Peltier cell: all about this element

peltier cell

You probably need refrigerate something in your DIY projects. For this, you would need a Peltier cell. This semiconductor device based on thermoelectric effects allows very fast cooling. You can buy it in some stores like Amazon, or simply remove it from a damaged device where it is. The appliances that you can get one of are the typical cold water dispensers and some dehumidifiers without a compressor.

This type of Peltier cells are widely used in different sectors of the industry for refrigeration. The reason is that it has many advantages over other traditional cooling systems. For example, in the two examples I have given above, in the case of the water dispenser it is dedicated to cooling the water tank so that it stays fresh, while in the dehumidifier it cools the incoming air so that moisture condenses and drips in the condensation tank ...

Thermoelectric effects

The thermoelectric effects are those that convert a temperature difference into electrical voltage or vice versa. This is achieved using thermocouples or very specific types of materials, usually semiconductors. In these, the temperature gradients produce charge carriers in the material, either electrons (-) or holes (+).

This effect can be used to multitude of applications, from heating, cooling, measuring temperatures, generating electricity, etc. And that is due to the various effects that exist within the so-called thermoelectric ones. Some of them are:

  • Seebek effect: observed by Thomas Seebek, it is a phenomenon in which thermocouples to which a temperature difference is applied produce electricity. It was discovered when it was observed that two metals joined by one of their ends a temperature difference was applied to it and that they generated a potential difference at their separated ends. With this, it could be possible to use the heat generated by some source to transform it into electricity.
  • Thomson effect: describes the heating or cooling of a current-carrying conductor with a temperature gradient. It was described by Williams Thomson or Lord Kelvin.

Generally, the Seebek, Thomson, and Peltier effects can be reversible, although this is not the case in the case of Joule heating.

Peltier effect

Peltier effect

El Peltier effect it's similar, and it's what the cells we discuss in this article are based on. With this property discovered by Jean Peltier in 1834, and similar to the Seebek. It happens when an electrical voltage causes a temperature difference between two different materials or thermocouples. In the case of current devices they are semiconductors, but they can also be metals known as Peltier junctions.

That means that if an electrical charge is applied to these devices, one side will get hot and the other side will cool. This is because electrons travel from a high-density region to a low-density region, expand in the same way that an ideal gas does, and therefore cool that region.

By the way, a single stage TEC can generate a temperature difference between its parts up to 70ºC. So if you keep the hot part cooled, the more cooling capacity this TEC or Peltier cell will have. This absorbed heat will be proportional to the current provided and time.

Advantages and disadvantages of TEC

Like any system, the TEC or Peltier cell has its advantages and disadvantages. This is why some refrigeration systems still prefer to use other conventional methods. Between the benefits are:

  • It has no moving parts, so it requires no maintenance and is more reliable.
  • Does not use compressors no polluting CFC gas.
  • It can control temperature easily and very precisely, up to fractions of a degree by varying the applied current.
  • Small size, although they can be manufactured with different sizes.
  • It has a long life of up to 100.000 hours, compared to what some mechanical refrigerators provide.

Companies that Disadvantages of using a TEC are:

  • You can only dissipate a limited amount heat flow.
  • Not efficient energetically speaking compared to gas compression systems. However, new advances make it increasingly efficient.

Properties

A Peltier plate such as TEC1 12706 It can be priced at a couple of euros, so it is very cheap. This board has dimensions of 40x40x3mm and contains 127 semiconductor pairs inside. The electrical power is 60w and its nominal supply voltage of 12v and nominal current of 5A.

With her you can generate maximum temperature differences between their faces of 65ºC, which is pretty good. It can work between -55ºC and 83ºC without damaging itself, so if you move outside these values ​​you run the risk of being unusable. If you keep the values ​​within that, it can even last you 200.000 hours of work perfectly, that is, many years ...

The efficiency of this model is about 12-15w heat extracted, that is an efficiency around 20 or 25% considering that it consumes about 60w. Anyway, you have to bear in mind that this value will also be greatly influenced by the ambient temperature.

If you prefer, instead of buying only the TEC or Peltier cell, you can also purchase at Amazon the complete cooling system.

Peltier cell application

Refrigerator with Peltier

Well, a Peltier cell can be used primarily for cooling. For example, you could cool water or any other liquid with it, or create your own homemade dehumidifier. Whatever it is, its set-up is very simple. Once you acquire or get the cell, you will only have to apply direct current through the positive and negative cables that it has. That way one side will get hot and the other side will get cold. You must identify its sides well according to what you are looking for.

Application example with Arduino

You can use a connection scheme like the one we made for him relay module, but instead of feeding the Peltier cell and the fan with 220v AC, it is fed with DC at 12v. You can use that same schematic and connect your cooler to the Arduino board.

Once you have everything connected, you can create a simple code for Arduino IDE so that your refrigeration system can be controlled, such as this one to control the relay under what conditions so that the system can be activated (you can use additional humidity, temperature, etc. sensors):

const int pin = 9; //Debe ser el pin conectado al relé para su control

const float thresholdLOW = 20.0;
const float thresholdHIGH= 30.0;

bool state = 0; //Celda Peltier desactivada o desactivada

float GetTemperature()
{
return 20.0; //sustituir en función del sensor de temperatura (o lo que sea) empleado
}

void setup() {
pinMode(pin, OUTPUT); //el pin de control se define como salida
}

void loop(){
float currentTemperature = GetTemperature();

if(state == 0 && currentTemperature > thresholdHIGH)
{
state = 1;
digitalWrite(pin, HIGH); //Se enciende el TEC
}
if(state == 1 && currentTemperature < thresholdLOW)
{
state == 0;
digitalWrite(pin, LOW); //Se apaga el TEC
}

delay(5000); //Espera 5 segundos entre las mediciones de temperatura en este caso
}


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