This has been a very informative and helpful thread. It supports my own experience and expectations with alternators and heat. I had considered putting in additional air cooling
in to the engine
room but it looks like it will not necessarily help increase the alternator
output very much. Too much heat is not good in a closed space though for other reasons so I may do it for that.
Re any additional concern about increased fire danger
from more air from fans, it would be possible to wire up a shut down relay circuit to turn off the fans with a fire/heat detector in the engine
space. But not a smoke detector as I believe there are too many false alarms with those in engine spaces. I am sure there is a heat sensor of some sort available that would work for high temps above the usual in the space.
Re thermostats, while I am not diesel
expert I have been told that the purpose and function of engine thermostats is to allow engines to come up to normal engine temp quicker and that they have nothing to do with the regulation of engine heat after the engines get up to that range. I believe that they are closed when cold and open when the internal coolant
reaches their rated temp.