Tidal power plants use the potential and the kinetic energy of sea water. The tides are caused by the rotation of the earth as well as the force of gravity of the moon and the sun.

The water of the tides is stored in natural bays which are separated from the ocean by an artificial dam. In times of rising tides the water passes the dam through several tubes and drives half of the installed generators. The other half of the generators are used when the water gets back to the sea passing through other tubes.

In order to get enough energy a tidal lift of more than three meters is necessary. Good coastal regions provide tidal lifts of 10 meters.

Some power plants do not store the water. These plants use only the tidal flow. The disadvantage is that they can only generate electricity in time of rising or falling tides.

The power that can be generated from storage tidal power plants is less because the pressure and the falling height of the water is smaller.