Tidal energy technologies convert tidal streams into electricity. Four times a day vast amounts of water are set in motion by the rise and fall of the tides. Especially suited for this kind of technology are compounded areas, such as bays or estuaries. Tidal stream technologies capture the velocity of the current and convert it into electrical energy. These devices can be placed on floating platforms, on the seabed or be integrated in existing coastal protection structures like storm surge barriers. Tidal range technologies are based on large dams and are utilising the height difference between the tides and the resulting head. They are therefore exclusively installed close to the coast. Only depending on the relative position of earth and moon this type of energy is extremely predictable over long periods of time.
Waves are found on all large open waters and are representing one of the largest resources of ocean energy. Wave Energy Converters (WECs) are capturing either the height difference created by waves or the rotation of water particles within the wave. They can be placed on the open sea, close to shore or even integrated in coastal structures. Based on these varieties, WECs are showing by far the largest range of different concepts. Waves are a result of wind but can travel very long distances without much loss of energy. This makes wave energy considerably more predictable than wind energy.
Salinity Gradient Energy
Salinity gradient power, also called “blue energy”, derives energy from the differences in salt concentration of fresh and sea water through special membranes. Salinity converters can be deployed at locations where salt and freshwater come together, such as river deltas. It can be implemented as a standalone power plant, or as a hybrid energy generation process focusing on energy recovery, for example from a desalination or water treatment plant. Blue energy provides sustainable, continuous and on demand power, 24/7.
Ocean Thermal Energy Conversion (OTEC) exploits the temperature difference between cold ocean water at a depth of 800 – 1000 metres (about 5 ⁰C) and warm surface water (about 25 ⁰C) to produce electricity or thermal energy for air conditioning. The technology is based on highly efficient pumps as well as heat exchangers and requires a temperature difference of 20 ⁰C to achieve significant energy yields. This makes it especially well-suited for equatorial and tropical seas and oceans. OTEC technologies are generating energy in a closed loop, 24 hours a day, all year round.