. An insulated cable of about 10-20 meters is used as an antenna and another grounding wire is attached to a water or gas pipe.

How to make a Peltier element with your own hands

A typical Peltier element is a plate assembled from parts of various metals, with connectors for connecting to a network. Such a plate passes current through itself, heating up on one side (for example, up to 380 degrees) and working from the cold on the other.

The Peltier element is a special thermoelectric converter that operates on the same principle of supplying electric current

This thermogenerator has the opposite principle:

One side can be heated by burning fuel (for example, a wood fire or some other raw material);
The other side, on the contrary, is cooled by a liquid or air heat exchanger;
Thus, current is generated on the wires, which can be used according to your needs.

True, the device’s performance is not very high, and the effect is not impressive, but, nevertheless, such a simple homemade module can easily charge a phone or connect an LED flashlight.

This generator element has its advantages:

Silent operation;
The ability to use what is at hand;
Light weight and mobile.

Such homemade stoves have begun to gain popularity among those who like to spend the night in the forest by the fire, taking advantage of the gifts of the earth and who are not averse to getting electricity for free.

The Peltier module is also used to cool computer boards: the element is connected to the board and as soon as the temperature becomes higher than permissible, it begins to cool the circuits. On one side, cold air space enters the device, and on the other, hot air. The 50X50X4mm (270w) model is popular. You can buy such a device in a store or make it yourself.

By the way, connecting a stabilizer to such an element will allow you to get an excellent output Charger for household appliances, and not just a thermal module.

To make a Peltier element at home, you need to take:

Bimetal conductors (about 12 pieces or more);
Two ceramic plates;
Cables;
Soldering iron.

The manufacturing scheme is as follows: the conductors are soldered and placed between the plates, after which they are tightly fixed. In this case, you need to remember about the wires that will then be attached to the current converter.

The scope of use of such an element is very diverse. Since one of its sides tends to cool, using this device you can make a small camping refrigerator, or, for example, a car air conditioner.

But, like any device, this thermocouple has its pros and cons. The advantages include:

Compact size;
Possibility of working with cooling or heating elements together or each separately;
Quiet, almost silent operation.

Minuses:

The need to control temperature differences;
High energy consumption;
Low level of efficiency at high cost.

Simple homemade generator

Despite the fact that these devices are not popular now, this moment there is nothing more practical than a thermogenerator unit, which is quite capable of replacing an electric stove when traveling, lighting bulb or help out if the charger for your mobile phone is broken, power the power window. Such electricity will also help at home in case of a power outage. You can get it for free, one might say, on a ball.

So, to make a thermoelectric generator, you need to prepare:

Voltage regulator;
Soldering iron;
Any body;
Radiators for cooling;
Thermal paste;
Peltier heating elements.

Device assembly:

First, the body of the device is made, which should be without a bottom, with holes at the bottom for air and at the top with a stand for a container (although this is not necessary, since the generator may not work on water);
Next, a Peltier element is attached to the case, and a cooling radiator is attached to its cold side through thermal paste;
Then you need to solder the stabilizer and the Peltier module, according to their poles;
The stabilizer should be very well insulated to prevent moisture from getting in;
It remains to check its operation.

By the way, if it is not possible to get a radiator, you can use a computer cooler or a car generator instead. Nothing bad will happen from such a replacement.

The stabilizer can be purchased with a diode indicator that will give a light signal when the voltage reaches the specified value.

Such a heat generator warms up in about 30 seconds, but the voltage it consumes already reaches several volts. After a few minutes of warming up, the generator will be ready for use.

Do-it-yourself thermocouple: process features

What is a thermocouple? A thermocouple is an electrical circuit consisting of two different elements with an electrical contact.

The thermoEMF of a thermocouple with a temperature difference of 100 degrees at its edges is approximately 1 mV. To make it higher, several thermocouples can be connected in series. The result is a thermopile, the thermoEMF of which will be equal to the total sum of the EMF of the thermocouples included in it.

The thermocouple manufacturing process is as follows:

A strong connection is created between the two different materials;
Take a voltage source (for example, car battery) and wires of different materials pre-twisted into a bundle are connected to one end;
At this time, you need to bring the lead connected to the graphite to the other end (here regular will do pencil lead).

By the way, for safety reasons it is very important not to work under high voltage! The maximum indicator in this regard is 40-50 Volts. But it is better to start with small powers from 3 to 5 kW, gradually increasing them.

