Thermoelectric power generation is a growing and exciting green technology that has in the past 5 years become increasing researched and implemented as a practical complimenting technology for generating additional power in off grid applications as well as remote locations. The basic concept of the technology is to use waste heat or generated heat and scavenge a portion of that heat thru the TEG modules and cool or a better term remove the heat from the cold side so that heat continues to flow. The cold side and hot side need to have a large differential in order for flow (heat flux) to occur. The larger the DT (difference of Temperature) the greater the heat flow and therefore the more power is produced!
Straight forward up to now! The predominant issue is in any design is how to introduce the heat and more importantly how to dissipate the heat as fast as it transfers thru to the cold side. The easiest way a flat hot plate and a heat sink. But there inlays the problem. This simple design only achieves a modest return on power. Only enough to run a small low voltage fan with very little extra power generated for a small device.
The next design is to use a fan on the cold side to induce forced convection which will increase the heat removal side significantly. To do this you now require a larger TEG system with more modules? Higher heat value? All of the above! Now you need extra power above your usable power to run the fan. This typically requires a number of thermoelectric modules in series to generate the required voltage 12VDC for a typical fan. Four modules in series (TEG1-12610-5.1) with a meaningful DT will generate an open circuit voltage of between 20 and 26 Volts on average. When a load is applied that voltage will be halved to about 10 to 13VDC. Enough to run the fan at rated voltage.
Not enough to do anything else? ie. Charge a 12VDC battery. To do this you need another bank of at least 4 (TEG1-12610-5.1) modules. Together, they can produce about 15 to 25 watts, again depending on DT. This system can be optimized by setting the TEG system up with a cold air intake from outside or thru the subfloor to the crawl space below the house or cabin or having a direct thermal path to the fire, but this would involve compromising the stove wall to illuminate the resistance the steel plate creates.
Again, in conclusion the colder the ambient air is running over the sinks the greater the power produced. The hotter the heat source and least resistance of heat flow the greater the power output.
We will discuss in our next blog “The difference between liquid and air cooling!”