Marine energy is one of the least utilized forms of renewable energy in the world today. However, the oceans and seas possess immense energy potential that, if harnessed properly, could meet a significant portion of global electricity demand. This form of energy has multiple sources, such as waves, tides, ocean currents, thermal gradients, and salinity gradients. Despite its advantages, its development has been slow due to high costs and associated technological challenges.
Types of marine energy
There are several ways to harness marine energy , each with its own technologies and challenges. Here we detail the main ones:
Wave energy
Also known as wave energy , this form of marine energy is obtained by harnessing the movement of waves on the ocean's surface. Waves are generated by the action of wind on water, and since wind originates from solar radiation, we can consider wave energy as a derivative of solar energy.
Waves contain a large amount of kinetic energy due to their oscillatory motion. Some areas of the planet, particularly those with constant winds, have considerable potential to harness this type of energy. For example, in regions of the North Atlantic Ocean, the energy contained in waves can reach up to 70 MW per square kilometre.
Various technologies exist for capturing wave energy. Notable devices include oscillating water columns , attenuators , and floating terminators . These mechanisms transform wave motion into usable energy using turbines or hydraulic systems.
Tidal energy
Tidal energy is generated by harnessing the rise and fall of water levels caused by tides, which are driven by the gravitational pull of the sun and moon on the oceans. This predictable phenomenon makes tidal energy a highly reliable source of power.
The main systems used to capture tidal energy involve building dams in coastal areas where the water level changes significantly with the tides. When the dams are opened, the water passes through turbines, generating electricity.
A notable example of the use of this technology is the La Rance tidal power plant in France, which has a capacity of 240 MW.
Energy of ocean currents
Ocean currents are movements of water masses that occur in the oceans due to the action of wind and other geophysical factors. To harness the kinetic energy of these currents, underwater turbines similar to wind turbines, but adapted to the aquatic environment, are used.
The main challenge for the development of this technology is the irregularity in the speed of ocean currents, as well as the technical and economic difficulty of installing and maintaining the turbines on the ocean floor.
Thermal gradients
Thermal gradient energy is based on harnessing the temperature difference between surface waters, which are heated by solar radiation, and deeper waters, which remain cold. This phenomenon occurs in tropical or equatorial regions, where the temperature gradient between the surface and the ocean depths is significant year-round.
To transform this energy into electricity, systems that operate according to a thermodynamic cycle (generally the Rankine cycle) are used. However, the profitability of these plants is still limited due to the complex and expensive systems required for their operation.
Saline gradients
Salinity gradient energy , or blue energy , is obtained by harnessing the difference in salt concentration between seawater and freshwater in rivers. This energy is primarily captured through osmosis or reverse electrodialysis processes.
This technology is currently in an experimental phase, with pilot projects such as that of Statkraft in Norway, which opened the world's first osmosis plant in the Oslo Fjord.
How to harness this energy
Harnessing marine energy remains a challenge, but its potential is enormous. Wave energy has made the most progress in terms of research and development, with pioneering projects in places like the UK and Portugal. However, tidal energy , despite its more localized impact, has been used successfully in locations such as La Rance, although it has not been widely replicated due to its significant environmental impact.
Ocean currents , while promising, face the problem of maritime traffic in some areas of high interest. However, if the technology to deploy turbines in sufficiently deep waters is developed, this drawback could be reduced.
On the other hand, the use of thermal and saline gradients is still at an experimental stage and is not profitable at the moment. However, this does not mean that these technologies have no future, since investment in research and development continues.
The potential of marine energy in the future
The development of marine technologies has been slower than other renewable sources such as wind or solar energy, but their potential is evident. According to the International Energy Agency, by 2050, marine energy is expected to contribute 10% of electricity generation in Europe, which shows a promising horizon.
The development of new technologies, coupled with increased international cooperation, is driving many pilot projects around the world. Regions such as Scotland, Spain and Norway are leading the way in this area, with projects targeting wave and tidal energy.
In Latin America, countries such as Chile, Brazil and Mexico have begun to develop their own marine energy projects, showing that interest in these technologies is beginning to globalize.
With the support of government policies and adequate funding, marine energy could become an integral part of the global energy mix in the coming decades. This energy source is not only renewable and inexhaustible, but also has a low environmental impact and could generate thousands of jobs in the renewable energy industry.
As technological advances and costs continue to decline, marine energy will play a crucial role in the transition to a clean and sustainable energy future.