Is marine energy renewable or non-renewable Why

Ocean energy: the untapped energy source

It is all the more important to tap this energy source of the future worldwide with innovative solutions. These are designed for the various forms of ocean energy: mechanical, thermal and physico-chemical. Probably the best known is the mechanical use of ocean energy by means of tidal, current and wave power plants. In addition, there are also more “exotic” methods. Ocean Thermal Energy Conversion (OTEC), for example, use the high temperature difference between water masses, as occurs in particular in the equatorial seas. Osmosis power plants make use of the difference in salt content between fresh water and sea water.

Electricity through current

Tidal power plants use the mechanical energy that is released in the natural alternation of ebb and flow. For this purpose, river mouths or natural sea bays are separated from the open sea with dams. The classic among tidal power plants and still one of the largest of its kind today is the tidal power plant built in 1966 near Saint-Malo in Brittany.

Current power plants convert the kinetic energy of large water currents naturally occurring in the sea into electrical energy. No weir is required for this. One example of this is the TRITON S40 platform in Nova Scotia, which can generate up to 2.5 megawatts of power in strong tidal currents. Ocean current power plants have great potential, but the technical requirements are also immense.

The strength rests in the wave

A temporally and spatially less regular, but very energetic type of ocean movement are waves. In wave power plants, the up and down movements of the waves are used, for example with the help of buoyancy or floating bodies, pneumatic chambers or other approaches to energy conversion. The world's first commercial wave power plant with an output of 300 kilowatts was commissioned in 2011 in the port city of Mutriku in northern Spain. In Germany, an overall wave power plant system is currently being tested and further developed as part of the NEMOS project. The BMWi is funding the project with around 1.7 million euros.

Energy from the deep

Ocean thermal gradient power plants (OTEC) use the differences in water temperature to generate electricity. In seas close to the equator, the temperature difference between the warm surface water and the cold deep water at a depth of 1,000 meters can be 20 to 25 degrees Celsius. With the help of heat engines, this “energy storage” can be tapped and used to generate electricity. A marine thermal power plant with a capacity of 105 kilowatts is operated in Keahole Point (Hawaii) and can supply 120 households. Projects are planned for the future which will enable the supply of 100,000 households for an electricity price of 20 cents per kilowatt hour. In contrast, the yield from osmosis power plants, in which the gradient in the salt content of freshwater and seawater is used, is still modest. The 4 kilowatt hours generated by the world's first micro power plant in Tofte, Norway on the Oslofjord, are just enough to make tea.