On our planet, nature has fundamental importance and provides us with incredible resources, which – increasingly – we must learn to understand and use consciously and responsibly to respond to growing energy needs with low environmental impact solutions.
From water, particularly that of the sea, it is possible to obtain tidal energy, a renewable source that uses ocean tides to generate electricity. This is clean energy with significant potential, but before any evaluation, it is essential to understand how it works, what the advantages and disadvantages of its application are, and how it is already used.
What is tidal energy?
Tides are a natural phenomenon caused mainly by the gravitational force of the moon and sun on Earth, which influence water levels in seas and oceans. Tidal energy is kinetic energy generated by the periodic movement of ocean tides. The tidal cycle has two main phases:
1. High tide: During this time, water accumulates and rises along the coasts.
2. Low tide: This is when the water recedes, lowering the sea level.
To exploit this difference in height between the tides, tidal power stations or specific systems that capture the moving water’s kinetic energy during the tide change are built. This motion is then used to spin turbines connected to electric generators, which convert the kinetic energy into electricity.
Brief history of tidal energy
The use of tides to generate energy is not a recent discovery but dates back centuries. The Romans already exploited the waves to power their millstones, while in China, during the Song dynasty (between the 10th and 13th centuries), water wheels powered by the tides were used to pump water and irrigate fields.
At the end of the 18th century, the first patent was filed for obtaining energy from the movement of sea waves. However, the real revolution in tidal energy began in the 20th century with the development of modern technologies.
With growing concern about climate change and the search for renewable energy sources, interest in tidal energy has been revived. New technologies and approaches, such as underwater turbines, make this energy more efficient and economical.
Today, tidal power is gaining popularity as a clean and renewable alternative source, and projects are being developed in different parts of the world to exploit this resource sustainably.
How does tidal energy work?
The high and low tide cycles repeat constantly, thus allowing a continuous flow of water through the turbines. As I said, this system uses the kinetic energy of moving water and the difference in height between high and low tide to generate electricity. Let’s now see in detail what the steps are and how sea energy generation practically works.
Tidal Range Weir or Reservoir
In an appropriate coastal region, a weir, or some reservoir, is constructed to capture rising water at high tide and release it at low tide.
Ebb and flow of the tides
Twice a day, water enters the area enclosed by the tidal system at high tide. During low tide, however, the water is retained by the weir.
Turbines or hydro generators
Turbines or hydro generators are installed inside the dam. When water is released at low tide, or when it flows through the turbines due to high tide, it sets these machines in motion.
Electricity generation
The turbines are connected to electrical generators that convert the mechanical energy of the water into electrical energy, which is then transmitted to the distribution network.
Tidal control
The opening and closing of locks or valves in the reservoir are controlled to regulate tidal flow and maximize energy production.
How is tidal energy produced?
Tidal energy can be produced in several ways:
Tidal currents: Some facilities take advantage of marine currents, using submerged turbines or floating installations to capture the kinetic energy of moving tides.
Weirs: This is the most common method. A large weir captures water at high tide and releases it at low tide, turning the turbines.
Tidal lagoons: Tidal lagoons are coastal areas with natural or artificial barriers. During high tide, water is trapped in the lagoon and released through turbines during low tide.
Cogeneration plants
Cogeneration systems are exciting to improve the overall efficiency of energy use, as they simultaneously produce electricity and usable heat from a primary source, reducing the typical waste of separate electricity and heat production systems.
The objective is to use the residual heat generated during electricity production for thermal purposes, such as heating buildings or producing domestic hot water. Like thermal power plants, cogeneration plants can be powered by different energy sources, including gas, fuel oil, biomass, or biogas.
The advantages of cogeneration plants are many:
1. Allow you to reduce energy consumption
2. Reduce emissions of greenhouse gases and other atmospheric pollutants
3. Offer an opportunity to recover thermal energy that would otherwise be wasted
Tidal power stations
They are plants located chiefly in coastal regions or near estuaries, where the wave motion significantly excursions between high and low tide. The heart of a tidal power plant is usually a weir or dam that captures water at high tide and releases it at low tide.
Hydro generators
They are devices designed to convert the mechanical energy of water into electrical energy. They can be used in various applications, including tidal power plants, and exploit the principle of converting the kinetic energy of water into rotary energy, which in turn powers an electric generator.
Advantages and disadvantages of tidal energy
As sustainable, clean, and almost inexhaustible as it is, even the energy from the ocean has its pros and cons, which are worth knowing to understand better how and why these energy sources still have a limited diffusion.
| Tidal Energy Advantages | Tidal Energy Disadvantages |
| Renewable Tides are a constant natural phenomenon. | High costs Requires significant investments, especially for the creation of weirs. |
| Low greenhouse gas emissions This form of energy produces few greenhouse gas emissions. | Environmental impact The construction of dams can alter local ecosystems and affect fish migration. |
| Stable and predictable Tidal energy can be predicted accurately. | Limited location Tidal energy is only viable in a few specific coastal areas with significant tides. |
How much energy can Tidal waves produce?
Seas and oceans generate between 20,000 and 90,000 TWh of electricity annually, equivalent to billions of kilowatt hours (kWh).
Precisely for this reason, the energy of marine currents has always been exploited worldwide, even if large-scale projects are limited to a few coastal regions with significant tides suitable for the purpose.