The Earth’s ocean waters, pushed by wind and tugged by the Moon and Sun, ebb and flow over more than 70 percent of the planet. However, the technology for harnessing some of this kinetic energy into usable power has emerged only in recent years. These technologies involve turbines that are built on a swiveling platform, which keeps their nose cones facing the tide (whether it is coming in or going out). These kinetic hydropower systems use gearboxes and speed increasers, which convert the slower rotating rotor into a faster rotating generator so that each turbine’s mechanical power is transformed into electricity. The result resembles an underwater wind farm.
Verdant Power‘s turbines require tides that move at least 1.8 meters per second in order to generate enough energy for them to be cost-effective. A few meters away from the closest turbine, an onshore control room receives a feed of the energy created by the entire cluster. Last year, in order to prove that this energy could be usable for local businesses, Verdant sent a test transmission of electricity to a supermarket and a parking garage on Roosevelt Island, New York, in the framework of the Roosevelt Island Tidal Energy project.
Underwater turbines, submerged “wind” farms, and wave-riding electrical generators are being tested around the world. Another company that has been developing tidal wave technology is Pelamis Wave Power, which promises relief for overworked energy utilities. Although Pelamis’s devices exploit the sea with similar physical powers, they are a bit different. They are big, red tubes, each 130 meters long, about four meters in diameter, and weighing around 750 tons each. The life expectancy of such ocean power plants is close to 20 years. They flex as the ocean swells around them and the wave-induced motion of the tubes’ joints is resisted by hydraulic rams, which pump high-pressure fluid through hydraulic motors, driving electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the seabed. Three such tubes, which work best at a depth of 50 to 70 meters and roughly six kilometers from the shore, can produce up to 2.25 megawatts of electricity.
TFOT has also covered other projects that exploit the powers of nature, such as the Windhunter, that creates hydrogen, the Ocean Thermal Energy Conversion technology, which uses solar energy from the ocean, and the German Repower 5M, which is the largest wind turbine in the world.