Combining a three-bladed Darrieus turbine on top, a Savonius turbine underneath, and a generator in between, the SKWID power generation concept is claimed to be the world's first hybrid system "capable of maximizing the harvesting of ocean energy from wind and current".
The SKWID, from the Japanese company Mitsui Ocean Development & Engineering Company (MODEC), is designed to capitalize on the energy potential available both in the winds above the ocean, and in the currents flowing beneath the waves. The device uses an omnidirectional Darrieus wind turbine sitting 47 meters above the sea on one end of a vertical shaft, with a different type of omnidirectional turbine design, a 15 meter diameter Savonius, spinning at the other end under the surface.
The Darrieus wind turbine efficiently harnesses the ocean wind: The omnidirectional Darrieus turbine rotates regardless of the wind direction. Due to the location of the generator, the system has excellent stability with a low center of gravity, as well as excellent maintainability with easy access. The Darrieus’ rectangular swept area catches twice as much wind when compared to the circular swept area of typical onshore wind turbines of the same diameter and is therefore capable of delivering twice as much power from a single installation - far more power from the same wind farm area
The Savonius current turbine harnesses the current: The split-cylinder-shaped buckets of the Savonius current turbine can harness any weak current and will rotate in one direction regardless of current direction. This turbine is insensitive to marine growth on the buckets and is harmless to the marine ecosystem, as it rotates slowly at the speed of the current. - MODEC
The floating unit is said to be stable and self-righting, thanks to a gimbal-like support structure that isolates the generator unit from the motion of the waves, as well as the underwater turbine acting as a ballast or keel. According to CBS News, a prototype SKWID unit will be deployed off the coast of Japan this fall.