Peltier module (TEC)
The Peltier module (thermo- electric cooler) operates based on the Peltier effect. The outer layer is made up of ceramics. Inside the ceramics lies a series of two types of semiconductors on two sides.
Peltier effect states that when you apply a certain voltage to two different conducting materials joined together, one of the junction heats up and the other junction cools down.
You can see the Cu-Fe thermocouple in the figure. Current flows from Cu to Fe, at junction 1. Here heat is absorbed. Thus, this junction becomes hot.
Similarly, current flows from Fe to Cu, at junction 2. Hear heat is released. Thus, this becomes cold.
If you reverse the direction of voltage, then junction 1 becomes cold and vice versa. This implies that it is a reversible process.
Pros of Peltier module
- It does not have any moving parts. So, it is noise-free and environment friendly.
- Peltier module is small and light in weight. So, you can easily adjust it in any electronic equipment.
- It is exceptionally reliable in quality and performance. Thus it helps to deliver a precise temperature.
- The solid-state of the Peltier module makes it very durable. So it has got a very long life expectancy of more than 5 years in normal condition.
Cons of Peltier module
- It can not provide a temperature below 10°C. Besides, it will also not deliver very high temperature.
- You will not be able to use it in AC voltage. This is because Peltier modules operate at a low voltage (around 12 volts). Similarly, the alternating nature of the voltage causes the Peltier module to operate in opposite direction. The continuous variation in the heating and cooling action will cause the module to rupture quickly.
- The hot and cold sides are very close to each other. Thus, it causes difficulty in transferring heat energy from one side to another. So, due to this, an extra fan is needed for temperature control.
Applications of Peltier module
- Photonic and medical systems (such as a semi-auto biochemistry analyzer)
- CPU cooler and scientific instrument
- Temperature stabilizer which can act both as a cooler and an incubator
- In IR sensors, CCD sensors, gas analyzers, refrigerators, etc.
Different modules have got different specifications which you will know by looking at the datasheet for the module.
- Operating voltage:- This is the voltage that you can give to the module. The mostly used Peltier modules operate at 12 VDC. You can also use the module at a lower voltage than the operating voltage. But, you will not get the same peak temperature variation between the hot and the cold sides.
- Maximum voltage:- It is the voltage above the operating voltage that you can give to the module. Operating above the maximum voltage is strictly prohibited. Also, operating within the maximum voltage is not recommended. Else, it will reduce the life expectancy of the Peltier module. So, you should operate it within the range of operating voltage.
- Maximum current:- It is the maximum current that the Peltier module draws when operated at maximum voltage.
Before you replace or add the Peltier module to the system, you need to check it first. For this, supply around 5 VDC to the points of the Peltier. Then touch both sides. If you feel any temperature variation on both sides, then it is in proper condition.
You can find various thermo-electric coolers (TECs) in the market. The models of those Peltier are printed on their surfaces.
The nomenclature consist of mainly 5 parts
1. First two alphabets
The first two alphabets are TE which represents the thermo-electric nature of the Peltier module.
2. Third alphabet
The third alphabet after TE represents the size of the Peltier module.
- C = standard size ( 40 mm X 40 mm) such as TEC1- 12704
- S= small size (30 mm X 30 mm) such as TES1- 12704
3. Single-digit after the three alphabets
It represents the no. of layers or the stages present in that module.
- 1 = single layer such as TEC1– 12704
- 2= double-layer such as TEC2– 127-63-08
The more is the no. of stages, the more temperature variation can it provide.
4. First three digits after the dash symbol
It implies the no. of P-type and N-type doped semiconductor pair present in the module. For example, the TEC1-26316 Peltier module has 263 P-N pairs. Similarly, TEC1-12706 has 127 P-N pairs.
In the case of double stages such as TEC2 – 127- 63– 08, 127- 63 represents P-N pairs at two different stages.
The more is the no. of P-N pairs, the more temperature variation it can provide.
5. Last two digits after the dash symbol
It represents the maximum operating current of the module. For example, in the case of TEC1- 12706, the maximum operating current is 6 A. Similarly, for TEC1-12715 maximum current is 15 A.