Exploiting ocean energy through advanced design concepts

Why is this gap important?

The vast majority of ocean technologies today are either wave or tidal energy. Increasing annual generation to reach SDS levels will also require that investments be diversified towards other alternative concepts and technologies such as ocean thermal energy conversion (OTEC), salinity gradient power and ocean current technology.

Technology solutions

Ocean thermal energy conversion (OTEC) (TRL 4) is a technology to draw thermal energy from the deep ocean and convert it into electricity or commodities. This technology requires a temperature difference of 20ºC between the warm surface water and cold deep water and, as such, is only feasible in certain areas of the world; the tropics are the best area for this technology. The key uses for OTEC are to generate electricity, desalinate water, provide heating and cooling, and support the cultivation of fish or other marine life for food.

Salinity gradient power (TRL 3) is energy produced from the chemical pressure that results from the difference in salt concentration between fresh water and saltwater. This can therefore be exploited at river mouths where fresh and saline water meet. Two technologies are being developed to convert this energy into electricity: pressure-retarded osmosis (PRO) and reverse electrodialysis (RED), both in TRL 3 stage.

Finally, ocean current technology (TRL 3) can harvest energy from sea currents, which always flow in one direction and are driven by wind, water temperature, water salinity and density among other factors; they are part of the thermohaline convection system that moves water around the world. Ocean current energy technologies are being developed to capture the kinetic energy carried in this constant flow of water: the primary design concepts are based on water turbines deployed in arrays.

Ocean thermal energy conversion (OTEC) Readiness level:

Salinity gradient power Readiness level:

Ocean current technology Readiness level:

Colored bars represent the Technology Readiness Level (TRL) of each technology. Learn more about TRLs

What are the leading initiatives?

  • Leading research institutions on OTEC include TU Delft in the Netherlands.
  • Xenesys Inc. of Japan and the Pacific Petroleum Company formed a joint venture to industrialise and commercialise OTEC in French Polynesia.
  • A consortium of French industrial and public partners launched the IPANEMA initiative, aimed at facilitating the emergence of renewable marine energy technologies, including OTEC.
  • Lockheed-Martin (LM) and the Taiwan Industrial Technology Research Institute (ITRI) pledged to collaborate on a 10‑MW OTEC plant project in Hawaii.
  • REDstack in the Netherlands is a successful 1‑MW pilot plant for reverse electrodialysis technology, built along the Afsluitdijk, a 32‑km causeway separating brackish and fresh water. The pilot is highly scalable.

Recommended actions

 

Actions

Governments and regulators

Next 10 years:

  • Develop an integrated policy framework with ocean energy-specific regulations.
  • Develop international guidelines and standards.
  • Institute regulatory reform and planning, leading to efficient and appropriate consenting processes.

Industry, academia and governments

Next 10 years:

  • Develop prototype devices to withstand the marine environment through demonstration and testing facilities, research and innovation support, and enable technology support to reduce costs and improve performance.