Ocean currents are closer to providing power for Japan
Power-hungry, fossil-fuel dependent Japan has successfully tested a system that could provide a constant, steady form of renewable energy, regardless of the wind or the sun.
For more than a decade, IHI Corp., a Japanese maker of heavy machinery, has been developing a subsea turbine that harnesses the energy in deep ocean currents and converts it into a steady and reliable source of electricity. The giant machine resembles an airplane, with two counterrotating turbine fans in place of jets, and a central “fuselage” housing a buoyancy adjustment system. Called Kairyu, the 330-ton prototype is designed to be anchored to the sea floor at a depth of 100 to
160 feet.
In commercial production, the plan is to site the turbines in the Kuroshio Current, one of the world’s strongest, which runs along Japan’s eastern coast, and transmit the power via seafloor cables.
“Ocean currents have an advantage in terms of their accessibility in Japan,” said Ken Takagi, a professor of ocean technology policy at the University of Tokyo Graduate School of Frontier Sciences. “Wind power is more geographically suited to Europe, which is exposed to predominant westerly winds and is located at higher latitudes.”
Japan’s New Energy and Industrial Technology Development Organization (NEDO) estimates that the Kuroshio Current could potentially generate as much as 200 gigawatts — about 60 percent of Japan’s present generating capacity.
Like other nations, the lion’s share of Japan’s investment in renewables has gone into wind and solar, especially after the Fukushima nuclear disaster curbed that nation’s appetite for atomic energy. Japan is already the world’s third-largest generator of solar power and is investing heavily in offshore wind, but harnessing ocean currents could provide the reliable baseline power needed to reduce the need for energy storage or fossil fuels.
The advantage of ocean currents is their stability. They flow with little fluctuation in speed and direction, giving them a capacity factor — a measure of how often the system is generating — of 50 percent to 70 percent, compared with around 29 percent for onshore wind and 15 percent for solar.
In February, IHI completed a 3½-year demonstration study of the technology with NEDO. Its team tested the system in the waters around the Tokara Islands in southwestern Japan by hanging Kairyu from a vessel and sending power back to the ship. It first drove the ship to artificially generate a current, then suspended the turbines in the Kuroshio.
The tests proved that the prototype could generate the expected 100 kilowatts of stable power, and the company now plans to scale up to a full 2-megawatt system that could be in commercial operation in the 2030s or later.
Like other advanced maritime nations, Japan is exploring various ways of harnessing energy from the sea, including tidal and wave power and ocean thermal energy conversion, which exploits the difference in temperature between the surface and the deep ocean. Mitsui OSK Lines Ltd. has invested in U.K.based Bombora Wave Power to explore the potential for the technology in Japan and Europe. The company is also investing billions of yen in OTEC and began operating a 100-kilowat demonstration facility in Okinawa in April, according to Yasuo Suzuki, general manager of the corporate marketing division. Kyushu Electric’s renewable unit Kyuden Mirai Energy begins a 650 million yen, or $5.1 million, feasibility test this year to produce one megawatt of tidal power around the Goto Islands in the East China Sea.
Among marine energy technologies, the one advancing fastest toward cost effectiveness is tidal stream, where
“the technology has advanced quite a long way, and it definitely works,” said Angus McCrone, a former BloombergNEF chief editor and marine energy analyst. Scotlandbased Orbital Marine Power is one of several companies constructing tidal systems around Orkney, location of the European Marine Energy Centre. Others include SIMEC Atlantis Energy’s MeyGen array and California-based Aquantis, founded by U.S. wind pioneer James Dehlsen, which reportedly plans to start testing a tidal system there next year.