You can select any type of motor. I'm going to spin it at a varying RPM and with a varying torque. The combination of torque and RPM will be capable of 50 hp intermittently. I can limit the maximum RPM but lower is better as I can leave out a gearbox. No different than what they probably use in a wind type generator. What all is required to covert this rotational energy @ 48 vdc with an electic motor?