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Clean Power ocean energy tidal turbines

Published on December 28th, 2014 | by Tina Casey


Turbines Float Like Kites In New Ocean Energy Project

December 28th, 2014 by  

The well known Japanese company Toshiba and its perhaps not as well known co-patriate IHI have been tapped to pilot a new ocean energy project that will deploy a phalanx of underwater turbines that float like kites. The project demonstrates once again how legacy companies are transitioning to new clean tech. At a little less than 100 years old Toshiba is a baby compared to IHI, which traces its roots back to 1853.

We’ve been bringing up the point about legacy companies lately (here and here, for example), because it underscores just how out of step the fossil energy sector is. Energy is a fungible technology, too, right?

ocean energy tidal turbines

Ocean energy concept courtesy of Toshiba.

Tapping Ocean Energy In Japan

Ocean energy turbines have been trickling into the global marketplace and Japan has an ocean energy ace up its sleeve: the Kuroshio Current.

One of the two largest of the world’s seven major currents, the Kuroshio Current lies right off the coast of Japan. According to our friends over at the US Navy, the current travels at a speed of up to 3 miles per hour.

That might not sound particularly speedy, but it’s more than enough to power an underwater turbine. Another thing to consider is the predictability of the current, which varies little throughout the year.


Back in 2012, The Japan Times also took note of how much control the country has over its maritime assets for ocean energy potential. Its offshore exclusive economic zone adds up to 4.47 million square kilometers, making it the sixth-largest in the world.

Floating Kite-Like Underwater Turbines

The new ocean energy project comes under the auspices of NEDO, Japan’s New Energy and Industrial Technology Development Organization.

This is actually the latest step in a NEDO-funded project that began back in 2011, involving Toshiba and IHI with the University of Tokyo and Mitsui Global Strategic Studies Institute in ocean energy research.

IHI has been leveraging its generations-long experience in energy and marine engineering to manufacture the device, which consists of two counter-rotating turbines that nest in a floating box. The box is anchored to the sea floor and floats, kite-like, at a strategic point in the current.

Similarly, Toshiba’s contribution to the project represents its expertise on the electricity generating side.

There doesn’t seem to be a timeline for deploying the device but for now we’ll guess it will be up and running by 2017, when the project is expected to wrap.

Ocean Energy In The USA

Here in the US, ocean energy strategy has been focusing on mainly on waves rather than currents. Among other projects we’ve been following the aptly named Ocean Power Technologies company, which has been working with the US Navy to deploy a wave energy harvesting device.

The Navy has also recently upgraded its wave energy test site in Hawaii. Last time we checked in, a deal was in the works to test run another device called StingRAY, engineered by the company  Columbia Power Technologies.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • JamesWimberley

    A better link on the Kuroshio – 1 on the map (link).

    The tethered design may be forced by the greater depth of the sea off Japan than in other tidal resources. This will push up costs, along with the low speed. On the other hand, the resource is enormous, and 24-hour as it’s an ocean gyratory current not a tide.

    Japan actually has good options for sustainable backup to wind and solar, the cheap variable renewables. It has very large legacy pumped storage, ironically built as backup for nuclear, and untapped geothermal, blocked by NIMBYism. Tidal stream adds another.

  • Martin

    I have looked at some of those quoted references, but some of those are for wind turbines, what I was thinking, using propellers that are used on large ships and submarines, low cavitation and very low speed.
    I have looked in the past at new propeller designs, for large ships, that are more efficient than all current types used.

  • Martin

    About industrial projects in the ocean, are oil drilling rigs not industrial projects?
    And we have seen what happens if there is a problem, with drill rigs, if a tidal turbine or something similar breaks, there would be a lot less damage!

  • borehead

    More junk in the ocean pantry. No industrial energy projects should be allowed. Tidal power? check!

    • Bob_Wallace

      Right. Let’s not put anything visible into the oceans.

      Let’s keep on pumping in the CO2. Yeah. That’s the answer…

      • borehead

        I was able to crack into your profile! I see you’ve received the a-hole of the day award multiple times! Congrats. You win again!

        • Bob_Wallace

          That’s one.

          We play a two strikes rule here.

          • borehead

            Well, you just play with yourself. Over ‘n out!

    • Matt

      Boat that move fast and have high speed props, damage wild life. These turn slow and don’t move around. Wake up, before posting please.

