Contra-rotating tidal turbine emerges in the east

Multi-disciplinary collaboration involving several Japanese companies and organizations has resulted in the development of a contra-rotating propeller technology for tidal stream power generation.

The propeller technology has been developed to serve as an element technology for the next-generation of ocean energy power generation, according to New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Aside from NEDO, the contra-rotating turbine has been jointly developed by Kyowa Engineering Consultants, EIM Electric, Maeda Corporation, the Kyushu Institute of Technology, and Waseda University.

After developing the concept, the power generation performance and safety of the turbine were evaluated through a towing test conducted in October 2017 in the Nagasaki Bay.

Conducted on a 1:7 scale model of turbine, the tests confirmed turbine’s power generation efficiency of 43.1%, which exceeded the power generation estimate based on the design, according to NEDO.

“We installed a power plant at a depth of 3.5 m from the stern of the barge and towed it with a tug boat to simulate the current flow in the real sea area environment. As a result, we confirmed the stability of the rotation of the front and rear two-stage propeller and the high waterproof performance by the mechanical seal,” NEDO said.

Based on the results obtained through towing tests, NEDO said that the full-scale turbine with a rotor diameter of 7 meters could be expected to produce 543.6kW of power at a flow rate of 4 m/s.

This power generation technology is characterized by the adoption of a contra-rotating method, which generates power by using two rotors moving in opposite directions.

NEDO expects the technology to have higher power generation efficiency than a conventional one-stage propeller system, and lower size for the same amount of power generation.