Floating Wind Turbine Harvests Energy From Ocean Currents

Harnessing the power of the world's oceans is one of the new frontiers for designers of renewable-energy generators, and now a Japanese company may be poised to make a breakthrough with a floating wind turbine that also harvests energy from ocean currents.

SKWID (Savonius Keel & Wind Turbine Darrieus) from Mitsui Ocean Development & Engineering Company (MODEC) promises to convert power from offshore winds, as well as from the ocean itself, into usable energy, according to the company. Because the turbine does not need external power to operate, MODEC envisions it being used to power remote islands or so-called "stranded" islands, where it is difficult to maintain onshore electricity facilities, as well as other applications for general electricity needs in coastal areas.

The invention is comprised of two core components -- the Savonius Current Turbine and the Darrieus Wind Turbine. The former harvests energy from ocean currents and then transmits that energy via a gearbox located in the turbine to increase the rotation of the latter, according to information posted on the company's website.

The Savonius is comprised of split-cylinder-shaped buckets that rotate in one direction, regardless of current direction, at the same speed as the current so as not to disturb the ocean ecosystem. The Darrieus is omnidirectional and rotates with a rectangular sweep, which allows it to catch twice as much wind when compared to onshore wind turbines of the same diameter that turn in a circular movement.

To ensure the turbine remains stable and impervious to ocean movement, a set of rubber mounts support the power-generation components to isolate them from any wave motion. The current turbine, which sits at the bottom of the structure like a platform that allows access to the power-generation components for maintenance, acts as a ballast that can self-right the structure during ocean movement.

Other researchers and companies are also working on ways to harvest energy from the sea, as well as its powerful offshore winds. In the US, the first offshore wind turbine was deployed off the coast of Maine thanks to the University of Maine and with support from the Department of Energy. Meanwhile, a company from Denmark called Danfoss has developed material it says could one day be used to harvest energy from ocean waves.

MODEC first exhibited a prototype of the SKWID system at the Wind Expo 2013 in Tokyo earlier this year, and plans to test it on both the land and the sea throughout the year.

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