The energy of waves to Japan's coasts is estimated to be at about 35 million kW, which is the one-third of the total electric power generated in Japan. Many attempts to exploit wave energy have been made from old times. After the first oil crisis research and development projects of wave power converters have been made in the world and various converters were developed including a wave power extracting caisson breakwater. However no system has been employed as a practical power plant due to cost of the system and irregularity of the electric output. Recently the challenges started again to develop the converters as a consequence of recent high oil price. Innovations are needed for the technologies of wave power converters and the social systems to utilize the wave energy.
