Electricity is generated through the revolution of turbines installed in a dam built across a river. Turbines are designed to work for both the ebb and the flow directions. These turbines move due to tidal movements.
Tides are predictable; hence, they are an ideal source of energy. Tides move in and out of rivers and estuaries in a cycle of about 12.4 hours, that is, two tides for every 24 hours and 50 minutes. Sluices and turbines are installed to generate electricity from the movement of tidal waves with two basic options for its design and operation. These are called the ebb generation and the two-way generation. In the ebb generation, sluices are opened to allow water to fill in the basin up to the full normal level and then it is closed during high tide. Having water level on both sides, turbines are used as pumps in order to raise the level of water higher in the basin. Water is held back for one to two hours before sluices are again opened, allowing the water to flow through the turbines during low tide. In the two-way generation on the other hand, water is not held during full tide; thus, the water just flows through the turbine. Ebb generation produces higher amounts of electricity for a shorter period of time, while two-way generation produces lower amounts at a much longer period.