[francesco525]

Could you please give some references for your figures of 40% and 70% efficiencies. My last recollection for thermal power plant efficiencies (coal, oil, nuclear, etc.) was about 32 - 33%. Perhaps you are discussing some other parameter?

[Jotmo]

The most efficient, latest technology, super-wham-o-dyne combined cycle plants currently run around 60%, depending greatly on the weather and altitude of the plants.

I believe that the 70% mark was passed not long ago, but I do not believe any plants of that rating are in operation yet.

But much depends on the ambient conditions, and those kinds of numbers are only achievable under ideal conditions. So it's likely that real efficiency rating would be good deal lower under real world circumstances.