Drop of water
Jag_cz / stock.adobe.com
2018-06-05 expert contribution 198 0

Ocean energy – The untapped energy source

Over 70 per cent of our planet is covered with water. Wind, tides and ocean currents make the seas an inexhaustible source of energy. Ocean energy could make a significant contribution to the global energy mix. The international race to find the best technologies for exploiting this potential has begun. Included in the line-up are companies and cutting-edge technology from Germany.

Energy harvested from the ocean has unbeatable advantages. The "fuel" obtained from ocean energy is inexhaustible, is available free of charge and pollutes the environment only to a negligible extent. This makes ocean energy an ideal candidate for inclusion in the global mix of renewable energies. However, the geographical conditions for harnessing ocean energy are not to be found everywhere. And energy generation from the power of the sea is still in its infancy.

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Alexander Nollau

Ocean energy – An astonishingly versatile energy source

This makes it all the more important to use innovative solutions for developing this future energy source worldwide. These are designed to harness the various forms of ocean energy: mechanical, thermal and physico-chemical. Probably the best known method is the exploitation of mechanical ocean energy by means of tidal, current and wave power plants. However, further, more "exotic" methods are also available. For instance, Ocean Thermal Energy Conversion (OTEC) power plants use the significant temperature difference between water masses, particularly as found in the equatorial seas. Osmosis power plants take advantage of the different salinity levels between fresh water and sea water.

Water currents for current

Tidal power plants harness the mechanical energy that is released by the natural tidal rhythm. River mouths or natural bays are separated by dams from the open sea for this purpose. The classic tidal power plant, and still one of the largest of its kind today, is that built in 1966 near Saint-Malo in Brittany.

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

The power resides in the waves

Waves represent an irregular – both temporally and spatially – but highly energy-rich form of ocean movement. Wave power plants make use of the up and down motion of the waves, for example with the aid of buoys or floats, pneumatic chambers or other energy conversion methods. The world's first commercial wave power plant, with an output of 300 kilowatts, went online in 2011 in the port city of Mutriku in northern Spain. In Germany, a wave power plant system is currently being tested and developed as part of the NEMOS project. The BMWi is supporting the project to the value of roughly EUR 1.7 million.

Energy from the deep

Ocean Thermal Energy Conversion (OTEC) power plants use the differences in water temperature to generate electricity. In equatorial seas, the temperature difference between the warm surface water and the cold deep water at a depth of 1,000 metres can be 20 to 25 degrees Celsius. This "energy store" can be tapped with the help of heat engines and used to produce electricity. Keahole Point (Hawaii) operates a 105 kilowatt marine thermal power plant that can supply 120 households. Projects are planned to supply 100,000 households at an electricity price of 20 cents per kilowatt hour in the future. In contrast, the output of osmosis power plants, which use the salinity gradient of fresh and sea water, is still modest. The 4 kilowatt hours produced by the world's first micro power plant of this kind in Tofte, Norway, on the Oslofjord are just enough to make a pot of tea.

Waves of global competition reaching ever higher

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It is precisely the mismatch between potential and yield that is now spurring the international race for the most innovative solutions in the use of ocean energy. Examples of this can be found all over the world: in China, for example, the stand-alone Eagle 3 wave power plant with an output of 100 kilowatts, in Canada the FORCE Berth Holders tidal power plant, or research on a hydraulic tidal power plant in Japan. In Germany, the prospects for profitable use of ocean energy are relatively poor due to the country's geography. But German research in this field is among the best in the world, and companies from Germany are involved in numerous projects worldwide.

Standardization plotting a course for success

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VDE

This makes it all the more important to discuss and chart the future standardization course for successful ocean energy generation. The IEC/TC 114 Technical Committee (DKE/GK 385) and its IEC 62600 series of standards are responsible for this. It is working on the preparation of international standards for ocean energy conversion systems. The main focus is on converting wave, tidal and other types of water current energy into electrical energy, although other conversion methods, systems and products are also covered. The standards and specifications prepared by the TC 114 Technical Committee range from system definitions, management plans and performance measurements of wave, tidal and hydroelectric power converters through to the provision, operation and maintenance of marine power plants, tests and measurement methods.

Don't miss the "Big Wave"!

Ocean energy production in Germany does not make very high waves. The reasons for this are: the limited magnitude of the tidal energy and the waves themselves, the very low number of development projects, the high development costs and so far no prospect of a place for marine energy in the future energy mix. But the commitment of German research and industry to the "global construction sites" of ocean energy shows that this is a field in which German power engineers can excel and where involvement in this future technology – including standardization – pays dividends. Therefore, it is important not only to wait for the i-deal wave, but also to surf on it – and to adopt a pioneering spirit in shaping the ocean energy trends of the future.

What potential. challenges and trends do you see in ocean energy? Which ideas would you like to see developed? What course should standardization and engineering take? We look forward to receiving your comments and your input.

Yours etc.
Alexander Nollau