Originally Posted by
Philldpapill
TEGs generally use devices called "Peltier Junctions". Basically, they require a temperature differential(one side hot, while one side is cool) to produce electron drift. This electron drift creates a voltage and current if attached to a load. They are generally used in reverse, where a current is supplied, and the device CREATES a temperature differential.
However, PJ's are pretty expensive... And horribly inefficient when using them in the energy production side(<10% and usually on the order of about 4-5%). On top of that, they are expensive and bulky. Be prepared to pay at least $2/watt. Doing the math on that, an extra 100W is going to be at least $200, and that's just for the PJ's alone. 100W equates to about 8A, and that is assuming you already have a very hot surface to mount these to, and a fairly cool heat sinking material/system. Chances are, you're going to use about half the energy these things make(if not more) just on driving the cooling system. So, in reality, you're looking at about $4/Watt - best case scenario.
Even if you had an extra 200W(which is pretty cool...) from these TEGs, is it really worth the $400 investment and up-keep? IMO, the technology/Seebeck effect is pretty 'cool', but not practical in this sort of thing. You're better off just using the power off the alternator. Richard was going on and on about MORE CURRENT = MORE HHO, which is true, but there IS a point of diminishing returns... Even if you could produce 100lpm, there is point where more HHO injection doesn't result in much more MPG.
Regardless, these things are fun to play with and dream up ideas.