A deep-sea turbine could offer endless green power

A prototype deep-sea power generator uses ocean currents to generate unlimited renewable energy

Spotted: While the use of renewables is advancing in fits and starts, Japan has recently tested a system that could provide an almost unlimited stream of energy, without relying on the wind or sun. The system involves the use of a turbine placed on the ocean floor, where it can take advantage of stable deep-sea currents that flow steadily with little fluctuation in speed and direction. The ‘Kairyu’ turbine was built by Japanese heavy machinery manufacturer IHI Corporation, and has been in development for around 10 years.

In February of this year IHI successfully completed a three-and-a-half year long test in the waters of southwestern Japan. The huge Kairyu turbine somewhat resembles an aeroplane and includes two 36-foot-long counter-rotating turbine fans and a central housing unit containing a buoyancy adjustment system. By rotating in opposite directions, the two turbine blades cancel out rotary torques—the force that can cause an object to rotate about an axis—and act to maintain the generator’s stable position underwater.

The 330-tonne prototype is designed to be anchored to the seafloor at a depth of around 30-50 metres (100-160 feet). The generator includes a mechanism that changes the pitch angle of the turbine blades in accordance with the speed of the ocean current. This enables the system to generate energy as efficiently as possible. When maintenance is needed, operators can float the turbine to the surface of the water for easier access. The long-term plan is to site several of the turbines in the Kuroshio, one of the world’s most powerful ocean currents, and transmit the power via seabed cables.

IHI argues that the trial has opened the door for the wider use of deep-sea ocean currents to generate power. A company document states that “As an approach to the commercialisation of this technology, a floating type ocean current turbine capable of stably generating power is expected to serve as a low-cost energy source for remote islands, where… it is difficult to receive electric power from the main islands of Japan via power cables.”

While Kairyu is the first deep-sea turbine, there has been a surge of interest in the potential of the ocean for energy storage and generation. Springwise has seen a number of new ideas in this area, including a wave-powered desalination system and a design for an energy storage system placed on the ocean floor.