By Kaname Yoneyama / Yomiuri Shimbun PhotographerTests are under way in various parts of Japan to generate electricity through the power of waves, wind, differences in water temperature and other oceanic sources of natural energy.
About 30 meters off a breakwater in Kuji, Iwate Prefecture, a huge metal plate — 4 meters wide and 2 meters tall — is suspended beneath a generator on a platform above the water. The plate can be seen swinging back and forth in the water, in sync with the motion of the waves. This is Japan’s first wave power plant, which was approved by the central government in November last year.
Its maximum output is 43 kilowatts, enough to supply the daily needs of about 10 households. The power generated here is currently used for refrigerators and other appliances at a nearby fishing port. The plant was set up by the University of Tokyo’s Institute of Industrial Science, which has been working on creating next-generation energy in areas afflicted by the 2011 Great East Japan Earthquake. The institute is planning to set up an improved power generator with a larger output off Hiratsuka, Kanagawa Prefecture, in 2020.
Wind power is used in the floating offshore wind turbine project, a task jointly promoted by industry, government and academia. Three huge wind turbines of different generating power rotate about 20 kilometers off Naraha, Fukushima Prefecture. Nothing blocks the wind on the sea, efficiently exposing the turbines to plenty of wind. To ready the system for commercial use, factors such as its cost and its impact on the environment and fisheries are now being assessed.
The Deep Sea Water Ocean Thermal Energy Conversion Demonstration Facility in Kumejima, Okinawa Prefecture, takes advantage of the temperature difference between deep-sea water and surface water. Warm surface water at an annual average of 26 C is used to evaporate volatile fluids such as ammonia. The expanding volume of the vapor creates pressure that rotates a turbine generator. Then, 8 C to 9 C water that has been pumped up from a depth of 612 meters cools the vapor and turns it back into fluid. This system can generate 50 kilowatts of electricity.
Studies of various methods of generating power are being promoted across the country. Okinawa Institute of Science and Technology Graduate University Prof. Tsumoru Shintake, 61, has developed a small, low-cost power generator using tidal or wave power to rotate turbine blades. “The ocean has great potential to create various types of energy,” Shintake said.