I mean then we could take these big beasts that put out like over 100W of heat and convert some of that back into power...
This is the closest I can think of, a bit gimmicky and not a major power regenerator:http://www.reghardware.co.uk/2008/02/29 ... g_cooling/
You could use a peltier or phase change system to draw heat out of the system and dump it into water for household use. Don't think anyone has done this but it sounds very complex.
Powering a peltier would add significantly to the electric load used by the system, wouldn't help more efficient use of the waste heat.
One could use a peltier as an electric generator (see for instance
), but the thermal resistance of the peltier device would tend to make cooling less efficient, and you would need to make sure that it had a reasonable temperature difference across the device.
Would it generate enough energy to pay for itself, to make up for the energy involved in making, shipping, marketing, disposing of the peltier element?
Rather like the SPCR approach to noise - better to try to make it produce less noise to start with than to try to handle noise once produced. Likewise better to try to use less energy to start with.
For one thing - much of the energy is lost upstream from the "consumer" - generation losses, transmission losses, etc.
Using the heat directly (for climate control, etc.) might be a better bet.
There are lots of generators of waste heat - unless dealing with server farms, the heat generated by one personal computer is unlikely to be a significant part of your energy budget. (i.e. better payback by focus on efficiency and recovery in other areas - insulation, better control, more efficient climate control, transportation, etc.)