FreeWord – Marine Energy

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Hello folks, it’s FreeWord time. On the previous FreeWord we talked about Oceans and now is the time to go through how to turn it into energy.


We have come a long way since Frenchman Girard and his son filled the first known wave energy device patent back in 1799. Scientists and engineers have been working hard in search of sustainable ways to capture ocean energy to feed our communities’ needs with electricity. The case for ocean power has been there for centuries. As of today, ocean power technologies are based on well-understood principles derived from physics, marine design, and reliable mechanical and electrical engineering, yet we are still waiting for a breakthrough. However, there is growing confidence that ocean energy technology is maturing, and with the ability of the ocean to deliver predictable, renewable, carbon-free and sustainable energy supply, ocean energy is predicted to grow exponentially.

Global Ocean Energy recast

Ocean Power

Marine energy (also known as ocean energy) refers to the renewable energy that is generated from the world’s oceans, seas, and rivers. Currently, marine energy is the largest remaining source of untapped renewable energy in the world and represents a vast, predictable resource through various methods – wave energy converters, ocean thermal energy converters, tidal range and stream devices, and salinity gradient technologies. These technologies, once fully utilized, provide reliable, sustainable and cost-competitive electricity for the end-user.

Wave Energy Converters (WEC) – Ocean waves contain tremendous energy potential, with an average of a 1-meter wave striking a coast every 10-seconds, which can deliver more than 7mw per kilometer per coastline. Wave power devices are based on extracting energy directly from the surface motion of ocean waves. The obtained amount of energy depends on the height of the waves. In many areas of the world, the wind blows with sufficient consistency and force to produce continuous waves along the coasts. WEC devices vary due to the diversity of waves in different parts of the world – it can be located on the shoreline, near-shore, and offshore in order to achieve the highest efficiency. Discover the global theoretical potential of WEC

The National Renewable Energy Laboratory (NREL) has listed the most promising methods of producing energy regarding wave energy. These designs are undergoing demonstration testing. The following video demonstrates a variety of these technologies.

Ocean Thermal Converters (OTEC) – is a process that can generate electricity from the temperature difference between tropical surface seawater and cold seawater at 800–1,000 meters depth. OTEC’s are only efficient in tropical seas and oceans since they require a temperature difference of 20 ⁰C to achieve significant energy efficiency. OTEC is a continuous cycle process in a closed-loop. The following video demonstrates the OTEC operating principle. Some more reading: Discover the global theoretical potential of OTEC.

Salinity Gradient Energy – This technology generates power from the difference in ionic concentration between freshwater and saltwater; this occurs where a river collides into an ocean. Pressure retarded osmosis (PRO) occurs when freshwater flows through a membrane to increase the pressure in a tank of saltwater, and reverse electrodialysis (RED) with ions of salt passing through alternating tanks of salt- and freshwater. The following video demonstrates the PRO operating principle. (Discover the theoretical global potential salinity gradient)

Tidal Energy Converters – exploit the natural flow of coastal tidal waters caused by the interaction of the gravitational fields of the earth, moon, and sun. Energy tidal energy converters are separated into two main categories -tidal range and tidal stream.

Tidal Range Converters – are based on differences in tide height inside and outside the area, causing water to drain from one side to the other through hydro turbines to generate energy. It uses the same principles as hydropower and requires a natural or a man-made structure to impound a large body of water.

Tidal Stream Converters – are principally similar to submerged wind turbines and are used to utilize kinetic energy in tidal currents; which are often enhanced with topographic features and the water is flowing through narrow tunnels. Due to the higher density of water, blades can be smaller and turn slower than in wind turbines, yet they still produce a significant amount of power. The following video describes the tidal energy converters operating principle and demonstrates some of the applied technologies.  

The International Energy Agency

The International Energy Agency (IEA) supports global energy technology, research, development, deployment, and knowledge transfer through multilateral groups. Ocean energy system is one of the initiatives within the international energy agency, and it was formed to unite the efforts of every country and bring ocean energy to the market as a practical, economical alternative to traditional fuels. More countries have started to commit to this course in an effort of global cooperation and intent; 2050 goal – producing 25% of the world’s energy requirements. 


The main challenge has been the development of reliable and cost-effective technologies to make use of the enormous renewable energy potential of the oceans. For this to succeed, a clear government commitment and targeted funding is needed to create an environment that encourages investments from large multinationals to take part in a sustainable future for our planet.

Check out our interview with Wello regarding the same subject if you haven’t done it yet, and don’t forget to read our other interviews and articles on our homepage, or continue the discussion on our Facebook and Twitter pages.

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