EUREKA!

YAY! I'm finally on the blog! And more I think that after drinking way to much coffee today and doing way to much math that I can do this project! Basically given a pipe 4" wide and 13' or so long attached to a 1,000 sq. ft roof it could be possible be able to generate 40-50 Watts of energy per hour during average rainfall. I have copious notes if anyone is interested in seeing the math but the basic numbers would be

360 cubic feet of water on the roof given .03 inches of rain in an hour (not unreasonable I found a website with hourly updates that seemed to be a good average).

37.7 cubic feet in the pipe.

360/37.7 gives the flow. This is cubic feet per minute; for this equation it is 9.5 cubic feet a minute in this instance.

The formula for calculating Horsepower with Hydroelectric Dams is given as:

Hp = 64.2 x F x H
------------------
33,000

Hp= Horsepower (176 Watts)
F= Flow (9.5 in this case)
H = Height (in this case 6')
33,000 is some number related to Horsepower that I couldn't explain here, suffice to say it is a constant.

So
64.2 x 9.5 x 6
--------------
33,0000

would end up equaling .1 Hp or a little less than 20 Watts. Except that I plan on using to turbines (hence the 13' long pipe 6' drop and a little extra for the turbines) so it would be hopefully 40 Watts. With two turbines and a hopefully steady flow of rain a six hour average rain storm could hopefully yield 200 Watts!

If anyone wants to see more math (I hope this wasn't too much for this post) or has any ideas about storage let me know!