# Calculate the total available energy from a water stream by use of a t

1. Jun 13, 2013

### bobmurray1

I keep confusing myself on this question, basically i want to know how you would determine the amount of potential energy you could capture by using a turbine, if water is flowing down a pipe into a river.

The change in elevation from the start to end of pipe is 30 meters.
The pipe is 100 meters long.
Water is flowing at a rate of 10 liters per second.

Not assuming the efficiency of the water turbine itself, is the formula just the potential energy minus the friction in the pipe? Thus:
Power per time = (Mass Flowrate X Gravitational constant X Change in Elevation) - Friction losses
= ((10 L/s X 0.001 m3/L X 1000 kg/m3) X (9.81 m/s2) X (30 m)) - Friction
= (2943 W/s or 2.94 kW/s) - Friction

Also second question, I know how to calculate the friction in a pipe, but the problem i cannot get my head around is that because the pipe is nearly a meter in diameter, the pipe is not full of water, thus i dont know how to calculate Reynolds number etc? Any help here would also be appreciated,

Thanks Guys

2. Jun 14, 2013

### 256bits

If only you knew the velocity of the stream....

Why not try v = Q/A ; Q = volumetric flow rate, A = area of the stream, v= average velocity

See as a reference,
Open channel flow
http://mysite.du.edu/~etuttle/tech/opench.htm