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Science

SKWID harnesses the power of both the wind and the tide

By Ben Coxworth
May 17, 2013
SKWID harnesses the power of both the wind and the tide
The SKWID system, which harnesses power from both the wind and the tide, is scheduled to be tested in Japan
The SKWID system, which harnesses power from both the wind and the tide, is scheduled to be tested in Japan
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The SKWID system, which harnesses power from both the wind and the tide, is scheduled to be tested in Japan
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The SKWID system, which harnesses power from both the wind and the tide, is scheduled to be tested in Japan
A diagram of the features of SKWID
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A diagram of the features of SKWID

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.

A diagram of the features of SKWID
A diagram of the features of SKWID

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.

Source: MODEC via CBS News

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ScienceRenewable EnergyWind PowerTidal PowerWind turbine
8 comments
Ben Coxworth
Ben Coxworth
Based out of Edmonton, Canada, Ben Coxworth has been writing for New Atlas since 2009 and is presently Managing Editor for North America. An experienced freelance writer, he previously obtained an English BA from the University of Saskatchewan, then spent over 20 years working in various markets as a television reporter, producer and news videographer. Ben is particularly interested in scientific innovation, human-powered transportation, and the marine environment.

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8 comments
Michael Crumpton
The harvesting of power from currents seems like a natural addition to offshore wind turbines.
Slowburn
Ok generators are expensive but unless they are driving the center portion of the generator one way and the outer portion in the other balancing the energy input through gears will be very difficult. (Forcing there to be friction joints in the conduction path unless they use a magnetic induction connection that is even less efficient.) However if they transmit the energy to the generator hydraulically the there is not a problem and you could use a hydraulic capacitor to smooth the energy input to the generator improving the quality of the current coming out. but this does not allow for giving the wind turbine the necessary little boost to get it started without additional components.
Vijay Kamat
Every sceptic is addicted to cheap fuel from oppression of big brother, the problems caused by population and pollution seem to be overseen and thrown to the wind out of car window.
I would like to state my view here. Let the big things be installed on a larger scale but at micro or local level efficiencies and micro generation be the buzzword. Every country has an economy to run, industries to grow and life to be enjoyed by its citizens.
Here is my calculation. I have a 29" CRT TV which consumes 130W of power. In our home we have four FTL tubes which consume on an average 40W of power. I have a PC which consumes 110W of power. A refrigerator wattage of which I have not seen. Three cell phones. If I can reduce my usage with new LED Panel TV, LED light with addition of solar pv power to the mix, I will reduce the load on the grid. If most of families in my community first then in the city later would take us of the grid.
Municipal corporation in my city, has street lights with Sodium or Mercury vapour. Slowly they are replacing them with LED. They in turn are becoming efficient, their efficiency over time will reduce our taxes. If they install solar panels, then after the initial investment recurring costs are nil. Excess power generated can be channelled through F-I-T. Power generated by big units can be directly sent to big consumers i.e. industries, commercial complexes, railways. etc
Gadgeteer
"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. "
I think you misunderstand. Vertical axis wind turbines are designed to rotate in one direction only. But the fact that the axis is vertical means that the wind direction is irrelevant. Seen from above, the turbine looks exactly the same in all directions.
It's unclear whether there's a gearbox for the Darrieus rotor since it's likely to rotate faster than the Savonius. At the very least, there should be some kind of clutch for both turbines. It's unwise to couple together two mismatched sources of power. You could end up wasting tidal power turning the wind turbine during times of still winds, or conversely, the tidal turbine could be a drag on the wind turbine during times of strong winds. Of course, the latter could be an advantage if it can act as an effective brake to slow down the wind turbine during high winds that would otherwise damage it.
StWils
I am not sure how much mechanical since there are gearing is needed longterm since there are several electronic ways to "shift" forces. Todays IGBT transistors can handle stunningly large amounts of charge instantly. At least one such design is being field tested by a Japanese company. This was reported in GIZMAG last year sometime.
Jim Sadler
We have rivers here with strong currents and we have decent wind speeds as well. We could use quite a few of these devices. The water turbines in particular might function well even if placed closely to each other. We might even be able to use under water turbines that were horizontal rather than vertical. Since we have areas with heavy currents a half mile wide we might be able to generate a lot of power from just one line of these stretched across the river.
Patrick McGean
Reduce the scale and increase the numbers to lessen the effect on the tides, energy in energy out, cavitations are felt down wind and down tide. Don't forget the physics when thinking big, small is what it is all about.
Slowburn
re; Vijay G. Kamat
So rationally considering the strengths and weaknesses of an alternative energy supply makes one addicted to addicted to cheap fuel. Interesting.