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NIPPONIA No.28 March 15, 2004

Special Feature*
Energy Harvested in Surprising Ways
The natural environment is a great source of renewable energy—and it is already being harvested. Science and technology are being applied to develop new energy resources, and to convert one form of energy into another. These pages document progress in Japan, from the development of new generating devices to innovations that will change lifestyles.
Written by Torikai Shin-ichi and Sanada Kuniko
Photos by Omori Hiroyuki and Kono Toshihiko
Other photo credits: Maritime Safety Agency; Bibai Natural Energy Research Association;
Xenesys Inc.; Kyushu Electric Power Co., Inc.; Ikeda Tomiki

Left: Illuminated buoy in the Akashi Strait, where tidal rips flow fast. The buoy is equipped with a tidal power generator that supplies several dozen watts.
Right: The Mizunokoshima lighthouse uses a combination of wave and solar power. The waves generate about 2,500 W, the sun about 4,400 W. For more info:

Ocean energy, to safeguard ocean transport
Wave and tidal power
Japan's Maritime Safety Agency has been researching and developing renewable energy since the early 1950s. Offshore sea routes need markers like lighthouses, radio beacons and illuminated buoys to guide maritime transportation. The markers are often placed on isolated islands and reefs, so an independent source of electricity is needed for each one.
There are approximately 5,500 sea route markers off the Japanese coast. At the present time, about 3,000 of them (54%) use renewable energy. The Agency plans to eventually increase this to around 80%.
In Japan, the biggest source of renewable energy is solar panels, which require little maintenance. The second most important source is wave turbines, which convert the vertical motion of ocean waves and swells into air pressure that turns electric turbine generators. The first wave turbine began operating in 1965, for an illuminated buoy in Osaka Bay. In 2002, the Agency installed a number of buoys illuminated by electricity from tidal-power turbines. The Agency thus uses ocean energy to ensure ocean safety.
The problem with these renewable energy systems is that the weather affects output. The Agency therefore uses a combination of solar and wave power to obtain a more stable supply of electricity. In the summer, the sun is strong and the ocean is calm, so most of the power comes from the sun. Wave energy is used mainly during the winter, when it is cloudy and the sea is rough.


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