TOKYO – Power-hungry, reliant on fossil fuels Japan has successfully tested a system that could provide a constant, consistent source of renewable energy regardless of wind or sun.
IHI Corp, a Japanese heavy machinery manufacturer, has been working on a subsea turbine that harnesses the energy in deep ocean currents and converts it into a steady and reliable source of electricity for more than a decade.
The massive machine resembles an aeroplane, but instead of jets, it has two counter-rotating turbine fans and a central ‘fuselage’ that houses a buoyancy adjustment system. The 330-ton prototype, known as Kairyu, is intended to be anchored to the sea floor at a depth of 30-50 metres (100-160 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 seabed cables.
“Ocean currents have an advantage in terms of their accessibility in Japan,” said Professor Ken Takagi, an expert on 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 Organisation (NEDO) estimates the Kuroshio Current could potentially generate as much as 200 gigawatts – about 60 per cent of Japan’s present generating capacity.
Like other nations, the lion’s share of investment in renewables has gone into wind and solar, especially after the Fukushima nuclear disaster curbed that nation’s appetite for atomic energy.
Japan Generator of Solar Power
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 50-70 per cent, compared with around 29 per cent for onshore wind and 15 per cent for solar.
In February, IHI completed a 3 ½ year-long demonstration study of the technology with Nedo.
Its team tested the system in the waters around the Tokara Islands in south-western Japan by hanging Kairyu from a vessel and sending power back to the ship. It first drove the ship to artificially generate a current, and then suspended the turbines in the Kuroshio.
The tests proved 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 (Otec), which exploits the difference in temperature between the surface and the deep ocean.
Mitsui OSK Lines Ltd has invested in UK-based Bombora Wave Power to explore the potential for the technology in Japan and Europe.
The company is also investing in Otec and began operating a 100 kW demonstration facility in Okinawa in April, according to Mr Yasuo Suzuki, general manager of the corporate marketing division. – Bloomberg
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