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Energy from below the surface of the seas
The power of the tides represents a nearly untapped source of clean energy. As the energy density of water compared to wind is 800 times higher, power generation is much more efficient. Additionally, the energy yield of an ocean power plant is highly precisely predictable and thus enhances the planning security in electricity output, as tidal currents are determined by the gravity of the moon and the sun. Therefore ocean power plants can be installed wherever ebb and flood generate strong currents.
This global availability leads to an estimated output potential of 800 Terawatt hours per year – an amount of electricity, which is enough to supply 250 million households with clean energy.
In 2008, the world’s first commercial tidal current power plant SeaGen began operating off the Irish coast. It produces 1.2 megawatts of electricity. This is enough to supply a town of 1.500 households, solely from the power of the tides. The system is developed by British-based company Marine Current Turbines Ltd..
From a technology point of view SeaGen looks like an underwater windmill. It consists of two, twin axial flow rotors mounted on a support structure. Each of its two drive trains weighs 27 tons and is equipped with a rotor measuring 16 meters in diameter. To minimize installation costs, the support structure or crossbeam is mounted on a single pilling structure. In order to utilize the currents of ebb and flood, the rotor blades can be turned through 180 degrees. This means that the system can produce electricity for up to 20 hours a day regardless of weather conditions and primary energy costs. During operation, the rotors are located at least three meters below the water level. But to allow a safe and easy maintenance the crossbeam can be raised above the sea level. The current project is only a starting point. Siemens believes in the potential of tidal power plants and keeps investing in this technology alongside its partners.