Tidal energy, what is and how does it work?

Tidal Energy

One of the lesser-known yet highly promising forms of renewable energy is tidal energy. Today, we will explore tidal energy

We live on a planet where 70% of the Earth’s surface is covered by water, with 97.6% of it belonging to the seas and oceans. This reality, which is often overlooked, shows that our existence is intimately connected to the waters that surround us and shape our geography. Throughout human history, we have harnessed the power of these waters for various purposes, building our societies in harmony with them and understanding their complex dynamics through observation over time. In the present day, this importance has only grown, as the sea, in addition to being a source of food and a vast transportation network for goods, has proven to be a crucial source of energy resources. The era of renewable energy has set its sights on the sea due to its immense potential. And here is where appears the tidal energy.

Perhaps the first question to answer is, what is tidal energy? We can define it as a type of alternative renewable energy that, through the use of technology, harnesses the movements of tides, which are caused by the gravitational influence of the sun and the moon, to generate clean electrical energy. Its major advantage is that it’s a highly predictable renewable energy source, unlike other sources that depend on less predictable weather phenomena like sunlight or wind. The reason for this predictability is that we have a precise understanding of tidal cycles, allowing us to know when we can incorporate electricity generated by tides into the energy mix. Interesting, isn’t it?

How does tidal energy work?

As we mentioned, water moves due to the gravitational influence of the moon and the sun on our planet. This force deforms bodies of water, causing them to move and generating currents and tides. Anyone with even a minimal understanding of marine environments is familiar with high and low tides. Tidal energy facilities take advantage of these water fluctuations to generate energy. How? Let’s look at it based on the type of facility:

Tidal Range Facility

Tidal range facilities are similar to hydroelectric power plants adapted to a marine environment. By constructing one or several retaining walls (dams) to create an artificial difference in water levels, water is trapped through filling channels when the tide reaches its peak. The flooded gate is in an elevated position relative to the natural water level when the tide begins to ebb. It’s at this point that the channel gates are opened to allow water to flow through turbines. The turbines’ blades start to rotate, driving a generator that produces electricity.

Tidal range facility
Tidal energy type: Range Facility

Despite the seemingly simple process, building such facilities requires highly specific conditions. There are very few locations that meet the necessary criteria for such installations. Furthermore, these facilities have a significant environmental impact as they are often situated in estuaries or bays that are altered for human use.

Throughout this process, the role of electrical equipment located near the stations is crucial. Once the energy is generated, it flows through the transmission network and reaches a substation, where its voltage is increased to enhance efficiency during transportation and minimize losses. Devices like electrical transformers come into play here, facilitating the voltage conversion, and primary distribution cells function as large switches to protect the entire substation in case of any issues. Once the energy is transformed, it travels to high-voltage towers to be transported to consumption points.

Tidal Stream Generator Facility

This is an installation composed of a set of generators anchored to the seabed, which can be compared to wind turbines and are designed to harness the movement of water in a manner similar to wind turbines. This is the least invasive type of facility in terms of the environment and has lower costs compared to other options. As a result, it is gradually gaining market share over other solutions.

Tidal Stream Generator Facility
Tidal energy type: Stream Generator Facility

When currents pass through a “Tidal Stream Generator” (TSG), the kinetic energy of the water flows through the turbines, much like wind currents do in traditional wind turbines. This causes the turbines to turn, generating the motion needed for a generator to start operating. Voilà, we now have electrical energy.

Similar to the previous type of facility, the electrical energy needs to be transported. Since these facilities generate power in smaller capacities, the electrical energy passes through transformation centers, which treat the electrical energy, protecting the grid at all times, and distribute it directly to consumption points.

Dynamic Tidal Power (DTP) Facility

The last type of tidal energy facility is the dynamic or DTP (Dynamic Tidal Power). This is still a theoretical technology that aims to harness the interaction between kinetic and potential energies generated by tidal currents. To achieve this, large dams, typically 30 to 50 kilometers long from the coast to the sea, are proposed. These dams do not enclose an area as traditional dams do but create a T-shaped dike that generates a difference in sea level on either side of the longer dike. Turbines are then used to capture the water transfer from one side to the other.

Dynamic Power Facility
Dynamic Power Facility

Some estimates suggest that one of these facilities could generate between 6 and 17 GW of power, but they would require specific geological conditions, which are typically found in countries like South Korea or the United Kingdom.

What are the advantages and disadvantages of tidal energy?

The enormous potential of tidal energy is undeniable, but there are various advantages and disadvantages to consider with these types of installations. Let’s look at some of them:

Primary Advantages:

  • It is 100% renewable energy.
  • Production remains constant during tidal changes.
  • Tidal cycles are predictable, allowing for energy production estimation.
  • Energy generation density per installation is higher than other energy sources.
  • Maintenance costs are relatively low.
  • Tidal range facilities can act as flood defenses.
  • There are no waste products from electricity generation.
  • The lifespan of these facilities is estimated to be between 75 and 100 years, reducing annual operating costs.
  • The capacity factor of such facilities is around 80%, similar to a thermal power plant but without emissions.

Primary Disadvantages:

  • Certain types of facilities, such as tidal range dams, require high construction costs and are vulnerable to unforeseen changes in conditions.
  • Specific geographic and topographic conditions are required, limiting installation and scalability on a global level.
  • Tidal range facilities have a significant impact on coastal environments.
  • Effective power generation is limited to a maximum of 10 hours per day, coinciding with tidal fluctuations.
  • Energy transport from the coast to the land requires investment.
  • Like other technologies, anti-corrosion measures are necessary to withstand the corrosive effects of seawater.

As we can see, tidal energy has tremendous potential, but it is highly dependent on the geographical location where it is installed. Just like other forms of renewable energy, a technical feasibility study is required to determine the energy difference that tides can generate based on the topographic conditions of the installation site. Currently, tidal energy is significant in countries such as South Korea, France, Canada, the United Kingdom, and Norway. France was the first country to experiment with tidal energy in the 1960s, with the Rance power plant still in operation.

Now that we know what tidal energy is, what other types of marine energy are there?

Given the variety of impacts that the seas have on our geography, there are numerous types of renewable technologies designed to harness the power of water to our advantage. Whether in estuaries, marshes, coastlines, or the open sea, there are different types of technologies, which can be summarized as follows:

  • Tidal current energy: Involves harnessing the kinetic energy of ocean currents to generate electricity.
  • Wave energy or wave power: Utilizes the mechanical energy of waves through their movement to generate electricity.
  • Ocean thermal energy or ocean thermal gradient energy: Extracts energy from the temperature difference generated by currents between the surface waters and the seabed, generating electricity through this thermal variation.
  • Tidal energy or tidal power: We’re already familiar with how it works 🙂