For some cool (and usefull) watermills, check out Better then Wolves. Theres even an addon to use it with IC2.
I do realize however that they are a tech from a past era, IC needs a moddern version. One thing that comes to mind are turbines from hydroeletric powerplants.
Simpler and cheaper, still 1 heat
Just cheaper if you don`t count babbysit time. You forgot to mention that it is at least a Mark II capable of running only 1 cycle before cooling, it also might melt the coolants making it a Mark III and possibly blowing up his mine and his machines if left unnatended. But I won`t test that far, as you should have done instead of just trying to beat my design without putting any effort or thought in it.