@5GHZ desire, TEC's have a maximum delta between the hot and cold sides of about 60-85 degrees celsius, so if you ran a TEC with the hotside at 125*c, your cold side would be at approximately 40-65degrees celsius, and that is with 0watt heat load, so that is effectively cooking your CPU or heating up your water in a chiller.
Now it is true that TEC's are more efficient with the hotside at higher temps, but it is pointless if your cold side isn't colder than ambient temperature, which is what we want for this application. For instance at 50*c hotside temp, you may get a greater delta between hot and cold side and your Qmax will also increase compared to if your hotside was at 27*c, for instance your dt may increase from 74*c to 83*c and your Qmax may increase from 122w to 134w Qmax such as this TEC http://www.thermonamic.com/TEHC1-12712S-English.pdf
However that increase in efficiency isn't enough to overcome the fact that your hotside is 23*c hotter, which means your cold side is 23*c hotter and your Dt only increased by 9*c so it can't overcome the deficit even though it is operating in a more efficient zone.
So even though TEC's are more efficient with a higher hot side temp, they are less effective for our application as the idea is to get the cold side to a sub ambient or even sub zero temperature. So the order of the day for us is to get that hotside as cold as possible, with the methods of cooling being liquid or air, that means we try to keep the hotside as close as possible to ambient temperature, which is as cold as we can get it with the hot side cooling methods we are using, that allows your delta between hot and cold side of the TEC to get the cold side as cool as we can possibly get it which is what we want to get our CPU's nice and chilly Edited by LiamG6 - 10/9/15 at 1:58am