There is also a “water” way to create a thermocouple. It consists in ensuring the heating of the connected wires of the future structure by an arc discharge that appears between them and a strong solution of water and salt.

During this interaction, “water” vapors bind the materials together, after which the thermocouple can be considered ready. In this case, it matters what diameter the product harness is.

It shouldn't be too big.

Free electricity with your own hands (video)

Getting free electricity is not as difficult as it seems. Thanks to various types of generators working with different sources, it’s no longer scary to be left without light during a power outage. A little skill and you already have your own mini-station for generating electricity.

Source: http://6watt.ru/elektrosnabzhenie/besplatnoe-elektrichestvo

Peltier module: technical characteristics

The thermal converter (Peltier module) operates on the reverse principle of the thermocouple - the appearance of a temperature difference when electric current flows.

How does the Peltier element work?

It is quite simple to use a Peltier module, the principle of which is to release or absorb heat at the moment of contact between different materials when current passes through it. The energy flux density of electrons before and after contact is different.

If it is less at the outlet, it means heat is generated there. When electrons in contact are inhibited by an electric field, they transfer kinetic energy to the crystal lattice, heating it up. If they accelerate, heat is absorbed.

This occurs due to the fact that part of the energy is taken from the crystal lattice and it cools.

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

The Peltier module, the application of which is the topic of our review, is used in the creation of thermoelectric cooling devices (TECs). The simplest of them consists of two p- and n-type semiconductors connected in series through copper contacts.

If electrons move from a semiconductor “p” to “n”, at the first metal bridge junction they recombine, releasing energy.

The next transition from the semiconductor “p” to the copper conductor is accompanied by the “pulling” of electrons through the contact by an electric field.

This process leads to energy absorption and cooling of the area around the contact. Processes occur in a similar way at the following transitions.

By placing heated and cooled contacts in different parallel planes, a practical implementation of the method will be obtained. Semiconductors are made from selenium, bismuth, antimony or tellurium. The Peltier module houses a large number of thermocouples placed between aluminum nitride or aluminum oxide ceramic plates.

Factors influencing the efficiency of TEM

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

Larger values have not yet been achieved due to low efficiency (5-8%) and high cost. For a TEM to work successfully, it is necessary to ensure effective heat removal from the heated side.

This creates difficulties in the practical implementation of the method. If the polarity is reversed, the cold and hot sides reverse each other.

Advantages and disadvantages of modules

The need for TEMs arose with the advent of electronic devices requiring miniature cooling systems. The advantages of the modules are as follows:

compactness;
no moving joints;
the Peltier module has a reversible operating principle when changing polarity;
simplicity cascade connections to increase power.

The main disadvantage of the module is low efficiency. This manifests itself in high power consumption to achieve the required cooling effect. In addition, it has a high cost.

Application of TEM

The Peltier module is used primarily for cooling microcircuits and small parts. A start was made for cooling elements of military equipment:

microcircuits;
infrared detectors;
laser elements;
crystal oscillators.

The Peltier thermoelectric module gradually began to be used in household appliances: to create refrigerators, air conditioners, generators, and 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 generation. Together with them, cooling systems are developing using innovative technologies, with modern means control.

The Peltier module has found application in this area primarily in cooling microcircuits and other radio components. Traditional coolers can no longer cope with forced overclocking modes of microprocessors.

And increasing the frequency of processors makes it possible to increase their performance.

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

Heat is usually removed from processors by coolers. The air flow can be sucked in from outside or come from inside the system unit. the problem is that the air temperature is sometimes insufficient for heat removal.

Therefore, TEM began to be used to cool the air flow entering the system unit, thereby increasing the efficiency of heat transfer.

Thus, the built-in air conditioner is an assistant to the traditional computer cooling system.

Aluminum radiators are attached to both sides of the module. From the cold plate side, cooling air is pumped into the processor. After it takes the heat, another fan blows it out through the module's hot plate heatsink.

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

Activating processor cooling also creates some problems.

Simple Peltier cooling modules are designed for continuous operation. Lower power consumption also reduces heat dissipation, which can cause the chip to overcool and subsequently freeze the processor.
If the operation of the cooler and refrigerator are not properly coordinated, the latter may switch to heating mode instead of cooling. The additional heat source will cause the processor to overheat.

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

Do-it-yourself car refrigerator

In the middle of the last century, the domestic industry tried to master the production of small-sized refrigerators based on the Peltier effect. Existing technologies of that time did not allow this to be done. Nowadays the limiting factor is mainly high price, but attempts continue, and success has already been achieved.

