Ocean Currents: A Renewable Energy Source

The energy of ocean currents offers an inexhaustible source of clean, green, renewable energy. Technology for converting the mechanical energy of ocean tides to electrical energy is still in development, and primarily experimental; however, some pilot projects around the world demonstrate the potential of marine power to someday make a relevant contribution to the electrical grids of major cities. Tidal stream technology employs underwater turbines that turn with the currents to produce electricity. As fuel costs increase, along with concerns over global warming and pollution, depletion of natural resources, and fair distribution of resources, tidal power is an attractive alternative energy source.

In a tidal stream system, the kinetic energy of moving water is used to power underwater ocean turbines. Turbines are either suspended in water or anchored to the ocean floor. These turbines function like underwater windmills, using the pressure of moving water to rotate a shaft connected to a generator. Cables connect the underwater generator to land-based power grids, in the same way that traditional power lines are connected. The ideal location for a tidal stream turbine would be the entrance to a bay or river, or between islands, where water flows at a rapid pace.

Although wind and solar technologies have been in development for decades, tidal stream technology offers certain advantages. Tide patterns are easy to determine based on the position of the sun and moon. Water density is much greater than that of wind, and therefore a single generator can provide more electricity than a wind generator, at a lower velocity. Tidal power generation is more efficient than wind power, and tidal stream turbines are smaller in diameter than wind-driven turbines.

Pilot projects are underway at select coastal locations around the world. Some examples include the first undersea turbine for commercial use, which began feeding Ireland's national electric grid in Strangford Lough, Northern Ireland, in July 2008. Once it is operating at full capacity, the Sea Gen turbine, equipped with two rotors, will produce 1.2 megawatts of power, enough to provide power to about 1000 homes. Tidal Stream Energy is developing plans to create tidal farms off the coast of British Columbia, Canada. The tidal farms will include many small generators, with a potential to provide over 800 megawatts of power, or enough to power about 140,000 homes. In the United States, Verdant Power has installed tidal turbines in New York's East River. The Roosevelt Island Tidal Energy project (RITE) is the world's longest running grid-connected collection of tidal turbines, and is expected to produce electricity for commercial use in the near future.

Tidal stream technology is part of the emerging alternative energy industry. This technology has tremendous potential for reducing dependence on non-renewable energy sources. Once the technology is place, ocean currents will provide an inexhaustible source of energy, with maximum output, low overhead and maintenance costs, and minimal impact on the environment. As long as we have the sun and the moon pulling at our oceans, we will have all the energy we will ever need.

Sources

(1) Sea Gen, Sea Generation Ltd.
http://www.seageneration.co.uk/
(2) Verdant Power
http://www.verdantpower.com/
(3) Tidal Stream Energy
http://www.tidalstreamenergy.com/