OTEC – Deep Sea Conversion

Ocean thermal energy conversion (OTEC) harnesses the difference in temperature between the surface water (about 25°C) and the water at depth (about 5°C at depths greater than 1000 m) based on the principle of thermal exchange. Predictable and continuous, the energy produced in this way is particularly environmentally friendly and decarbonised.


Naturally present in the inter-tropical areas, this inexhaustible source of energy constitutes an effective response to environmental challenges and the energy problems faced by the planet’s isolated regions.

Naval Energies intervenes both as a system engineering leader and sub-system engineering leader at multiple levels in the OTEC field: from the design of thermal exchangers (condensers and evaporators) to the construction of complete onshore OTEC systems, with the possibility of associating co-products such as desalination, ORC (Organic Rankine Cycle) and SWAC (Sea Water Air Conditioning), in association with other industrial partners.

Our experts are also developing innovative technological building blocks, such as biofouling prevention systems and the optimisation of the energy-production system, and are working to overcome technological locks with the aim of deploying offshore OTEC plants in the longer term.


The advantages of our solutions

A pioneer on this emerging market, Naval Energies has anticipated the challenges of the OTEC systems of tomorrow thanks to its considerable technological advance and the multidisciplinary expertise of its teams. We have developed two test benches, which are unique in the world, allowing the performance of tests that can be extrapolated to full scale and thus dimension the OTEC systems of tomorrow:

  • Onshore OTEC prototype in La Réunion: installed since 2012, it allows the performance of tests on the energy cycle, the validation of system performance and the certification of critical systems. Both a research and development tool and a training platform for students at the University Institute of Technology (IUT), this prototype allows the teams to work on the main electricity-production system that could be used in future plants. This installation allows the testing of new generations of equipment to continuously improve the efficiency of the energy system and optimise the costs of the technology.


  • Test bench in Martinique: installed in 2017 in partnership with IFREMER, in the frame of the Marlin project (supported by ADEME), it allows the performance of tests on biofouling and thus improve the performance of the energy system’s thermal exchangers.


Market perspectives

Up to about thirty countries around the world could benefit from OTEC as a result of their latitude, the favourable position of their sites and the energy-mix policy adopted locally.

Located close to the equator, where the temperature differential is the highest between water at the surface and at depth, these countries possess total accessible resources estimated to be 56 GW. Thanks to the advantages offered by the pumping of cold sea water, further solutions may be added to the OTEC plants, such as air conditioning, fresh-water production or aquaculture.