Rainfall Driven Micro Hydro-Generating System

[cutegaljessy]

Homework Statement

Im trying to design a Rainfall Driven Micro Hydro-Generating System
Under normal operation, the generating system is expected to produce 30 W at 12 V regulated DC.
Is there any relation between the length of the water pipe, the speed of rotation of the turbine and the generated voltage?
and how to measure the flow? (Im using rainfall here)

Homework Equations

the Power generated is equal to Head x flow x g x efficiency of the turbine

The Attempt at a Solution

I'm using a pelton turbine, I found how the power generated is calculated

 

[NewtonianAlch]

Not entirely sure what this thing is meant to look like, but I presume the length would matter as that's a distance, so with a greater distance you may lose power as it takes time for water to travel a longer distance, possible loss of momentum.

Alternatively, a longer pipe might mean increased momentum if it was vertically pointed, or on some kind of incline; depends on orientation.