# Velocity more efficient than volume?

## Main Question or Discussion Point

Here are two equations showing a nearly equivelant energy output for a given volume and velocity of water. Using the formula:

EKin = M/2 x Vsquared

250/2 x 15.34m/s x 15.34m/s = 29,414 KW (requires 5 times more volume)

50/2 x 35m/s x 35m/s = 30,625 KW (requires only 2.3x more velocity)

Since the velocity is squared, isn't it better to look to use velocity over volume? IF velocity can be acheived through another means other than water pressure via water depth, wouldn't that be the most efficient way to go?

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Mathematically, yes, it is.

Practically?
$$v \propto \sqrt{h}$$
where h is the height of the water and pressure
$$p \propto \rho g h$$
This depends on desinty of water and height. If you want to double velocity, you'll 4x the height, which 4x the pressure...It'd be a challenge to find material that can withstand that...

drewman13 said:
Here are two equations showing a nearly equivelant energy output for a given volume and velocity of water. Using the formula:

EKin = M/2 x Vsquared

250/2 x 15.34m/s x 15.34m/s = 29,414 KW (requires 5 times more volume)

50/2 x 35m/s x 35m/s = 30,625 KW (requires only 2.3x more velocity)

Since the velocity is squared, isn't it better to look to use velocity over volume? IF velocity can be acheived through another means other than water pressure via water depth, wouldn't that be the most efficient way to go?
Water depth? You will still have to get the water to a sufficent height above the outlet in order to get the pressure. You will also have to refill this depth of water in order to maintain pressure. That means using energy to get all this water from the working level to the top.

Are you thinking that you can just put a hose deep in the ocean and water will flow up to land with the pressure from the depth? I hope not Integral
Staff Emeritus