You can't extract much energy from low-grade heat. Maximum efficiency = (T2-T1)/T1, where T2 is the temperature of the low-grade heat (exhaust from the computer system), and T1 is the ambient temperature of where you dump the heat. All temps are absolute (K). Typical chip surface temps are 60-80C, and 70C is about 343K. If your cold end is a cool day (say 15C), then T1 is 288K. The maximum energy you can recover from that heat is 19% of the input. That's a theoretical upper limit. Actual heat engines don't do that well.
It is even worse than the above calculation. The maximum energy that can be extracted between temperatures Thot and Tcold is (Thot - Tcold)/ Thot. The above equation should be (T2-T1)/T2 rather than (T2-T1)/T1.
For the above example of 70C and 15C the maximum possible efficiency is 16% rather than 19%. In reality the efficiency is likely to be between 5 and 10%.
Trying to extract any power from a small temperature difference is very inefficient. Large power stations get better efficiency because the difference between high and low temperatures is around 500C, not 50C. Power stations need the biggest possible temperature difference - that's why they need cooling water or cooling towers.
In summary part of the confusion in this thread seems to be because there are 2 very different ways proposed in this thread, and on the 3xergy site, to use the heat.
1) Simple use the heat as heat. This is efficient. Simply use the heat from a miner to heat a room or heat water. This seems to 'first generation' proposed at the
www.3xergy.com site and appears to be nothing more than using a miner's excess heating to do space (or water) heating. There is nothing new or unusual with this proposal.
2) The second way to use the heat is to use the small temperature difference between the miner and a cool point to extract power, for example to generate electricity or to power refrigeration. As shown above this is very inefficient with small temperature differences. Extracting power from the heat (temperature difference) and distributing excess heat via the electrical grid, as proposed on the
www.3xergy.com site, is extremely unlikely to be cost effective. I won't call it a scam but it may be wishful thinking. It can be done but is rarely worth the effort. If you want more information see Carnot's principle or the second law of thermodynamics.