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.