## Tidal Power

Tidal power is a relatively new field of obtaining power
through using the steady and predictable changing of the
tides. There are two main methods of obtaining power
through tides; the first is to use the velocity of changing
tides to power what is essentially an underwater wind
turbine and the other is to use capture water during high
tide to form essentially a tidal dam.## Tidal Stream Generators

Tidal stream generators function very much like a traditional wind turbine. The water has a velocity towards or away from the shore when the tide is coming in or receding. This stream of water can be used to run a turbine to obtain power. Unlike wind turbines, this form or power generation is very predictable, constant, and has the potential to be used in a multitude of places due to the only requirement being changing tides. Also this method produces much more power than wind for the same velocities of wind or water due to the density of water being much higher than air.

http://nared.org/marine-energy/tidal-power/

The available power for the turbines used in tidal stream generators is very easy to calculate and can be found by multiplying the energy available from the water by the efficiency of the turbine.

$P=(\rho *A*{V}^{3})/2*{C}_{p}P=(\rho *A*V^3)/2*C\_p$

where ρ is the density of the water, area is the turbine swept area, V is the ambient water velocity, and Cp is the efficiency of the turbine.