I'm not sure really how to answer this.
A Stirling engine produces mechanical power from a heat difference.
Does he mean using a Stirling type cooler?
Using the term "energy created" shows something about background.
Well, I will mention that there is another thread, that describes a Stirling PC computer CPU cooling fan. This is a clever little device and would be interesting to read. I think that is the closest answer I can give.
And of course, I don't stop there!
The concept of heat just throws so many people.
I happen to have a nice gaming PC system.
It is very very fast, and generates a lot of heat.
It has a kilowatt power supply.
The energy to run the cooling fans is the least of my energy worries.
It has seven cooling fans, with blue LEDs on them.
This is NOT including the system CPU fan and video card cpu fan.
The computer would still overheat.
Solution:
take the pretty glass side cover off.
buy a $10 all stainless 7 inch table top fan.
point fan into side of computer.
TAH - DAH !
It is amazingly that simple.
Also works to cool all my cable modem, router, switches, etc.
People can not believe it can be that easy.
So, how much would a Stirling engine cost that would run on waste heat of a PC that could really make a difference ?
You do not even want to know!!!!
This is not to say a Stirling cooler might not show up in a high end gaming system, but such a device would plug into the wall. It would be used to extreme chill the fluid { yes fluid } in the fluid based PC cooling system. For those of you not that into gaming systems, this is not that far fetched.