Ocean power encompasses five different types of technologies that exploit the following phenomena: tidal rise and fall (barrages), tidal/ocean currents, waves, temperature gradients, and salinity gradients.

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About ocean power

Five different ocean energy technologies under development aim to extract energy from the oceans. 

Technologies

Tidal power: the potential energy associated with tides can be harnessed by building a barrage or other forms of construction across an estuary.

Tidal (marine) currents: the kinetic energy associated with tidal (marine) currents can be harnessed using modular systems.

Wave power: the kinetic and potential energy associated with ocean waves can be harnessed by a range of technologies under development.

Temperature gradients: the temperature gradient between the sea surface and deep water can be harnessed using different ocean thermal energy conversion (OTEC) processes.

Salinity gradients: at the mouth of rivers, where freshwater mixes with saltwater, energy associated with the salinity gradient can be harnessed using the pressure-retarded reverse osmosis process and associated conversion technologies.

 

None of these technologies is widely deployed as yet. Tidal barrages depend on conventional technology, but only a few large-scale systems are in operation worldwide, notably the 254 MW Sihwa barrage (South Korea) operational since 2011 and the 240 MW La Rance barrage in France, which has been generating power since 1966. Other smaller projects have been commissioned since then in China, Canada and Russia.

Tidal and wave power have been under development since the 1970s. Many design concepts are still being researched, and the leading ones have now reached the point where megawatt scale installations are being demonstrated, and initial deployment plans involving arrays of devices are being developed. Although devices are under development in many countries, a concentration of effort in both development and demonstration is under way in the United Kingdom, and particularly in Scotland. Also dedicated efforts are being made in the New England region of the United States and the province of Nova Scotia in Canada.

Tidal projects produce variable, but highly predictable, energy flows. Generation from wave power will be variable, depending on the sea state. The engineering challenges associated with efficiently intercepting energy from wave or tidal power are significant, particularly given the need to survive and operate in difficult conditions. Other issues that need to be considered include impacts on marine life, the marine environment and other marine users such as shipping, fishing industry, etc.

Projects involving OTEC have so far been restricted to relatively small-scale applications, although plans and design efforts have been aimed at larger installations. Salinity gradient technology is still at the R&D and pilot plant stage.

 

Ocean power generation and projection by region

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IEA, (2015), Medium-Term Renewable Energy Market Report 2015, OECD/IEA, Paris.

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Fast facts

  • 0.53 GWGlobal ocean power capacity in 2014