Widespread production of thermoelectric devices allows you to create a small refrigerator with your own hands, convenient for use in cars. Its basis is a “sandwich”, which is made as follows.

A layer of heat-conducting paste type KPT-8 is applied to the upper radiator and the Peltier module is glued to one side of the ceramic surface.
Similarly, another radiator is attached to it from the bottom side, intended for placement in the refrigerator chamber.
The entire device is tightly compressed and dried for 4-5 hours.
Coolers are installed on both radiators: the upper one will remove heat, and the lower one will equalize the temperature in the refrigerator chamber.

The refrigerator body is made with a heat-insulating gasket inside. It is important that it closes tightly. You can use a regular plastic tool box for this.

12V power is supplied from the vehicle system. It can also be made from a 220 V AC network, with a power supply. The simplest AC to DC conversion circuit is used.

It contains a rectifier bridge and a ripple-smoothing capacitor. It is important that at the output they do not exceed 5% of the nominal value, otherwise the efficiency of the device is reduced. The module has two outputs made of colored wires.

“Plus” is always connected to red, and “minus” to black.

The power of the TEM must correspond to the volume of the box. The first 3 digits of the marking indicate the number of pairs of semiconductor microelements inside the module (49-127 or 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 onto the radiators.

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

Peltier module: electrical energy generator

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

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

2 Peltier modules TEC1-12705 with plate size 40x40 mm;
converter EK-1674;
aluminum plates 3 mm thick;
water pan;
heat resistant glue.

Two modules are placed between the plates with glue, and then the entire structure is fixed to the bottom of the pan. If you fill it with water and put it on fire, you get the required temperature difference, which produces an EMF of the order of 1.5 V. By connecting the modules to a boost converter, you can increase the voltage to 5 V, which is necessary to charge the phone 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 the water different ways: make it flow-through, replace it with fresh one more often, etc.

An effective means of increasing the temperature difference is the cascade switching of modules, when they are layered one on top of the other.

Increasing the overall dimensions of the device allows you to place more elements between the plates and thereby increase the overall power.

The generator's performance will be sufficient to charge small batteries, operate LED lamps or radio. Note! To create thermal generators, you will need modules capable of operating at 300-400 0C! The rest are only suitable for trial testing.

Unlike other means alternative receipt Electricity they can work while driving if you create something like a catalytic heater.

Domestic Peltier modules

TEMs of their own production appeared on our market not so long ago. They are highly reliable and have good characteristics. The Peltier module, which is in wide demand, has dimensions of 40x40 mm. It is designed for a maximum current of 6 A and voltage up to 15 V.

A domestic Peltier module can be purchased for a low price. With a power consumption of 85 W, it creates a temperature difference of 60 0C. Together with the cooler, it is capable of protecting the processor from overheating with a power dissipation of 40 W.

Characteristics of modules from leading companies

Foreign devices are presented on the market in greater variety. To protect processors from leading companies, a PAX56B Peltier module is used as a refrigerator, the price of which, complete with a fan, is $35.

With dimensions of 30x30 mm, it maintains the processor temperature no higher than 63 0C with a power output of 25 W. For power supply, a voltage of 5 V is sufficient, and the current does not exceed 1.5 A.

The PA6EXB Peltier module is well suited for cooling the processor, providing normal temperature conditions with a dissipation power of 40 W. 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 (including the fan) - the device requires free space around it. Its price is $65.

When the Peltier module is used, specifications it must meet the needs of the cooled devices. It is unacceptable that their temperature is too low. This can lead to moisture condensation, which can be harmful to electronics.

Modules for the manufacture of generators, such as TEC1-12706, TEC1-12709, are distinguished by higher power - 72 W and 108 W, respectively. They are distinguished by markings, which are always applied to the hot side.

The maximum permissible temperature of the hot side is 150-160 0C. The greater the temperature difference between the plates, the higher the output voltage.

The device operates at a maximum temperature difference of 600 0C.

You can buy a Peltier module inexpensively - about $10 or less per piece, if you look hard enough. Quite often, sellers significantly inflate their prices, but you can find them several times cheaper if you buy them on sale.

Conclusion

The Peltier effect has now found application in the creation of small refrigerators necessary modern technology. The reversibility of the process makes it possible to produce micropower stations that are in demand for charging batteries of electronic devices.

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

31.03.2020

Computer

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