Testing a giant turbine on the high seas offers hope for endless green energy
(Bloomberg) – Energy-hungry, fossil fuel-dependent Japan has successfully tested a system that could provide a constant, stable form of renewable energy, independent of wind or sun.
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For more than a decade, Japanese heavy machinery manufacturer IHI Corp. develops an underwater turbine that harnesses the energy of deep ocean currents and converts it into a stable and reliable source of electricity. The giant machine resembles an airplane, with two counter-rotating 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 seabed at a depth of 30 to 50 meters (100 to 160 feet).
In commercial production, the plan is to place the turbines in the Kuroshio Current, one of the strongest in the world, which runs along Japan’s east coast, and transmit the power via undersea cables.
“Ocean currents have an accessibility advantage in Japan,” said Ken Takagi, professor of ocean technology policy at the University of Tokyo’s Graduate School of Frontier Sciences. “Wind power is geographically more suited to Europe, which is exposed to predominantly westerly winds and located at higher latitudes.” The Japan New Energy and Industrial Technology Development Organization (NEDO) estimates that Kuroshio power could potentially generate up to 200 gigawatts, or about 60% of Japan’s current generation capacity.
Like other countries, the lion’s share of renewable energy investment has gone to wind and solar, especially after the Fukushima nuclear disaster dampened that country’s appetite for atomic power. Japan is already the world’s third-largest solar power producer and is investing heavily in offshore wind, but harnessing ocean currents could provide the reliable baseload power needed to reduce the need for energy storage or fuels. fossils.
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 system production frequency – of 50-70%, compared to about 29% for onshore wind and 15% for the solar.
In February, IHI completed a 3.5-year demonstration study of the technology with NEDO. His team tested the system in the waters around the Tokara Islands in southwestern Japan by hanging Kairyu from a ship and bouncing electricity back to the ship. He first led the ship to artificially generate a current, then suspended the Kuroshio’s turbines.
Tests proved the prototype could generate the expected 100 kilowatts of stable power and the company now plans to upgrade 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 to harness energy from the sea, including tidal and wave energy and ocean thermal energy conversion (OTEC), which harnesses the temperature difference between the surface and the deep ocean. Mitsui OSK Lines Ltd. invested in British company Bombora Wave Power to explore the technology’s potential in Japan and Europe. The company also promotes OTEC and began operating a 100 kW demonstration facility in Okinawa in April, according to Yasuo Suzuki, general manager of the company’s marketing division. Kyushu Electric’s renewable unit, Kyuden Mirai Energy, is starting a 650 million yen ($5.1 million) feasibility test this year to generate 1 MW of tidal power around the Goto Islands in the East China Sea. The government also this month proposed changes to offshore wind auctions that could speed up development.
Among marine energy technologies, the fastest moving towards profitability is tidal current, where “the technology has advanced quite a bit and is really working,” said Angus McCrone, former BloombergNEF editor and analyst at marine energy. Scotland-based Orbital Marine Power is one of many companies building tidal systems around Orkney, where the European Marine Energy Center is located. Others include SIMEC’s MeyGen network Atlantis Energy and California-based Aquantis, founded by US wind pioneer James Dehlsen, which plans to start testing a tidal system there next year.
Although tidal flows do not run 24 hours a day, they tend to be stronger than deep ocean currents. The Kuroshio Current flows at 1 to 1.5 meters per second, compared to 3 meters per second for some tidal systems. “The biggest issue for ocean current turbines is whether they could produce a device that economically generates power from currents that aren’t particularly strong,” McCrone said.
Ocean Energy Systems, an intergovernmental collaboration established by the International Energy Agency, sees the potential to deploy over 300 gigawatts of ocean energy globally by 2050.
But the potential for ocean energy depends on location, taking into account the strength of currents, access to networks or markets, maintenance costs, shipping, marine life and other factors. In Japan, wave energy is moderate and unstable throughout the year, while areas with strong tidal currents tend to have heavy ship traffic, Takagi said. And OTEC is better suited to tropical regions where the temperature gradient is greater. One benefit of the deep ocean current is that it does not limit ship navigation, the IHI said.
Yet Japanese society still has a long way to go. Compared to terrestrial installations, it is much more complicated to install a system underwater. “Unlike Europe, which has a long history of oil exploration in the North Sea, Japan has little experience in offshore construction,” Takagi said. There are major engineering challenges to building a system robust enough to withstand the harsh conditions of a deep ocean current and to reduce maintenance costs.
“Japan is not blessed with many alternative energy sources,” he said. “People may say it’s just a dream, but we have to try everything to get to zero carbon.”
With the cost of wind and solar power and battery storage declining, IHI will also need to demonstrate that overall project costs for ocean current power are competitive. IHI aims to generate electricity at 20 yen per kilowatt hour from large-scale deployment. This compares to around 17 yen for solar in the country and around 12-16 yen for offshore wind. IHI also said it conducted an environmental assessment before launching the project and will use the test results to examine any impact on the marine environment and the fishing industry.
If successful on a large scale, deep ocean currents could play a vital role in providing basic green energy as part of the global effort to phase out fossil fuels. IHI’s work could help Japanese engineering play a leading role with government support, McCrone said.
IHI needs to make a compelling case that “Japan could benefit from being a technology leader in this area,” he said.
(Add Japan offshore wind changes to ninth paragraph)
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