I was a licensed Boiler Tech until a short time ago. I hope my thoughts on this subject are helpful…
The major advantages of a steam engine are threefold:
2. External combustion
1. Torque – most generators out there use four-cycle engines. Google four or Otto cycle engines for an explanation. The piston cycles are – intake, compression, POWER and exhaust. Long story short, only 1 out of 4 downward strokes is a power stroke. On a simple, double acting steam piston (mill engine) there is a power stroke in BOTH directions. So what you get compared to the diesel is power, power, power, power, power, power, power, power. Each up AND down stroke is powered. Eight power strokes vs. one. A steam engine thus generates MUCH more torque. If you gear it up to run a bank of alternators or generators, you would have no trouble achieving any particular RPM because the torque available is about 16 times greater.
2. External combustion – A boiler is needed. You can burn anything in the boiler to produce the steam. This means you can run your boiler at the best efficiency to generate the steam needed. On anything that burns. Coal, wood, old clothes, crank case oil, you name it. Chemically treat the water, and you get no calcium buildup in the tubes.
Simplicity – Once you get your boiler and engine dialed in, it’s a simple question of running it.