Everything about tidal power

Making the most of the tides

What is tidal power?

Tidal power, also called ocean energy, is a type of renewable energy that is capable of making the most of the movement of tides and transforming it into electricity.

Tidal power is therefore a source of clean and endless energy, so it's a perfect option to advance towards a more sustainable energy system. Platforms such as BiMEP, the Biscay Marine Energy Platform, whose main function is the testing and demonstration of offshore wave catchers, confirms that oceans and tides can be a great ally in renewable energy.

Currently, thanks to R+D+I (research + development + innovation), renewable energy sources constitute a key piece to comply with the Paris Agreement objectives and reduce greenhouse gas (GHG) emissions. For its part, the International Energy Agency (IEA) affirms that the participation of renewables in the global electric supply “will go from 26% in 2018 to 44% in 2040”, which will also have a positive economic effect on the global economy and development.

The different types of marine energy

Before going further into tidal power and its role in the energy transition, it's worth clarifying that our oceans can provide us with energy in many different ways:

Tidal power: as we have seen, it makes the most of the rise and fall of the tides produced by the gravitational attraction exerted by the sun and the moon on our planet. It's an easily predictable natural phenomenon from which the movement of water can be transformed into electricity.
Wave power: It makes the most of the movement of the waves. In this case, radiation from the sun causes an uneven heating of the Earth, which leads to the displacement of air masses and the formation of wind that causes waves.
Current power: The kinetic energy from marine currents is used.
Thermal gradient or ocean thermal energy conversion: based on the temperature difference between surface waters and deepwaters, the thermal energy of the sea is made the most of.
Salinity gradient energy or blue energy: Energy is obtained from the difference in salt concentration that exists between seawater and that of rivers.

What advantages does tidal power have?

It's a renewable and clean energy

It's an endless energy source that also doesn't emit any greenhouse gas, nor needs additional fuels, so it's environmentally friendly.

It's highly predictable

Tidal cycles are easy to predict and therefore to manage. The power that each tidal power plant can offer can be known in advance, so it's a reliable electricity production system.

It's efficient at low speeds

Tides can generate electricity at very low speeds since in their case the most important thing is the high volume of the water mass and not so much the speed of its displacement.

As well as these advantages, you also have to bear in mind that tidal power plants have a very long useful life. To date, there are still few power plants of this type, but the results are very positive. For example, the first tidal power plant was built in Rance (France) in 1966, so it has been operational for more than 55 years, and it's estimated that it will be able to generate electricity for much more time. Below we'll learn in more detail how these types of power plants operate.

How does a tidal power plant work?

Tidal power plants are responsible for the process of transforming tidal power into electricity. To manage it, underwater installations that meet some very specific geographical conditions are required.

According to the IDAE, Institute for the Diversification and Saving of Energy, a tidal power plant has to be installed in an estuary, a bay, or sea inlet where the difference between the high tide (maximum sea level) and low tide (minimum sea level) is more than 5 meters. Taking these characteristics into account, tidal power plants are built with turbines and alternators that with the turn of their blades and the circulation of the water itself can produce electricity.

Types of tidal power plants

Depending on how the electricity is generated, there are 3 types of tidal power plants:

Tidal barrage: This is a dam located at the highest point where the tide reaches. When the tide rises, the dam gates are opened to allow water to reach the reservoir. And when this reaches its maximum level, they are closed. Later, when the tide lowers, the gates are opened and the water from the inside of the reservoir goes out to sea, putting the turbines into operation. This type of tidal power plant is one of the less common, as there aren't many geographical areas that have the ideal conditions to build them.
Tidal stream generator: Tidal stream generators, also called TSG, use the kinetic energy of water in constant motion. In this case, the propellers of the turbines turn, transferring energy to a generator that transforms it into electricity.
Dynamic tidal power or DTP: This type of tidal power plant could be classed as a combination of the two previous ones. The passage of the different currents moves the propellers of the large dams causing the generation of energy.