I would be incredibly interested if something like the kryton beast eventuated and featured active cooling or an integrated TEC
now that would be decent
I suspect that there is no TEC efficent enough ..... and it's just a problem of physic laws .....
I mean, a TEC does not produce "cold", it just transfer the heat from the "cold" to the "hot" side, also generating heat in the process itself ..... then you need to take away the heat from the "hot" surface (if you don't do it, the TEC plate, after a certain time, start to heat both the surfaces, and can reach a temperature high enough for burn the junctions or desolder them, destroying itself.
Also, there's a limit to the quantity of heat tha the TEC plate can transfer (is usually indicated as "power", in Watt) ..... this mean, as example, that a TEC rated for 50W, can efficently transfer a maximum thermal power of 50W, not more.
Now, just wondering ..... if you find a TEC small enough for be used in a handheld host, it will be, probably, a 6x6mm, or a 8x8mm ..... and can probably work around 1V at 2A, and transfer 1W or few more ..... plus, ofcourse, the 2W of heat generated from the plate for transfer the 1W of heat from the "cold" to the "hot" face (this, BTW, mean that for transfer 1W of heat from the device to the heat dissipator, it have to dissipate to the ambient 3W of heat
) ..... also, the maximum difference temperature is fixed, and is around, for good working conditions, like 70C ..... this mean that the temperature that you can reach on the "cold" face, depend mainly abut how much "cold" you can keep the "hot" face ..... like, if you can keep the "hot" face at 70C, theorically you can reach 0C on the "cold" face ..... but this only theorically ..... you must also keep in consideration the dispersion between the junctions, the dispersion of the parts in air, thermal resistance of the parts connected, mutual thermal resistance from cold part > air > hot part, and so on ..... in short, you may be lucky if you can have a difference of 50C.
So, keeping the "cold" face around 30C, you need to have the "hot" face (and the heat dispersion system) at 80C or less, and continuously draw away the heat ..... also, considerate now if your diode developes 1,2W of heat ..... if your TEC can transfer only 1W, the remaining 0,2W does not become transferred, overloading the system and quickly rising the diode holder temperature (remember that, with the TEC system, the "cold" part of the assembly is NOT exposed to air, nor heatsinked from the ambient, so also this small 0,2W can quickly rise the temperature, til the diode burns).
Those are just examples, but can give you an idea .....
EDIT: i just remembered, i read some times ago about a company called Micropelt GMBH, that was announcing new generation of thin-film TEC coolers ..... maybe these new technologies can be more efficents and valid, for this specific use ..... but, being new technologies, i don't dare to just imagine how much can cost one of them
EDIT2: just found again
their site, and there's something new, respect the time i seen it for the first time .....
thermogenerators ..... does come something in mind ? ..... a TEC thermogenerator, specifically designed for generate current from heat, with a black adsorbing face ..... who said LPM ?