www.yomiuri.co.jp
September 16, 2010
A project under way in the Seto Inland Sea aims to generate huge amounts of electricity from the energy of water currents, using streamlined turbines shaped like a tuna. Kiyomi Suzuki, president of the Hyogo Prefecture firm Nova Energy Co., sailed around the world in his former career as a ship captain and is taking a hands-on approach to leading the project. "Whenever I saw a tanker in the Persian Gulf. I had a sense of crisis about Japan's reliance on imported energy", Suzuki said.
The principle of tidal power generation is the same as that of hydroelectric power generation: Moving water rotates turbines that are connected to an electricity generator. Tidal power electricity generation projects pursued by other countries, such as Britain and South Korea, have been troubled by frequent occurrences of debris, such as driftwood and fishing nets, jamming or breaking turbine propellers. Suzuki realised the problem was due to the fixed position of the turbines--if they were able to move freely and follow changes in the direction of the current, debris would wash past the turbines, rather than becoming lodged in their propellers. "There are many obstacles in the sea", Suzuki said. "But the correct design can effectively deal with them".
Under Nova Energy's design, turbines are connected to electricity generators by a system of rotating axle joints. This enables a turbine to move on both vertical and horizontal axes, so that its body is always in line with the flow of the current. The design is ideal for the Seto Inland Sea, where the currents of up to 20 kph do not run in a uniform direction, because of the many small Islands within its waters. Ocean currents, on the other hand, have a continuous, unidirectional flow. The design, which is expected to have no negative impact on the marine ecosystem, may be included in plans for marine power plants being drawn up by the Economy. Trade and Industry Ministry.
Suzuki established Nova Energy in 2007, nine years after he quit his job as captain of a cargo vessel, to put his ideas for improved turbines into action. He conducted extensive tests of different designs in a water tank and in 2008, using 1.2-meter-long propellers made of light but strong reinforced plastic, he succeeded in generating electricity at a rate of 200 watts. The rotating-axle system proved to be a success--the turbines changed position to follow changes in the current, and were untroubled by passing debris.
Research into hydrodynamics by Prof. Deog Hee Doh of Korea Maritime University, who studied at the University of Tokyo, provided Suzuki's efforts with a great boost. By applying Deog's research, Suzuki found that power-generation efficiency increased by 30% by using turbines modeled on the distinctive, streamlined shape of tuna. The firm is currently experimenting with turbines equipped with six-meter-long propellers in the Akashi Strait in the Seto Inland Sea. The aim is to achieve a production capacity of more than 5kWs.
The Environment Ministry has commissioned the project to develop technology aimed at addressing global warming, and will provide 114 million yen in subsidies. Nova Energy plans to build a turbine with a 14-meter-long propeller by the end of this fiscal year, with a view to eventually developing a 25-meter-long model. The company has also set a goal of building a power station in the open sea, using large-propeller turbines to capture the energy of ocean currents, which it believes could be an attractive alternative to nuclear power. "We'll be able to build a large electric power plant with generation capacity of 1.6 millionkWs, the equivalent of a large nuclear power station, for half the cost of building a nuclear power plant", Suzuki predicted.
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