How Thermoelectric TEG Generators Work

The  concept of Thermoelectric Generators TEG’s (Seebeck Effect) is outlined below. We have been manufacturing TEG Power Generators for the last 14 years. Interest in the thermoelectric power generation field has exploded in the last three years. Thermoelectric modules work on two different principals:

1.Peltier Effect:
This effect introduces power to the module with a resultant cooling of one side and heating of the other. These types of modules are low amp (typically in the 6 amp range) and are designed for low temperature exposure of no more than 130°C to 140°C hot side. Higher temperature exposures will cause the module to either break apart or the soldered couples to break under stress and are not good power generators!

2. Seebeck Effect:
This effect creates a temperature differential across the module by heating one side of the module and cooling the opposite.
You cannot describe a Peltier module and say it produced power as many laymen do in their BLOGS. Think of it this way: a Seebeck Module is a power generator and a Peltier Module is a cooling module.
Thermoelectric Generators using the Seebeck Effect work on temperature differentials. The greater the differential (DT) or Delta Temperature, of the hot side compared to the cold side, the greater the amount of power (Watts) will be produced. Visit our Youtube channel for a great list of video’s on our products grctec1

Two critical factors dictate power output :
1. The amount of heat flux that can successfully move through the module (HEAT FLOW)
2. (DT) Delta Temperature – the temperature of the hot side less temperature of the cold side

Great effort must be placed on both the heat input design and especially the heat removal design (Cold Side). The better the TEG Generator construction is at moving heat from the hot side to the cold side and dissipating that heat once it arrives to the cold side cold side, the more power will be generated. Unlike solar PV, which use large surfaces to generate power, Thermoelectric Seebeck Effect modules are designed for very high power densities. On the order of 50 times greater than Solar PV !

Thermoelectric Seebeck Generators using liquid on the cold side perform significantly better than any other method of cooling and produce significantly more net additional power than a pump consumes (based on system size).
For any thermoelectric power generator (TEG), the voltage(V) generated by the TEG is directly proportional to the number of couples (N) and the temperature difference (Delta T) between the top and bottom sides of the TE generator and the Seebeck coefficients of the n and p- type materials.
For any thermoelectric power generator (TEG), the voltage(V) generated by the TEG is directly proportional to the number of couples (N) and the temperature difference (Delta T) between the top and bottom sides of the TE generator and the Seebeck coefficients of the n and p- type materials.
No other semiconductor material can perform as well as BiTe as far as efficiency is concerned at temperatures below 320°C.
Other material like PbTe are used but are far less efficient at lower temperatures, and must be used at significantly higher temperatures (in the 600°C hot side range) and are commercially available but very expensive!
Power output based on (DT) is very predictable and well documented for BiTe, but access to this information is difficult to find. With power generation, the thinner the length or thickness of the module, the greater the amp output or rating. To read more about how thermo electric technology works our (What’s news) page offers a large array of Thermoelectric  articles that are written to educate the enthusiast about TEG power.

You can have a 25 amp module the same size (typically 40 mm x 40 mm) as a 3 amp module, but length x width and height of the pellet or elements determines how much heat can pass through the module. The ratio of the height compared to the actual width x length determines the overall amperage of the module. As the height of the pellet is shortened, the ability of heat flux to pass more quickly through the module allows for greater power generation as long as (DT) can be maintained. That same 25 amp modules will produce over 8 times the amount of power as the 3 amp module. But 8 times the heat would need to pass thru that 25 amp module in order to produce that increase power. It is imperative that the (DT) be maintained. The module simply acts as a bridge. The larger the bridge area to length, the greater the flow of heat and resulting power output.

Our Low Temperature Modules (TEG2) are high amp modules with contacts that are soldered using SnSb solder on both sides. Although, the temperature of the solder has a 240°C melting point the solder begins to degrade at about 190-200°C . Therefore, we recommend the hot side stay below 190°C to allow for small temperature variations.
Our High Temperature Modules (TEG1) use flame spraying high temperature metal aluminum on the hot side and can withstand much higher temperatures in the range of 300° to 320°C hot side and have considerably larger tolerances when it comes to incidental  higher temperature over shouts. So much so, that you can expose the hot side to 340°C intermittently with very little module degradation. This technique is much more expensive to implement and therefore the cost is reflected in the price of the modules.
Temperature of the hot side is probably the most critical component when considering Thermoelectric Generators. (DT) needs to be in the 100 C range to get a viable power output from each module.
In cases where all you need is a milli watt of power, than temperature becomes less critical.

Want to see one working with outputs to show multimeter recordings from our unit click here https://www.youtube.com/watch?v=3-prKCGwV5M

An Example:
If you want to produce a 100 watt TEG thermoelectric generator and the TEG power output is based on a
DT of 100 C ( Hot side – Cold side)

Therefore:
You need at least  2000 watts of heat on the hot side given a 5% efficiency conversion to produce 100 watts of power.
To produce 100 watts of electrical power you are required to dissipate 1900 watts of heat on the cold side continuously as only 100 watts is being converted to power.

How critical is DT. The same 100 watt TEG above will produce:
200 watts:  If DT is increased to 150°C.
350 watts:  If DT is increased again to 200°C.
Power output in relation to Per Degree Celsius expansion between the hot and cold side is roughly 1°C = 2 to 2.5 watts of output.

******As long as the modules are designed for high temperature (TEG1).******
Therefore,
(DT) is the most critical criteria of power generation
Heat flux, or flow of heat through the TEG Modules (Seebeck Effect) is second