Underwater turbines operate on the same principles that wind turbines use; a flow of fluid moves a set of blades creating mechanical energy which is then converted to electrical energy. They are equally troublesome for environmentalists, as wind turbines interrupt bird flights just as water turbines can disturb underwater life. One advantage water turbines enjoy over other sources of renewable energy is a predictable tide table.
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How They Work
Underwater turbines rely on tides to push water against angled blades, causing them to spin. These turbines can be placed in natural bodies of water, such as harbours and lagoons that naturally feature fast-moving flows of water. These turbines must be able to swivel 180 degrees to accommodate the ebb and flow of tides, as demonstrated by the SeaGen prototype turbine in Ireland. As the blades spin, a gearbox turns an induction generator, which produces an electric current. Other devices can be tethered and attached to a float, such as the Evopod in England. This design allows the face of the turbine to always face the direction of the current, much like a moored boat does.
Underwater turbines remove the uncertainty that other forms of energy production suffer from. While some regions like the American southwest may enjoy sunshine for the majority of the year, good for solar energy production, it is still dark at night. The tide will ebb and flood twice a day, every day, for as long as the moon rotates around the planet, meaning energy can be constantly produced 24 hours a day. Additionally, in locations where tidal currents are not particularly strong, currents can be induced by constructing a lagoon with a narrow opening. The turbine is then placed in the opening of the lagoon to catch tidal currents. Hydro-energy is a more attractive energy source than fossil fuels due to the virtually inexhaustible nature of the planet's oceans. While the price of water-resistant materials drops and implementation costs decline, the payback period on these energy sources will decrease as well.
Implementation of underwater turbines has proven to be difficult. Tides cannot be mitigated during installation, which applies force to turbine blades as they are being mounted. Blades in New York's East River have been known to snap, according to gothamist.com. Underwater apparatus can significantly change the ecosystem as well, though Popular Science reports a new type of system utilises an auger rather than sharp blades to drive the gearbox without harming marine life.
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