Thermoelectric generator

The production of electricity by conversion of heat differences to electric current.

The principle of Peltier cells, which are widely used for cooling, finds application as a thermoelectric generator. Just make different temperatures on the two surfaces of the article and the article generates a dc current.

A little historical excursion:

Between the years 1821 to 1823 Thomas Johann Seebeck came on the method of direct conversion of temperature differences to electric voltage. The series involved two different electrically conductive materials generate electricity, if there is a material exposed to heat and the second cooling. Since the described thermoelectric phenomenon bears the name of its discoverer, Seebeckův phenomenon.

1834 came, Jean C.And. Peltier on the way to make use of the same phenomenon for cooling/ heating. Peltier effect is the opposite of Seebeckova phenomenon when the electric current supplied to the Peltier cells on the one hand, article cool and the other warm. This phenomenon is today mainly used for cooling electronics, portable refrigerators and smaller cooling devices.

TEG from the English ThermoElectric Generator, or thermoelectric generator is a device for the direct conversion of thermal energy (temperature difference) into electrical energy. In today's concept of the semiconductor component, consisting of two ceramic plates, between which are applied two metals. 

The most commonly used materials: a bismuth (Bi2Te3), a lead (PbTe) and Germanium silicon (SiGe). If one side of the parts to cool them, and the other is heated, there is a direct current to the output. The higher the difference between the hot and cold side, the greater the voltage and current.

Today, with the generator in the home we will meet in the fireplace fans that distribute heat from the stove into the room and use the high temperature of the top plate of the stove or flue pipe compared to the relatively low temperature of the surrounding air. 

In general, the generator finds application wherever there are surpluses of waste heat, which is not possible to use other methods. The reasons for the small number of applications is more. Both the low efficiency reported from 5 to 10 percent, also the high price of the articles.

Interesting is the comparison with the performance of the playing area compared to PV, where TEG articles take up 6 to 7 times smaller area compared to the area of photovoltaic panels.

Here is available: sample datasheet TEG article

Some of the projects they propose to extract the excess heat from the exhausts of internal combustion engine, or need to utilize the waste heat of the hot-air pipes. Interesting it shows the possibility of heating the concentrated solar energy výhřevnou surface of the article – use lenses, or increase the area of the impact of solar radiation, or the use of the solar collector. At the same time, it is necessary to ensure sufficient heat dissipation from the other side, or directly cooling. An interesting idea is Water-cooled, sun reheated generator.

Pros
  • no moving parts
  • small size
  • maintenance-free device
Risks
  • low efficiency
  • the higher purchase price of articles
  • solve the questions of how to ensure a sufficient difference between the hot and cold side of the article
Conclusion:

In techonologii with lots of potential. One day, when articles far more powerful and cheaper overall, there will be a space for diverse technical solutions, and not only in industry, but also for home experiments. Maybe we will see the need of solar power plants, which will be much smaller, and therefore more powerful in a built-up area. 

So far, we can play with iow-powered articles and try to get maximum performance and find new application.

Sources:

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