Tides are caused primarily by the gravitational pull of the Moon and, to a lesser extent, the Sun's gravitational pull on the Earth's water masses. Tidal energy exploits the regular variations in water levels due to this phenomenon.

Here's how a tidal power generation system typically works :

Tidal dams :
Tidal dams are the most common method of harnessing tidal energy. These dams are built in estuaries or river mouths where the tides have a strong upward and downward movement.
Tidal dams use a structure similar to that of a traditional hydroelectric dam. They usually have doors or valves that open to allow water to flow through turbines when the tide rises, and close when the tide goes out.
The water that passes through the turbines spins generators that convert the kinetic energy of the water into electricity.


Subsea turbines :
Subsea turbines are an emerging technology for harnessing tidal energy. They are placed on the seabed where tidal currents are strong.
Underwater turbines capture the kinetic energy of tidal currents by rotating their blades. This rotation is then converted into electricity using a generator.
Potential benefits of subsea turbines include better integration into the marine environment and potentially lower construction costs compared to tidal dams.

- It is a renewable source of energy, because tides are predictable and will continue to exist as long as the Moon and Sun exert their gravitational influence on the Earth.
- It produces little or no greenhouse gas emissions or air pollution.
- It has a low impact on land, as tidal dams usually occupy areas where there are already human settlements, such as estuaries or ports.

However, tidal energy presents challenges, including the high construction costs of tidal dams, environmental concerns related to the alteration of marine habitats and coastal ecosystems, and the variation in energy availability with tidal cycles. Despite these challenges, tidal energy continues to attract growing interest as a long-term renewable energy source.

Operation :

Energy capture : Tidal dams use the rise and fall of tides to generate energy. They are usually built in estuaries or straits where the tides are particularly high. When the tide rises, the water is held back by gates or locks. When the tide goes out, this water is released through turbines, which generates electricity.

Turbine technology : The turbines used in tidal dams can be of different types, including propeller turbines, action turbines, or jet turbines. They are designed to work in both directions, meaning they can rotate in both directions to capture energy at both rising and falling tides.

Electricity generation cycle : Tidal dams generate electricity cyclically, usually twice a day, at high tide and low tide. Electricity generation is predictable and can be scheduled according to tide times.

Benefits :

Renewable energy : Tidal energy is a renewable energy source because it is powered by the gravitational forces of the moon and sun, which affect the tides.

Predictability : Unlike other renewable energy sources such as solar and wind, tidal energy is predictable and constant. Tide times can be accurately calculated years in advance.

Low environmental impact : Tidal dams have a relatively low environmental impact compared to other forms of energy production. They do not produce greenhouse gases and do not require large tracts of land, reducing the problems of deforestation or habitat loss.

Disadvantages :

High cost : The construction of a tidal dam is a significant financial investment due to the complexity of the infrastructure required and the high construction costs.

Impact on the ecosystem : The construction of a tidal dam can disrupt local ecosystems, altering currents and affecting the migration of fish and other marine life.

Specific location : Tidal dams can only be built in places where the tides are high enough to provide a significant amount of energy. This limits the possible locations for this type of installation.

Despite these challenges, tidal dams represent a promising source of energy for coastal regions with high tides, offering considerable potential for clean and sustainable electricity generation.

Kinetic Energy Capture : Subsea turbines are installed underwater, often attached to the seabed or submerged structures. They are positioned so that they are exposed to the sea current or tidal flows. As water passes through the turbine blades, the force of the current causes the turbine to rotate, converting the kinetic energy of the water into mechanical energy.

Electricity generation : The rotation of the turbine is connected to an electric generator, usually an alternator, which converts mechanical energy into electrical energy. The electricity produced in this way is then transported via submarine cables to the onshore electricity grid for distribution to consumers.

Types of subsea turbines :

Axial turbines : These turbines have blades arranged around a central axis, similar to the propellers of an airplane. They are designed to be installed in relatively fast ocean currents and are effective at capturing kinetic energy under a wide range of conditions.

Propeller turbines : These turbines look like large propellers and are designed to be installed in constant and powerful ocean currents. They are effective at converting energy from regular tidal currents into electricity.

Oscillating blade turbines : These turbines have blades that oscillate or oscillate with the movement of the water. They are suitable for variable ocean currents and can operate effectively in low-speed conditions.

Renewable energy : Underwater turbines harness a renewable resource, the kinetic energy of ocean currents and tides, which is powered by the gravitational forces of the moon and sun.

Predictability : Unlike other renewable energy sources such as solar and wind, ocean currents and tides are predictable, allowing for accurate planning of power generation.

Low visual impact : Being installed underwater, subsea turbines have minimal visual impact compared to onshore wind turbines or solar panels, making them more aesthetically acceptable in some coastal areas.

High upfront costs : The construction and installation of subsea turbines can be expensive due to the technical and logistical challenges involved in installing equipment underwater and maintaining them.

Impact on the marine environment : Although less visually intrusive than other energy installations, subsea turbines can impact marine ecosystems, disrupting habitats and migrations of marine wildlife.

Maintenance and durability : Subsea turbines require regular maintenance and can be prone to corrosion and wear due to the harsh marine environment in which they operate.