I am having a tough time connecting my engine to my generator, mostly because of how it is sitting, and in trying to get dual power sources for it.
Option A: If I go with mechanical belt linkage, the only way I can get it to work is to mate a 4 inch pulley on the engine, and a 16 inch pulley on the generator, and at 19 inches of shaft centers, get 2100 rpm out of the engine. With its narrow powerband, that only gives me 32 HP at that rpm, but enough to pull the full 20 KW out of the generator. Even then I would have to twist the belts to get the right rotation.
Option B: I could go with a hydraulic set up, and with that I would have no physical limitations, and got most of the parts, but it leaves me with buying a $900 hydraulic pump. Add in various fittings, and I am at the same cost as a buying a second generator head. I also have no idea if I would have to add a hydraulic cooler because that is a boatload of oil being pushed around at 2000 psi.
Option C: If I buy a new generator head, I can shaft-drive the generator, but I am tapped out at 1800 rpm. With my narrow powerband on my engine, that knocks me down to a 16 KW generator head. The cost would be $1500, probably comparable with option C, but does give me redundant back-up power of both engine and generator. I could also get both flopping, synchronize them, and put out 36 KW/183 amps if I needed more power then 16 or 20 KW.
But maybe there is some other options I have not thought of yet.