Underwater turbine produces unlimited electricity at great depths

The Japanese company IHI Corp. has successfully tested its powerful underwater turbine that wants to benefit from the Kuroshio currents, one of the strongest on the planet, to supply electricity continuously and reliably to the country, after more than a decade of development.

The Japan New Energy and Industrial Technology Development Organization (NEDO) estimates that the Kuroshio Current, which flows along Japan’s east coast, could produce up to 60% of the country’s current capacity, roughly 200 gigawatts. Japan cannot rely on solar and wind energy as other nations try to do and looks to the sea as one of the most hopeful renewable sources.

“Ocean currents have an advantage in terms of accessibility in Japan,” Ken Takagi, a professor of ocean technology policy at the University of Tokyo told Iraic.info. “Wind power is more convenient geographically for Europe, which is exposed to prevailing westerly winds and is found at higher latitudes.

Prototype operation

IHI’s model is called Kairyu, and its design is similar to that of Orbital’s turbine in Scotland, the largest on the planet. Kairyu is also reminiscent of an airplane, although it is smaller. It is about 20 meters long by 20 meters wide and at the tip of its wings it carries two large propellers that rotate in opposite directions. This turbine weighs around 330 tons and is designed to work anchored to the sea floor between 30 and 50 meters deep.

In February, IHI and NEDO concluded a 3-year trial in the sea around the Tokara Islands in southwestern Japan. The turbine was connected to a ship and in the first phase of the tests, thanks to the drag effect, it artificially generated current. In the final phase, the ship left suspended within Kuroshio’s currents, which is how it should function normally.

In that period, the prototype achieved the goal that the company had set for itself, generating 100 kilowatts of stable power. Now, IHI is working to expand the system to 2 megawatts ahead of its commercial exit in the 2030s. The company told Iraic.info that it has also conducted an environmental impact study to understand how the system affects marine fauna and fishing in the area.

Steal the energy produced by the sea

One of the great drawbacks to market this turbine is the cost of energy production. IHI aims to generate power at 20 yen (0.14 euros) per kilowatt-hour from large-scale deployment. That figure is somewhat higher than the cost of wind and solar energy in the Japanese country.

Another obstacle will be installing it under the sea. According to Takagi, it is difficult to build a system robust enough to withstand ocean floor currents and lower maintenance costs. “Unlike Europe, which has a long history of oil exploration in the North Sea, Japan has little experience in offshore construction,” the researcher said.

Japan is also researching ocean thermal energy conversion (OTEC), a method that harnesses the difference in temperature between the ocean surface and bottom to produce energy. As Iraic.info points out, the transport company Mitsui OSK Lines has invested in the British company Bombora Wave Power to explore the potential of this technology in Japan and Europe. Yasuo Suzuki, the general manager of the corporate marketing division of Mitsui OSK Lines, says that a 100-kilowatt capacity demonstration facility of this technology started up in Okinawa in April. And this month the government has proposed changes to offshore wind auctions that could accelerate its OTEC development.

Takagi commented that “Japan has not been blessed with many alternative energy sources.” “People may say this is just a dream, but we have to try everything to achieve zero carbon emissions.”