SKWID harnesses the power of both the wind and the tide
By Ben Coxworth
May 17, 2013
There are already a wide variety of renewable energy systems that harness the power of the wind, along with some that generate power via the flow of ocean currents. According to Japanese engineering firm MODEC (Mitsui Ocean Development & Engineering Co.), however, its soon-to-be-tested SKWID system will be the first one to do both.
SKWID stands for Savonius Keel and Wind Turbine Darrieus. This is appropriate, as it’s an anchored floating platform that contains both a Savonius tidal turbine below the waterline, and a Darrieus vertical-axis wind turbine up in the air. The two are connected by a central gearbox/generator, allowing the SKWID to generate power from the currents, the wind, or both. Additionally, the rotation of the tidal turbine can be used to help get the wind turbine spinning, when breezes are light and it needs a bit of extra inertia.
The design of the Darrieus turbine is such that it can spin to the left or to the right, so it works regardless of the wind direction. The tidal turbine spins in just one direction, but it does so irrespective of the direction of the current. It is reportedly able to harness even the weakest of currents, and is not affected by marine growth on its half-cyclinder-shaped buckets/blades. Additionally, because it spins no faster than the current, it is claimed to be safe for marine life.
The SKWID shouldn’t be too likely to tip over in rough seas, as the deck-level-mounted generator and below-deck-mounted tidal turbine help keep its center of gravity low. Additionally, the ring-shaped deck (which is the source of flotation) is joined to the central structure via flexible rubber mounts, allowing it to rock back and forth with the waves while the turbines and associated machinery remain stable and upright.
According to a report on Japan’s NHK News (relayed by America’s CBS News), one of the SKWIDs is due to be installed and tested off the coast of Japan, sometime this fall (Northern Hemisphere). The wind turbine should sit 47 meters (154 feet) above sea level, with the tidal turbine having a diameter of 15 meters (49 feet). Together, they may be able to generate enough power to provide for approximately 300 households.