Renewable energy development remains focused on wind and solar power, with geothermal energy achieving marginal results from leading countries such as Iceland and New Zealand, though various forms of marine energy are still at the theoretical stage. Japan, as an island country, has been engaged in marine energy, despite its trailing progress in wind, PV, and geothermal energy. Ishikawajima-Harima Heavy Industries (IHI) has been studying power generation through ocean current energy, and now completed the field testing for its prototype.
（Source：IHI）
Marine energy primarily consists of wave energy, tidal energy, and ocean current energy. The coast of Japan is hit with the Oyashio Current and the Kuroshio Current from the north and the south, which form the North Pacific Current at the eastern sea area of Japan. IHI believes that an excellent utilization of the Kuroshio Current in power generation would be able to development 205GW of power capacity, where Japan generated 270GW of total power throughout 2021, making ocean current energy a significantly promising source for Japan.
IHI joined hands with the New Energy and Industrial Technology Development Organization (NEDO) of the Ministry of Economy, Trade, and Industry (METI) for R&D that had taken several decades. The two managed to complete the prototype, weighing 330 tons, and named as Kairyu, back in 2017
The body of Kairyu is formed with three large cylinders, each measuring at 20m in length, where the middle cylinder has a buoyancy adjustment device and an electrical connection device that is connected to the substation and distribution cables. A long tube is situated on each of the left and right lower sides at also 20m, and there are fan blades measuring at a diameter of 11m at the front of the left and right cylinders. The blades rotate in opposite directions, where the offset torque stabilizes the body of the equipment, with left and right cylinders each configured with power generations, as well as control and sensing devices.
Towed in the sea with anchor cables and power cables, Kairyu floats at a depth of roughly 50m, and offsets the force exerted by the current on the blades through buoyancy, which also offers the source of drag force for the blades. The device locates deep water current with the most efficient power generation by automatically adjusting its location, before transmitting the generated power to the grid. Kairyu is able to generate 100kWh of power at a water velocity of 2-4.
The field test of Kairyu was officially concluded in February 2022 after a duration of 3.5 years at the southwestern coast of Japan, and the next step is to invest in prototypes that are even larger, with blades extending to a diameter of 20m and power capacity enlarging to 2 million watts.
The 100kWh capacity of Kairyu’s prototype is exceedingly small compared to that of a single offshore wind turbine at as high as 14 million watts, and even the 2 million watt capacity after expansion would still be nothing in comparison. With that being said, a successful development in Kairyu has the potential to provide 40-70% of total power consumption for Japan, and the fact that ocean current is a self-sufficient energy would be a major contribution to Japan’s energy security.
(Cover photo source: pixabay)