    • Larmion

      And why should industrial projects not be allowed in the ocean? They’re allowed on land, where their impact on biodiversity is often much greater.

      Sure, the industry (like all others) has to be properly regulated. But ‘X could potentially harm Y’ is never a good argument against X – it’s just an argument for strict regulation of X.

    • JamesWimberley

      One of the greatest threats to marine life is uncontrolled fishing. Offshore energy plants, whether under or above water, are incompatible with trawling because of the seabed power cables, and largely so with seine and line fishing. They become de facto marine conservation zones, after the one-off disruption from construction. This benefit can be enhanced with designing seabed structures as artificial reefs.

  • Marcus Kornmehl

    What stops marine life getting chopped into gefilte fish?

    • Bob_Wallace

      The blades don’t spin fast.

      When the first tidal turbine was installed it was only run during daylight hours and when biologists could be in the water to access damage to sea life. They cut the test period short because nothing was getting hit. Fish easily swam around the blades.

    • Larmion

      The same thing that stops you from being chopped up into tiny pieces next time you leave home: senses.

      Fish, primitive though they are, have a very decent talent for avoiding obstacles. And observation at existing Gorlov turbines shows most also swim fast enough to escape alive if they were to happen to be caught up in/near a turbine.

    • rtfazeberdee

      whats wrong with ready made but fresh sushi?

  • Martin

    Which one is more efficient underwater, a ship propeller type or a windmill type?

    • Different purposes, so they take different forms.

    • Larmion

      ‘Ship propellors’ aren’t a common design for turbines.

      Out of all realistic designs, the ‘windmill type’ (a horizontal axis turbine) is the most efficient, and the two-bladed design shown in the picture even more so than a three-bladed design (but they are subjected to greater stress).

      That being said, the largest and best performing tidal stream turbines currently used are Gorlov turbines. Though less efficient, they are simple, sturdy and reliable. Alstom is getting good results with their large-ish (1,4MW) horizontal axis turbines though, so Gorlov’s reign might be over soon.

    • Omega Centauri

      Ship propellers design has to be concerned with the phenomena called cavitation. This is the creation of water vapor bubbles in areas of locally low pressure. Because ships are generally travelling much faster than harvestable currents, and the propellers are close to the surface, and a lot of thrust is required from a limited diameter this is a much much more severe constraint than for these turbines, which are deep under water in a slow current. It shouldn’t be a surprise that optimal propeller designs look different.

      Wind turbines went to three blades to reduce the variable torque that results from the fact that the height above the ground (and hence wind speed) varies a lot every rotation. I doubt that would be much of a factor here.

    • globi

      I already answered your question some time ago: link.
      (‘Propeller-like-turbines’ are being used in run-of-the-river applications).

      And 3 blades are actually slightly more efficient than 2 blades because of the lower rpm (= the spinning speed of the blades is reduced = less drag).

      However, this additional blade is not delivering enough efficiency-gain to justify the extra material. The reason why 2 blades are rarely used in wind-turbine applications is because of uneven loads during yawing operations, higher cycling stresses (when ever one blade receives the most load the other blade receives the least load and vice versa) and noise.

      • Larmion

        The lower weight of a two-bladed design also makes a downwind configuration easier. That means eliminating the cost of a yawing mechanism and potentially more lightweight blades as flex is less of a problem (no danger of the blades hitting the turbine).

        A two bladed rotor can also be pre-assembled and stacked on deck of a ship (it’s flat), unlike three-bladed designs that have to be assembled at sea, where conditions are more challenging and more expensive equipment is required. That could sharply reduce the installation time (and thus cost) of offshore wind farms.

        Chinese and Japanese companies like MingYang and Hitachi are experimenting with large (5MW and more) two-bladed downwind designs, especially for offshore applications.

        For an industry currently held back only by high costs, this sort of penny-pinching innovation is more than welcome.

  • I like it! There is lots of torque in moving water.

  • David in Bushwick

    Thank you, Tina!

  • Larmion

    Wait. In what universe can Toshiba be described as a ‘legacy company’? If Toshiba is a legacy company, a business like Tesla is positively prehistorical.

    It’s a leading player in semiconductors and optics, medical technology (think MRI scanners), advanced materials, environmental technology, defense electronics and such like. And yes, it is a leader in energy too: it does groundbreaking research in superconductors, fuel cells and advanced nuclear and thermal technology.

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