first off, you need to understand the limitations you face.
for most folks, that limitation is the pipeline.
if the pipeline is the limitation, then the maximum hydro power is located at the 2/3rds static pressure. measure the static pressure, and design the turbine for 2/3rds that pressure, spend some time with the half dozen online pipe flow calculators to find the water flow at that pressure loss.
if the water quantity is the limitation then you have to choose how much the power is worth, to make a reasonable investment in the pipe.
My friend in oregon was looking at 1100 feet of pipeline for 67 psi of static pressure, at up to 6 cubic feet a second. 6 inch pvc pipe wasn't in the uh, 'pipeline' so to speak, and the system hasn't been built yet.
anyhow,
i recommend turgo wheels over pelton wheels. anything less than 40 psi and i would look into designing a kaplan turbine, via lost wax casting after prototypes built with via 3-d printers out of plastic, to find the optimum size for maximum efficiency.
design the generator last, its the easiest thing to build. but only build the generator after measuring the available power via a pony brake or some other arrangement.
i would throw out the idea of trying to design the turbine around a fixed rpm of say, 1850 or 3700 rpm and attempting to convert an induction motor to generator.
it is simply not worth the lost in power. but for some its lightning proof and that's what matters.
