hydraulic fan motors...wtf?

It may be more efficient, I don't know. What it is "NOT" is "free HP." It takes real power to move water and air. Alternators are not very efficient really I think the older ones barely cracked 50 - 60% which is way below some electric motors. Of course if you produce power off a belt,and lose power in that conversion, you lose even MORE power when you convert back to mechanical force........with a motor. I'd bet the overall conversion for an electric fan is only about 40%

I have no idea what a hydraulic pump runs in that regard. Since it must produce enough to run "in bypass" it can't be very high.

Kinda makes ya wonder why they don't just .....................BELT DRIVE the thing (fan)?