wdyasq wrote
"Start with Ohm's law... V X A = W"
It is true that volts x amps gives watts (for DC systems) but that's not Ohm's law.
Ohm's law is the one about resistance : amps x ohms = volts. resistance = volts/amps
Best bet for the hydro turbine is to run it connected to a battery at teh correct voltage. The light bulb has probably stalled it right down to a very low speed. I wonder why people use bulbs and resistors to test machines that are designed for charging a battery.
As Flux points out the turbine will work best at about half of its runaway speed, so 24 volts is not far off the mark. However when you allow for losses, 12 volts may be closer. I suggest you try both. And also make any adjustments that the manufacturer suggests for tuning the turbine once connected.
have fun