- foot propeller in 5 feet/s water flow can generate about 4.8kwhr per day.
- 8kwhr per day looks to be more than you need. No more diesel generator!
The energy in a Dam is based on height (P.E.), where here we are getting the energy from the water based on velocity or K.E.
The energy in the water is calculated by:
K.E. = ½ m v^2 K.E. the joules per sec = watts
v = water velocity in m/s= 5ft/s * 12in/ft * 0.0254m/in = 1.524m/s
m = (kg) mass of water in 1 sec = vol * density of water
= pi*(18in*.0254m/in)^2 * 1.524m * 1000kg/m^3 = 1002kg
watts = ½ * 1002 * 1.524^2 = 1163.6 watts or 28kwhr per day.
Interesting link about propellers:
http://mystic.math.neu.edu/gorban/Gorlov2001.pdf
With that in mind. The best propeller is 35% eff, typical propeller is 20% according to the above article.
28Kwhr * .2 = 5.6kwhr per day.
But that's not the end. The generator is 95% eff at best to 85% for a good one.
5.6* .85 = 4.8kwhr per day.
Any additional power transformations you add will reduce power out.
Best to have the generator attached to the propeller directly. The Gorlov turbine can be used vertically. Eliminating any gears, belts which reduce total power. The torque is high on the shaft, will need a very beefy bearing. Maybe use a front wheel bearing from a vehicle. Two bearings on a shaft are needed, second one is a pillow bearing?
Putting a shroud around the propeller can increase the generated power. I don't have any numbers on how effective it can be. A smaller dia propeller could then be used. Use the equations to figure a propeller dia that meets your energy needs. Always can use extra larger or two smaller generators and use power to heat water...
Sure you don't want to build a larger wind machine? Might be easier.
Have fun.