More than 70 per cent of the Earth’s surface is covered by water, 96.5 per cent of which consists of seas and oceans. Given its volume, it seems reasonable to assume that, in this context of decarbonisation, marine energy is here to stay. That said, we may be taking the wrong approach, as Jesús Mari Blanco, coordinator of the Erasmus Mundus Master’s in Renewable Energy in the Marine Environment at the UPV, explains: ‘We always end up talking about offshore wind power, which is the sector leader, but let’s not forget wave, tidal and current energy, which are the great unknowns.’

Before we go on to discuss how this emerging technology – which some countries are already using – works and the impact it may have, we must first understand what ocean energy is. It is a form of renewable energy obtained by harnessing the movement, temperature and salinity of the oceans. Also known as marine energy, it falls mainly into two categories: wave energy and tidal energy. Other, less common sources can also be included, such as ocean thermal energy and ocean current energy.



On the one hand, wave energy is generated from the movement of the ocean’s surface. Devices designed to capture this energy convert the vertical movement of the waves into mechanical energy, which is then converted into electricity. These devices can be buoys, oscillating water columns or floating platforms that efficiently capture the movement of the waves.

Tidal energy harnesses the ebb and flow of ocean tides. There are two main methods for capturing this energy: tidal barrages and tidal currents. Tidal barrages are dams built in estuaries or bays that capture water at high tide and release it at low tide, generating electricity via turbines. Tidal currents, on the other hand, use underwater turbines positioned at strategic locations where the currents are strong and constant.

Marine energy can come from both waves (wave energy) and tides (tidal energy).

Furthermore, ocean thermal energy conversion (OTEC) is based on the temperature difference between the ocean’s surface, heated by the sun, and the cold depths of the ocean. This thermal gradient is used to generate electricity through a working cycle similar to that of a conventional power station.

The potential impact of ocean energy is significant. Firstly, it can help reduce greenhouse gas emissions by replacing electricity generation based on fossil fuels. Furthermore, ocean energy facilities generally have a smaller environmental footprint compared with other forms of renewable energy, such as solar or wind power stations. From an economic perspective, it can provide employment in coastal communities and stimulate the development of new technologies and industrial capabilities. It can also enhance energy security by diversifying energy sources and reducing reliance on imported fuels.

Pioneering countries

Several countries have begun to explore and utilise ocean energy as part of their energy mix, such as the United Kingdom, one of the world’s leaders in the exploitation of tidal energy. The MeyGen Tidal Power Plant, located in Scotland, is one of the most advanced projects in the world. This plant uses underwater turbines to harness the energy of the strong tidal currents in the Pentland Firth.

Similarly, France has been a pioneer in the development of tidal energy since the construction of the La Rance Tidal Power Station in 1966. This plant, situated in Brittany, remains one of the world’s largest tidal power facilities and has demonstrated the long-term viability of this technology.

In the United States, several wave and tidal energy projects are currently underway, particularly along the Pacific and Atlantic coasts. The US Department of Energy has funded numerous research and development programmes to advance ocean energy technology. The marine energy test facility in Oregon is an example of the country’s investment in this field.

As for Spain, the main tidal power plant is located in Mutriku, on the coast of the Basque Country. This is a pioneering facility and the first commercial tidal power plant in operation in the country. It comprises 16 reversible turbines arranged in series and is capable of generating approximately 300 megawatt-hours (MWh) of electricity annually.

But all that glitters is not gold: this type of energy also faces challenges. On the one hand, the initial cost of the facilities and maintenance can be high, and the technology is still at a stage of development that requires significant investment in research and development. Furthermore, it is crucial to assess and mitigate potential environmental impacts, such as the disruption of marine habitats and interference with the migration routes of marine life.

In any case, international collaboration and the exchange of knowledge will be essential to accelerating progress in this field. Furthermore, integrating ocean energy with other renewable sources, such as solar and wind power, can create a more balanced and sustainable energy system.

Article from Ethic magazine. Read article