The sea is one of the most powerful and underused sources of renewable energy. Among all renewable energies, those derived from marine resources stand out for their potential. The reason for their efficiency is that, being vast open areas, like the oceans, they do not face barriers or shadows that block the wind or currents, which allows for maximum use of these resources. Below, we detail the main sources of marine energy and the current state of their development.
Offshore wind
La offshore wind power It is one of the most developed and competitive technologies in marine energy. At the end of 2009, the installed capacity of offshore wind energy reached 2.063 MW. Denmark and the United Kingdom lead the sector, but countries such as China are advancing rapidly, investing in cutting-edge technology to increase the efficiency of offshore wind turbines.
The potential for offshore wind energy is huge, especially in deep oceans, where floating wind turbines are gaining ground. The advantage of these locations is that the winds are more stable and of higher quality due to the absence of obstacles such as mountains or buildings, allowing for greater, consistent power generation.
It is estimated that 80% of the planet's wind resources are found in the sea, making this technology key to the future of renewable energy. In addition, floating platforms They are a solution to harness the winds in deep ocean areas, further boosting the growth of this industry.
An example of this development is the offshore park Hywind, located in the North Sea 25 km off the coast of Scotland, which uses floating wind turbines. This type of solution is expected to expand widely in the near future.
Wave energy
La wave energy Wave energy uses the undulating motion of the water surface to generate electricity. Although still in the experimental stages, this technology has great potential, especially in areas with strong waves such as the Atlantic coast of Europe.
There are different types of technologies in development to capture this energy:
- Oscillating Water Column (OWC): An innovative project using this technology is being developed in the Basque Country. It consists of a semi-submerged column where the movement of the waves compresses the air contained in the column, which moves a turbine that generates electricity.
- Attenuators and absorbers: These devices capture the movement of the waves and convert it into mechanical energy, which is then transformed into electricity.
- Overflow systems and terminatorsThese systems take advantage of the impact of waves on a structure to generate electricity.
In Motrico (Spain), several wave turbines have already been installed that generate up to 296 kW, demonstrating that wave energy is a growing reality in the field of renewable energy.
Tidal energy
La Seawater energy It is generated by taking advantage of the rise and fall of the tides. Most of the current tidal power systems are based on the construction of a dam that creates a natural reservoir. During high tide, the water fills this reservoir and, later, when the tide goes out, the water is released through turbines that generate electricity.
One of the oldest and largest examples of this technology is the tidal power plant in La Rance in France, which has been in operation since 1966. Although these systems have limitations, such as the need for waves to be at least 5 metres high and the potential disruption of coastal ecosystems, they remain a viable option in places with strong tides. South Korea also has similar facilities.
Energy of ocean currents
Another option to obtain energy from the sea is through marine currents. Like wind energy, this source uses the force of the continuous movement of water to move submerged turbines that generate electricity. The most representative example is the system SeaGen, an offshore turbine located in Strangford Sound. This system can generate up to 1,2 MW per day, making it one of the most efficient offshore current energy projects.
Although Spain does not have areas with ideal sea currents for this type of project, some areas, such as the Strait of Gibraltar and the Galician coast, could host this type of installation in the future.
Oceanic thermal gradient
This energy source is based on the temperature difference between the sea surface and deep waters. In tropical and equatorial regions, where the difference can exceed 20ºC, it can be used to generate electricity. The system uses a thermodynamic cycle, like the Rankine cycle, to move a generating turbine.
Although this technology is in its early stages of development, countries such as India, Japan and Hawaii are investing in research into these tidal power plants.
Salt gradient and osmotic pressure
The use of the saline gradient, also known as blue energy, is based on the difference in salt concentration between seawater and river water. Through the process of osmosis, this difference generates energy that can be converted into electricity. In Norway, one of the first osmotic power plants is being developed in the Oslo Fjord.
The use of these technologies has enormous potential, as river mouths and river deltas around the world offer numerous opportunities for their implementation.
Although the sea offers multiple energy resources with immense potential, most of the technologies that harness them are still in the research or development phase. One exception is offshore wind energy, which already has a technological maturity and is competitive in the market.
The main obstacles to the mass development of marine energy are the high costs of implementation and the need for further technological progress to ensure efficient and sustainable production. However, the future of renewable energy will largely depend on the advances made in this sector.